Accuracy of digitally fabricated partial coverage ceramic restorations using conventional impression and intraoral scanners

Background The purpose of this in-vitro study was to evaluate the accuracy of digitally fabricated partial coverage ceramic restorations with two designs using conventional impression and intraoral scanners. Methods Forty-eight sound human maxillary first premolars with homogenous dimensions were partitioned into two equal groups (n = 24) based on the overlay preparation design; Group (1): teeth prepared with thin conventional design (D1), Group (2): teeth prepared with MODFL (mesial-occlusal-distal-facial-lingual) design (D2). Based on the method of taking impression, each group was subdivided into 3 subgroups (n = 8); Subgroup (C): conventional impression using polyvinyl siloxane, Subgroup (SC1): scanner type 1 TRIOS 5 (3Shape) and Subgroup (SC2): scanner type 2 Medit i900 (Medit). All fabricated restorations were cemented into corresponding teeth utilizing self-adhesive resin cement (Multilink Speed). All specimens were thermo-cycled for 5000 cycles in a water bath between 5 °C and 55 °C after that marginal adaptation test was done using scan electron microscope. The threshold for statistical significance was established at p ≤ 0.05. Results SC1 demonstrated the lowest mean marginal gap in D1and D2. The Tukey post-hoc multiple comparison test indicated that statistically significant changes in marginal adaption were mostly related to restorations produced using the SC1, especially in D2. Design 2 overlays generated with SC1(D2SC1) exhibited markedly reduced marginal gap values in comparison to those produced by the conventional impression technique (D2C) ( p = 0.017) and in relation to D1SC2 ( p = 0.007), as well as D1 created using the conventional impression method (D1C) ( p = 0.034). Conversely, the majority of pairwise comparisons between conventional impressions(C) and SC2, irrespective of design type, were not statistically significant. Conclusions Digital impressions improved marginal integrity of overlay restorations and offered a clinically effective alternative to conventional silicone impressions within a digital workflow, the TRIOS 5 (3Shape) scanner demonstrated improved marginal adaptation across both preparation designs compared to the other techniques. This may be attributed to its high trueness and precision, as well as its confocal microscopy-based image acquisition technology, with the effect becoming more evident in complex designs.