The Journal of Adhesive Dentistry, 06/2020

Purpose: To compare the 2-year cumulative survival rates of class II restorations made according to Atraumatic Restorative Treatment (ART) with axial grooves and the high-viscosity glass-ionomer cement (HVGIC) Equia Fil (GC) and the conventional method using the resin composite Filtek Z250 (3M Oral Care). Materials and Methods: A parallel-group study design and a stratified randomization process (DMFS count and cavity size) were applied. Restorations were evaluated according to the ART restoration a nd USPHS criteria. Data were statistically analyzed using the proportional hazard rate regression model with frailty correction. Results: 272 class II restorations were placed in 131 people (mean age 26.2 years) by two dentists. The dropout rate of restorations was 2.6%. According to ART restoration and USPHS criteria, the 2-year cumulative survival rates of class II ART/HVGIC restorations were 96.2% and 97.0%, respectively, and 97.8% and 98.5%, respectively, for the conventional class II resin-composite restorations. No differences were observed in the cumulative survival rates between the two treatment groups at 2 years (ART criteria: p=0.26; USPHS criteria p=0.23). Conclusion: HVGIC Equia Fil used in the ART method with axial grooves and Filtek Z250 in the conventional method provided high survival rates for restoring class II cavities over 2 years. Keywords: atraumatic restorative treatment, glass-ionomer cement, resin composite, class II, cavity size, restorations, axial grooves

Purpose: To survey dentists in Germany regarding their preferred cementation regimen for fixed dental prostheses (FDPs) fabricated from various restorative materials. Materials and Methods: An online survey was developed for completion by dentists in Germany between 08/2019 and 02/2020. The questionnaire gathered information about the cementation regimen (conventional, including the acid-base cements zinc-oxide phosphate or any glass-ionomer cement; self-adhesive; adhesive; don’t know) that the participant would preferably select for the insertion of single- or multi-unit FDPs fabricated from various restorative materials. Data were also collected on demographic and personal characteristics. Results: A total of 721 dentists completed the survey, and the data from 688 questionnaires were included in the analysis. Conventional cementation was the option of choice for restorations fabricated from alloy/porcelain-fused-to-metal among 91.0% of the participants and for restorations fabricated from polycrystalline ceramics among 42.9% of the participants. Adhesive cementation was preferred for restorations fabricated from feldspathic/leucite-reinforced glass ceramics (77.9%), lithium-disilicate glass ceramics (67.5%), zirconia-reinforced lithium-silicate glass ceramics (42.0%), and CAD/CAM resin composites (63.8%). Uncertainties regarding the appropriate cementation protocol for restorations fabricated from CAD/CAM resin composites were reported by 15% of the participants. More than 20% of the participants selected a technique that is less or not at all recommended for the cementation of restorations fabricated from zirconia-reinforced lithium-silicate glass ceramic and CAD/CAM resin composites. Conclusion: The results of the survey suggest that dentists in Germany select the cementation regime depending on the restorative material. Some of the participating dentists selected cementation regimens that are less or not at all recommended for restorations fabricated from zirconia-reinforced lithium-silicate glass ceramic and CAD/CAM resin composites, or were not sure about the appropriate cementation protocol. Keywords: dental cements, ceramics, composite cements, crown, fixed bridge, denture, partial, fixed, composite resins, alloys, porcelain metal

Purpose: The purpose of this multicenter study was to evaluate the survival and quality outcome of direct composite buildups in the anterior dentition based on representative sample sizes. Materials and Methods: At three university clinics in Germany, the survival and quality outcome of n = 667 direct composite buildups performed between 2001 and 2012 was evaluated in n = 198 participants. Survival outcomes were categorized as failure (F), survival (SR), or successful (S). Restorations still in place and without failure prior to follow-up (n = 567) were rated using modified USPHS/FDI criteria to obtain the quality outcome. Detailed failure analysis was done by means of Cox regression models. Results: The restricted mean for overall survival was 15.5 years. N = 576 restorations were classified as successful (S), n = 81 survived with repair (SR) and n = 8 failed (F). Two restorations were removed due to iatrogenic interventions. Overall survival rates after 2, 10, and 15 years were 98.8% (CI: 97.6 and 99.4), 91.7% (CI: 89.0 and 93.8), and 77.6% (CI: 72.2 and 82.2), respectively. Functional survival rates were 100.0%, 98.9% (CI: 97.5 and 99.5), and 98.5% (CI: 96.7 and 99.3), respectively. Clinical quality was rated as excellent or good for most restorations. The dominant failure mode was chipping; however, regression analysis did not detect any influence of the evaluated parameters “enlargement range,” “position in the jaw,” or “tooth type” on failure. Conclusion: This multicenter study represents the first of its type including clinical survival and quality data on 576 direct anterior composite buildups over a restricted mean follow-up of 15.5 years in a relatively large group of participants. In particular, functional survival was outstanding due to the clinical reliability of this treatment option, while simultaneously providing flexibility, reparability, and minimal invasiveness. Keywords: direct composite buildups, recontouring, diastema, survival, clinical quality parameters, follow-up

Abstract: Tooth-cavity preparation contributes to a large extent to the quality of the direct posterior composite restoration, the so-called hidden quality of the restoration. Indeed, the effect of a poor cavity design is not immediately visible after placement of the restoration. To correctly prepare a cavity for a posterior composite restoration, the tooth to be restored should first be profoundly biomechanically analyzed. Here, the forces that work on the tooth during occlusion and articulation, and the amount and quality of the remaining tooth structure determine the cavity form. In addition, the dental tissues must be prepared in order to receive the best possible bond of the adhesive and subsequent restorative composite. A well-finished cavity preparation enables the restorative composite to adapt well, providing a good marginal ?seal to the direct benefit of the clinical lifetime of the posterior composite restoration. Finally, it is highly recommendable to isolate the teeth with rubber-dam before starting with the cavity preparation, as this increases the visibility of the operating field and allows the operator to work in a more precise way.

Abstract: Currently, there is a trend towards simplification of materials and clinical procedures. Simplification and quality can go together if the dentist works with materials and techniques that are well proven in vitro and in vivo. The placement of a high-quality class-1/2 direct posterior composite restoration can be time efficient following a standardized layering protocol and using composite materials that adapt well to the tooth surface and are able to mimic the natural tooth. When these materials are applied in a controlled way, finishing and polishing can also be shortened. In this article, an effective layering and finishing/polishing protocol for medium-sized class-1/2 direct posterior composite restorations is presented. Following the histo-anatomic buildup of natural teeth, dentin must be concave, as opposed to convex enamel. An isochromatic, medium-opaque, highly filled flowable composite is used to replace dentin. Enamel is replaced with a medium-translucent small-particle hybrid composite. Enamel is modelled in an anatomical way, following a successive cusp-by-cusp buildup approach. Clinical experience shows that the combination of both materials used according to this so-called bi-laminar histo-anatomical layering approach results in restorations that blend in very well within the surrounding tooth structure. Following a simplified finishing and polishing protocol, the composite restorations will have a correct contour, seamless margins, and a smooth, glossy surface. Keywords: adhesion, finishing, flowable, layering, polishing, polymerization, posterior composite, shrinkage

Purpose: This study evaluated the effect of an aromatic silane compound and acidic functional monomer on the bond strength of fused quartz. Materials and Methods: A total of 264 disk specimens were fabricated from fused quartz for shear bond testing. Two silane compounds were used: 3-(trimethoxysilyl)propyl methacrylate (3-TMSPMA) and 3-(4-methacryloyloxyphenyl) propyltrimethoxysilane (3-MPPTS). As acidic functional monomers, 4-methacryloyloxyethyl trimellitate (4-MET) and 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) were used. The disks were primed with one of each silane compound with or without the acidic functional monomer of the same molarity. The specimens were bonded with a tri-n-butylborane (TBB) initiated luting material. The shear bond strength was determined before and after 10,000 thermocycles. Bond strength was statistically evaluated with Kruskal-Wallis, Mann-Whitney U-, and Steel-Dwass tests. To test dye penetration, the specimens were immersed in 0.5 wt% fuchsin solution for 24 h after priming with each condition, bonding, and 10,000 thermocycles. The dye penetration area was determined by observing the backside of the bonded specimen with an optical microscope. The relationship between the shear bond strength and dye penetration ratio was analyzed with Spearman’s rank correlation test. Results: The highest post-thermocycling bond strengths in the 1 mol% and 2 mol% groups were 3-TMSPMA + 10-MDP and 3-MPPTS + 10-MDP. Spearman’s rank correlation coefficient between shear bond strength and dye penetration area was γ = -0.7519, indicating a strong negative correlation. Conclusion: The surface treatments of 3-TMSPMA and 3-MPPTS combined with 10-MDP yielded higher bond strength after 10,000 thermocycles than those combined with 4-MET, despite the similarity in molarity. The shear bond strength was negatively correlated with the dye penetration area. Keywords: acidic functional monomer, adhesive, bonding, ceramics, silane coupling, tri-n-butylborane

Purpose: To evaluate whether the composite cement tensile bond strength is affected by different firing cycles or etching conditions on zirconium-incorporated lithium-silicate glass ceramics. Materials and Methods: Specimens (N=53) were prepared from blocks of zirconium-incorporated lithium-silicate glass ceramic (ZLS, Dentsply Sirona) with specimen dimensions of 12.5 x 14 x 2 mm (L x W x H, respectively). The specimens were subjected to different firing cycles and etching conditions. They were subsequently cemented onto titanium rods (grade V Ti-alloy, 4.8 mm in diameter, and 25.4 mm in length) with self-adhesive composite cement (TheraCem, Bisco), and then tested for tensile bond strength (TBS). The least-square means linear regression model was used to analyze the effects on TBS using JMP Pro 14 (SAS) and the post-hoc Tukey test with α = 0.05. Results: The TBS was significantly affected by etching duration (p < 0.001) and firing cycles (p < 0.001), but was not significantly affected by etchant concentration (p = 0.31). The highest TBS peak (4.83 MPa) on the fit curve was observed at 45 s of etching time. The lowest TBS was observed at 20 s (3.02 ± 0.28 MPa) etching time. In terms of firing cycles, 1 firing cycle (4.00 ± 0.71 MPa) provided the highest TBS. In contrast, the lowest TBS was observed for as-machined ZLS specimens but without a firing step (3.29 ± 0.53 MPa). Conclusions: Changing the etching time and firing conditions of the specimens had a significant effect on the composite cement tensile bond strength to zirconium-incorporated lithium-silicate glass ceramic. In contrast, etching the specimens with different acid concentrations, 5% or 9.6% of HF, did not significantly change the composite cement tensile bond strength. Keywords: dental ceramic, adhesive bond strength, acid etching, lithium disilicate, composite cement

Purpose: To investigate the effect of application of a primer resembling a universal adhesive with or without light irradiation followed by a hydrophobic bonding agent on bonding effectiveness, based on shear bond strength (SBS) and shear fatigue strength (SFS) tests. Materials and Methods: An experimental two-step self-etch adhesive (BZF) that comprises a primer resembling a universal adhesive (BZP) and a hydrophobic bonding agent (BZB) were used. The two-step self-etch adhesive, Clearfil SE Bond 2 (SE), served as a comparison. Three experiments were conducted. Experiment 1: (1) BZP alone without light irradiation (BZP w/o); (2) BZP alone with light irradiation (BZP w/); (3) BZP without light irradiation followed by BZB (BZPB w/o); (4) BZP with light irradiation followed by BZB (BZPB w/). Experiment 2: (1) BZPB w/o, (2) SE primer + BZ bonding agent (SEP + BZB), and (3) SE primer + SE bonding agent (SEPB). The bonded specimens of experiment 1 and 2 were subjected to SBS tests. Experiment 3: Bonded specimens following the same experimental protocol as experiment 2 were subjected to SFS tests. Results: BZPB showed significantly higher mean enamel and dentin SBS than did BZP. BZPB showed significantly higher SBS without light irradiation than with light irradiation to both substrates. The group of BZPB without light irradiation showed significantly higher SBS than the group of BZPB with light irradiation to both substrates. For experiments 2 and 3, although no significant differences were found in SBS among groups for enamel, SEP + BZB showed a significantly lower SBS and SFS than other groups for dentin. Conclusions: BZF showed bonding performance equivalent to that of the gold standard Clearfil SE Bond 2. Keywords: HEMA free primer, hydrophobic bonding agent, shear bond strength, shear fatigue strength