Heritability of nasal characteristics using lateral cephalograms
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BACKGROUND: Growth of the cranial base and its structures are of particular interest to the orthodontic community. The midface and nasal bones have a significant influence on facial esthetics and thus pattern recognition of facial growth from parental data can influence orthodontic treatment plans. We aimed to determine if there is a similarity in midface and nasal bone and soft tissue growth between a child and either parent. MATERIALS AND METHODS: This cross-sectional study was comprised of forty-seven western European families from the Forsyth/Moorrees Twin Study. The lateral cephalograms of each parent and post pubertal child, who were at least 2 years past peak growth (age ≥ 16 yrs for females and ≥ 17 yrs for males) were evaluated on fourteen cephalometric variables. The radiographs were digitized and analyzed using the Mimics™ software program (Materialise, Leuven, Belgium) by a single investigator. A linear regression analysis was used to correlate linear and angular measurements to one another. An ANOVA with multiple comparisons (TUKEY) was performed to test for the differences between family members controlling for the effect of the individual family (as each family has a trend within itself). Age and gender interactions were tested for in the models. Statistical significance was set at p < 0.05. RESULTS: Twenty-five male and twenty-two female children and their parents were studied. When comparing the fourteen parameters between the mean of the child and both parents, a significant difference (p < 0.05) was found between the child and the father but not the mother in six measurements. These included the ratio of nasal height to total face height, angle of nasal bone to SN, distance from rhinion to pronasale (mm), distance from ANS to pronasale (mm), projection of nose (mm) and nasal length (mm). A significant difference was also found between the child and the mother, but not the father for rhinion to ANS (mm). A significant difference was found between the child and both parents for nasal height (mm). When controlling for family and isolating the gender of the child, males and females were not significantly different from their fathers for ratio of nasal height to total face height. For angle of nasal bone (S-N-Rh) and nasal length (N’-vertical line from Pro), females but not males were significantly different from the father. Both girls and boys were still significantly different from the father in the rhinion to pronasale and ANS to pronasale distances, projection of nose and nasal heights. Only males showed a significant difference from the mother for rhinion to ANS and nasal height when isolated for by gender. CONCLUSION: Statistically significant differences were found between the child and father and not the mother for six out of our fourteen measurements of interest. Two measurements of interest showed a difference between the child and the mother and not the father and one showed a significant difference from both parents. From this study we conclude that children tend to be morphologically less similar to their fathers when comparing midface and nasal soft and hard tissue parameters.