Microleakage and Fracture Resistance of "Infinity Edge" and Cusp Reduction Preparation Designs for Moderate-sized Class II Composites.

Aim: This study aimed to evaluate the marginal microleakage and maximum occlusal fracture loads and fracture modes of two novel class II preparation designs, "infinity edge" and the "2.5 mm cusp reduction" preparations as compared to a traditional class II preparation without cuspal involvement.

Materials And Methods: Thirty extracted human mandibular molars were prepared for moderate-sized class II restorations with extensions into all occlusal grooves. Of these, ten class II preparations served as control. Ten were modified for a 2.5 mm even reduction of the cusps adjacent to the interproximal box. An additional 10 preparations were modified with an "infinity edge" bevel on the interproximal and occlusal portions. All teeth were restored utilizing a flowable bulk-fill composite in the apical portion of the interproximal box and 2-4 mm of heated bulk-fill composite in one increment for the remainder. All groups were cyclic loaded and thermocycled, then imaged with microcomputed tomography (µCT) before and after infiltration with a silver nitrate solution. Images were subtracted to obtain volumetric measurements of microleakage and reported as a percentage of the total volume from the apical extent of the proximal box. All groups were loaded to failure and fracture load and mode were recorded.

Results: No significant differences were found in microleakage volume as a percentage of total tooth volume; however, the "infinity edge" group had significantly greater microleakage in the proximal box compared to the traditional class II group. No significant differences were found in fracture load or mode between the groups.

Conclusion: Traditional class II, 2.5 mm cuspal reduction, and "infinity edge" preparation designs have similar fracture loads as well as volumes of microleakage; however, an "infinity edge" preparation has a higher ratio of microleakage in the proximal box.

Clinical Significance: Clinicians should carefully consider the use of "infinity edge" margins, particularly on dentin in the apical extent of the proximal box. How to cite this article: Watson JC, Lien W, Raimondi JC, . Microleakage and Fracture Resistance of "Infinity Edge" and Cusp Reduction Preparation Designs for Moderate-sized Class II Composites. J Contemp Dent Pract 2024;25(1):3-9.