The extent of enamel surface fractures. A quantitative comparison of thermally debonded ceramic and mechanically debonded metal brackets by energy dispersive micro- and image-analysis

Single-component orthodontic adhesives: comparison of the clinical and in vitro performance

OBJECTIVES

To investigate the clinical and in vitro performance of single-component orthodontic adhesives under metal brackets.

MATERIALS AND METHODS

Bimaxillary orthodontic treatment was required for sixty patients and 60 premolar teeth were divided into three groups (n: 20). The single-component orthodontic adhesives Biofix and GC Ortho Connect (GC) that did not require primers were compared to the control group using Transbond XT, which was applied with a primer. For each patient, total bonding time was measured. The Adhesive Remnant Index (ARI_(Bracket)) score was noted over 12 months. In vitro tests were used to evaluate specimens, shear bond strength (SBS), ARI_(Bracket), and Enamel Surface Index (ESI). After in vitro debonding, the enamel surface and bracket base were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX).

RESULTS

Clinical failure rate with primer was 9.0%, while it was 8.0 and 10.0 for GC and Biofix, respectively. The mean in vitro SBS values of the Biofix, GC, and Transbond XT groups were 8.21, 8.07, and 7.37 MPa, respectively. There were no statistically differences in clinical failure (p = 0.160) and SBS values (p = 0.158). Mean differences in bond-up time per jaw were 9.65, 10.51, and 11.97 min, which were statistically significant (p = 0.0001).

CONCLUSION

Single-component adhesives had acceptable SBS values and enamel effects according to SEM-EDX analysis. Clinically, bonding failure was not shown statistically inferior to bonding with primer. There was also a significant difference in bond-up times.

CLINICAL RELEVANCE

Considering an intensely working clinic with bonding processes for at least two jaws per day, this means a saving of the chair time of 1 patient per week. However, better saliva contamination and moisture control with lack of the primer stage and, thereby, an acceptable bracket failure rate will bring clinically significant results with less chair time for clinicians.

The use of the laser confocal scanning microscopy to measure resin remnants on customized lingual bracket

Background

The study aimed to evaluate the permanence of resin and enamel remains on lingual brackets at the end of orthodontic treatment and after the debonding procedure. The evaluation of resin remnants on customized lingual brackets bases has never done before in other studies because they are curved, and traditional techniques are not applicable.

Methods

The sample consisted of 100 lingual brackets (25 incisors, 25 canines, 25 premolars, 25 molars) scanned with a confocal laser microscope (OLS4000). We measured the brackets' surface and the area of resin remnants with the software of the microscope. Median and quartiles were presented to describe the data. ARI calculation was indirect for each tooth, measuring the resin remnants to the total surface of the bracket. The Kruskal-Wallis test and Fisher test were applied respectively to compare the percentages of remnants and the frequencies of the ARI between the four groups.

Results

After the analyses, 13 brackets had no adhesive remnants (ARI 0), 29 brackets had less than 50% of resin remnants (ARI 1), 50 brackets had more than 50% of resin remnants (ARI 2), and 8 brackets had 100% of adhesive (ARI 3). Canines brackets presented the lower amount of resin followed by premolars, incisors, and molars.

Conclusion

Lingual brackets showed a high frequency of ARI = 2. The median percentage of the bracket surface covered by resin was 41%. We observed a slight tendency of more resin remnants on molar brackets, due to half-pad configuration. The authors suggest paying attention during the debonding procedure of molar brackets since a stronger connection between the adhesive and the bracket mesh means a higher risk of enamel damage.

Comparative three-dimensional analysis of initial biofilm formation on three orthodontic bracket materials

INTRODUCTION

The purpose of the present study was to investigate and compare early biofilm formation on biomaterials, which are being used in contemporary fixed orthodontic treatment.

METHODS

This study comprised 10 healthy volunteers (5 females and 5 males) with a mean age of 27.3 +-3.7 years. Three slabs of different orthodontic materials (stainless steel, gold and ceramic) were placed in randomized order on a splint in the mandibular molar region. Splints were inserted intraorally for 48 h. Then the slabs were removed from the splints and the biofilms were stained with a two color fluorescence assay for bacterial viability (LIVE/DEAD BacLight-Bacterial Viability Kit 7012, Invitrogen, Mount Waverley, Australia). The quantitative biofilm formation was analyzed by using confocal laser scanning microscopy (CLSM).

RESULTS

The biofilm coverage was 32.7 ± 37.7% on stainless steel surfaces, 59.5 ± 40.0% on gold surfaces and 56.8 ± 43.6% on ceramic surfaces. Statistical analysis showed significant differences in biofilm coverage between the tested materials (p=0.033). The Wilcoxon test demonstrated significantly lower biofilm coverage on steel compared to gold (p=0.011). Biofilm height on stainless steel surfaces was 4.0 ± 7.3 μm, on gold surfaces 6.0 ± 6.6 μm and on ceramic 6.5 ± 6.0 μm. The Friedman test revealed no significant differences between the tested materials (p=0.150). Pairwise comparison demonstrated significant differences between stainless steel and gold (p=0.047).

CONCLUSION

Our results indicate that initial biofilm formation seemed to be less on stainless steel surfaces compared with other traditional materials in a short-term observation. Future studies should examine whether there is a difference in long-term biofilm accumulation between stainless steel, gold and ceramic brackets.

Three-dimensional quantitative analysis of adhesive remnants and enamel loss resulting from debonding orthodontic molar tubes

AIMS

Presenting a new method for direct, quantitative analysis of enamel surface. Measurement of adhesive remnants and enamel loss resulting from debonding molar tubes.

MATERIAL AND METHODS

Buccal surfaces of fifteen extracted human molars were directly scanned with an optic blue-light 3D scanner to the nearest 2 μm. After 20 s etching molar tubes were bonded and after 24 h storing in 0.9% saline - debonded. Then 3D scanning was repeated. Superimposition and comparison were proceeded and shape alterations of the entire objects were analyzed using specialized computer software. Residual adhesive heights as well as enamel loss depths have been obtained for the entire buccal surfaces. Residual adhesive volume and enamel loss volume have been calculated for every tooth.

RESULTS

The maximum height of adhesive remaining on enamel surface was 0.76 mm and the volume on particular teeth ranged from 0.047 mm3 to 4.16 mm3. The median adhesive remnant volume was 0.988 mm3. Mean depths of enamel loss for particular teeth ranged from 0.0076 mm to 0.0416 mm. Highest maximum depth of enamel loss was 0.207 mm. Median volume of enamel loss was 0.104 mm3 and maximum volume was 1.484 mm3.

CONCLUSIONS

Blue-light 3D scanning is able to provide direct precise scans of the enamel surface, which can be superimposed in order to calculate shape alterations. Debonding molar tubes leaves a certain amount of adhesive remnants on the enamel, however the interface fracture pattern varies for particular teeth and areas of enamel loss are present as well.

Comparison of shear bond strength of plastic and ceramic brackets

OBJECTIVES

The purpose of this in vitro study is to compare the shear bond strength of various esthetic brackets used in conjunction with two different adhesive systems.

METHODS

Five non-silanized ceramic brackets (Aspire Gold/Forestadent, Clarity™/3M Unitek, CLEAR/Adenta, Contour Twin/ODS, QuicKlear/Forestadent) and four plastic brackets (Aesthetik-Line®/Forestadent, Brillant®/Forestadent, Composite Clear®/ODS, Elegance®/Dentaurum) were bonded either with Transbond™ XT (3M Unitek, Monrovia, CA, USA) or with ConTec SE (Dentaurum, Ispringen, Germany) to bovine permanent mandibular incisors. Twelve specimens were tested in each group, thus, bonding 60 ceramic and 48 plastic brackets with either adhesive to a total of 216 teeth. Shear bond strength was measured in accordance with the DIN 13990-2 standard governing test methods for the entire attachment-adhesive-enamel system. The fracture surfaces resulting from shear-induced debonding were analyzed via light microscopy.

RESULTS

The combinations Clarity™ + Transbond™ XT, CLEAR® + Transbond™ XT, and Contour Twin + Transbond™ XT exhibited shear bond strengths of over 10 MPa. The Adhesive Remnant Index scores of the various bracket types varied widely according to the different bracket-base designs. No enamel fractures were observed.

CONCLUSION

Some bracket-adhesive combinations in this study attained shear bond strengths approaching those of metal brackets. The risk of debonding-related enamel defects is comparable with different esthetic bracket combinations. Manufacturers' recommendations for the adhesive systems to be used with their brackets should be strictly adhered to.

Periodontal ligament strain induced by different orthodontic bracket removal techniques: nonlinear finite-element comparison study

OBJECTIVES

The goal of this work was to biomechanically analyze several different methods of bracket debonding and compare the strain they induce in the periodontal ligament (PDL).

METHODS

The CT dataset of an anatomical specimen was divided into four segmental models of the mandible. Each model covered one tooth (32, 42, 44, and 47). One of these teeth (32) was characterized by marked loss of periodontal attachment. After suitable finite-element models were generated, material properties were defined as nonlinear for PDL and anisotropic for the alveolar bone. This was followed by simulating four bracket debonding techniques: frontal and lateral torquing, bracket-wing compression, and shear stress applied with specially designed pliers.

RESULTS

The greatest strain was measured at the periodontally compromised tooth site 32 in response to frontal and lateral torquing. Both techniques also resulted in great strain around the other three teeth. Strain was markedly lower with the shear technique and virtually negligible with the compression technique. All simulated tooth sites confirmed the PDL-sparing effect of bracket-wing compression.

CONCLUSION

The severity of PDL strain during orthodontic bracket removal depends on the debonding method used. The technique of compressing the bracket wings appears to trigger the smallest effect on PDL. Clinical studies should be undertaken to confirm these findings.

In vitro analysis of shear bond strength and adhesive remnant index comparing light curing and self-curing composites

OBJECTIVE

To evaluate, in vitro, the shear bond strength of self-curing (ConciseTM - 3M and Alpha Plast - DFL) and light-curing composites (TransbondTM XT - 3M and Natural Ortho - DFL) used in orthodontics bonding, associated to Morelli metal brackets, with further analysis of adhesive remnant index (ARI) and enamel condition in scanning electron microscopy (SEM).

METHODS

Forty human premolars, just extracted and stored in physiologic solution 0.9 % were used. Randomly, these samples were divided in four groups: G1 group, the brackets were bonded with ConciseTM - 3M composite; in G2 group, Alpha Plast - DFL composite was used; in G3 group, TransbondTM XT - 3M was used; in G4 group, Natural Ortho - DFL composite was used. These groups were submitted to shear strength tests in universal testing machine, at 0.5 mm per minute speed.

RESULTS

Statistical difference between G3 and G4 groups was recorded, as G4 showing higher strength resistance than G3. In the other hand, there were no statistical differences between G1, G2 and G3 and G1, G2 and G4 groups. ARI analysis showed that there was no statistical difference between the groups, and low scores were recorded among then. The scanning electron microscopy (SEM) analysis revealed the debonding spots and the enamel surface integrity.

CONCLUSIONS

Shear bond strength was satisfactory and similar between the composites, however Natural Ortho - DFL revealed best comparing to TransbondTM XT - 3M.

Orthodontic bracket debonding: risk of enamel fracture

OBJECTIVES

Until now, it is not clear if various procedures of bracket debonding differ with regard to their risk of enamel fracture. Therefore, the objective of the present study was to compare these procedures biomechanically for assessing the risk of complications.

MATERIALS AND METHODS

An anisotropic finite element method (FEM) model of the mandibular bone including periodontal ligament, enamel, dentin, and an orthodontic bracket was created. The morphology based on the CT data of an anatomical specimen. Typical loading conditions were defined for each method of bracket debonding (compression, shearing off, twisting off). Shortly before the adhesive's break, the induced stress in enamel, periodontal ligament, and in the alveolar bone was measured. The statistical analysis of the obtained values was performed in SPSS 19.0.

RESULTS

Relatively high stresses occurred in the enamel using frontal torque (max. 44.18 MPa). With shearing off, the stresses were also high (max. 41.96 MPa), and additionally high loads occurred on the alveolar bone as well (max. 11.79 MPa). Moderate maximum values in enamel and alveolar bone appeared during the compression of the bracket wings (max. 37.12 MPa) and during debonding by lateral torque (max. 35.18 MPa).

CONCLUSIONS

The present simulation results indicate that the risk of enamel fracture may depend on the individual debonding procedure. Further clinical trials are necessary to confirm that.

CLINICAL RELEVANCE

For patients with prior periodontal disease or loosened teeth, a debonding procedure by compression of the bracket wings is recommended, since here the load for the periodontal structures of the tooth is lowest.