Three-Dimensional Assessment of Crown Size and Eruption Space for Developing Third Molars: Data Collection Techniques Based on Cone-Beam Computed Tomography (CBCT).

Third molar development and eruption are two related areas of major interest in dental research into the etiology of "wisdom tooth" impaction. Third molars are not only an excellent model for studying dental development but also of fundamental clinical importance because they are very frequently impacted. Because the third molar is located in the distal-most region of the oral cavity, clinical access is relatively challenging. With the increasingly widespread use of cone-beam computed tomography (CBCT) in dentistry, studies and measurements of the third molar and its eruption area have become considerably easier to do. Here we present a novel CBCT-based measurement methodology we developed for our recent investigations that we hope will also be useful for the broader dental research community.

A robust methodology for the quantitative assessment of the rat jawbone microstructure.

Micro-computed tomography can be applied for the assessment of the micro-architectural characteristics of the cortical and trabecular bones in either physiological or disease conditions. However, reports often lack a detailed description of the methodological steps used to analyse these images, such as the volumes of interest, the algorithms used for image filtration, the approach used for image segmentation, and the bone parameters quantified, thereby making it difficult to compare or reproduce the studies. This study addresses this critical need and aims to provide standardized assessment and consistent parameter reporting related to quantitative jawbone image analysis. Various regions of the rat jawbones were screened for their potential for standardized micro-computed tomography analysis. Furthermore, the volumes of interest that were anticipated to be most susceptible to bone structural changes in response to experimental interventions were defined. In the mandible, two volumes of interest were selected, namely, the condyle and the trabecular bone surrounding the three molars. In the maxilla, the maxillary tuberosity region and the inter-radicular septum of the second molar were considered as volumes of interest. The presented protocol provides a standardized and reproducible methodology for the analysis of relevant jawbone volumes of interest and is intended to ensure global, accurate, and consistent reporting of its morphometry. Furthermore, the proposed methodology has potential, as a variety of rodent animal models would benefit from its implementation.

Microanatomical assessment of nasomaxillary suture patency.

In addition to acting as a growth site, sutures in the facial skeleton are important for distributing mechanical forces during mastication. In the present study, the extent of fusion of a facial suture is assessed in two samples of adult bushbabies (Galago moholi and Otolemur garnettii). Microanatomical techniques were used to determine the loci of osseous bridges across the nasomaxillary suture (NMS). Histological sections containing sutures with osseous bridging were rated as "fused." One of the specimens was studied using micro-computed tomography before paraffin embedding and serial sectioning. At all ages, O. garnettii shows more advanced fusion of the NMS than G. moholi. The youngest O. garnettii shows multiple foci of fusion of the NMS; however, 13% of the posterior most suture is patent. Throughout the NMS of this animal, sutural fusion is isolated to one or two small osseous bridges, typically of woven bone. These bridges are most often on the external (superficial) surface of the suture, but in numerous sections the site of fusion occurs deep to an external notch. In G. moholi, the youngest adults studied showed little or no fusion across the NMS. However, the nasal and maxillary bones were indirectly tethered at some levels by other bones that were fused to both nasal and maxillary bones. These results indicate that microanatomical evidence is required to fully assess the extent of fusion of facial sutures. These findings also support previous observations of differing magnitude of suture fusion between the two species.