Non-Radiological Method for Fabrication of a Screw-Channel Drilling Guide in Cement-Retained Implant Restorations Using Intraoral Digital Scanning and Imaging Superimposition: A Clinical Report

A three-dimensionally printed template for locating the screw channel in a cement-retained implant-supported crown: A digital workflow

Locating the screw channel in a cement-retained implant-supported crown is challenging. This article describes a fully digital workflow for fabricating a 3D printed template which can accurately guide the dentist to find the screw channel. A definitive implant cast from the patient and an implant planning software program are used in the workflow. This technique provides precise guidance for finding the location and angulation of the abutment screw access hole.

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.

Accuracy of digitally fabricated drilling guide to form screw-access channels in cement-retained implant prostheses: A randomized clinical trial

STATEMENT OF PROBLEM

Accurate intraoral preparation of screw channels in cement-retained implant prostheses could be a treatment challenge for tilted or badly positioned implants.

PURPOSE

The purpose of this randomized clinical trial was to evaluate screw channel accuracy for retrieving cement-retained implant prostheses by using a digitally fabricated drilling guide.

MATERIAL AND METHODS

Twenty-four participants requiring removal of cement-retained implant prostheses were recruited and consecutively assigned to 1 of 2 groups. In the first group, drilling guides were fabricated by using an intraoral scan, computer-aided design (CAD), and 3D printing to facilitate screw channel preparation (guide group). In the second group, screw channel preparation was based on panoramic radiographs without a drilling guide (freehand group). Screw channel accuracy was evaluated with a 3D analysis and subsequently compared with the ideal shape of the screw channel for linear deviation at coronal and apical levels, angular deviation, surface loss deviation, and volume loss deviation. The ideal shape of the screw-access channel was based on the Ø2.2-mm cylinder image marked along the long axis of the implant. The Mann-Whitney U and Kruskal-Wallis tests were used for statistical analyses (α=.05).

RESULTS

The drilling guide group showed higher dimensional accuracy than the freehand group for angular deviation (9.45 degrees versus 15.69 degrees; P=.014) and surface loss deviation (7.40 mm versus 9.53 mm; P=.001), especially when the implant was tilted more than 30 degrees. The deviation values of the screw channels were not significantly different according to implant tilt in either group (P>.05).

CONCLUSIONS

Digitally fabricated drilling guides for intraoral preparation of screw channels in cement-retained implant prostheses can improve accuracy and provide a less-destructive screw channel.

Techniques for locating the screw access hole in cement-retained implant-supported prostheses: A systematic review

STATEMENT OF PROBLEM

Different techniques for retrieving cement-retained implant-supported prostheses have been described to minimize damage to the prostheses. Nevertheless, a classification of the described techniques remains ambiguous.

PURPOSE

The purpose of this systematic review was to review and classify the described techniques for recording and locating the screw access hole in cement-retained implant-supported prostheses.

MATERIAL AND METHODS

A bibliographic search was completed on MEDLINE/PubMed, Web of Science, Scopus, and Cochrane databases. A manual search was also conducted. The articles that described or evaluated techniques for recording and locating the screw access hole of cement-retained implant-supported prostheses were included. Two investigators independently assessed the quality assessment of the studies using the Revised Cochrane risk of bias tool for randomized trials. A third examiner was consulted to resolve the lack of consensus.

RESULTS

A total of 30 articles were included. The different methods were classified according to whether the screw access hole location was registered before or after cementation. The precementation techniques were classified into 4 subgroups: identification marks, photographic records, digital files, and precementation screw access hole location guides. The postcementation techniques were subdivided into 2 subgroups: radiographic records and postcementation screw access hole location guides.

CONCLUSIONS

Different techniques have been proposed to facilitate the location of the screw access hole in cement-retained implant-supported restorations. Although the evidence is scarce, studies seem to ascertain that some techniques, such as the use of drilling guides, orientation with cone beam computed tomography images, or holes made in the metal framework, can increase the retrievability of cement-retained implant-supported prostheses and decrease complications in the location of the screw access hole. The proposed classification summarizes precementation and postcementation techniques and provides a tool to decide the most suitable for each specific clinical situation.

The Effects of Distribution of Image Matched Fiducial Markers on Accuracy of Computer-Guided Implant Surgery

PURPOSE

Image registration of the optical intraoral scan to computed tomography image is essential for computer-guided implant surgery. The remaining teeth, which are considered to be congruent structures observed in the scan and radiographic images, are used to perform the image registration. The purpose of this study was to evaluate the effects of the distribution of matching fiducial points on the accuracy of the image registration.

MATERIALS AND METHODS

A partially edentulous model with three anterior remaining teeth was prepared. Two mini dental implants were inserted in the posterior edentulous areas on both sides, and computed tomography and surface scan data were obtained. Three groups were set according to the distribution of the image matching points used: localized distribution, unilateral distribution, and bilateral distribution. Fifteen graduate students performed the registration process in each group using the same image matching method. The accuracy of image registration was evaluated by measuring the geometric discrepancies between the radiographic and registered scan images in the anterior, middle, and posterior regions. One-way and two-way analysis of variance with the Tukey HSD post hoc test were used for statistical analysis (α = 0.05) RESULTS: In general, the registration discrepancy was lowest in the bilateral distribution group, followed by the unilateral distribution and localized distribution groups (p< 0.001). In the regional analysis, the registration error tended to increase as the measurement region moved farther from the matching points. The distribution of the matching points and measurement regions had a statistical interaction in the accuracy of image registration.

CONCLUSION

The accuracy of image registration of the surface scan to the computed tomography is affected by the matching point distribution that can be improved by placing artificial markers in the edentulous areas.