Measurement of interfacial porosity at the acrylic resin/denture tooth interface

Effectiveness of disinfectant solutions associated or not with brushing on the biofilm control of a 3D printed-denture base resin

BACKGROUND

The formation of biofilm on denture bases is a recurrent clinical problem that favors the development of denture stomatitis. The effectiveness of a hygiene protocol in a 3D-printed denture base resin is still uncertain.

OBJECTIVE

To evaluate of the effectiveness of immersion, associated or not with brushing in a soap solution, on the biofilm control of a 3D-printed denture base resin.

METHODOLOGY

Specimens of denture base resins [Cosmos Denture (COS) and Classico (CLA/control)] were contaminated in vitro with Candida albicans and immersed in sodium hypochlorite 0.25% (SH, alkaline peroxide) AP, chlorhexidine digluconate 2% (CD or PBS-Control), associated or not with brushing with 0.78% Lifebuoy soap. Roughness was evaluated before and after brushing and immersion. The effectiveness of the protocols was assessed by CFU/mL, cellular metabolism (XTT), scanning electron microscopy (SEM), and confocal scanning laser microscopy. Data were analyzed by T student, ANOVA/Welch, and Tukey/Gomes-Howell pos-hoc tests (α = 0.05).

RESULTS

CLA showed greater roughness than COS. CFU/mL and XTT were higher in COS resin with a higher hyphae formation. Immersion in SH and CD eliminated CFU/mL and reduced XTT for both resins, associated or not with brushing. AP reduced CFU/mL only when associated with brushing.

CONCLUSIONS

The biofilm on the 3D-printed resin was thicker and presumably more pathogenic, regardless of its smoother surface. Immersions in SH 0.25% and CD 2% are effective hygiene protocols for both resins, associated or not with brushing. AP should be recommended when associated with brushing with a Lifebuoy 0.78% solution.

Effect of Chitosan and Acrylic Acid Addition to Acrylic Resin on Porosity and Streptococcus mutans Growth in Denture Base

OBJECTIVE

 This work aimed to determine the effect of adding chitosan and acrylic acid to acrylic resin denture base on the porosity of the material and the growth of Streptococcus mutans.

MATERIALS AND METHODS

 This study is an experimental laboratory research. Samples were divided into the following three groups (n = 10): group 1 was the control group, group 2 was the acrylic resin mixture with 1% chitosan and acrylate acid, and group 3 was the acrylic resin mixture with 2% chitosan and acrylate acid. S. mutans growth was tested using the dilution method, and porosity was examined using an optical microscope. Data were calculated by one-way analysis of variance (p < 0.05) and correlation analysis.

RESULTS

 The acrylic resin added with 2% chitosan and acrylic acid showed pores with an almost spherical shape and the smallest size. Significant difference (p < 0.05) was observed among all the groups. A positive and extremely strong correlation was found between porosity and S. mutans growth.

CONCLUSION

 Chitosan and acrylic acid at 1 and 2% concentrations can be added to acrylic resin to minimize the porosity of the denture base and reduce the growth of S. mutans. A less porous denture is associated with a low S. mutans growth rate.

Silver nanoparticles in denture adhesive: An antimicrobial approach against Candida albicans

OBJECTIVE

To evaluate the antimicrobial potential of silver nanoparticles (Ag NPs) synthesized using three different routes (ultraviolet light, Turkevich, and green chemistry method using Glycine max extract) associated with COREGA® denture powder adhesive.

METHODS

Heat-cured acrylic resin specimens were treated with different Ag NPs associated with the adhesive (AD + Ag UV, AD + Ag Turk, and AD + Ag Gm groups). As controls, the specimens were treated with a combination of adhesive and nystatin (AD + Nyst group), only adhesive (AD group), or submerged on the surface of the specimens (PBS group). After the treatments, biofilms of C. albicans developed for 3, 6, and 12 h on the specimen surfaces. The biofilm was quantified using colony-forming units per milliliter, colorimetric assay, and confocal laser scanning microscopy.

RESULTS

Regardless of the period, we observed an inhibition of fungal load and a reduction in metabolic activity and biofilm mass in the resin specimens treated with the combinations AD/Ag NPs, compared to AD and PBS. The antimicrobial action of the AD + Turk and AD + Ag Gm groups was similar than that for the AD + Nyst group in all periods and viability tests, except for the biofilm mass (12 h).

CONCLUSIONS

The COREGA® adhesive with Ag NPs, mainly those synthesized using the Turkevich and Glycine max methods, showed excellent antimicrobial activity against C. albicans biofilms, maintained for up to 12 h.

CLINICAL SIGNIFICANCE

The association of Ag NPs to the adhesive can add preventive or therapeutic effects against denture stomatitis, to this prosthetic material.

Evaluation of Shear Bond Strength Between Denture Teeth and 3D-Printed Denture Base Resin

PURPOSE

The aim of this study was to evaluate the bond strength between two types of artificial teeth with a 3D-printed denture base resin using different bonding agents.

MATERIALS & METHODS

Two types of artificial teeth were evaluated: 3D-printed (Cosmos TEMP) and prefabricated polymethylmethacrylate (Biotone) bonded to cylinders (2.5 mm in height and 5 mm in diameter) of 3D-printed denture bases (Cosmos Denture designing by Meshmixer and printed by Flashforge Hunter DLP Resin 3D Printer). Two combinations between denture base and artificial teeth were eveluated: Cosmos Denture - Biotone, n = 30, and Cosmos Denture - Cosmos TEMP, n = 30. For each combination, the specimens were randomly distributed according to the bonding agent: 1. autopolymerized acrylic resin-Duralay, n = 10; 2. 3D-printed resin Cosmos TEMP, n = 10; and 3. methylmethacrylate monomer (MMA) + 3D-printed resin Cosmos TEMP, n = 10, totaling 60 specimens. The application of MMA was done conditioning the tooth surface for 180 seconds; the other agents were applied on the same surface. The virtual design of the 3D-printed resin teeth was obtained by scanning the first maxillary molar of the prefabricated teeth as the same protocol of cylinders. The control group (n = 10) was a conventional heat-polymerized denture base resin (Lucitone 550) bonded to the prefabricated resin teeth (Biotone). The shear bond tests were performed by applying a perpendicular force to the artificial tooth - denture base resin, through a chisel at 1mm / min until failure. Two-way ANOVA and Bonferroni post hoc tests (α = 0.05) were used for multiple comparisons.

RESULTS

For the Biotone tooth, the bond strength was significantly higher using MMA + Cosmos TEMP (10.04 MPa), and similar to the control (11.84 MPa, p = 0.484). For the 3D-printed tooth (Cosmos TEMP), the bond strength using the agents Cosmos TEMP (9.57 MPa) and MMA + Cosmos TEMP (12.72 MPa) were similar to the control (11.84 MPa, p = 0.169 and p = 1, respectively), but different from each other (p = 0.016).

CONCLUSIONS

From the results, it is recommended to use: MMA + Cosmos TEMP bonding agent for the Biotone tooth; and Cosmos TEMP or MMA + Cosmos TEMP bonding agents for the Cosmos TEMP tooth, both attached to the 3D-printed denture resin Cosmos Denture. This article is protected by copyright. All rights reserved.

Incorporating Digital Dentures into Clinical Practice: Flexible Workflows and Improved Clinical Outcomes

Replacement of missing teeth with complete denture prostheses have been successfully accomplished for decades. However, limitations of denture materials and the number of appointments required to fabricate new or replacement complete dentures preclude practicality. New innovations involving a partially or completely digital workflow facilitate the fabrication of complete dentures in fewer, shorter appointments, and by incorporating materials that exhibit improved physical properties. The purpose of this manuscript is to describe the variety of workflows that can be implemented to incorporate digital denture fabrication into clinical practice.

Evaluation of thermal conductivity and flexural strength properties of poly(methyl methacrylate) denture base material reinforced with different fillers

STATEMENT OF PROBLEM

Poly(methyl methacrylate) (PMMA) is widely used in prosthodontics as a denture base material. However, it has several disadvantages, including low strength and low thermal conductivity.

PURPOSE

The purpose of this in vitro study was to evaluate thermal conductivity and flexural strength after adding powdered Ag, TiO₂, ZrO₂, Al₂O₃, SiC, SiC-nano, Si₃N₄, and HA-nano in ratios of 10 wt% to PMMA.

MATERIAL AND METHODS

A total of 144 specimens were fabricated and divided into 18 groups. Specimens were left in water for 30 days. Thermal conductivity values were measured using a heat flowmeter, flexural strength was measured with a 3-point bend test, and specimens were investigated with environmental scanning electron microscopy. One-way ANOVA was used to compare means followed by using Duncan multiple range test (α=.05).

RESULTS

The thermal conductivity value of PMMA increased significantly after the addition of Si₃N₄, SiC, Al₂O₃, SiC-nano, TiO₂, ZrO₂, HA-nano, and Ag. Progressive increases in thermal conductivity were observed in Si₃N₄, SiC, and Al₂O₃ fillers. Flexural strength values of the control group were not significantly different from those of the SiC, Al₂O₃, or Ag group (P>.05). In the other groups, flexural strength values decreased significantly (P<.05). On the basis of electron microscopy, we observed that Si₃N₄, SiC, and Al₂O₃ powders had higher thermal conductivity values that are dissipated more homogeneously in PMMA.

CONCLUSIONS

Although the addition of 10 wt% SiC, Al₂O_3, and Ag powder to PMMA significantly increased thermal conductivity, the flexural strength values of PMMA were not significantly changed.

Bonding of acrylic denture teeth to MMA/PMMA and light-curing denture base materials: the role of conditioning liquids

OBJECTIVES

The connection between resin denture teeth and the denture base is essential for the integrity of partial and full dentures. The aim of the present study was to analyse the bond strength of acrylic denture teeth to two light curing denture base materials compared to the gold-standard (MMA/PMMA) using different conditioning liquids.

METHODS

The ridge laps of 220 identical denture teeth were ground and pre-treated using different conditioning liquids (MMA, an experimental conditioning liquid as well as the two commercially available liquids Palabond and Versyo.bond). The denture base materials (PalaXpress, Versyo.com, Eclipse) were applied using a split mould to obtain tensile bond strength specimens of identical shape. Ten specimens per test group were either stored in water for 24h or thermocycled (5000×, 5-55°C) prior to tensile bond strength testing (cross-head speed 10mm/min). Data was subjected to parametric statistics (α=0.05).

RESULTS

The three-way ANOVA revealed a significant influence of the material, pre-treatment as well as the storage. PalaXpress showed the highest bond strength (24.3MPa) of all materials tested after TC, whereas the use of MMA led to the most constant results. Lower values were recorded for Versyo.com (17.5MPa) and Eclipse (10.4MPa) bonded with Versyo.bond.

CONCLUSIONS

The results indicate that MMA/PMMA based denture base resins provide reliable and durable bond strength to acrylic denture teeth. Using light-curing denture base materials requires the application of appropriate conditioning liquids to obtain acceptable bond strength. The use of MMA affects bond strength to light-curing denture base materials.

CLINICAL SIGNIFICANCE

The pre-treatment of denture teeth is critical regarding their bond-strength to denture base materials and in turn for the integrity of removable full and partial dentures. Light-curing denture base resins are more sensitive to the correct tooth pre-treatment compared to conventional MMA/PMMA materials, requiring specific conditioning liquids.

Application of optical coherence tomography (OCT) to nondestructive inspection of dentures

The porosity of denture base resins continues to be one of the undesirable characteristics of acrylic resins. It is commonly accepted that porosity of the denture not only often leads to denture fractures, but also may function as a reservoir of potential pathogens. The purpose of this study was to present the first OCT images of finished dentures using a new advanced-type OCT scanner we have developed, and to discuss the application of our new OCT system for nondestructive inspection of dentures. Ten newly fabricated full dentures of outpatient of the National Center for Geriatrics and Gerontology in Japan were selected for this study. Two types of denture base resins were used for inspection by OCT, which provided clear images of all the dentures examined. Internal structures, not visually detectable, inspection, can be observed using this OCT system. It is concluded that OCT can detect nonvisible internal structures in dentures, a finding not reported to date. OCT may, therefore, be an appropriate method for detecting interior defects in dentures nondestructively.