RESUMEN
Aim: This study was performed to compare the effect of applying Pro Seal cure varnish to the enamel surface when placed before or after application on the shear bond strengths of orthodontic brackets
Methods: Sixty non carious premolars were randomly divided into three equal groups. In the first and second groups, Pro Seal, a fluoride releasing light cure varnish was applied to the enamel surface before and after the sealant provided with adhesive was placed respectively while, the third group [Control] was bonded regularly using only the sealant supplied with the adhesive. Monolok[2] no-mix bonding system was used to bond stainless steel brackets to each tooth. All teeth were embedded in self-cure acrylic and placed in steel rings and were secured in a jig attached to the base plate of a universal testing machine. A perpendicular force was applied to the bracket at a crosshead speed of 0.5mm/min. The residual adhesive on the enamel surface was evaluated after debonding with the Adhesive Remnant Index [ARI]
Results: The mean shear bond strength for Group I treated with the Pro Seal varnish before the sealant was 10.06+/- 3.11 MPa. However, for Group II, where varnish was applied after the sealant, the mean shear bond strength was 12.78 +/- 3.7 MPa, while it was 12.81 +/- 2.6 MPa for the control group. Analysis of variance test showed that the mean shear bond strengths of the three groups were not significantly different from each other. The Chi-Square test evaluating the residual adhesive on enamel surfaces showed no significant differences between all groups
Conclusions: It was thus concluded that the application of Pro Seal before or after the sealant did not reduce the mean shear bond strength of orthodontic brackets. However, further studies are recommended to compare the amount of enamel protection offered in either situation
RESUMEN
One of the concerns of orthodontic patients nowadays is whether premolar extraction will prevent third molar impaction and obviate the need for their surgical removal. The aim of this study was to investigate changes in third molar position as a result of first premolar extractions and or-thodontic therapy in Egyptian adolescents. Pre and post treatment panoramic and lateral ce-phalometric radiographs of 38 orthodontically treated patients were used in this study. All patients had Angle Class I malocclusion with moderate crowding. According to the treatment modality, the patients were divided into 2 groups. Group I comprised the radiographs of 20 patients who were treated by premolar extraction, while Group II comprised the radiographs of 18 patients who were "treated non-extraction. Relevant anatomjcal landmarks were traced on both the pre and post treatment panoramic radiographs. Angular and linear position of upper and lower 3rd molars were measured. Then, the amount of movement of upper and lower third molars were computed. Statistical analysis was used to compare between the 2 groups. The results of the study revealed that premolar extractions led to a statistically significantly greater increase in the space available for upper and lower third molars, as well as a statistically significantly greater improvement in the inclination and vertical position of upper third molars. These effects might contribute to the eruption process of upper and lower 3rd molars and prevent their impaction
RESUMEN
The purpose of this study was to compare in-vitro the shear bond strength of stainless steel brackets bonded by phosphoric acid etching versus Reliance First Step self-etching primer. Forty human upper first bicuspids were used in this study. In Group I [control group], bicuspids were first etched with 37% phosphoric acid, rinsed with water and dried. The sealant was applied and Light- cure composite [Transbond XT] was used to bond the brackets. In Group II, a self-etching primer [First Step. Reliance Orthodontic Products, Inc.] was applied to the teeth according to manufacturer's instructions. Then, the brackets were bonded as in Group I. Each group was stored in water at 37°C for 1 week. Brackets were then subjected to a shear bond strength test using a computerized testing Lloyds machine. Descriptive statistics were calculated for each group and the Student t test was used to compare between the two groups. The results of this study revealed that the mean bond strength of self-etching primer group was significantly higher than PO4 acid etching group [26.0 N/mm[2] +/- 18.8 and 15.7 N/mm[2] +/- 5.6 respectively. p = 0.024481]
RESUMEN
The purpose of this study was to compare in-vitro the shear bond strength of stainless steel brackets bonded to previously bonded teeth via 4 different procedures. Eighty-four human upper first bicuspids were used in this study. They were all etched and bonded using Po4 acid and Transbond Light Cure composite. The brackets were debonded one week later with debonding pliers and the buccal surfaces cleaned with a finishing bur. Then, they were divided into four equal groups, 21 bicuspids each. They were rebonded with new brackets using 4 different protocols. In Group I, the teeth were re-etched with phosphoric acid and rebonded with Reliance Two-paste system. In Group II the teeth were also re-etched with Po4 acid and rebonded with Transbond Light Cure composite. In Group III. First-step etching primer was applied and Reliance phase II two-paste system was used to rebond the teeth, In Group IV. First-step etching primer was applied and Transbond Light Cure composite was used to rebond the teeth. The 4 groups were stored individually in water at 37°C for 1 week. Brackets were then subjected to a shear bond strength test using a computerized testing Lloyds machine. Descriptive statistics were calculated for each group and One-Way ANOVA was used to compare between the two groups, followed by multiple comparison of group means [LSD]. It was found that rebonding teeth by re-etching with phosphoric acid yielded higher bond strength than when using etching primer. Also, it was bound that rebonding using two-paste composite yielded higher bond strength than when using light-cure composite