Objective: The purpose of this study was to evaluate, using atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), the morphological and structural changes of the enamel after irradiation with the Er:YAG laser. Background data: A previous study showed that subablative Er:YAG laser irradiation produced undesirable morphological changes on the enamel surface, such as craters and cracks; however, the enamel acid resistance was not increased. Methods: Fifty-two samples of human enamel were divided into four groups ( n = 13): Group I was the control (no laser irradiation), whereas Groups II, III, and IV were irradiated with the Er:YAG 100 mJ (12.7 J/cm ² ), 100 mJ (7.5 J/cm ² ), and 150 mJ (11 J/cm ² ), respectively, at 10 Hz with water spray. The morphological changes were observed by AFM and SEM. The weight percentages (wt%) of calcium (Ca), phosphorus (P), oxygen (O) and chlorine (Cl) were determined in the resultant craters and their periphery using EDS. Kruskal–Wallis and Mann–Whitney U tests were performed ( p ≤ 0.05) to distinguish significant differences among the groups. Results: The AFM images showed cracks with depths between 250 nm and 750 nm for Groups II and IV, respectively, and the widths of these cracks were 5.37 μm and 2.58 μm. The interior of the cracks showed a rough surface. The SEM micrographs revealed morphological changes. Significant differences were detected in Ca, P, and Cl in the crater and its periphery. Conclusions: AFM observations showed triangular-shaped cracks, whereas craters and cracks were evident by SEM in all irradiated samples. It was not possible to establish a characteristic chemical pattern in the craters.

Since the adhesion of resin composites to calcium silicate-based cement is considered challenging. Therefore, the best adhesion strategy should be indicated. This review aimed to assess the effect of different adhesive systems on the bond strength of resin composite to calcium silicate-based cement through a systematic review and meta-analysis. The subsequent PICOS framework used was: population, calcium silicate-based cement; intervention, use of self-etch adhesive systems; control, use of total-etch adhesive systems; outcome, bond strength; study design, in vitro studies. The literature search was conducted independently by two reviewers up to 18 February 2021. Electronic databases (PubMed, ISI Web of Science, SciELO, Scopus, and Embase) were searched for applicable articles. In vitro manuscripts studying the effect of adhesive systems on the bond strength of calcium silicate-based cement were considered. The meta-analyses were performed using Review Manager Software version 5.3.5 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark). Bond strength comparisons were made considering the type of calcium silicate-based cement (Mineral Trioxide Aggregate (MTA), Biodentine™, or TheraCal LC^®). A p-value < 0.05 was considered statistically significant. A total of 7321 studies were retrieved in databases searched. After full-text evaluation, 37 eligible papers were assessed for qualitative analysis, leaving a total of 22 papers for the quantitative analysis. According to the meta-analysis, the bond strength values of resin composite materials to MTA and TheraCal LC^® cement were favored when a total-etch adhesive system was used (p ≤ 0.02). On the other hand, the meta-analysis of the bond strength of resin-based materials to Biodentine™ calcium silicate-based cement was similar between both approaches (p = 0.12). The in vitro evidence suggests that the bond strength of resin-based materials to both MTA and TheraCal LC^® cement was preferred by using the total-etch adhesive strategy. However, when bonding to Biodentine™, the use of self-etch or total-etch strategies displayed promising results. Given the lack of evidence related to the chemical interaction of self-etch adhesive materials with the bioceramics, if self-etch adhesives are used for bonding resin-based restorations to calcium silicate-based cement, a pretreatment with phosphoric acid could be recommended.

Objective: The purpose of this study was to evaluate the acid resistance and structural changes in the enamel surface of permanent teeth after subablative Er:YAG laser irradiation in vitro . Background Data: Er:YAG irradiation laser is expected to enhance acid resistance and to produce morphological changes on the enamel surface. Methods: One hundred twenty samples of human enamel were divided into four groups ( n = 30): Group I was the control (no laser irradiation), and Groups II, III, and IV were irradiated with Er:YAG laser at 100 mJ (12.7 J/cm ² ), 100 mJ (7.5 J/cm ² ), and 150 mJ (11 J/cm ² ), respectively, at 10 Hz and with water spray. The samples were placed in an acid solution, and the released calcium was quantified by atomic absorption spectrometry. The weight percentages of calcium, phosphorus, oxygen, and chlorine on the enamel surface were determined by energy dispersive X-ray spectroscopy. The morphological changes were observed by scanning electron microscopy. One-way ANOVA and Kruskal–Wallis tests were performed ( p ≤ 0.05) to distinguish significant differences among groups. Results: The weight percentage of calcium in the samples obtained from EDS and the amount of calcium in the solution did not show any significant difference. All irradiated samples showed morphological changes on the enamel surface compared to the control group. Conclusions: The results of this study suggest that acid resistance of enamel due to subablative Er:YAG laser irradiation on the samples did not increase as expected. Morphological microscopic changes included craters and cracks on the irradiated zones.

The adhesion of some bacteria has been attributed to critical levels of roughness in hard tissues, which increases the risk of developing caries. The objective of this work was to assess the effect of deciduous and permanent tooth enamel surface roughness on bacterial adhesion. One hundred and eight samples of deciduous and permanent enamel were divided into two groups (n = 54). G1_DE deciduous enamel and G2_PE permanent enamel. The surface roughness was measured by profilometry and atomic force microscopy (AFM). Subsequently, the evaluation of bacterial adherence was carried out in triplicate by means of the XTT cell viability test. Additionally, bacterial adhesion was observed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The average values of the micrometric roughness in both groups were similar; however, in the nanometric scale they presented significant differences. Additionally, the G1_DE group showed the highest amount of adhered S. mutans and S. sanguinis compared to the G2_EP group. Although the roughness of deciduous and permanent enamel showed contrasting results according to the evaluation technique (area and scale of analysis), bacterial adhesion was greater in deciduous enamel; hence, enamel roughness may not be a determining factor in the bacterial adhesion phenomenon.

Objective: The purpose of this study was to evaluate in vitro morphological and chemical changes on human deciduous enamel produced by Er:YAG laser irradiation, fluoride application, combined treatment, and acid dissolution. Background data: Er:YAG laser has been proposed as a potential preventive dental caries strategy. There is scarce information regarding deciduous enamel. Methods: Eighty enamel samples were assigned to eight groups ( n =10): G1, control; G2, G3, and G4, Er:YAG laser irradiation at 7.5, 12.7, and 39.8 J/cm ² , respectively; G5, fluoride application; G6, G7, and G8, irradiation at previous densities plus fluoride application. Morphology was evaluated by scanning electron microscopy, and chemical composition was determined by energy dispersive X-ray spectroscopy before treatment (BT), after treatment (AT), and after acid dissolution (AAD). One way and repeated measures analysis of variance (ANOVA) were used ( p ≤0.05). Results: Morphology of lased surfaces included craters, exposed prisms, fractures, and melting. No morphological modifications appeared after fluoride application, or AAD. Chemically, AT: C atomic percentage (at%) decreased in G3, G4, and G8; O at% decreased in G5–G8; F content was higher for G7; trace elements remained under 1.0 at%; Ca at % increased in G4, G7, and G8; there were increments in P at% in G4 and G8; and Ca/P increased in G4, G7, and G8. AAD: F at% dropped to 0.00 in G5–G8; and P at% increased in G7. Conclusions: Morphological changes of Er:YAG irradiated enamel represented mild to severe damages. Conditions employed in this study are not recommended for deciduous caries prevention. Er:YAG energy density influenced chemical changes in enamel to enhance its structure. Acid dissolution removed fluoride from enamel surface.