The Journal of Adhesive Dentistry, 03/2018

Purpose: The primary objective of this systematic review was to compare treatment outcomes of direct and indirect permanent restorations in endodontically treated teeth, and provide clinical suggestions for restoring teeth after endodontic treatment. Materials and Methods: Electronic databases (Medline, EMBASE, CENTRAL) and gray literature were screened for articles in English that reported on prospective and retrospective clinical studies of direct or indirect restorations after endodontic treatment with an observation period of at least 3 years. Primary outcomes were determined to be short-term (≤ 5 years) and medium-term (> 5 and ≤ 10 years) survival. Secondary outcomes included restorative and endodontic success of restored teeth. The quality of included studies and risk of bias were assessed using Cochrane Collaboration's tool for RCTs (randomized controlled trials), the Newcastle-Ottawa Scale for cohort studies, and the Agency for Healthcare Research and Quality (AHRQ) methodology checklist for cross-sectional studies. The GRADE system was used for assessing collective strength of the overall body of evidence. Results: Of 2547 screened articles, only 9 (2 RCTs, 3 retrospective cohort studies, 3 cross-sectional studies) met the inclusion criteria, and 8 studies were used in the meta-analysis. In general, indirect restorations (mostly full crowns) showed higher 5-year survival (OR 0.28, 95% CI 0.19-0.43, p 0.00001) and 10-year survival (OR 0.20, 95% CI 0.12-0.31, p 0.00001) than direct restorations. However, there was no statistical difference in short-term (≤ 5-years) restorative success (OR 0.32, 95% CI 0.05-2.12, p = 0.24) and endodontic success (OR 0.88, 95% CI 0.72-1.08, p = 0.22). Conclusions: Based on current evidence, there is a weak recommendation for indirect restorations to restore endodontically treated teeth, especially for teeth with extensive coronal damage. Indirect restorations using mostly crowns have higher short-term (5-year) and medium-term (10-year) survival than do direct restorations using composite or amalgam (GRADE quality of evidence: low to moderate), but no difference in short-term (≤ 5 years) restorative success (low quality) and endodontic success (very low quality). There is a need for high-quality clinical trials, especially well-designed RCTs. Keywords: endodontic treatment, direct restorations, indirect restorations, survival rates, success rates, apical periodontitis

Purpose: One-step self-etch adhesives are among the most popular adhesives to directly bond composite to tooth tissue, mainly because of their perceived ease-of-use. The aim of this randomized controlled trial was to evaluate the clinical performance of a HEMA-free 1-step self-etch adhesive (1SEa), as compared with a 3-step etch-and-rinse adhesive (3E&Ra). Materials and Methods: 267 non-carious cervical lesions in 52 patients were restored with a microhybrid composite Gradia Direct (GC), bonded in random order either with the HEMA-free 1SEa G-Bond (GB; GC) or the considered gold-standard 3E&Ra Optibond FL (OFL; Kerr). The restorations were evaluated after 6 months, 1, 2, 3, 5 and 9 years of clinical service for retention, marginal adaptation, marginal discoloration, caries occurrence and tooth sensitivity. Statistical analysis was done using a logistic regression model with generalized estimating equations (2-way GEE model). Results: The patient recall rate at 9 years was 82.6%. The overall clinical success rate was 80.3% and 79.5% for GB and OFL, respectively. In total, 47 restorations (23 GB, 24 OFL) failed because of retention loss, severe marginal defects and/or discoloration and/or caries. A similar retention rate of 89.7% was recorded for both adhesives GB and OFL. Slight marginal defects and superficial marginal discoloration, though both still clinically acceptable, were significantly more observed at the incisal enamel side of GB (92.4% and 52.1%, respectively) than OFL (59.6%; 30.8%) restorations (p 0.05). Conclusion: After 9 years of clinical service, class-V restorations bonded with the HEMA-free 1SEa performed clinically equally successful as those bonded with the 3E&Ra. However, more marginal deterioration, though still clinically acceptable, was recorded at the incisal enamel side for the 1SEa. Keywords: randomized clinical trial, RCT, Class V, bonding, adhesion, clinical effectiveness

Purpose: This in vitro study aimed to evaluate the shear bond strength (SBS) of particulate filler composite (PFC) to saliva- or water-contaminated fiber-reinforced composite (FRC). Materials and Methods: One type of FRC substrate with semi-interpenetrating polymer matrix (semi-IPN) (everStick C&B) was used in this investigation. A microhybrid PFC (Filtek Z250) substrate served as control. Freshly cured PFC and FRC substrates were first subjected to different contamination and surface cleaning treatments, then the microhybrid PFC restorative material (Filtek Z250) was built up on the substrates in 2-mm increments and light cured. Uncontaminated and saliva- or water-contaminated substrate surfaces were either left untreated or were cleaned via phosphoric acid etching or water spray accompanied with or without adhesive composite application prior applying the adherent PFC material. SBS was evaluated after thermocycling the specimens (6000 cycles, 5°C and 55°C). Results: Three-way ANOVA showed that both the surface contamination and the surface treatment signficantly affected the bond strength (p 0.05). Saliva contamination reduced the SBS more than did the water contamination. SBS loss after saliva contamination was 73.7% and 31.3% for PFC and FRC, respectively. After water contamination, SBS loss was 17.2% and 13.3% for PFC and FRC, respectively. The type of surface treatment was significant for PFC (p 0.05), but not for FRC (p = 0.572). Conclusion: Upon contamination of freshly cured PFC or semi-IPN FRC, surfaces should be re-prepared via phosphoric acid etching, water cleaning, drying, and application of adhesive composite in order to recover optimal bond strength. Keywords: saliva contamination, water contamination, composite, fiber-reinforced composite, shear bond strength, composite repair

Purpose: The methacrylate monomer 2-hydroxyethyl methacrylate (HEMA), commonly used in dentistry, has multiple effects on the immune system. This study examined whether HEMA affects the immune system by inducing formation of the NLRP3 inflammasome. Materials and Methods: Human peripheral blood mononuclear cells (PBMCs) and the human monocyte cell line THP1 were cultured with or without 1000 μM HEMA. To block NLRP3 inflammasome activation, 130 mM KCl was also added to some of the cultures. For the in vivo studies, two different experimental setups were used. In the first experimental setup, mice were injected subcutaneously at the base of the tail with 20 μmol HEMA with or without 100 mM KCl. After 3 weeks, the animals were given an identical booster injection. Two weeks after the last injection, the mice were sacrificed and splenectomized. In the second experimental setup, HEMA (20 μmol), with or without 100 mM KCl, was injected subcutaneously into the tails of BALB/c mice. The mice were given two similar injections at 3-week intervals to allow evaluation of the local inflammation induced by HEMA. After the last inoculation, the injection site was examined daily for 4 days, after which the mice were sacrificed. Results: Cultures of PBMCs and THP1 cells exposed to HEMA in vitro produced more IL-1ß and IL-18 than did control cells. Increased extracellular concentration of KCl inhibited the secretion of IL-1ß. HEMA exposure did not induce cytokine production in variants of the THP1 cell line unable to form the NLRP3 inflammasome. For the first experimental setup, the level of unstimulated basic splenocyte proliferation in vitro was significantly higher in cultures from mice exposed in vivo to HEMA only than in cultures from mice injected with HEMA plus KCl. In the second experimental setup of the in vivo studies, the HEMA-treated mice developed more pronounced inflammation at the site of injection compared to the group of mice given HEMA plus KCl. Conclusion: HEMA affects the immune system by inducing formation of the NLRP3 inflammasome. Keywords: 2-hydroxyethyl methacrylate, dentin-bonding agents, Interleukin-1ß, Interleukin-18, inflammasome

Purpose: To evaluate the effect of acidic challenge (AC) on the properties and bond stability of restorative materials to primary enamel and dentin. Materials and Methods: One hundred twenty primary molars were assigned to 12 groups according to substrate (enamel or dentin), restorative material (composite, high-viscosity glass ionomer cement [HV-GIC] or resin-modified glass-ionomer cement [RM-GIC]), and immersion after restoration (control [saline solution/7 days] or AC [cola-based drink/5 min/3x per day/7 days]). Twenty-four hours after the restorative procedure, specimens were submitted to one of the proposed challenges. Half of the specimens were immediately subjected to the microshear bond strength test, and the other half after 12 months. To determine flexural strength flexural strength and superficial roughness (SR), 30 specimens were built up. After 24 h, the first measurement of SR from 10 specimens was performed. Specimens were then immersed in one of proposed challenges and SR was measured again. Subsequently, flexural strength testing was performed. Bond strength, surface roughness, and flexural strength data were subjected to ANOVA and Tukey's test. Results: Composite showed the highest bond strengths compared to the others materials on both substrates. The storage period negatively influenced the bond strength only for composite groups in dentin. AC after restoration negatively influenced bond strength when the materials were evaluated in eroded dentin. AC affected the second SR measurement, showing increased SR for all restorative materials. AC did not affect flexural strength. Conclusion: The acidic challenge jeopardizes the surface roughness and bond strength of restorations to eroded dentin. Keywords: pediatric dentistry, dental erosion, bond strength, flexural strength, surface roughness

Purpose: To compare microtensile bond strength and characterize the bond of nano-structured alumina-coated vs tribochemically silica-treated zirconia specimens. Materials and Methods: Eight zirconia blocks were assigned to two groups: nano-structured alumina coating (AlN) and tribochemical silica treatment (CoJet) followed by RelyX Ceramic Primer (COJ). For each group, two identically pre-treated zirconia blocks were bonded with RelyX Unicem 2 Cement and cut into 30 stick-shaped specimens (1 x 1 x 9 mm3). A total of 120 specimens were stored in distilled water at 37°C for 24 h and then assigned to three groups (n = 20/test group): short-term test, thermocycling 5000 cycles, and thermocycling 10,000 cycles. The specimens were tested in tensile mode. The bond strength results were analyzed using two-way ANOVA, followed by one-way ANOVA and Tukey's HSD (α = 0.05). Failure mode and surfaces were analyzed with optical microscopy and SEM. FTIR and EDS were used for chemical analyses on primer-, mechanically and/or chemically pre-treated surfaces. Results: The mean bond strengths of AlN and COJ groups were not statistically significantly different in all aging conditions (p > 0.05). Thermocycling significantly decreased the bond strength of both groups (p 0.01). The AlN groups exhibited predominantly either adhesive or mixed failure, whereas the specimens in the COJ groups mainly presented either mixed or cohesive failure in composite cement. Silane chemically reacted with mechanically pre-treated COJ surface via the absorption of Si-O group. Conclusion: The composite-zirconia bond strength after application of a nano-structured alumina coating was comparable to that after tribochemical silica treatment. Keywords: zirconia, tribochemical silica coating, nano-structured alumina coating, surface treatment, composite cement, microtensile bond strength, surface characterization

Purpose: To examine the influence of phosphoric acid containing chlorhexidine on the dentin bond stability of a universal and a 2-step etch-and-rinse adhesive. Materials and Methods: Eighty sound bovine incisors were randomly assigned to 8 groups (n = 10) according to: phosphoric acid (37% phosphoric acid [CTR] or 37% phosphoric acid with 2% chlorhexidine [CHX]); adhesive (Scotchbond Universal Adhesive [SBU]or Adper Single Bond 2 [SB2]); and water storage time (24 h and 6 months). Both acids and adhesives were applied to flat dentin surfaces (following manufacturer's instructions) upon which composite cylinders were built up (0.72 mm2). After storage in distilled water at 37°C for 24 h or 6 months, the composite cylinders were submitted to microshear bond strength (µSBS) testing. Bond strength data (MPa) were analyzed using three-way ANOVA and post-hoc Tukey's test (α = 5%). Results: The interaction among factors was significant (p = 0.012). Both adhesives showed similar 24-h bond strengths regardless of the phosphoric acid. After 6 months, similar values were found for both materials when control phosphoric acid was used, but CHX phosphoric acid produced statistically significantly lower bond strengths for SBU. SB2 bond strength was not affected by acid type. Conclusion: Phosphoric acid containing chlorhexidine induced premature bond strength degradation of Scotchbond Universal Adhesive. Keywords: universal adhesive, chlorhexidine, phosphoric acid, dentin, microshear bond strength

Purpose: The present study evaluated the influence of air entrapment within demineralized dentin on bond strength, nanoleakage, and degree of conversion. Materials and Methods: A vacuum pump with adjustable pressure was used to control the gaseous pressure of a sealed container during the application of a two-step etch-and-rinse adhesive to demineralized dentin. Atmospheric pressure was used as control, and reduced pressures (0.08, 0.06, 0.04 MPa) as experimental variables. Simulated pulpal pressure was adopted during the bonding procedures. After making composite buildups and 24-h water storage, 48 specimens were occlusogingivally sectioned into beams for microtensile bond strength testing, interfacial morphology observation, and nanoleakage evaluation immediately (6 for each group) or after artificial aging (6 for each group); 20 specimens (5 for each group) were occlusogingivally sectioned into slices for degree of conversion testing. Failure modes were compared using the chi-squared test. The other data were analyzed using ANOVA. Results: When air within composite-dentin interface was thinned with reduced pressures, more thorough adhesive infiltration was achieved, and less distinct nanoleakage as well as higher bond strength were observed compared with control groups, regardless of artificial aging. Mixed failure was predominantly identified, and its percentage was higher in the reduced pressure groups than in the controls. Adhesive application at reduced pressure improved the degree of conversion. Conclusion: Air entrapment in the demineralized dentin adversely affects composite-dentin bonds. Adhesive application at reduced pressure is helpful for reducing entrapped air, thereby improving the durability of composite-dentin bonds. Keywords: vacuum, microtensile bond strength, bond durability, dentin bonding, nanoleakage, polymerization

Purpose: To evaluate the influence of different surface treatments of lithium disilicate glass ceramics on the bonding efficacy of three luting composites. Materials and Methods: A total of 450 blocks of e.max CAD (Ivoclar Vivadent) ground with 600-grit silicon carbide paper were prepared and divided into three groups (n = 150) according to the composite cements used: Variolink Esthetic DC (VE), Multilink Automix (MA), and SpeedCEM (SC). Each group was further divided into five subgroups (n = 10) according to the surface treatment performed: no treatment (control), Monobond Plus (MP), 37% phosphoric acid and Monobond Plus (PA), 5% hydrofluoric acid and Monobond Plus (HF), and Monobond Etch & Prime (ME). All treated ceramic specimens were bonded with three composite cements and light cured. After 24-h water storage and 5000 or 10,000 thermocycles, tensile bond strength (TBS) was measured. The specimens underwent failure mode analysis. The results were statistically analyzed using two-way ANOVA and t-tests with Bonferroni correction. Results: The TBSs were significantly influenced by surface treatments (p 0.05). There were no significant differences in HF and ME among most of the groups. Furthermore, ME showed the highest bond strength with MA after 10,000 thermocycling. Most specimens of the ME groups exhibited cohesive failures, whereas a combination of adhesive failures and mixed failures were observed in control, MP, PA, and HF groups. Conclusion: In the surface treatment of lithium disilicate glass ceramics, Monobond Etch & Prime was found to be a possible substitution for the combination of hydrofluoric acid and Monobond Plus. Keywords: lithium disilicate ceramics, adhesion; tensile bond strength, thermocycling