Comparison of shear bond strength of orthodontic brackets bonded with a universal adhesive using different etching methods

Incorporation of Zirconium Oxide Nanoparticles in Adhesive Resin for Bonding of Brackets to Enamel Conditioned with Er,Cr:YSGG, Photodynamic Therapy, and Phosphoric Acid

Objective: To evaluate the effect of enamel conditioning methods, that is, total-etch and rinse (TER), Er,Cr:YSGG (ECYL), and photodynamic therapy (PDT) on the shear bond strength (SBS) of orthodontic metallic brackets bonded using Zirconium oxide experimental adhesive (ZOEA). Methods: Sixty human incisor buccal surfaces were cleaned and allocated into three groups based on the method of enamel surface treatment, that is, TER using 37% phosphoric acid gel, methylene blue photosensitizer activated by PDT and ECYL (n = 20 each). Each group was further divided into two subgroups (n = 10) based on the type of adhesive, that is, ZOEA and experimental adhesive (EA). Metallic brackets were seated using composite resin. Samples were placed in a universal testing machine for SBS and failure mode using the ARI index. One-way analysis of variance and post hoc Tukey were used for multiple comparisons. ARI was presented in percentages in different investigated groups. Results: TER+ZOEA (17.16 ± 0.41 MPa) displayed the highest bond integrity. However, group PDT+EA (11.34 ± 0.25 MPa) demonstrated the lowest bond scores. The intergroup comparison revealed that the TER system displayed significantly higher SBS values than the PDT and ECYL groups (p < 0.05). The intragroup comparison revealed that enamel conditioned with TER and brackets bonded with ZOEA and EA displayed comparable bond integrity (p > 0.05). Conclusions: Enamel conditioned with TER bonded to a metallic bracket displayed better bond strength than PDT and ECYL. Zirconium oxide nanoparticles incorporated in adhesive have proved to be promising in improving the bond integrity of adhesive.

Application of laser on enamel surface with three types of bioactive glasses-based resin infiltrants: An in vitro study

OBJECTIVE

The study aimed to evaluate and compare the surface micro-hardness, roughness, color, and morphology of enamel after Er,Cr:YSGG laser irradiation, followed by application of three types of bioactive glasses-based resin infiltrants, and the samples groups were challenged with the pH cycle.

METHODOLOGY

Experimental photoactivated resin infiltrants were synthesized using dimethacrylate resins, whereby three different types of bioactive glasses (BGs), i.e., 45S5, fluoridated-BG (F-BG), and borosilicate-BG (B-BG), were incorporated into the resin system. Initially, white spot lesions were created artificially on the toosth enamel surface, then irradiated with Er,Cr:YSGG laser. Then, the resin-only and BG-based resins were infiltrated on the enamel surface. All samples were pH challenged for 14 days, and the micro-hardness, surface roughness, surface morphology, and color stability (ΔE) analyses were conducted before and after the 14 days pH challenge.

RESULTS

After laser irradiation, the micro-hardness was significantly high with 45S5 group compared to resin-only (p = 0.021), F-BG (p = 0.042), and B-BG (p = 0.001) groups. After the pH challenge, the micro-hardness values for all groups were reduced significantly (p ≤ 0.05). The surface roughness was least with the resin-only group and showed a non-significant difference with F-BG (p = 0.34) and significant differences with both B-BG (p = 0.005), and 45S5 (p = 0.010) groups. After the pH cycle, the roughness of all groups was increased significantly (p ≤ 0.05), except B-BG group showed a non-significant difference (p = 0.528). The B-BG group showed significantly high ΔE between day 0 and baseline compared to resin-only (p = 0.0008), F-BG (p = 0.017), and 45S5 (p = 0.029), whereas between day 14 and baseline, the lowest ΔE value was observed for B-BG (14.2 ± 2.10) and maximum for the resin-only (20.57 ± 2.47) group. The SEM images showed pitting on the surface of all resin infiltrant groups after 14 days of pH challenge.

CONCLUSION

The morphological difference was observed after the laser irradiation on the enamel surface. The differences in micro-hardness, surface roughness, and color were observed after the application of experimental resin infiltrants and significant differences were observed after the pH challenge.

Evaluation of the Demineralization Development around Different Types of Orthodontic Brackets

The aim of this study was to compare the demineralizations of the enamel surfaces around different types of orthodontic brackets in an artificial cariogenic environment. A total of 90 extracted human maxillary first premolar teeth were used in this in vitro study. The teeth were divided into 6 groups, 5 study and 1 control, each consisting of 15 samples. Victory metal, Gemini metal, Clarity self-ligating ceramic, APC Clarity Advanced ceramic and Clarity Advanced ceramic brackets (3M Unitek, Monrovia, Calif) used in the study groups were bonded to the teeth with the direct technique. The gingival, occlusal and proximal enamel surfaces adjacent to the brackets were measured with a DIAGNOdent pen (KaVo, Biberach, Germany) (T0). Then, the teeth were placed in a cariogenic suspension environment containing Streptococcus mutans, sucrose and artificial saliva. The teeth were removed from the cariogenic suspension at the end of 28 days. Enamel surfaces were remeasured with DIAGNOdent and the values were recorded (T1). Whether the obtained data were homogeneously distributed or not was determined by the Kolmogorov-Smirnov test, within-group comparisons were performed with the Wilcoxon test, and between-group comparisons were performed with Mann-Whitney U and Kruskal-Wallis tests. Significance level was accepted as p < 0.05. In all groups, the demineralization values of the enamel surfaces in the gingival, proximal and occlusal surfaces adjacent to the brackets were significantly higher in the T1 period than in the T0 period (p < 0.05). In the T1 period of Gemini metal, Clarity self-ligating ceramic and Clarity advanced ceramic bracket groups, the demineralization values of the proximal enamel surfaces were found to be significantly higher than the Victory metal and APC Clarity Advanced ceramic bracket groups (p < 0.05). In the T1 period, the demineralization values of the occlusal enamel surfaces of the Victory metal, APC Clarity Advanced ceramic bracket groups and control group were significantly lower than the Gemini metal, Clarity self-ligating ceramic and Clarity Advanced ceramic bracket groups (p < 0.05). Significant increases in enamel demineralization values were observed as a consequence of increased retention areas for microbial dental plaque on enamel surfaces adjacent to the bracket. Considering the importance of minimizing enamel demineralization in fixed orthodontic treatments, less enamel demineralization in Victory metal and APC Clarity Advanced ceramic bracket groups showed that these brackets can be preferred in patients with poor oral hygiene.

Shear bond strength of orthodontic molar tubes to composite restoration bonded with particular adhesives after different surface pre-treatments

OBJECTIVE

To evaluate in vitro the shear bond strength of orthodontic molar tubes to composite restoration bonded with particular adhesives after different surface pre-treatments.

SETTING AND SAMPLE POPULATION

The sample population is 60 extracted molars.

MATERIALS AND METHODS

After the teeth were thermocycled, they were randomly divided into six groups according to the adhesive and various surface pre-treatments that had been applied. The surface pre-treatments included sandblasting with 50-μm aluminium oxide particles and roughening with diamond bur and 37% phosphoric acid. Transbond XT Adhesive Primer (3M Unitek) (TXT) and Assure Plus (Reliance Orthodontic Products) adhesives were used in the study. Following the application of the adhesives, the brackets were bonded to the surfaces of the teeth. Shear bond strength was measured using a universal testing machine. Data were analysed with one-way ANOVA and LSD tests (P = .05). The adhesive remnant index (ARI) was determined using a stereomicroscope. Data from the ARI scores were submitted to Pearson's chi-squared test (P = .05).

RESULTS

The highest shear bond strengths were obtained in the Assure Plus group 15.05 ± 3.72 MPa after sandblasting (P < .05). The lowest shear bond strengths were found in the TXT group (7.52 ± 2.89 MPa; P < .05). Sandblasting and bur pre-treatment for TXT and Assure Plus adhesives increased shear bond strength in both of them. There were no significant differences in the ARI scores between the groups (P > .05).

CONCLUSION

Sandblasting and roughening pre-treatment can increase the bond strength of teeth with composite restoration. Assure Plus is also more effective than conventional adhesive systems.

The Use of Laser Energy for Etching Enamel Surfaces in Dentistry-A Scoping Review

BACKGROUND

In dental practice, different situations require etching the enamel layer. Acid etching, the present golden standard, may be replaced by other methods, such as laser etching. The main focus of our scoping review is to assess the existent literature regarding the effectiveness of different types of lasers, to identify the main aspects studied so far, and to understand where new search strategies are needed.

METHODS

The search was conducted in several databases focusing on the laser etching of human definitive enamel. We included English language articles published between January 2000 and December 2021.

RESULTS

The 34 articles reviewed showed that hard lasers, Er:YAG, Er,Cr:YAG, may represent an alternative etching method on enamel surfaces. They create a fractured, irregular surface and open dentin tubules, highly suitable for adhesion but with a lower risk of cavity formation. Nd:YAG, CO₂, and Diode lasers do not help in creating sufficient shear bond strength. There is, however, evidence suggesting that microcracks in the enamel layer may appear after thermomechanical ablation using laser energy.

CONCLUSIONS

While the use of acid etching is still successfully used for enamel conditioning, some researchers have emphasized the role played by saliva in the enamel-remineralization process a few days after the procedure. In this context, laser energy can be used, especially for bonding ceramic brackets in the case of orthodontic treatments. However, as thermomechanical ablation can generate microcracks, further research is required in order to establish clear findings concerning the use of laser energy on enamel etching.

Bond assessment of enamel conditioned with Er, Cr: YSGG laser and methylene blue photosensitizer activated by photodynamic therapy to orthodontic metallic brackets

AIM

To assess bond integrity and failure mode after enamel pretreated with conventional and contemporary conditioning methods were bonded to metallic brackets (MB).

MATERIAL AND METHODS

Forty maxillary central incisors were selected and disinfected. All specimens were mounted up to the cement-o-enamel junction and divided into four experimental groups randomly based on the enamel conditioning technique. Photodynamic therapy (PDT) was used to condition enamel in group 1, Total-etch and rinse (TER) was used to treat samples in group 2, Specimens in group 3 were conditioned with ECL, and samples in group 4 surface pretreated with SEP. Bonding of MB was performed on the surfaces of all the specimens with a Transbond XT. Specimens from all investigated groups were positioned on a universal testing machine maintaining buccal surfaces similar to the direction of the force. After bracket debonding bond failure was assessed using ARI. The bond integrity of all four groups was compared using analysis of variance (ANOVA). Post hoc Tukey test was used for pairwise comparison among different groups.

RESULTS

Group 2, TER+MB (15.38±0.14 MPa) displayed the highest bond value whereas the lowest values of SBS were exhibited by group 1, PDT+MB (10.11±0.17 MPa). The inter-group comparison revealed that specimens of group 2 and group 3, ECL+MB (14.61±0.55 MPa) demonstrated comparable bond strength (p>0.05).

CONCLUSION

Enamel conditioned with TER and ECL demonstrated comparable SBS. However, bond integrity after PDT and SEP (self-etch primer) surface treatment of enamel bonded with MB significantly lowered bond values.

Comparison of shear bond strength and ARI of four different adhesive systems used to bond molar tubes: An in vitro study

OBJECTIVE

The purpose of this in vitro study was to determine and compare the shear bond strength and ARI score of one traditional etch-and-rinse adhesive system serving as control, with those of two other all-in-one adhesives but with enamel acid etching preceding their application, and of one new 8th generation all-in-one bonding agent combined with a traditional adhesive used to bond stainless steel buccal tubes to molar teeth.

MATERIAL AND METHODS

Four groups of teeth were formulated according to the adhesive system used to bond the tubes on the molars. Shear bond strength was measured using a universal testing machine (Hounsfield, UK). After debonding, each enamel surface was imaged using Inspex HD l080p Vesa camera (Ash Technologies Ltd., Ireland) to determine the ARI score.

RESULTS

The mean SBSs in MPa for the four groups were respectively: A: 9.640 (±3.69), B: 10.261 (±3.03), C: 9.689 (±2.48), D: 8.412 (±3.02). No statistically significant differences were neither found through one-way ANOVA to exist between the group means (P: 0.715), nor for the ARI score frequence through Chi² (P: 0.534). Maxcem Elite showed four and G-Premio Bond zero instances of enamel fracture.

CONCLUSIONS

1. SBSs of all adhesives and ARI score distributions did not present any significant differences when used to bond stainless steel molar tubes. 2. All adhesives presented with acceptable shear bond strengths for clinical use. 3. Maxcem Elite under the tested conditions presented the greatest and G-Premio the least number of enamel fractures.