Influence of Primer Pre-curing and Co-curing on Shear Bond Strength of Orthodontic Brackets Using Three Light-cure Adhesive Systems: An In Vitro Study.

AIM: This study aimed to evaluate the shear bond strength (SBS) of orthodontic brackets with primer pre-curing and co-curing using three light cure adhesive systems. MATERIALS AND METHODS: In this in vitro study, 102 extracted premolar teeth mounted on self-cure acrylic resin blocks were separated into six groups based on primer pre-curing and co-curing with each group receiving stainless steel orthodontic premolar brackets bonded to the buccal surfaces. The following adhesives were used: Transbond XT (3M Unitek, CA, USA), Orthofix (Anabond Stedman, India), and Enlight (Ormco, India). In the groups with pre-curing, the primer was pre-cured for 20 seconds while in the groups with co-curing, the primer and adhesive were cured together. Shear bond strength tests and Adhesive Remnant Index (ARI) were assessed followed by an scanning electron microscope (SEM) view (×3000) of the enamel surface after debonding. Statistical analysis was done using a one-way analysis of variance (ANOVA) test. RESULTS: The descriptive statistics in the pre-cured groups showed a statistically significant difference. The highest mean SBS was observed for group I, i.e., Transbond XT with primer pre-curing (20.56 ± 3.22 MPa). The lowest mean SBS was for group IV, i.e., Orthofix with primer co-curing (7.57 + 0.49 MPa). The results of ANOVA revealed a significant difference among the groups. The ARI scoring and the SEM analysis also confirmed this finding. CONCLUSION: Shear bond strength of orthodontic brackets with primer pre-curing showed a better bond strength than brackets with co-curing. The ARI data suggested that the majority of bracket failure happened at the resin-bracket interface. Scanning electron microscope analysis also confirmed the ARI and SBS findings. CLINICAL SIGNIFICANCE: During the bonding of orthodontic brackets, the primer can be co-cured where the primer and adhesive resin are cured simultaneously or pre-cured where the primer is cured separately. Most orthodontic clinicians to save time co-cure primer. Both these methods affect the SBS of brackets.

Effect of Different Light-tip Distances on Shear Bond Strength of Orthodontic Brackets Cured with Light-emitting Diode and High-intensity Light-emitting Diode.

AIM: The aim was to find out whether the light-tip distance affected the shear bond strength of orthodontic brackets when cured with light-emitting diode (LED) and high-intensity LED at four different light-tip distances. MATERIALS AND METHODS: Extracted human premolars were divided into eight groups. Each tooth was embedded in the self-cure acrylic resin block, and brackets were bonded and cured with different lights and different distances. Shear bond strength tests were performed in vitro using the universal testing machine. Data were analyzed using one-way ANOVA test. RESULTS: The descriptive statistics for shear bond strength of orthodontic brackets cured with LED light at 0 mm was 8.49 ± 1.08 MPa, at 3 mm was 8.13 ± 0.85 MPa, 6 mm was 6.42 ± 0.42 MPa, and at 9 mm was 5.24 ± 0.92 MPa, and those cured with high-intensity light at 0 mm was 19.23 ± 4.83 MPa, at 3 mm was 17.65 ± 3.28 MPa, at 6 mm was 13.04 ± 2.36 MPa, and at 9 mm was 11.74 ± 1.4 MPa. Mean shear bond strength was found to decrease as the light-tip distance increased with both light sources. CONCLUSION: Shear bond strength is higher when the light source is close to the surface to be cured, and it decreases as the distance increases. The highest shear bond strength was achieved with high-intensity light. CLINICAL SIGNIFICANCE: Light-emitting diode or high-intensity units can be used for bonding orthodontic brackets without compromising the shear bond strength of the brackets, and that shear bond strength is stronger when the light source is close to the surface to be cured, and it decreases as the distance increases between the light source and the surface.

Effect of Displacement of Bracket Position after Initial Placement on Shear Bond Strength: An In vitro Study.

CONTEXT: Displacement of bracket after initial placement on tooth surface in the precure phase of bonding influences the shear bond strength. AIMS: The aim of this study was to evaluate the influence of bracket displacement during the precure phase after initial placement on the tooth surface on shear bond strength of chemical cure and light cure composites. SETTINGS AND DESIGN: In vitro experimental study. SUBJECTS AND METHODS: Stainless steel orthodontic premolar brackets were bonded to the buccal surfaces of 88 maxillary 1st premolar teeth. Teeth were divided into four groups: (1) Group 1 - Control group for light-cure composites, (2) Group 2 - Displacement group for light-cure composites, (3) Group 3 - Control group for chemical cure composites, and (4) Group 4 -Displacement group for chemical cure composites. In the control groups, the brackets were bonded with no precure bracket displacement. In the displacement groups, the brackets were bonded with 2 mm precure linear displacement. Photoactivation was carried out for light-cure composites. Shear bond strength tests were carried out using the universal testing machine. Statistical analysis used: Data were analyzed using the one-way analysis of variance test. RESULTS: The mean shear bond strength of Groups 1, 2, 3, and 4 were observed to be 14.49 ± 0.75, 13.40 ± 0.61, 12.34 ± 0.53, and 11.55 ± 2.43MPa, respectively, with the displacement groups showing lower shear bond strength when compared to the control groups. Whether displaced or not, chemically cured composites showed lower bond strength when compared to light-cured composites. CONCLUSIONS: Displacement of brackets during bracket placement seemed to reduce the enamel bond strength after the final positioning of the bracket.

A Retrospective Evaluation of Conventional Rapid Maxillary Expansion versus Alternate Rapid Maxillary Expansion and Constriction Protocol Combined with Protraction Headgear in the Management of Developing Skeletal Class III Malocclusion.

AIMS AND OBJECTIVES: The reverse pull headgear has been widely used to intercept a developing skeletal Class III malocclusion with maxillary deficiency. Rapid maxillary expansion (RME) is recommended along with the reverse pull headgear because there is disruption of the circummaxillary and intermaxillary sutures. This, in turn, expedites the orthopedic effect of the reverse pull headgear. However, studies have shown that the circummaxillary sutures may not be fully disrupted by the use of RME alone. The protocol of alternate RME and constriction (Alt-RAMEC) has been found to produce much more beneficial effects. Hence, this retrospective study was conducted to compare and assess the results obtained in the two methods. MATERIALS AND METHODS: This study comprised pre- and post-treatment lateral cephalograms of two groups of nine patients each (total 18 patients - 10 females and 8 males) having skeletal Class III malocclusion (ANB<0°) due to a retrognathic maxilla with or without associated mandibular prognathism treated at the Department of Orthodontics of a teaching institute in Kerala. The patients were treated with either Alt-RAMEC/protraction or RME/protraction. The statistical analysis of the data was done using statistical package SPSS Version 16 software (SPSS Inc., Chicago, IL, USA). RESULTS: Skeletal, dental, and soft-tissue parameters in Group 2 (Alt-RAMEC group) showed very significant changes with the maxilla moving forward, mandible rotating backward and downward, and proclination of the maxillary incisors when compared to Group 1. CONCLUSIONS: It may be concluded from the results of our study that the Alt-RAMEC protocol and reverse pull headgear might be more effective than conventional RME and the reverse pull headgear to correct a retruded maxilla in a developing skeletal Class III patient.

Evaluation of Biomechanical Properties of Four Loops at Different Activation: A Finite Element Method Study.

AIM: The aim of the study was to evaluate the force, moment, and moment/force ratio (M/F) generated by activating T loop, Kalra Simultaneous Intrusion and Retraction (KSIR) loop, Omega loop, and Teardrop loop made of titanium molybdenum alloy (TMA) wire with different preactivation bends at 1, 2, and 4 mm activation. MATERIALS AND METHODS: Finite element method (FEM) models of the four loops were created and different preactivation bends were placed. The loops were then activated and analyzed for force, moment, and M/F ratio using ANSYS software. RESULTS: In loops without preactivation bends, highest force values were generated by Omega loop, whereas T loop had the least force value. The mean value for the M/F in the alpha segment was almost similar. In loops with preactivation bend, the force was highest in Teardrop loop, whereas T loop had the least force value. The mean value for the M/F in the alpha segment was almost similar in all the loops. CONCLUSION: T loop with preactivation bend shows the most favorable properties. CLINICAL SIGNIFICANCE: T loop is comparatively reliable for the frictionless mechanics for the space closure than the other loops evaluated in clinical use.

Platelets and Their Pathways in Dentistry: Systematic Review.

Advancing research in medicine and technology has benefitted the mankind immensely with its contribution toward an improved life quality and increased life expectancy. The inability of a human body to autoregenerate has resulted in an increased demand for newer and healthier tissues and organs. Therefore, the restoration of naturally replicated tissue components has become a subject of interest for the scientific community lately. There was felt an intense quest for promoting strategies that could restore tissue regeneration and fuel the field of regenerative medicine. It was then the role of platelets was accounted for its wound healing and regenerative effects. Consequently, the use of platelet concentrates to improve wound healing, and bone formation was explored, which was considered to be possible because platelets contain high quantities of growth factors which would be able to stimulate cell proliferation, matrix remodeling, and angiogenesis, thereby establishing a new era of research with the successful application of innovative medical therapies focused on healing damaged tissues or regenerate the affected organs.

Cytomorphometric Analysis on the Effects of Components of Orthodontic Appliances on the Epithelial Cells of the Buccal Mucosa.

AIM: The aim of the present study was to evaluate the effect of fixed orthodontic appliances on the epithelial cells of buccal mucosa in patients undergoing orthodontic treatment. MATERIALS AND METHODS: The study group included 30 healthy patients who were advised orthodontic treatment. Applying sterile cement spatula, scrapping of exfoliated buccal epithelial cells was performed from the middle part of the inner cheeks before starting the orthodontic treatment and at 1st week, 2nd week, 1 month, and 45 days after the treatment, followed by smearing and staining with Papanicolaou stain. Light microscope was used to score micronuclei, and independent two-tailed t-test was used for statistical analysis. RESULTS: Micronuclei were assessed during the various stages of treatment and were recorded accordingly. At 1 week, there was increase in micronuclei number compared to before starting the treatment (day 0) and at 15th day; 30th day showed decrease in number compared to 1 week but increase compared to day 0. The results of day 45 were almost equal to day 0 with a significant P value (P < 0.001). CONCLUSION: Fixed orthodontic appliances induce increased micronuclei frequency, especially in the first weeks of treatment, however, these genotoxic effects tend to approach baseline levels in later period.