Self‐Adhesive Resin Cements—Part I

A recent Medline search revealed 214 publications related to the search term “self‐adhesive resin cements.” The Journal published a Critical Appraisal on these materials by Burgess and colleagues in late 2010 (J Esthet Restor Dent 2010;22:412–9). One hundred fifty‐eight of those were published in 2009 or later, so the knowledge base on this subject is growing rapidly. With that in mind, we thought it would be helpful to provide an update. The update will be presented in two parts. Here in Part I, the specific topics addressed are bonding to tooth structure, bonding to zirconia ceramics, and effects of curing mode.     

Self‐Adhesive Resin Cement for Luting Glass Fiber Posts

Self‐adhesive resin cements are gaining increasing popularity in dentistry because they simplify the cementation protocol by eliminating the etching, priming, and bonding steps. Due to the scarce literature on the clinical performance of glass fiber posts luted using different adhesive strategies, clinicians have difficulty in selecting the most appropriate resin cement system. This Critical Appraisal will review in vitro and clinical studies regarding the luting of fiber posts with self‐adhesive materials.     

Effect of Dentin Surface Modification on the Microtensile Bond Strength of Self‐Adhesive Resin Cements

Purpose: To explore the potential to modify human dentin surface as a means of improving the microtensile bond strength (μTBS) of resin cement to dentin. Materials and Methods: Sound human molars were collected, and their occlusal surfaces were ground flat to expose polished dentin. Indirect composite resin cylinders were cemented to the teeth with RelyX Unicem or G‐Cem self‐adhesive cements following dentin surface treatments: 6.5% grape‐seed extract, 5% glutaraldehyde, or 25% polyacrylic acid and control (no pretreatment). After 24 hours, the teeth were sectioned into beams to produce a cross‐sectional area of 1.0 mm². Specimens of each group (n = 25) were individually mounted on a jig and placed on a tensile testing machine. A tensile force was applied to failure at a 1 mm/min crosshead speed. Results: The use of polyacrylic acid on dentin prior to cementation with RelyX Unicem resulted in a statistically significant increase in μTBS compared to the control group (p= 0.0282). Polyacrylic acid (p= 0.0016) or glutaraldehyde (p= 0.0043) resulted in a statistically significant increase in μTBS of G‐Cem to dentin when compared to the control group. Treatment with grape‐seed extract did not result in a statistically significant increase in μTBS for either cement (p > 0.05). Conclusions: Priming dentin surfaces prior to the use of self‐adhesive resin cements may be a promising means of improving μTBS. In addition, it was concluded that the results of this study are material dependent as well as being dependent of the type of dentin primer.     

Microleakage of Porcelain and Composite Machined Crowns Cemented with Self‐Adhesive or Conventional Resin Cement

Purpose: Resistance of machined crowns to microleakage when cemented with new self‐adhesive cements has not been fully investigated. This study evaluated microleakage of machined crowns milled from porcelain and composite blocks and bonded to teeth with self‐adhesive and conventional resin cement. Materials and Methods: Thirty‐two freshly extracted premolars of similar shape and size were sterilized and mounted in resin blocks. Teeth received standard crown preparations with 1‐mm circumferential shoulder finish line, flat occlusal surface reduced by 2 mm, and ideal angle of convergence. Prepared teeth were divided into two equal groups and assigned to either porcelain (Vita Mark II, Vident) or composite (Paradigm MZ100, 3M ESPE) blocks for crown fabrication. Optical impressions were captured for each tooth with the intraoral camera of a CEREC 3D machine. Crowns were designed and milled from both materials. Each group was then subdivided into two subgroups (n = 8) according to cement used (self‐adhesive resin cement, RelyX Unicem, 3M ESPE or resin cement with self‐etching adhesive, Panavia F 2.0, Kuraray). Following seating, a 5‐kg weight was applied on the occlusal surface of the crown for 5 minutes. Specimens were then stored in water at 37°C for 24 hours. Specimens were thermocycled for 3000 cycles between 5°C and 55°C, then coated with nail varnish and immersed in a 2.0% basic red fuchsine dye solution for 24 hours. Teeth were then rinsed and sectioned mesiodistally and assessed under magnification for microleakage. A five‐point scale was used to score degree of microleakage. Data were statistically analyzed with 2‐way ANOVA and Kruskal‐Wallis nonparametric test. Results: Crown material had no significant effect on microleakage (p= 0.67); however, cement type had a significant effect (p < 0.0001), with Panavia F 2.0 resulting in lower microleakage scores than RelyX Unicem. Conclusions: Compared to the self‐adhesive cement, the resin cement with separate primer/bonding agent resulted in significantly lower microleakage scores, irrespective of crown material.     

Dental Amalgam Update—Part II: Biological Effects

Dental amalgam restorations have been controversial for over 150 years. In Part I of this Critical Appraisal, the clinical efficacy of dental amalgam was updated. Here in Part II, the biological effects of dental amalgam are addressed.     

光固化与化学固化复合树脂黏接正畸托槽的对比研究

目的对比光固化、化学固化复合树脂黏接正畸托槽的抗剪强度和牙釉质脱矿程度。方法20颗离体前磨牙随机分为光固化复合树脂组(1)和化学固化复合树脂组(2),检测抗剪黏接强度;将116例正畸患者左右侧上前牙随机分为2组,试验组用光固化复合树脂黏接托槽,对照组用化学固化复合树脂黏接托槽,对比正畸治疗结束后两组牙釉质脱矿的差异。结果2组黏接抗剪强度为:(1)组(17.45±7.06)MPa,(2)组(13.02±5.38)MPa,两组间有差异(P<0.05)。试验组与对照组正畸治疗结束后牙釉质脱矿程度有显著差异(P<0.01)。结论光固化型复合树脂的抗剪强度优于化学固化型。光固化复合树脂黏接正畸托槽能减少正畸治疗中牙釉质脱矿。     

Bulk‐Fill Composites,Part II

This is the second part of a Critical Appraisal that reviews some of the recent research on bulk‐ fill composite resins.     

Bond Strength of Resin Cements to Co‐Cr and Ni‐Cr Metal Alloys Using Adhesive Primers

Purpose: The aim of this study was to evaluate the effectiveness of adhesive primers (APs) applied to Co‐Cr and Ni‐Cr metal alloys on the bond strength of resin cements to alloys. Materials and Methods: Eight cementing systems were evaluated, consisting of four resin cements (Bistite II DC, LinkMax, Panavia F 2.0, RelyX Unicem) with or without their respective APs (Metaltite, Metal Primer II, Alloy Primer, Ceramic Primer). The two types of dental alloys (Co‐Cr, Ni‐Cr) were cast in plate specimens (10 × 5 × 1 mm³) from resin patterns. After casting, the plates were sandblasted with aluminum oxide (100 μm) and randomly divided into eight groups (n = 6). Each surface to be bonded was treated with one of eight cementing systems. Three resin cement cylinders (0.5 mm high, 0.75 mm diameter) were built on each bonded metal alloy surface, using a Tygon tubing mold. After water storage for 24 hours, specimens were subjected to micro‐shear testing. Data were statistically analyzed by two‐way ANOVA and Tukey's studentized range test. Results: The application of Metal Primer II resulted in a significantly higher bond strength for LinkMax resin cement when applied in both metal alloys. In general, the cementing systems had higher bond strengths in Co‐Cr alloy than in Ni‐Cr. Conclusions: The use of AP between alloy metal surfaces and resin cements did not increase the bond strength for most cementing systems evaluated.