Labial and Palatal Pressure Changes in Extraction Cases Before and After Maxillary Incisor Retraction: A Quasi-Experimental Study.

OBJECTIVE: To evaluate the changes in lip and tongue pressure before and after incisor retraction in patients undergoing orthodontic treatment with premolar extraction and incisor retraction. STUDY DESIGN: A Quasi-experimental study Place and Duration of the Study: Orthodontic Department at Dow University of Health Sciences, Pakistan, from January 2018 to November 2019. METHODOLOGY: The study included 64 patients who were divided into two groups, (32 patients of class I and 32 patients of class II malocclusion). The lip and tongue pressures were recorded before and after incisor retraction with the help of Flexiforce sensor. The collected data were statistically analysed using the SPSS V-24 software. Shapiro-Wilk test was used to test the normality of data. The mean difference between lip and tongue pressure before and after incisor retraction was analyzed by Wilcoxon Signed Ranks Test. The difference in soft tissue pressures between class I and class II treatment groups was carried out using the Mann Whitney test. RESULTS: The mean pressure on the labial surface of incisors was significantly reduced after premolar extraction and incisor retraction (p </=0.001). On the other hand tongue pressure on the palatal side of incisors was enhanced after incisor retraction (p=0.008) Comparing the differences between Angle's class I and class II malocclusion in mean pressure changes before and after incisor retraction revealed that the difference was not statistically significant on labial (p=0.58) or palatal side (p=0.28) of maxillary incisors. CONCLUSION: Reduced lip pressure and increased tongue pressure were observed after incisor retraction, whereas no significant change was seen in between the class I and class II cases. This signifies that orthodontic extraction affects the pressure changes on incisors and teeth do not remain in balance equilibrium at rest. KEY WORDS: Lip pressure, Tongue pressure, Orthodontic treatment, Flexiforce resistive sensor, Extraction, neutral zone.