ABSTRACT
The aim of this study was to investigate the prevalence of tooth agenesis, tooth malformation, and eruption patterns of upper canines/first premolars in Taiwanese children. A total of 132 cleft lip and cleft palate (CLCP) patients (82 boys and 50 girls) underwent alveolar bone grafting (ABG) between 2012 and 2022. The patients' dental records and X-ray images were inspected. We examined dental anomalies, including congenital missing teeth, microdontia, and transposition from the upper canines to the upper first premolars in these CLCP patients. Additionally, we investigated the mean ABG operation age (9.27 ± 0.76 years) of our patient; 40.9% of them received pre-ABG orthodontic treatment at 8.72 ± 0.70 years. Among the 132 cleft subjects, the prevalence of tooth agenesis is 73.5% (97/132). The most frequently missing teeth are the maxillary lateral incisors (right side: 46.2%; left side: 47.0%). In this study, microdontia are found in all the upper incisors, of which the highest percentage (18.9%) is observed in the upper left lateral incisors. The prevalence of upper canine and first premolar transposition is 10.6%. The pattern of tooth agenesis and microdontia of the upper lateral incisors shows a strong correlation with the cleft sites of these CLCP patients in our study. These results may support the idea that the patterns of dental anomalies in CLCP patients are region-specific.
ABSTRACT
PURPOSE: Stress analysis was performed for various implant designs using 3-dimensional finite element analysis approaches. MATERIALS AND METHODS: Six implant designs were included: 3 parallel-sided implants (no thread, triangular thread, and squared thread), 2 stepped configurations (non-thread and triangular thread), and a tapered body of implant with squared thread. All threads had spiral characteristics. The mandibular model was constructed from computed tomographic (CT) images of a human mandible, and the material properties were anisotropic (different in different directions). A 100-N oblique force was applied at a 45-degree angle to the long axis of the implants at the buccal cusp as the loading condition. RESULTS: Compared with cylindric implants, threaded implants (either triangular or squared) demonstrated increased peak stress at the crestal bone. The bone stress of stepped implants was decreased in the cortical region but was increased in the trabecular region. However, both threaded and stepped designs showed decreased interfacial stresses of bone near the valleys of the threaded and stepped areas. The tapered design decreased stresses by up to 32% in the cortical region and 17% in the trabecular region. CONCLUSIONS: Although threaded implants could not decrease the peak stress at the crestal bone, both threaded and stepped designs show an ability to dissipate the interfacial stresses of bone. The use of tapered implants could reduce peak stress in both cortical and trabecular bone.
