Comparison of the 3D triple-scan protocol and the impression replica technique for 3-unit tooth-supported fixed dental prostheses

Triple scan evaluation of internal and marginal adaptation of overlays using different restorative materials

OBJECTIVE

Problems in the confection of indirect restorations may increase the marginal and internal gap. This study aimed to quantify the marginal and the internal fit of overlays fabricated with three different materials.

MATERIALS AND METHODS

Standardized cavities were prepared on endodontically treated human third molars and digital impressions were done using an intraoral camera (Trios 3). Restorations were designed (n = 15) and fabricated with three materials: Hybrid ceramic (Cerasmart; GC Corp, EUROPE), high-strength lithium disilicate (GC Initial® LiSi Press; GC Corp, Tokyo, Japan), and zirconia reinforced Lithium Silicate Glass Ceramic (Vita Suprinity; Vita, Germany). Axial, marginal, pulpal, and gingival gaps were calculated by measuring the distance between the restoration and the tooth at several reference points. Two-Way analysis of variance was used for statistical analysis. The significance level was set at α = 0.05.

RESULTS

Mean gap was significantly influenced by the material (p < 0.001), gap localization (p < 0.001), and interaction between the factors (p = 0.002). For all materials, the highest gap was observed at gingival and pulpal surfaces (p ≤ 0.015). LiSi Press achieved the overall lowest values at axial values measurements (p ≤ 0.003).

CONCLUSIONS

The performance of a CAD/CAM system relative to marginal adaptation is influenced by the restorative material used. High-strength lithium disilicate seems to be showed the best marginal adaptation.

CLINICAL SIGNIFICANCE

Marginal and internal adaptation of CAD/CAM restorations could be influenced by the type of material chosen.

Comparison of internal fit of metal-ceramic crowns in CAD/CAM and lost-wax techniques in all fabrication stages through replica weighting, triple scanning, and scanning electron microscope

OBJECTIVES

Restoration fit is one of the prerequisites of clinical durability. It is controversial as to whether computer-assisted design/computer-aided milling (CAD/CAM) or lost-wax fabrication methods result in more fit metal-ceramic crowns. This in-vitro study was conducted to examine the internal fit of porcelain fused to metal crowns fabricated using CAD/CAM and lost-wax techniques during fabrication stages (framework, porcelain, cementation) through digital triple scanning, replica weighting, and observation with electron microscopy.

MATERIAL AND METHODS

Twenty uniform resin dies of prepared first maxillary molars were randomly divided into two groups according to the fabrication technique: lost wax and CAD/CAM. The internal fit was measured in all steps of completing the crowns (framework, porcelain, and cementation) using different methods, including triple scanning, replica weighting, and scanning electron microscopy. The data were statistically analyzed using t test, Pearson, and repeated measures analysis of variance (α = .05).

RESULTS

Triple scanning revealed no difference in the internal fit of CAD/CAM and lost-wax groups in all the fabrication steps (p > .05). The replica weighting method showed no difference between groups in the framework step (p > .05), while the internal fit was significantly better in the CAD/CAM group after porcelain application (p < .05). After cementation, electron microscopy measurements showed no difference between CAD/CAM and lost wax groups (p > .05). The Pearson correlation test showed no significant correlation between electron microscopy, replica weighing, and triple scanning methods (p > .05).

CONCLUSION

According to scanning electron microscopy as the superior evaluation method, the internal fit of cobalt-chrome PFM crown of both CAD/CAM and lost wax groups was within the acceptable clinical range and there was no significant difference between them. Triple scanning revealed no difference in the internal fit of framework and porcelain steps but a better fit after cementation. According to replica weighting, the internal fit in the porcelain step was higher than the framework.

A systematic review on the accuracy of zirconia crowns and fixed dental prostheses

Purpose

The aim of this study was to review the fit and assess the accuracy of tooth-supported single and multi-unit zirconia fixed dental prostheses.

Background

The fit of zirconia restorations has been reported in several studies, but the accuracy of the manufacturing process is seldom discussed or used when drawing conclusions on the fit.

Materials and methods

A literature search of articles published in PubMed between 2 March 2013 and 1 February 2018 was performed using clearly defined inclusion and exclusion criteria. 841 articles were found and 767 were excluded after screening the title and abstract. After full-text analysis another 60 articles were excluded which left 14 articles to be included for data extraction. Fit was the mean of distances reported in the studies and accuracy was the fit minus the pre-set spacer

Results

For marginal gap of single crowns and multi-unit FDPs combined, the fit was 83 μm and the accuracy was 59 μm. The internal gap fit was 111 μm and the accuracy 61 μm. For the total gap, the fit was 101 μm, and the accuracy of the zirconia restorations was 53 μm.

Conclusions

Within the limitations of the present systematic review the fit of zirconia single crowns and multi-unit FDPs may be regarded as clinically acceptable, and the accuracy of the manufacturing of zirconia is ∼60 μm for marginal, internal, and total gap. Also, digital impressions seem to be associated with a smaller gap value.