Does the etching strategy influence the bonding of universal adhesive systems to primary teeth? A systematic review and meta-analysis of in vitro studies.

PURPOSE: To assess through a systematic review and meta-analysis of in vitro studies, the influence of the etching strategy (etch-and-rinse versus self-etch) of universal adhesive systems on bonding to primary teeth. METHODS: A systematic search was carried out in PubMed, Web of Science and Scopus. In vitro studies that compared the bond strength of the etching strategies of universal adhesives to primary teeth were included. Pooled-effect estimates were derived from a random-effects model by comparing the standardized mean difference between the etching strategies (α < 0.05). The risk of bias and heterogeneity between studies were also assessed (Cochrane and I2 tests). RESULTS: Seven studies were included in the review and six in the meta-analyses. For dentin, the immediate bond strength was not influenced by the etching strategy regardless of sound (Z = 0.72, p = 0.47) or caries-affected (Z = 1.27, p = 0.21) substrate, nor after aging (Z = 0.24, p = 0.81). It was not possible to perform a meta-analysis for the enamel substrate. Most studies have a medium risk of bias. CONCLUSIONS: This systematic review and meta-analysis of in vitro studies provides evidence that universal adhesives can be used in both etching strategies in primary dentin. The evidence is currently insufficient about whether selective acid etching of primary enamel is necessary when universal adhesive systems are used.

Zinc oxide eugenol paste jeopardises the adhesive bonding to primary dentine.

AIM: This was to evaluate the influence of root canal filling pastes on microshear bond strength (µSBS) of an adhesive system to primary dentine. METHODS: Human (32) primary molars were randomly assigned into four experimental groups (n = 8): zinc oxide eugenol paste (ZOE); iodoform paste (Guedes-Pinto paste); calcium hydroxide paste thickened with zinc oxide; and no filling paste (control). Flat dentine surfaces were covered with a 1 mm-thick layer of the pastes for 15 min at 37 °C. The pastes were mechanically removed from dentine surfaces, followed by rinsing and drying. After adhesive application (Adper Single Bond 2, 3M ESPE), starch tubes were placed over pre-treated dentine and filled with composite resin (Z250, 3M ESPE). The µSBS test was performed after 24 h of water storage at 37 °C. The failure mode was evaluated using a stereomicroscope. The µSBS values (MPa) were analysed with one-way ANOVA and Tukey post-hoc tests (α = 0.05). RESULTS: The lowest µSBS values were achieved when ZOE was used. No difference was found among other filling pastes compared with control group. All specimens showed adhesive/mixed failures. CONCLUSIONS: Zinc oxide eugenol paste negatively influenced the bond strength of adhesive systems to primary dentine. Iodoform-based Guedes-Pinto paste and calcium hydroxide paste thickened with zinc oxide did not influence the microshear bond strength values.

Degradation of resin-dentine bond of different adhesive systems to primary and permanent dentine.

AIM: To evaluate the water storage degradation of resin-dentine bonds of different adhesive systems to primary and permanent human dentine. METHODS: Flat occlusal human dentine surfaces of 15 primary molars and 15 permanent molars were randomly assigned according to adhesive systems: Adper Single Bond 2; Clearfil SE Bond and One Up Bond F Plus. After bonding procedures, the adhesives were applied according to the manufacturers' instructions and composite resin blocks were built. Restored teeth were sectioned rendering rectangular sticks (RS) (0.4 mm2). The RS were submitted to microtensile bond strength (µTBS) test according to the water storage time: 24 h, 1-year, and 2-years. Mean µTBS values were analysed by three-way analysis of variance (mixed design) and Tukey post hoc test (α = 0.05). The failure mode was analysed at 400× magnification. RESULTS: All three factors isolated showed significant influences on µTBS, as did the cross-product interactions between material vs. storage time (p = 0.01) and substrate vs. storage time (p = 0.002). Bond strength means to primary dentine were lower than to permanent dentine (34.7 ± 10.1 and 45.8 ± 12.9 mPa, respectively) after 2-years of water storage. The one-step self-etch adhesive (One Up Bond F Plus) showed less stable bond strength after 2-years of water storage. CONCLUSION: The resin-dentine bond of primary teeth was more prone to degradation over time compared to permanent dentine.

Bovine tooth is a substitute for human tooth on bond strength studies: A systematic review and meta-analysis of in vitro studies.

OBJECTIVES: This study aimed to systematically review the literature to compare the bond strength values achieved from human and bovine teeth of in vitro studies. DATA AND SOURCE: The PubMed/MEDLINE, ISI Web of Science and Scopus electronic databases were searched to select laboratorial studies that evaluated adhesive systems bond strength to human and bovine teeth. No publication year or language restriction was considered. STUDY SELECTION: From 1,285 potentially eligible studies, 15 were selected for full-text analysis, 11 were included in the systematic review and 9 in the meta-analysis. Two authors independently selected the studies, extracted the data and assessed the risk of bias. Mean differences were obtained by comparing bond strength values between human and bovine teeth (overall analysis), and considering enamel and dentin separately (subgroups analysis). Statistical analysis was performed using RevMan5.1, with random effects model, at a significance level of p=0.05. RESULTS: No significant difference was found between human and bovine teeth (p=0.35), either for enamel (p=0.07) or for dentin (p=0.93) substrates. Low to moderate heterogeneity was found on the meta-analysis. All included studies in the systematic review scored between medium and high risk of bias. CONCLUSIONS: Bovine teeth can be a reliable substitute for human ones on bond strength studies of adhesive systems to both enamel and dentin substrates.

The effect of grinding on the mechanical behavior of Y-TZP ceramics: A systematic review and meta-analyses.

The aim of this study was to systematically review the literature to assess the effect of grinding on the mechanical properties, structural stability and superficial characteristics of Y-TZP ceramics. The MEDLINE via PubMed and Web of Science (ISI - Web of Knowledge) electronic databases were searched with included peer-reviewed publications in English language and with no publication year limit. From 342 potentially eligible studies, 73 were selected for full-text analysis, 30 were included in the systematic review with 20 considered in the meta-analysis. Two reviewers independently selected the studies, extracted the data, and assessed the risk of bias. Statistical analyses were performed using RevMan 5.1, with random effects model, at a significance level of 0.05. A descriptive analysis considering phase transformation, Y-TZP grain size, Vickers hardness, residual stress and aging of all included studies were executed. Four outcomes were considered in the meta-analyses (factor: grinding x as-sintered) in global and subgroups analyses (grinding tool, grit-size and cooling) for flexural strength and roughness (Ra) data. A significant difference (p<0.05) was observed in the global analysis for strength, favoring as-sintered; subgroup analyses revealed that different parameters lead to different effects on strength. In the global analysis for roughness, a significant difference (p<0.05) was observed between conditions, favoring grinding; subgroup analyses revealed that different parameters also lead to different effects on roughness. High heterogeneity was found in some comparisons. Generally grinding promotes decrease in strength and increase in roughness of Y-TZP ceramics. However, the use of a grinding tool that allows greater accuracy of the movement (i.e. contra angle hand-pieces coupled to slowspeed turbines), small grit size (<50µm) and the use of plenty coolant seem to be the main factors to decrease the defect introduction and allow the occurrence of the toughening transformation mechanism, decreasing the risk of deleterious impact on Y-TZP mechanical properties.

Low-temperature degradation of Y-TZP ceramics: A systematic review and meta-analysis.

The aim of this study was to systematically review the literature to assess if low-temperature degradation (LTD) simulation in autoclave promotes deleterious impact on the mechanical properties and superficial characteristics of Y-TZP ceramics compared to the non-aged protocol. The MEDLINE via PubMed electronic database was searched with included peer-reviewed publications in English language and with no publication year limit. From 413 potentially eligible studies, 49 were selected for full-text analysis, 19 were included in the systematic review with 12 considered in the meta-analysis. Two reviewers independently selected the studies, extracted the data, and assessed the risk of bias. Statistical analysis was performed using RevMan 5.1, with random effects model, at a significance level of p<0.05. Descriptive analysis of monoclinic phase content data showed that aging in autoclave promotes an increase in m-phase content (ranging from 0% up to 13.4% before and 2.13% up to 81.4% after aging) with intensity associated to the material susceptibility and to the aging parameters (time, pressure and temperature). Risk of bias analysis showed that only 1 study presented high risk, while the majority showed medium risk. Five meta-analyzes (factor: aging×control) were performed considering global and subgroups analyzes (pressure, time, temperature and m-phase % content) for flexural strength data. In the global analysis a significant difference (p<0.05) was observed between conditions, favoring non-aging group. Subgroup analysis revealed statistical difference (p<0.05) favoring non-aging, for aging time >20h. However, for shorter aging times (≤20h), there was no difference between groups. Pressure subgroup analysis presented a statistical difference (p<0.05) only when a pressure ≥2bar was employed, favoring non-aging group. Temperature subgroup analysis showed a statistical difference (p<0.05) only when temperature=134°C was used, favoring the non-aging group. M-phase % content analysis presented statistical difference (p<0.05) when more than 50% of m-phase content was observed, favoring non-aging group. High heterogeneity was found in some comparisons. Aging in autoclave promoted low-temperature degradation, impacting deleteriously on mechanical properties of Y-TZP ceramics. However, the effect of LTD depends on some methodological parameters indicating that aging time higher than 20h; pressure ≥2bar and temperature of 134°C are ideal parameters to promote LTD effects, and that those effect are only observed when more than 50% m-phase content is observed.

Effect of air abrasion and polishing on primary molar fissures.

AIM: To evaluate the effect of air abrasion and polishing on primary molar fissures under light microscopy. METHODS: 15 exfoliated primary second molars were longitudinally sectioned and photographed under a stereomicroscope (40×; baseline evaluation). Sections were then randomly allocated into one of the two groups (n = 15) and treated by either air abrasion (aluminium oxide jet) or air polishing (sodium bicarbonate jet) for 30 s. After treatment, sections were washed with an air/water spray, dried with absorbent paper, and photographed as previously described (final evaluation). Baseline and final morphology were compared by two blinded examiners who evaluated changes in the width and depth of fissures. STATISTICS: The percentage of changed fissures was analysed, and the two treatments were compared using the Mann-Whitney test (α = 0.01). RESULTS: Both air systems resulted in fissure changes in most (93.3 %) of the sections. No significant differences in fissure width changes were found between treatments, but when changes in fissure depth were evaluated, air polishing was found to be less damaging than air abrasion (p < 0.01). CONCLUSION: Air abrasion and polishing cause changes to the anatomical configuration of occlusal fissures of primary molars.

Erosive effects of beverages in the presence or absence of caries simulation by acidogenic challenge on human primary enamel: an in vitro study.

AIM: To evaluate in vitro the erosive effects of beverages in the presence or absence of caries simulation (acidogenic challenge) on the microhardness of primary enamel. METHODS: Forty human primary teeth were submitted to the erosive effects: 3 × 20-min-long daily immersion in fresh orange juice (orange group), strawberry yogurt drink (yog group), or cola soft drink (cola group) separately or in combination with acidogenic challenge (pH cycling for 10 days). Specimens were also submitted to acidogenic challenge alone, and in the negative control group specimens were not submitted to any treatment. Mineral loss was evaluated by cross-sectional microhardness determination. The data (Knoop hardness numbers, KHN) were subjected to 2-way analysis of variance and Tukey's post hoc test (α = 0.05%). RESULTS: All the test beverages significantly reduced the sample cross-sectional enamel hardness (KHN ± SD, 235.93 ± 18.15, 257.23 ± 21.79, and 253.23 ± 13.86 in the orange, yog, and cola groups, respectively) compared to samples in the negative control group (290.27 ± 3.92). In vitro acidogenic challenge exacerbated the mineral loss induced by all beverages (166.02 ± 4.28, 190.43 ± 17.55, and 198.39 ± 21.39 in the orange, yog, and cola groups combined to acidogenic challenge, respectively) compared to acidogenic challenge alone. CONCLUSIONS: All beverages exhibited erosive effects on primary enamel. Simulated caries challenge considerably exacerbated the enamel softening of primary teeth.

Fluorescence of primary dentine after chemomechanical and conventional rotary excavation.

AIM: This was to compare fluorescence values of dentine remaining after caries removal using chemomechanical systems and conventional rotary methods. STUDY DESIGN: In vitro study. METHODS: 30 extracted primary teeth with proximal carious cavities were divided into three groups according to caries removal method: Carisolv, Papacarie and conventional low speed rotary burs. Carious (initial) and remaining (final) dentine evaluations were assessed by visual-tactile examination and DIAGNOdent. Transversal microhardness (TMH) of remaining dentine was evaluated. Fluorescence and TMH values were submitted to two-way ANOVA and the post hoc Tukey test (alpha = 0.05) and Pearson's linear correlation. RESULTS: Two-way ANOVA revealed that fluorescence values were similar between conventional rotary excavation, Carisolv and Papacarie groups (p = 0.0542). No statistically significant differences (p = 0.1147) were found to TMH values. No correlation was found between fluorescence and TMH values (r = -0.0273). CONCLUSION: All caries excavation methods resulted in similar remaining dentine fluorescence values. No correlation was found between fluorescence values and TMH of remaining dentine.