Photogrammetric method to measure the discrepancy between clinical and software-designed positions of implants

Accuracy of intraoral photogrammetry versus direct digital implant impressions in the fully edentulous lower jaw: An in vitro study

OBJECTIVE

To evaluate and compare the accuracy of intraoral photogrammetry (IPG) and direct digital impressions in capturing the three-dimensional (3D) implant position in a fully edentulous mandible model with four multi-unit abutments (MUAs).

METHODS

An edentulous mandibular model with four implant analogs was scanned with a reference desktop scanner (INEOS X5®, Sirona) and four different intraoral scanners (IOSs; TRIOS 5®, 3SHAPE; i700®, MEDIT; Aoralscan 3® and Aoralscan Elite IPG®, SHINING 3D), the latter being equipped with an IPG system. In total, 120 scans (30 per IOS) were captured and saved in standard tessellation language (STL) format. The IOS scans were then compared with the reference desktop scan using a 3D analysis software (Inspect®, ZEISS) to evaluate accuracy through the distance standard deviation, integrated distance, and integrated absolute distance. Statistical analysis was performed using IBM SPSS Statistics v25® (IBM CORPORATION) and Kruskal-Wallis and Mann-Whitney tests.

RESULTS

The IOS equipped with IPG (Aoralscan Elite IPG®) demonstrated the highest accuracy in all measured parameters. It showed a statistically significantly lower (p < 0.01) distance standard deviation, integrated distance, and integrated absolute distance compared to the direct impressions taken with the other three IOSs (TRIOS 5®, i700®, and Aoralscan 3®). Among the direct digital implant impressions without IPG, TRIOS 5® exhibited the best performance, while i700® and Aoralscan 3® showed higher deviations.

CONCLUSIONS

Based on the preliminary results of this in vitro study, IPG demonstrated the highest accuracy in all measured parameters compared to direct digital implant impressions with IOSs; however, clinical studies are needed to confirm these results.

STATEMENT OF CLINICAL RELEVANCE

IPG might represent an accurate and reliable method for obtaining implant impressions in full-arch cases, offering significant advantages for clinicians in the field of implant prosthodontics.

Accuracy of digital implant impressions using a novel structured light scanning system assisted by a planar mirror in the edentulous maxilla: An in vitro study

OBJECTIVES

This study aimed to develop a structured light scanning system with a planar mirror to enhance the digital full-arch implant impression accuracy and to compare it with photogrammetry and intraoral scanner methods.

MATERIALS AND METHODS

An edentulous maxillary stone cast with six scan bodies was scanned as the reference model using a laboratory scanner. Three scanning modalities were compared (n = 10): (1) self-developed structured light scanning with a mirror (SSLS); (2) intraoral scanner (IOS); and (3) photogrammetry system (PG). The scanners were stopped for 1 min after each scan. Six scan bodies were analysed within each scan model. Linear deviations between the scan bodies (1-2, 1-3, 1-4, 1-5, and 1-6) and 3D mucosal deviations were established. The overall deviation was calculated as the mean of all linear deviations. "Trueness" represented the discrepancy between the test and reference files, while "precision" denoted the consistency among the test files. Kruskal-Wallis and Mann-Whitney U tests were used for statistical analyses.

RESULTS

Significant overall linear discrepancies were noted among the SSLS, PG, and IOS groups (p < .001). SSLS showed the best overall trueness and precision (6.6, 5.7 μm), followed by PG (58.4, 6.8 μm) and IOS (214.6, 329.1 μm). For the 3D mucosal deviation, the trueness (p < .001) and precision (p < .001) of the SSLS group were significantly better than those of the IOS group.

CONCLUSIONS

The SSLS exhibited higher accuracy in determining the implant positions than the PG and IOS. Additionally, it demonstrated better accuracy in capturing the mucosa than IOS.

Accuracy of edentulous full-arch implant impression: An in vitro comparison between conventional impression, intraoral scan with and without splinting, and photogrammetry

OBJECTIVES

The purpose of this in vitro study was to compare the trueness and precision of complete arch implant impressions using conventional impression, intraoral scanning with and without splinting, and stereophotogrammetry.

MATERIALS AND METHODS

An edentulous model with six implants was used in this study. Four implant impression techniques were compared: the conventional impression (CI), intraoral scanning (IOS) without splinting, intraoral scanning with splinting (MIOS), and stereophotogrammetry (SPG). An industrial blue light scanner was used to generate the baseline scan from the model. The CI was captured with a laboratory scanner. The reference best-fit method was then applied in the computer-aided design (CAD) software to compute the three-dimensional, angular, and linear discrepancies among the four impression techniques. The root mean square (RMS) 3D discrepancies in trueness and precision between the four impression groups were analyzed with a Kruskal-Wallis test. Trueness and precision between single analogs were assessed using generalized estimating equations.

RESULTS

Significant differences in the overall trueness (p = .017) and precision (p < .001) were observed across four impression groups. The SPG group exhibited significantly smaller RMS 3D deviations than the CI, IOS, and MIOS groups (p < .05), with no significant difference detected among the latter three groups (p > .05).

CONCLUSIONS

Stereophotogrammetry showed superior trueness and precision, meeting misfit thresholds for implant-supported complete arch prostheses. Intraoral scanning, while accurate like conventional impressions, exhibited cross-arch angular and linear deviations. Adding a splint to the scan body did not improve intraoral scanning accuracy.

A comparative evaluation of photogrammetry software programs and conventional impression techniques for the fabrication of nasal maxillofacial prostheses

STATEMENT OF PROBLEM

The fabrication of facial prostheses is complicated and time-consuming because of the need for accurate impressions of the facial defects and surrounding tissues. Inaccuracies can arise from soft-tissue compression, involuntary patient movements, and insufficient support for the impression material. Various 3-dimensional (3D) imaging and scanning techniques, including photogrammetry, have been introduced, but their accuracy remains insufficiently evaluated.

PURPOSE

The purpose of this in vitro study was to evaluate and compare the accuracy of 3D digital casts generated by 4 photogrammetry software programs (Agisoft Metashape, 3DF Zephyr, Meshroom, and Polycam) and casts from 2 conventional impression materials (alginate and polyvinyl siloxane [PVS]) for the fabrication of nasal maxillofacial prostheses.

MATERIAL AND METHODS

A stone cast of a patient's nose was used as the basis for generating a reference digital 3D cast and another 54 test 3D casts. The reference cast was created by scanning the stone cast using a FARO Optor Lab 3D scanner. The 54 test 3D casts were generated and divided into 6 test groups as follows: Agisoft group: 9 3D casts generated using Agisoft Metashape, a commercial personal computer (PC) software program; 3DF Zephyr group: 9 3D casts generated using 3DF Zephyr, a commercial PC software program; Meshroom group: 9 3D casts generated using Meshroom, a free PC software program; Polycam group: 9 3D casts generated using the Polycam, a commercial Android cloud application; PVS group: 9 3D casts generated indirectly by 3D scanning a gypsum cast made from a polyvinyl siloxane (PVS) impression of the stone nose cast; and Alginate group: 9 3D casts generated indirectly by scanning a master cast made using alginate impressions of the stone nose cast. Deviation measurements of the produced specimens were analyzed using the Geomagic Control X software program, and statistical comparisons were performed employing the Kruskal-Wallis test (α=.05).

RESULTS

The results showed that the 3DF Zephyr group had the smallest deviation measurements (median: 0.057 mm ±0.012) among the 4 photogrammetry software programs, while the alginate impression group had the largest deviations (median: 0.151 mm ±0.094) of the 2 conventional impression materials. Significant differences were observed among the 4 photogrammetry software programs and the 2 conventional impression materials (H=39.41, df=5, P<.001). The casts generated by Agisoft Metashape were significantly more accurate than those produced by Meshroom, Polycam or the conventional impression materials (P=.024, P=.045, P<.001, respectively). The casts produced by 3DF Zephyr were significantly more precise than those created by Meshroom and the conventional impression materials (P=.037, P<.001, respectively). No significant differences were observed between the Agisoft Metashape and 3DF Zephyr groups (P>.05).

CONCLUSIONS

Photogrammetry software programs, specifically Agisoft Metashape and 3DF Zephyr, demonstrated better accuracy than conventional impression materials in creating nasal digital casts. Photogrammetry has the potential to improve workflow and reduce patient discomfort during the fabrication of maxillofacial prostheses. Further research is needed to validate these findings in clinical settings.

Photogrammetry technology in implant dentistry: A systematic review

STATEMENT OF PROBLEM

Photogrammetry technology may be useful in implant dentistry, but a systematic review is lacking and is indicated before routine use in clinical practice.

PURPOSE

The purpose of this systematic review was to assess the role of the photogrammetry technology used in implant dentistry and determine its validity as an accurate tool with clinical applications.

MATERIAL AND METHODS

Four major databases, PubMed MEDLINE, Google Scholar, Scopus, and Web of Science, were selected to retrieve articles published from January 2011 to February 2021 based on custom criteria. The search was augmented by a manual search. After screening of the collected articles, data, including study design and setting, type of application, digitizer used, reference body, method of evaluation, and overall outcomes, were extracted.

RESULTS

Twenty articles were included based on the selection criteria. Most of the articles confirmed that the use of photogrammetry was promising as an implant coordinate transfer system. However, few articles showed its use for 3-dimensional scanning, which might require more development.

CONCLUSIONS

The initial reports of using photogrammetry technology considered this method as a valid and reliable clinical tool in implant dentistry. More studies to develop the photogrammetry technology and to assess the results with evidence-based research are recommended to enhance its application in different clinical situations.

Guided Zygomatic Implantology for Oral Cancer Rehabilitation: A Case Report

Oral rehabilitation after maxillary oncological resection is challenging. This case report presents the rehabilitation of a 65-year-old Caucasian male adenoid cystic carcinoma patient using a myo-cutaneous thigh flap, zygomatic implant placement, and an immediate fixed provisional prosthesis made with computer-aided technologies. The patient presented complaints of asymptomatic enlarged swelling of 5-mm on the right hard hemi-palate. There was an oro-antral communication deriving from a previous local excision. Preoperative radiographs showed the involvement of the right maxilla, maxillary sinus, and nose with a suspect involvement of the maxillary division of the trigeminal nerve. Treatment was planned through a fully digital workflow. A partial maxillectomy was performed endoscopically, and maxilla was reconstructed using an anterolateral thigh free flap. Two zygomatic implants were inserted simultaneously. A provisional fix full-arch prosthesis was manufactured preoperatively through a fully digital workflow and was placed in the operating room. Following post-operative radiotherapy, the patient received a final hybrid prosthesis. During the follow-up period of two years, the patient reported good function, aesthetics, and significant enhancement in quality of life. According to the results of this case, the protocol represented can be a promising alternative for oral cancer patients with large defects, and can lead to an improved quality of life.

Trueness and precision of complete-arch photogrammetry implant scanning assessed with a coordinate-measuring machine

STATEMENT OF PROBLEM

Photogrammetry technology has been used for the digitalization of multiple dental implants, but its trueness and precision remain uncertain.

PURPOSE

The purpose of this in vitro investigation was to compare the accuracy (trueness and precision) of multisite implant recordings between the conventional method and a photogrammetry dental system.

MATERIAL AND METHODS

A definitive cast of an edentulous maxilla with 6 implant abutment replicas was tested. Two different recording methods were compared, the conventional technique and a photogrammetry digital scan (n=10). For the conventional group, the impression copings were splinted to an additively manufactured cobalt-chromium metal with autopolymerizing acrylic resin, followed by recording the maxillary edentulous arch with an elastomeric impression using an additively manufactured open custom tray. For the photogrammetry group, a scan body was placed on each implant abutment replica, followed by the photogrammetry digital scan. A coordinate-measuring machine was selected to assess the linear, angular, and 3-dimensional discrepancies between the implant abutment replica positions of the reference cast and the specimens by using a computer-aided design program. The Shapiro-Wilk test showed that the data were not normally distributed. The Mann-Whitney U test was used to analyze the data (α=.05).

RESULTS

The conventional group obtained an overall accuracy (trueness ±precision) value of 18.40 ±6.81 μm, whereas the photogrammetry group showed an overall scanning accuracy value of 20.15 ±25.41 μm. Significant differences on the discrepancies on the x axis (U=1380.00, P=.027), z axis (U=601.00, P<.001), XZ angle (U=869.00, P<.001), and YZ angle (U=788.00, P<.001) were observed when the measurements of the 2 groups were compared. Furthermore, significant 3-dimensional discrepancy for implant 1 (U=0.00, P<.001), implant 2 (U=0.00, P<.001), implant 3 (U=6.00, P<.001), and implant 6 (U=9.00, P<.001) were computed between the groups.

CONCLUSIONS

The conventional method obtained statistically significant higher overall accuracy values compared with the photogrammetry system tested, with a trueness difference of 1.8 μm and a precision difference of 18.6 μm between the systems. The conventional method transferred the implant abutment positions with a uniform 3-dimensional discrepancy, but the photogrammetry system obtained an uneven overall discrepancy among the implant abutment positions.

Accuracy of DICOM-DICOM vs. DICOM-STL Protocols in Computer-Guided Surgery: A Human Clinical Study

Guided implant surgery can enhance implant placement positioning, increasing predictability and decreasing postoperative complications., To date, the best protocol to be used for template realization is still unknown. Thus, the aim herein was to clinically compare the accuracy of two different protocols. A total of 48 implants were divided into Group A (24 implants), in which a stereolithographic template was realized using the digital imaging and communications in medicine (DICOM) data arrived from cone beam computer tomographies (CBCTs) (patients and prothesis alone), and Group B (24 implant), in which a standard intraoral stent with a standardized extraoral support was used for patients’ intraoral impressions and CBCT. The preimplant virtual planning and postsurgery CBCT images of both groups were superimposed, and differences were registered in terms of average deviations at the platform (a) and implant apex (b), mean depth change (c), and angular deviation (d). The results demonstrated that there were no statistically significant differences between groups (p = 0.76) for the parameters measured. However, statistically significant differences (p < 0.05) were found between maxillary and mandible implant surgery, as the latter showed greater accuracy. Additional studies are necessary to further reduce discrepancies between planning and surgical procedures.

Comparative study of the accuracy of an implant intraoral scanner and that of a conventional intraoral scanner for complete-arch fixed dental prostheses

STATEMENT OF PROBLEM

Most of the available digital systems are designed to image teeth and soft tissue rather than dental implants. However, although some are marketed specifically to record implant position, whether these products are better for implant scanning is unclear.

PURPOSE

The purpose of this in vitro study was to compare the accuracy of an implant intraoral scanner (PiC camera) with that of an intraoral scanner (TRIOS3) for 6 implants placed in completely edentulous arches.

MATERIAL AND METHODS

Two maxillary master models with 6 external hexagonal Ø5.1-mm implants were used, one with parallel and the other with angled implants. The reference values were obtained with a coordinate measuring machine. Ten scans were made per model (parallel and angled) and system (intraoral and implant) (n=10), after which the 3-dimensional coordinates for each implant were determined with a computer-aided design software program and compared with the linear and angular reference values. Statistical significance was determined with the Student t test (α=.05).

RESULTS

Statistically significant differences (P<.001) were found in both precision and trueness. The overall errors relative to the reference in the parallel implant-supported casts based on the implant scanner were 20 μm (P=.031) and 0.354 degrees (P=.087) compared with 100 μm (P<.001) and 1.177 degrees (P<.001) in the cast based on conventional digital scans. The global errors in the angled implant casts were 10 μm (P=.055) and 0.084 degrees (P=.045) for the implant digital scans and 23 μm (P=.179) and 0.529 degrees (P<.001) for the conventional digital scans.

CONCLUSIONS

The implant intraoral scanner delivered greater precision and trueness than the conventional instrument for imaging complete-arch implant-supported prostheses.

Photogrammetry as an alternative for acquiring digital dental models: A proof of concept

Photogrammetry is a mathematical technique that generates three-dimensional coordinates of specific points identified from multiple images of the same object obtained at different angles. This technique may be a low-cost alternative for traditional scanning. The objective of this proof of concept was to evaluate the accuracy and precision in obtaining digital models (DM) from a plaster model (PM) using photogrammetry. Five DM were generated from 50 photographs taken surrounding the PM. The photographs were taken by a single operator on five consecutive days using natural light. The images obtained were processed on 3DF Zephyr Free software. The height and width of all teeth were recorded on both PM and DM, as well as the distance between the canine cusps (C-C) and between the mesiobuccal cusps of the first molars (1 M-1 M). For the PM the measurements were taken with a digital caliper, whereas the DM was measured using the software Blender. The DM and PM measurements presented a limit of agreement between -0.433 and 0.611 mm. The accuracy of DM measurements showed a SD of ±0.171 mm and a repeatability coefficient of 0.474. In the superimposition of all DM, it was possible to notice a greater discrepancy in the posterior region of the arch and palate, but this difference decreased when the region was segmented. It can be concluded that photogrammetry appears to be a viable technique for the digitization of dental models. Further studies need to be performed to evaluate its clinical application.

A combined digital and stereophotogrammetric technique for rehabilitation with immediate loading of complete-arch, implant-supported prostheses: A randomized controlled pilot clinical trial

STATEMENT OF PROBLEM

Traditional impressions for complete-arch restorations are complex and time-consuming, and they can be uncomfortable for the patient. New digital techniques such as stereophotogrammetry may mitigate this.

PURPOSE

The purpose of this randomized controlled pilot clinical trial was to compare the patient and dentist satisfaction and work times of traditional impressions (control group) and digital impressions with stereophotogrammetry in complete-arch, implant-supported prostheses. Success rates, implant survival, marginal bone loss around the dental implants, and prosthesis survival were also analyzed.

MATERIAL AND METHODS

This randomized controlled pilot clinical trial included 18 participants who received 131 dental implants. Implant impressions in the experimental group were made with stereophotogrammetry (8 participants with 66 implants), while traditional impressions were made in the control group (10 participants with 65 implants). Working times were measured in minutes starting from removal of the healing abutments to their replacement after the impression. Patient and dentist satisfaction was analyzed using a questionnaire with a visual analog scale, and implant success was assessed using the Buser success criteria. Prosthesis survival was defined as the presence of the prosthesis in the mouth, without screw loosening or fracture.

RESULTS

The work times were 15.6 (experimental group) and 20.5 minutes (control group) (P<.001). The patient satisfaction scores were 8.8 in the experimental and 7.9 in the control group (P=.02). The dentist satisfaction scores were 9.1 in the experimental group and 8.5 in the control group (P=.03). The implant success rate was 100% in both groups. Marginal bone loss was 0.6 ±0.5 mm (experimental group) and 0.6 ±0.2 mm (control group) (P=.72).

CONCLUSIONS

Digital impressions using stereophotogrammetry may be an alternative to traditional impressions. Patient and dentist satisfaction improved, and the work time was reduced in the experimental group. No statistically significant differences were found in terms of the implant success rate, implant survival, marginal bone loss, or prosthesis survival between the 2 groups.

Evaluation of marginal and internal adaptation of hybrid and nanoceramic systems with microcomputed tomography: An in vitro study

STATEMENT OF PROBLEM

The accuracy of recently introduced chairside computer-aided design and computer-aided manufacturing (CAD-CAM) blocks is not well established, and marginal integrity and internal adaptation are not known.

PURPOSE

The purpose of this in vitro study was to evaluate the marginal and internal adaptation of hybrid and nanoceramics using microcomputed tomography (μ-CT).

MATERIAL AND METHODS

The marginal and internal adaptation of 3 polymer-infiltrated ceramic-network (PICN) materials (Vita Enamic [VE]; Lava Ultimate [LU]; Vita Suprinity [VS]) were compared with lithium disilicate (IPS e.max.CAD, IPS). Ninety-six specimens (48 dies and 48 crowns) were prepared (n=12 each group) using a chairside CAD-CAM system. The restorations were scanned with μ-CT, with 160 measurements made for each crown, and used in 2-dimensional (2D) analysis. The marginal adaptation of marginal discrepancy (MD), absolute marginal discrepancy (AMD), internal adaptation of shoulder area (SA), axial space (AS), and occlusal space (OS) were compared using appropriate statistical analysis methods (α=.05). Cement volumes were compared using 3D analysis.

RESULTS

The IPS blocks showed higher MD (130 μm), AMD (156 μm), SA (111 μm) (P<.05), AS (52 μm), and OS (192 μm) than the other blocks (P<.01). The adaptation values of VS were significantly lower than those of the IPS block (P<.05). The adaption values of the LU and VE blocks were significantly lower than those of others (P<.01) but were statistically similar to one another (P>.05). IPS had the largest cement space at 18 mm³ (P<.01).

CONCLUSIONS

The marginal and internal adaptation values were within a clinically acceptable range for all 3 hybrids and nanoceramics tested.