Adaptation of cobalt chromium frameworks fabricated by conventional versus selective laser melting techniques: An in vitro and clinical assessment.

STATEMENT OF PROBLEM: Three-dimensional (3D) printing of cobalt chromium (Co-Cr) removable partial dentures (RPDs)by selective laser melting (SLM) has been claimed to be less challenging than by conventional casting and provides significant improvements. However, the adaptation and fit of the SLM framework and the optimum build orientation are still unclear. PURPOSE: The purpose of this in vitro and clinical study was to evaluate the effect of different build orientations on the adaptation of removable partial denture frameworks fabricated by SLM technology in vitro and to compare the adaptation of the SLM and conventional RPD frameworks clinically. MATERIAL AND METHODS: A master model simulating a maxillary arch of Kennedy class III modification 1 was scanned and duplicated to create a virtual 3D cast and reference cast. Four groups (n=40) of Co-Cr RPD frameworks were fabricated. For the SLM groups, the Co-Cr framework was virtually designed and exported for SLM printing. The SLM printing was done in 3 different build orientations: 0-degree (n=10), 45-degree (n=10), and 90-degree (n=10) groups. Other Co-Cr frameworks were conventionally cast (n=10). All Co-Cr frameworks were scanned and virtually superimposed with the master model using a surface-matching software program. The gap under 9 selected points in the palatal major connectors was analyzed and calculated. A smaller gap indicates more surface adaptation and close contact between the palatal major connector and the master model. The data were analyzed using the Kruskal-Wallis and Dunnett T3 tests (α=.05). Three patients with a partially dentate maxillary arch were enrolled in the clinical part based on inclusion criteria. Two RPD frameworks were provided for each patient (conventional casting and SLM printing). The adaptation of each framework was assessed by measuring the gap between the palatal major connector of the framework and the palate with light-body silicone. The differences in adaptation between the conventional and SLM frameworks were compared by using independent t tests (α=.05). RESULTS: The in vitro study identified significant differences in the adaptation of the palatal major connector among the 4 groups (P<.001), except for conventional and 0-degree SLM printing (P=.999). The conventional and 0-degree SLM frameworks exhibited the best adaptation, with the lowest gap underneath the palatal major connector of the RPD framework (0.01 ±0.02 mm and 0.01 ±0.01 mm, respectively). In the clinical part of the study, no significant difference was found between the adaptation of SLM and the conventional framework (P=.430) CONCLUSIONS: The adaptation of SLM printing can be maximized with less gap under the palatal major connector of the RPD framework when using the 0-degree build orientation. Co-Cr frameworks produced with SLM printing technology were comparable with conventionally produced frameworks; hence, SLM printed frameworks can be an alternative for clinical applications when optimum SLM parameters are applied.

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.

Antifungal effects of eugenol on Candida albicans adherence to denture polymers.

Background: The study's objective is to assess the adherence of C. albicans in different types of denture polymers and the effectiveness of eugenol and commercialized denture cleansers in the removal of C. albicans. Three types of denture base polymers (Lucitone® 199 (High-Impact PMMA), Impact® (conventional PMMA) and Eclipse® (UDMA)) and two hard denture reline materials (Kooliner® and Tokuyama® Rebase II Fast) were used in this study. Methods: Three hundred samples were prepared (6 × 2 mm disc shape) and divided into five groups of denture polymers (n = 60) and further subjected into five treatment groups (Polident®, Steradent, distilled water, eugenol 5-minutes, and eugenol 10-min). Three samples were extracted from each treatment group for baseline data (n = 12). Baseline data were used to calculate the initial number of C. albicans adherence. A 0.5 ml immersion solution from each specimen was cultured on YPD agar and incubated for 48 h at 37 °C. Visible colonies were counted using a colony counter machine (ROCKER Galaxy 230). Results: The result showed that the denture base polymer significantly affected the initial adherence (p = 0.007). The removal of C. albicans was also considerably affected by the denture base polymers and denture cleansers (p < 0.05). Lucitone®, Tokuyama®, and Kooliner® denture base polymers immersed for 3 min in eugenol showed the best results of removal. Discussion: This study's overall results showed that all denture polymers used as denture bases had an effect on C. albicans initial adherence and removal from the denture base, and eugenol is comparable to commercialised denture cleansers in reducing the number of attached C. albicans on denture base polymers.