In Vivo and In Vitro Accuracy Analysis of Static Computer-Assisted Implant Surgery in an Edentulous Patient

Round 1

Reviewer 1 Report

Dear Authors, 

thank you for the chance to review your manuscript. I found it very interesting because of the aim of the study. 

However, some minor points needs to be highlight and revised.

In the introduction, please describe the different static templates that can be used to perform sCAIS and report the deviations.

"Several studies have provided information on accuracy of s-CAIS, but a lack of homogeneity was found for accuracy assessment techniques and protocols [5]."  this is a strong sentence, please add more recent references the can support this statement.

Please insert in the first part of the discussion section the aim and the limitations of this study.

Moreover, it could be interesting to compare dynamic navigation systems to sCAIS in terms of accuracy and clinical reliability for complete arches restorations.

 

Here you can find some papers that can be inserted in the introduction and in the discussion section:

Carosi P, Lorenzi C, Lio F, Cardelli P, Pinto A, Laureti A, Pozzi A. Accuracy of Computer-Assisted Flapless Implant Placement by Means of Mucosa-Supported Templates in Complete-Arch Restorations: A Systematic Review. Materials (Basel). 2022 Feb 16;15(4):1462. doi: 10.3390/ma15041462

Tallarico M, Xhanari E, Kim YJ, Cocchi F, Martinolli M, Alushi A, Baldoni EE, Meloni SM. Accuracy of computer-assisted template-based implant placement using conventional impression and scan model or intraoral digital impression: A randomised controlled trial with 1 year of follow-up. Int J Oral Implantol (Berl). 2019;12(2):197-206.

Romandini M, Ruales-Carrera E, Sadilina S, Hämmerle CHF, Sanz M. Minimal invasiveness at dental implant placement: A systematic review with meta-analyses on flapless fully guided surgery. Periodontol 2000. 2022 Jul 30. doi: 10.1111/prd.12440.

Pozzi A, Arcuri L, Carosi P, Nardi A, Kan J. Clinical and radiological outcomes of novel digital workflow and dynamic navigation for single-implant immediate loading in aesthetic zone: 1-year prospective case series. Clin Oral Implants Res. 2021 Dec;32(12):1397-1410. doi: 10.1111/clr.13839.

Carosi P, Ferrigno N, Arcuri C, Laureti M. Computer-Aided Surgery and Immediate Loading to Rehabilitate Complete Arch with Four Dental Implants and Fixed Screw-Retained Prosthesis Up to 4 Years in Function: A Retrospective Study. Int J Oral Maxillofac Implants. 2021 Nov-Dec;36(6):1180-1187. doi: 10.11607/jomi.8946

Pozzi A, Hansson L, Carosi P, Arcuri L. Dynamic navigation guided surgery and prosthetics for immediate loading of complete-arch restoration. J Esthet Restor Dent. 2021 Jan;33(1):224-236. doi: 10.1111/jerd.12710.

 

Author Response

Dear reviewer, thank you for your time dedicated to our manuscript. Your valuable comments helped to improve it significantly

- In the introduction, please describe the different static templates that can be used to perform sCAIS and report the deviations.

According to Bornstein et al. [10] and Tahmaseb et al. [11] mucosa-, tooth-, and mini-implant–supported templates demonstrate accuracy of implant placement superior to that of bone-supported guides. Carosi et al. state that computer-assisted flapless implant placement by means of mucosa-supported templates in complete-arch restorations can be considered a reliable and predictable treatment choice, despite the potential effects that a flapless approach could bring to the overall treatment [12]. Flapless and fully guided implant placement has the potential to maximize efficacy outcomes and at the same time to minimize surgical invasiveness [13]. The use of computer-guided surgery to rehabilitate edentulous arches by means of four dental implants supporting a fixed screw-retained prosthesis could be a valid treatment option in the short and medium term [16]   -"Several studies have provided information on accuracy of s-CAIS, but a lack of homogeneity was found for accuracy assessment techniques and protocols [5]."  this is a strong sentence, please add more recent references the can support this statement.   Tahmaseb et al. in the systematic review state that several studies have provided information on accuracy of s-CAIS, but a lack of homogeneity was found for accuracy assessment techniques and protocols: many different surgical factors and techniques were not standardized between the studies, which served to confound the true accuracy of guided surgery; there were many steps within the digital workflow itself, where there was a possibility of accumulating error, which also served to mask the real accuracy of the technique [5].Most studies compare CBCT data before and after implant placement   -Please insert in the first part of the discussion section the aim and the limitations of this study.

The aim of this study was to evaluate the accuracy of s-CAIS in an edentulous patient both in vivo and in vitro with two different evaluation techniques and investigate if both can be applied in edentulous patients.

Deviations between the planned and achieved implant positions should be expected because of inaccuracies in the various procedures during template design and manufacturing [31,32]. At the same time, the use of such individualized template allows appropriate bone reduction for obtaining a predictable surgery and prosthetic stage [33].

The limitations of the study are related to the fact that during implant placement, several clinical factors might affect the accuracy of final treatment and some of them (different bone density guiding the osteotomy, different possible fit of a bone-supported template, stability, and fixation of the template) are missing in the in vitro part of the experiment. In this clinical report, treatment evaluation was affected by the procedure of matching DICOM to DICOM as well as to the possible errors during CBCT acquisition. On the contrary, in the in vitro part of the study, dental implants seem to be placed more similarly to the initial planning if compared to the in vivo part.

However, several inaccuracies might occur also in the in vitro analysis due to several factors related to data acquisition and the following 3D printing of the model. According to Zhou et al. [32], different types of errors might arise during image acquisition and data processing. There is a correlation between the dataset volume extracted from the CBCT and a CBCT resolution reported by Schnutenhaus [34]. Evaluating the results, the explanation is that CBCTs were created with a resolution of 0.2 voxels and, therefore, a matching precision greater than 0.2 mm is not achievable. This error might have been doubled when printing the exported DICOM dataset of the mandible. Hence, volume shrinkage could be noticed at the matching stage. According to Shujaat et al. [35], there is some inaccuracy also due to 3D printing procedures: the 3D-printer used in the present study has at 35 µm precision, according to the manufacturer. Several parameters must be considered before choosing a 3D printing, such as the processing software, the type of 3D printer, mechanical characteristics, as well as properties of the printing material [36]. In fact, several factors were controlled as best as possible by standardizing treatment planning and production parameters for the accuracy of the 3D printing having a minor possible effect on the results.

The other issue to consider is bone density, which appeared to be denser than the real bone and this was related to the use of radiopaque resin. In fact, the adequate bone density was achieved by utilizing a mixture of a radiopaque and transparent polymers. Also, when performing a CBCT scan to the printed model, a higher blooming effect was noticed around implants, if compared to implants placed in the patient, which could also affect the implant matching procedure. As of today, no clinical evidence exists related to the optimal CBCT scanning settings for reducing the influence of metal artifacts [37].

IOS procedures today are widely integrated with s-CAIS. Implant rehabilitations planned utilizing intraoral digital impressions showed similar results compared to conventional impression and model scan. Digital impression may be a viable option for the rehabilitation of partial edentulous patients when computer-guided template-assisted implant placement is used [38]. Applying IOS in edentulous patients up to today is still limited. Wismeijer et al. [39] stated that the accuracy of digital impressions is negatively influenced by an increase in the inter-implant distance in edentulous situations. When considering the accuracy of full-arch impressions for long-span prostheses, conventional impression methods remain the gold standard as the IOS error rises with the increase in the edentulous scanning area [40]. Further research needs to be conducted to improve the precision and trueness of IOS for full arch scanning [27]. For this reason, IOS was not used in the clinical part of the study and cannot be recommended yet for clinical use in edentulous. Furthermore, Komuro et al. [24] recommended the use of laboratory scanners as they  provide more precise data as compared to IOS

-Moreover, it could be interesting to compare dynamic navigation systems to sCAIS in terms of accuracy and clinical reliability for complete arches restorations

For future research it would be beneficial to access the data on dynamic navigation in edentulous patients. Dynamic systems in the Jung et al. [44] systematic review provided greater accuracy than the static systems; this difference might be explained by the fact that static template-based systems were more often used clinically rather than in preclinical models, which have provided better accuracy. According to Wei et al. [45] accuracy of dynamic computer-aided implant surgery reaches a clinically acceptable range and has potential in clinical usage, but more patient-centered outcomes and socio-economic benefits should be reported. As for today, the scientific data on dynamic navigation in literature is scarce. There are few studies reporting on dynamic navigation and its application in edentulous patients [46]. Future research should be oriented on utilizing of dynamic navigation surgery in edentulous and reporting data on its accuracy.

-Here you can find some papers that can be inserted in the introduction and in the discussion section

All articles were thoroughly studied, valuable information was included in introduction and discussion 

Thank you and best regards

 

Reviewer 2 Report

This is a review for a technical note that compared CBCT and intra oral scanning accuracy for a single patient receiving 4 implants. It is generally well written and I recommend publication after the following edits.

 

 

 

More information the CBCT and how it was processed is needed in the methods. This is also true for the IOS.

 

Table 1 needs unites and more explanation for the base vs. tip.

 

Does the accuracy of the 3D printing affecting the results in anyway?

 

Could the authors be more explicit about the benefits of comparing the scans themselves and then using the scans to print a 3D model and comparing that?

 

There are a few typos but they’re minor.

 

Author Response

Dear reviewer, thank you for your time dedicated to our manuscript. Your valuable comments helped to improve it significantly.

-More information the CBCT and how it was processed is needed in the methods. This is also true for the IOS.

Radiopaque 3D markers were attached to the existing prosthesis to serve also as radiographic template prior to CBCT acquisition. The denture was further relined with soft material (GC Soft Liner) before the acquisition of the CBCT scan, thus avoiding possible prosthesis movement and for precise transition of actual soft tissue of the patient in the planning software. The first CBCT was performed at the patient with Green 16 (Vatech, Fort Lee, New Jersey, USA) in standard conditions (94 kVp, 8.0 mA, 360° rotation, 9 s, FOV: 100 x 85, voxel size: 200 μm) with the mouth closed, as separating the arches could cause radiological template movement. A protocol described by Storelli et al. [26] was implemented: after CBCT acquisition, STL file of the denture was obtained using the laboratory scanner (Straumann 7 series lab scanner, Institut Straumann AG). Data obtained in Digital Imaging and Communications in Medicine (DICOM) format were, then, imported in a surgical planning software (coDiagnostiX, Dental Wings). All the acquisition parameters that could influence the accuracy of later steps for generating a virtual model such as segmentation as described by Shujaat et al. [27] were assessed. Data in Standard Tessellation Language (STL) format were imported in the software to prosthetically orient implant positions. CBCT data of the patients in DICOM (Digital imaging and communications in medicine) format, STL files of radiographic template of edentulous patient were matched in a surgical planning software.

For the in vivo evaluation DICOM to DICOM matching protocol of the accuracy assessment technique was applied, which consists of matching of dataset with planning, with dataset of the results of the surgery. The patient received a second CBCT scan after implant placement and delivery of the final prosthesis to perform accuracy analysis (Figure 1d). The same CBCT device was used to obtain more qualitative data as the registration accuracy in implant planning software is significantly influenced by the preprocessing of imported data [30]. The area of interest (mandible) was segmented from CBCT scan, which allowed more qualitative matching. Data in DICOM format were inserted in the Treatment evaluation tool of coDiagnostiX, matching the pre-op and post-op CBCT scans was performed (Figure 2a).

The limitation of DICOM to DICOM protocol might be the discrepancy between the CBCT scans. To minimize its influence, the same CBCT device was used, and matching was performed in multiple areas in clearly visible anatomical structures following the recommended protocol of Treatment Evaluation Tool. Each implant was aligned in the pre-op and post-op CBCT, and accuracy values were automatically generated by the software (Figure 2b).

-Table 1 needs unites and more explanation for the base vs. tip.

The 3D, distal, vestibular and apical deviations were recorded on a coronal (base) and apical (tip) points of the implants, as well as angular deviations.

-Does the accuracy of the 3D printing affecting the results in anyway?

The STL file exported from the segmentation and STL file of printed and scanned mandible with implants and scan body inserted, were imported into Geomagic Studio 2013 (3D Systems, USA) (an open-source software for processing, editing and comparing 3D triangular meshes) and aligned using the fine alignment algorithm. As described by Nulty [41], these kind of software allows the generation of a colorimetric map of the deviation across the surface of the STL mesh as compared to the master STL, quantified at specific points. The colour map indicates deviation inward (blue) or outward (red), while green indicates minimal deviation. The same colour deviation scale was utilized to illustrate the minimum and maximum deviations for each comparison. The colour scale ranged from a maximum and minimum deviation of +200 (outward/red) and −200 μm (inward/blue). In the present study, the overall trueness was 27 μm. Thus, the accuracy of the 3D printing did not seem to significantly affect the results.

-Could the authors be more explicit about the benefits of comparing the scans themselves and then using the scans to print a 3D model and comparing that

As the aim of the present study was to evaluate the accuracy of s-CAIS in an edentulous patient both in vivo and in vitro, the clinical situation was to be duplicated, so the bone-supported template design was chosen. Bornstein et al. [10] recommended the use of digital impressions to evaluate the accuracy of computer-assisted implant placement. Skjerven et al. [42] in a study comparing two treatment evaluation methods available using the same surgical planning software, stated that accuracy measurements performed via IOS provided comparable results to those obtained by CBCT. However, in the above-mentioned study, tooth-supported templates were used, which are more precise than mucosa- or bone–supported templates in edentulous patients [43] and IOS in partially edentulous patients in this study could be performed. However, to the best of the authors’ knowledge, there are no studies in literature reporting data on comparing IOS to DICOM and DICOM to DICOM treatment evaluation methods in edentulous patients. Further research needs to be conducted to improve the precision and trueness of IOS for full arch scanning [27]. For this reason, IOS was not used in the clinical part of the study and cannot be recommended yet for clinical use in edentulous. Furthermore, Komuro et al. [24] recommended the use of laboratory scanners as they  provide more precise data as compared to IOS.    Thank you again and best regards!

 

Reviewer 3 Report

The theme of the paper is original and interesting.

The authors presented the aims of their research.

Material and method are clearly presented.

The paper addressed the proposed subject.

The conclusions are clearly presented and argued.

For the reasons given above, I consider that the manuscript deserves to be published.

 

Author Response

Dear reviewer, thank your for your time dedicated to our work, and positive feedback!