Journal of Dental Medicine

Background and Aim: Recycling of brackets can significantly reduce the price of fixed orthodontic appliances but if the bond is more prone to failure during treatment, this potential benefit will disappear. The aim of this study was to investigate the effect of chemical recycling on bond strength of metal orthodontic brackets and failure pattern of recycled brackets.

Material and Methods: In this experimental study Instron machine was used to measure shear bond strength (SBS) of brackets in two stages on 60 human maxillary first premolars using No-Mix composite. Shear bond strength and pattern of failure were compared between recycled and new brackets in two stages. Data were analyzed by ANOVA and Duncan tests. Adhesive Remnant Index was evaluated in different groups by Pearson Chi-square test. P<0.05 was considered as the limit of significance.

Results: Statistical analysis showed that the mean values of SBS for new bracket group was 12.00 MPa and for recycled group and double recycled group, 9.94Mpa and 10.00 MPa respectively. A significant reduction (about 18%) in bond strengths of brackets was observed at the first time of recycling. Recycling at the second time had no significant influence on the bond strength. Pattern of bond failure of these brackets showed that a great amount of residual adhesive material was remained on the teeth surfaces after debonding of recycled brackets which indicates that cleaning the teeth surfaces after debonding of recycled brackets is more time consuming.

Conclusion: Based on the results of this study, before using recycled brackets, several advantages and disadvantages must be considered.

Background and Aim: With the introduction of different bondable restorative materials in dentistry, various methods have been suggested to enhance the polymerization and shear bond strength of these materials. The aim of this study was to determine the effects of different methods of enamel conditioning on bond strength of orthodontic brackets and on the bracket/ adhesive failure mode.

Materials and Methods: In this experimental in vitro study, brackets were bonded to thirty-six bovine incisor teeth with different protocols according to the manufacturer's instructions as follows: Group 1: conventional multistep adhesive (n=12) Group 2: self-etching primer system (n=12) Group 3: acid+self-etching primer system (n=12). Specimens were loaded in a universal testing machine (Instron, Canton and Mass) and the mode of failure was recorded. Data were analyzed by ANOVA and Kruskall-Wallis tests with p<0.05 as the limit of significance.

Results: The mean shear bond strength was 11.7 ± 4.2, 10.5 ± 4.4, and 10.9 ± 4.8 MPa for group 1, 2, and 3 respectively. There was no significant difference in bond strength among the three groups (P=0.800). No significant difference was observed among the three groups with respect to residual adhesive on the enamel surfaces (P=0.554).

Conclusion: Based on the results of the present study, the use of self-etching primers may be an alternative to conventional phosphoric acid pre-treatment in orthodontic bonding.

Background and Aim: At the end of fixed orthodontic treatment, enamel damages are affected by amount of adhesive remnants. Thus, determining the factors involves in the amount of adhesive remnants e.g. the types of resins and the methods used for debonding is of necessity. The aim of this study was to evaluate the effect of the composite resin type and debonding pliers on enamel surface by a new method in measuring the adhesive remnant.

Materials and Methods: In this interventionally in-vitro study, 120 extracted human premolars were randomly divided into four groups of 30 each. The standard edgewise metal brackets were bonded on the teeth with two pastes self-cure composite "Concise" in the first and second groups, and with No-mix composite "Unite" in the third and fourth groups. the debonding was done by means of Lift off Debonding Instrument "LODI" (3M-Unitek), in first and third groups, and Bracket Removing Plier (Dentaurum), in the second and forth groups, respectively. After debonding, all teeth were evaluated with steriology software (stereolith version 1) for comparing the amount of adhesive remnants between the four groups. For data analysis, One-way ANOVA and independent t.test were used.

Results: The fourth group showed the lowest adhesive on the enamel surface and the most on the bracket surface with significant differences with other three groups (p<0.01).

Conclusion: The use of Dentaurum debonding plier with shear-peel force when used with the Unite adhesive (group 4), would decrease the adhesive remnants on the enamel surface.

Background and Aims: Considering the application of recycled metallic brackets in orthodontic treatments and probably more resultant metal ion release, which can cause cytotoxic side effects, this study was set up to assess the effect of recycling process of orthodontic brackets on metal ion release.
Materials and Methods: In this experimental study, 80 Discovery direct bond brackets (Dentarum, Germany) were divided into 2 groups, new and recycled brackets (n = 40), then each group was divided into two subgroups (one-week and 6-months subgroups) (n=20). The specimens were maintained in buffered solution of NaNHNo3 (pH=7) at 37°C in an incubator. After periods of one week and 6 months immersion, 0.5 mL of each solution was analyzed by spectrophotometry for the quantity of released Nickel (Ni), Chromium (Cr), and Cobalt (Co) ions. The data were analyzed using two way ANOVA analysis.
Results: After one week, the quantity of Ni, Cr, and Co ions released from new brackets were 0.65, 1.4, and 0.75 (ppb), respectively. The values for recycled brackets were 142, 2.61, and, 1.43 (ppb). These findings indicated significant difference between two groups (P<0.001). After six months, the quantity of Ni, Cr, and Co ions released from new brackets were 1200, 3.4, and 2.4 (ppb) and from recycled brackets were 2330, 6.9, and 10.8 (ppb), which showed significant difference between two groups (P<0.001).
Conclusion: Application of recycled brackets in long fixed orthodontic treatments can lead to metal ion release, specifically Nickel. Thus, the use of recycled brackets in long orthodontic treatments is not recommended.

  Background and Aims: The aim of this descriptive longitudinal study was to determine the type of teeth that were more prone in accidental bracket debonding and also to investigate the relationship between broken bracket bond and intervening factors such as age, type of malocclusion and sex.

  Materials and Methods: We used a pilot study to determine the correct sample size for this study. According to the pilot study which consisted of 20 records of patients, it was concluded that 576 patient’ records was needed. The mean time for a bracket before it fails was also measured using Kaplan-Meier method. Cox regression analysis was done to examine the effect of age, gender, and class of malocclusion on each tooth with broken bracket. Data were analyzed using the software SPSS 20.

  Results: Results showed that the percentage of unexpected broken bracket bond for each tooth varied and they were significantly related only in second premolars in both jaws with malocclusion that was different for each tooth (P=0.037, P=0.004).

  Conclusion: Maxillary second premolars and mandibular second premolars had the highest rate of unexpected broken bracket bond in CL II CL I malocclusion respectively. Age, gender and malocclusion had no effect on the unexpected broken bracket bond for other teeth.