Digital immediate tooth restoration: Fabricating acrylic resin interim crowns from CBCT scans for immediate implant-supported prostheses: A case series

Abstract

Statement of problem: Adjusting an interim screw-retained crown made of acrylic resin for maintenance of peri-implant soft tissues after immediate implant insertion requires accuracy and time. Assessments of these factors by using digital techniques are sparse.

Purpose: The purpose of this clinical study was to describe a technique to fabricate an acrylic resin interim crown by using the data acquired from a cone beam computed tomography (CBCT) scan. The 3D tomography files were converted to a standard tessellation language (STL) file format used to print or to mill the interim crown with a technique called digital immediate tooth restoration (DITR). Additionally, the chair time spent during the prosthetic phase was evaluated in comparison with a protocol in which a standard interim crown (SIC) was fabricated with an indirect-direct technique.

Material and methods: Patients who needed to replace a single nonrestorable tooth were treated from February to June 2018 with an immediately placed implant and an acrylic resin screw-retained interim prosthesis that was connected to the implant immediately after placement of the implant. The participants were divided into 2 groups according to the acrylic resin interim crown fabrication technique: group DITR and group SIC. The average time to finalize the prostheses was compared between the groups. The total chair time (TCT) taken for the adaptation of the interim crown was noted and distinguished in 3 different times corresponding to each phase of adaptation of the interim restoration of the interproximal contact areas (CT1), adaption of the postextractive alveolar bone walls (CT2), and adaption of the occlusal contacts (CT3). For each time, the number of changes (N-CT1, N-CT2, N-CT3, and TN) needed to complete each prosthetic phase was also marked and observed. Generalized linear mixed models and generalized linear models were used for data analysis. All the sites were definitively restored with a screw-retained crown after 6 months of healing, and the participants were provided with standard hygiene recall appointments for the next year.

Results: A total of 82 crowns at sites distributed across the mandible and the maxilla were included in the study. Thirty-five were restored with an SIC and 47 with a DITR interim crown. None of the implants were lost during the 18-month follow-up period. The analysis of the chair times registered for the adaptation of the interim crown to the implant healing abutment and to the neighboring teeth between the 2 groups showed a reduction if a DITR interim crown was used (average CT1 of 15 ±14 seconds, CT2 of 2 ±5 seconds, CT3 of 59 ±19 seconds, and TCT of 76 ±28 seconds for group DITR and average CT1 of 135 ±27 seconds, CT2 of 185 ±30 seconds, CT3 of 73 ±16 seconds, and TCT of 394 ±61 seconds for group SIC). The number of corrections to finalize the interim crown adaptations was lower for the group DITR (0.81 ±0.74 for N-CT1, 0.19 ±0.39 for N-CT2, and 2.81 ±0.74 for N-CT3) when compared with the number of corrections needed for the group SIC (4.37 ±0.81 for N-CT1, 5.57 ±0.77 for N-CT2, and 3.86 ±0.64 for N-CT3).

Conclusions: The data from CBCT scans led to interim acrylic resin crowns that needed fewer adjustments with the immediate implant placement and interim restoration approach, reducing chair time.