Reinforcement in removable prosthodontics: a literature review

Removable complete denture with a metal base: Integration of digital design and conventional fabrication techniques

OBJECTIVE

Digitally-designed removable complete dentures are typically composed of a resin denture base without a metal framework. However, metal denture bases are preferable as resin bases are more susceptible to fracture. Therefore, this article introduces a unique technique that integrates computer-aided design (CAD) and conventional resin processing for the fabrication of removable complete dentures with a metal framework.

CLINICAL CONSIDERATIONS

A maxillary complete denture with a metal base and a mandibular implant-retained overdenture reinforced with a metal framework were fabricated. The dentures were designed using CAD software and a tooth library. The denture bases were milled from wax disks, and artificial teeth were placed to complete the wax dentures. The metal frameworks were also designed using CAD software and produced via casting of printed resin patterns. Finally, conventional denture processing techniques were applied to obtain dentures with metal frameworks.

CONCLUSIONS

A digitally designed, removable complete denture with a metal base can be successfully fabricated using the described technique, which merges digital design and conventional methods. This article demonstrates the feasibility and potential advantages of this innovative approach in denture fabrication.

CLINICAL SIGNIFICANCE

The presented technique provides the following advantages: digital design features, precise space above implant overdenture attachments for a metal framework, convenience of esthetic evaluation with printed trial dentures, long-term data storage and duplication, reliable bond between the artificial teeth and denture base, and enhanced strength of the removable complete denture due to the metal reinforcement.

Evaluation of flexural properties and dynamic mechanical analysis of glass fiber-reinforced polyamide resin

Purpose:

The aim of this study was to evaluate flexural strength, elastic modulus and dynamic mechanical analysis (DMA) of heat-polymerized polymethyl methacrylate resin, polyamide resin and glass fiber-reinforced polyamide resin.

Materials and methods:

Three groups were determined according to denture base materials as polymethyl methacrylate resin (H), polyamide resin (P) and glass fiber reinforced polyamide resin (R). Sixteen specimens for each denture base material were prepared with dimensions of 64x10x3.3 mm for three-point bending test. Two specimens for each denture base material were prepared with dimensions of 30x10x3 mm for DMA. Polymethyl methacrylate and polyamide specimens were prepared according to the manufacturer’s recommendations. The silane was applied to glass fibers (4.5 mm length) 2% by weight of the polyamide resin, they were placed in polyamide resin cartilages and injected to the mold. The thermal aging procedure was applied to half of specimens of each material (n=8). Flexural strength and elastic modulus of the specimens were determined by three-point bending test at a speed of 5 mm/ min. DMA was performed to 1 specimen from each group to evaluate viscoelastic properties. Data were analyzed with one-way ANOVA, Tukey and Paired t tests.

Results:

A statistically significant difference was found in flexural strength and elastic modulus values of denture base materials (p=0.00). The highest flexural strength and elastic modulus values were observed in polymethyl methacrylate group. There was no significant difference between polyamide and glass-fiber reinforced polyamide groups (p=0.497). No significant difference was determined in all threedenture base materials before and after aging procedure.

Conclusion:

The reinforcement with glass-fibers did not affect the flexural strength and elastic modulus of polyamide resin.

Mechanical properties and surface roughness of chitosan reinforced heat polymerized denture base resin

PURPOSE

The antifungal property of chitosan (Ch) in denture base resin (DBR) was well established. Ch influence on the mechanical properties of DBR is less studied in the literature and is vital for clinical success of denture. This study estimates the effect of different concentrations of Ch on the flexural strength (FS), fracture toughness (FT), impact strength (IS) and surface roughness (Ra) in heat polymerized DBR.

METHODS

A total of 160 samples were divided into 4 groups (n =10) by weight percentage - Ch 0, Ch 5, Ch 10, Ch 15. FS and FT were estimated by three-point bending test. IS was determined by Charpy test. Ra was evaluated by non-contact laser surface profilometer. The tested samples were characterized by scanning electron microscope and Fourier transformation infra-red spectroscopy. Data were statistical analyzed with one-way ANOVA and Post hoc Bonferroni test.

RESULTS

FS, FT and IS improved with Ch addition when compared to control group. Ch5 showed higher "FS, FT, IS. (p<0.001)". Increased Ra was observed in Ch5 and Ch10 with significant statistical differences among the g roups. (p <0.001) Ch15 displayed decrease in Ra compared to control group.

CONCLUSIONS

The addition of Ch to DBR improved the "FS, FT, IS at 5%wt and Ra at 15%wt" of Ch.

Biological and technical complications in root cap-retained overdentures after 3-15 years in situ: a retrospective clinical study

OBJECTIVES

This retrospective clinical study investigates the frequency of biological and technical complications in patients rehabilitated by natural root-retained overdentures (RODs) with cast post-and-cores (root caps) wearing precision attachments and analyses factors influencing complication rates (e.g. oral hygiene routines).

MATERIALS AND METHODS

Patients formerly treated with RODs were invited for a cost-free clinical visit to evaluate their intraoral status. Furthermore, they were interviewed and patient records were screened for complications occurring since denture delivery. Statistical models include descriptive analyses, Fisher's exact test, odds ratios, and a multivariate regression model.

RESULTS

A total of 114 patients wearing 128 RODs with a total of 280 abutment teeth were evaluated (mean service time: 7.9 years). Technical complications occurred in 68.8% of the RODs, with matrix loosening being the most frequent complication (50.1%). Biological complications occurred in 53.9% of all RODs, with the presence of denture stomatitis being the most common biological complication (38.3%). The presence of denture stomatitis was significantly higher in the maxilla relative to the mandible (p = 0.0029), in subjects cleaning their dentures less than twice a day (p < 0.001), in subjects regularly using CHX-containing products (p = 0.036) and in subjects with a plaque index > 40% (p < 0.001).

CONCLUSIONS

Root cap-retained overdentures with precision attachments are a viable treatment option in partially dentate subjects, even over long-term periods. However, high complication rates should be expected.

CLINICAL RELEVANCE

Establishing good oral hygiene is a decisive factor in preventing complications in RODs. Furthermore, CHX-containing products may not be recommended for routine domestic use.

Influence of High-Pressure Polymerization on Mechanical Properties of Denture Base Resins

PURPOSE

The purpose of this study was to study the influence of high-pressure (HP) polymerization on the mechanical properties of denture base PMMA resins compared with conventional thermopolymerization and PMMA discs for digital dentures.

MATERIALS AND METHODS

Three groups of blocks were prepared: Probase Hot (Ivoclar Vivadent, Lichtenstein) conventionally heat polymerized at 100°C, Probase Hot heat polymerized at 100°C under HP (200 MPa) and Ivobase CAD (Ivoclar Vivadent, Lichtenstein). Samples for mechanical/physical (n = 30) and samples for viscoelastic (n = 10) characterizations were cut from the blocks. Flexural strength (σ_f ), elastic modulus (E_f ), hardness, density (ρ), flexural deformation at maximal flexural stress, flexural load energy (U_r ) and viscoelastic properties (E', E'', Tanδ, T_g ) were analyzed using one-way ANOVA (α = 0.05), Scheffé multiple means comparisons (α = 0.05) and Weibull statistics (for σ_f ). SEM images of the fractured surfaces were obtained.

RESULTS

E_f , E', E'' and density of HP polymerized Probase hot were significantly higher than conventional heat polymerized Probase Hot, whereas T_g was significantly lower and σ_f , Tanδ, hardness, flexural deformation at maximal flexural stress, U_r were not significantly different. The highest values for σ_f , flexural deformation at maximal flexural stress, U_r and Weibull modulus were obtained with Ivobase CAD.

CONCLUSION

HP polymerization does not significantly increase the mechanical properties of denture base resins.

Overdenture Prostheses with Metal Copings: A Retrospective Analysis of Survival and Prosthodontic Complications

PURPOSE

To retrospectively evaluate complications associated with overdentures and abutment teeth restored with metal copings, including post-procedural and prosthetic problems; also to analyze the frequency and influencing factors associated with these problems.

MATERIALS AND METHODS

A total of 80 subjects (48 females, 32 males, mean age 62 years) wearing root-supported overdentures were enrolled in the study. All participants were thoroughly examined by a single examiner, and appropriate maintenance care was performed. The 80 subjects had 270 abutments, which were endodontically treated teeth. All 80 subjects were carefully interviewed, inspected, and evaluated for post-procedural and clinical problems with their overdentures for an observation period of up to 5 years.

RESULTS

Of the post-procedural problems evaluated, the most common problems were gingival inflammation (69%) and root caries (36%) because of poor oral hygiene (41%) and loss of metal copings (34%), followed by overdenture base fracture over abutment teeth (34%). Other post-procedural problems reported were loss of overdenture stability (23%), incidence of overdenture repair (20%), poor retention (18%), incidental finding of root fragments (unplanned) in the jaws (15%), and up to two grade net change in the mobility of overdenture abutments (8%). All prostheses were in use at the time of data collection and observation up to 5 years.

CONCLUSIONS

Overdenture therapy was satisfactory; however, post-procedural and prosthetic complications and aftercare maintenance must not be underestimated.