Influence of planning software and surgical template design on the accuracy of static computer assisted implant surgery performed using surgical guides fabricated with material extrusion technology: An in vitro study

Impact of the superimposition methods on accuracy analyses in complete-arch digital implant investigation

OBJECTIVES

To measure the impact of the superimposition methods on accuracy analyses in digital implant research using an ISO-recommended 3-dimensional (3D) metrology-grade inspection software.

MATERIALS AND METHODS

A six-implant edentulous maxillary model was scanned using a desktop scanner (7Series; DentalWings; Montreal, Canada) and an intraoral scanner (TRIOS 4; 3Shape; Copenhagen, Denmark) to generate a reference and an experimental mesh, respectively. Thirty experimental standard tesselletion language (STL) files were superimposed onto the reference model's STL using the core features of six superimposition methods, creating the following groups: initial automated pre-alignment (GI), landmark-based alignment (G1), partial area-based alignment (G2), entire area-based alignment (G3), and double alignment combining landmark-based alignment with entire model area-based alignment (G4 ) or the scan bodies' surface (G5). The groups underwent various alignment variations, resulting in sixteen subgroups (n = 30). The alignment accuracy between experimental and reference meshes was quantified by using the root mean square (RMS) error as trueness and its fluctuation as precision. The Kruskal-Wallis test with a subsequent adjusted post-hoc Dunn's pairwise comparison test was used to analyze the data (α = 0.05). The reliability of the measurements was assessed using the intraclass correlation coefficient (ICC).

RESULTS

A total of 480 superimpositions were performed. No significant differences were found in trueness and precision among the groups (p > 0.05), except for partial area-based alignment (p < 0.001). Subgroup analysis showed significant differences for partial area-based alignment considering only one scan body (p < 0.001). Initial automated alignment was as accurate as landmark-based, partial, or entire area-based alignments (p > 0.05). Double alignments did not improve alignment accuracy (p > 0.05). The entire area-based alignment of the scan bodies' surface had the least effect on accuracy analyses.

CONCLUSIONS

Digital oral implant investigation remains unaffected by the superimposition method when ISO-recommended 3D metrology-grade inspection software is used. At least two scan bodies are needed when considering partial area-based alignments.

CLINICAL SIGNIFICANCE

The superimposition method choice within the tested ISO-recommended 3D inspection software did not impact accuracy analyses in digital implant investigation.

Dimensional accuracy and simulation-based optimization of polyolefins and biocopolyesters for extrusion-based additive manufacturing and steam sterilization

Polyolefins exhibit robust mechanical and chemical properties and can be applied in the medical field, e.g. for the manufacturing of dentures. Despite their wide range of applications, they are rarely used in extrusion-based printing due to their warpage tendency. The aim of this study was to investigate and reduce the warpage of polyolefins compared to commonly used filaments after additive manufacturing (AM) and sterilization using finite element simulation. Three types of filaments were investigated: a medical-grade polypropylene (PP), a glass-fiber reinforced polypropylene (PP-GF), and a biocopolyester (BE) filament, and they were compared to an acrylic resin (AR) for material jetting. Square specimens, standardized samples prone to warpage, and denture bases (n = 10 of each group), as clinically relevant and anatomically shaped reference, were digitized after AM and steam sterilization (134 °C). To determine warpage, the volume underneath the square specimens was calculated, while the deviations of the denture bases from the printing file were measured using root mean square (RMS) values. To reduce the warpage of the PP denture base, a simulation of the printing file based on thermomechanical calculations was performed. Statistical analysis was conducted using the Kruskal-Wallis test, followed by Dunn's test for multiple comparisons. The results showed that PP exhibited the greatest warpage of the square specimens after AM, while PP-GF, BE, and AR showed minimal warpage before sterilization. However, warpage increased for PP-GF, BE and AR during sterilization, whereas PP remained more stable. After AM, denture bases made of PP showed the highest warpage. Through simulation-based optimization, warpage of the PP denture base was successfully reduced by 25%. In contrast to the reference materials, PP demonstrated greater dimensional stability during sterilization, making it a potential alternative for medical applications. Nevertheless, reducing warpage during the cooling process after AM remains necessary, and simulation-based optimization holds promise in addressing this issue.

Accuracy of additively manufactured and steam sterilized surgical guides by means of continuous liquid interface production, stereolithography, digital light processing, and fused filament fabrication

Different printing technologies can be used for prosthetically oriented implant placement, however the influence of different printing orientations and steam sterilization remains unclear. In particular, no data is available for the novel technology Continuous Liquid Interface Production. The objective was to evaluate the dimensional accuracy of surgical guides manufactured with different printing techniques in vertical and horizontal printing orientation before and after steam sterilization. A total of 80 surgical guides were manufactured by means of continuous liquid interface production (CLIP; material: Keyguide, Keyprint), digital light processing (DLP; material: Luxaprint Ortho, DMG), stereolithography (SLA; Surgical guide, Formlabs), and fused filament fabrication (FFF; material: Clear Base Support, Arfona) in vertical and horizontal printing orientation (n = 10 per subgroup). Spheres were included in the design to determine the coordinates of 17 reference points. Each specimen was digitized with a laboratory scanner after additive manufacturing (AM) and after steam sterilization (134 °C). To determine the accuracy, root mean square values (RMS) were calculated and coordinates of the reference points were recorded. Based on the measured coordinates, deviations of the reference points and relevant distances were calculated. Paired t-tests and one-way ANOVA were applied for statistical analysis (significance p < 0.05). After AM, all printing technologies showed comparable high accuracy, with an increased deviation in z-axis when printed horizontally. After sterilization, FFF printed surgical guides showed distinct warpage. The other subgroups showed no significant differences regarding the RMS of the corpus after steam sterilization (p > 0.05). Regarding reference points and distances, CLIP showed larger deviations compared to SLA in both printing orientations after steam sterilization, while DLP manufactured guides were the most dimensionally stable. In conclusion, the different printing technologies and orientations had little effect on the manufacturing accuracy of the surgical guides before sterilization. However, after sterilization, FFF surgical guides exhibited significant deformation making their clinical use impossible. CLIP showed larger deformations due to steam sterilization than the other photopolymerizing techniques, however, discrepancies may be considered within the range of clinical acceptance. The influence on the implant position remains to be evaluated.

A comprehensive review and update on the current state of computer-assisted rehabilitation in implant dentistry

AIM

This paper provides a comprehensive review of the established concepts and newer developments related to computer-assisted implant rehabilitation.

METHODS

Two independent researchers searched the English literature published to 31st December 2023 in the PubMed/Medline database for primary and secondary research and related publications on computer-assisted implant planning, computer-assisted implant placement and computer-assisted implant restoration.

RESULTS

A total of 58,923 papers were identified, 198 relevant papers were read in full text and 110 studies were finally included. Computer-assisted implant rehabilitation was found to result in more precise implant positioning than freehand placement. Advantages include reduced trauma and surgery time; disadvantages include reduced primary implant stability and higher cost.

CONCLUSION

Computer-assisted surgery is particularly indicated in cases of critical anatomy, but may encounter limitations in terms of cost, restricted mouth opening, visibility and adjustment of the surgical guides and the need for prior familiarisation with the procedure. Nonetheless, this surgical technique reduces the post-implant placement complication rate.

Comparative Evaluation of Accuracy of Adjacent Parallel Implant Placements Between Dynamic Navigation and Static Guide: A Prospective Study

Aim The study aims to compare the accuracy of dynamic navigation (DN) and static guides (SGs) for simultaneous adjacent parallel placement of implants, the time taken for the surgery, and the ease of handling the instruments. Materials and methods This prospective trial was carried out at the Department of Implantology of Saveetha Dental College from October 2022 to February 2023. A total of 20 patients who needed simultaneous adjacent dental implants were allocated randomly into two groups: Group 1 SG surgery and Group 2 DN surgery. Forty implants were placed, 20 under DN and 20 under SG. Bucco-lingual displacement, apico-coronal displacement, mesiodistal displacement, and mesiodistal angulation were compared between the two groups. The patients' data in both groups were evaluated by operating surgeons along with the surgical time taken and the ease of handling of instruments. Results The 20 patients who underwent implant placement in the DN and SG groups all had adjacent missing teeth in posterior sites, including lower posteriors (70%) and upper posteriors (30%). There was improved precision in relation to the mesiodistal displacement and angulation of the anterior implant of the adjacent parallel implants. The mesiodistal displacement in Group 1 (SG) was 5.61 + 3.1 mm, which was higher than Group 2 (DN), which was 0.55 + 0.56 mm. The mesiodistal angulation was 3.1 + 2.9 degrees in Group 2 and 0.42 + 0.5 degrees in Group 1. The second implant had a significant difference (p < 0.005) in mesiodistal displacement, mesiodistal angulation, and bucco-lingual displacement. The difference between the intergroup surgical time (mean + SD) in Group 1 was 30 + 4.5 mins and in Group 2 was 60.7 + 10.1 mins, with p < 0.05 statistically significant. The comfort of the operator was better in the SG group. Conclusion Any digitally aided implant placement technique can improve placement accuracy but each has its downfalls. Achieving the highest levels of precision and long-lasting prosthetic results hinges on both the suitability of the chosen case and the expertise of the surgeon performing the implant placement.

Accuracy in static guided implant surgery: Results from a multicenter retrospective clinical study on 21 patients treated in three private practices

PURPOSE

To evaluate the accuracy of a static computer-assisted implant surgery (s-CAIS) system across different private practices.

METHODS

This retrospective clinical study was based on data retrieved from 21 patients who received 61 implants between 2018 and 2020 in 3 private practices run by surgeons with extensive experience with s-CAIS. All patients were treated using the same s-CAIS system, planning software, template manufacturing process, and surgical guides. The standard tessellation language (STL) file of the intraoral scan of the fixture taken immediately after implant placement was matched with that of the preoperative plan for comparisons of preoperative and planned implant positions with postoperative and actual implant positions. The study outcomes were linear and angular deviations between the planned and actual implant positions.

RESULTS

No surgical or postsurgical complications occurred. The overlap of the two STL files resulted in a mean angular deviation of 2.94° The mean linear deviation at the implant shoulder was 0.73 mm, and that at the apex was 1.06 mm. The mean vertical deviations at the implant shoulder and the apex were 0.29 mm and 0.01 mm, respectively.

CONCLUSION

All cases showed satisfactory accuracy within the limits of this study (small number of patients and retrospective design). These results might be related to the use of a standardized digital workflow by experienced operators.

STATEMENT OF CLINICAL RELEVANCE

The study shows that careful control of each step, from data acquisition to final execution, is key for the accuracy of stent-guided systems.

Accuracy of freehand versus guided immediate implant placement: A randomized controlled trial

PURPOSE

This randomized controlled trial (RCT) aimed to compare the accuracy of immediate implant placement with freehand and static guided surgery.

METHODS

An RCT was conducted on 61 subjects who received a total of 80 dental implants. The enrolled patients were randomly allocated to two groups: freehand surgery (control group, n = 40 implants) and static guided surgery with R2Gate® (Megagen, Gyeongbuk, South Korea, test group, n = 40 implants). Crestal and apical deviations in both mesiodistal and buccolingual dimensions, as well as depth and angular deviations, were calculated by comparing the three-dimensional (3D) position of the implant in the planning software with the final implant position, revealed by an intraoral scan of the fixture after placement. The Mann-Whitney test was used for comparative assessment.

RESULTS

In the freehand group (control), crestal deviations of 1.13 ± 0.89 mm and 1.00 ± 0.76 mm were found in the mesiodistal and buccolingual directions, respectively, versus 0.34 ± 0.26 mm (p<0.001) and 0.37 ± 0.24 mm (p = 0.03) in the static guided surgery group (test). Apical deviation was also higher in the freehand group (control) than in the static guided surgery group (test) in the mesiodistal (4.04 ± 1.90 mm vs. 0.97 ± 0.55 mm, p = 0.04) and buccolingual directions (3.46 ± 1.82 mm vs. 0.94 ± 0.67 mm, p = 0.02). Freehand surgery had greater angular deviation (6.09° ± 3.23) compared to guided surgery (0.83° ± 0.53, p = 0.02). However, depth deviation was similar in the freehand surgery group (2.24 ± 1.58 mm) and static guided surgery group (0.66 ± 0.43, p = 0.09).

CONCLUSIONS

Immediate implant placement with static guided surgery demonstrated better accuracy than freehand surgery.

STATEMENT OF CLINICAL RELEVANCE

Guided implant surgery showed fewer deviations compared to freehand surgery in fresh extraction sockets; therefore, the use of static guides should be given preference over the freehand modality.

Hybrid Navigation Technique for Improved Precision in Implantology

The hybrid navigation technique involves the merging of the Dynamic navigation (DN) system (Navident, Claronav, Canada) and static navigation technique (3Shape, Copenhagen, Denmark). Combining the advantages of both techniques, devising a protocol of hybrid navigation will be advantageous to eliminate the difficulties faced by operators in using either methods separately. Three patients requiring dental implants were included in this study. This requires the cone beam computed tomography (CBCT) (Digital Imaging and Communications in Medicine (DICOM) data) and intra-oral scan (Standard Tessellation Language (STL) format) data for the accurate planning of the implant positions in both the static and dynamic approaches. The steps carried out were repeated for each of the patients, the accuracy of the implant placement was verified postoperatively by merging the CBCT data pre and post through the Evalunav software (NaviDent, Claronav). The accuracy of the implants placed were assessed based on the mesio-distal, bucco-lingual, apical deviations in distance and in angulation. The semi-robotic DN and static guide combination as a hybrid technique is an interesting method to improve the accuracy of flapless implant surgeries and can be used in cases where the anatomical landmarks are determinant factors for the implant placement.