Craniofacial growth of untreated children: A longitudinal CBCT study

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MSOB (Master of Science in Oral Biology)
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Objectives: To conduct a longitudinal study of growth in untreated patients using CBCT. Materials and Methods: CBCT images were obtained for eleven male children (mean age 8.8 years at T1, 11.8 years at T2) and eighteen females (mean age 9.1 years at T1, 10.8 years at T2) and had been taken at least 1 year apart. A non-magnified 2D lateral cephalogram was derived from each CBCT image and superimposed to evaluate sagittal and vertical growth. The transverse widths of various skeletal areas (anterior and posterior nasal cavity, infra orbital foramina, infrazygomatic, mental foramina, Gonion, Antegonion, condyle) and the dentoalveolus at the first molar (2 mm, 6 mm, and 10 mm apical to the CEJ) were measured. Results: This study reports separated male and female average values. Relative to the cranial base, Orbitale, A point, and B point move anteriorly and inferiorly. Porion moves posteriorly and inferiorly. Nasion moves anteriorly and has a wide range of vertical movement. Within the maxilla, A point had variable sagittal movement and moves inferiorly. Within the mandible, B point has variable sagittal movement and moves superiorly, and the condyle moves superiorly. True rotation of the mandible and maxilla occurs in a counterclockwise direction, the inferior border remodels in a clockwise direction, the condyle rotates forward relative to the mandible, and the gonial angle reduces. These processes are correlated with each other and one subject had clockwise rotation of the jaws. The upper and lower first molars mesialize, upright bucco-lingually, and erupt vertically with age. The upper and lower central incisors erupt and the lower incisors procline. The transverse width of the posterior portions of the face increase more than the anterior. The mandibular and maxillary dentoalveoli increase at similar rates corono-apically. The maxillary dentoalveolus increases more than the mandibular dentoalveolus. Conclusions: Angular measurements with N, Or, Po, A, and B may not be reliable for longitudinal growth evaluation. This study confirms the unique facial patterns and correlations between developing processes described by Bjork and Skieller. The posterior skeletal increases in the mandible seems to primarily be the result of lengthening of the mandibular body. The small dentoalveolar increases in the mandible is likely the result of periosteal apposition. The skeletal and dentoaveolar transverse increases in the maxilla reflect the greater increases in the posterior than anterior portions of the mid-palatal suture. The width of the posterior portions of the maxilla and mandible increase in a coordinated fashion. The vertical eruption and bucco-lingual uprighting of the upper and lower first molars seem to bridge the differential sagittal, vertical, and transverse growth of the maxilla and mandible.

Chun-Hsi Chung
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