Dimensional Accuracy of Dental Casting Patterns Fabricated Using Consumer 3D Printers

Consumer 3D printers have improved considerably due to the evolution of additive manufacturing. This study aimed to examine the accuracy of consumer printers in dental restoration. Cylindrical patterns mimicking a full crown were created and enlarged from 100% to 105% of the original size. Two types of consumer 3D printers, including a fused deposition modeling (FDM) device and a stereolithography (SLA) device, and two types of dental 3D printers, including a multi-jet device and an SLA device, were used to fabricate the patterns. Then, the outer and inner diameters and depths, and surface roughness of the patterns were measured. The changing rates of the outer diameter of models created using dental printers were significantly smaller than those of the models created using consumer printers (p < 0.05). Significantly greater surface roughness was obtained in the tooth axis of the model fabricated using the consumer FDM device (p < 0.05). However, no significant differences were observed on the surface roughness of both axes between the consumer SLA device and the dental devices (p > 0.05). However, FDM showed larger surface roughness than dental devices in both axes (p < 0.05). Thus, the SLA consumer printer can be applied to fabricate resin patterns with enlargement editing of 1–3% along the horizontal axis.

ISW for the Treatment of Deviated and Rotated Teeth

The objective of the case study is for the treatment of deviated and rotated teeth by ISW (Improved Super-elastic Ti-Ni alloy wire, developed by Tokyo Medical and Dental University). An adult female (37 years old) came to our clinic with a chief complaint of abnormal tooth axis of lower arch combined with spacing and rotation of other teeth. This patient mentioned she didn’t care about the problem of facial asymmetry. By using ISW, lower deviated teeth were corrected rapidly. Rotation of lower left and right premolars were corrected simply by ISW leveling. For correction of rotated upper left second premolar, we placed a bracket on the mesial surface of #25 temporarily and Ni-Ti open coil-spring was placed in between #25 and #26 in order to increase inter-bracket span so as to create space for bracket bonding on the buccal surface. ISW was fully engaged into #25 and then rotation was corrected by further leveling. After 18 months of active treatment, a stable occlusion and a desirable esthetic outcome was achieved and the patient was pleased with the treatment result after the active treatment.

Passive Periodontal Sensation Threshold of Upper Molars in Patients with Myofascial Pain

Background and Objective: The relationship between periodontal sensation and Myofascial Pain (MP) is not yet fully clarified. The aim of this study was to test the null hypothesis that there is no difference in the periodontal sensation threshold between subjects with MP and subjects with no Temporomandibular Disorders (TMD). Methods: Participants have clinically assessed in accordance with the Research Diagnostic Criteria for Temporomandibular Disorders version 1.0 guidelines and assigned to the MP group (mean age 54.8 ± 14.8 years; 1 male and 11 females) or the control group (mean age: 63.9 ± 13.2 years; 1 male and 15 females). The Passive Periodontal Sensation Threshold (PPST) was evaluated using impulsive mechanical stimulation on the occlusal surface parallel to the tooth axis of the maxillary first molar, if present. The difference in the mean PPST between the MP group and the control group was evaluated using the Student t-test after checking for homoscedasticity. Results: The mean PPST value was 1050.1 ± 480.3 mN in the MP group and 712.3 ± 288.5 mN in the control group. A significant difference was observed between these mean PPST values (p = 0.045). Conclusion: There was a significant difference in PPST between the MP group and the control group. Although the etiology of the change of PPST is still unknown, the higher PPST value observed in MP patients suggests that future study on occlusal dysesthesia or occlusal sensation-related pathosis is warranted.

Analytical Methods and Finite Element Method Computation The dental - periodontal tissues response

The study of the biomechanical behaviour of dental-periodontal structures during orthodontic movement has been carried out on the basis of the analysis of values of equivalent stress following Von Mises theory, of the stress after the direction of the sz vertical force, which constitutes the essential component of the Von Mises equivalent stress, as well as on the basis of registering the deformities on the tooth axis. The processes of implementation, modelling, calculation and interpretation, using FEM, involved the following steps: defining the geometry and the structure of the model under analysis; meshing the geometry of the structure; connecting the nodal elements; defining the limit conditions and restrictions; loading the created model with vertical forces of different intensities; solving the equation system, having as unknowns in the nodes the following: movement, tension, tension on the spatial coordinates, Von Mises stress. We simulated the orthodontic intrusion through the application of some vertical forces with different intensities and on structures with alveolar bone loss. The tension values in the tooth axis vary in direct proportion to the level of resorption of the alveolar bone, but the decisive element is the numerical value of the applied force, and not the absorption level.

Computation of tooth axes of existent and missing teeth from 3D CT images

Orientations of tooth axes are important quantitative information used in dental diagnosis and surgery planning. However, their computation is a complex problem, and the existing methods have respective limitations. This paper proposes new methods to compute 3D tooth axes from 3D CT images for existent teeth with single root or multiple roots and to estimate 3D tooth axes from 3D CT images for missing teeth. The tooth axis of a single-root tooth will be determined by segmenting the pulp cavity of the tooth and computing the principal direction of the pulp cavity, and the estimation of tooth axes of the missing teeth is modeled as an interpolation problem of some quaternions along a 3D curve. The proposed methods can either avoid the difficult teeth segmentation problem or improve the limitations of existing methods. Their effectiveness and practicality are demonstrated by experimental results of different 3D CT images from the clinic.