Positional accuracy of a single implant analog in additively manufactured casts in biobased model resin

ABSTRACT Objectives: To evaluate the positional accuracy of implant analogs in biobased model resin by comparing them to that of implant analogs in model resin casts and conventional analogs in dental stone casts. Methods: Polyvinylsiloxane impressions of a partially edentulous mandibular model with a single implant were made and poured in type IV dental stone. The same model was also digitized with an intraoral scanner and additively manufactured implant casts were fabricated in biobased model resin (FotoDent biobased model) and model resin (FotoDent model 2 beige-opaque) (n = 8). All casts and the model were digitized with a laboratory scanner, and the scan files were imported into a 3-dimensional analysis software (Geomagic Control X). The linear deviations of 2 standardized points on the scan body used during digitization were automatically calculated on x-, y-, and z-axes. Average deviations were used to define precision, and 1-way analysis of variance and Tukey HSD tests were used for statistical analyses (α = 0.05). Results: Biobased model resin led to higher deviations than dental stone (all axes, P ≤ 0.031) and model resin (yaxis, P = 0.015). Biobased model resin resulted in the lowest precision of implant analog position (P ≤ 0.049). The difference in the positional accuracy of implant analogs of model resin and stone casts was nonsignificant (P ≥ 0.196). Conclusions: Implant analogs in biobased model resin casts mostly had lower positional accuracy, whereas those in model resin and stone casts had similar positional accuracy. Regardless of the material, analogs deviated more towards mesial, while buccal deviations in additively manufactured casts and lingual deviations in stone casts were more prominent

Stereolithography vs. Direct Light Processing for Rapid Manufacturing of Complete Denture Bases: An In Vitro Accuracy Analysis

The topical literature lacks any comparison between stereolithography (SLA) and direct light processing (DLP) printing methods with regard to the accuracy of complete denture base fabrication, thereby utilizing materials certified for this purpose. In order to investigate this aspect, 15 denture bases were printed with SLA and DLP methods using three build angles: 0°, 45° and 90°. The dentures were digitalized using a laboratory scanner (D2000, 3Shape) and analyzed in analyzing software (Geomagic Control X, 3D systems). Differences between 3D datasets were measured using the root mean square (RMS) value for trueness and precision and mean and maximum deviations were obtained for each denture base. The data were statistically analyzed using two-way ANOVA and Tukey's multiple comparison test. A heat map was generated to display the locations of the deviations within the intaglio surface. The overall tendency indicated that SLA denture bases had significantly higher trueness for most build angles compared to DLP (p < 0.001). The 90° build angle may provide the best trueness for both SLA and DLP. With regard to precision, statistically significant differences were found in the build angles only. Higher precision was revealed in the DLP angle of 0° in comparison to the 45° and 90° angles

Marginal gap of printed, milled, and heat-pressed two-piece polyetheretherketone abutments before and after thermal cycling, and their pull-off bond strength after thermal cycling

Abstract Purpose: To evaluate the marginal gap of two-piece polyetheretherketone (PEEK) abutments fabricated with different methods, before and after thermal cycling, while also focusing on their pull-off bond strength. Materials and Methods: A two-piece abutment was virtually designed after digitizing a titanium-base (Ti-base) abutment. This design was used to fabricate printed (P-PEEK), milled (M-PEEK), and heat-pressed (HP-PEEK) PEEK abutments (n = 8). The marginal gaps of all abutments were evaluated under a stereomicroscope (15 points on each side, ×40 magnification), before and after thermal cycling (10,000 cycles, 5◦C–55◦C). Then, all abutments were subjected to a pull-off bond strength test. The marginal gap data were analyzed with a generalized linear model, while the pull-off bond strength data were analyzed with one-way analysis of variance and Tukey tests (α = 0.05). Results: The marginal gaps were affected by the interaction between the fabrication method and aging condition, as well as by the fabrication method and aging condition (p ≤ 0.003). HP-PEEK abutments before thermal cycling had the lowest gap, whereas M-PEEK abutments after thermal cycling mostly had the highest (p ≤ 0.042). Thermal cycling increased the marginal gap of HP-PEEK (p < 0.001). M-PEEK had the lowest and HP-PEEK had the highest pull-off bond strength (p < 0.001). Most of the failures of P-PEEK and M-PEEK abutments were mixed. Conclusions: The tested abutments had marginal gaps below the clinically acceptable threshold of 120 µm, both before and after thermal cycling. HP-PEEK abutments may be more resistant to dislodgment from the Ti-base abutments than P-PEEK and M-PEEK abutments