Effects of adhesion promoter on orthodontic bonding in fluorosed teeth: A scanning electron microscopy study

Correlation of Shear Bond Strength and Degree of Conversion in Conventional and Self-Adhesive Systems Used in Orthodontic Bonding Procedures

(1) Background: Self-adhesive systems have been proposed for the orthodontic bonding with the intention to reduce the traditional three-component system. (2) Methods: The sample consisted of 32 extracted intact permanent premolars randomly divided into two groups (n = 16). In Group I the metal brackets were bonded with Transbond XT Primer and Transbond XT Paste. In Group II the metal brackets were bonded with GC Ortho connect. The resin was polymerized for 20 s from two directions (mesial and occlusal) using a Bluephase light-curing unit. The shear bond strength (SBS) was measured using a universal testing machine. Immediately after SBS testing, Raman microspectrometry was performed for each sample to calculate the degree of conversion (DC). (3) Results: There was no statistically significant difference in the SBS between the two groups. A significantly higher DC (p < 0.001) value was recorded in Group II, in which the brackets were bonded with GC. Very weak or no correlation (0.01) was recorded between SBS and DC in Group I and moderate positive correlation was recorded in Group II (0.33). (4) Conclusions: No difference was found in SBS between the conventional and two-step systems used in orthodontics. The two-step system demonstrated higher DC compared to the conventional system. There is a very weak or moderate correlation between DC and SBS.

Effects of fluorosed enamel on orthodontic bracket bonding : An in vitro study

OBJECTIVE

To investigate the effect of enamel deproteinization and air abrasion on shear bond strength (SBS), adhesive remnant index (ARI) scores, and surface topography when bonding orthodontic brackets to fluorosed enamel.

MATERIALS AND METHODS

The sample included 90 fluorosed and 30 normal premolars divided into four groups: group I (fluorosed premolars subjected to air abrasion before acid etching), group II (fluorosed premolars subjected to deproteinization before acid etching), group III (fluorosed premolars; control for groups I and II), and group IV (normal premolars; control for group III). Bonding procedures included etching with 37% phosphoric acid, priming with Transbond^TM XT primer (3M Unitek, Monrovia, CA, USA), and application of Transbond^TM XT adhesive paste (composite; 3M Unitek, Monrovia, CA, USA). Air abrasion was done using 50 µm aluminum oxide particles under 0.28 MPa pressure for 5 s with the micro-etcher held at a distance of 10 mm. Deproteinization was done for 60 s with 5% sodium hypochlorite (NaOCl).

RESULTS

Fluorosed premolars subjected to deproteinization showed the lowest (median = 6.57 MPa) SBS among the four groups, followed by 8.14, 8.90, 8.14 MPa for groups I, III, and IV respectively. ARI scores were significantly different between the four groups (p = 0.006). Fluorosed enamel etched after air abrasion or deproteinization with NaOCl showed a predominance of type 4 etching pattern with some areas appearing unetched.

CONCLUSIONS

Shear bond strength of all groups was within the 6-8 MPa acceptable range for orthodontic purposes. Fluorosed premolars subjected to deproteinization showed the lowest values. Further studies are recommended to scrutinize the deproteinization technique.

Comparison of the shear bond strength of reconditioned metal brackets used in indirect bonding: an in vitro pilot study

Objectives:

This study aimed to compare the shear bond strength (SBS) related to surface treatment methods of debonded brackets before indirect rebonding and to evaluate changes in SBS related to sandblasting time.

Methods:

After brackets were debonded from a dental cast during an indirect bonding procedure, seven groups were assigned to conduct SBS tests. Sandblasted groups were sprayed with Al2O3 for 3 s (Group II), 6 s (Group III), 9 s (Group IV), and 12 s (Group V). In Group VI, a no. 4 round low-speed bur was used to remove resin. In Group VII, the bracket base was coated with a plastic conditioner (Reliance, IL, USA) and Group I served as the control group.

Results:

The SBS of Group VII was not statistically different from that of the control group. The SBS of Group VI was not statistically different from that of Group II but higher than that of the control group (P < 0.05). There was no statistical difference between Groups III, IV, and V, but was greater than the other groups (P < 0.05).

Conclusion:

The group with surface treatment by sandblasting for more than 6 sec prior to indirect bonding recorded a higher SBS than the other groups. The SBS did not increase further even if the sandblasting time increased by more than 9 sec.

Comparison of shear bond strength of orthodontic brackets bonded to human teeth with and without fluorotic enamel: a systematic review and meta-analysis of experimental in vitro studies

OBJECTIVE

The aim of this systematic review was to compare the shear bond strength (SBS) of orthodontic brackets bonded to human teeth with and without enamel fluorosis (EF) using conventional bonding interventions/techniques.

MATERIALS AND METHODS

An unrestricted search of indexed databases was performed with the following eligibility criteria: (a) human fluorotic teeth (experimental-group); (b) human teeth without fluorosis (control-group); (c) studies using phosphoric acid (PA) etching without air abrasion (AA), PA etching combined with AA, and application of self-etching primer (SEP) alone as bonding interventions/techniques; and (d) measuring SBS in megapascals (MPa). Data screening, selection, and extraction were performed by two reviewers. The risk of bias (rob) was assessed using the JBI Critical appraisal tool for Quasi-Experimental Studies. Meta-analyses were performed using a random effects model. The quality of available evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation approach.

RESULTS

Ten in vitro studies were included. Subgroup analyses were performed for each intervention type. The SBS was significantly lower in fluorotic teeth when PA was used without AA (mean difference = 3.26 MPa, confidence interval: [1.00, 5.52]); and there were no significant differences for the PA combined with AA, and SEP interventions. All studies had a low rob. The overall level of evidence was at best low.

CONCLUSIONS

The SBS is lower in teeth with EF when traditional PA is used. No significant differences were found in SBS between teeth with and without EF when PA is used with AA or when SEP is used alone.

Effect of Adhesion Boosters on the Indirect Bonding with the Lingual Brackets: An In Vitro Study

Aims and Objectives:

To evaluate the influence of the two adhesion boosters (assure universal bonding resin and enhance adhesion booster) on the shear bond strengths of indirectly bonded lingual brackets.

Materials and Methods:

A total of 120 extracted human teeth were randomly divided into 3 groups (n = 40), each group contained equal number of anterior and posterior teeth (anterior = 20, posterior = 20), and their lingual surfaces were etched by using 37% phosphoric acid. The bracket was bonded indirectly without using adhesion booster in group 1 (control group). In group 2, the adhesion booster A (enhance adhesion booster) and adhesion booster B (assure universal bonding resin) in group 3 were applied, respectively, before the bonding. The universal testing machine was used to measure the maximum bond strength. Student’s t-test followed by the one-way analysis of variance was used to compare shear bond strength among the groups.

Results:

The shear bond strength was found to be highest in group 3, followed by group 2, and it was least in controls. There were highly significant differences statistically in shear bond strength among the groups 1, 2, and 3 ( P = .001).

Conclusion:

Shear bond strength was admissible in all the groups. The application of the assure universal bonding resin significantly increased the bond strength of lingual brackets in indirect bonding.

Bracket bonding to polymethylmethacrylate-based materials for computer-aided design/manufacture of temporary restorations: Influence of mechanical treatment and chemical treatment with universal adhesives

Objective

To assess shear bond strength and failure mode (Adhesive Remnant Index, ARI) of orthodontic brackets bonded to polymethylmethacrylate (PMMA) blocks for computer-aided design/manufacture (CAD/CAM) fabrication of temporary restorations, following substrate chemical or mechanical treatment.

Methods

Two types of PMMA blocks were tested: CAD-Temp® (VITA) and Telio® CAD (Ivoclar-Vivadent). The substrate was roughened with 320-grit sandpaper, simulating a fine-grit diamond bur. Two universal adhesives, Scotchbond Universal Adhesive (SU) and Assure Plus (AP), and a conventional adhesive, Transbond XT Primer (XTP; control), were used in combination with Transbond XT Paste to bond the brackets. Six experimental groups were formed: (1) CADTemp®/SU; (2) CAD-Temp®/AP; (3) CAD-Temp®/XTP; (4) Telio® CAD/SU; (5) Telio® CAD/AP; (6) Telio® CAD/XTP. Shear bond strength and ARI were assessed. On 1 extra block for each PMMA-based material surfaces were roughened with 180-grit sandpaper, simulating a normal/medium-grit (100 mm) diamond bur, and brackets were bonded. Shear bond strengths and ARI scores were compared with those of groups 3, 6.

Results

On CAD-Temp® significantly higher bracket bond strengths than on Telio® CAD were recorded. With XTP significantly lower levels of adhesion were reached than using SU or AP. Roughening with a coarser bur resulted in a significant increase in adhesion.

Conclusions

Bracket bonding to CAD/CAM PMMA can be promoted by grinding the substrate with a normal/medium-grit bur or by coating the intact surface with universal adhesives. With appropriate pretreatments, bracket adhesion to CAD/CAM PMMA temporary restorations can be enhanced to clinically satisfactory levels.

Impact of Fluorosis on the Tensile Bond Strength of Metal Brackets and the Prevalence of Enamel Microcracks

The objective of this in vitro study was to determine the effects of dental fluorosis on the tensile bond strength of metal brackets bonded to human teeth and to evaluate the changes in the tooth enamel surface after debonding. The study sample consisted of 68 recently extracted human upper premolars, which were divided into 2 groups: the fluorosis group (34 fluorosed teeth) and the control group (34 healthy teeth). Identical premolar metal brackets were bonded on the buccal surfaces of the teeth. Both groups were submitted to a tension test using a universal testing machine. The number and length of the enamel microcracks in the buccal surface of each tooth were determined before bracket bonding and after debonding using a stereomicroscope. The percentage adhesive remnant index (PARI) was calculated after debonding. The results showed that the tensile bond strength (TBS) of brackets bonded to fluorosed teeth was 21.08% lower than that of brackets bonded to healthy teeth (p < 0.0001). The length of the enamel microcracks on fluorosed teeth increased by 47.4% after debonding, whereas the control group showed an increase of only 12.6%. The PARI showed lower values for fluorosed teeth in comparison to the control group (p = 0.047). In conclusion, dental fluorosis has a negative impact on tensile bond strength and the length of microcracks formed after bracket debonding.