Radiographic markers for merging virtual data sets

Superimposing digital arch scans onto cone beam computed tomography scans with metallic artifacts by applying a radiopaque occlusal registration material: A chairside dental technique

Precise alignment between digital arch scans and cone beam computed tomography (CBCT) scans is a crucial step in computer-aided implant planning and placement. However, clinicians frequently encounter challenges during this process when imaging patients with existing metal restorations or orthodontic devices, as these can introduce metallic artifacts on CBCT scans that lead to alignment deviations. The presented technique describes a straightforward approach using a radiopaque occlusal registration material as a radiographic marker to facilitate the alignment between digital arch scans and CBCT scans with metallic artifacts. This technique simplifies the clinical workflow by eliminating the need for additional radiographic templates or specialized devices, offering a cost-effective option for clinicians.

Single scanning of CBCT and intraoral scanning for guided implantation in terminal dentitions with multi-unit metal restorations: technical note

When anatomical landmarks are missing or obstructed by metal artefacts, it is challenging to accurately merge cone beam computed tomography (CBCT) and intraoral scanning (IOS) information, and the accuracy of the implant surgical guides would be compromised. This article describes a novel technical note using oral wound dressings and flowable resin as additional new radiopaque fiducial landmarks to design surgical guides for full-arch immediate implant placement. This technical note provided an accurate, convenient, and cost-effective option for the clinician.

The in-vitro accuracy of fiducial marker-based versus markerless registration of an intraoral scan with a cone-beam computed tomography scan in the presence of restoration artifact

OBJECTIVES

To determine the effect of restoration artifact ('metal artifact') on registration accuracy of an intraoral scan and cone-beam computed tomography (CBCT) scan, comparing fiducial marker-based registration with markerless registration.

MATERIALS AND METHODS

A maxillary model was fitted with multiple configurations of zirconia crowns to simulate various states of oral rehabilitation. Intraoral scans and CBCT scans (half and full rotation) were acquired. Registration was performed using markerless (point-based registration with surface-based refinement) and fiducial marker-based registration. Each experimental condition was repeated 10 times (n = 320). The absolute deviation was measured at the canines and first molars, and the average and maximum values were analysed using multiple linear regression.

RESULTS

R2 was 0.874 for average error and 0.858 for maximum error. For markerless registration, there were 0.041 mm (p < .001) and 0.045 mm (p < .001) increases in average and maximum error per crown, respectively. For fiducial marker-based registration, the effect of additional crowns was not statistically significant for average (p = .067) or maximum (p = .438) error. For a full arch of crowns, the regression model predicted average and maximum errors of 0.581 and 0.697 mm for the markerless technique, and 0.185 and 0.210 mm for the fiducial marker-based technique. Overall, the fiducial marker-based technique was more accurate for four or more crowns. The half rotation scan increased average error by 0.021 mm (p = .001) and maximum error by 0.029 mm (p < .001).

CONCLUSIONS

Under the present study's experimental conditions, the fiducial marker-based technique should be considered if four or more full-coverage highly radiopaque restorations are present.

Application of 3D-printed guide for locating screw access channels in cement-retained complete arch implant-supported zirconia restorations

Removal of cement-retained complete arch implant-supported zirconia restorations can be challenging. A predictable and minimally invasive technique combining cone beam computed tomography (CBCT) and intraoral scans with a virtual implant planning software program is described to identify the location of the screw access channels during the retrieval, thus minimizing damage to the existing restoration and allowing reuse.

A chairside digital radiographic guide for registering digital casts to cone beam computed tomography scans with strong metallic artifacts

Accurate registration of digital casts and cone beam computed tomography (CBCT) scans with strong metallic artifacts is essential for the accuracy of guided implant surgery. This article describes a procedure for mapping digital casts onto CBCT scans containing significant scatter artifacts in the virtual implant planning stage. The technique uses a chairside segmented occlusal wing-like radiographic guide, which is constructed of digital splints fabricated using a desktop 3-dimensional printer and composite resin spheres as markers to accurately superimpose the bimaxillary digital scans onto the CBCT scans in a single procedure. This cost-effective technique is timesaving for clinicians and patients, and the digital information for implant planning can be collected in a single visit.

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.

Radiopaque fiducial markers as an aid to fabrication of an implant surgical guide for a patient with orthodontic brackets: A dental technique

Designing implant surgical guides for patients undergoing orthodontics merely by merging data imaging and communications in medicine (DICOM) files generated from cone beam computed tomography (CBCT) images and standard tessellation language (STL) files generated from surface scanners is challenging because of the inaccuracy caused by metal artifacts. The present technique describes a straightforward and effective method of fabricating a surgical guide with the aid of fiducial markers made from cotton swabs and flowable resin. The implant surgical guide is designed by using a software program after the superimposition of digital scan and CBCT data. This chairside technique provides an accurate, convenient, and cost-effective option for the clinician.

Influence of zirconia crown artifacts on cone beam computed tomography scans and image superimposition of tomographic image and tooth surface scan: An in vitro study

STATEMENT OF PROBLEM

Zirconia restorations create significant artifacts on 3D cone beam computed tomography (CBCT) imaging. Static computer-assisted implant surgery (s-CAIS) relies on the accuracy of superimposition between an intraoral surface scan and CBCT imaging. However, how the artifacts from zirconia on the tomographic image might affect the predictability of s-CAIS is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of zirconia crown restorations on the superimposition process for s-CAIS.

MATERIAL AND METHODS

Four stone casts generated 4 groups: a control group (CG) with no crowns and 3 experimental groups with 4 (TG4), 7 (TG7), and 13 (TG13) zirconia crowns. A total of 40 CBCT scans were made for the 4 groups (n=10). All CBCTs were imported into a computer planning software program, and the casts from all 4 groups were scanned by using a high-resolution laboratory scanner. The standard tessellation language (STL) files were imported, segmented, and the 3 files superimposed for all groups. The accuracy of the superimposition was assessed, in millimeters, in 3 planes corresponding to anterior-posterior, horizontal, and vertical, as well as the overall measurement, and the results were analyzed statistically (α=.05).

RESULTS

The overall analysis demonstrated statistically significant differences between all groups (P<.001), except between CG and TG4. The anterior-posterior dimension demonstrated significant differences between CG and TG7 (P<.001), CG and TG13 (P<.001), TG4 and TG7 (P=.004), and TG4 and TG13 (P=.001). For the vertical dimension analysis, significant differences were found between CG and TG7 (P=.001), CG and TG13 (P<.001), and TG4 and TG13 (P<.001). For the horizontal variable, statistically significant differences were found between CG and TG7 (P=.049), CG and TG13 (P<.001), TG4 and TG13 (P<.001), and TG7 and TG13 (P=.003).

CONCLUSIONS

The accuracy of the superimposition of the images was influenced by the number of zirconia crowns, with an increased number reducing the superimposition accuracy.

Dental software classification and dento-facial interdisciplinary planning platform

OBJECTIVE

Despite all advantages provided by the digital workflow, its application in clinical practice is still more focused on device manufacturing and clinical execution than on treatment planning and communication. The most challenging phases of treatment, comprehensive planning, diagnosis, risk assessment, and decision-making, are still performed without significant assistance from digital technologies. This article proposes a new dental software classification based on the digital workflow timeline, considering the moment of patient's case acceptance as key in this classification, and presents the ideal software tools for each phase.

CLINICAL CONSIDERATIONS

The proposed classification will help clinicians and dental laboratories to choose the most appropriate software during the treatment planning phase and integrate virtual plans with other software platforms for digitally guided execution. A dento-facial interdisciplinary planning platform virtually simulates interdisciplinary clinical procedures and assists in the decision-making process.

CONCLUSIONS

The suggested classification assists professionals in different phases of the digital workflow and provides guidelines for improvement and development of digital technologies before treatment plan acceptance by the patient.

CLINICAL SIGNIFICANCE

Three-dimensional interdisciplinary simulations allow clinicians to visualize how each dental procedure influences further treatments. With this treatment planning approach, predictability of different procedures in restorative dentistry, orthodontics, implant dentistry, periodontal, and oral maxillofacial surgery is improved.

Effects of supporting conditions and anchor microscrew on the stabilization of the implant guide template during the drilling process: An in vitro study

STATEMENT OF PROBLEM

Implant placement errors have been reported in guided surgeries because of movement of the guide template during implant placement. With a completely limiting guide design with high restrictions, guide template stabilization is essential to minimize mobility during the drilling process.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of supporting conditions and the use of an anchor microscrew on the seating and functional stabilization of a computer-aided design and computer-aided manufacturing (CAD-CAM) implant surgical guide with a completely limiting design.

MATERIAL AND METHODS

Twelve implant surgical guide templates were fabricated under different supporting conditions: tooth-mucosa, tooth-tooth, tooth-screw, and screw-screw (n=3 per group). In the tooth-screw and screw-screw groups, anchor microscrews and anchor caps were used to fix the guide templates. The seating stability of the templates was evaluated by using a micromovement assessment. The functional stability of the templates was analyzed during the drilling process by using a motion tracking method. One-way analysis of variance and the Tukey HSD post hoc test were conducted to compare the differences among the groups (α=.05).

RESULTS

The tooth-tooth, tooth-screw, and screw-screw groups exhibited similar seating stability, which was significantly more stable than that of the tooth-mucosa group (P<.001). In terms of functional stability, the tooth-mucosa group reported the highest positional deviation and motion magnitude, whereas low values were found in the tooth-screw and screw-screw groups (P<.001).

CONCLUSIONS

The use of anchor microscrews can increase the seating and functional stability of CAD-CAM guide templates during the drilling process for implant placement.

Designing a complete-arch digital trial tooth arrangement for completely edentulous patients by using an open-source CAD software program: A dental technique

A method for creating a complete-arch digital trial tooth arrangement for completely edentulous patients is described. The technique demonstrates an effective way to reproduce the dental and gingival anatomies by using a free 3D modeling software program. This cost-effective, time-saving, and versatile method allows dental professionals to digitally plan challenging treatments for completely edentulous patients. The technique can also be used to fabricate diagnostic prostheses and implant-supported interim prostheses.

A technique for registering digital dental casts onto cone beam computed tomography scans with excessive metallic artifacts

This article describes a method of integrating digital dental casts into cone beam computed tomography (CBCT) scans in virtual implant planning in situations with an excessive number of metal artifacts. This technique requires the use of a prefabricated registration tray to provide a common landmark; is noninvasive, minimally time-consuming, and cost-effective; and requires only a single registration and minimal exposure to radiation.