완전 무치악에서 임플란트 디지털 인상의 정확성

Abstract

Purpose : The purpose of this study is to compare the accuracy of digital and conventional impression techniques using an intraoral scanner in producing implant fixed superstructure in fully edentulous patients, in addition, to evaluate the clinical applicability of intraoral scanners and to propose a method to reduce errors of digital impressions.

Materials and methods : Two implant fixtures(UFII, DIO Implant, Busan, Republic of Korea) were inserted in the acrylic resin dentiform reproducing a completely edentulous mandible. Digital images were obtained by taking digital impressions with a dental model scanner(S600 ARTI model scanner, Zirkonzhan, South Tyrol, Italy) after connecting the digital scan adapter to the implant fixtures, and the images were used as those of the control group. Conventional and digital impression techniques were employed to take impressions for production of the implant superstructure connecting the two implants. This study was conducted categorized by a total of six experimental groups; Group 1 – Closed tray impression technique with transfer impression coping, Group 2 – Open tray impression technique with pick-up impression coping(non-splinted), Group 3 – Open tray impression technique with pick-up impression coping(splinted). Group 4 – Digital impression with scan adapter (non-splinted), Group 5 – Digital impression with scan adapter and reference marker, Group 6 – Digital impression with scan adapter (splinted). In Group 1, 2, and 3, a conventional impression technique was introduced using an impression body. A plaster model was made after taking impressions by producing the same shape of an individual tray with a 3D printer(ProJet® 3510 DP Pro, 3D Systems, Rock Hill, SC, USA) to adjust evenly the thickness of impression body, and digital images were acquired with a dental model scanner after connecting the digital impression coping to the imitation model. In Group 4, 5, and 6, digital images were obtained with an intraoral scanner(Trios®, 3shape Dental Systems, Copenhagen, Denmark) after connecting the scan adapter to the implant fixtures inserted in the dentiform model. Digital images of six experimental groups were matched with those of the control group using the optimal matching algorithm of a 3D image analysis program(Geomagic Design X 2014; 3D systems, USA), and scanning errors were calculated. One-Way ANOVA test was applied to assess the significance between six experimental groups(p<0.05), and a multiple comparison post-hoc test was performed using Bonferroni correction.

Results : Average error values between the experimental groups and the control group in Group 1∼6 were 0.00600±0.00245mm, 0.00686±0.00431mm, 0.00490±0.00296mm, 0.01042±0.00179mm, 0.00566±0.00303mm, and 0.00606±0.00221mm, respectively. The greatest average error value was observed in Group 4, which shows statistically significant differences with other groups except for Group 2. There were no statistically significant differences between other groups except for Group 4.

Conclusion : The digital impression taking by an intraoral scanner can be an alternative to a conventional impression technique because showing clinically acceptable errors in producing the fixed implant superstructure of completely edentulous mandible. It is recommended for taking more accurate impressions to place the reference marker between digital impression coping or to take digital impressions by connecting two digital impression coping when taking digital impressions of two implants in the edentulous condition.

Key words: Accuracy, Intraoral scanner, Digital impression, Implant superstructure, Reference marker