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UBC Theses and Dissertations

Analysis of human early fetal facial growth and jaw relationships McFadden, Megan


Objectives: Abnormal jaw relationships can be a warning sign of the presence of congenital anomalies. During the late fetal period the jaw relationship is hypothesized to be stable allowing for detection of abnormal jaw position. This study aims to analyze growth of the jaws in 2D and 3D during the early fetal period in normal human conceptuses. Methods: Lateral and frontal radiographs were available from a collection of 197 fetal specimens aged 10-20 weeks gestation, of these 26 specimens were scanned with micro-CT. Exclusion criteria was applied and a total of 14 linear and 5 angular measurements were made on digitized radiographs and micro-CT volume renderings. Linear regression models were used to analyze the relationship between the data collected and age in days of the specimens. Results: Images comprising this study included 141 frontal radiographs, 120 lateral radiographs and 25 micro-CT scans. All linear measurements of the maxilla and mandible show a significantly positive association with increasing age in days. Age in days is a statistically significant (P<0.001) predictor of the size of the maxilla and mandible in all three planes of space. Both the maxilla and mandible increase more in width than length or height. Between 10-20 weeks, age in days is a significant (P<0.001) predictor of the jaw relationship. The radiographic data was divided into two groups, the jaw relationships during the 10-15 week period is significantly correlated with age (P<0.001). There is no correlation between jaw relationship and age during the 16-20 week period. From 10 to 15 weeks gestation the percent increase in size of all linear measurements is greater than during the 16-20 week period. Gender related growth rate differences are not observed. Conclusions: During the early fetal period the maxilla and mandible grow more in width than height or length. Age in days is a strong predictor of maxillary and mandibular size in all three planes of space. Both the maxillary projection and the maxillary position relative to the mandibular position increase with increasing age especially in the 10 to 15 week timespan. The mandibular projection does not change with increasing age.

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