Fracture Strength of Minimally Prepared Resin Bonded CEREC Inlays

Abstract

SUMMARYPurpose: This study compared the structural integrity and fracture mode of teeth restored with traditionally and minimally prepared resinbonded CAD/CAM inlays fabricated from the same material.Methods: Forty intact maxillary premolars were used and divided into four groups. Two groups were prepared according to a traditional inlay preparation design (2.0 mm occlusal reduction, a 1.5 mm wide proximal box and divergent walls) and two groups were prepared according to a newly proposed minimal preparation design (round shaped cavity with 1.0 mm occlusal reduction, a U-shaped proximal box 1.0 mm wide and parallel walls). Two restorative systems were tested: a composite system comprised of Paradigm MZ100 (3M ESPE) blocks and RelyX Unicem (3M ESPE) resin cement and a ceramic system comprised of ProCAD blocks (IvoclarVivadent) and Variolink II (Ivoclar-Vivadent) resin cement. The inlays were cemented according to the manufacturers' instructions. Each specimen was loaded axially to its occlusal surface at a crosshead speed of 0.5 mm/minute in a universal testing machine until fracture. The fracture load data were analyzed using ANOVA, comparing inlays of the same restorative material. Also, the mode of fracture of the inlays was recorded and analyzed using a non-parametric test (Kruskal-Wallis).Results: In the composite system case, the mean fracture load and SD were 1322 N (±445) for the traditional inlays and 1511 N (±395) for the mini- Clinical RelevanceMinimal preparation designs for inlay restorations are a viable option for CAD/CAM systems (CEREC) and could potentially strengthen the restored tooth. 538Operative Dentistry A mal inlays, while in the ceramic system case, those values were 1135N (±450) for the traditional inlays and 1761 N (±494) for the minimal inlays. Statistical analysis of the results showed that there was no statistically significant difference between the two designs for the composite system, while for the ceramic system, the minimally prepared teeth showed higher mean fracture strength. Non-parametric analysis (KruskalWallis) of the mode of fracture showed that there was no statistically significant difference between traditionally and minimally prepared inlays for both systems (p>.05).Conclusions: Under the conditions of this experimental study, only the ceramic inlays, when prepared with a minimal preparation design, demonstrated a higher fracture strength as compared to the traditionally prepared teeth. Use of the proposed minimal preparation design did not compromise the immediate post-operative structural integrity of teeth restored either with resin composite or ceramic inlays.

Fracture strength of ultrathin occlusal veneer restorations made from CAD/CAM composite or hybrid ceramic materials

“…Inspection of the samples after fracture frequently showed cement to the intaglio of the occlusal veneer as well as to the tooth surface, suggesting failure of the cement. For ceramic materials, it has been known that bonding increases the failure strength [19,20]. This is likely also true for the new ceramic hybrid materials, but additional studies are needed to investigate the bonding capability of these materials and how it affects the strength and failure modes.…”

Marginal Gap, Internal Fit, and Fracture Load of Leucite-Reinforced Ceramic Inlays Fabricated by CEREC inLab and Hot-Pressed Techniques

“…With the use of materials that can be adhesively bonded to the tooth, the application of more minimal preparation designs has also been possible. Minimally prepared resin‐bonded CEREC inlays did not compromise the initial structural integrity of teeth restored either with resin composite or ceramic inlays 10 …”

Fracture Resistance of Teeth Restored With All-ceramic Inlays and Onlays: An In Vitro Study

“…1,9,[24][25][26] Adhesive luting procedures can reinforce teeth and minimize deleterious effects of cusp flexure, thus increasing crown stiffness as an outcome of adhesive effects, cohesive resistance, and stress distribution. 6,15,[26][27][28] In in vitro studies, a number of factors may interfere with resistance to fracture, such as the tooth embedment method, type of load application device, and crosshead speed. [29][30][31][32][33][34] Thus, the experimental methods used for in vitro analyses do not accurately represent real clinical conditions in which failures occur primarily due to fatigue.…”