Impact of number of registration points on the positional accuracy of a prosthetic treatment plan incorporated into a cone beam computed tomography scan by surface scan registration: An in vitro study

Accuracy of manual and artificial intelligence-based superimposition of cone-beam computed tomography with digital scan data, utilizing an implant planning software: A randomized clinical study

OBJECTIVES

To investigate the accuracy of conventional and automatic artificial intelligence (AI)-based registration of cone-beam computed tomography (CBCT) with intraoral scans and to evaluate the impact of user's experience, restoration artifact, number of missing teeth, and free-ended edentulous area.

MATERIALS AND METHODS

Three initial registrations were performed for each of the 150 randomly selected patients, in an implant planning software: one from an experienced user, one from an inexperienced operator, and one from a randomly selected post-graduate student of implant dentistry. Six more registrations were performed for each dataset by the experienced clinician: implementing a manual or an automatic refinement, selecting 3 small or 3 large in-diameter surface areas and using multiple small or multiple large in-diameter surface areas. Finally, an automatic AI-driven registration was performed, using the AI tools that were integrated into the utilized implant planning software. The accuracy between each type of registration was measured using linear measurements between anatomical landmarks in metrology software.

RESULTS

Fully automatic-based AI registration was not significantly different from the conventional methods tested for patients without restorations. In the presence of multiple restoration artifacts, user's experience was important for an accurate registration. Registrations' accuracy was affected by the number of free-ended edentulous areas, but not by the absolute number of missing teeth (p < .0083).

CONCLUSIONS

In the absence of imaging artifacts, automated AI-based registration of CBCT data and model scan data can be as accurate as conventional superimposition methods. The number and size of selected superimposition areas should be individually chosen depending on each clinical situation.

Digital registration versus cone-beam computed tomography for evaluating implant position: a prospective cohort study

BACKGROUND

Postoperative cone-beam computed tomography (CBCT) examination is considered a reliable method for clinicians to assess the positions of implants. Nevertheless, CBCT has drawbacks involving radiation exposure and high costs. Moreover, the image quality can be affected by artifacts. Recently, some literature has mentioned a digital registration method (DRM) as an alternative to CBCT for evaluating implant positions. The aim of this clinical study was to verify the accuracy of the DRM compared to CBCT scans in postoperative implant positioning.

MATERIALS AND METHODS

A total of 36 patients who received anterior maxillary implants were included in this clinical study, involving a total of 48 implants. The study included 24 patients in the single implant group and 12 patients in the dual implant group. The postoperative three-dimensional (3D) positions of implants were obtained using both CBCT and DRM. The DRM included three main steps. Firstly, the postoperative 3D data of the dentition and intraoral scan body (ISB) was obtained through the intraoral scan (IOS). Secondly, a virtual model named registration unit which comprised an implant replica and a matching ISB was created with the help of a lab scanner and reverse engineering software. Thirdly, by superimposing the registration unit and IOS data, the postoperative position of the implant was determined. The accuracy of DRM was evaluated by calculating the Root Mean Square (RMS) values after superimposing the implant positions obtained from DRM with those from postoperative CBCT. The accuracy of DRM was compared between the single implant group and the dual implant group using independent sample t-tests. The superimposition deviations of CBCT and IOS were also evaluated.

RESULTS

The overall mean RMS was 0.29 ± 0.05 mm. The mean RMS was 0.30 ± 0.03 mm in the single implant group and 0.29 ± 0.06 mm in the dual implant group, with no significant difference (p = 0.27). The overall registration accuracy of the IOS and CBCT data ranged from 0.14 ± 0.05 mm to 0.21 ± 0.08 mm.

CONCLUSION

In comparison with the 3D implant positions obtained by CBCT, the implant positions located by the DRM showed clinically acceptable deviation ranges. This method can be used in single and dual implant treatments to assess the implant positions.

Assessment of guide fitting using an intra-oral scanner: An in vitro study

OBJECTIVES

The aim of this study was to evaluate the capacity of an intra-oral scanner (IOS) to assess the position of an endodontic guide in vitro.

METHODS

Fourteen extracted human teeth were placed into a maxillary model and scanned using computed tomography and a reference laboratory scanner. An ideal endodontic guide was then created and modified by adding defects of different thicknesses to simulate incorrect positions: 50 μm, 150 μm, 400 μm, and 1000 μm. For each thickness, guides were printed three times and each guide was scanned by three experimented operators using a Trios 4 IOS (3Shape, Copenhagen, Denmark). The 36 scans were compared using a best-fit alignment to the master model without defect to define the accuracy of the method and the positioning error.

RESULTS

The IOS presented a mean trueness of 1.28 μm (SD= 12.70) and a mean precision of 11.52 μm (SD= 62.17). Considering all sizes of defect, the mean measured position of the endodontic guide was highly correlated (R>0.99) with the expected position. Compared to the ideal guide, there was a mean linear deviation of 46.11 μm (SD= 23.21) and a mean angular deviation of 5.9° (SD= 1.2); this deviation was not influenced by the operator.

CONCLUSION

The present study found that an IOS had good performance to detect a positioning error of the endodontic guide in vitro.

CLINICAL SIGNIFICANCE

This new application of IOS has a promising potential in clinical practice to assist practitioners during the fitting of guides.

How to Avoid Errors When Using Navigation to Place Implants - A Narrative Review

PURPOSE

Surgeons placing implants use navigation for implant placement accuracy. The importance of this review is to document the sources of error that are involved with navigation so surgeons can recognize factors to decrease error. The objective is to provide surgeons with a reference to optimize navigation.

METHODS

Pubmed.gov was the information source. Years reviewed included 2010 to 2022. The inclusion criteria included only articles in peer-reviewed journals. In vitro results were included only if they involved testing of variables microgap, cone beam computerized tomography (CBCT) accuracy evaluation, or accuracy of printed models. Variables were searched and evaluated. Data collected included the objectives and outcomes of the study including statistical significance. The conclusions made by the authors were confirmed by evaluating the data analysis, and then these conclusions were listed in each error-related topic.

RESULTS

The search used terms which included guided implant surgery complications (n = 4,029), accuracy of CBCT scanners (n = 319), accuracy of implant navigation (n = 983), and the error between drills and static guides (n = 3). From this search, 70 articles were collated that satisfied the inclusion criteria. There are multiple sources of error that are less than 1 mm, including but not limited to errors associated with the scanner and method for scanning, errors associated with merging scanned files with the CBCT scan, errors using different guide stent fabrication methods, errors associated with intraoperative techniques, the learning curve, and planning error. If small errors are not taken into consideration, implant placement errors can exceed 1-2 mm of platform location and angulation errors in excess of 8°.

CONCLUSION

The surgeon needs to take into consideration controllable factors that will result in the avoidance of implant malposition and thus be able to effectively utilize navigation for accurate implant placement.

The impact of cone beam computer tomography field of view on the precision of digital intra-oral scan registration for static computer-assisted implant surgery: A CBCT analysis

OBJECTIVES

Registration of intra-oral surface scans to cone beam computer tomography (CBCT) is critical in the digital workflow for static computer-aided implant surgery (sCAIS). This study aimed to assess the impact of CBCT field of view (FoV) on the precision of digital intra-oral scan registration.

MATERIALS AND METHODS

Cone beam computer tomography data and intra-oral scans from 20 patients were included. Small FoV CBCT's were created by digitally segmenting a large FoV into three sextants. Virtual implant planning was performed. Digital intra-oral scans were repeatedly registered onto their corresponding large and small FoV CBCT datasets. The distances and angulations between the matching implant positions of each repeated registration were used to determine the precision of the registration process. Wilcoxon Signed Rank Paired Tests were used to compare the differences between large FoV and small FoV. The threshold for statistical significance was set at p = .05.

RESULTS

Differences in 3D implant position based on the registration precision between small FoV and large FoV present at both the implant entry point (0.37 ± 0.25 mm vs 0.35 ± 0.23 mm, p = .482) and implant tip (0.49 ± 0.34 mm vs 0.37 ± 0.24 mm, p < .001). Differences in overall angular precision were observed between small FOV and large FoV (1.43 ± 1.36° vs 0.51 ± 0.38°, p < .001).

CONCLUSION

CBCT with a small FoV is accompanied by greater precision errors in intra-oral scan registration. However, when sufficient well-distributed teeth are visible in small FoV CBCT, the precision of digital intra-oral scan registration appears to be within clinically acceptable limits for sCAIS.

Influence of digital implant analog design on the positional trueness of an analog in additively manufactured models: An in-vitro study

BACKGROUND

Limited evidence exists regarding the accuracy of implant analog position in printed models, particularly when implant analogs with varying designs are used.

PURPOSE

To evaluate the effect of digital implant analog (DIA) design on the trueness of their position in additively manufactured digital implant models (DIMs) and to compare with that of a conventional implant analog in a stone cast.

MATERIALS AND METHODS

A dentate maxillary model with a conventional implant analog (Nobel Biocare Implant Replica 4.3 mm CC RP) at left second premolar site was digitized by using a laboratory scanner (3Shape D2000) and a (SB) scan body to generate the master standard tessellation language (STL) file (M0). 12 custom trays were fabricated on M0 file and conventional polyvinylsiloxane impressions of the model were made. All impressions were poured after inserting conventional implant analogs (Nobel RP Implant Replica) (Group A). Model was then digitized with an intraoral scanner (TRIOS 3) and the same SB, and DIMs with three different DIA designs (Nobel Biocare [Group B], Elos [Group C], and NT-trading [Group D]) were generated (Dental System-Model Builder). 12 DIMs of each design were additively manufactured and corresponding DIAs were inserted. All models were digitized by using the same laboratory scanner and SB, and these STLs were transferred to a 3D analysis software (Geomagic Control X), where the STL files of the models were superimposed over M0. Linear and 3D deviations at three selected points on SB (implant-abutment connection, most cervical point on SB, and most coronal point on SB) as well as angular deviations on two planes (buccolingual and mesiodistal) were calculated. Analysis of variance (ANOVA) and Bonferroni corrected t-tests were used to analyze the trueness of implant analog positions (α = 0.05).

RESULTS

The interaction of main effects significantly affected linear (p < 0.001) and angular deviations (p = 0.020). At point 1, group D had higher deviations than groups A and B (p ≤ 0.015). In addition, groups A and D had higher deviations than group B at point 4 (p < 0.001). While group C had similar linear deviations to those of other groups at point 1 and point 4 (p ≥ 0.192), the differences among test groups at point 2 were nonsignificant (p ≥ 0.276). Group B had lower angular deviations than groups C (p = 0.039) and D (p = 0.006) on buccolingual plane.

CONCLUSIONS

Analog design affected the trueness of analog position as proprietary, pressure/friction fit DIA (group B) had higher linear trueness than screw-retained DIA (Group D) and conventional implant analog (group A). In addition, pressure/friction fit DIA had the highest angular trueness among tested DIAs.

Digital versus radiographic accuracy evaluation of guided implant surgery: an in vitro study

Background

Cone-beam computed tomography (CBCT) is the most widely used method for postsurgical evaluation of the accuracy of guided implant surgery. However, the disadvantages of CBCT include radiation exposure, artifacts caused by metal implants, and high cost. Few studies have introduced a digital registration method to replace CBCT for evaluating the accuracy of guided surgery. The purpose of this study was to compare digital registration to conventional CBCT in terms of the capacity to evaluate the implant positioning accuracy of guided surgery.

Materials and methods

This in vitro study included 40 acrylic resin models with posterior single mandibular tooth loss. Guided surgery software was used to determine the optimal implant position; 40 tooth-supported fully guided drilling templates were designed and milled accordingly. After the guided surgery, the accuracies of the surgical templates were evaluated by conventional CBCT and digital registration. For evaluation by conventional CBCT, postsurgical CBCT scans of the resin models were performed. The CBCT data were reconstructed and superimposed on the implant planning data. For digital registration, we constructed a virtual registration unit that consisted of an implant replica and a scan body. Next, we obtained postsurgical optical scans of resin models with the scan body. The postsurgical implant position was identified by superimposition of the registration unit and optical scan data. The implant planning data and postsurgical implant position data were superimposed; deviations were reported in terms of distance for implant entry/apex point and in terms of angle for the implant axis. Interclass correlation coefficients (ICCs) and Bland–Altman plots were used to analyze the agreement between the two evaluation methods.

Results

The ICCs between the two methods were 0.986, 0.993, and 0.968 for the entry point, apex point, and angle, respectively; all were significantly greater than 0.75 (p < 0.001). Bland–Altman plots showed that the 95% limits of agreement of the differences were − 0.144 to + 0.081 mm, − 0.135 to + 0.147 mm, and − 0.451° to + 0.729° for the entry point, apex point, and angle, respectively; all values were within the maximum tolerated difference.

Conclusion

Conventional CBCT and digital registration showed good agreement in terms of evaluating the accuracy of implant positioning using tooth-supported surgical templates.

Evaluation of different registration methods and dental restorations on the registration duration and accuracy of cone beam computed tomography data and intraoral scans: a retrospective clinical study

OBJECTIVES

To evaluate whether the accuracy and duration of registration for cone beam computed tomography (CBCT) and intraoral scans differ according to the method of registration and ratio of dental restorations to natural teeth.

MATERIALS AND METHODS

CBCT data and intraoral scans of eligible patients were grouped as follows according to the ratio of the number of dental restorations to the number of natural teeth (N): group 1, N = 0%; group 2, 0% < N < 50%; group 3, 50% ≤ N < 100%; and group 4, 100% ≤ N. Marker-free registration was performed with a deep learning-based platform and four implant planning software with different registration methods (two point-based, one surface-based, and one manual registration software) by a single operator, and the time consumption was recorded. Registration accuracy was evaluated by measuring the distances between the three-dimensional models of CBCT data and intraoral scans.

RESULTS

A total of 36 patients, one jaw per patient, were enrolled. Although registration accuracy was similar, the time consumed for registration significantly differed for the different methods. The deep learning-based registration method consumed the least time. Greater proportions of dental restorations significantly reduced the registration accuracy for semi-automatic and deep learning-based methods and reduced the time consumed for semi-automatic registration.

CONCLUSIONS

No superiority in registration accuracy was found. The proportion of dental restorations significantly affects the accuracy and duration of registration for CBCT data and intraoral scans.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: KCT0006710 CLINICAL RELEVANCE: Registration accuracy for virtual implant planning decreases when the proportion of dental restorations increases regardless of registration methods.

Comparison of the virtual techniques in registering single implant position with a universal-coordinate system: An in vitro study

OBJECTIVES

The aim of this in-vitro study was to compare the virtual techniques for registering single-implant position to the physical gold standard using a universal-coordinate system.

MATERIALS AND METHODS

Thirty dentate maxillary resin models with a dental implant inserted in the incisor region were prepared. On each model, a tooth-supported acrylic stent with a 1 cm x 1 cm x 1 cm cubic-corner (CC) was prepared. The Cartesian x,y,z-coordinate of the implant neck and apex were measured physically by a coordinate-measuring machine (CMM) with reference to this CC and served as the gold-standard. The resin models were scanned by a benchtop scanner (Group BS), cone-beam computed tomography (Group CBCT), and intraoral scanner (Group IOS). Stone casts, poured from open-tray polyether impression of the resin models, were scanned by the benchtop scanner (Group BS-cast). The implant neck and apex coordinates with reference to the CC were measured and the differences in the coordinates (∆x, ∆y, ∆z) and distance r from the gold standard were calculated. The data were analyzed by one-sample t-test and one-way ANOVA/Kruskal-Wallis test with the level of significance set at 0.05.

RESULTS

The implant neck and apex positions of Group BS were statistically different from that of the CMM, r>0 (p<0.001). Group IOS showed a significant less ∆z and r at the implant neck than Group BS-cast (p = 0.006). No significant difference was found in the coordinates and distance at implant apex among Groups BS, CBCT, IOS and BS-cast.

CONCLUSIONS

The physical measurements could be adopted as the gold standard in assessing the single-implant positions. The IOS was more accurate in registering the single-implant neck positions than scanning of the cast.

CLINICAL SIGNIFICANCE

A universal-coordinate system defined by the cubic-corner allows comparing the virtual techniques in registering single-implant positions to the physical gold standard.

The question about the numerical value and quantitative data transfer of implant prosthodontics-orom experience guidance to digital guidance

The correct implant site design and placement are the basic clinical techniques that must be known for implant restoration. For a long time, most implants have been placed by free hands, and the choice of site is mostly dependent on the accumulation of long-term experience of the surgeon. The selection of implant site guided by this experience analogy logic is often based on the surgeon's level of experience,which often makes it very easy to produce complications related to the implant restoration of the incorrect site. In contrast, a clinical program using digital guidance and real-time measurable verification has emerged based on the restoration-oriented implantation concept, which marks the formation of an accurate, measurable and verifiable whole-process digital implant prototype. Furthermore, from the perspective of surveying, the numerical requirements that digital implant restoration relies on are actually incomplete to the four elements of measurement, which leading to the doubts about its authenticity. This article will question the numbers in implant restoration, and conduct a preliminary demonstration, and propose a new reliable actual measurement and verification method of the correct location and the numerical requirements of the restoration space and a new clinical program that relies on numbers from the perspective of the evolution of digital restoration, guided implantology and actual measurement technology. And this article further discusses the current mainstream implant restoration technology based on experience analogy which cannot effectively support the whole process of digital implant restoration and provides a new logical cognitive basis for the final realization of the entire process of digital implant restoration.

Impact of Matching Point Selections on Image Registration Accuracy between Optical Scan and Computed Tomography

The point-based surface registration method involves the manual selection process of paired matching points on the data of computed tomography and optical scan. The purpose of this study was to investigate the impact of selection error and distribution of fiducial points on the accuracy of image matching between 3-dimensional (3D) images in dental planning software programs. Computed tomography and optical scan images of a partial edentulous dental arch were obtained. Image registration of the optical scan image to computed tomography was performed using the point-based surface registration method in planning software programs under different conditions of 3 fiducial points: point selection error (0, 1, or 2 mm), point distribution (unilateral, bilateral), and planning software (Implant Studio, Blue Bio Plan) (n = 5 per condition, N = 60). The accuracy of image registration at each condition was evaluated by measuring linear discrepancies between matched images at X, Y, and Z axes. Kruskal-Wallis test, Mann-Whitney U test with Bonferroni correction, and 3-way analysis of variance were used to statistically analyse the measurement data (α = 0.05). No statistically significant difference was exhibited between the 0 and 1 mm point mismatch conditions in either unilateral or bilateral point distributions. The discrepancy values in the 2 mm mismatch condition were significantly different from the other mismatch conditions, especially in the unilateral point distribution (P < 0.05). Strong interactions among point selection error, distribution, and software programs on the image registration were found (P < 0.001). Minor matching point selection error did not influence the accuracy of point-based automatic image registration in the software programs. When the fiducial points are distributed unilaterally with large point selection error, the image matching accuracy could be decreased.

Comparison of the Accuracy of Image Registration Methods for Merging Optical Scan and Radiographic Data in Edentulous Jaws

PURPOSE

The image registration of optical scans to radiographic images is essential for performing computer-guided implant surgery. This study aimed to evaluate the effect of different image matching conditions on the accuracy of image registration for computer-guided implant surgery in completely edentulous jaws.

MATERIALS AND METHODS

The optical scan image of a completely edentulous study model was registered to the respective cone-beam computed tomography data using three different image matching conditions: small point (SP), large point (LP), and entire surface (ES). For the SP and LP groups, gutta-percha markers (1.0 and 3.0 mm in diameter) were attached to a base template, and a radiopaque impression material was relined on the intaglio surface of template in the ES group. Image registration was performed by 20 operators in the images obtained from each group at an interval of 2 weeks (n = 20 in each group), and the registration accuracy was assessed by calculating the aligned position of the edentulous arch image. One-way analysis of variance with Tukey post hoc tests was used to compare the results among the groups (α = 0.05).

RESULTS

The mean registration error was significantly larger in the SP group (0.52 ± 0.19 mm) than in the LP group (0.29 ± 0.08 mm) and ES group (0.27 ±0.06 mm) (F = 24.689, p < 0.001). No difference was found between the LP and ES groups. The image matching discrepancy was more homogeneously distributed on the arch in the ES group than in the other groups.

CONCLUSION

The accuracy of image registration is affected by the size of the congruent area shown in the optical scan and radiographic images. The entire surface-based matching method is more accurate as compared to the small point-based matching method in the image registration for implant planning in full edentulous jaws.