What Occlusal Scheme Should Be Used with Removable Partial Dentures?

Removable partial dentures: Part 1

The provision of removable partial dentures (RPDs) is an important skill for practitioners and it can often be challenging to make a successful prosthesis which the patient finds satisfactory. This three-part series has been designed to provide an overview of the clinical management of patients requiring RPDs. This first part provides a refresher of the aspects of the history and examination that are relevant to RPDs. We describe some key principles that are relevant to challenging denture cases. This will help the reader begin the treatment planning process and understand some of the factors which influence the prognosis of dentures.

Fracture Resistance of Zirconia Surveyed Crowns With Digitally Designed and Hand-Modified Occlusal Rest Seats

Background In light of the trend of using zirconia crowns, clinicians will likely face abutment included in removable partial dentures (RPD) designs with existing zirconia. However, the decision to replace the existing crown with a surveyed crown or modify the existing crown to accept the RPD is unclear. To the best of our knowledge, there is a lack of literature on the effect of preparing a rest seat on the existing monolithic zirconia crown in the patient's mouth on the fracture resistance of the crown. Therefore, in this study, we aimed to evaluate the fracture resistance of computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia surveyed crowns with digitally designed rest seats and hand-modified rest seats. Methods Thirty CAD/CAM zirconia surveyed crowns were digitally designed and fabricated and divided into groups (n=10 per group) as follows: Group 1 comprised surveyed crowns with no occlusal rest seat; Group 2 comprised surveyed crowns with a digitally designed mesial rest seat; and Group 3 comprised surveyed crowns with a hand-modified mesial rest seat. Then, with all the crowns cemented to metal dies, the specimens were subjected to a fracture resistance test using a universal testing machine (Model 8501 Instron, Norwood, MA, USA). Results Surveyed crowns without any rest seat and those with digitally created and hand-modified rest seats displayed different fracture resistances: crowns with no rest seat offered the highest fracture resistance (5831 ± 895.15 N), followed by those with a digitally designed and milled rest seat (5280 ± 1673.33 N). Crowns with a hand-modified rest seat provided the lowest fracture resistance (4976 ± 322.5 N). Based on our results, surveyed crowns without a rest seat displayed higher fracture resistance than those with a rest seat. Conclusion The fracture resistance of crowns with a digitally designed and milled rest seat was statistically similar to that of control crowns with no rest seat, whereas hand-modified rest seats significantly reduced the fracture resistance of surveyed zirconia crowns.

CAD-CAM denture teeth made on cast metal removable partial denture frameworks

Once the fit of the cast metal framework on a removable partial denture (RPD) has been verified, the manufacturer's prefabricated denture teeth are typically secured on the cast metal framework to prepare for a wax evaluation. Although prefabricated denture teeth are available in different tooth forms and sizes, they require modification to fit an edentulous space. In arches with severe space discrepancy, it may be inefficient and time-consuming to make modifications to prefabricated denture teeth. The technique described uses digital technology to fabricate custom denture teeth on a cast metal framework and establish harmonious occlusion. An edentulous space with more than a single tooth replacement is designed as a splinted fixed partial denture with a connector. The designed teeth are milled in the double-cross-linked polymer to prepare for a wax evaluation, and once verified, the RPD is processed by using heat polymerization. Modifications are made to the milled denture teeth after wax elimination to reduce the likelihood of acrylic resin bond failure.

Closed sinus lift and fixed prostheses versus implant-assisted overdentures in management of atrophied distal extension maxillary ridges: A one-year randomized clinical trial

STATEMENT OF PROBLEM

Rehabilitation of elderly or medically compromised patients with an atrophied unilateral posterior maxillary ridge by an implant-supported prosthesis may be complicated by maxillary sinus pneumatization with insufficient bone for implant placement.

PURPOSE

This short-term clinical trial assessed clinical results of closed sinus lift and fixed prosthesis versus implant-assisted overdentures in the management of participants with atrophied distal extension maxillary ridges.

MATERIAL AND METHODS

Forty participants with unilateral atrophying distal extension maxillary ridges were randomly assigned into 2 groups. The CSL group (n=20) participants received fixed prostheses supported by 3 implants following a closed sinus lift. The IOD group (n=20) participants received removable partial overdentures assisted by a single implant that was positioned mesially to the maxillary sinus. The modified plaque index (MPI), modified gingival index (MGI), pocket depth (PD), implant stability (IS), and vertical bone loss (VBL) were measured at prosthesis delivery (T0), and 6 (T6) and 12 months (T12) after delivery. The oral health impact profile (OHIP-14) questionnaire was used to assess oral health-related quality of life (OHRQoL) at T12. Significant differences between observation times were performed using Friedman and Wilcoxon signed-rank tests for MPI and MGI and using repeated measures ANOVA with Bonferroni correction of P values for PD, IS, VBL, and OHIP. Between-group comparison of MPI and MGI the Mann-Whitney test was used, while for PD, IS, VBL, and OHIP comparison was made using independent samples t test (α=.05 for all tests).

RESULTS

The implant survival rates were 100% for both groups. MPI and PD significantly increased with time for both groups. MGI significantly increased with time for the CSL group only (P=.049). The IS significantly decreased with time for the IOD group. VBL increased significantly from T6 to T12 for the CSL (P=.042) and the IOD (P=.002) groups. The CSL group recorded higher MPI, MGI, PD, and IS values than the IOD group (P<.05). The IOD group recorded higher VBL than the CSL group (P<.001). The CSL group scored significantly lower OHIP-14 values (better OHRQoL) than the IOD group for all values (P<.05).

CONCLUSIONS

In comparison with implant-assisted partial overdentures, closed sinus lift with fixed prostheses had higher implant stability, reduced bone loss, and higher participant OHRQoL. However, peri-implant soft tissue health was found to be better with implant overdentures.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The Scientific Investigation Committee of the American Academy of Restorative Dentistry offers this review of the 2021 dental literature in restorative dentistry to inform busy dentists regarding noteworthy scientific and clinical progress over the past year. Each member of the committee brings discipline-specific expertise to coverage of this broad topical area. Specific subject areas addressed, in order of the appearance in this report, include COVID-19 and the dental profession (new); prosthodontics; periodontics, alveolar bone, and peri-implant tissues; implant dentistry; dental materials and therapeutics; occlusion and temporomandibular disorders; sleep-related breathing disorders; oral medicine and oral and maxillofacial surgery; and dental caries and cariology. The authors focused their efforts on reporting information likely to influence daily dental treatment decisions with an emphasis on future trends in dentistry. With the tremendous volume of dentistry and related literature being published daily, this review cannot possibly be comprehensive. Rather, its purpose is to update interested readers and provide important resource material for those interested in pursuing greater details on their own. It remains our intent to assist colleagues in negotiating the extensive volume of important information being published annually. It is our hope that readers find this work useful in successfully managing the patients and dental problems they encounter.

Stress Distribution Pattern in Mini Dental Implant-Assisted RPD with Different Clasp Designs: 3D Finite Element Analysis

Introduction

The removable partial denture (RPD) components, especially the retentive arm, play a major role in the loading characteristic on supporting structures.

Objective

To evaluate and compare the effect of different clasp designs on the stress distribution pattern, maximum von Mises stress, and average hydrostatic pressure on abutment teeth, as well as edentulous ridges, mini dental implants (MDIs), and peri-implant bone between the conventional removable partial denture (CRPD) and mini dental implant-assisted distal extension removable partial denture (IARPD) using a three-dimensional finite element analysis (3D FEA).

Materials and Methods

3D FEA models of mandibular arches, with and without bilateral MDI at the second molar areas, and Kennedy class I RPD frameworks, with RPA, RPI, Akers, and no clasp component, were generated. A total of 200 N vertical load was bilaterally applied on both sides of distal extension areas, and the stress was analyzed by 3D FEA.

Results

The stress concentration of IARPD with RPI clasp design was located more lingually on abutment teeth, MDI, and peri-implant bone, while the other designs were observed distally on the supporting structures. The maximum von Mises stress on the abutment root surface was decreased when the RPDs were assisted with MDIs. The CRPD and IARPD with the Akers clasp design showed the highest von Mises stress followed by the designs with RPA and RPI clasp, respectively. The average hydrostatic pressure in each group was in approximation.

Conclusion

The placement of MDIs on distal extension ridges helps to reduce the stress concentration on denture supporting structures. The maximum von Mises stress is affected by the different designs of clasp components. The CRPD and the IARPD with RPI clasp provide the least stress on supporting structures.