The Journal of Adhesive Dentistry, 02/2017

Purpose: The aim of this article was to provide an overview of the literature on the currently available bulk-fill composites, and to describe the common trends as well as the wide variations. The findings may help the clinician to select the proper material with regard to its applicability in various clinical situations. Methods: The literature up to October 2016 was reviewed based on a PubMed search (keywords: "bulk-fill OR bulkfill OR bulk fill" AND "composite OR composites"). Results: This review revealed that bulk-fill composites differ most from conventional composites in their increased depth of cure, which could mainly be attributed to an increase in translucency. However, the literature is inconsistent regarding the determination of the depth of cure. Flowable "base" bulk-fill composites seem most suitable for narrow cavities deeper than 4 mm, in particular when a higher adaptation potential thanks to better flowability in less accessible cavity configurations is desirable. In more extensive cavities, "full-body" bulk-fill composites with a high filler load are preferable. Then, resistance against wear and fracture becomes increasingly important, while a thicker consistency might also help in obtaining a good contact point. Tests related to shrinkage stress induced by bulk-filling seem inconsistent and their clinical relevance is unclear. Conclusion: More clinical studies that specifically focus on bulk-filling deep and large restorations are definitely required to fully explore the clinical benefits of bulk-fill composites. Keywords: bulk fill, composite, review, depth of cure, polymerization shrinkage

This paper presents European expert consensus guidelines on the management of severe tooth wear. It focuses on the definition of physiological vs pathological tooth wear and recommends diagnosis, prevention, counseling, and monitoring aimed at elucidating the etiology, nature, rate and means of controlling pathological tooth wear. Management decisions are multifactorial, depending principally on the severity and effects of the wear and the wishes of the patient. Restorative intervention is typically best delayed as long as possible. When such intervention is indicated and agreed upon with the patient, a conservative, minimally invasive approach is recommended, complemented by supportive preventive measures. Examples of adhesive, minimum-intervention management protocols are presented. Keywords: tooth wear, decision making, restorative treatment, direct, indirect

Purpose: To evaluate the influence of previous acid etching on the bond strength of a self-etch universal adhesive system on sound and eroded enamel and dentin. Materials and Methods: Flat enamel and dentin surfaces were obtained from bovine incisors (n = 44) and divided into two groups according to the exposure to erosive conditions: sound (without erosion) and eroded (after erosive challenge with 0.3% citric acid, pH 2.6, 5 min, 4x/day, 5 days). Each group was then divided into two subgroups (n = 11) according to the application or not of 37% phosphoric acid before applying a universal self-etch adhesive. Single Bond universal adhesive (3M ESPE) was applied and composite blocks were built up using Amelogen Plus (Ultradent). Sticks (1 × 1 mm) were obtained and the microtensile bond strength (µTBS) was assessed using a universal testing machine at a speed of 1 mm/min. Data were analyzed with two-way ANOVA and Tukey's tests (p 0.05). Results: For enamel groups, significant differences were observed for erosive challenge (p = 0.034) and acid etching (p = 0.047), but not for the interaction between them (p = 0.182). The means ± SD (MPa) for the erosive conditions were: sound, 25.02 ± 5.82a; eroded, 28.45 ± 5.92b; and for acid etching: without, 24.89 ± 5.39a; with, 28.58 ± 6.23b (different superscript letters indicate significant differences). For dentin, both the erosive condition (p = 0.936) and acid pretreatment (p = 0.084), as well as their interaction (p = 0.107), did not affect the bond strength. Conclusion: The erosive challenge and previous acid etching significantly increased the bond strength of the tested universal adhesive to enamel but not to dentin. Keywords: tooth erosion, enamel, dentin, microtensile bond strength, adhesive system

Purpose: To compare the shear bond strength of three different light-curing, flowable composites (Ionoseal [IS], Vertise flow [VF], and Futurabond NR + Grandio Flow [GF]) on MTA-Angelus [MTA] or Biodentine [BD] at three different time intervals. Materials and Methods: Freshly mixed MTA or BD was applied into 180 identical plaster molds. Three minutes, 15 min, and 2 days after mixing, specimens of IS, VF, and GF with standardized size and diameter were applied on MTA and BD specimens (n = 10 per material and time interval). Subsequently, all specimens were stored at 36°C and 100% humidity for 28 days. The shear bond strength was determined using a universal testing machine. Statistical evaluation was performed using multifactorial ANOVA and post-hoc Tukey's Test (p 0.05). Results: Multifactorial ANOVA did not show any significant influence of the combinations "lining material × time" (p = 0.257) and "calcium-silicate cement × lining material × time" (p = 0.241). Significant influences were detected for the interactions "calcium-silicate cement × lining material" (p = 0.000) and "calcium-silicate cement × time" (p = 0.009) and for the parameters calcium-silicate cement (p = 0.000), lining material (p = 0.000), and time (p = 0.008). The predominant failure mode of the restorative materials to the cement surfaces was mixed. Conclusion: Already 3 min after mixing, IS, VF, and GF achieved shear bond strengths on MTA or BD that were similar to those after 15 min and 2 days. Keywords: Biodentine, calcium-silicate cement, composite, lining material, MTA-Angelus, shear bond strength

Purpose: To compare the effect of boric acid solutions of different percentages to conventional irrigation solutions on the adhesive bond strength between fiber posts and radicular dentin surface with different cement types. Materials and Methods: One hundred fifteen extracted human incisors were endodontically instrumented to a length of 14-15 mm, and 12-mm post spaces were prepared with specific drills. Cylindrical fiber posts (Panavia Post) were luted with two different composite cements (Panavia F 2.0, Panavia SA) and cut into 1-mm-thick slices. These specimens were randomly allocated to 5 groups according to the irrigant applied: 1. control, no irrigant; 2. 10 ml of 2% chlorhexidine; 3. 10 ml of 5.25% NaOCl for 5 min and 10 ml of 17% EDTA for 3 min; 4. 10 ml of 5% boric acid solution at a temperature of 55°C for 60 s; 5. 10% boric acid solution, conditions as in group 4. Bond strength was determined using the push-out test. Microscopic assessment and SEM evaluations were performed in combination with push-out tests. Results: The push-out bond strengths of cervical segments were significantly higher than for the middle and apical segments in all groups. The type of irrigation solution used significantly affected the bond strengths of the posts. The 10% boric acid solution and EDTA + NaOCl irrigation solutions provided the highest bond strengths (p 0.005). SEM analysis showed that the dentin tubules were open and the smear layer was completely removed when EDTA/NaOCl and 10% boric acid were used as irrigation agents. Conclusion: Boric acid solutions, especially at a concentration of 10%, can be a viable alternative to the conventional irrigants used during endodontic treatment. The extent to which the 10% boric acid solution successfully removed the smear layer and the ease of rinsing boric acid from the root surface are advantageous. Keywords: boric acid, irrigation solution, composite cement, fiber post, bond strength

Purpose: To evaluate the influence of different pretreatments on the microtensile bond strength (µTBS) of an etch-and-rinse adhesive to eroded dentin. Materials and Methods: Thirty-six human teeth were ground down to their dentin layer and randomly divided into six groups (G1-G6; n = 6), G1 being the control group. Only in the test groups (G2-G6) were samples subjected to erosion using citric acid (pH 2.6) 10 x 2 min per day for five days. Between the erosive attacks, samples were stored in artificial saliva. After pretreatment - none (G1); none (G2); 2% chlorhexidine (30 s) (G3); prolonged primer application (1 min) (G4); roughening with a diamond bur (G5) and 10.5% NaOCl (1 min) (G6) - the adhesive OptiBond FL was applied. After the application of composite, samples were stored in water (7 d) and µTBS was determined. Data were evaluated using one-way ANOVA and Dunnett-T post-hoc test (p 0.05). Results: Eroded dentin without pretreatment (G2) resulted in significant reduction of µTBS compared with uneroded dentin (G1). µTBS after pretreatment with a diamond bur (G5) or NaOCl (G6) was not significantly different from that of the uneroded control group (G1). µTBS after pretreatment with chlorhexidine (G3) or with prolonged primer application (G4) was significantly lower than in the uneroded control group (G1), and not significantly different from the eroded control group (G2). Conclusion: The present data suggests that µTBS to eroded dentin pretreated with bur abrasion or NaOCl is similar to the µTBS to sound, uneroded dentin. Keywords: adhesion, dentin, erosion, microtensile bond strength

Purpose: To evaluate the effect of the type and concentration of photo-initiator on the long-term bonding efficacy to dentin in terms of mini-interfacial fracture toughness (mini-iFT). Materials and Methods: The bonding efficacy of the one-step self-etch (SE) adhesive Clearfil S3 Bond Plus and four derivative experimental adhesives (Leuven University Bond [LUB]), which were similar in composition except for the (co)photo-initiators (all prepared by Kuraray Noritake), containing 2.0 wt% camphorquinone (CQ) and 2.0 wt% EDMAB (LUB-CQ/amine_high), 0.35 wt% CQ and 0.35 wt% EDMAB (LUB-CQ/amine_low ), 2.0 wt% TPO (LUB-TPO_high), and 0.35 wt% TPO (LUB-TPO_low), was measured using a mini-iFT approach after being aged for 6 months and 1 year by water storage at 37°C (control: 1 week mini-iFT). The mini-iFT specimens were loaded until failure in a 4-point bending device to determine the interfacial fracture toughness (KIc). All fractured specimens were evaluated using scanning electron microscopy (SEM). Results: The mini-iFT of Clearfil S3 Bond Plus and the adhesives with high photo-initiator concentrations was not significantly different at 6 months, although it dropped significantly at 1 year. For each storage period, the mini-iFT of the adhesives with high photo-initiator concentrations was not significantly different from that of the commercial adhesive, in contrast to the significantly lower mini-iFT measured for adhesives with low concentrations of photo-initiator. SEM fracture analysis revealed that the adhesives with high concentrations of photo-initiator most frequently failed at the top of the hybrid layer at 1 week, while this failure pattern shifted to the bottom of the hybrid layer after aging. Conclusion: A one-step self-etch adhesive should contain photo-initiator in a sufficiently high concentration, as this directly improves its immediate and long-term bonding efficacy to dentin. While the mini-iFT remained stable up to 6 month of aging for both the commercial and the adhesive with a high concentration of photo-initiator, the mini-iFT was found to decrease after 1 year of aging. Keywords: adhesive, bonding, dentin, photo-initiator, fracture toughness, interface

Purpose: To investigate the effect of relative humidity and saliva contamination on short- and long-term bond strength of two self-etch adhesives to normal and artificially eroded dentin. Materials and Methods: A total of 480 dentin specimens were produced from extracted human molars. Half of the specimens (n = 240) were left untreated (normal dentin) whereas the other half (n = 240) were artificially eroded. The specimens were treated with Clearfil SE Bond (CSE) or Scotchbond Universal (SBU), and composite (Filtek Z250) was applied to the treated dentin surface under four experimental conditions: at a relative humidity of 45% or 85% without/with human saliva contamination. Shear bond strength (SBS) was measured after storage for 24 h (100% humidity; 37°C) or 1 year (tap water; 37°C). SBS results were statistically analyzed with a nonparametric ANOVA followed by Wilcoxon-Mann-Whitney tests (significance level: ? = 0.05). Results: SBS was significantly influenced by the dentin substrate (normal or artificially eroded dentin) and adhesive (p 0.001) but not by relative humidity, saliva contamination, or storage. SBS significantly differed (all p 0.001) following the ranking (MPa; medians [pooled]): SBU on normal dentin (21.1) > CSE on normal dentin (19.2) > SBU on artificially eroded dentin (17.1) > CSE on artificially eroded dentin (10.9). Conclusion: On normal dentin, the two self-etch adhesives showed stable bond strength over time even under adverse conditions such as high relative humidity and saliva contamination. However, erosively altered dentin had a detrimental effect on the bond strength of both the adhesives investigated. Keywords: adhesion, adhesive treatment, 10-MDP, pH cycling, air moisture, salivary contamination

Purpose: To investigate the buffering capacity of restorative materials during a simulated carious and intrinsic erosive attack. Materials and Methods: Cavities with a volume of 130 μl were milled (Cerec MC XL) out of blocks of Ceram X Mono (CM), Quixfil (QX), Filtek Supreme (FS), Apa Fill 3 (AF), an experimental dual-curing composite containing a bioactive glass (EX), Dyract eXtra (DY), Beautifil (BE), Equia Fil (EQ), Telio CAD (TL) (negative control), TheraCal (TC; positive control), and extracted teeth (ED). 80 μl of lactic acid (pH 4.5) and hydrochloric acid (pH 2.6) were each pipetted into the cavities of two samples of each material. Change of pH in the solutions was measured continuously for 12 min using a calibrated pH electrode. Results: CM, AF, and FS (final pH 3.0-3.2) neutralized hydrochloric acid to a significantly lesser extent than did BE, EQ, DY and QX (final pH 5.0-5.6) (p 0.05, ANOVA Scheffé). The lactic-acid buffering capacity of CM, BE, and AF was equivalent (final pH 6.3-7.4) to that of ED (7.5), but was surpassed by FS (pH 8.0). pH values for EX and TC (final pH 9.2-11.3) increased significantly (p 0.05) in response to both acids. Conclusions: Conventional restorative materials do not buffer better than human teeth. However, the experimental composite demonstrates that buffering against carious and intrinsic erosive acid attacks is technically feasible. Keywords: buffering capacity, ion release, bioactive glass, secondary caries, composite, erosion