ObjectiveTo evaluate the rate of canine retraction, mesial movement of molar and pain perception in maxillary first premolar extraction patients with or without flapless cortical perforations (FCPs).MethodsThirty adult patients with class II div I malocclusion were randomly allocated with the help of SPSS software to either perforation or conventional group for carrying out this randomized parallel group-controlled trial in 1:1 ratio. Maxillary first premolars were extracted and after canine retraction, distance between the tip of the canine and midpoint of incisal edge and the distance between the cervical midpoints on the height of contour of respective cinguli was measured. Also, mesial movement of molar and pain perception were assessed in both groups. Three bilateral cortical FCP of 1.5 mm diameter were made in the perforation group. Data were analyzed with the help of SPSS software with an intention-to-treat the FCP approach.ResultsSignificant canine retraction in patients with FCP (mean retraction of 6.68 ± 0.60 [measured at crown tip level] and 5.97 ± 0.71 mm [measured at mid cervical level]) was revealed, while patients with conventional mechanics had mean retraction of 2.54 ± 0.49 and 2.33 ± 0.46 mm. Mesial movement of molar also showed significant difference (FCP = 0.48 ± 0.11 mm and Conventional = 0.65 ± 0.19 mm). Pain perception in control group was significantly lower in day 1 and 2.ConclusionFCPs are an effective method of accelerating the rate of canine retractions by 2–3 fold of tooth movement, however, pain perception was high in day 1 and 2.

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OBJECTIVE: The aim of this experimental study is to compare the dimensional accuracy of gypsum casts after repeated disinfection in microwave at 900 Watts, 2450 MHz (5 minutes) and immersion in 0.5% Sodium hypochlorite (10 minutes). Disinfecting casts is recommended to prevent cross infection but may cause dimensional changes. During fabrication of prosthesis, a cast may get contaminated several times so there is a need of repeated disinfection. METHODOLOGY: Sample size was 33 (11 in each group), calculated through WHO software for sample size determination by using standard deviation of 0.16 at 95% confidence interval and 80% power of study. Impressions in irreversible hydrocolloid were recorded of an acrylic cast fabricated for this study. The impressions were poured with die stone and were randomly divided into 3 groups; Group I: Microwave disinfection, Group II: Immersion disinfection in 0.5% Sodium hypochlorite, Group III: Control group. For Groups I and II, each cast was disinfected 7 times with 5 minutes interval between two disinfection cycles, after every cycle anteroposterior and mediolateral measurements were recorded using digital Vernier caliper (accuracy upto 0.01 mm). For group III, casts were rinsed with distilled water, dried in open air within temperature range of 28+/-2OC for 10 mins followed by anteroposterior and mediolateral measurements. This procedure was repeated seven times for each cast. RESULTS: Anteroposterior and Mediolateral differences of dimensional change between and within the Group A, B and C was calculated by One Way ANOVA. Inter/intra examiner reliability was taken into consideration at the time of study. Mean dimensional change in the casts were insignificant through six disinfecting cycles. However, in the seventh cycle, a significant difference (p=0.003) was observed in the anteroposterior dimension (0.03% dimensional change for Group A and 1.26 % for Group B whereas, in mediolateral dimension, dimensional change was 0.35% for Group A and 0.59% for Group B (p=0.004). Dimensional change of >0.5% was considered as the cutoff value for casts to be considered as dimensionally accurate. Casts disinfected through immersion disinfection did not produce dimensionally inaccurate casts in anteroposterior dimension after third cycle and in seventh cycle in mediolateral dimension. However, result is significant only in seventh cycle. Microwave disinfection produced dimensionally accurate casts throughout all cycles. CONCLUSION: Microwave disinfected casts remained dimensionally stable compared to immersion disinfection. KEYWORDS: Disinfection, microwave, immersion, dimensional stability, gypsum casts