Dentistry, Faculty of
DSpace
UBCV
AlTuwaijri, Sahr
Master of Science - MSc
University of British Columbia
Statement of problem: The use of digital impressions for implants are limited to single and short span bridges due to the few available studies supporting their usage in more complex cases. Therefore, its essential to evaluate their accuracy in full arch cases to benefit from their great advantages. Purpose: Evaluate and compare the accuracy of digital and conventional impressions for multiple straight and angulated implants of full arch implant supported fixed prosthesis. Also, assess the effect of implant angulation of 45° and increased length on the accuracy of both methods. Materials and methods: A stereolithographic (SLA) model of edentulous mandibular cast was fabricated and used to produce the master stone cast with four Nobel CC RC implants placed at tooth positions 3.4, 3.2, 4.2 and 4.4. Implants at #32 and 42 were perpendicular to the occlusal plane and parallel to each other while implants at #34 and 44 were distally angulated with 45°. Three impression methods were made from the master stone cast. Digital impressions were made with Trios (3Shape, Copenhagen, Denmark) intraoral scanner (IOS) (n=10). Conventional splinted open-tray implant–level impressions were made with Polyvinyl (PVS) (n=10) and Polyether (PE) (n=10). All stone casts were digitized using a 3shape D800 lab scanner to obtain STL (standard tessellation language) files, which then were imported into Rhino5 3D software. Six linear measurements were obtained for each cast to evaluate their discrepancies from the master cast. Absolute values of the linear deviation of each line among the three groups were compared using Kruskal-Wallis test and Dunn's post hoc test. Results: Significant difference (P< 0.05) were found between Trios and PVS and between PE and PVS for the distance between Implant #42 and 44. Also, for the distance between implant #32 and 44 between PE and Trios, and between PE and PVS. No significant difference was found for the other lines. Conclusion: The PE impression technique was more accurate than the others and all methods were considered clinically acceptable. The 45° degree of angulation and the increased length had affected the accuracy of PVS and Trios groups.
Multiple implants impression accuracy of edentulous jaw: digital and conventional implant impression comparative study by Sahr AlTuwaijri A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Craniofacial Science) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) August 2018 © Sahr AlTuwaijri, 2018 ii The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, a thesis/dissertation entitled: Multiple implants impression accuracy of edentulous jaw: digital and conventional implant impression comparative study Submitted by Sahr AlTuwaijri in partial fulfillment of the requirements for the degree of Master of Science in “Craniofacial Science” Examining Committee: Dr. Caroline Nguyen Supervisor Dr. Chris Wyatt Supervisory Committee Member Dr. Dorin Ruse Supervisory Committee Member Dr. Huge Kim Additional Examiner Additional Supervisory Committee Members: Dr. Vincent Lee Supervisory Committee Member iii Abstract Statement of problem: The use of digital impressions for implants are limited to single and short span bridges due to the few available studies supporting their usage in more complex cases. Therefore, its essential to evaluate their accuracy in full arch cases to benefit from their great advantages. Purpose: Evaluate and compare the accuracy of digital and conventional impressions for multiple straight and angulated implants of full arch implant supported fixed prosthesis. Also, assess the effect of implant angulation of 45 and increased length on the accuracy of both methods. Materials and methods: A stereolithographic (SLA) model of edentulous mandibular cast was fabricated and used to produce the master stone cast with four Nobel CC RC implants placed at tooth positions 3.4, 3.2, 4.2 and 4.4. Implants at #32 and 42 were perpendicular to the occlusal plane and parallel to each other while implants at #34 and 44 were distally angulated with 45. Three impression methods were made from the master stone cast. Digital impressions were made with Trios (3Shape, Copenhagen, Denmark) intraoral scanner (IOS) (n=10). Conventional splinted open-tray implant–level impressions were made with Polyvinyl (PVS) (n=10) and Polyether (PE) (n=10). All stone casts were digitized using a 3shape D800 lab scanner to obtain STL (standard tessellation language) files, which then were imported into Rhino5 3D software. Six linear measurements were obtained for each cast to evaluate their discrepancies from the master cast. Absolute values of the linear deviation of each line among the three groups were compared using Kruskal-Wallis test and Dunn's post hoc test. Results: Significant difference (P< 0.05) were found between Trios and PVS and between PE and PVS for the distance between Implant #42 and 44. Also, for the distance between implant #32 and iv 44 between PE and Trios, and between PE and PVS. No significant difference was found for the other lines. Conclusion: The PE impression technique was more accurate than the others and all methods were considered clinically acceptable. The 45 degree of angulation and the increased length had affected the accuracy of PVS and Trios groups. v Lay Summary People who have lost all their teeth search for solutions other than complete removable dentures. They are keen on having teeth that are fixed into their mouths. Complete dentures can be fixed to dental implants surgically placed in bone. The first step in fabricating complete fixed dentures is making an impression of the implants. Currently, new impression methods (digital scanning) have become widely available, and are introduced as a comparable alternative to the previous techniques (conventional Polyether and Polyvinyl impressions). In this study, a comparison was made between these methods to evaluate how accurate they are and what factors can influence their accuracy and their eventual usage. All tested methods found to be clinically acceptable, with polyether impression method being significantly better than the rest. The Trios digital scanning was affected by the inter-implants increased distance, while the conventional Polyvinyl method was influenced by the angulated position of the implants. vi Preface The research was designed by myself with the modification and supervision of the supervisor Dr. Caroline Nguyen and the committee member Dr. Chris Wyatt. The literature review was performed by myself. The master acrylic cast was fabricated by the lab technician at Paul Ro dental laboratory. The fabrication of the stone master cast (reference cast), all test groups of the study including; Group 1 (10 PE implant impression) / Group 2 (10 PVS implant impression) / Group 3 (10 Trios IOS implant impression) were done by myself in addition to the 20 stone casts of group 1 and 2. The conventional implant impressions (group 1 and 2) included the fabrication of the custom tray and the impression coping splinting. All stone casts; master cast and the 20 test casts were digitized by the same lab technician. The accuracy measurements with Rhino 3D software for all the digital casts were analyzed and performed by myself with the supervision of Dr. Alan Hannam. The statistical analysis was performed by the statistical department at UBC. vii Table of Contents Abstract ......................................................................................................................................... iii Lay Summary .................................................................................................................................v Preface ........................................................................................................................................... vi Table of Contents ........................................................................................................................ vii List of Tables ..................................................................................................................................x List of Figures ............................................................................................................................... xi List of Symbols ........................................................................................................................... xiii List of Abbreviations ................................................................................................................. xiv Glossary ........................................................................................................................................xv Acknowledgements .................................................................................................................... xvi Dedication .................................................................................................................................. xvii Chapter 1: Introduction ................................................................................................................1 1.1 Passive fit ............................................................................................................................ 2 1.1.1 Misfit: biological and mechanical complication ..................................................... 3 1.1.2 Load distribution differences between teeth and implants ..................................... 3 1.2 Determining passivity ......................................................................................................... 4 1.3 Conventional implants impression ...................................................................................... 5 1.3.1 Impression materials ............................................................................................... 5 1.3.2 Impression techniques ............................................................................................. 6 1.3.2.1 Open tray vs closed tray impressions.................................................................. 6 1.3.2.2 Splinting vs non-splinting ................................................................................... 6 viii 1.4 Modern fabrication methods in implant dentistry ............................................................... 8 1.5 Digital Intra-Oral Scanning (IOS) ...................................................................................... 8 1.5.1 Scan body ................................................................................................................ 9 1.5.1.1 Scan body accuracy related factors ................................................................... 10 1.5.2 Advantages of IOS ................................................................................................ 10 1.5.3 Challenges with IOS ............................................................................................. 11 1.5.4 Accuracy of IOS in complete implant supported prosthesis ................................. 12 1.5.5 Trios IOS accuracy ............................................................................................... 13 1.6 Patient preference.............................................................................................................. 16 1.7 Accuracy of lab scanner .................................................................................................... 16 1.8 Rhino 5 3D software ......................................................................................................... 16 1.9 Rationale ........................................................................................................................... 17 1.10 Research questions ............................................................................................................ 17 1.11 Null Hypotheses ................................................................................................................ 18 1.12 Specific aims ..................................................................................................................... 18 1.13 Significance....................................................................................................................... 18 Chapter 2: Materials and methods .............................................................................................19 2.1 Master cast fabrication ...................................................................................................... 19 2.2 Custom tray fabrication..................................................................................................... 22 2.3 Implant impression (test groups) (Figure 9) ..................................................................... 23 2.3.1 Group 1: Splinted implant level open-tray polyether impression ......................... 24 2.3.2 Group 2: Splinted implant level open-tray polyvinyl impression ......................... 25 2.3.3 Group 3: Digital Intra-Oral scanning (TRIOS) ..................................................... 27 ix 2.4 Digitizing the master cast.................................................................................................. 28 2.5 Accuracy measurement ..................................................................................................... 28 2.6 Statistical analysis ............................................................................................................. 33 2.6.1 Comparing the accuracy of implants impression between the three test groups. . 33 2.6.2 Comparing the implants position errors between the groups................................ 34 2.6.3 Intraclass Correlation ICC. ................................................................................... 34 Chapter 3: Results........................................................................................................................35 3.1 Effect of implant angulation: ............................................................................................ 35 3.2 Effect of increased distance (cross arch): ......................................................................... 36 3.3 Comparing the implants position errors between the groups: .......................................... 38 3.4 The intraclass correlation test ........................................................................................... 40 Chapter 4: Discussion ..................................................................................................................41 4.1 Limitations of the study .................................................................................................... 44 4.2 Strength of the study ......................................................................................................... 44 Chapter 5: Conclusion .................................................................................................................46 Bibliography .................................................................................................................................47 x List of Tables Table 1: Measurements and comparison of line deviation in micrometer for three methods....... 37 Table 2: Measurements and comparison of implants errors in micrometer for the three methods....................................................................................................................................................... 39 Table 3: The Intraclass Correlation test (ICC) results .................................................................. 40 xi List of Figures Figure 1: Scan body ........................................................................................................................ 9 Figure 2: Trios IOS ....................................................................................................................... 15 Figure 3: Digital design of the master cast in Co-diagnostic software ......................................... 19 Figure 4: Master cast digital design in Rhino 5 3D software ....................................................... 20 Figure 5: Master cast in clear acrylic ............................................................................................ 21 Figure 6: Master stone cast (control) ............................................................................................ 21 Figure 7: Impression coping ......................................................................................................... 22 Figure 8: Splinted implant level impression coping ..................................................................... 23 Figure 9: Methodology flow chart ................................................................................................ 23 Figure 10: Intaglio surface of PE Implant level impression ......................................................... 24 Figure 11: Group 1 (PE) stone cast ............................................................................................... 25 Figure 12: Intaglio surface of PVS implant level impression ....................................................... 26 Figure 13: Group 2 (PVS) stone cast ............................................................................................ 26 Figure 14: Trios Digital scan ........................................................................................................ 27 Figure 15: Plane through points .................................................................................................... 30 Figure 16: Plane parallel to CP ..................................................................................................... 30 Figure 17: Surface extension and offset by 2mm ......................................................................... 31 Figure 18: Mesh split by the offset surface ................................................................................... 31 Figure 19: Surface from curve and perpendicular line ................................................................. 32 Figure 20: Line split and formation of the implant surface centroid ............................................ 32 xii Figure 21: Six linear measurements in Rhino 5 ............................................................................ 33 Figure 22: Implants positions diagram ......................................................................................... 35 Figure 23: Linear deviation among the three groups .................................................................... 38 Figure 24: Comparison of implant errors among the groups ........................................................ 39 xiii List of Symbols : indicate the angle degree m: micrometer xiv List of Abbreviations CAD: “Computer assisted design” CAM: “Computer assisted manufacturing” IOS: Intra-Oral scanner PE: Polyether impression material PVS: Polyvinyl Siloxane impression material STL: Standard tessellation language SLA: Stereolithographic xv Glossary Dental Implant: “a prosthetic device made of alloplastic material(s) implanted into the oral tissues beneath the mucosal and/or periosteal layer and on or within the bone to provide retention and support for a fixed or removable dental prosthesis; a substance that is placed into and/or on the jaw bone to support a fixed or removable dental prosthesis” (GPT9). Digital scan: “in dentistry, capturing the optical image directly of the patient’s anatomy or indirectly of a definitive cast of the anatomy” (GPT9). Edentulous: “without teeth, lacking teeth” (GPT9). Implant-supported denture: “dental prosthesis, such as fixed complete denture, fixed partial denture, removable complete overdenture, removable partial overdenture, as well as maxillofacial prostheses, which can be supported and retained in part or whole by dental implants” (GPT9). Polyether: “an elastomeric impression material of ethylene oxide and tetra-hydrofluro copolymers that polymerizes under the influence of an aromatic ester” (GPT9). Poly (vinyl siloxane): “an addition reaction silicone elastomeric impression material of silicone polymers having terminal vinyl groups that cross-link with silanes on activation by a platinum or palladium salt catalyst” (GPT9). Removable complete denture: “a removable dental prosthesis that replaces the entire dentition and associated anatomy of the maxillae or mandible; the removable complete denture can be readily inserted and removed from the mouth by the patient; comp, COMPLETE DENTURE” (GPT9). xvi Acknowledgements I wish to express my great appreciation to my supervisor Dr. Caroline Nguyen and my Committee members Dr. Chris Wyatt, Dr. Dorin Ruse and Dr. Vincent Lee for their substantial support, guidance and precious time. Special thanks to Dr. Caroline Nguyen for her generosity and guidance providing a safe environment throughout the thesis journey. My dear committee members, this entire experience wouldn’t have been as good as it was without your great ideas and continuous encouragement. I would like to express my gratitude to Dr. Alan Hannam for his generous impact in teaching me how to use the Rhino 5 3D software for the accuracy analysis of the study. I really appreciate the valuable time, your patience and kindness. I would love to thank Mrs. Erikka Gilmore, the Territory representative of Nobel Biocare Canada, for her amazing personality, support and kindness as well as the Nobel Biocare company for their generosity in supporting the study through providing all the implant replicas, scan bodies and impression coping needed for the study. Finally, special thanks to my colleague Dr. Arwa Gazzaz for being a great friend who supported me throughout the process, giving me feedback and making this journey unforgettable. xvii Dedication Every great achievement requires endless personal effort, I would not be able to progress, bear the burdens required and succeed without the support of my loving family. I dedicate my humble work to my family, my beloved husband Eng. Emad Al Fouzan. Your presence, continuous emotional support, endless reassurances and valuable suggestions made this journey unforgettable. No words will be enough to describe my gratitude. I would love to dedicate my work to my great and amazing parents, my dad Eng. Homood Al Tuwaijri and my mom Joharah Al Tuwaijri; my life wouldn’t have been as good without you. You were the role models that every child wants to have; your endless love, support and encouragements made me who I am. I really cannot explain my gratitude to you. I would like to express my special thanks to my parents-in-law Ahmed Al Fouzan and Munerah Al Essa, your infinite support and prayers were such a motivation for me to keep going. Finally, my brother and sisters: thank you so much for being in my life. You were always there whenever I felt weak or lost, thank you for being my source of strength and wisdom. 1 Chapter 1: Introduction Historically, people who lost their entire teeth will replace them with complete removable denture. In 1950-1960s Professor Branemark and colleagues developed and introduced the titanium endosseous dental implant (Albrektsson, Brånemark and Zarb). After that, dental implants were accepted as a treatment modality and has become widely used in dentistry. Nowadays, with the dentistry evolution, implant prosthetic rehabilitation is the preferred treatment option for replacing missing teeth. People are increasingly aware of all the available possible treatments and seek the best. Several studies have proven the long-term success of implant treatments (Buser et al.). Restoring function and esthetics are essential components in prosthodontic treatment planning. There are different types of Implant supported dentures, whether it is removable or fixed and whether it is complete or partial. For people who are completely edentulous and seek a treatment that is fixed and feels like natural teeth, the treatment of choice will be the full arch implant supported fixed prosthesis. Patients that will benefit the most from such a treatment are those who are young, people who suffer from xerostomia or gag reflex. This treatment modality consists from either a metal framework with veneered acrylic resin, a zirconia framework with layered ceramic or a full counter monolithic zirconia framework. To fabricate this prosthesis, several steps are involved: 1- Prosthetically driven implant planning according to the ideal tooth position in the arch 2- Implants surgical placement in the desired locations using surgical guide 3- Implant impression to fabricate the master cast 2 4- Jaw relation record including; centric relation and vertical dimension of occlusion 5- Teeth try in to assess the esthetic, phonetics and the previous jaw records 6- Framework design and fabrication 7- Framework intra-oral try in 8- Framework/teeth try in, 9- And finally processing and insertion of the implant supported prosthesis. All these fabrication steps should be done meticulously and precisely to ensure longevity and avoid any future complications. An accurate fit of the implant supported prosthesis is one of the main success factors of implant treatments. Prostheses misfits can lead to several mechanical complications including; screw loosening, prosthesis fracture, or even more advanced complications like implant fracture or failure (Papaspyridakos, Lal, et al.; Duyck and Naert). Half of the misfits are caused by the impression procedures, while the other half are due to the prosthesis casting and fabrication process (Heckmann et al.). 1.1 Passive fit Branemark determined “passive fit” in 1983, when he suggested that it should not exceed 10 μm to permit bone remodeling under occlusal forces (Branemark). A few years later in 1985, Klineberg and Murray recommended that discrepancies higher than 30 μm over more than 10% of the circumference of the abutment interface were unacceptable (Klineberg and Murray). Jemt has defined “passive fit” as the fit that will not cause any type of long term clinical complication. It 3 was suggested that an unacceptable level of framework misfit happened when more than half-a-turn was required to completely tighten the gold screw after its initial seating resistance was faced (Jemt). To have passive fit, the prosthetic superstructure should have zero strain over the underlying implant when it is unloaded (Sahin and Cehreli). An implant-supported fixed prosthesis with discrepancies or misfit up to less than 150 μm is considered clinically acceptable (Jemt; Jemt and Lie; Jemt and Book) which was considered in the study as the clinically accepted discrepancy. 1.1.1 Misfit: biological and mechanical complication In a study done by Carr et al., they found that the bone biologic reaction for different misfit levels, ranging between 38 μm and 345 μm, was similar, with no signs of bone resorption over the period of the study in unloaded implants (Carr, Gerard and Larsen). Similar findings were found in the retrospective study done by Kallus and Bessing who stated that 236 patients with misfitting implant-supported prostheses for a period of five years had no signs of osseointegration or marginal bone level loss, while misfit of the prosthetic superstructure was the cause of gold screw loosening (Kallus and Bessing). 1.1.2 Load distribution differences between teeth and implants Natural teeth demonstrate buccolingual movement ranging between 56 μm and 108 μm and intrusion of 28 μm under load, that is mainly related to the presence of the periodontal ligament (Shillingburg, Hobo and Whitsett), while implants are osseointegrated and completely encircled by bone, so the interface is stiffer and minimum movement is detected, which is attributed to the bone deformation under load around implants (Sahin and Cehreli). 4 1.2 Determining passivity The evaluation of the strains on each prosthetic implant component is the only in vivo technique to assess the actual amount of the prosthesis passivity. Such a process is definitely time consuming that demand the connection of strain gauges which also requires the use of complex and costly equipment. Therefore, it is considered unrealistic to use strain gauges as part of a regular clinical treatment protocol (Sahin and Cehreli). Kan et al. suggested numerous clinical assessment techniques to evaluate the misfit of the implant framework: 1- “Alternate finger pressure”, to evaluate the instability of the prosthetic superstructure and observe the misfit gap for any bubbling around. 2- Direct visualization and tactile sensation by using the explorer tip to confirm the marginal fit, which is restricted by the explorer tip dimension (a pristine explorer tip is approximately 60 m). 3- Radiographs, which have the disadvantages of possible overlap or superimposition, depending on different angulations. 4- “The Sheffield test” (“the one screw test”): tightening one screw at the end of one side of the framework and then discrepancies are detected at the other end screw. 5- “Screw resistance test”, where one starts with the midline nearest implant; the screws are then tightened one after the other one until the initial resistance is met at one of the screws. If the screw needs more than an extra half a turn to reach the optimal screw seating, the framework is considered mis-fitting. 6- Disclosing media, like “fit checker” (GC), “pressure indicating paste” (mizzy Keystone) or disclosing wax. 5 7- 3D photogrammetric test has been considered as a quantifying method that can assess discrepancies to the nearest 10 μm. Other 3D quantifying procedures, such as “coordinate measuring machine”, can only be utilized extra-orally (Kan et al.). 1.3 Conventional implants impression Several factors affect the accuracy of the impression and hence the accuracy of the implant cast, including the type of impression, implant position and angulation, the number of implants, the impression technique: whether to splint or not, open or close tray impressions and the use of stock tray or customized impression tray, and finally, the type of prostheses (Lee et al.). 1.3.1 Impression materials Multiple studies have been conducted to compare the accuracy of different impression materials, most of them evaluating the differences between polyether and polyvinyl impression materials as they are the most frequently used implant final impression materials (Lee et al.) . Most of these studies show no difference between these two materials. Daoudi MF et al. and Chang et al. both reported no difference between polyether and polyvinyl impression material with regards to their accuracy for single implant impression (Daoudi, Setchell and Searson; Chang et al.). Similar results were reported by Lorenzoni M et al. and Gökçen-Rohlig et al. where they found no significant difference in distortion between polyvinyl and polyether implant impressions (Lorenzoni et al.; Gokcen-Rohlig et al.). With regards to different implant angulation, S Reddy et al. found no difference in the accuracy of the two materials when the angle of the implants were 0°, 10°, and 15° (Reddy et al.). In contrast, Sorrentino et al. found a difference in accuracy, 6 with polyvinyl being more accurate in 5 angled implants and polyether in straight implants (Sorrentino et al.). Similarly to Sorrentino, Kurtulmus-Yilmaz et al. found a difference with polyvinyl being more accurate with the angled implants at 10 and 20 (Kurtulmus-Yilmaz et al.). 1.3.2 Impression techniques Several factors are related to the impression technique, including type of the tray, open vs closed tray impression and splinting vs non-splinting impression, as detailed below. 1.3.2.1 Open tray vs closed tray impressions Several studies were done evaluating the difference in accuracy between open tray and close tray impression techniques. One of these studies is the one conducted by Al Quran FA et al. where they reported that the direct (open tray) technique showed the lowest mean of distortion (Al Quran et al.). Similar results were found by Assif D et al. with the open tray technique being more accurate (Assif et al.). In contrast, Chang WG et al. reported no difference between the two techniques (Chang et al.). In a recent systematic review in 2014, it was reported that out of 21 studies, 11 of them preferred the open tray impression technique, 1 study supported the closed tray and the remaining 10 studies found no difference (Papaspyridakos, Chen, et al.) . 1.3.2.2 Splinting vs non-splinting Numerous studies have been done to detect the differences between splinting and non-splinting, and also examine different splinting materials and techniques. Several studies recommended 7 splinting over non-splinting (de Avila et al.; Pujari, Garg and Prithviraj) (Papaspyridakos, Hirayama, et al.; M. Stimmelmayr et al.). Papaspyridakos P et al. concluded that the splinting resulted in more accurate casts compared to the non-splinted impressions in the overall 3D measurements, which coincided with clinical assessment of the prosthesis, where the clinical fit of the CAD/CAM Zirconia full arch implant supported prostheses were acceptable in 11 casts out of 12 in the splinted group and 6 out 12 in the non-splinted group (Papaspyridakos, Benic, et al.). In addition, another study was conducted to compare the splinting with acrylic resin and metal drill bars, and non-splinting impression technique. Four parallel implant analogs were placed simulating the Branemark protocol. A metal framework was made to fit the master cast, with mean gap value of 39.64 μm, and used to check the amount of discrepancy between the two techniques. This study resulted in significant differences, where the splinted technique resulted in lesser gaps (99.19 μm) compared to the non-splinted technique with a mean gap value of (205.86 μm) (Avila et al.). When comparing splinting, with auto-polymerizing acrylic resin/light curing composite resin, and non-splinting technique, involving air abraded impressions coping with aluminum oxide of 50 μm under 75 lbs pressure in two different situations, straight and 65°of angulation, no difference was found with the straight implants, while the angulated implants showed statistically significant difference, being more accurate in splinted techniques compared to the non-splinted air-abraded impression post (Assuncao et al.). In addition, three different splinting materials (light polymerizing resin (Triad gel) and autopolymerizing resin (GC resin and Fixpeed resin)) were tested to evaluate their 3D accuracy for full arch implant cast verification jig. Triad gel had the lower 3D deviation compared to other two materials although the results were not statistically 8 significance (Papaspyridakos, Kim, et al.) which can be explained by the 0.20% linear shrinkage of Triad gel (Harvey and Harvey) and the 0.80% of GC resin (Mojon et al.) . 1.4 Modern fabrication methods in implant dentistry The CAD/CAM technology provided better fit and improved accuracy when compared to the conventional casting procedures for implant-supported cobalt-chromium and zirconia fixed prostheses (de França et al.). Discrepancies of less than 40 μm were obtained using CAD/CAM for implant-supported short and long FPD prosthesis (Katsoulis et al.). 1.5 Digital Intra-Oral Scanning (IOS) Digital IOS was introduced in the 1980’s by Professor Mormann and Dr. Brandistini. It is considered the first step towards a full digital work flow, which is the data acquisition. Cerec 1 (Redcam) was the first 3D intra-oral camera, introduced in 1985 (Mormann, Brandestini and Lutz). Several available IOS are available on the market, such as Cerec Bluecam, Omnicom (Sirona), I Tero (Cadent Inc), True definition (3M), Lava COS (3M ESPE), Trios (3Shape), CS 3500 (Carestream) and PlanScan (Planmeca). Each IOS has its own working principle such as, active triangulation for the CEREC system, CS 3500 and PlanScan while Parallel conofocal technology for I Tero, Active wavefront sampling for True definition and Lava C.O.S and Confocal laser technology for Trios. Each one has its advantages, and disadvantages, with different levels of 9 accuracy and specific indications (Zimmermann et al.). Nowadays, IOS are widely available and are known for having a wide range of accuracy, similar or comparable to conventional impressions in tooth-borne fixed prostheses (Ender and Mehl; Luthardt, Loos and Quaas; Patzelt et al.). 1.5.1 Scan body The scan abutments are used to capture the position, trajectory, and rotation of the lab analogs in the working cast. Using dental scanners, the scan abutments are registered optically and the digital information is used to produce individual abutments and crown and bridge frameworks using innovative CAD/CAM technology (Figure 1). Figure 1: Scan body 10 1.5.1.1 Scan body accuracy related factors The implant scan body accuracy is affected by several factors including: the design of the scan body, material, type of scanner and the repositioning. 1- Accuracy of geometric representations of implant scan bodies: algorithm is a sufficient means to obtain surface data of the scan bodies. 2- Accuracy of scanning implant scan bodies: The accuracy of an extra-oral scanner varied between the scan design and the distances between the scan bodies. 3- Accuracy of positioning the implant scan body in the implant analogs: The precision of scanning was not significantly affected by removing and repositioning of the scan body (Fluegge et al.) . 4- Scanning stone casts has less errors in contrast to polymer casts when using lab scanners (white- light scanners) for the scanning of scan bodies. 5- The repositioning of the scan body is better on implant analogs compared to original implants with original implants having less reproducible fit of scan bodies (Michael Stimmelmayr et al.). 1.5.2 Advantages of IOS IOS has several advantages over the conventional impression technique that affect the efficiency and accuracy of the procedure as well as the patient experience. 1. Improved patient acceptance (Joda and Brägger; Schepke et al.). 2. Reduced distortion of conventional impression materials. 3. Potential cost and time effectiveness. 11 4. Elimination of all laboratory procedures. 5. A full digital work flow with the CAD/CAM technology (Christensen) . 6. More efficiency in relation to the total working time. 7. Allows for additional re-scans without repeating the entire procedure. 8. Less difficult to learn by unexperienced participants (Lee and Gallucci) . 1.5.3 Challenges with IOS The accuracy of IOS in implant dentistry can be affected by multiple factors that require proper case selection; • Possible scan bodies fit discrepancies on implants compared to implant analogs (Michael Stimmelmayr et al.). • The lack of landmarks or reference points in scanning implants in edentulous jaw (Andriessen et al.). • The scanned implants inter-distance length influence on the accuracy of scanner (Gimenez, Ozcan, et al.; Flugge, Att, et al.) • The geometrical shape of the scan body can affect the precision of the intra-oral scans (Fluegge et al.) 12 • The intra-oral conditions such as saliva and limited mouth opening decrease the accuracy of intra-oral scanning (Flugge, Schlager, et al.). • The position of the camera when moving from the first quadrant to the second one affect the distance accuracy (Gimenez, Ozcan, et al.) . • The operator experience, inexperienced operators showed higher accuracy with less variations compared to the experienced operators (Gimenez, Ozcan, et al.). 1.5.4 Accuracy of IOS in complete implant supported prosthesis Several studies have recently conducted evaluations of the accuracy of IOS. Moreno et al and Gherlone et al. have evaluated the Lava COS (3M ESPE) IOS, which resulted in clinically accurate implant supported prosthesis (Moreno et al.; E. F. Gherlone et al.), which is in contrast with Andiersson et al study, where they used I Tero IOS and found it less accurate with a mean of distance errors of 226 m and stated that it can’t be use to fabricate the prosthesis (Andriessen et al.). Gimenez et al tested the accuracy of several IOS (I Tero (Cadent Inc), Lava COS (3M ESPE), CEREC Blue cam (Sirona), 3D progress and ZFX(MHT)) for 6 implants placed in an edentulous maxilla and found that different depth of the implants and angulation didn't influence the accuracy of the scan and only the length of the scanned section had adversely affected the accuracy of CEREC with a mean distance deviation of -116m and SD of 103m. Also, generated a large number of errors with 3D progress and ZFX with mean distance deviation of 382.2m and -13 170.1m.(Gimenez, Ozcan, et al.; Giménez et al.; Gimenez, Pradies, et al.; Gimenez, Ozcan, et al.). Another in-vitro study by Mangano et al. in 2016 to evaluate the accuracy of four different IOSs (Trios, CS3500, ZFX Intascan and Planscan) in both partially and completely edentulous maxillary arch casts. No difference in accuracy was found between partially and completely edentulous casts scanning, while the different scanners had significantly different levels of accuracy, with Trios (71.6m) and CS3500 (63.2m) being the most accurate (Mangano et al.). In another study comparing the accuracy of single-unit dental implants and complete arch frameworks on implants in regard to the impression making and framework fabrication. They compared the digital scanning using I Tero and fabrication (CAD/CAM) of a single unit implant crown to a conventional impression made of polyvinyl material and conventional cast fabrication method, as well as for complete arch frameworks. They found that for the complete arch framework the digital method provided a more accurate implant supported framework prosthesis with 63.14m, while the conventional method was more accurate for the implant single framework (Abdel-Azim et al.) . 1.5.5 Trios IOS accuracy Trios (3Shape; Copenhagen, Denmark) is a IOS that Utilize Confocal microscopy working principle that recognize variations of focus plane positions. It takes multiple colored images and doesn’t require surface coating (Figure 2). Also, it’s an open system that allows scans to be exported as STL files or propriety files (Ting-shu and Jian). The accuracy of four different IOS 14 (Trios, 3M true definition, Omnicam and Lava COS) were compared using a highly accurate laboratory scanner as a control, when placing 6 relatively parallel implants in an edentulous mandible. The Trios and 3M true definition scanners showed the best accuracy while the Lava COS scanner showed the least accurate scanning and found to be not suitable to be used in a complete edentulous jaw with accuracy of 0.112 mm. (Vandeweghe et al.). In a clinical comparative study conducted by Gherlone and colleagues, they had 25 patients with clinical conditions that were recommended for “All-On-Four” prostheses (fixed implant supported prostheses on four implants) with a total of 30 conditions between mandible and maxilla suitable for implanted supported prostheses. For the test group, digital IOS with Trios from 3Shape (confocal microscopy) were used to fabricate 15 implant supported prostheses. For the control group, 15 conventional impressions (polyether pick-up impressions) were made. 30 CAD/CAM milled prosthetic frameworks were made and the final prostheses were seated on the implants and the fit of the prostheses was checked using the Sheffield test. The total time and the number of re-takes were counted to check the efficacy of both procedures. Intra-oral digital radiographs were taken immediately after placement and after 3, 6 and 12 months follow ups to evaluate the amount of bone loss. All the definitive prostheses were clinically accurate. No significant difference was found between the groups with regards to the amount of bone loss for the straight and tilted implants. The digital group was significantly more efficient, according to the total time needed, although the retakes there were more in the digital compared to the conventional impressions (E. Gherlone et al.) . 15 Different conventional implant impressions (implant level impression splinted/non-splinted and abutment level impression splinted/ non-splinted) were compared for five implants placed in an edentulous mandible with digital impression using 3Shape Trios IOS. The study concluded that there was no significant difference between conventional and digital impressions, with the digital impression being as accurate as conventional impression even with 15° implant angulation (Papaspyridakos, Gallucci, et al.). Figure 2: Trios IOS 16 1.6 Patient preference Two in-vivo studies were done evaluating patients’ preference and acceptance between digital and conventional single implant impressions. Both concluded that digital IOS was preferred by the participants and that it was more time effective (Joda and Brägger; Schepke et al.). Similar results were found by another study done by Wismeijer et al. evaluating patients’ preference between analog conventional implant impression, using polyether impression material, and digital implant impressions, using I Tero IOS. They conducted a questionnaire with seven different questions for both types, including general opinion, preparation needed, time involved, taste, intra-oral bite registration, size of impression tray and gag reflex. The thirty patients involved in the study preferred the digital IOS for all the factors except the time duration, which significantly favored the analog conventional implant impression (Wismeijer et al.) 1.7 Accuracy of lab scanner 3Shape D800 has 2 cameras with 5.0 MP that utilize light technology with red laser with 8 μm accuracy for implant supported bars and bridges. It takes up to 25 secs to finish a scan. W Renne and colleagues, concluded that the trueness of the full arch scan of the 3Shape D800 was the best among all other scanners (Renne et al.). The accuracy of the lab scanner D800 is not affected by the location or extent of the scan (Su and Sun) 1.8 Rhino 5 3D software Rhino 5 three-dimensional software can generate, edit, evaluate, document, render, animate, and translate 3D geometry that define any shape from a simple 2D line. In addition, you can import 17 any design or 3D object scan as STL files and utilize the software features such as analyzing distances, angles, radiuses and lengths. It has been used in dentistry mostly as a CAD software, 3D designing for Rapid prototype for experimental (Porojan, Topală and Porojan) or educational goals (Soares et al.) 1.9 Rationale As the demand for full arch implant supported is increasing, utilizing the most efficient methods available is highly recommended. IOS with all their advantages can provide both the patient and the clinician pleasant experiences with short appointments, reduced costs and treatment time. IOS are well known for their accuracy in implant supported single and short span fixed prostheses. There are very few studies supporting their use in full arch prostheses where the cross arch accuracy is important as well as with extremely angulated implants that are commonly used to avoid bone grafting and reduce the cost of such a treatment by utilizing fewer implants. 1.10 Research questions In the development of the research project two research questions were formulated. Firstly, we would like to know if Trios IOS digital impressions of multiple straight implants more accurate than conventional PVS/PE impressions? Secondly, are Trios IOS digital impressions more accurate than conventional PVS/PE impressions for angulated implants? 18 1.11 Null Hypotheses H01: No significant difference in the accuracy of implant impressions between Trios IOS and conventional PVS and PE impression techniques for multiple implants in edentulous jaw. H02: No significant difference in the accuracy of implant impression between Trios IOS and conventional PVS and PE impression techniques for angulated implants in edentulous jaw. 1.12 Specific aims 1- To measure the accuracy of conventional vinyl polysiloxane impressions for multiple (straight and angulated) implants in an edentulous mandible. 2- To measure the accuracy of conventional polyether impression for multiple (straight and angulated) implants in an edentulous mandible. 3- To measure the accuracy of intra-oral digital scanning (TRIOS 3SHAPE) for multiple (straight and angulated) implants in an edentulous mandible. 4- To compare the accuracy of conventional and digital impression method in angulated implants. 1.13 Significance Precise and accurate passive fit of implants prostheses depends on accurate implants impressions. If digital impressions are more accurate than conventional methods, this would provide patients with a treatment option leading to better long-term success, and efficient treatment. In addition, digital impressions are very convenient and well-tolerated methods, especially for patients with gag reflex and for geriatric patients. 19 Chapter 2: Materials and methods 2.1 Master cast fabrication To stimulate a clinical scenario, a stone cast of a patient’s edentulous mandible was used to fabricate the master acrylic cast. The cast was scanned with 3Shape D800 lab scanner. Implants were planned according to the (All-on-Four) design at the locations of teeth number 3.4, 3.2, 4.2, 4.4. Implants at 3.2 and4.2 were placed perpendicular to the horizontal plane. Subsequently, implants at 3.4 and 4.4 were distally angled by 45 , relative to the 3.2 and 4.2 implants, in Co-diagnostic software (Figure 3) and then designed on Rhino 5 3D (Figure 4). Figure 3: Digital design of the master cast in Co-diagnostic software 20 Figure 4: Master cast digital design in Rhino 5 3D software The cast was then fabricated on a desktop Stereolithography (SLA) 3D printer with clear acrylic resin using Nobel CC RP implants (Figure 5). Because the acrylic master cast cannot be digitized as the light will go through the cast surface and cause distortion, a stone cast was fabricated through conventional splinted open tray polyether impression, the impression was then poured with type IV die stone (silky rock, Whipmix, Louisville, USA) after connecting the implants analogs to the impression posts (Figure 6). 21 Figure 5: Master cast in clear acrylic Figure 6: Master stone cast (control) 22 2.2 Custom tray fabrication A two-millimeter wax spacer was used on the master stone cast that will allow uniform proper amount of impression material, and a light cured acrylic resin Triad sheet was used to fabricate the custom tray 2 mm away from the depth of the sulcus. The custom tray was cured for 2 minutes in (Enterra VLC curing unit, DENTSPLY). Custom tray has been used with all the conventional implant impressions. All impression copings (Figure 7) were splinted with light cured acrylic resin (Triad Gel; Dentsply, York, USA) which is urethane-dimethacrylate resin (UDMA), sectioned and then re-luted to reduce any polymerization shrinkage that might happened (Figure 8). Figure 7: Impression coping 23 Figure 8: Splinted implant level impression coping 2.3 Implant impression (test groups) (Figure 9) Figure 9: Methodology flow chart Group1 (PE)Digitized to have 10 digital castsGroup2 (PVS)Digitized to have 10 digital castslinear measurment compared to controlMaster castDigitized to have control digital castlinear measuremnt Group3 (Trios)10 digital castslinear measurment compared to control24 2.3.1 Group 1: Splinted implant level open-tray polyether impression First, the open tray non- engaging impression copings were connected to the implants of the master stone cast, then they were splinted using light cured acrylic resin (Triad Gel; Dentsply, York, USA) (Figure 8). Then, PE impression adhesive (3M ESPE; impregum) was applied on the custom tray intaglio surface. The adhesive was then allowed to dry for 15 minutes. Next, the impression was taken using polyether impression material (Impregum; 3M ESPE) (Figure 10). PE light body was applied around the implant impression coping while the heavy body was injected to fill the custom tray. The impressions were finally poured using type IV die stone (silky rock, Whipmix, Louisville, USA), after connecting the implants analogs to the impression copings. This entire procedure was then repeated 10 times, which resulted in 10 stone casts (Figure 11). Figure 10: Intaglio surface of PE Implant level impression 25 Figure 11: Group 1 (PE) stone cast 2.3.2 Group 2: Splinted implant level open-tray polyvinyl impression In this group, the open tray non- engaging impression copings were connected to the implants of the master stone cast, then they were splinted using light cured acrylic resin (Triad Gel; Dentsply, York, USA) (Figure 8). Then, PVS impression adhesive (Extrude; Kerr, Orang, USA) Afterwards, the impression was done using polyvinyl impression material (Extrude; Kerr, Orang, USA) (Figure 12). PVS light body was applied around the implant impression coping while the medium body was injected to fill the custom tray. The impressions were finally poured using type IV die stone (silky rock, Whipmix, Louisville, USA), after connecting the implants analogs to the impression copings. This procedure was then repeated 10 times, which resulted in 10 stone casts (Figure 13). 26 Figure 12: Intaglio surface of PVS implant level impression Figure 13: Group 2 (PVS) stone cast 27 2.3.3 Group 3: Digital Intra-Oral scanning (TRIOS) ELOS scan bodies (ELOS MedTech) with titanium insert and PEEK material were connected to the implants of the stone master cast. Then, the cast was scanned with IOS, utilizing confocal microscopy (TRIOS 3Shape) 10 times without removing the scan bodies, starting with quadrant 3 from occlusal, buccal and then lingual, with one continuous stroke of each surface. Then the virtual cast scan was checked and any deficiencies were rescanned. Finally, the scanned data were exported as STL (standard tessellation language) files (Figure 14). Figure 14: Trios Digital scan 28 2.4 Digitizing the master cast ELOS scan bodies were screwed in to the implants. The master stone cast was then scanned with the 3Shape D800 scanner, which worked as the reference (control) scan for the study. All stone casts fabricated from both conventional techniques, Group 1 and Group 2, were digitized with 3Shape D800 scanner as well using the same ELOS scan bodies. 2.5 Accuracy measurement 3D modeling and designing software (Rhino 5) was used to measure the accuracy of the implants impressions test groups. As far as this researcher knows, this is the first time that this software had been used to assess accuracy. Previous studies were mainly assessing the 3D deviation through superimposition of casts. In our study, each STL file from control cast, PE, PVS and Trios groups were named, numbered and imported into the software. The control scan was done first. The scan was displayed using prospective view from the software desktop, and shaded view of the cast, to make it clearly visible. The scan bodies were identified as A, B, C and D. Scan body A corresponds to the 3.4 implant, B to the3.2 implant, C to the4.2 implant and D to the 4.4 implant. The analysis started with scan body A for all the casts, followed by B, C and D following these steps: 1- A constructor plane with X, Y, Z coordinates at the horizontal top of the scan body was created, so the flat top of the scan body is considered the horizontal plane with X and Y axis’s for this implant. Vertices were selected from the flat top of the scan body; the target number of vertices was 10 with a minimum of 5 that were all located away from the borders. Then, the selected vertices were highlighted to construct a plane through command (plane through points) (Figure 15). 2- The plane was set parallel to the constructor plan (Figure 16). 29 3- The surface to cover the borders of the scan body was enlarged. The centroid of the surface was determined through the object propriety command and enlarged through scale 3D object up to 2. 4- The surface was offset to a parallel surface below by 2 cm (Figure 17). 5- The mesh was selected and split through the second offset surface (Figure 18). Then, hiding the upper part of the scan body, a (curve from object) command was selected along with the end curve of the split mesh. After that, the (construct a surface from curve) command was done. Then, centroid was identified for the surface and a perpendicular line was constructed (Figure 19). Finally, this line was split by the top surface to locate the point at the intersection of the line and the top surface as the point in which the measurement will be started (Figure 20). These steps were then done for each scan body of each cast. These points were used to obtain 6 measurements for each cast by constructing a line connecting each point together to create the following lines: AB, BC, CD, DA, AC and BD (Figure 21). All these measurements were done for every cast scan of the PE, PVS and IOS group to be compared with the control cast scan measurements for trueness and, within each group, for precision. The mean deviation of each measurement was obtained for the comparison between the groups, to evaluate the trueness. The linear deviation was used to compare the accuracy of three test groups between each other rather than comparing each group to the controls measurements. This was done by subtracting the control reading from each test reading for every line in each group. Test reading of line (AB) – Control reading of line (AB) After that, all the measurements were converted from millimeter to micrometer. 30 Figure 15: Plane through points Figure 16: Plane parallel to CP 31 Figure 17: Surface extension and offset by 2mm Figure 18: Mesh split by the offset surface 32 Figure 19: Surface from curve and perpendicular line Figure 20: Line split and formation of the implant surface centroid 33 Figure 21: Six linear measurements in Rhino 5 2.6 Statistical analysis 2.6.1 Comparing the accuracy of implants impression between the three test groups. Absolute values were used as the magnitude of deviation was the interest rather than the direction; otherwise, positive and negative results would reduce the total value and mislead the results to less deviation. Because of the small size of the sample, a non-parametric Kruskal-Wallis test was used on each pair of measurement deviations on same line to test if there was a significant difference among three methods for each line. If there was a significant difference, then Dunn's post-hoc test was used to detect which two measurement deviations had a significant difference in median. 34 2.6.2 Comparing the implants position errors between the groups. Kruskal-Wallis was used to test if there was any significant difference among the three methods for each implant. If there was a significant difference, then Dunn's post-hoc test was used to detect which two measurement errors had a significant difference on the median. 2.6.3 Intraclass Correlation ICC. The (ICC) was done to test the agreement and the reliability of each impression method with value range between 0-1. The procedure considered more accurate as it gets closer to 1. 35 Chapter 3: Results The comparison of linear deviation median for all the lines between the three groups are summarized in (Table 1). To evaluate the effect of implant angulation on the accuracy of the implant impression, four lines were used to assess any difference; these lines are the ones connecting implants from Quadrant 3 to Quadrant 4 (AB, CD, BD, AC). The other factor to evaluate was the cross arch (long span) effect on the accuracy. These lines were connecting one straight implant to angulated implant in the whole cast (DA, BC, AC, BD) (Figure 22). 3.1 Effect of implant angulation: 1- The median deviation for the PE group in AB line was 37 m, for CD line 52.5 m, for BD line 21.5 m and for AC line 46 m. 2- The median deviation for the PVS group in AB line was 44 m, for CD line 110. 5m, for BD line 79 m and for AC line 63 m. 3- The median deviation for the Digital (trios) group in AB line was 41 m, for CD line 50 m, for BD line 68.5 m and for AC line 53.5 m. A B C D Figure 22: Implants positions diagram 36 3.2 Effect of increased distance (cross arch): 1- The median deviation for the PE group in DA line was 45 m, for BC line 61.5 m, for AC line 46 m and for BD line 21.5 m. 2- The median deviation for the PVS group in DA line was 86.5 m, for BC line 30.5 m, for AC line 63 m and for BD line 79 m. 3- The median deviation for the Digital (trios) group in DA line was 132.5 m, for BC line 24 m, for AC line 53.5 m and for BD line 68.5 m. Significant differences in the deviations were found for the CD line between Trios and PVS and Between PE and PVS, with PVS having the highest deviation of 110.5 m. No difference was found between PE and Trios, with median values of 52.5 m and 50 m, respectively. Similarly, for the BD line there was significant differences between PE and Trios, and between PE and PVS, with PE having the least deviations of 21.5 m. There was no difference between PVS and Trios, with median deviation of 79 m and 68.5 m, respectively. So, the null hypotheses were rejected because of the significant difference found between Trios IOS with median of 68.5 m and PE group with median of 21.5 m in the (BD) linear measurement as its contribute to the null hypotheses. 37 Line PE PVS D P-value Post hoc test AB, Median (Range) 37 (0-117) 44 (2-97) 41 (2-102) 0.95 No significant difference in median CD, Median (Range) 52.5 (22175) 110.5 (47-243) 50 (11-76) 0.0013* D vs. PVS & PE vs. PVS AC, Median (Range) 46 (1-163) 63 (7-99) 53.5 (16-120) 0.99 No significant difference in median BD, Median (Range) 21.5 (2-74) 79 (22-173) 68.5 (10-100) 0.0079* PE vs. D & PE vs. PVS DA, Median (Range) 45 (2-133) 86.5 (13-721) 132.5 (25-434) 0.08 No significant difference in median BC, Median (Range) 61.5 (0-135) 30.5 (16-72) 24 (1-90) 0.249 No significant difference in median For post hoc comparison, the Kruskal-Wallis test is used with the Dunn’s test. Statistical significance is at p-value<0.05 Table 1: Measurements and comparison of line deviation in micrometer for three methods Box plot (Figure 23) was used to visualize the precision of each method. Variability in a data set is measured by interquartile range (IQR). The IQR is equal to (Q3- Q1). PVS group at DA line shows the wider variation compared to the other lines in the same group. DA line showed the higher variation among the lines for both PVS and Trios IOS groups. While AC line was the line with the wide variation in the PE group. 38 Figure 23: Linear deviation among the three groups 3.3 Comparing the implants position errors between the groups: The comparison of the implant position errors was carried out through the summation of three lines' absolute deviations that are related to each implant (Table 2). No significant difference was found for implant A and B between the three different implant impression groups. Implant C showed a significant difference between the groups, with the Trios digital group having less deviation compared to PE and PVS groups, whereas Implant D had a significant difference between PE and Trios as well between PE and PVS groups, with PE group having the least deviation (Figure 24). 39 Implant PE PVS D P-value Post hoc test A, Median (Range) 156.5 (18-304) 208.5 (54-917) 208.5 (72-656) 0.4973 No significant difference in median B, Median (Range) 138.5 (2-262) 183.5 (93-232) 117 (64-263) 0.4229 No significant difference in median C, Median (Range) 205.5 (60-300) 219 (136-354) 116.5 (90-285) 0.0331* D vs. PE & D vs. PVS D, Median (Range) 113 (83-247) 308.5 (129-988) 210.5 (102-580) 0.0045* PE vs. D & PE vs. PVS For post hoc comparison, the Kruskal-Wallis test is used with the Dunn’s test. Statistical significance is at p-value<0.05 Table 2: Measurements and comparison of implants errors in micrometer for the three methods Figure 24: Comparison of implant errors among the groups 40 3.4 The intraclass correlation test The average value for all the six-linear measurement of all the sample sizes of each group is displayed in (Table 3). PVS method has the higher ICC value followed by PE and lastly by Trios IOS. ICC Average value PE 0.74 PVS 0.88 Trios IOS 0.55 Table 3: The Intraclass Correlation test (ICC) results 41 Chapter 4: Discussion Implant impression accuracy is the first step in providing the patient with the best prosthesis with long term success through ensuring passive fit of the prosthesis. Digital implant impressions were introduced to the market as a new technique that can provide accurate impressions of fixed tooth borne prosthesis and small partial edentulous implant supported prosthesis. To our knowledge, few studies have assessed the accuracy of IOS for implant impressions of complete edentulous arches. Only two studies compared the accuracy of digital vs conventional implant impression (Papaspyridakos, Gallucci, et al.; Amin et al.). Before our study, no studies have been conducted to compare implant impression accuracy of full edentulous arch with angled implants up to 45. The (BD) line represents the distance between one straight and one angulated implant, located in quadrant 1 and quadrant 2, which describes the cross arch accuracy of IOS. Also, significant difference was found between the Trios IOS and PVS impression for (CD) line, where the Trios had better accuracy with median of 50 m while the PVS had a median of 110.5 m. This line represents the effect of the implant angulation of implant D with 45 distally. The comparison between the test groups and the control cast was conducted through digitizing the stone casts produced from both conventional techniques and the control cast to be compared with the digital casts, which is similar to several published papers (Amin et al.; Papaspyridakos, Gallucci, et al.; Güth et al.; Vecsei et al.). For accuracy measurement, Rhino 5 3D software was used. All STL files of all the test groups and the control cast were imported into the software. This is a new method to evaluate accuracy through 6 linear measurements between the four implants, where each line starts from the central long access of the implant. This technique helped in providing information regarding the effects of cross arch accuracy and the implant angulation. 42 The results of our study showed similarity in the accuracy of implant impression between digital and conventional methods, except for the two-linear measurements (BD and CD) mentioned above. In regard to the effect of implant angulation on the accuracy of the full arch implants impression, the current study had two distally angulated implants with 45 in the mandibular edentulous arch. The first angulated implant at #34 (A) related measurement (AB), (AC) and (DA) had no significant difference between the three groups which coincides with the study findings of Papaspyridakos et al. where the angulation of 10 and 15 didn’t affect the accuracy of the Trios 3 shape scanner when used for mandibular full arch implants impression (Papaspyridakos, Gallucci, et al.). Also, Gimenez et al.’s study on maxillary edentulous model with 6 implants and angulation up to 30 had similar results to our study with no effect of the implant angulation in the accuracy of implants impression using the LAVA C.O.S IOS (Giménez et al.). In addition, another study by Gimenez et al. utilizing the same previous study protocol with implant angulation of 30 but with iTero IOS had the same result with no significant difference on the implant impression accuracy in regard to the angulation (Gimenez, Ozcan, et al.). By assessing the accuracy of parallel 0 implants (B) and (C) and the distance between the implants (BC), no significant difference was found among the three groups with accurate measurements compared to the control. This finding is comparable with the Mangano et al. study which examined the accuracy of four IOS for partially and complete edentulous maxilla with six implants. No information was mentioned regarding the angulation of the implants which were most likely relatively parallel implants. The authors concluded in their study that CS3500 and Trios IOS were significantly more accurate than the other two IOS Zfx intra scan and Planscan which were not recommended to be used in the long 43 span prosthesis or multiple full arch implants (Mangano et al.). Additionally, Vandeweghe et al. conducted a study where they placed 6 relatively parallel implants in an edentulous mandible, and concluded that the Trios and 3M true definition IOS showed the best accuracy while LAVA C.O.S IOS was not recommended for cross arch prosthesis (Vandeweghe et al.). The other concern with the accuracy of multiple implants impression in edentulous jaw is the cross arch accuracy or the long span factor especially with the second quadrant accuracy. In our study, we found a significant difference between the groups for (BD) line which is crossing the midline with PE group having the least discrepancy compared to PVS and to Trios IOS with no significant difference between PVS and Trios IOS groups. This could be due to the long distance between the two implants as well as the position of implant (D) which is distally angulated implant with 45. Similar results were concluded by Gimenez et al. where they found that CEREC blue cam had high deviation in the second quadrant compared to the first scanned quadrant in maxillary cast with six implants placed with angulation ranged from 0 to 30 (Gimenez, Ozcan, et al.). The boxplot of figure 23 shows the variation of the linear discrepancy for every impression method that can describe the precision of each method and each line. The highest variation was found for the (DA) line for the PVS and the Trios IOS groups, although the differences were not statistically significant. This could be due to the long distance between implant (A) and (D) which caused the wide rang in the Trios values and that the cross arch factor should be taken into consideration. While the variability of the PVS group reading could be explained by the material physical properties which is more resilience compared to the PE rigidity. 44 Table 2 demonstrates the comparison of implants errors between the three methods. The results are in agreement with the linear discrepancy presented in table 1. Implant (C) and (D) had significant difference among the three groups with PVS having higher discrepancy in both implants which can be happened due to the impression removal technique of the conventional impression method which was started slightly with quadrant 4 followed by quadrant 3. This didn’t affect the PE due to the stiffer nature of the material. The ICC test was done to test the reliability of each method, the ICC range from 0-1 with reading closed to 1 considered more reliable and producible. The reading showing in table 3, demonstrates that PVS impression method has the highest reliability among the three groups while Trios IOS has the lowest. This means that PVS will provide a more constant impression, although it showed the highest deviation in (AD) but in general for all the lines of the whole sample of each group it was more constant. 4.1 Limitations of the study The project is an in-vitro study which is very different from the oral environment, where patient’s cooperation is paramount and there are isolation concerns. One IOS system was used, which limits generalizing the result of IOS accuracy due to the unique data acquisition of each IOS system. The method of the accuracy evaluation is new, which limits the comparison between the results obtained with those of other studies. Finally, the relatively small sample size used, even though similar to that of other studies, limits the generalization of the results. 4.2 Strength of the study Although this is an in-vitro study, the master cast used was obtained from a patient cast rather than a standard acrylic block to simulate a real clinical scenario. No markers or reference structures 45 were imbedded in the cast, to be similar to a patient edentulous arch. In addition, all the clinical steps for implant impression technique of the conventional impressions, as well as the sequence recommended for the IOS, were followed in the study to simulate a clinical situation as closely as possible. The study evaluated the accuracy of multiple implants with angulation up to 45 , which can provide estimation of the accuracy of any clinical case that has non- parallel implants or implants with different angulation, in addition to a recommendation to which technique can result in the least deviation. The study was done by one clinician (the MSc student) to ensure that the level of the experience was the same with both the IOS and the conventional PVS and PE impression techniques through all the samples. Also, one dental laboratory technician was responsible for the digitizing process of the control master cast and the two conventional test groups to eliminate any inter-operator errors. The accuracy analysis through the Rhino 5 3D software for all the digital casts was obtained by the MSc student for the same reason. 46 Chapter 5: Conclusion Using Rhino 5 3D software to obtain the linear measurements in order to compare the linear discrepancies between the three test groups reveals that Polyether implant impression of the edentulous jaw had the best accuracy compared to the other two groups. The PE group was significantly better than the PVS group in the CD line and significantly more accurate than the PVS and Trios digital groups in the BD line. Hence, PE impression is the superior in full edentulous multiple implants impression with angulated implants that is quite reproducible with 0.74 ICC value. PVS impression technique was affected by the implant angulation and Trios IOS was influenced by the increased distance between the implants that was shown in the wide variation of the DA line discrepancy of both groups. Although all the impression techniques resulted in discrepancies that are clinically accepted and ranged from 21.5-132.5 m, PE impression was significantly better among the test groups. PVS impression was the most reproducible method with ICC value of 0.88. In conclusion, all methods are clinically acceptable to use in multiple implants impression of full arch fixed prosthesis, with PE being recommended due to the better performance. PVS impression and IOS with Trios are very valid options as implant final impression of full arch implant supported fixed prosthesis, but the degree of angulation as well as the inter-implant distance need to be taken into consideration prior to the selection of these two methods. Finally, these recommendations should be taken with caution as they are based on in-vitro study that might differ from a real clinical situation. Further clinical studies comparing the accuracy of conventional and digital methods would be very beneficial and a natural extension of this project, in addition to testing different IOS systems that are available in the market. 47 Bibliography Abdel-Azim, T., et al. "The Influence of Digital Fabrication Options on the Accuracy of Dental Implant-Based Single Units and Complete-Arch Frameworks." INTERNATIONAL JOURNAL OF ORAL & MAXILLOFACIAL IMPLANTS 29.6 (2014): 1281-88. Print. Al Quran, F. A., et al. "Passive Fit and Accuracy of Three Dental Implant Impression Techniques." Quintessence Int 43.2 (2012): 119-25. Print. Albrektsson, Tomas, Per-Ingvar Brånemark, and George Albert Zarb. Tissue-Integrated Prostheses: Osseointegration in Clinical Dentistry. Quintessence, 1985. Print. Amin, Sarah, et al. "Digital Vs. Conventional Full-Arch Implant Impressions: A Comparative Study." Clinical Oral Implants Research 28.11 (2016): 1360-67. Print. Andriessen, Frank S., et al. "Applicability and Accuracy of an Intraoral Scanner for Scanning Multiple Implants in Edentulous Mandibles: A Pilot Study." The Journal of Prosthetic Dentistry 111.3 (2014): 186-94. Print. Assif, D., et al. "Comparative Accuracy of Implant Impression Procedures." Int J Periodontics Restorative Dent 12.2 (1992): 112-21. Print. Assuncao, W. G., et al. "Prosthetic Transfer Impression Accuracy Evaluation for Osseointegrated Implants." Implant Dentistry 17.3: 248-56. Print. Avila, Erica Dorigatti de, et al. "Effect of Splinting in Accuracy of Two Implant Impression Techniques." Journal of Oral Implantology 40.6 (2014): 633-39. Print. Branemark, Per-Ingvar. "Osseointegration and Its Experimental Background." The Journal of Prosthetic Dentistry 50.3 (1983): 399-410. Print. Buser, Daniel, et al. "10‐Year Survival and Success Rates of 511 Titanium Implants with a Sandblasted and Acid‐Etched Surface: A Retrospective Study in 303 Partially Edentulous Patients." Clinical Implant Dentistry and Related Research 14.6 (2012): 839-51. Print. Carr, Alan B., David A. Gerard, and Peter E. Larsen. "The Response of Bone in Primates around Unloaded Dental Implants Supporting Prostheses with Different Levels of Fit." The Journal of Prosthetic Dentistry 76.5 (1996): 500-09. Print. Chang, W. G., et al. "Accuracy of Three Implant Impression Techniques with Different Impression Materials and Stones." Int J Prosthodont 25.1 (2012): 44-7. Print. Christensen, Gordon J. "Impressions Are Changing: Deciding on Conventional, Digital or Digital Plus in-Office Milling." The Journal of the American Dental Association 140.10 (2009): 1301-04. Print. Daoudi, M. F., D. J. Setchell, and L. J. Searson. "A Laboratory Investigation of the Accuracy of Two Impression Techniques for Single-Tooth Implants." INTERNATIONAL JOURNAL OF PROSTHODONTICS 14.2 (2001): 152-58. Print. de Avila, E. D., et al. "Comparison of the Accuracy for Three Dental Impression Techniques and Index: An in Vitro Study." Journal of Prosthodontic Research 57.4: 268-74. Print. de França, Danilo Gonzaga B., et al. "Influence of Cad/Cam on the Fit Accuracy of Implant-Supported Zirconia and Cobalt-Chromium Fixed Dental Prostheses." The Journal of Prosthetic Dentistry 113.1 (2015): 22-28. Print. 48 Duyck, J., and I. Naert. "Influence of Prosthesis Fit and the Effect of a Luting System on the Prosthetic Connection Preload: An in Vitro Study." INTERNATIONAL JOURNAL OF PROSTHODONTICS 15.4 (2002): 389-96. Print. Ender, A., and A. Mehl. "Full Arch Scans: Conventional Versus Digital Impressions--an in-Vitro Study." International journal of computerized dentistry 14.1 (2011): 11. Print. Fluegge, Tabea, et al. "A Novel Method to Evaluate Precision of Optical Implant Impressions with Commercial Scan Bodies-an Experimental Approach: Precision of Optical Dental Implant Impressions." Journal of Prosthodontics (2015): n/a-n/a. Print. Flugge, T. V., et al. "Precision of Dental Implant Digitization Using Intraoral Scanners." Int J Prosthodont 29.3 (2016): 277-83. Print. Flugge, T. V., et al. "Precision of Intraoral Digital Dental Impressions with Itero and Extraoral Digitization with the Itero and a Model Scanner." AMERICAN JOURNAL OF ORTHODONTICS AND DENTOFACIAL ORTHOPEDICS 144.3 (2013): 471-78. Print. Gherlone, E., et al. "Conventional Versus Digital Impressions for "All-on-Four" Restorations." INTERNATIONAL JOURNAL OF ORAL & MAXILLOFACIAL IMPLANTS 31.2 (2016): 324-30. Print. Gherlone, E. F., et al. "Digital Impressions for Fabrication of Definitive "All-on-Four" Restorations." IMPLANT DENTISTRY 24.1 (2015): 125-29. Print. Gimenez, B., et al. Int J Oral Maxillofac Implants 29.4 (2014): 853-62. Print. ---. IMPLANT DENTISTRY 24.5 (2015): 498-504. Print. Gimenez, B., et al. "Accuracy of Two Digital Implant Impression Systems Based on Confocal Microscopy with Variations in Customized Software and Clinical Parameters." INTERNATIONAL JOURNAL OF ORAL & MAXILLOFACIAL IMPLANTS 30.1 (2015): 56-64. Print. Giménez, Beatriz, et al. "Accuracy of a Digital Impression System Based on Active Wavefront Sampling Technology for Implants Considering Operator Experience, Implant Angulation, and Depth." Clinical Implant Dentistry and Related Research 17 (2015): e54-e64. Print. Gokcen-Rohlig, B., et al. "Comparative Evaluation of the Effects of Implant Position, Impression Material, and Tray Type on Implant Impression Accuracy." Implant Dentistry 23.3: 283-8. Print. GPT9. "The Glossary of Prosthodontic Terms: Ninth Edition." J Prosthet Dent 117.5s (2017): e1-e105. Print. Güth, Jan-Frederik, et al. "Accuracy of Digital Models Obtained by Direct and Indirect Data Capturing." Clinical Oral Investigations 17.4 (2013): 1201-08. Print. Harvey, Wayne L., and Eric V. Harvey. "Dimensional Changes at the Posterior Border of Baseplates Made from a Visible Light-Activated Composite Resin." The Journal of Prosthetic Dentistry 62.2 (1989): 184-89. Print. Heckmann, Siegfried M., et al. "Cement Fixation and Screw Retention: Parameters of Passive Fit: An in Vitro Study of Three-Unit Implant-Supported Fixed Partial Dentures." Clinical Oral Implants Research 15.4 (2004): 466-73. Print. Jemt, T. "Failures and Complications in 391 Consecutively Inserted Fixed Prostheses Supported by Brånemark Implants in Edentulous Jaws: A Study of Treatment from the Time of Prosthesis Placement to the First Annual Checkup." The International journal of oral & maxillofacial implants 6.3 (1991): 270. Print. 49 Jemt, T., and K. Book. "Prosthesis Misfit and Marginal Bone Loss in Edentulous Implant Patients." The International journal of oral & maxillofacial implants 11.5 (1996): 620. Print. Jemt, T., and A. Lie. "Accuracy of Implant-Supported Prostheses in the Edentulous Jaw: Analysis of Precision of Fit between Cast Gold-Alloy Frameworks and Master Casts by Means of a Three-Dimensional Photogrammetric Technique." Clinical oral implants research 6.3 (1995): 172-80. Print. Joda, Tim, and Urs Brägger. "Patient-Centered Outcomes Comparing Digital and Conventional Implant Impression Procedures: A Randomized Crossover Trial." Clinical Oral Implants Research (2015): n/a-n/a. Print. Kallus, T., and C. Bessing. "Loose Gold Screws Frequently Occur in Full-Arch Fixed Prostheses Supported by Osseointegrated Implants after 5 Years." The International journal of oral & maxillofacial implants 9.2 (1994): 169. Print. Kan, Joseph Y. K., et al. "Clinical Methods for Evaluating Implant Framework Fit." The Journal of Prosthetic Dentistry 81.1 (1999): 7-13. Print. Katsoulis, Joannis, et al. "Cad/Cam Fabrication Accuracy of Long‐ Vs. Short‐Span Implant‐Supported Fdps." Clinical Oral Implants Research 26.3 (2015): 245-49. Print. Klineberg, I. J., and G. M. Murray. "Design of Superstructures for Osseointegrated Fixtures." Swedish dental journal. Supplement 28 (1985): 63. Print. Kurtulmus-Yilmaz, Sevcan, et al. "Digital Evaluation of the Accuracy of Impression Techniques and Materials in Angulated Implants." Journal of Dentistry 42.12 (2014): 1551-59. Print. Lee, H., et al. "The Accuracy of Implant Impressions: A Systematic Review." J Prosthet Dent 100.4 (2008): 285-91. Print. Lee, S. J., and G. O. Gallucci. "Digital Vs. Conventional Implant Impressions: Efficiency Outcomes." Clin Oral Implants Res 24.1 (2013): 111-5. Print. Lorenzoni, M., et al. "Comparison of the Transfer Precision of Three Different Impression Materials in Combination with Transfer Caps for the Frialit®-2 System." Journal of Oral Rehabilitation 27.7 (2000): 629-38. Print. Luthardt, R. G., R. Loos, and S. Quaas. "Accuracy of Intraoral Data Acquisition in Comparison to the Conventional Impression." International journal of computerized dentistry 8.4 (2005): 283. Print. Mangano, Francesco G., et al. "Trueness and Precision of Four Intraoral Scanners in Oral Implantology: A Comparative in Vitro Study." PLoS ONE 11.9 (2016): e0163107. Print. Mojon, Philippe, et al. "Polymerization Shrinkage of Index and Pattern Acrylic Resins." The Journal of Prosthetic Dentistry 64.6 (1990): 684-88. Print. Moreno, A., et al. "A Clinical Protocol for Intraoral Digital Impression of Screw-Retained Cad/Cam Framework on Multiple Implants Based on Wavefront Sampling Technology." IMPLANT DENTISTRY 22.4 (2013): 320-25. Print. Mormann, W. H., M. Brandestini, and F. Lutz. "[the Cerec System: Computer-Assisted Preparation of Direct Ceramic Inlays in 1 Setting]." Quintessenz 38.3 (1987): 457-70. Print. Papaspyridakos, P., et al. "Accuracy of Implant Casts Generated with Splinted and Non-Splinted Impression Techniques for Edentulous Patients: An Optical Scanning Study." Clinical Oral Implants Research 23.6: 676-81. Print. 50 Papaspyridakos, P., et al. "Accuracy of Implant Impressions for Partially and Completely Edentulous Patients: A Systematic Review." Int J Oral Maxillofac Implants 29.4 (2014): 836-45. Print. Papaspyridakos, P., et al. "Full-Arch Implant Fixed Prostheses: A Comparative Study on the Effect of Connection Type and Impression Technique on Accuracy of Fit." Clin Oral Implants Res (2015). Print. Papaspyridakos, P., et al. "Effect of Splinted and Nonsplinted Impression Techniques on the Accuracy of Fit of Fixed Implant Prostheses in Edentulous Patients: A Comparative Study." Int J Oral Maxillofac Implants 26.6 (2011): 1267-72. Print. Papaspyridakos, Panos, et al. "Digital Versus Conventional Implant Impressions for Edentulous Patients: Accuracy Outcomes." Clinical Oral Implants Research 27.4 (2016): 465-72. Print. Papaspyridakos, Panos, et al. "Digital Evaluation of Three Splinting Materials Used to Fabricate Verification Jigs for Full-Arch Implant Prostheses: A Comparative Study." Journal of Esthetic and Restorative Dentistry 29.2 (2016): 102-09. Print. Patzelt, Sebastian B. M., et al. "Accuracy of Full-Arch Scans Using Intraoral Scanners." Clinical Oral Investigations 18.6 (2014): 1687-94. Print. Porojan, LILIANA, FLORIN Topală, and SORIN Porojan. "Biomechanical Impact During Protrusion Loading on an Incisor Restored with a Ceramic Crown." Print. Pujari, Malesh, Pooja Garg, and D. R. Prithviraj. "Evaluation of Accuracy of Casts of Multiple Internal Connection Implant Prosthesis Obtained from Different Impression Materials and Techniques: An in Vitro Study." Journal of Oral Implantology 40.2 (2014): 137-45. Print. Reddy, S., et al. "Accuracy of Impressions with Different Impression Materials in Angulated Implants." Nigerian Journal of Clinical Practice 16.3: 279-84. Print. Renne, Walter, et al. "Evaluation of the Accuracy of 7 Digital Scanners: An In vitro Analysis Based on 3-Dimensional Comparisons." The Journal of Prosthetic Dentistry 118.1 (2017): 36-42. Print. Sahin, S., and M. C. Cehreli. "The Significance of Passive Framework Fit in Implant Prosthodontics: Current Status." Implant dentistry 10.2 (2001): 85-92. Print. Schepke, Ulf, et al. "Digital Versus Analog Complete-Arch Impressions for Single-Unit Premolar Implant Crowns: Operating Time and Patient Preference." Journal of Prosthetic Dentistry 114.3 (2015): 403-06. Print. Shillingburg, Herbert T, Sumiya Hobo, and Lowell D Whitsett. "Fundamentals of Fixed Prosthodontics, Quintessence Pub." Co, 2011. Print. Soares, Paulo Vinícius, et al. "Rapid Prototyping and 3d-Virtual Models for Operative Dentistry Education in Brazil." Journal of Dental Education 77.3 (2013): 358. Print. Sorrentino, R., et al. "Effect of Implant Angulation, Connection Length, and Impression Material on the Dimensional Accuracy of Implant Impressions: An in Vitro Comparative Study." Clin Implant Dent Relat Res 12 Suppl 1 (2010): e63-76. Print. Stimmelmayr, M., et al. "Clinical Study Evaluating the Discrepancy of Two Different Impression Techniques of Four Implants in an Edentulous Jaw." Clin Oral Investig 17.8 (2013): 1929-35. Print. Stimmelmayr, Michael, et al. "Digital Evaluation of the Reproducibility of Implant Scanbody Fit—an in Vitro Study." Clinical Oral Investigations 16.3 (2012): 851-56. Print. 51 Su, Ting-shu, and Jian Sun. "Comparison of Repeatability between Intraoral Digital Scanner and Extraoral Digital Scanner: An in-Vitro Study." Journal of Prosthodontic Research 59.4 (2015): 236-42. Print. Ting-shu, Su, and Sun Jian. "Intraoral Digital Impression Technique: A Review: Intraoral Digital Impression Review." Journal of Prosthodontics 24.4 (2015): 313-21. Print. Vandeweghe, S., et al. "Accuracy of Digital Impressions of Multiple Dental Implants: An in Vitro Study." Clin Oral Implants Res (2016). Print. Vecsei, Bálint, et al. "Comparison of the Accuracy of Direct and Indirect Three-Dimensional Digitizing Processes for Cad/Cam Systems – an in Vitro Study." Journal of Prosthodontic Research 61.2 (2017): 177-84. Print. Wismeijer, D., et al. "Patients' Preferences When Comparing Analogue Implant Impressions Using a Polyether Impression Material Versus Digital Impressions (Intraoral Scan) of Dental Implants." Clinical Oral Implants Research 25.10 (2014): 1113-18. Print. Zimmermann, M., et al. "Intraoral Scanning Systems - a Current Overview." International journal of computerized dentistry 18.2 (2015): 101. Print.
Thesis/Dissertation
eng
Craniofacial Science
Vancouver : University of British Columbia Library
Attribution-NonCommercial-NoDerivatives 4.0 International
Graduate
Multiple implants impression accuracy of edentulous jaw : digital and conventional implant impression comparative study
Text