Factors associated with bone thickness: Comparison of the cranium and humerus.

Cortical bone thickness is important for the mechanical function of bone. Ontogeny, aging, sex, body size, hormone levels, diet, behavior, and genetics potentially cause variations in postcranial cortical robusticity. However, the factors associated with cranial cortical robusticity remain poorly understood. Few studies have examined cortical robusticity in both cranial and postcranial bones jointly. In the present study, we used computed tomography (CT) images to measure cortical bone thicknesses in the cranial vault and humeral diaphysis. This study clearly showed that females have a greater cranial vault thickness and greater age-related increase in cranial vault thickness than males. We found an age-related increase in the full thickness of the temporal cranial vault and the width of the humeral diaphysis, as well as an age-related decrease in the cortical thickness of the frontal cranial vault and the cortical thickness of the humeral diaphysis, suggesting that the mechanisms of bone modeling in cranial and long bones are similar. A positive correlation between cortical indices in the cranial vault and humeral diaphysis also suggested that common factors affect cortical robusticity. We also examined the association of polymorphisms in the WNT16 and TNFSF11 genes with bone thickness. However, no significant associations were observed. The present study provides fundamental knowledge about similarities and differences in the mechanisms of bone modeling between cranial and postcranial bones.

The human EDAR 370V/A polymorphism affects tooth root morphology potentially through the modification of a reaction-diffusion system.

Morphological variations in human teeth have long been recognized and, in particular, the spatial and temporal distribution of two patterns of dental features in Asia, i.e., Sinodonty and Sundadonty, have contributed to our understanding of the human migration history. However, the molecular mechanisms underlying such dental variations have not yet been completely elucidated. Recent studies have clarified that a nonsynonymous variant in the ectodysplasin A receptor gene (EDAR 370V/A; rs3827760) contributes to crown traits related to Sinodonty. In this study, we examined the association between the EDAR polymorphism and tooth root traits by using computed tomography images and identified that the effects of the EDAR variant on the number and shape of roots differed depending on the tooth type. In addition, to better understand tooth root morphogenesis, a computational analysis for patterns of tooth roots was performed, assuming a reaction-diffusion system. The computational study suggested that the complicated effects of the EDAR polymorphism could be explained when it is considered that EDAR modifies the syntheses of multiple related molecules working in the reaction-diffusion dynamics. In this study, we shed light on the molecular mechanisms of tooth root morphogenesis, which are less understood in comparison to those of tooth crown morphogenesis.

Outcomes of an international volunteer surgical project for patients with cleft lip and/or cleft palate: A mission in developing Laos.

Cleft lip and/or palate (CL/P) is a common birth defect of complex etiology. CL/P surgery is generally performed in infancy to allow for improvements in esthetics, suckling, and speech disorders as quickly as possible. We have engaged in activities such as free-of-charge surgery for CL/P a total of 12 times from 2001 to 2016 in Lao People's Democratic Republic (Laos). The United Nations has designated Laos as a Least Developed Country; it is one of the poorest countries in Asia. We have carried out our activities for a long time, primarily in CL/P patients who cannot undergo surgery for financial reasons, and we have performed CL/P-related surgeries for 283 patients up to 2016. When we began our activities in 2001, the mean age at first cheiloplasty was 11.6 years, which dropped over time until 2016 when the mean age was 1.8 years. A linear regression analysis showed a significant difference between the age at first lip plasty and the year of first operation (ß = -0.35; P < 0.001). This was likely an effect of continuing to train local medical staff in surgical techniques and donating surgical tools and facilities over a period of 16 years while building a good relationship with local staff. However, the healthcare system in Laos is an obstacle to some patients who still cannot undergo CL/P surgery in infancy for financial reasons. We therefore need to support Laos to provide treatment on their own as we continue to carry out our activities for CL/P patients.

Measurement of Distraction Force in Cleft Lip and Palate Patients During Le Fort I Maxillary Advancement With Rigid External Distraction.

OBJECTIVE: Maxillary distraction osteogenesis (DO) is a mainstream surgical technique for patients who have severe maxillary hypoplasia associated with craniofacial syndromes and cleft-related deformities. However, limited information about the biomechanical aspects of maxillary DO is available limiting broad utilization and improvements to the procedure. The objective of this study was to analyze force levels during the active distraction process and to investigate the relationship between distraction force and maxillary movement during Le Fort I maxillary DO using a rigid external distraction (RED) system. PATIENTS: Microtension gauges were integrated into the distraction wires on each side of the RED system. Six patients with cleft lip and palate aged 12.8 to 23.5 years underwent strain gauge measurements during maxillary advancement with DO using an RED system. Lateral cephalograms were taken to measure maxillary horizontal, vertical, and linear movements after DO. RESULTS: The average linear maxillary movement was 11.2 mm (range 8.5-15.9 mm). The applied forces ranged from 13.4 to 26.8 N. The distance of maxillary movement was proportional to the distraction force. CONCLUSIONS: The measurement of distraction forces during DO provides important information with which to establish appropriate protocols. Patients requiring more advancement may require more distraction force. However, other factors such as scarring, patient anatomy, surgical freedom of the osteotomized maxilla, and the like, may affect the required force during DO with the RED system.