Comparison of Dimensional Accuracy of PMMA Resin by Convectional and Injection Molding Technique Gupta et al. THIEME 36 An In vitro Study to Evaluate and Compare the Dimensional Accuracy of Poly (Methyl Methacrylate) by Injection Molding and Conventional Molding Technique Ambika Shrivastava Gupta 1, Vaibhav Awinashe 2 Umesh Palekar 3 Siddharth Gupta 1 Shilpa Jain 1 Arpit Jain 4 1 Department of Prosthodontics, Crown and Bridge and Implantology, Rishiraj College of Dental Sciences and Research Centre, Bhopal, Madhya Pradesh, India 2 Dental Faculty, Department of Dentistry in Al-Russ, Qassim University, Buraydah, Saudi Arabia 3 Department of Prosthodontics, Rural Dental College and Hospital, Loni, Maharashtra, India 4 Department of Oral Medicine and Radiology, College of Dental Sciences and Hospital, Indore, Madhya Pradesh, India published online December 12, 2020 Address for correspondence Ambika Shrivastava Gupta, MDS, Department of Prosthodontics, Crown and Bridge and Implantology, Rishiraj College of Dental Sciences and Research Centre, Bhopal 462016, Madhya Pradesh, India (e-mail: ambikashrivastava@gmail.com). Introduction Poly(methyl methacrylate) is widely used as denture base material due its better physical properties, ease to fabricate, and repair. Despite being the material of choice for the denture fabrication, dentures made from poly(methyl methacrylate) may exhibit dimensional changes due to volumetric shrinkage. This further affects the retention of the denture. Various methods have been used to overcome this problem. One such method is the use of injection molding technique. So, a study was planned to evaluate the efficacy of dentures processed by injection molding technique in reduc- ing the volumetric shrinkage. Objective To evaluate and compare the dimensional accuracy of poly(methyl methacrylate) resin processed by conventional and injection molding technique. Materials and Methods A total of 90 samples were made. Half of the samples (45) were fabricated by compression molding and half (45) by injection molding technique. Dimensional change was studied at three equidistant points in posterior region with the help of digitized travelling microscope. Statistical analysis was done using stu- dent’s t-test. Result Dimensional accuracy of injection molded poly(methyl methacrylate) resin was greater than that of compression molded poly(methyl methacrylate). Abstract Keywords ► compression molding ► injection molding technique ► poly (methyl methacrylate) ► retention DOI https://doi.org/ 10.1055/s-0040-1721551 ISSN 2321-1482. ©2020. Bhojia Dental College and Hospital affiliated to Himachal Pradesh University. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/). Thieme Medical and Scientific Publishers Pvt. Ltd. A-12, 2nd Floor, Sector 2, Noida-201301 UP, India Dent J Adv Stud:2021;9:36–42 Original Article Published online: 2020-12-12