Comparative evaluation of the internal and marginal adaptation of 1-piece endodontic crowns fabricated by additive,...

One-piece endodontic crowns can be fabricated using different techniques, and the introduction of definitive 3-dimensionally (3D) printed resin materials has expanded digital manufacturing options. Because internal and marginal adaptation are critical for long-term success, it is essential to evaluate the performance of different fabrication methods. However, comparative studies assessing these techniques-particularly using complementary adaptation-measurement approaches-remain limited.

The purpose of this in vitro study was to evaluate the internal and marginal adaptation of 1-piece endodontic crown restorations fabricated by additive, subtractive, and conventional techniques using silicone replica and modified triple-scan methods, including the assessment of volumetric cement space and marginal deviation.

Thirty-six mandibular molar 1-piece endodontic crowns were fabricated using 3 techniques (n=12 per group): additive manufacturing (VarseoSmile TriniQ; BEGO) using a 3D printer (MAX 2; Asiga), subtractive manufacturing (Cerasmart 270; GC) using a milling machine (CEREC MC XL; Sirona), and the conventional technique (Gradia Plus; GC) on gypsum dies obtained from A-type silicone impressions. Preparations were scanned with an intraoral scanner (TRIOS 4; 3Shape A/S) and restorations digitally designed using a computer-aided design (CAD) software program (DentalCAD; exocad GmbH). Adaptation was assessed using 2 methods. The silicone replica technique involved sectioning and stereomicroscopic evaluation at 60 measurement points per specimen across the pulpal floor, axial wall, and marginal areas. The modified triple-scan protocol digitally superimposed restoration, abutment, and assembly scans to calculate internal and marginal discrepancies, cement-space volume, and marginal deviation (Geomagic Control X; Oqton). Normality was assessed using the Kolmogorov-Smirnov and Shapiro-Wilk tests. Depending on the data distribution, groups were compared using analysis of variance (ANOVA) with the Tukey honestly significant difference (HSD) or Kruskal-Wallis with Dunn post hoc tests (α=.05).

Significant differences were observed among the evaluated groups (P<.05). The conventional indirect composite group demonstrated favorable internal and marginal gap values, whereas the subtractively milled hybrid composite group exhibited higher discrepancies under the conditions tested. Absolute marginal discrepancy (AMD) type marginal deviation values were highest for the conventional indirect composite resin group. Across all groups, the pulpal floor showed the largest gaps, while the axial wall demonstrated the smallest discrepancies. All measured internal and marginal gap values remained within clinically acceptable limits.

Adaptation varied among all the evaluated material groups. Within the limitations of this study, 1-piece endodontic crowns fabricated using additive, subtractive, and conventional workflows demonstrated clinically acceptable adaptation.