Implant scanning workflows: Accuracy of registration methods for integrating intraoral scans containing soft tissue and tooth position information

Abstract

Statement of problem

An implant scanning workflow involves recording different intraoral scans containing all the information needed to fabricate an implant-supported prosthesis. The accuracy of these implant scanning workflow registration methods remains unknown.

Purpose

The purpose of this in vitro study was to compare the accuracy of different implant scanning workflows for registering the soft tissue and tooth position information scans recorded by using 5 intraoral scanners (IOSs).

Material and methods

A maxillary edentulous stone cast with 6 implant abutment analogs (MultiUnit Abutment Replica) and 2 screw-retained implant-supported interim restorations (from the right first molar to the left canine and from the left first premolar to the left first molar) were obtained. Three markers were attached on the palatal surface of the cast on the anterior palatine raphe and right and left first molar positions, and 4 markers were attached on the palatal surface of the right and left second premolar and right and left lateral incisor of the interim prostheses. Afterwards, 5 composite resin (CR) reference landmarks were created on the palatal surface of the cast on the anterior palatine raphe, right and left first premolar, and right and left first molar. Additionally, a screw was placed in the posterior palatine raphe, simulating a temporary anchorage device (TAD). The interim prostheses were positioned in the implant analogs of the cast and digitized by using a laboratory scanner (T710). Five groups were created depending on the IOS: TRIOS 5, i700, Elite, iTero, and Primescan groups. A tooth position, soft tissue information, and soft tissue with existing teeth scans were obtained by using each IOS. Six subgroups were created depending on the reference landmarks used to register the scans: 3 or 5 CR landmarks (3CR or 5RC subgroup, respectively), existing teeth (teeth subgroup), existing teeth combined with 2 CR landmarks (teeth+2CR subgroup), TAD (TAD subgroup), TAD combined with 1 CR landmark (TAD+1CR subgroup). Twelve linear measurements were performed on the control scans and on each specimen among the 7 markers. Trueness was analyzed by using 2-way ANOVA and the pairwise comparison Tukey tests (α=.05). Precision was evaluated by using the Levene and pairwise comparisons tests (α=.05).

Results

Trueness discrepancies were found among the groups (P<.001) and subgroups (P<.001), with a significant group*subgroup interaction (P=.004). The Tukey test showed that the Primescan and iTero systems obtained worse trueness than the other groups. Also, the TAD and Teeth subgroups obtained worse trueness than the other subgroups tested. All the groups and subgroups were significantly different from each other (P<.05).

Conclusions

The IOS and reference landmarks tested impacted the trueness and precision of the registration of soft tissue and tooth position information scans.