Accuracy of a computerized tomography-guided template-assisted implant placement system: an in vitro study

Objectives: To evaluate the accuracy of computer-assisted 3D planning and implant insertion using computerized tomography (CT).
Materials and methods: Nine implants were planned on pre-operative CTs of six resin models, which were acquired with radiographic templates, using a planning software (E implants). Each resin model contained three pre-existing control implants (C implants). Radiographic templates were converted into operative guides containing 4.8-mm-diameter titanium sleeves. A single set of insertable sleeves was used for consecutively drilling the six models, followed by implant insertion through the guide sleeves. Models were further divided into group A (the first three models) and group B (the last three models). Post-operative CTs were used to compare implant positions with pre-operative planned positions. Statistical analysis included the Mann–Whitney U test for E and C implants and the Wilcoxon's signed ranks test for groups A and B.
Results: The mean apex depth deviations for E and C implants [0.49 mm±0.36 standard deviation (SD) and 0.32 mm±0.21 SD, respectively], and the mean apex radial deviations (0.63 mm±0.38 SD and 0.49 mm±0.17 SD, respectively) were similar ( P >0.05). The mean angulation deviations for E and C implants were 2.17±1.06°SD and 1.33±0.69°SD, P <0.05. E implant deviations of all the parameters in group A were significantly smaller than E implant deviations in group B.
Conclusions: Computer-assisted implant planning and insertion provides good accuracy. Deviations are mainly related to system and reproducibility errors. Multiple use of drills and titanium sleeves significantly reduces system accuracy.     

Precision of transfer of preoperative planning for oral implants based on cone-beam CT-scan images through a robotic drilling machine

In this study, an image-guided system for oral implant placement was assessed. A specially designed mechanical tool has been elaborated to transfer the preoperative implant axis planned on 3-dimensional imagery into a surgical template by a numerically controlled drilling machine. The main drawback of image-guiding systems is the use of preoperative computed tomography, which is expensive and delivers high radiation doses. Therefore, in this study the image-guiding system was coupled with a cone-beam tomograph that significantly decreased both cost and radiation doses. Three edentulous models were used. To determine the accuracy of the system, the ability of a 1.8-mm diameter drill to enter a 2.0-mm diameter, 10-mm-long titanium tube inserted on the model with no contact was verified. Because the drill entered the tubes with no contact and went beyond the end of the tube, the transfer error was less than 0.2 mm for translation and less than 1.1 degrees for rotation. The method presented here is low cost and high precision compared to other technological solutions such as tracking. Further assessment in the surgical field should lead to daily use of this system for flapless surgery, to prepare a prosthesis prior to surgery for immediate loading, to reduce risk of injuring critical anatomical structures and to eliminate manual placement error.     

Transference of virtual planning and planning over biomedical prototypes for dental implant placement using guided surgery

Objectives: This study evaluated the transference of virtual planning and planning over biomedical prototypes for dental implant placement using guided surgery. Material and methods: This experiment was conducted with 11 identical replicas of a human edentulous mandible. For each mandible, models and surgical guides were manufactured using stereolithography. Simulated surgeries were performed on the prototypes. Following this, the implants were placed in the mandible replicas. Superposition of the tridimensional pre‐ and postoperative models was used for virtual evaluation. The real evaluation was conducted by linear measurements directly on the models. Results: The variations in angles and distances between the coronal, central and apical regions of the 22 implants evaluated in this study had mean values <1.45° and 0.41 mm. The correlations between the positions of implant beds in each mandible were fair to very good, according to the distance analyzed and the interpretation guidelines used. Conclusions: According to the results of this study, the variations found in the transference of dental implant positioning to the operative field, determined during virtual planning and obtained in surgeries simulated with biomedical prototypes, confirm the reliability of guided surgery techniques in implantology. To cite this article:
Viegas VN, Dutra V, Pagnoncelli RM, de Oliveira MG. Transference of virtual planning and planning over biomedical prototypes for dental implant placement using guided surgery.
Clin. Oral Impl. Res. 21 , 2010; 290–295.
doi: 10.1111/j.1600‐0501.2009.01833.x     

计算机辅助设计种植导板精确性及其影响因素

数字化已经成为口腔种植领域乃至整个口腔技术发展的新趋势。数字化导板,即牙种植导向模板技术,逐渐走入市场。数字化口腔种植技术凭借直观的术前设计和简易的手术方式,可实现不翻瓣种植及术后即刻修复等,但也存在精准度不确定并由此可能产生严重并发症的问题。本文旨在介绍数字化导板的分类,分析数字化口腔种植技术的优缺点,评价数字化导板的精确性和影响数字化导板精确性的相关因素,以期为临床医师在应用该技术过程中提供参考。     

Precision surgical template for implant placement: a new systematic approach

The importance of a precise surgical template for implant placement cannot be overstated. The radiographic template carries both clinical and radiographic information for the planning of fixture angulation and location. This article describes a systematic approach to the fabrication of a dual-purpose radiographic surgical template. The simple steps result in the accurate transfer of radiographic information to the surgical template with no need for complex equipment or maneuvers. key words: dental implants, implant placement, radiographic template, surgical template     

Texture analysis of cone beam computed tomography images reveals dental implant stability

The aim of this study was to characterize the alveolar bone of edentulous maxillary sites using texture analysis (TA) of cone beam computed tomography (CBCT) images and to correlate the results to the insertion torque, thus verifying whether TA is a predictive tool of final implant treatment. This study was conducted on patients who had received single implants in the maxilla (46 implants) 1 year earlier and whose torque values were properly recorded. Three cross-sections of the sites were selected on CBCT scans. Two regions of interest (ROIs) corresponding to the implant bone site and peri-implant bone were also outlined, according to virtual planning. The CBCT scans were exported to MaZda software, where the two ROIs were delimited following the previously demarcated contours. Values for the co-occurrence matrix were calculated for TA. With regard to the insertion torque value, there was a direct correlation with the contrast of the peri-implant bone (P < 0.001) and an inverse correlation with the entropy of the implant bone site (P = 0.006). A greater contrast indicates a greater torque value for insertion of the implants, and there is a possible association with a lower entropy value of the implant–bone interface.     

Effects of dose reduction on multi‐detector computed tomographic images in evaluating the maxilla and mandible for pre‐surgical implant planning: a cadaveric study

Objective: To assess effects of dose reduction on image quality in evaluating maxilla and mandible for pre‐surgical implant planning using cadavers. Materials and methods: Six cadavers were used for the study using multi‐detector computed tomography (CT) operated at 120 kV and the variable tube current of 80, 40, 20 and 10 mA. A slice thickness of 0.625 mm and pitch 1 were used. Multi‐planar images perpendicular and parallel to dentitions were created. The images were evaluated by five oral radiologists in terms of visibility of the anatomical landmarks including alveolar crest, mandibular canal, floors of the maxillary sinus and nasal cavity, contours/cortical layer of jaw bones and the details of trabecular bone. Observers were asked to determine the quality of the images in comparison with 80 mA images based on the criteria: excellent, good, fair or non‐diagnostic. The average scores of all observers were calculated for each specimen in all exposure conditions. Results: The 40 mA images could visualize such landmarks and were evaluated to be same or almost equivalent in quality to the 80 mA images. Even the 20 mA images could be accepted just for diagnostic purpose for implant with substantial deterioration of the image quality. The 10 mA images may not be accepted because of the obscured contour caused by image noise. Conclusion: Significant dose reduction by lowering mA can be utilized for pre‐surgical implant planning in multi‐detector CT. To cite this article:
Koizumi H, Sur J, Seki K, Nakajima K, Sano T, Okano T. Effects of dose reduction on multi‐detector computed tomographic images in evaluating the maxilla and mandible for pre‐surgical implant planning: a cadaveric study.
Clin. Oral Impl. Res. 21 , 2010; 830–834.
doi: 10.1111/j.1600‐0501.2010.01925.x     

Accuracy of intentionally tilted implant placement in the maxilla using dynamic navigation: a retrospective clinical analysis

The aim of this retrospective study was to investigate the accuracy of dynamic navigation for the placement of intentionally tilted implants in the posterior maxilla. The study included 12 patients with edentulism or continuous multiple tooth loss, who had 48 implants inserted under dynamic navigation guidance in the posterior maxilla. Twenty-four implants near maxillary sinuses were intentionally tilted. The average platform deviation was 1.3 ± 0.4 mm (range 0.8–2.3 mm), apex deviation was 1.1 ± 0.5 mm (range 0.2–2.3 mm), and axis deviation was 3.1 ± 1.0° (range 1.8–6.7°). The other 24 implants were axially positioned. The average platform deviation was 1.5 ± 0.5 mm (range 0.7–3.1 mm), apex deviation was 1.3 ± 0.7 mm (range 0.5–3.1 mm), and axis deviation was 3.2 ± 1.5° (range 1.5–7.7°). There was no significant difference in platform deviation, apex deviation, or axis deviation between the tilted implants and implants in the axial position (P > 0.05). This analysis indicates that a dynamic navigation system can be used as a method of guidance to place intentionally tilted implants as accurately as axially positioned implants in the posterior maxilla, thereby preventing damage to the maxillary sinuses and the need to graft bone.     

Accuracy of Virtually Planned and Template Guided Implant Surgery on Edentate Patients

Purpose: Scientific evidence regarding the accuracy of implants placed into patients by the aid of a surgical template is limited. The objective of the present study was to verify if any variation exists between virtually planned implants' position using a computer, compared with the subsequently clinically placed implants with the aid of a surgical template in the mandible and the maxilla. Material and Methods: A total number of 25 edentate jaws were treated with the aid of a surgical template. In total, 139 implants were inserted. Fifty implants were inserted in the mandible and 89 in the maxilla. A voxel‐based registration method was used to match two separate cone‐beam computed tomography scans of the patients. The implant positions were calculated and compared between the planned implants and the implants' clinical position after more than 1 year after surgery. The results included the linear differences in distance at the level of the hex, the apex, and the depth. The angular differences were presented in degrees. Results: Statistical results indicated some factors with significant deviations. The greatest errors were found when comparing between patients moving during the computed tomography scans and those that did not move. The results showed significant divergence at the level of the hex and apex of the implants. Conclusion: The hypothesis was rejected, as the statistical results indicated that there were significant differences between virtually planned implants' position and the final position of implants placed clinically.     

Accuracy of implant position when placed using static computer-assisted implant surgical guides manufactured with two different optical scanning techniques: a randomized clinical trial

Data from cone beam computed tomography (CBCT) and optical scans (intraoral or model scanner) are required for computer-assisted implant surgery (CAIS). This study compared the accuracy of implant position when placed with CAIS guides produced by intraoral and extraoral (model) scanning. Forty-seven patients received 60 single implants by means of CAIS. Each implant was randomly assigned to either the intraoral group (n = 30) (Trios Scanner, 3Shape) or extraoral group (n = 30), in which stereolithographic surgical guides were manufactured after conventional impression and extraoral scanning of the stone model (D900L Lab Scanner, 3Shape). CBCT and surface scan data were imported into coDiagnostiX software for virtual implant position planning and surgical guide design. Postoperative CBCT scans were obtained. Software was used to compare the deviation between the planned and final positions. Average deviation for the intraoral vs. model scan groups was 2.42° ± 1.47° vs. 3.23° ± 2.09° for implant angle, 0.87 ± 0.49 mm vs. 1.01 ± 0.56 mm for implant platform, and 1.10 ± 0.53 mm vs. 1.38 ± 0.68 mm for implant apex; there was no statistically significant difference between the groups (P > 0.05). CAIS conducted with stereolithographic guides manufactured by means of intraoral or extraoral scans appears to result in equal accuracy of implant positioning.     

Accuracy of magnetic resonance imaging compared with computed tomography for implant planning

Aim: The objective of this study was to evaluate the reliability of magnetic resonance imaging (MRI) compared with computed tomography (CT) for dental implant planning in respect to bone measurements. Methods: Five dry mandibles were submitted to MRI and CT examinations. Each mandible had three specific sites identified with markers, in a total of 15 sites to be studied. The images provided by the MRI and CT examinations were delivered to four specialists in Oral and Maxillofacial Radiology to measure the bone height at the specific sites. Subsequently, the bone height of the dry mandibles was directly measured in the determined sites. The measurements obtained by the specialists in MRI and CT images were compared with the measurements obtained directly from the dry mandibles using the ANOVA test with a 0.05 significance level. Results: The differences between the measurements obtained directly from the dry mandibles and the measurements from the MRI exams varied from 0.13 to 1.67 mm, with 10 sites being overestimated in MRI exams and five sites being underestimated. The differences between the measurements from the dry mandibles and CT exams varied from 0.02 to 1.25 mm, with nine sites being overestimated in CT exams and six sites being underestimated. The differences between the measurements from the MRI and CT exams varied from 0.03 to 1.00 mm, with nine sites giving higher values in MRI exams and six sites giving higher values in CT exams. There were no statistically significant differences between the three grous of measurements (P=0.98). Conclusion: The MRI, when compared with CT, shown to be reliable in respect to bone measurements for dental implant planning.     

Accuracy of a newly developed integrated system for dental implant planning

Objectives: To evaluate the accuracy of the first integrated system for cone-beam CT (CBCT) imaging, dental implant planning and surgical template-aided implant placement.
Materials and methods: On the basis of CBCT scans, a total of 54 implant positions were planned for 10 partially edentulous anatomical patient-equivalent models. Surgical guides were ordered from the manufacturer (SICAT). Two different types of guidance were assessed: for assessment of the SICAT system inherent accuracy vendor's titanium sleeves of 2 mm internal diameter and 5 mm length were utilized for pilot drills. The guide sleeves of the NobelGuide system were implemented for fully guided surgery and implant insertion. Deviations perpendicular to the implant axes at the crestal and apical end, as well as the angle deviations between the virtual planning data and the surgical results, were measured utilizing a follow-up CBCT investigation and referential marker-based registration.
Results: The SICAT system inherent mean deviation rates for the drilled pilot osteotomies were determined to be smaller than 500 μm even at the apical end. Mean angle deviations of 1.18° were determined. Utilizing the NobelGuide sleeve-in-sleeve system for fully guided implant insertion in combination with the investigated template technology enabled to insert dental implants with the same accuracy. Crestal deviations, in general, were significantly lower than the apical deviations.
Conclusion: Although hardly comparable due to different study designs and measurement strategies, the investigated SICAT system's inherent accuracy corresponds to the most favourable results for computer-aided surgery systems published so far. In combination with the NobelGuide surgical set for fully guided insertion, the same accuracy level could be maintained for implant positioning.