Shear Bond Strength of Four Resin Cements Used to Lute Ceramic Core Material to Human Dentin

Purpose: This study evaluated the effect of four resin cements on the shear bond strength of a ceramic core material to dentin. Materials and Methods: One hundred twenty molar teeth were embedded in a self‐curing acrylic resin. The occlusal third of the crowns were sectioned under water cooling. All specimens were randomly divided into four groups of 30 teeth each according to the resin cement used. One hundred twenty cylindrical‐shaped, 2.7‐mm wide, 3‐mm high ceramic core materials were heat‐pressed. The core cylinders were then luted with one of the four resin systems to dentin (Super‐Bond C&B, Chemiace II, Variolink II, and Panavia F). Half of the specimens (n = 15) were tested after 24 hours; the other half (n = 15) were stored in distilled water at 37°C for 1 day and then thermocycled 1000 times between 5°C and 55°C prior to testing. Shear bond strength of each specimen was measured using a universal testing machine at a crosshead speed of 1 mm/min. The bond strength values were calculated in MPa, and the results were statistically analyzed using a two‐way analysis of variance (ANOVA) and Tukey HSD tests. Results: The shear bond strength varied significantly depending on the resin cement used (p < 0.05). The differences in the bond strengths after thermocycling were not remarkable as compared with the corresponding prethermal cycling groups (p > 0.05). Significant interactions were present between resin cement and thermocycling (p < 0.05). After 24 hours, the specimens luted with Variolink II (5.3 ± 2.2 MPa) showed the highest shear bond strength, whereas the specimens luted with Chemiace II (1.6 ± 0.4 MPa) showed the lowest. After thermocycling, the bond strength values of specimens luted with Chemiace II (1.1 ± 0.1 MPa) and Super‐Bond C&B (1.7 ± 0.4 MPa) decreased; however, this was not statistically significant (p > 0.05). The increase in the shear bond strength values in the Panavia F (4.5 ± 0.7 MPa) and Variolink II (5.5 ± 2.1 MPa) groups after thermocycling was also not statistically significant (p > 0.05). Conclusion: Variolink II and Panavia F systems showed higher shear bond strength values than Chemiace II and Super‐Bond C&B. They can be recommended for luting ceramic cores to dentin surfaces.     

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.     

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.     

6种复合树脂粘接剂与纤维增强型复合树脂根管桩的粘接强度研究

目的评价6种复合树脂粘接剂与带有半渗透网状复合基质的纤维增强型复合树脂根管桩的粘接强度。方法实验分为6组,分别为纤维增强型复合树脂根管桩和6种复合树脂粘接剂模块,每组7个样本。用粘接树脂活化剂处理各组根管桩表面5min,将粘接剂模块粘接到根管桩表面并固化,37℃下储存各组样本20h后,万能实验机进行剪切粘接强度测定。结果6种不同复合树脂粘接剂与纤维增强型复合树脂根管桩粘接后,各组根管桩表面剪切粘接强度之间的差异无统计学意义（F=2.32,P=0.45）。结论6种复合树脂粘接剂均适用于纤维增强型复合树脂根管桩的粘接。     

The investigation of non‐invasive techniques for treating early approximal carious lesions: an in vivo study

Objectives: The aim of this study was to examine non‐cavitated approximal caries using non‐invasive treatment methods. Materials and methods : Molar and premolar teeth with approximal caries were used in this in vivo study. Approximal caries lesions were evaluated with visual and radiographic inspection and with the DIAGNOdent device. Five groups were formed to study non‐invasive treatment, and each had at least 25 early approximal carious lesions. Patients in the control group were not treated. After the separation, either ozone application, acidulated phosphate fluoride gel, CPP‐ACP‐containing material (Tooth Mousse), or an antibacterial bonding agent (Clearfil Protect Bond) was used. For 18 months after the non‐invasive treatment, radiological controls were used to observe the progress of the initial and approximal caries in the 1st, 3rd, 6th and 12th months of follow‐up. A Mann–Whitney U‐test was used to perform the statistical analysis; in‐group comparisons were made with the Wilcoxon signed‐rank test, and a quantitative assessment was performed using a chi‐squared test. Results: At the end of 18 months, the caries lesions in the control group were observed to progress (P < 0.01). The lesions that were scored as 1a during a visual inspection recovered by using non‐invasive treatments. Conclusion: Approximal caries lesions that were detected at the early stages remained stationary when using antibacterial agents and materials that promoted remineralisation. Clinical relevance: Antibacterial agents and remineralisation materials can be used in treatment of early approximal caries lesions.     

Effectiveness of casein phosphopeptide‐amorphous calcium phosphate‐containing products in the prevention and treatment of white spot lesions in orthodontic patients: A systematic review

The purpose of the present systematic review was to evaluate the effectiveness of casein phosphopeptide‐amorphous calcium phosphate (CPP‐ACP)‐containing products in the prevention and treatment of active white spot lesions (WSL) in orthodontic patients. Searched the Scopus, PubMed, Web of Science, Cochrane, Virtual Health Language, ClinicalTrials, and Open Gray databases without limitations on the year or language of publication. We included controlled clinical trials with patients with fixed orthodontic appliances under the use of CPP‐ACP‐containing products compared to control, placebo, or other interventions in the prevention and treatment of WSL around orthodontic braces. Case reports, editorials, in vitro studies, annals of congress, and reviews were excluded. To assess the risk of bias, the revised version of the Cochrane tool for randomized trials (RoB 2.0) and Risk Of Bias In Non‐randomized Studies for non‐randomized trials were used. The biases were graded low, moderate, and high according to the tools used. Of the 599 articles found, 11 met the inclusion criteria. Of these, nine were randomized, controlled clinical trials and two were non‐randomized. Two studies were considered to have moderate bias risk, and the most‐used CPP‐ACP presented form was a cream for topical applications. Although CPP‐ACP‐containing products did not differ from other fluoride products, they were able to reduce WSL and neutralize the pH around the orthodontic braces. Products containing CPP‐ACP are effective in preventing and treating WSL around the braces. However, further studies with the same measurement method and periods of use, and other forms of presentation of CPP‐ACP are needed.     

The Effect of Fatigue on the Shear Bond Strength of Resin Bonded to Porcelain

Purpose The objective of this study was to determine whether fatigue cycling affects the shear bond strength of a resin that is initially strongly bonded to porcelain. Materials and Methods Thirty-five disks of a feldspathic/leucite porcelain were fired on a phosphate-bonded investment material. Each disk was etched with hydrofluoric acid and treated with a silane solution and an adhesive. Resin cement composite cylinders were applied to the treated porcelain and light cured. All specimens were stored for 1 week in distilled water at 37°C and then thermocycled for 1000 cycles in water between 2°C and 50°C. Fifteen of the specimens were randomly selected as control specimens. The remaining were subjected to fatigue cycling. A shear load was applied parallel to the bonded surface and cycled in a square wave between 0 and 26 N at 2 Hz for 27,500 cycles. All specimens were fractured in shear at 1.27 mm/min, and the shear bond strength was determined. Results Fifteen percent of fatigued specimens and 6.7% of the control specimens showed at least partial adhesive failure. All other specimens in both groups failed cohesively in the porcelain. There was no significant difference in the mean bond strengths of the fatigued and control groups (analysis of covariance, P > .05). Conclusions For the conditions investigated, cyclic fatigue did not reduce the bond strength of this resin/porcelain system.     

Effect of Light‐Emitting Diode (LED) Curing Modes on Resin/Dentin Bond Strength

Purpose: This study aimed to compare the effect of three curing modes of a high‐powered curing‐light source on the shear bond strength and marginal gap of light‐ and dual‐cured adhesive resin cements to dentin. Materials and Methods: Twelve freshly extracted intact human mandibular molars were selected for this study and stored in the saline solution. Three of the axial surfaces of the teeth were prepared to obtain flat dentinal surfaces. Thirty‐six ceramic disks (4‐mm diameter, 2‐ mm thick) were constructed from a pressable glass‐ceramic (Vision). The discs were etched with hydrofluoric acid and primed, and then divided into two equal groups, groups I and II (n = 18 each). Two adhesive systems were used following manufacturer's instructions. The discs of group I were bonded to the conditioned dentin surface using adhesive resin (Rely X Veneer), and group II discs were bonded to dentin using Rely X ARC. For each group, the resin was cured using three modes (fast, ramp, pulse). Interfacial gap at the dentin/resin interface was measured at eight predetermined sites for each specimen using a stereomicroscope, and shear bond strength of the bonded specimens was carried out using a universal testing machine. Results: Ramp‐cured specimens recorded significantly higher mean shear bond strengths for both dual‐ and light‐polymerized resins than those with fast and pulse modes. Moreover, fewer interfacial gaps were found at the resin/dentin interface in association with ramp cure modes of both resins. Most failures were adhesive failures at the dentin–resin luting agent (RLA) interface in specimens polymerized using high‐powered LED fast or pulse modes, while a cohesive failure pattern within the resin was associated with the ramp‐curing mode. Conclusion: Within the limitations of this study, the shear bond strength of an RLA to dentin was found to be enhanced with light‐ or dual‐polymerized adhesive resin using an LED light in ramp mode, whereas shear bond strength was significantly lower when polymerized using LED in fast or pulse modes.     

The Effect of Eugenol-Containing Temporary Cement on the Bond Strength of Two Resin Composite Core Materials to Dentin

Purpose This study investigated the effect of eugenol-containing temporary cement on the bond strength of two resin composite core materials (FluoroCore and Ti-Core) to dentin. Materials and Methods Dentin was exposed in three groups of extracted teeth (20 specimens each). In group one, dentin was covered with eugenol-containing temporary cement; the second group was covered with eugenol-free temporary cement; and the third group was left uncovered and served as a control group. All specimens were stored for 1 week at 37°C and 100% humidity. The dentin surfaces were cleaned and treated using the GLUMA adhesive system, followed by placement of composite core build-ups. Debonding of the core material was accomplished using the Accuforce Elite test system. Results There was a significant reduction in bond strength for the specimens covered with eugenol temporary cement (p < .0001), but no significant difference was found between the control group and the group treated with eugenol-free temporary cement. Bond strength of the Ti-Core material to dentin was significantly higher than that of FluoroCore (p < .0001). Conclusion Pretreatment of the dentin with eugenol-based temporary cement adversely affects the bond strength of resin composite core material to dentin.     

Effect of Different Cements on the Biomechanical Behavior of Teeth Restored with Cast Dowel‐and‐Cores—In Vitro and FEA Analysis

Purpose: To test the hypothesis that the type of cement used for fixation of cast dowel‐and‐cores might influence fracture resistance, fracture mode, and stress distribution of single‐rooted teeth restored with this class of metallic dowels. Materials and Methods: The coronal portion was removed from 40 bovine incisors, leaving a 15 mm root. After endodontic treatment and standardized root canal relief at 10 mm, specimens were embedded in polystyrene resin, and the periodontal ligament was simulated with polyether impression material. The specimens were randomly divided into four groups (n = 10), and restored with Cu–Al cast dowel‐and‐cores cemented with one of four options: conventional glass ionomer cement (GI); resin‐modified glass ionomer cement (GR); dual‐cure resin cement (RC); or zinc‐phosphate cement (ZP). Sequentially, fracture resistance of the specimens was tested with a tangential load at a 135° angle with a 0.5 mm/min crosshead speed. Data were analyzed using one‐way analysis of variance (ANOVA) and the Fisher test. Two‐dimensional finite element analysis (2D‐FEA) was then performed with representative models of each group simulating a 100 μm cement layer. Results were analyzed based on von Mises stress distribution criteria. Results: The mean fracture resistance values were (in N): RC, 838.2 ± 135.9; GI, 772.4 ± 169.8; GR, 613.4 ± 157.5; ZP, 643.6 ± 106.7. FEA revealed that RC and GR presented lower stress values than ZP and GI. The higher stress concentration was coincident with more catastrophic failures, and consequently, with lower fracture resistance values. Conclusions: The type of cement influenced fracture resistance, failure mode, and stress distribution on teeth restored with cast dowel‐and‐cores.