Comparison of dimensional changes and water absorption of temporary crown resin in conventional and 3D printing methods

Abstract

Background and goal: Using temporary restorations is one of the important steps in a lot of prosthetic treatments. Dimensional changes due to polymerization and water absorption is one of the inherent characteristics of acrylic resins. They can cause damage to remaining tooth structure and surrounding tissues. 3-D print has a very high potential in the field of dentistry and its usage is increasing every day. So, the aim of this study is the comparison of dimensional changes and water absorption of temporary crown resin in conventional and 3D printing methods Materials and Methods: In this in-vitro, experimental study, 30 specimens of ALIKETM (GC America) conventional acrylic resin with the dimensions of 10×5×2 mm were made using a metal mold. The same number of specimens with the same dimensions were made using FREEPRINT® temp (Detax) resin with 3-D print method (total n=60). All specimens were incubated in 37±1ºC water for 7 days. Dimensions and weight of each specimen were measured after the end of polymerization and after incubation. Dimensional changes and water absorption were calculated and the results were reported in indicators of descriptive statistics using mean ± standard deviation. Data normality was evaluated by Kolmogorov-Smirnov test. In order to compare dimensional changes and water absorption between two groups, if data was normal, independent t-test was used and otherwise Mann–Whitney test was used. Findings: Mean dimensional change was 1.58±0.59% in conventional group and 1.61±0.55% in 3-D print group. Because of the normality of the data in this variant, the two groups were compared by independent t-test and the P-value was 0.82. As a result, there was no significant difference between two groups. Median (first quarter-third quarter) of water absorption rate in conventional resin group was (0.06-0.13) 0.067 g/cm3 and in 3D printing group was (0.07-0.10) 0.077 g/cm3. Due to abnormal distribution of data, Mann-Whitney test was used to compare the two groups. According to the results of Mann-Whitney test, there was a statistically significant relationship between the median of water absorption in the two groups (P-value = 0.011). Conclusion: In this study no significant difference were seen between conventional ALIKE resin and 3-D printable FRAAPRINT resins in terms of dimensional changes But water absorption was significantly higher in FREEPRINT resin. Dentists can choose either of these two materials according to all factors affecting the treatment, such as availability, construction time, ease of work for the dentist and the patient, and treatment costs.