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AIM The purpose of this study was to evaluate force systems to bring about the en masse retraction of maxillary anterior teeth having reduced bone levels using finite element analysis. MATERIALS AND METHODS This is a prospective study. Three-dimensional finite element models of maxillary dentition having normal alveolar bone level and 2, 4, and 6 mm bone loss with first premolar extraction were constructed from a spiral CT scan of a skull. Archwire and brackets were modeled on the facial surfaces of teeth. Retraction force of 175 gm was applied from an orthodontic mini-implant placed bilaterally between the second premolar and first molar and 12 mm above plane of the archwire to anterior retraction hook (ARH) fixed at two heights of 6 and 10 mm above the archwire. RESULTS Maximum displacement and periodontal ligament (PDL) stress were calculated for different combinations of bone levels and ARH. As the bone loss increased, the tipping tendency, amount of intrusion, and maximum von Mises stress in PDL also increased, showing a direct correlation. CONCLUSION To minimize tipping and PDL stress, the height of ARH should be increased in alveolar bone loss conditions to allow retraction force to pass through or even above the center of resistance of anterior teeth. Even then, pure bodily retraction may not be achieved, but tipping tendency can be reduced. Nevertheless, it may not be suitable to increase ARH beyond a limit owing to chances of irritation to the vestibular mucosa. Alternative methods should be contemplated to reduce the tipping behavior. CLINICAL SIGNIFICANCE The alternative is to apply a lighter retraction force to reduce lingual tipping. A higher counter-moment in the archwire or bracket can also be incorporated.

Objective: To evaluate the shear bond strength of the brackets bonded with adhesive and flowable composites under contamination by human blood and human saliva& to evaluate enamel damage post debonding using ARI index. Material and Methods: 100 human premolars extracted for orthodontic reasons were used & shear bond strengths of 4 flowable composites and one conventional composite were evaluated under 2 bonding conditions: (1) contamination with saliva (2) contamination with blood. Contamination was done after the application of primer in all the groups and before bonding the brackets, decontamination was done by using the air water spray for 5 seconds and air drying the surface. Shear bond strengths were measured with universal testing machine after placing the bonded specimen in deionized water and incubator at 37˚C for 72 hours to permit adequate water absorption and equilibration. After debonding, each specimen was examined under a stereoscopic zoom microscope (10X) to identify the location of the bond failure. The residual composite remaining on the premolar was assessed by using the remnant index (ARI), where each specimen was scored according to the amount of material remaining on the enamel surface. Results: conventional composite showed the highest bond strength in both blood and salivary contaminations. Among the flowable composites, each behaved differently. Blood contamination showed reduced bond strengths in all the groups. Decontamination with air water spray and air drying the surface before bonding the brackets seems to be satisfactory. Conclusion: with use of a primer, flowable composites can be used to bond the orthodontic brackets under contamination and decontamination with air water spray for 5 seconds and air drying the surface before bonding seems to be satisfactory if contamination occurs after the application of the primer.