External gap progression after cyclic fatigue of adhesive overlays and crowns made with high translucency zirconia or lithium silicate

Abstract

Objectives: To evaluate three-dimensional external gap progression after chewing simulation of high translucency zirconia (HTZ) and zirconia-reinforced lithium silicate (ZLS) applied on endodontically treated teeth with different preparation designs.

Materials and method: Endodontically treated molars were prepared with low-retentive (adhesive overlay) and high-retentive (full crown) designs above cementum-enamel junction and restored with HTZ and ZLS. Micro-computed tomography analysis was assessed before and after chewing simulation to evaluate three-dimensionally the external gap progression. Results were statistically analyzed with two-way ANOVA and post-hoc Tukey test.

Results: High-retentive preparation design had a significantly inferior gap progression compared to the overlay preparation (p < 0.01); ZLS exhibited a significant inferior gap progression compared to HTZ (p < 0.01).

Conclusions: High-retentive preparations restored with ZLS seem to better perform in maintaining the sealing of the external margin after cyclic fatigue.

Clinical significance: The clinician should pay attention to the proper combination of preparation designs and ceramic material selection for an endodontically treated molar restoration. HTZ seems to perform worse than lithium silicate in terms of marginal sealing, still showing lacks in resistance to cyclic fatigue when adhesive preparations are performed.

Keywords: crown; endodontically treated teeth; external gap; high-translucency zirconia; micro-CT; overlay.

FIGURE 1

Random samples transversal sections of a low‐retentive design (Fig. 1A) and high‐retentive design (Fig. 1B). Both the restorations were performed above the CEJ level, as highlighted in Fig. 1B

FIGURE 2

Random sample external gap analysis (ADH, ZLS) in stages A–D. Figure A presents a random cross‐section with external gaps highlighted. Figure B is a magnification of Figure A, showing in red the pixels corresponding to the external gap used in the analysis. Figure C shows a 3D rendering (Geomagic Studio 12, 3D Systems) of the tooth‐restoration complex (in blue) and the analyzed gap (in yellow). Figure D presents the analyzed gap in yellow

FIGURE 3

Random sample (ADH, HTZ) external gap progression analysis. Figure A presents the baseline gap in light blue aligned with the transparent blue tooth‐restoration complex. It is worth mentioning that even if a gap is reported throughout the whole interface, it is extremely thin, making its total volume almost irrelevant. Figure (B) presents the same sample gap after fatigue simulation in yellow, with red circles indicating some of the area that showed a significant gap progression. Figure (C) presents the superimposition of the baseline (light blue) on the final gap (yellow), with the same highlights presented in Figure B. Figure (D) presents a detailed view of Figure C for better understanding