Influence of glazing and aging on the marginal, axial, axio-occlusal, and occlusal fit of 3-unit monolithic zirconia restorations fabricated using additive and subtractive techniques.

STATEMENT OF PROBLEM: Studies are sparse on how glazing and aging influence the fit of additively fabricated monolithic zirconia restorations. PURPOSE: The purpose of this in vitro study was to assess the effect of glazing and aging on the fit of 3-unit monolithic zirconia restorations fabricated using different techniques. MATERIAL AND METHODS: A total of 32 monolithic zirconia restorations were fabricated for a typodont model by using 4 distinct techniques (subtractive fabrication [SF], stereolithography [SLA], digital light processing [DLP], and lithography-based ceramic manufacturing [LCM]). The silicone replica approach was adopted to measure the discrepancy values for premolar and molar abutments after sintering, glazing, and 1 year of aging. The silicone replicas were sliced into mesiodistal and buccopalatal cross-sections, and digital micrographs of the cross-sections were made with a ×80 stereomicroscope. An inherent measuring program was run to record the discrepancy values (µm). Repeated-measures 2-way ANOVAs with the Bonferroni post hoc test were used to statistically analyze the acquired data. (α=.05). RESULTS: From the repeated measures 2-way ANOVAs, both the glazing×fabrication technique and the aging×fabrication technique interactions were not statistically significant (P>.05). Glazing significantly influenced premolar abutment marginal (P=.022) and occlusal (P=.007) discrepancy values, as well as molar abutment marginal discrepancy values (P=.047). Aging had a statistically significant effect on premolar abutment marginal (P=.008) and occlusal (P=.011) discrepancy values, as well as molar abutment occlusal discrepancy values (P=.039). In both the glazing and aging data, for all areas of interest, statistically significant differences were detected among the fabrication techniques (P<.05). The LCM group had the lowest discrepancy values, followed by the SLA, SF, and DLP groups. CONCLUSIONS: The LCM and SLA groups outperformed the other groups in terms of fit accuracy. The glazing and aging procedures altered the discrepancy values. The marginal discrepancy values of all groups were below the threshold of clinical acceptability (<120 µm).

Effect of angulation on the 3D trueness of conventional and digital implant impressions for multi-unit restorations.

PURPOSE: The study aimed to determine the influence of implant angulation on the trueness of multi-unit implant impressions taken through different techniques and strategies. MATERIALS AND METHODS: As reference models, three partially edentulous mandibular models (Model 1: No angulation; Model 2: No angulation for #33, 15-degree distal angulation for #35 and #37; Model 3: No angulation for #33, 25-degree distal angulation for #35 and #37) were created by modifying the angulations of implant analogues. Using a lab scanner, these reference models were scanned. The obtained data were preserved and utilized as virtual references. Three intraoral scanning (IOS) strategies: IOS-Omnicam, ISO-Quadrant, and IOS-Consecutive, as well as two traaditional techniques: splinted open tray (OT) and closed tray (CT), were used to create impressions from each reference model. The best-fit alignment approach was used to sequentially superimpose the reference and test scan data. Computations and statistical analysis of angular (AD), linear (LD), and 3D deviations (RMS) were performed. RESULTS: Model type, impression technique, as well as interaction factor, all demonstrated a significant influence on AD and LD values for all implant locations (P < .05). The Model 1 and SOT techniques displayed the lowest mean AD and LD values across all implant locations. When considering interaction factors, CT-Model 3 and SOT-Model 1 exhibited the highest and lowest mean AD and LD values, respectively. Model type, impression technique, and interaction factor all revealed significant effects on RMS values (P ≤ .001). CT-Model 3 and SOT-Model 1 presented the highest and lowest mean RMS values, respectively. CONCLUSION: Splinted-OT and IOS-Omnicam are recommended for multi-unit implant impressions to enhance trueness, potentially benefiting subsequent manufacturing stages.