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Background: Dental cone beam computed tomography (CBCT) is commonly used to evaluate cancellous bone density before dental implant surgery. However, to our knowledge, no measurement approach has been standardized yet. This study aimed to evaluate the relationship between three different regions of interest (ROI) methods on cancellous bone density at the dental implant site using dental CBCT images. Methods: Patients' dental CBCT images (n = 300) obtained before dental implant surgery were processed using Mimics (Materialise, Leuven, Belgium). At the potential implant sites, the rectangle, cylinder, and surrounding cylinder ROI methods were used to measure bone density. Repeated measures one-way analysis of variance was performed to compare the three ROI methods in terms of measurement results. Pearson correlation analysis was performed to identify the likely pair-wise correlations between the three ROI methods. Results: The density value obtained using the surrounding cylinder approach (grayscale value [GV],523.56 ± 228.03) was significantly higher than the values obtained using the rectangle (GV, 497.04 ± 236.69) and cylinder (GV,493 ± 231.19) ROI methods in terms of results. Furthermore, significant correlations were noted between the ROI methods (r > 0.965; p < 0.001). Conclusions: The density measured using the surrounding cylinder method was the highest. The choice of method may not influence the trends of measurement results. Trial registration: This study was approved by the Institutional Review Board of China Medical University Hospital, No. CMUH111-REC3-205. Informed consent was waived by the Institutional Review Board of China Medical University Hospital, CMUH111-REC3-205, owing to the retrospective nature of the study. [ABSTRACT FROM AUTHOR]

Few studies have investigated the effects of abutment screw diameter in the stress of dental implants and alveolar bones under occlusal forces. In this study, we investigated how variations in implant diameter, abutment screw diameter, and bone condition affect stresses in the abutment screw, implant, and surrounding bone. Three-dimensional finite element (FE) models were fabricated for dental implants with external hex-type abutments measuring 4 and 5 mm in diameter. The models also included abutment screws measuring 2.0 and 2.5 mm in diameter. Each implant model was integrated with the mandibular bone comprising the cortical bone and four types of cancellous bone. In total, 12 finite element models were generated, subjected to three different occlusal forces, and analyzed using FE software to investigate the stress distribution of dental implant and alveolar bone. Wider implants demonstrated lower stresses in implant and bone compared with standard-diameter implants. The quality of cancellous bone has a minimal impact on the stress values of the implant, abutment screw, and cortical bone. Regardless of occlusal arrangement or quality of cancellous bone, a consistent pattern emerged: larger abutment screw diameters led to increased stress levels on the screws, while the stress levels in both cortical and cancellous bone showed comparatively minor fluctuations. Wider implants tend to have better stress distribution than standard-diameter implants. The potential advantage of augmenting the abutment screw diameter is unfavorable. It may result in elevated stresses in the implant system. [ABSTRACT FROM AUTHOR]

Objective: This study proposed a new classification method of bone quantity and quality at the dental implant site using cone-beam computed tomography (CBCT) image analysis, classifying cortical and cancellous bones separately and using CBCT for quantitative analysis. Methods: Preoperative CBCT images were obtained from 128 implant patients (315 sites). First, measure the crestal cortical bone thickness (in mm) and the cancellous bone density [in grayscale values (GV) and bone mineral density (g/cm3)] at the implant sites. The new classification for bone quality at the implant site proposed in this study is a "nine-square division" bone classification system, where the cortical bone thickness is classified into A: > 1.1 mm, B:0.7–1.1 mm, and C: < 0.7 mm, and the cancellous bone density is classified into 1: > 600 GV (= 420 g/cm3), 2:300–600 GV (= 160 g/cm3–420 g/cm3), and 3: < 300 GV (= 160 g/cm3). Results: The results of the nine bone type proportions based on the new jawbone classification were as follows: A1 (8.57%,27/315), A2 (13.02%), A3 (4.13%), B1 (17.78%), B2 (20.63%), B3 (8.57%) C1 (4.44%), C2 (14.29%), and C3 (8.57%). Conclusions: The proposed classification can complement the parts overlooked in previous bone classification methods (bone types A3 and C1). Trial registration: The retrospective registration of this study was approved by the Institutional Review Board of China Medical University Hospital, No. CMUH 108-REC2-181. [ABSTRACT FROM AUTHOR]

Residual alveolar ridge resorption often occurs after tooth extraction, which causes issues requiring further prothesis rehabilitation. A treatment concept referred to as all-on-four, involving fixed dentures supported with four implants, was recently developed. The current study aimed to determine the effect of changing bone atrophy and implant length in all-on-four treatments on stress and strain in the surrounding bone of the implant. A three-dimensional finite element method was used in this research. The stress analysis was conducted with von Mises stress values. Two types of synthetic jawbone models with mild and moderate atrophy were used. Furthermore, two different implant lengths with a similar implant design and diameter were selected, and they were classified into eight models. Then, the bone model was assessed via a computed tomography (CT) scan and was transformed into a virtual model in Geomagic and SolidWorks with implant rebuilding. After modifying bone atrophy, the von Mises stresses in the surrounding bone of the implant were as follows: mild type 2 < mild type 3 < moderate type 3 < moderate type 4. The bone quantity change rate increased more than when bone conditions were limited. Compared with changes in implant lengths, the stresses in the peri-implant surrounding bone were generally higher in the 9 mm implant length group than in the 11.5 mm group. However, the results did not significantly differ. In conclusion, the von Mises stress and strain increased in the models with moderate atrophy and low-density trabecular bone. Hence, bone atrophy and its presurgical diagnosis in long-term implant prognosis are crucial. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effect of bone–miniscrew contact percentage (BMC%) and bone quality and quantity on orthodontic miniscrew stability and the maximum insertion torque value (ITV). Orthodontic miniscrews of five different dimensions and several bovine iliac bone specimens were used in the evaluation. Miniscrews of each dimension group were inserted into 20 positions in bovine iliac bone specimens. The experiment was divided into three parts: (1) Bone quality and quantity were evaluated using cone-beam computed tomography (CBCT) and microcomputed tomography. (2) The 3D BMC% was calculated. (3) The ITVs during miniscrew insertion were recorded to evaluate the stability of the orthodontic miniscrews. The results indicated that longer and thicker miniscrews enabled higher ITVs. CBCT was used to accurately measure cortical bone thickness (r = 0.939, P < 0.05) and to predict the bone volume fraction of cancellous bone (r = 0.752, P < 0.05). BMC% was significantly influenced by miniscrew length. The contribution of cortical bone thickness to the ITV is greater than that of cancellous bone structure, and the contribution of cortical bone thickness to BMC% is greater than that of cancellous bone structure. Finally, the higher is BMC%, the greater is the ITV. This study concludes that use of CBCT may predict the mechanical stability of orthodontic miniscrews. [ABSTRACT FROM AUTHOR]