Effect of deep marginal elevation on marginal adaptation and fracture resistance in endodontically treated teeth restored with endocrowns constructed by two different CAD/CAM ceramics: an in-vitro study

Abstract

Aim: To evaluate the effect of deep marginal elevation on the marginal adaptation and fracture resistance in endodontically treated teeth restored with endocrowns constructed by two CAD/CAM ceramics in an in-vitro model. Material and methods: twenty four human, intact freshly extracted mandibular first molars were endodontically treated and mounted in an upright position in a standard plastic ring filled with acrylic resin 4mm apical to the CEJ. A standard endocrowns preparation was performed with a butt- joint occlusal margin for all specimens and a proximal box preparation was done on the mesial surfaces. The specimens were then equally divided in to two groups (n=12) according to the material used in construction group (M) using IPS e.max CAD ceramic blocks and group (V) using Vita Enamic ceramic blocks; then further divided in to two subgroups (n=6) according to the application of a mesial marginal elevation or not into (ME, VE) with marginal elevation and groups (MN, VN) without marginal elevation. All endocrowns were cemented to the corresponding preparation using dual cured self- adhesive resin cement (RelyX, Unicem). All specimens were thermally aged with 10000 cycle in water bath between 5˚C- 55˚C. The marginal adaptation was evaluated using stereomicroscope (40 ×) at 5 predetermined points on the mesial margin for each specimen and mean gap measurement was calculated. All specimens were then subjected to fracture resistance test via universal testing machine. The collected data was recorded, tabulated and transferred for statistical analysis. Results: Vita Enamic with deep marginal elevation (VE) recorded the lowest marginal gap measurements at (69.3 µm)which is significantly lower than all tested subgroups (P < 0.001), while IPS e.max CAD with deep marginal elevation (ME) subgroup showed significantly higher fracture resistance (1478.2N) than all tested subgroups (P< 0.001). Conclusion: Deep marginal elevation enhances both marginal adaptation and fracture resistance of IPS e.max CAD and Vita Enamic. IPS e.max CAD has higher fracture resistance while Vita Enamic has better marginal adaptation.