Three-dimensional Mandible Models Research Articles

A novel dental reconfigurable drilling guide based on standardized drilling sleeves and personalized substrate

Drilling guide that consists of a personalized substrate and additional guide sleeves has been widely used to precisely position the implants in dental surgery. However, the traditional drilling guide cannot be reused or disassembled because the guide sleeves are affixed in the substrate. Additionally, the guide sleeves are not as wearable as they are made of titanium. In this paper, based on standardized drilling sleeves and a personalized substrate, a novel dental reconfigurable drilling guide is proposed, which is beneficial to ensure the accuracy of implant insertion. The drilling sleeves are installed in the substrate through transition fit and can be easily disassembled. First, the three-dimensional model of mandible was reconstructed based on the cone beam computed tomography data. Secondly, according to the implant planning from the dentist, the drilling sleeves were designed based on the diameter of special drills. The drilling sleeves was used in conjunction with the special drill. Thirdly, different substrates were designed through medical image processing software based on the oral cone-beam computed tomographic data. Afterwards, the designed drilling sleeves and substrates were manufactured by means of computer numerical control machining and three-dimensional printing, respectively. Finally, the reconfigurable drilling guide was formed by installing the standardized drilling sleeves in different substrates. The results were demonstrated that the standardized drilling sleeves can be reused in different substrates for different drilling guides. Reusing the reconfigurable drilling sleeves economizes medical materials, reduces the time to prepare the drilling guide, and simultaneously achieves prospective precision in the implant placement.

Investigation of a Modified Novel Technique in Bilateral Sagittal Splitting Osteotomy Fixation: Finite Element Analysis and In Vitro Biomechanical Test.

Purpose To evaluate the biomechanical properties of the modified novel 2-hole monocortical plate fixation (2HMCPf) and traditional 4-hole monocortical plate fixation (4HMCPf) techniques in bilateral sagittal splitting osteotomy (BSSO) synthesis using a finite element analysis (FEA) and an in vitro biomechanical test with the application of a shearing loading force on a sawbone mandible model. Materials and Methods A three-dimensional mandible models were generated using the geometry obtained from the computerized tomography image of a sawbone mandible. Plates and screws were generated and combined with the mandible in a CAD environment. The 2HMCPf and traditional 4HMCPf techniques for BSSO osteosynthesis were then analyzed under the occlusal load using the FEA. An in vitro biomechanical test was executed to verify the result of FEA. The force on fixation failure and pattern of failure were recorded. Results The results revealed that the von Mises Stress on the mandible cortical bone (75.98 MPa) and the screw/plate (457.19 MPa) of the 2HMCPf group was lower than that of the 4HMCPf group (987.68 MPa, 1781.59 MPa). The stress concentrated on the central region of the 4HMCPf group and the distal set of the 2HMCPf group. In vitro study using the sawbone mandible model showed mechanical failure at the region of the proximal segment near the osteotomy site with the 4HMCPf group (average 32.198 N) but no failure on the fixation sites with the 2HMCPf group. Instead, the mandible sawbone fractured on the condyle neck region (average 44.953 N). Conclusion From the biomechanical perspective, we proved that the 2HMCPf method was able to withstand a higher shearing loading force than the 4HMCPf fixation method in BSSO osteosynthesis.

Biomechanical evaluation of resorbable and titanium miniplates and of single and double miniplates for the treatment of mandibular condyle fractures

Mandibular condyle fractures are one of the most common facial bone fractures, and open reduction, which involves implanting miniplates to ensure rigid fixation of the fractured surfaces, is the standard treatment. The aim of this study was to compare the stress fields of resorbable and titanium miniplates and of single and double miniplates by taking the displacement between the fracture surfaces (interfragmentary displacement) into account. Three-dimensional mandible models were created based on computed tomography images from 10 patients. To simulate the common loading conditions that the mandible is exposed to during daily living, mastication and muscle forces were applied to each model. The von Mises stress distribution over the miniplates and the maximum displacements between the fractured surfaces were calculated using finite element analysis. The mean maximum stresses associated with the titanium miniplates were significantly higher than those associated with the resorbable miniplates (p<0.05). Moreover, the mean maximum interfragmentary displacements associated with the resorbable miniplates were higher than those associated with the titanium miniplates, but there was no significant difference (p>0.05). The stress and interfragmentary displacement results associated with the single and double miniplates (made of either of the two materials) were within the clinically acceptable limits.

Sex determination from the mandibular ramus flexure of Koreans by discrimination function analysis using three-dimensional mandible models

It has been known that mandible ramus flexure is an important morphologic trait for sex determination. However, it will be unavailable when mandible is incomplete or fragmented. Therefore, the anthropometric analysis on incomplete or fragmented mandible becomes more important. The aim of this study is to investigate the sex-discriminant potential of mandible ramus flexure on the Korean three-dimensional (3D) mandible models with anthropometric analysis. The sample consists of 240 three dimensional mandibular models obtained from Korean population (M:F; 120:120, mean age 46.2y), collected by The Catholic Institute for Applied Anatomy, The Catholic University of Korea. Anthropometric information about 11 metric was taken with Mimics, anthropometry libraries toolkit. These parameters were subjected to different discriminant function analyses using SPSS 17.0. Univariate analyses showed that the resubstitution accuracies for sex determination range from 50.4 to 77.1%. Mandibular flexure upper border (MFUB), maximum ramus vertical height (MRVH), and upper ramus vertical height (URVH) expressed the greatest dimorphism, 72.1 to 77.1%. Bivariate analyses indicated that the combination of MFUB and MRVH hold even higher resubstitution accuracy of 81.7%. Furthermore, the direct and stepwise discriminant analyses with the variables on the upper ramus above flexure could predict sex in 83.3 and 85.0%, respectively. When all variables of mandibular ramus flexure were input in stepwise discriminant analysis, the resubstitution accuracy arrived as high as 88.8%. Therefore, we concluded that the upper ramus above flexure hold the larger potentials than the mandibular ramus flexure itself to predict sexes, and that the equations in bivariate and multivariate analysis from our study will be helpful for sex determination on Korean population in forensic science and law.