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The role of nanofillers in reducing the microleakage of dental composite resins has not been previously investigated. So this study was designed to evaluate microleakage of nanofilled composite resin in comparison to the conventional hybrid composite. Twenty extracted sound molars were selected. Class II cavities were prepared. All cavities were etched (enamel and dentin) with 37% phosphoric acid. Dentin bonding agents were applied to etched tooth surfaces and restored with nanofilled and hybrid composite restorative materials. The restored teeth were thermocycled. Specimens were immersed in 2% methylene blue dye, sectioned along the mesio-distal direction; dye penetration of occlusal and gingival margins of each section was evaluated using a stereo-microscope. No significant difference was found between the microleakage of nanofilled and hybrid composite restorations at occlusal / enamel and at gingival / dentin margins. Also, there were no significant differences for nanofilled composite restorations at occlusal / enamel margins and gingival / dentin margins. On the other hand, there were a significant differences for hybrid composite restorations at occlusal / enamel margins and gingival / dentin margins

Purpose: The objective of this study was to evaluate the retentive strength of singleunit crowns with 10• and 26• taper angles cemented using two surface conditioning methods. Materials and Methods: Thirty-two freshly extracted sound human molars were divided into two groups (n = 16) and prepared in a standardized manner with 10• and 26• taper angles. All-ceramic (IPS e.max Press) single crowns were fabricated for the prepared teeth. The crowns were then subdivided into two groups (n = 8), according to type of surface conditioning for the intaglio surfaces. Half the groups were HF acid etched and silanized, and the other half were conditioned with tribochemical silica coating and silanization. The crowns were cemented using adhesive cement (Panavia F 2.0). Retentive strength was measured in a universal testing machine. Results: No significant difference was found between the mean retention forces for both 10• and 26• taper angles when the crowns were conditioned either with silica coating (613 ± 190 N and 525 ± 90 N, respectively), or with hydrofluoric (HF) acid etching and silanization (550 ± 110 N and 490 ± 130 N for 10• and 26• , respectively) (p = 0.32). Conclusion: Neither the surface conditioning type, nor the taper angle affected the retentive strength of IPS e.max Press single-unit crowns when cemented adhesively. Since silica coating and silanization did not show significant differences from HF acid gel and silanization, the former can be preferred for conditioning intaglio surfaces of glass ceramic crowns to avoid the use of the hazardous compound HF acid gel chairside.All-ceramics became the common material of choice for singleunit crowns or multiple-unit fixed partial dentures (FPD) due to their esthetic appeal as opposed to their metal-ceramic counterparts.1 Strong and reliable adhesion could be provided by resinbased luting systems.2,3 Recently, heat-pressed all-ceramic materials that contain lithium disilicate as a major crystalline phase have become available. One such system is IPS e.max Press, heat-pressed between 890 and 1120• C, with which single crowns or multiple-unit FPDs can be fabricated for both the anterior and posterior region of the mouth. The lithium disilicate-containing ceramics have sufficient flexural strength (350 to 400 MPa) and fracture toughness (3.2 MPa.m 1/2 ), extending their range of clinical applications. 4 With heat-pressed ceramics, large pores caused by non-uniform mixing, extensive grain growth, or secondary crystallization that occurs often during sintering can be avoided.5 Longevity of all-ceramic FPDs mainly rely on adequate adhesion of the resin-based luting cements both to the tooth tissues and the ceramic surface. 4 Adhesion of luting cements increases the fracture resistance of the tooth and the restoration itself. It also increases the retention of the restoration and minimizes microleakage that may play a role in the biological success of the restoration. 2,6,7 Predictable adhesion between resin luting cements and glassy matrix ceramics is usually c...