Leakage Pathway of Class V Cavities Restored with Different Flowable Resin Composite Restorations.

This study investigated the leakage pathway of facial and lingual Class V cavities restored with different flowable resin composites bonded with one bonding agent by examining the resin/dentin interface. Forty Class V cavities were etched with 37% phosphoric acid gel; Single Bond dental adhesive was applied, then the cavities were randomly divided into four groups (n=10). Three groups were restored with one of three flowable resin composites (Grandio Flow, Filtek Flow and Admira Flow). The fourth group was restored with Z250 (hybrid resin composite) to serve as a control. The specimens were then placed in 50% w/v silver nitrate solution for 24 hours and immersed in a photodeveloping solution for eight hours. Thereafter, the specimens were sectioned bucco-lingually, polished, mounted on stubs, gold sputter coated and examined by scanning electron microscope. Silver particle penetration length with and without gap formation was measured directly on the scanning electron microscope monitor and calculated as a percentage of the total length of the cut dentin surface that was penetrated by silver nitrate. The data were analyzed with one-way ANOVA and Tukey HSD test. The groups restored with Filtek Flow and Admira Flow showed a microleakage pattern where silver nitrate penetration was observed with gap formation at the tooth/restoration interface and Filtek Flow recorded significantly higher leakage than Admira Flow. Grandio Flow showed similar marginal adaptation to Z250 resin composite with no gap formation at the interface. However, silver ions had penetrated beneath the resin-impregnated layer in cavities restored with Grandio Flow and Z250, indicating nanoleakage occurred. This study suggests that volumetric shrinkage in resin composites remains a problem. Although some new technologies are trying to solve the problem of composite shrinkage, the bonding system used in this study did not achieve perfect sealing at the restoration/dentin interface. This might affect durability of the bond to dentin.King Saud Universit

Effect of seating forces on cement-ceramic adhesion in microtensile bond tests

OBJECTIVES: The aim of this study was to evaluate the effect of different seating forces during cementation in cement-ceramic microtensile bond strength (μTBS). MATERIALS AND METHODS: Forty-five blocks (5 × 5 × 4 mm(3)) of a glass-infiltrated alumina-based ceramic (In-Ceram Alumina) were fabricated according to the manufacturer's instructions and duplicated in resin composite. Ceramic surfaces were polished, cleaned for 10 min in an ultrasonic bath, silica coated using a laboratory type of air abrasion device, and silanized. Each treated ceramic block was then randomly assigned to five groups (n = 9) and cemented to a composite block under five seating forces (10 g, 50 g, 100 g, 500 g, and 750 g) using a dual-cured resin cement (Panavia F). The ceramic-cement-composite assemblies were cut under coolant water to obtain bar specimens (1 mm × 0.8 mm(2)). The μTBS tests were performed in a universal testing machine (1 mm/min). The mean bond strengths values were statistically analyzed using one-way ANOVA (α ≤ 0.05). RESULTS: Different seating forces resulted in no significant difference in the μTBS results ranging between 13.1 ± 4.7 and 18.8 ± 2.1 MPa (p = 0.13) and no significant differences among cement thickness. CONCLUSIONS: Excessive seating forces during cementation seem not to affect the μTBS results. CLINICAL RELEVANCE: Excessive forces during the seating of single all-ceramic restorations cementation seem to display the same tensile bond strength to the resin cement

Luting, cements and bonding

This chapter will emphasise the need to:Appreciate why conventionally cemented extra-coronal restorations require preparations with retentive axial walls (minimally tapered and sufficiently long)Avoid creating a thick lute between a preparation and the inner surface of a restorationEnsure your technician facilitates seating of the restoration by die spacing, venting the crown or programming a lute space using CAD/CAMBe familiar with surface treatments which can enhance resin bonding to tooth structure and restorative materialsBe familiar with resin bonding agents, their uses and limitationsChoose a luting agent which is appropriate to the situatio