TransbondTM XT Research Articles

The influence of cyclic shear fatigue on the bracket–adhesive–enamel complex: An in vitro study

ObjectivesTo describe the effect of fatigue on the strength of the bracket–adhesive–enamel complex and characterize the fatigue behavior of the materials tested. MethodsUpper central incisor brackets (Discovery®, Dentaurum) were bonded with a light-curing (Transbond XT™, 3M Unitek) and a chemically-curing adhesive (Concise™, 3M Unitek) on bovine teeth embedded in cylindrical resign bases and stored in water at 37(±2)°C for 24 (±2)h. The first 15 specimens were tested with a universal testing machine ZMART.PRO® (Zwick GmbH & Co. KG, Ulm, Germany) for ultimate shear bond strength according to the DIN-13990-2-standard. The remaining three groups of 20 specimens underwent fatigue staircase testing of 100, 1000 and 3000 cycles at 1Hz with a self-made testing machine. The survived specimens were subjected to shear strength testing. ResultsThe fatigued specimens showed decreased shear strength with both adhesives at all cycle levels. The shear strength after fatigue for 100, 1000 and 3000 cycles was in the Concise™-groups 34.8%, 59.0%, 47.3% and in the Transbond™ XT-groups 33.6%, 23.1%, 27.3% relative to the ultimate shear strength. The fatigue life of the Concise™-groups decreased with increasing stress and Transbond™ XT showed lower fatigue ratio with no obvious trend. The specimens bonded with Transbond™ XT showed typically favorable fracture modes in contrary to Concise™. SignificanceFatigue of the bracket–adhesive–enamel complex decreased its shear strength. The staircase method can provide a standardized experimental protocol for fatigue studies, however testing at various cycle numbers is recommended.

Evaluation of bovine and human teeth exposed to thermocycling for microleakage under bonded metal brackets

Bovine teeth are commonly used as substitutes for human teeth in scientific investigations. The present study was performed in vitro with the objective of comparing bovine and human enamel subjected to thermocycling for microleakage beneath metal brackets. A total of 50 bovine and human teeth (25 per group) void of defects or carious decay were extracted and stored in chloramine B (0.5%). A light-curing adhesive (Transbond™ XT) was used as instructed by the manufacturer (3M Unitek, Monrovia, CA, USA) to bond a metal bracket (discovery®; Dentaurum, Ispringen, Germany) to the surface of each tooth following 30 s of enamel etching (phosphoric acid 35%). After 24 h of dye penetration in methylene blue (0.5%), the cervical and incisal bracket surfaces were analyzed by light microscopy for excess bonding material, dye penetration, and microleakage at the bracket-adhesive and adhesive-enamel interfaces. Staining and evaluation was repeated after thermocycling (5000 cycles at 5/55 °C). Before thermocycling, the number of human teeth showing marginal gaps was one-third the number of bovine teeth (p<0.001). After thermocycling, the distribution of gaps was similar (p=0.180). The adhesive-enamel interface was most frequently affected (on 74% of human and 64% of bovine teeth). No dye penetration in either group after examining a horizontal slice through the bracket basis was observed. Immediately after bonding, less microleakage was observed around the base of metal brackets on human than bovine teeth. These marginal gaps were, however, superficial in both groups, none of them involving deep penetration of dye under the bracket base.

Effect of fluoride on tooth erosion around orthodontic brackets

The aim of the present study was to evaluate the effect of fluoride in prevention of tooth erosion around orthodontic brackets under erosive challenge. Edgewise brackets were bonded with Transbond™ XT composite on vestibular surface of 40 bovine incisors. The teeth were assigned to 4 groups (n=10): G1: Remineralizing saliva; G2: Erosive challenge; G3: Experimental group submitted to topical application of neutral fluoride gel (2% NaF) before erosive challenge; G4: Experimental group submitted to three daily applications of fluoride dentifrice (PFM 1500 ppmF) during erosive challenge. After 14 days of erosive challenge, direct visual and tactile examination were performed by two calibrated and trained examiners (Kappa = 0.867). The following scores were used: 0 = Intact enamel, 1 = Demineralized enamel without cavity, 2 = Demineralized enamel with cavity, 3 = Remineralized enamel without cavity, 4 = Remineralized enamel with cavity. Kruskal-Wallis and Mann-Whitney tests were applied to determine erosion levels, establishing a confidence interval of 95% (p<0.05). G2 and G3 presented 100% of score 2, with large cavities, presenting rough and opaque surface. G4 showed 50% of score 3 and 50% of score 4. Considering the studied conditions, it was found a significant difference between G2 and G4 and between G3 and G4 (p<0.01). By contrast to single application of neutral fluoride gel, the high frequency of use of fluoride at low concentration had a great influence during the dynamics of erosion.

Assessment of shear bond strength of brackets bonded by direct and indirect techniques: an in vitro study

OBJECTIVE: This in vitro study was designed to evaluate the shear bond strength (SBS) of orthodontic metal brackets bonded by direct and indirect techniques. METHODS: Thirty healthy human maxillary premolar teeth were used. The teeth were divided into three groups of 10 teeth each: Group I - indirect bonding with SondhiTM Rapid-Set system (3M/Unitek), Group II - indirect bonding with TransbondTM XT adhesive system (3M/Unitek) and Group III - direct bonding with TransbondTM XT adhesive system (3M/Unitek). After bonding and obtaining the specimens for the study, the specimens were subjected to SBS testing in a universal testing machine (Emic, model DL-500). The Kolmogorov-Smirnov test was applied to ascertain that the data had a normal distribution and the Bartlett test to check whether there was homogeneity of variance. One-factor analysis of variance was performed and, subsequently, Tukey's test for paired means. A 5% significance level was adopted. RESULTS: The results of Group I were 67.6 (N) and 5.9 (MPa); Group II, 68.9 (N) and 6.1 (MPa) and Group III (control), 92.5 (N) and 8.1 (MPa). CONCLUSION: It can therefore be concluded that the means for Group III were significantly higher compared with Groups I and II in both Newton (N) and Megapascal (MPa) values. The means attained by the indirect bonding technique used in Groups I and II, however, exhibited no statistically significant differences.

Atraumatic Restorative Treatment used for caries control at public schools in Piracicaba, SP, Brazil

Orthodontic appliances predispose to the accumulation of plaque due to the great number of retentive sites, which might lead to enamel demineralization adjacent to the accessories. Aim: To assess the effectiveness of a compomer for orthodontic bonding in preventing the formation of white spots around orthodontic brackets. Methods: Forty extracted human premolars were divided into two groups: control group (CG), in which conventional resin Transbond™ XT Light Cure (3M Unitek™) was used to bond the brackets; and experimental group (EG), in which the compomer Transbond™ Plus Color Change (3M Unitek™) was used. pH cycling was performed for 17 days to induce the demineralization process. Enamel on the buccal face was photographed under a stereomicroscope (at 10x magnification) before (t0) and after (t1) pH cycling. The images were used to compare demineralization between the groups by using a visual scale. Results: A statistically significant difference between control and experimental groups was found (p=0.004) showing that the compomer was more efficient than the conventional resin in preventing white spots. Conclusions: The compomer Transbond Plus Color Change was capable of inhibiting enamel demineralization adjacent to the bonding area of brackets. However, the inhibition halo did not exceed 1 mm.

Preventive effect of an orthodontic compomer against enamel demineralization around bonded brackets

Orthodontic appliances predispose to the accumulation of plaque due to the great number of retentive sites, which might lead to enamel demineralization adjacent to the accessories. Aim: To assess the effectiveness of a compomer for orthodontic bonding in preventing the formation of white spots around orthodontic brackets. Methods: Forty extracted human premolars were divided into two groups: control group (CG), in which conventional resin Transbond™ XT Light Cure (3M Unitek™) was used to bond the brackets; and experimental group (EG), in which the compomer Transbond™ Plus Color Change (3M Unitek™) was used. pH cycling was performed for 17 days to induce the demineralization process. Enamel on the buccal face was photographed under a stereomicroscope (at 10x magnification) before (t0) and after (t1) pH cycling. The images were used to compare demineralization between the groups by using a visual scale. Results: A statistically significant difference between control and experimental groups was found (p=0.004) showing that the compomer was more efficient than the conventional resin in preventing white spots. Conclusions: The compomer Transbond Plus Color Change was capable of inhibiting enamel demineralization adjacent to the bonding area of brackets. However, the inhibition halo did not exceed 1 mm.

Influence of saliva contamination on the shear bond strength of adhesives on enamel

OBJECTIVE: To evaluate shear bond strength of 3 adhesive systems (Single Bond, TransbondTM MIP and TransbondTM XT) applied on bovine enamel under saliva contamination condition. METHOD: One hundred and twenty enamel surfaces of bovine incisors were divided into 6 groups (n = 20) according to the adhesive system used (TransbondTM XT, TransbondTM MIP and Single Bond) with or without saliva contamination. For each adhesive system, there were two groups defined as no contamination group (NC): 37% H3PO4 conditioning for 30 seconds and two layers of adhesive systems; saliva contamination group (SC): After the first adhesive layer application, the examined areas were contaminated with saliva. Samples were mounted appropriately for testing and stored in deionized water at 37 oC for 7 days. Samples were then submitted to shear bond strength trials at a speed of 0.5 mm/min. The Adhesive Remnant Index (ARI) was evaluated under stereomicroscopy. Two-way analysis of variance and the Tukey test were used to compare mean values (α = 0.05). RESULTS: Groups XT (NC) = 26.29 ± 7.23; MIP (NC) = 24.47 ± 7.52 and SB (NC) = 32.36 ± 4.14 XT (SC) = 19.59 ± 6.76; MIP (SC) = 18.08 ± 6.39 and SB (SC) = 18.18 ± 7.03 MPa. ARI 0 and 1 were the most prevalent scores in all study groups examined. CONCLUSION: Saliva contamination significantly decreased bond strength of the three adhesive systems examined (p <0.05). However, the comparison of groups with and without saliva contamination did not reveal any significant differences, and, therefore, the three systems may be considered equivalent.

Rebonding of unused brackets with different orthodontic adhesives

OBJECTIVE: To compare in vitro shear bond strength (SBS) of different orthodontic adhesives in bonding and repeatedly rebonding metal brackets, and to evaluate the bond failure site with the adhesive remnant index (ARI). METHODS: Specimens consisted of 90 extracted human first premolars, randomly divided into three groups (n=30). The adhesives Alpha Plast (AP), ConciseTM (CO) and TransbondTM XT (TB) were used in each group. Three SBS tests were performed, i.e., one at T0 (initial) and the other two at T1 and T2 (first and second rebondings, respectively), observing a 24-hour interval. The tests were performed in a Shimadzu AG-I (10kN) SBS testing machine, at a speed of 0.5 mm/min. RESULTS: SBS data were subjected to ANOVA, Tukey's test and Bonferroni test (p<0.05). For the ARI, the Kruskal Wallis test was performed, followed by the Dunn test. The results revealed that at T0 groups AP and CO showed SBS values that were near, but above TB values; and at T1 and T2, the highest SBS values were observed for the AP group, followed by the CO and TB groups. CONCLUSION: Statistically significant differences were found in SBS between groups AP, CO and TB during bonding and repeated rebondings of unused metal brackets, with group AP achieving the highest SBS value. Regarding ARI, adhesive AP exhibited bond failure at the enamel-adhesive interface, with a higher enamel fracture frequency.

Evaluation of the effects of the bonding agent on acid-etched human enamel demineralization: in situ study

This in situ study evaluated the influence of the bonding agent on demineralization of acid-etched human enamel. Enamel blocks obtained from 20 human molars (four blocks per tooth) were divided into five groups. For the control groups, healthy control (HC, no treatment) and acid-etched control (EC, etching with 35 per cent phosphoric acid for 20 seconds), the specimens were obtained by sectioning in half, one block from each tooth. For the experimental groups, experimental etched group (EE), experimental Concise™ group (CE), and experimental Transbond™ group (TE), all specimens were etched with 35 per cent phosphoric acid for 20 seconds (EE) and treated with Concise™ enamel bond (CE) and Transbond™ XT primer (TE). Specimens from the experimental groups were fixed at intra-oral appliances wore by 10 volunteers and exposed to oral environment. After 28 days, the specimens were sectioned in the mesial-distal direction and the enamel cross-sectional Knoop hardness number (KHN, 50 g, 15 seconds) was measured at the cervical and occlusal regions at 25, 50, and 75 μm from the enamel surfaces. Data were analysed by analysis of variance (ANOVA) and Tukey honestly significantly different test for multiple comparisons (α = 0.05). Enamel KHN (P < 0.05) was recovered only in the Concise-treated group (CE; P < 0.05). When considering depth measurements, KHN results were 25 > 50 > 75 μm (P < 0.05). None of the groups exposed to the intra-oral environment for 28 days have recovered completely the enamel microhardness, but the order of improvement was better in the CE group than the TE group, the latter being only slightly better than the EE group.

Effects of three adhesion promoters on the shear bond strength of new and recycled orthodontic brackets—an in vitro study

Introduction This study was done to determine the effect of 3 adhesion promoters: Ortho Solo™ (Ormco), ALL-BOND 2® (Bisco), and Enhance L.C. (Reliance) on the shear bond strength of new and recycled orthodontic brackets and the amount of remnant adhesive on the teeth after debonding and to verify whether Enhance L.C. is material specific as stated by the manufacturer. Materials and Method This in vitro study was carried out on 120 premolar teeth which were bonded to 0.018 Roth premolar brackets. These teeth were divided into 6 groups of 20 with 2 subgroups—new group and recycled group. Brackets were bonded according to manufacturer's instructions: 1) Transbond™ XT 2) Transbond™ XT+ALL-BOND 2® 3) Transbond™ XT + Ortho Solo™ 4) Transbond™ XT + Enhance L.C. 5) Light Bond™ 6) Light Bond™ + Enhance L.C. Bond strength was tested on a universal testing machine and remnant adhesive on the tooth surface was determined. Kruskal-Wallis test and Mann-Whitney test were carried out to know the significant difference between the groups. Chi-square test was used to determine significant differences in the Adhesive Remnant Index (ARI) scores between the scores. Weibull analysis was performed to know the percentage of bracket failures among the groups tested. Results There was no significant difference between the groups with respect to the median load (p<0.001). Higher mean load was recorded in Group Via (Light Bond™ + Enhance L.C.) and least in Group lb (recycled with Transbond™ XT). Chi-square test showed no significant association between the ARI scores and the different groups. Conclusion Recycling brackets with Ashpol electropolishing liquid can serve them as new brackets in terms of the clinically acceptable bond strength. It is preferable to use Enhance L.C. with Light Bond™ when greater bond strength is required with new brackets.

In vitro Influence of Topical Fluoride Application on the Mechanical Properties of an Orthodontic Resin under pH Cycling

Objective: To evaluate the shear bond strength and the adhesive remnant index (ARI) of an orthodontic resin after in vitro pH cycling and topical fluoride application. Methods: Edgewise brackets were bonded with TransbondTM XT resin on the buccal of 40 bovine incisors. The teeth were divided in 4 groups (n=10): G1: pre cycling group (immediate shearing); G2: pos cycling group (pH cycling in the absence of fluoride); G3: experimental group with single topical application of neutral fluoride gel (2% NaF) before pH cycling; G4: experimental group with three daily applications of fluoride dentifrice (MFP 1500 ppmF) during pH cycling. Shear bond strength and ARI were evaluated after 14 days of pH cycling (acid saliva, pH 4.5). Shear bond strength data were analyzed by ANOVA and Tukey’s test while the Man-Whitney and Kruskal-Wallis were used for analysis of ARI data using a 95% confidence interval (p 0.05) in the shear bond strength among the groups. For the ARI analysis, 100% of the specimens of G1, G2 and G4, and 60% of G3 were scored 1, while 40% of the specimens of G3 were scored 2. There was statistically significant difference (p=0.029) between G1 and G3; G2 and G3; G3 and G4. Conclusion: Topical fluoride application concomitant to pH cycling did not exert influence on the shear bond strength of TransbondTM XT resin, but the use of neutral fluoride gel indicated a reduction in the risks of tooth fracture on debonding of orthodontic brackets, according to the ARI characteristics.

Comparative in vitro study of the shear bond strength of brackets bonded with restorative and orthodontic resins

The aim of this study was to evaluate the shear bond strength of brackets bonded with different restorative systems and compare it with that afforded by an established orthodontic bonding system. Seventy human bicuspids were used, divided into five different groups with 14 teeth each. Whereas a specific orthodontic bonding resin (Transbond™ XT) was used in the control group, the restorative systems Charisma, Tetric Ceram, TPH Spectrum and Z100 were used in the other four groups. Seven days after bonding the brackets to the samples, shear forces were applied under pressure in a universal testing machine. The data collected was evaluated using the ANOVA test and, when a difference was identified, the Tukey test was applied. A 5% level of significance was adopted. The mean results of the shear bond strength tests were as follows: Group 1 (Charisma), 14.98 MPa; Group 2 (Tetric Ceram), 15.16 MPa; Group 3 (TPH), 17.70 MPa; Group 4 (Z100), 13.91 MPa; and Group 5 or control group (Transbond™ XT), 17.15 MPa. No statistically significant difference was found among the groups. It was concluded that all tested resins have sufficient bond strength to be recommended for bonding orthodontic brackets.

Avaliação do efeito de tratamentos superficiais sobre a força de adesão de braquetes em provisórios de resina acrílica

OBJETIVO: avaliar a influência do tratamento de superfície de resinas acrílicas na resistência ao cisalhamento de braquetes colados com resina composta. MÉTODOS: foram confeccionados 140 discos de resina acrílica autopolimerizável (Duralay®), divididos aleatoriamente em 14 grupos (n=10). Em cada grupo, os corpos de prova receberam um tipo diferente de tratamento de superfície: grupo 1 = sem tratamento de superfície (controle); grupo 2 = silano; grupo 3 = jato de óxido de alumínio (JOA); grupo 4 = JOA + silano; grupo 5 = broca diamantada; grupo 6 = broca diamantada+ silano; grupo 7 = ácido fluorídrico; grupo 8 = ácido fluorídrico + silano; grupo 9 = ácido fosfórico; grupo 10 = ácido fosfórico + silano; grupo 11 = monômero de metilmetacrilato (MMA); grupo 12 = MMA + silano; grupo 13 = Plastic conditioner (Reliance®); grupo 14 = Plastic conditioner (Reliance®) + silano. Após o preparo de superfície, os corpos de prova foram analizados através da rugosimetria. Posteriormente, foram colados braquetes (Morelli®) de incisivo central "standard edgewise" com resina fotopolimerizável Transbond XT®; de acordo com as instruções do fabricante. RESULTADOS: o agente umectante à base de silano não teve um efeito estatisticamente significativo sobre os valores de força de adesão; os tratamentos com JOA e broca produziram maiores mudanças topográficas na superfície da resina acrílica, bem como os maiores valores de rugosidade; observou-se uma correlação não linear entre a força de adesão e a rugosidade de superfície; tratamentos com monômero e JOA resultaram nas maiores forças de adesão. CONCLUSÕES: o silano não foi capaz de aumentar a força de adesão entre braquete e resina acrílica. Sugere-se mais estudos sobre este tema, pois a força de adesão obtida foi muito baixa.

Influence of Enamel Conditioning on the Shear Bond Strength of Different Adhesives

Phosphoric acid etching is the gold standard for enamel conditioning. However, it is possible that air abrasion or a combination of air abrasion and etching might result in enhanced adhesion. The aim of this study was to investigate the effect of different enamel conditioning methods on the bond strength of six adhesives. Three different enamel conditioning procedures (phosphoric acid etching, air abrasion, air abrasion + phosphoric acid etching) were evaluated for their influence on the shear bond strength of six different adhesives (Transbond™ XT, Cool-Bond™, Fuji Ortho LC, Ultra Band-Lok, Tetric(®) Flow, Light-Bond™). Each group consisted of 15 specimens. Shear forces were measured with a universal testing machine. The scores of the Adhesive Remnant Index (ARI) were also analyzed. There were no significant differences between phosphoric acid etching and air abrasion + phosphoric acid etching. Air abrasion as a single conditioning technique led to significantly lower shear forces. The ARI scores did not correlate with the shear strengths measured. There were greater variations in shear forces for the different adhesives than for the conditioning techniques. The highest shear forces were found for the conventional composites Transbond™ XT and Cool- Bond™ in combination with conventional etching. Air abrasion alone and in combination with phosphoric acid etching showed no advantages compared with phosphoric acid etching alone and, therefore, cannot be recommended.

Effect of flexural strength of orthodontic resin cement on bond strength of metal brackets to enamel surfaces

Three types of experimental resin cements with different curing systems, dual, light, and chemical, were designed. The relationship between the flexural strengths of the three experimental and five commercial (Beauty Ortho Bond, Transbond™ XT, Light Cure Bond, Kurasper® F, and Super Bond) orthodontic resin cements on the tensile bond strength (TBS) and shear bond strength (SBS) of metal brackets to enamel was determined. Seven specimen bars of each resin were prepared for measuring the flexural strengths of the resins. Bonded specimens of each resin were prepared, seven for measuring TBS and seven SBS for after bonding of a metal bracket to a maxillary central human labial anterior tooth using experimental and commercial resin cements. The results were analysed by one-way analysis of variance and Scheffé's multiple comparison tests. The level of statistical significance was set at 0.05. Increases in the flexural strength of the resin cements were related to increases in the TBS and SBS of the metal bracket. While the light-curing cements exhibited a strong linear correlation between flexural strengths and TBS or SBS, the dual- and chemical-curing cements exhibited a different flexural strength effect on both TBS and SBS. This was a result of the adhesive layer under the metal bracket, which could be chemically cured, in contrast to the light-curing cement. To control setting time and to obtain higher initial TBS and SBS by polymerizing the resin cement under the bracket, a dual-curing system, that combines both light- and chemical-curing systems, is essential.

Evaluation of Bonded Orthodontics Brackets Using Different Adhesive Systems after a Cariogenic Challenge

The aims of this study were to evaluate the prevention of enamel demineralization and the shear bond strength (SBS) of orthodontic brackets bonded with fluoride and no fluoride conventional and self-etching adhesives and to analyze the characteristics of enamel near the bond area using a polarized light microscope (PLM) following demineralization and remineralization cycling (Des Re). Fifty bovine incisors were selected and divided into five groups according to the adhesive system used during the bonding process: G1, Transbond XT Adhesive; G2, Single Bond 2 Adhesive; G3, Optibond Solo Plus; G4, Clearfil SE Bond; and G5, Clearfil Protect Bond. Transbond XT was used to fix the brackets to the teeth in all groups. After bonding, the groups were separated into cycling and control subgroups. The specimens were submitted to SBS testing and evaluated under a PLM. The results were submitted to ANOVA and Tukey's post hoc tests (p<.05). There were no significant differences for SBS after Des-Re cycling. The Clearfil Protect Bond showed the SBS to be statistically lower than the other adhesives used for the control groups. After a cariogenic challenge, the Single Bond adhesive showed an SBS significantly lower than Transbond XT. The Des-Re cycling increased the enamel demineralization induced after the cariogenic challenge. The cariogenic challenge did not reduce the SBS. Optibond Solo Plus and Transbond XT adhesives presented the highest SBS while Clearfil Protect Bond had the lowest. The PLM showed that the cariogenic challenge increased the enamel demineralization for all adhesives evaluated, independent of the presence of fluoride. An alternative material with the ability to prevent enamel demineralization should be used in orthodontic patients due to the higher accumulation of plaque around orthodontic brackets.

Micro-tensile bond strength to surface and subsurface enamel

Testing of bond strength to enamel has been undertaken on both surface and subsurface enamel on the assumption that it is the same substrate. Over recent years, the micro-tensile method has become widely used for the evaluation of dental adhesives. However, there have been no micro-tensile bond strength studies comparing surface and subsurface enamel using orthodontic adhesives. It has been proposed that the bond strength to subsurface enamel is greater than that to surface enamel. Objective The micro-tensile bond strength (MTBS) of Transbond (light activated paste, 3 M Unitek, USA) to surface and subsurface enamel was investigated. Methods Ten sound freshly extracted lower human first molars were divided into two groups of five each. Surface enamel of the first group was removed with 500-grit silicone carbide paper, whilst in the second group it was left intact. Gelatin capsules filled with Transbond composite paste were bonded perpendicular to the enamel using light cure adhesive Primer (Transbond™ XT, 3 M Unitek, USA) in both groups, and stored in distilled water at 37 °C for 24 h. Crowns of all specimens were sectioned bucco-lingually into vertical slabs of approximately 0.6 mm thickness. Slabs in each group were prepared into an hourglass shape of 1 mm width and 0.6 mm thickness. Micro-tensile bond strength was determined using a mini tensile testing machine (COMPACT Gauge, DILLON). Results Mean values of MTBS were: 31.2 MPa (SD14.5) for surface enamel and 47.9 (SD15.0) for subsurface enamel. Significance There was a significant difference between the two groups P = 0.001. It was concluded that subsurface enamel has significantly higher bond strength than surface enamel. This has implications for bonding in restorative dentistry and orthodontics.