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Introduction: CBCT imaging recently has become a very common diagnostic tool in the orthodontic literature. Recent research work has shown that CBCT imaging would give additional information regarding the volumetric assessment of the craniofacial structures. However, the previous published work has not considered the impact of the anterior-posterior skeletal classification and the vertical skeletal pattern on the volumetric assessment of the maxillary and mandibular bones. Aim: To evaluate maxillary and mandibular volumes (MxV and MdV, respectively) in hyper-divergent skeletal Class II (CII) and normo-divergent skeletal Class I (CI) patients and to investigate any possible correlation between CBCT derived lateral cephalometric variables and the calculated volumes. Materials and Methods: CBCT images of 60 patients (30 patients: CI, 30 patients: CII) were obtained and processed with Mimics® 17 software (Materialise, NV, Belgium). the Three dimensional models of both jaws were reconstructed and the related volumes were calculated using a novel approach. CBCT based cephalograms were also derived and linear and angular measurements of the craniofacial complex were obtained. Significance tests were based on t-tests (alpha set at 5%) and Pearson's correlation coefficients were calculated. Results: No significant differences were detected between the two groups in the MxV (p=0.435) and the MdV (p=0.507). In the CI group, no or weak correlations were found between the volumetric measurements and the 2D variables. In the CII group, there was a strong correlation between both MxV and MdV and both the posterior facial height (r=0.60, 0.78 respectively) and the facial height index (r=0.62, 0.72 respectively). A negative moderate correlation was found between both MxV and MdV and the mandibular plane angle (r=-0.48,-0.44 respectively) and Bjork's sum (r=-0.48,-0.44 respectively). Conclusion: There were no significant differences in the MxV and MdV between CI and CII skeletal patterns. Some cephalometric variables had moderate to strong correlation with the MxV and MdV in the CII group. [ABSTRACT FROM AUTHOR]

Background: Heat generation is considered a decisive factor in the occurrence of bone necrosis during implant placement, which can happen when the temperature exceeds a threshold of 47°C for 1 min. The use of a surgical guide to aid implant placement has gained popularity in the last few years. Whether it increases the risk of bone necrosis is still debatable., Objectives: The aim of the present study was to compare heat generation during implant placement with and without the use of a surgical guide., Material and Methods: The study sample consisted of 80 measurement sites placed near 40 dental implant sockets, which were prepared on 10 bone-like dental models. These models were divided into 5 models for the conventional method group and 5 models for the surgical guide group. Each model had 4 implant sockets prepared, and then two 1-millimeter-wide holes were drilled <1 mm away from the socket on the opposite sides of the implant socket to be used as temperature measurement sites. The diameter of the drill was standardized to 2.2 mm, and 4 different drill lengths were used (6, 8, 10, and 12 mm). The data was analyzed using the SPSS for Windows software, v. 13.0. A p-value of <0.05 was deemed statistically significant., Results: Significant differences were found in heat generation between the conventional group (41.07°C) and the surgical guide group (42.97°C) (p < 0.05). Significant changes in temperature were recorded after drilling, regardless of the method used (p < 0.05). Moreover, the length of the drill was associated with temperature changes, with longer drills generating more heat (p < 0.05)., Conclusions: Within the limitations of this study, the use of a surgical guide resulted in higher temperatures as compared to the conventional method of implant placement. However, the highest recorded temperature was far below the threshold for bone necrosis.