Biomechanical characteristics of microimplant for anchorage in orthodontics: a 3D finite element model study.

In orthodontic treatment, anchorage control is essential for success. A recent development, stationary anchorage (micro- implants) eliminates one of the uncertainties of orthodontic tooth movement by offering absolute control over potentially undesirable counter movements. The objective of this study was to establish a 3D finite element model for microimplant and to analyze the influence of different angulations to the long axis of the teeth (30-90°) on the biomechanical characteristics of orthodontic anchorage implant-bone interface. Results of this study showed that largest stress and deformation was seen in the cortical bone and upper region of trabecular bone. Stress and deformation increased as the angulations of the implant to the long axis of the tooth increased. As the angulation of the implant to the long axis of maxillary 1st molar increased, stress and deformation also decreased. Maximum stress and displacement were recorded when implant was placed perpendicular to the long axis of maxillary 1st molar.

Therapeutic extraction of lower incisor for orthodontic treatment.

UNLABELLED: Lower incisor extraction in orthodontic treatment was very rare modality of orthodontic treatment because there are few patients who meet the standards for such treatment. Proper diagnosis and treatment planning should be done to achieve good occlusion and facial esthetics. Criteria for lower incisor extraction included degree of crowding, tooth size discrepancy, pathologic condition, vertical overbite, sagittal incisal relationship, skeletal growth pattern and age of the patient. This article comprises of a case of class I malocclusion treated with lower incisor extraction, with comprehensive analysis, diagnosis and treatment planning, treatment results were satisfactory. CLINICAL SIGNIFICANCE: Mandibular incisor extraction can be an effective treatment option in borderline cases with mild crowding in lower arch. Minimal alteration of mandibular arch form is key factor for success and stable results.

Effect of trichloromethane on the bond strengths between acrylic teeth and different heat-cured denture bases: a comparative study.

AIM: This study is to evaluate the role of 1:1 v/v 30% trichloromethane and monomer solvent in enhancing the durability of bonding between cross-linked acrylic teeth and different heatcured denture bases with or without mechanical preparations made on ridge lap portion of the artificial teeth. MATERIALS AND METHODS: Two high impact denture base resin materials (Trevalon HI, DeTrey, UK, and DPI Tuff, Mumbai) and one nonhigh impact denture base resin material (DPI Quick Set, Mumbai) were selected to form three groups. Each group contains 30 specimens prepared by five different methods. A mixture of 30% trichloromethane and monomer, mixed in the ratio of 1:1 and applied for 1 minute on the ridge lap area of experimental specimens of methods--B, C, D and E (Specimens of method--A being control group, where no alterations were made at the ridge lap portion of acrylic teeth) before curing. Hounsfield universal testing machine is employed to evaluate the comparative bond strengths. RESULTS: No significant difference was seen in bond strengths between specimens of experimental methods in all groups. When each group was assessed separately method B specimens in group 1 (739.2 N), group 2 (758 N) and method D specimens in group 3 (729 N) showed highest mean bond strengths. Control group specimens showed the least bond strength (400-460 N) in all groups with more adhesive failures. CONCLUSION: Ridge lap portion of the specimens treated with chemical solvent as in method B showed increased bond strength in groups 1 and 2. Hence, this is a preferred method. CLINICAL SIGNIFICANCE: Evaluation of effect of different chemical and mechanical preparations at the ridge lap areas of acrylic teeth before acrylization helps the clinician and technician to overcome the problem of debonding of teeth from denture bases and in turn provides better quality prosthesis to the patient.