ABSTRACT
INTRODUCTION: The pre-adjusted brackets are available in various prescriptions and sizes; nevertheless there are still many controversies as to which pre-adjusted edgewise bracket offers the maximum clinical efficiency. AIM: This study was conducted to determine and compare the amount of lower incisor proclination during de-crowding if any of the Mini-Uni Twin Brackets with that of the standard double width brackets. MATERIALS AND METHODS: A total of 20 patients i.e., 10 patients in each group both males and females were randomly selected for the study from subjects seeking treatment, the selected samples were grouped as follows. Group I - Double Width Brackets (3M Unitek Gemini Series) 0.018" slot with Roth prescription. Group II - Mini Uni-Twin Bracket (3M Unitek) 0.018" slot with Roth prescription. RESULTS: The Mini-Uni Twin Brackets had statistically significant (p = 0.01) amount of proclination of the lower anteriors (0.8(o)± 0.3(o)) after de-crowding as compared to the standard Double Width Brackets and since the mean change in the Incisor Mandibular Plane Angle (IMPA) was lesser than 1(o), its clinical significance could be questionable. CONCLUSION: The Mini Uni Twin brackets are comparatively efficient in the lower anterior decrowding but further comparative clinical studies need to be performed on these Mini Uni Twin brackets, with an increase in the sample size and also the number of parameters to prove its total clinical efficiency.
ABSTRACT
INTRODUCTION: Etching of enamel and dentin surfaces increases the surface area of the substrate for better bonding of the tooth colored restorative materials. Acid etching is the most commonly used method. Recently, hard tissue lasers have been used for this purpose. AIM: The aim of the present study was to evaluate and compare the etching pattern of Er,Cr:YSGG and conventional etching on extracted human enamel and dentin specimens. MATERIALS AND METHODS: Total 40 extracted non-diseased teeth were selected, 20 anterior and 20 posterior teeth each for enamel and dentin specimens respectively. The sectioned samples were polished by 400 grit Silicon Carbide (SiC) paper to a thickness of 1.0 ± 0.5 mm. The enamel and dentin specimens were grouped as: GrE1 & GrD1 as control specimens, GrE2 & GrD2 were acid etched and GrE3 & GrD3 were lased. Acid etching was done using Conditioner 36 (37 % phosphoric acid) according to manufacturer instructions. Laser etching was done using Er,Cr:YSGG (Erbium, Chromium : Ytrium Scandium Gallium Garnet) at power settings of 3W, air 70% and water 20%. After surface treatment with assigned agents the specimens were analyzed under ESEM (Environmental Scanning Electron Microscope) at X1000 and X5000 magnification. RESULTS: Chi Square and Student "t" statistical analysis was used to compare smear layer removal and etching patterns between GrE2-GrE3. GrD2 and GrD3 were compared for smear layer removal and diameter of dentinal tubule opening using the same statistical analysis. Chi-square test for removal of smear layer in any of the treated surfaces i.e., GrE2-E3 and GrD2-D3 did not differ significantly (p>0.05). While GrE2 showed predominantly type I etching pattern (Chi-square=2.78, 0.05
0.10) and GrE3 showed type III etching (Chi-square=4.50, p<0.05). The tubule diameters were measured using GSA (Gesellschaft fur Softwareentwicklung und Analytik, Germany) image analyzer and the 't' value of student 't' test was 18.10 which was a highly significant result (p<.001). GrD2 had a mean dentinal tubule diameter of 2.78µm and GrD3 of 1.09µm. CONCLUSION: The present study revealed type I etching pattern after acid etching, while type III etching pattern in enamel after laser etching. The lased dentin showed preferential removal of intertubular dentin while acid etching had more effect on the peritubular dentin. No significant differences was observed in removal of smear layer between the acid etched and lased groups. Although diameter of the exposed dentinal tubules was lesser after lased treatment in comparison to acid etching, further long term in vivo studies are needed with different parameters to establish the usage of Er,Cr:YSGG as a sole etching agent.
