Annual review of selected scientific literature: Report of the committee on scientific investigation of the American Academy of Restorative Dentistry

The Stresses and Deformations in the Abfraction Lesions of the Lower Premolars Studied by the Finite Element Analyses: Case Report and Review of Literature

BACKGROUND

The purpose of the study was to investigate the behavior of hard dental structures of the teeth with abfraction lesions when experimental occlusal loads were applied.

METHODS

A 65-year-old patient came to the dentist because she had painful sensitivity in the temporomandibular joints and the lower right premolars. The patient was examined, and cone-beam computed tomography (CBCT) of the orofacial area was indicated. The data provided from the CBCT were processed with Mimics Innovation Suite 17 software to create the desired anatomical area in 3D format. Then, the structural calculation module was used in order to perform a finite element analysis of the lower right premolar teeth. A focused review of articles published between 2014 and 2023 from specialty literature regarding the FEA of premolars with abfraction lesions was also conducted.

RESULTS

The parcel area and the cervical third of the analyzed premolars proved to be the most vulnerable areas under the inclined direction of occlusal loads. The inclined application of experimental loads induced 3-4 times higher maximum shears, stresses, and deformations than the axial application of the same forces.

CONCLUSIONS

FEA can be used to identify structural deficiencies in teeth with abfractions, a fact that is particularly important during dental treatments to correct occlusal imbalances.

Is dynamic occlusal design necessary for anterior guidance recovery in the computer-aided design process? An in vitro study

OBJECTIVES

This study aimed to assess the effectiveness of patient-specific motion in restoring anterior guidance and to investigate the influence of occlusal plane position within a virtual articulator on the design of the anterior guide slope for incisors.

METHODS

Twenty participants' intraoral scan, occlusal plane position, and jaw motion data were recorded. The maxillary anterior teeth were virtually prepared, and the crowns were designed based on average virtual articulator (AVR), personalized virtual articulator (ART), and patient-specific motion (PSM). The anterior guide slope of maxillary central incisors (S1, S2, Sc, Sp) and the mesio-distal angle (MDA) of the canine of prostheses were compared to that of natural teeth (NAT). One-Way ANOVA was utilized to evaluate the effectiveness of the three methods in restoring the anterior guidance of maxillary anterior teeth.

RESULTS

The comparison of Sp and MDA showed no significant difference between the PSM and NAT groups (p > 0.05). However, Sp of the ART group was significantly smaller, while MDA was higher than that of the NAT group (p < 0.05). Sp did not differ significantly (p > 0.05) when the angle of the occlusal plane (AOP) was small. As the AOP increased, Sp of the ART and AVR groups were significantly smaller than that of the NAT group (p < 0.05). With a large AOP, Sp of the ART group was notably smaller than that of the NAT group (p < 0.05), while there was no significant difference between the AVR and NAT groups (p > 0.05).

CONCLUSIONS

Occlusal design based on patient-specific motion proved more effective in restoring natural anterior guidance. The anterior guidance of prostheses designed using a virtual articulator was influenced by occlusal plane position.

CLINICAL SIGNIFICANCE

The utilization of a jaw motion tracer facilitated the transfer of personalized occlusal plane positions and recorded jaw motion, which can be integrated into the digital prosthetic workflow for virtual occlusion adjustment. Occlusal design based on patient-specific motion more effectively restored lingual guidance of maxillary anterior crowns.

The influence of temporomandibular joint movement parameters on dental morphology

Association between tooth morphology, occlusal relations and mandibular condyle/glenoid fossa morphology is still a controversial issue in dentistry. The aim of the present study was to examine the influence of three important articular parameters on the dental morphology and the crown volume, quantifying the variation for each tooth group: incisor, canine, premolar and molar.

MATERIALS AND METHODS

All maxillary teeth from a set of basic study models were prepared for zirconia single crowns. The models were scanned and then, using a computer aided design software, they were mounted in a virtual articulator and specific mandibular movements were defined. The crown morphology was designed and statically adapted. Ten models were obtained by dynamical adjustment of the basic model for successively modified articular parameters: sagittal condylar inclination (SCI)=30°, Bennett angle (BA)=10°, Immediate side shift (ISS)=0.5mm - for control and SCI: 40°, 50° and 60° with BA and ISS as control, BA: 15°, 20° and 25° with SCI and ISS as control, ISS: 1.5mm, 1.0mm and 0.0mm with SCI and BA as control - for the nine test models. The following measurements were performed three times on the right side of each model: volume for each tooth group, slope (S) for the central incisor, S and mesio-distal angle (MDA) for canine, S, MDA and vestibulo-oral angle (VOA) for the first premolar and molar.

RESULTS

When SCI was varied, statistically significant changes as compared to the controls were found for incisor's and premolar's S, premolar's VOA and, for 50° and 60°, MDA and molar's MDA (for 50°) and VOA (for 60°). When BA was varied, significant changes were found for S (canine) and, in certain models, MDA (premolar, molar). Variations of ISS significantly changed mainly MDA for molars and, in two models, premolars.

CONCLUSIONS

Within the limits of this study, among the articular parameters, SCI mostly influenced the dynamic tooth morphology, but canine and molar morphology was stronger influenced by BA and/or ISS.