Comparison of Shear Bond Strengths of Ceramic Brackets Using Either Self-etching Primer or Conventional Method After Intracoronal Bleaching

Objective:To evaluate initial shear bond strengths (SBSs) of ceramic brackets using either a self-etching primer (SEP) or the conventional method (CM) after intracoronal bleaching with sodium perborate and distilled water.Materials and Method:Eighty human incisors were divided into 4 groups according to bleaching and bonding procedures: group 1, bleaching was not applied and brackets were bonded with SEP; group 2, bleaching was not applied and brackets were bonded with the CM; group 3, intracoronal bleaching with sodium perborate was applied for 3 weeks and brackets were bonded with SEP; group 4, intracoronal bleaching with sodium perborate was applied for 3 weeks and brackets were bonded with the CM. The SEP (Transbond Plus) was applied as recommended by the manufacturer. After SEP application, ceramic brackets were bonded with light cure adhesive (Transbond XT). For the CM, the teeth were etched with 37% phosphoric acid. After etching, a thin uniform coat of primer (Transbond XT Primer) was applied and ceramic brackets were bonded with light cure adhesive (Transbond XT). The SBSs were measured after water storage for 30 days, after 1000 cycles of thermocycling between 58C and 558C. Bond failure location was determined with the adhesive remnant index (ARI).Results:For the SEP method, there was no significant difference between the SBS values of the bleaching and nonbleaching groups. Furthermore, for the CM, the SBS value of the nonbleaching group was not significantly different from that of the bleaching group. The SBS values of the SEP method presented significant differences from the SBS values of the CM (p , 0.001). The SBS values of the SEP application decreased with and without bleaching. ARI scores did not show any significant difference between the groups (p = 0.174).Conclusion:Intracoronal bleaching with sodium perborate and distilled water did not affect the SBS values of ceramic brackets

Shear bond strength of a self-etching primer after 10,000 and 20,000 thermal cycles

Purpose: To determine the effects of thermocycling on shear bond strengths (SBSs) of a self-etching primer (SEP) after 10,000 and 20,000 thermal cycles. The tested hypothesis was that 10,000 and 20,000 thermal cycles would affect the bond strength of metal brackets bonded to enamel with the self-etching primer. Materials and Methods: Brackets were bonded to bovine incisors with two etching protocols. In group CM (conventional method), teeth were etched with 37% phosphoric acid for 30 s. In group SEP, a self-etching primer (Transbond Plus, 3M Unitek) was applied. Brackets were bonded with light-curing adhesive (Transbond XT, 3M Unitek). The SBSs were determined after water storage at 37°C for 24 h, after 10,000 and 20,000 cycles of thermocycling. Results: For both groups (CM and SEP), SBSs decreased with 10,000 and 20,000 thermal cycles. These decreased SBSs were significantly different from the values obtained with no thermocycling. Highest SBSs were observed with no thermocycling for groups CM and SEP (18.6 and 18.0 MPa, respectively). These values were not statistically different from each other. Lowest SBSs were obtained with 10,000 and 20,000 thermal cycles for group SEP (14.2 and 14.7 MPa, respectively). These values were significantly different from all other SBSs. Conclusion: This study indicates that the SEP (Transbond Plus) provides clinically acceptable bond strength values compared with the conventional method after 10,000 and 20,000 thermal cycles. © 2010 by Quintessence Publishing Co Inc

Physical properties of root cementum: Part 24. Root resorption of the first premolars after 4 weeks of occlusal trauma

Introduction In orthodontics, adding restorative materials on occlusal or lingual surfaces is a common method to create a mini-biteplane to increase patients' vertical dimension temporarily to facilitate several treatment procedures. However, this method transmits excessive occlusal forces through the periodontal ligament and causes trauma. In this prospective randomized clinical trial, we measured and compared quantitatively the volumes of root resorption after 4 weeks of occlusal trauma. Methods Forty-eight maxillary and mandibular first premolars of 12 patients (6 girls, 6 boys) comprised the sample for this study. One side of each patient was randomly selected as the control. On the contralateral side, a light-cured glass ionomer cement (Transbond Plus Light Cure Band Adhesive; 3M Unitek, Monrovia, Calif) was bonded onto the occlusal surface of the mandibular first premolar so that the cement was in contact with the maxillary first premolar. After 4 weeks, both first premolars were extracted. Each sample was imaged using a microcomputed tomography system (1172; SkyScan, Aartselaar, Belgium) and analyzed with specially designed software for volumetric measurements of resorption craters. Furthermore, pain was evaluated with a visual analog scale for 7 days. Results There were significant differences in the amounts of root resorption between the control and the experimentally traumatized teeth. No significant difference among the buccal, lingual, mesial, and distal surfaces was found in either jaw. Furthermore, no significant difference existed in the amount of root resorption among the cervical, middle, and apical thirds of both jaws. There was no correlation between age, sex, volume of the root resorption craters, and pain. Conclusions Restorative buildups, used to increase the vertical dimension by 2 mm for 4 weeks, caused root resorption along the sides of the teeth during the active bite-increase period. Copyright © 2014 by the American Association of Orthodontists

Physical properties of root cementum: part 24. Root resorption of the first premolars after 4 weeks of occlusal trauma

Introduction: In orthodontics, adding restorative materials on occlusal or lingual surfaces is a common method to create a mini-biteplane to increase patients' vertical dimension temporarily to facilitate several treatment procedures. However, this method transmits excessive occlusal forces through the periodontal ligament and causes trauma. In this prospective randomized clinical trial, we measured and compared quantitatively the volumes of root resorption after 4 weeks of occlusal trauma. Methods: Forty-eight maxillary and mandibular first premolars of 12 patients (6 girls, 6 boys) comprised the sample for this study. One side of each patient was randomly selected as the control. On the contralateral side, a light-cured glass ionomer cement (Transbond Plus Light Cure Band Adhesive; 3M Unitek, Monrovia, Calif) was bonded onto the occlusal surface of the mandibular first premolar so that the cement was in contact with the maxillary first premolar. After 4 weeks, both first premolars were extracted. Each sample was imaged using a microcomputed tomography system (1172; SkyScan, Aartselaar, Belgium) and analyzed with specially designed software for volumetric measurements of resorption craters. Furthermore, pain was evaluated with a visual analog scale for 7 days. Results: There were significant differences in the amounts of root resorption between the control and the experimentally traumatized teeth. No significant difference among the buccal, lingual, mesial, and distal surfaces was found in either jaw. Furthermore, no significant difference existed in the amount of root resorption among the cervical, middle, and apical thirds of both jaws. There was no correlation between age, sex, volume of the root resorption craters, and pain. Conclusions: Restorative buildups, used to increase the vertical dimension by 2 mm for 4 weeks, caused root resorption along the sides of the teeth during the active bite-increase period

Effect of continuous versus intermittent orthodontic forces on root resorption: A microcomputed tomography study

Objectives: To compare the extent of root resorption and the amount of tooth movement between continuous orthodontic force and intermittent orthodontic force that was activated in a similar way to a 4-week orthodontic adjustment period. Materials and Methods: Twenty-five patients who required the extraction of upper first premolars were recruited in this study. A buccally directed continuous force of 150 g was applied to the upper first premolar on one side for 15 weeks. A buccally directed intermittent force (28 days on, 7 days off) of the same magnitude was applied to the contralateral first premolar. The teeth were extracted at the end of the experimental period and processed for volumetric evaluations of resorption craters. The degree of tooth movement and rotation were measured on the study models. Results: Continuous force application displayed significantly higher root resorption volume than the intermittent force application (P, .05), particularly on the buccal and lingual surfaces (P, .05) and the middle third of the root (P, .01). There was more tipping and rotational movement in the continuous force group. Conclusions: In a 4-week orthodontic adjustment period, intermittent force significantly reduced the amount of root resorption compared with continuous force. Although there was less degree of tooth movement with intermittent force, unwanted rotational movement was avoided. This is crucial in patients who are predisposed to orthodontically induced inflammatory root resorption, and the use of this intermittent regimen should be considered. © 2018 by The EH Angle Education and Research Foundation, Inc.Corresponding author: Dr M. Ali Darendeliler, Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Level 2, 2 Chalmers Street, Surry Hills NSW 2010 Australia (e-mail: [email protected]) Accepted: May 2018. Submitted: January 2018. Published Online: August 20, 2018 © 2018 by The EH Angle Education and Research Foundation, Inc