Effect of different polishing methods on roughness and color stability of air-abraded restorative materials after artificial accelerated aging.

PURPOSE: To evaluate the effect of air abrasion and polishing procedures on roughness and color stability of ceramic and composite materials after artificial accelerated aging. METHODS: In this study, six restorative materials were tested: feldspathic ceramic (CEREC Blocks), glass ceramic (IPS e.max CAD), resin-based hybrid ceramic (Cerasmart), microhybrid composite (Charisma Classic), nanohybrid composite (Charisma Diamond) and nanoceramic composite (CeramXOne). Forty square-shaped composite specimens were fabricated from each composite and CAD-CAM ceramic material. Initial surface roughness measurements were performed using a profilometer and color measurements of each specimen with a spectrophotometer. Ten control specimens for each group did not receive air abrasion. The other specimens were treated by an air abrasion device and then were randomly divided into three subgroups of 10 specimens (n= 10). After air abrasion, 10 specimens of each group did not receive polishing (Air abrasion group) and others were repolished with Sof-Lex kit (Sof-Lex group) or a rubber kit (Rubber group). Surface roughness and color measurements were repeated before and after 300 hours of artificial accelerated aging (AAA). The univariate test and then three-way ANOVA and two-way ANOVA were performed for comparison of groups (α= 0.05). RESULTS: The univariate statistical analysis revealed that the restorative materials were differently affected after air abrasion, polishing methods and AAA (P< 0.001). Three-way ANOVA showed that the surface roughness of the restorative materials increased after air abrasion and AAA (P< 0.001). Two-way ANOVA showed statistically significant differences between color changes of ceramic (CEREC and IPS e.max CAD) and composite based restorative materials (P< 0.001). CLINICAL SIGNIFICANCE: Clinicians should be aware that air abrasion at a specified power and time significantly changes the surface roughness of the materials except for CEREC. Additionally, polishing procedures (Sof-Lex, Rubber) did not significantly reduce the surface roughness of the ceramic groups. After air abrasion, depending on the material type used clinically, restorations should be repolished to reduce roughness and ensure color stability.

Evaluation of Implant Impression Accuracy Using Different Trays and Techniques With a 3D Superimposition Method.

PURPOSE: The purpose of this study was to evaluate the dimensional accuracy of implant impressions obtained using different tray types and techniques. MATERIALS AND METHODS: A partially dentate maxillary Kennedy Class II model was created as a reference model through three-dimensional (3D) printing. Then, 4.3-mm diameter implant analogs were placed at the first premolar, first molar, and second molar regions. Five types of trays-metal and plastic stock trays and custom trays fabricated using liquid crystal display (LCD), fused deposition modeling (FDM), and urethane dimethacrylate (UDMA) resin-were used to create impressions. Open- and closed-tray techniques were also compared. In total, 150 impressions were obtained. The reference model and impressions were scanned using a laboratory scanner. The positional and angular deviations of implants with different tray types and techniques were evaluated using the superimposition method. RESULTS: There was no statistically significant difference (P>0.05) between the impression accuracy with the different tray types and impression techniques. The angular deviations with plastic and UDMA trays were greater than those with metal, FDM, and LCD trays. Angular deviation at the second molar by using closed trays was greater than that using open plastic trays. The highest and lowest positional deviation were observed at the first molar implant with an open plastic tray impression (mean: 62.46 ± standard deviation: 28.54 µm) and a closed LCD tray impression (36.59 ± 29.93 µm). The greatest angular deviation was observed with an open FDM tray impression at the first premolar implant (0.067 ± 0.024°), and the lowest angular deviation was observed with a closed metal stock tray impression at the second molar implant (0.039 ± 0.025°). Statistical differences were detected using Mann-Whitney U tests for pair groups and the Kruskal- Wallis test for groups with more than three comparisons (P>0.05). CONCLUSION: Plastic and metal stock trays or conventional and 3D-printed custom trays can be used to obtain implant impressions for maxillary partially edentulous arches with similar dimensional accuracy. The five tray types and two techniques may be safely used to obtain impressions of partially edentulous maxillary arches with three implants.