Comparison of Stress Dissipation Pattern Underneath Complete Denture with Various Posterior Teeth form: An In Vitro Study

Algorithm for Designing a Removable Complete Denture (RCD) Based on the FEM Analysis of Its Service Life

(1) Background: The paper addresses the computer simulation and prediction of the service life of the base of removable complete dentures (RCDs) under typical loads caused by biting and chewing food. For this purpose, the finite element method (FEM) was used. It is assumed that various blocks of teeth, such as incisors, canines, premolars and molars, are subjected to cyclic impacts during a human life. (2) Methods: Both symmetric and asymmetric mastication (two- and one-sided loads, respectively) cases were considered. The load level was assumed to be 100 N, which corresponds to the average muscular compression force of typical human jaws. (3) Results: The FEM analysis of the stress-strain state evolution for RCDs under cyclic loads was carried out. Maps of equivalent lines were drawn for the denture base in terms of its durability. A multi-axial criterion was implemented to determine the number of cycles prior to failure by the mechanism of a normal opening mode crack. The FEM-based assessment of the service life of RCDs enabled us to establish the critical stress concentration areas, thereby allowing for further planning for the correction of an occlusal scheme or teeth inclinations. As a result, the service life of RCDs under cyclic loading can be improved. (4) Conclusions: An algorithm for designing RCDs in the case of edentulism based on the FEM simulation using commercial software as part of the procedure is proposed.

Stress distribution and patient satisfaction in flexible and cast metal removable partial dentures: Finite element analysis and randomized pilot study

Purpose

To compare stress distribution in polyacetyl based flexible RPD (FRPD) with cast metal RPD (CRPD) by using three-dimensional finite element analysis (FEA) and patient satisfaction by using OHIP-14 questionnaire in participants with Kennedy's class I partially edentulous mandibular arch rehabilitated with CRPD and FRPD.

Material and methods

For FEA, 3D models of Kennedy's class I partially edentulous mandibular arch, CRPD in chrome-cobolt alloy, and polyacetyl based FRPD were geometrically modelled and subjected to a vertical load of 100 ​N bilaterally. The in vivo comparison of satisfaction was assessed by enrolling 22 participants with Kennedy's class I partially edentulous mandibular arch. After randomization, 11 participants were rehabilitated by CRPD (group C), and 11 participants by polyacetyl based FRPD (group F). OHIP-14 questionnaire in Hindi language was filled at 1 week and 1 year after denture insertion.

Results

Von Mises stress distribution in CRPD was maximum in mesial rest seat of the primary abutment (100 ​MPa) and minimum for edentulous ridge (7 ​MPa on bone and 6 ​MPa on mucosa). Von Mises stress distribution for polyaccetyl based FRPD was maximum in ridge (25 ​MPa) and minimum in periodontal ligament of the second premolar (3 ​MPa). Patient satisfaction in group F was significantly more than in group C at end of 1 year (P ​= ​.0158).

Conclusion

FRPD is useful in periodontally compromised abutment teeth and CRPD in resorbed ridge conditions. Patient satisfaction is more with polyacetyl based flexible RPD when compared with cast metal RPD at the end of 1 year.

Biomechanics of oral mucosa

The prevalence of prosthodontic treatment has been well recognized, and the need is continuously increasing with the ageing population. While the oral mucosa plays a critical role in the treatment outcome, the associated biomechanics is not yet fully understood. Using the literature available, this paper provides a critical review on four aspects of mucosal biomechanics, including static, dynamic, volumetric and interactive responses, which are interpreted by its elasticity, viscosity/permeability, apparent Poisson's ratio and friction coefficient, respectively. Both empirical studies and numerical models are analysed and compared to gain anatomical and physiological insights. Furthermore, the clinical applications of such biomechanical knowledge on the mucosa are explored to address some critical concerns, including stimuli for tissue remodelling (interstitial hydrostatic pressure), pressure–pain thresholds, tissue displaceability and residual bone resorption. Through this review, the state of the art in mucosal biomechanics and their clinical implications are discussed for future research interests, including clinical applications, computational modelling, design optimization and prosthetic fabrication.

Different Occlusal Schemes in a Persistent Protruding Complete Denture Wearer

Different types of artificial teeth and occlusal designs can be used in complete dentures. Bilateral balanced occlusion, lingualized occlusion, canine guidance, and monoplane are the main occlusal designs; however there is no agreement on which tooth arrangement is ideal for achieving success in complete dentures. This report presents an alternative for persistent involuntary protruding complete denture wearers through the use of artificial teeth with higher cusps. Due to an old and worn pair of complete dentures, the patient had the habit of protruding. New dentures were made with Biotone artificial teeth and in the trial session, the patient would still protrude. A new set was made with Premium artificial teeth, which present higher cusps. With these dentures, the involuntary protrusion did not occur. From the delivery to the follow-up sessions, the patient stopped protruding.