Is microbial adhesion affected by the build orientation of a 3-dimensionally printed denture base resin?

The Effect of Manufacturing Factors on the Material Properties and Adhesion of C. albicans and S. mutans on Additive Denture Base Material

(1) Understanding the effects of manufacturing factors on microbial adhesion is essential for optimizing additive denture base materials and improving their clinical performance. This study evaluated how polymerization time, layer thickness, extended cleaning, and storage conditions influence C. albicans and S. mutans adhesion on a denture base material. (2) Specimens (n = 15/group, d = 8 mm, h = 2 mm) were additively fabricated or poured (reference). Digital light processing was performed with varying polymerization times, layer thicknesses, extended cleaning, and storage. Microbial adhesion was assessed using a luminescence assay. Surface properties were characterized by roughness (Sa/Sz), hardness, and surface free energy (SFE). Statistics: The Shapiro-Wilk test, ANOVA, Bonferroni post hoc test, and Pearson correlation (α = 0.05) were utilized. (3) Polymerization time, layer thickness, cleaning, and storage conditions significantly influenced C. albicans and S. mutans adhesion. Increased layer thickness reduced C. albicans adhesion but promoted S. mutans colonization, emphasizing the role of SFE. Extended polymerization and optimized cleaning reduced microbial adhesion, highlighting the need for tailored processing to enhance microbial resistance and material integrity. (4) Manufacturing factors influenced microbial adhesion, with additive materials reducing the abundance of C. albicans but increasing the abundance of S. mutans, underscoring the importance of material adjustments and extended polymerization to enhance microbial resistance.

CADCAM Versus Conventional Denture Bases: Network Meta-Analysis of In Vitro Studies Comparing Accuracy and Surface Properties

INTRODUCTION

This systematic review with network meta-analysis (NMA) analysed the current evidence on in vitro studies comparing trueness of fit, surface roughness, colour stability, surface wettability, water sorption, water solubility, and microbial adhesion between conventional and digital denture bases.

METHODS

From inception until December 2023, a systematic search of published in-vitro studies from Scopus, PubMed, and the Cochrane Central Register of Controlled Studies was conducted. The protocol was registered in PROSPERO (CRD42024531416). NMA compared properties related to dimensional accuracy and surface properties between conventional and digital dentures. The ranking was performed using the surface area under the cumulative ranking guidelines.

RESULTS

A total of 6004 articles were initially identified, of which 342 duplicates were removed, and 5566 were excluded by screening the titles and abstracts. A total of 96 articles were assessed by full-text reading, and 43 were included in the quantitative synthesis. As per the NMA results, MIL demonstrated significantly higher trueness of fit when compared with conventional compression moulding (standardized mean differences [SMD] = -2.25 [95% CI: -4.09, -0.40]), P = .017 (<.05) and TDP (SMD = -1.57 [95%CI: -3.14, -0.01]) P < .05. MIL demonstrated significantly lower surface roughness when compared with conventional compression moulding (SMD = -0.99 [95% CI: -1.72, -0.26]), P = .008 (<.05), and TDP (SMD = -1.08 [95%CI: -1.95, -0.22]) P < .05.

CONCLUSIONS

There is conclusive evidence that milled digital denture bases demonstrate higher trueness of fit and lower surface roughness than 3D-printed denture bases and conventional denture bases, as demonstrated by the concurrent network and pairwise results.

CLINICAL RELEVANCE

In vitro studies show that milled digital dentures exhibit higher accuracy and lower surface roughness. The clinical performance of milled dentures in relation to these properties needs to be evaluated by high-quality randomized controlled clinical trials.

Bond Strength of Nanocomposite Hard Liner to CAD-CAM Milled, 3D Printed, and Conventionally Fabricated Denture Base Resins

BACKGROUND

To investigate the effect of zirconium dioxide nanoparticles (ZrO2NPs) on the shear bond strength (SBS) of hard denture lines bonded to different denture base resins.

METHODS

Five different denture bases were used in this study: conventional heat-cured resin, IvoCad, AvaDent, NextDent, and FormLabs, in acrylic specimens of 10 × 10 × 2.5 mm3 (N = 150, n = 10). Specimens were centered at the bottom of a silicon mold to create an auto-polymerized holder. Three major groups of reline material were used: no ZrO2NPs (control), 2 wt.%, and 4 wt.% ZrO2NPs. Reline was bonded to the resin surface using a customized jig. After polymerization, specimens were stored in distilled water, and 5000 thermal cycles were performed. Each specimen was fixed to an Instron machine, and SBS was tested using a blade loaded (1 mm/min) at the resin interface until failure. Data was collected and analyzed using two-way ANOVA and post hoc Tukey test (α = 0.05).

RESULTS

AvaDent showed the highest SBS when compared with other denture base materials (p < 0.001) except for IvoCad. The addition of ZrO2NPs significantly decreased the SBS of AvaDent (p = 0.003) and IvoCad (p = 0.001), while heat polymerized resin, Formlabs, and NextDent showed no significant change in SBS (p > 0.05).

CONCLUSION

CAD-CAM milled denture base resin showed higher SBS with pure denture reline. The addition of ZrO2NPs decreased the SBS of reline with CAD-CAM milled denture base resins but did not change bond strength with 3D printed and conventional denture base resins.

Adhesion of Candida Albicans to digital versus conventional acrylic resins: a systematic review and meta-analysis

BACKGROUND

The present systematic review and meta-analysis investigated the available evidence about the adherence of Candida Albicans to the digitally-fabricated acrylic resins (both milled and 3D-printed) compared to the conventional heat-polymerized acrylic resins.

METHODS

This study followed the guidelines of the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA). A comprehensive search of online databases/search tools (Web of Science, Scopus, PubMed, Ovid, and Google Scholar) was conducted for all relevant studies published up until May 29, 2023. Only in-vitro studies comparing the adherence of Candida albicans to the digital and conventional acrylic resins were included. The quantitative analyses were performed using RevMan v5.3 software.

RESULTS

Fourteen studies were included, 11 of which were meta-analyzed based on Colony Forming Unit (CFU) and Optical Density (OD) outcome measures. The pooled data revealed significantly lower candida colonization on the milled digitally-fabricated compared to the heat-polymerized conventionally-fabricated acrylic resin materials (MD = - 0.36; 95%CI = - 0.69, - 0.03; P = 0.03 and MD = - 0.04; 95%CI = - 0.06, - 0.01; P = 0.0008; as measured by CFU and OD respectively). However, no differences were found in the adhesion of Candida albicans between the 3D-printed digitally-fabricated compared to the heat-polymerized conventionally-fabricated acrylic resin materials (CFU: P = 0.11, and OD: P = 0.20).

CONCLUSION

The available evidence suggests that candida is less likely to adhere to the milled digitally-fabricated acrylic resins compared to the conventional ones.