Cranial suture lineage and contributions to repair of the mouse skull.

The cranial sutures are proposed to be a stem cell niche, harbouring skeletal stem cells that are directly involved in development, homeostasis and healing. Like the craniofacial bones, the sutures are formed from both mesoderm and neural crest. During cranial bone repair, neural crest cells have been proposed to be key players; however, neural crest contributions to adult sutures are not well defined, and the relative importance of suture proximity is unclear. Here, we use genetic approaches to re-examine the neural crest-mesoderm boundaries in the adult mouse skull. These are combined with calvarial wounding experiments suggesting that suture proximity improves the efficiency of cranial repair. Furthermore, we demonstrate that Gli1+ and Axin2+ skeletal stem cells are present in all calvarial sutures examined. We propose that the position of the defect determines the availability of neural crest-derived progenitors, which appear to be a key element in the repair of calvarial defects.

Quantitative tooth wear analysis of index teeth compared to complete dentition.

OBJECTIVES: Recent software advancements have facilitated quantification of erosive tooth wear progression using intraoral scans. This paper investigated if wear on commonly affected surfaces (central incisors and first molars) was representative of wear on the full arch. METHODS: Bimaxillary digital intraoral scans (True Definition, 3 M, USA) of patients (n = 30) from the monitoring arm of the Radboud Tooth Wear Project, were taken at baseline and at 3 years (+/-10months). The occlusal/incisal surface of each tooth (excluding 3rd molars) was analysed for volume change and volume change per mm of analysed surface area in WearCompare (www.leedsdigitaldentistry.com/Wearcompare) following previously published protocols. Data were normal, descriptives and multi-level linear regression analysis was performed in Stata v15.1 taking patient level and surface type data into account. RESULTS: Data from 556 surfaces in 29 patients were included in analysis. Per patient, mean volume loss (95 % CI) was -0.91mm3(-1.28,-0.53) on all surfaces, -1.85mm3(-2.83,-0.86) on index surfaces, -2.53mm3(-3.91,-1.15) on molar surfaces and -0.83 mm3(-1.34,-0.31) on upper central incisal surfaces. Statistical differences were observed between analysing all surfaces and index teeth(p = 0.002) in addition to molar surfaces(p < 0.0001). Mean volume loss per mm2 of surface analysed was -0.024 mm3 (-0.031,-0.017), -0.028mm3 (-0.041,-0.014), -0.030mm3 (-0.046,-0.013) and -0.025mm3 (-0.041,-0.010) for all surfaces, index surfaces, first molar surfaces and central incisor surfaces respectively with no statistical differences between groups. CONCLUSIONS: Wear on upper central incisors was not statistically different to full arch wear analysis. If the surface area is standardised, wear on both index surfaces are statistically similar to wear on the full arch. CLINICAL SIGNIFICANCE: These results suggest that analysing rates of wear on index teeth can be a resource-saving substitute for analysing rates of wear on the entire dentition, provided the surface area is standardised. If whole surfaces are analysed, the molar surfaces will show greater rates of wear.