Factors influencing transfer accuracy of cone beam CT-derived template-based implant placement

Influence of bone condition on implant placement accuracy with computer-guided surgery

BACKGROUND

The impact of the jaw bone condition, such as bone quantity and quality in the implant placement site, affecting the accuracy of implant placement with computer-guided surgery (CGS) remains unclear. Therefore, this study aimed to evaluate the influence of bone condition, i.e., bone density, bone width, and cortical bone thickness at the crestal bone on the accuracy of implant placement with CGS.

METHODS

A total of 47 tissue-level implants from 25 patients placed in the posterior mandibular area were studied. Implant placement position was planned on the simulation software, Simplant® Pro 16, by superimposing preoperative computed tomography images with stereolithography data of diagnostic wax-up on the dental cast. Implant placement surgery was performed using the surgical guide plate to reflect the planned implant position. The post-surgical dental cast was scanned to determine the position of the placed implant. Linear and vertical deviations between planned and placed implants were calculated. Deviations at both platform and apical of the implant were measured in the bucco-lingual and mesio-distal directions. Intra- and inter-observer variabilities were calculated to ensure measurement reliability. Multiple linear regression analysis was employed to investigate the effect of the bone condition, such as density, width, and cortical bone thickness at the implant site area, on the accuracy of implant placement (α = 0.05).

RESULT

Intra- and inter-observer variabilities of these measurements showed excellent agreement (intra class correlation coefficient ± 0.90). Bone condition significantly influenced the accuracy of implant placement using CGS (p < 0.05). Both bone density and width were found to be significant predictors.

CONCLUSIONS

Low bone density and/or narrow bucco-lingual width near the alveolar bone crest in the implant placement site might be a risk factor influencing the accuracy of implant placement with CGS.

Accuracy of computer-guided implantation in the placement of one-piece ceramic dental implants in the anterior region: A prospective clinical study

Purpose

Placement of one-piece ceramic dental implants requires precision, which can be enhanced by using a computer-guided system. This prospective clinical study examines the accuracy of partially guided implantation in the placement of one-piece ceramic implants in the anterior region.

Materials and methods

One-piece ceramic dental implants were placed in 20 patients who were missing a central or lateral incisor. Partially guided dental implant placements were performed in all cases. The deviations in the implant positions were analyzed by superimposing post-operative cone beam computed tomography images over pre-operative treatment planning images. The results were reported as deviations (mean ± standard deviation) for three aspects (3D offset, mesio-distal, labio-lingual, and apico-coronal) and in three dimensions (the angle, coronal, and apical parts).

Results

Implants were successfully placed in 20 patients. The mean angular deviation was 4.23±1.84°, whereas the mean coronal 3D offset was 0.98±0.48 mm, and the mean apical 3D offset was 1.57±0.46 mm.

Conclusions

A prospective clinical study involving 20 patients was conducted to measure the accuracy of computer-guided implantation of one-piece ceramic dental implants. Accuracy was determined by comparing the planned implant position to the actual position. Greater accuracy can be expected at the coronal part than at the apical part. The coronal 3D offset was found to be the most accurate.

A review of virtual planning software for guided implant surgery - data import and visualization, drill guide design and manufacturing

Background

Virtual implant planning systems integrate (cone beam-) computed tomography data to assess bone quantity and virtual models for the design of the implant-retained prosthesis and drill guides. Five commercially available systems for virtual implant planning were examined regarding the modalities of integration of radiographic data, virtual dental models and the design of drill guides for guided implant surgery. The purpose of this review was to describe the limitations of these available systems regarding the import of imaging data and the design and fabrication of a drill guide.

Methods

The following software systems were examined regarding the import of imaging data and the export of the virtual implant planning for the design and fabrication of a drill guide with the help of two clinical situations requiring dental implant therapy: coDiagnostiX™, DentalWings, Canada (CDX); Simplant Pro™, Dentsply, Sweden (SIM); Smop™, Swissmeda, Switzerland (SMP); NobelClinician™, Nobel Biocare, Switzerland (NC); Implant Studio, 3Shape, Denmark (IST). Assessment criteria included data formats and management as well as the workflow for the design and production of drill guides.

Results

All systems have a DICOM-interface (“Digital Imaging and Communication in Medicine”) for the import of radiographic data. Imaging artefacts could be reduced but not eliminated by manual data processing. The import of virtual dental models in a universal format (STL: Standard Tesselation Language) was possible with three systems; one system could only be used with a proprietary data format.

All systems display three-dimensional surface models or two-dimensional cross-sections with varying orientation for virtual implant planning. Computer aided design and manufacturing (CAD/CAM) of drill guides may be performed by the user with the help of default parameters or solely by the provider of the software and thus without the influence of the clinician.

Conclusion

Data bases of commonly used implant systems are available in all tested software, however not all systems allow to plan and execute fully guided implant placement. An individual design and in-house manufacturing of the drill guide is only available in some software systems. However, at the time of publication most recent software versions showed flexibility in individual design and in-house manufacturing of drill guides.

Newly developed data-matching methodology for oral implant surgery allowing the automatic deletion of metal artifacts in 3D-CT images using new reference markers: A case report

PATIENTS

The patient was a 55-year-old woman with left upper molar free-end edentulism and 9 full cast metal crowns in her mouth. Three three-dimensional (3D) images were superimposed: a computed tomography (CT) image with the patient wearing the CT-matching template (CTMT) with six glass ceramic markers, which hardly generate any artifacts, on the template surface, and oral plaster model surfaces with and without CTMTs. Metal artifacts were automatically removed by a Boolean operation identifying unrealistic images outside the oral plaster model surface. After the preoperative simulation, fully guided oral implant surgery was performed. Two implant bodies were placed in the left upper edentulism. The placement errors calculated by comparing the preoperative simulation and actual implant placement were then assessed by a software program using the 3D-CT bone morphology as a reference. The 3D deviations between the preoperative simulation and actual placement at the entry of the implant body were a maximum 0.48 mm and minimum 0.26 mm. Those at the tip of the implant body were a maximum 0.56 mm and a minimum 0.25 mm.

DISCUSSION

In this case, the maximum 3D deviations at the entry and tip section were less than in previous studies using double CT.

CONCLUSIONS

Accurate image fusion utilizing CTMT with new reference markers was possible for a patient with many metal restorations. Using a surgical guide manufactured by the new matching methodology (modified single CT scan method), implant placement deviation can be minimized in patients with many metal restorations.

How Accurate Is Oral Implant Installation Using Surgical Guides Printed from a Degradable and Steam-Sterilized Biopolymer?

3D printed surgical guides are used for prosthetically-driven oral implant placement. When manufacturing these guides, information regarding suitable printing techniques and materials as well as the necessity for additional, non-printed stock parts such as metal sleeves is scarce. The aim of the investigation was to determine the accuracy of a surgical workflow for oral implant placement using guides manufactured by means of fused deposition modeling (FDM) from a biodegradable and sterilizable biopolymer filament. Furthermore, the potential benefit of metal sleeve inserts should be assessed. A surgical guide was designed for the installation of two implants in the region of the second premolar (SP) and second molar (SM) in a mandibular typodont model. For two additive manufacturing techniques (stereolithography [SLA]: reference group, FDM: observational group) n = 10 surgical guides, with (S) and without (NS) metal sleeves, were used. This resulted in 4 groups of 10 samples each (SLA-S/NS, FDM-S/NS). Target and real implant positions were superimposed and compared using a dedicated software. Sagittal, transversal, and vertical discrepancies at the level of the implant shoulder, apex and regarding the main axis were determined. MANOVA with posthoc Tukey tests were performed for statistical analyses. Placed implants showed sagittal and transversal discrepancies of <1 mm, vertical discrepancies of <0.6 mm, and axial deviations of ≤3°. In the vertical dimension, no differences between the four groups were measured (p ≤ 0.054). In the sagittal dimension, SLA groups showed decreased deviations in the implant shoulder region compared to FDM (p ≤ 0.033), whereas no differences in the transversal dimension between the groups were measured (p ≤ 0.054). The use of metal sleeves did not affect axial, vertical, and sagittal accuracy, but resulted in increased transversal deviations (p = 0.001). Regarding accuracy, biopolymer-based surgical guides manufactured by means of FDM present similar accuracy than SLA. Cytotoxicity tests are necessary to confirm their biocompatibility in the oral environment.

Accuracy of fully guided orthodontic mini-implant placement evaluated by cone-beam computed tomography: a study involving human cadaver heads

OBJECTIVES

The aim of this study was to evaluate the accuracy of fully guided orthodontic mini-implant (OMI) placements supported by tooth- (TBGs) or gingiva-borne silicone guides (GBGs) based on virtually superimposed lateral cephalograms on virtual plaster models.

MATERIALS AND METHODS

Lateral cephalograms and corresponding plaster models were virtually superimposed for the planning of OMI positions; fully guided TBGs and GBGs were fabricated (each, n = 10). A total of 40 OMIs were inserted in a paramedian position into the palate of 20 human cadavers. Postoperative cone-beam computer tomographies (CBCTs) were carried out, and an accuracy evaluation was performed by comparing preoperative planning models and postoperative CBCTs. Deviations of the axis, tip, centre of the shoulder and vertical position of each of the implants were evaluated. Furthermore, the transfer accuracy measured by postoperative CBCT scans were compared with the accuracy determined using an intraoral scanner.

RESULTS

A significant deviation between TBGs (2.81° SD 2.69) and GBGs (6.22° SD 4.26) regarding implant angulation was evaluated (p = 0.005). Implant tip and implant shoulder deviations revealed no statistical differences between the guides. Accuracy values of oral scans regarding vertical deviations were significantly more inaccurate when compared with CBCTs (p < 0.001).

CONCLUSIONS

The accuracy of an OMI position can be significantly increased by using a guide extension over the teeth. Vertical implant positions presented the lowest deviations. Postoperative oral scans and CBCTs represent diverging accuracy measurements when compared with virtual planning.

CLINICAL RELEVANCE

Users must keep in mind that despite virtual planning deviations, inaccuracies of a few millimetres may occur.

Alveolar ridge preservation and primary stability as influencing factors on the transfer accuracy of static guided implant placement: a prospective clinical trial

Background

The aim of this prospective clinical study was to investigate differences between virtually planned and clinically achieved implant positions in completely template-guided implant placements as a function of the tooth area, the use of alveolar ridge preservation, the implant length and diameter, and the primary implant stability.

Methods

The accuracy of 48 implants was analyzed. The implants were placed in a completely template-guided manner. The data of the planned implant positions were superimposed on the actual clinical implant positions, followed by measurements of the 3D deviations in terms of the coronal (dc) and apical distance (da), height (h), angulation (ang), and statistical analysis.

Results

The mean dc was 0.7 mm (SD: 0.3), the mean da was 1.4 mm (SD: 0.6), the mean h was 0.3 mm (SD: 0.3), and the mean ang was 4.1° (SD: 2.1). The tooth area and the use of alveolar ridge preservation had no significant effect on the results in terms of the implant positions. The implant length had a significant influence on da (p = 0.02). The implant diameter had a significant influence on ang (p = 0.04), and the primary stability had a significant influence on h (p = 0.02).

Conclusion

Template-guided implant placement offers a high degree of accuracy independent of the tooth area, the use of measures for alveolar ridge preservation or the implant configuration.

A clinical benefit is therefore present, especially from a prosthetic point of view.

Trial registration

German Clinical Trial Register and the International Clinical Trials Registry Platform of the WHO: DRKS00005978; date of registration: 11/09/2015.

Digitally planned root end surgery with static guide and custom trephine burs: A case report

INTRODUCTION

Apicoectomy is an endodontic surgical intervention that requires high precision. The computer-assisted static guided approach has proven to increase the precision of dental implantation in a significant manner. The authors sought to transfer this precision to root-end resection with the use of custom designed trephine burs manufactured specifically for use in targeted endodontic microsurgery.

METHODS

A set of custom bone trephines were designed and manufactured, then their digital models were integrated into an already existing implant surgical planning software, in cooperation with the software developer. Apicoectomy was performed in an actual case with the help of the new system.

RESULTS

It has become possible to plan root end removal in the virtual space and to manufacture 3D printed static surgical guides to help the execution of the surgery. A patient with persistent periapical lesion was successfully treated without complication. The 6-month follow-up found uneventful healing.

CONCLUSION

The presented system is a step toward a standardized digital system and workflow dedicated to guided endodontic surgery.

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.

Accuracy of static computer-assisted implant placement in anterior and posterior sites by clinicians new to implant dentistry: in vitro comparison of fully guided, pilot-guided, and freehand protocols

Background

One of the challenges encountered by clinicians new to implant dentistry is the determination and controlling of implant location. This study compared the accuracy of fully guided (FG) and pilot-guided (PG) static computer-assisted implant placement (sCAIP) protocols against the conventional freehand (FH) protocol for placing single anterior and posterior implants by recently introduced clinicians to implant dentistry.

Material and methods

Ten clinicians new to implant dentistry inserted one anterior (central incisor) and one posterior (first molar) implants per protocol in training maxillary models. The FG protocol involved drilling and implant placement through the guide, while the PG protocol controlled the pilot drilling only. The FH implant placement was completed without the aid of any guide. A total of 30 models were used, and 60 implants were inserted. The implant vertical, horizontal neck, horizontal apex, and angle deviations from planned positions were calculated.

Results

The FG protocol provided the most accurate implant placement in relation to horizontal neck (0.47 mm–0.52 mm), horizontal apex (0.71 mm–0.74 mm), and angle deviations (2.42^o–2.61^o). The vertical deviation was not significantly different among the different protocols. The PG protocol was generally similar to the FH protocol with a horizontal neck deviation of 1.01 mm–1.14 mm, horizontal apex deviation of 1.02 mm–1.35 mm, and angle deviation of 4.65^o–7.79^o. The FG protocol showed similarity in the accuracy of the anterior and posterior implants. There was a tendency for inferior accuracy for posterior implants compared with anterior implants for the PG and FH protocols.

Conclusions

In the hands of recently introduced clinicians to implant dentistry, it appears that the accuracy of the FG protocol was superior to the other protocols and was not influenced by the position of the implants. The PG and FH protocols showed inferior accuracy for posterior implants compared with anterior implants.

Stereolithographic Surgical Guide with a Combination of Tooth and Bone Support: Accuracy of Guided Implant Surgery in Distal Extension Situation

A distal free-end situation could result in insufficient stability of the surgical guide, and could reduce accuracy of the static guided implant surgery (sGIS). The purpose of this study was to investigate the accuracy of sGIS using a combination tooth-and-bone supported stereolithographic (SLA) surgical guide in distal extension situation. Thirty dentists, each placed three implants at the Federal Dentaire Internationale (FDI) teeth positions #46, #47 (a distal extension situation), and #36 (a single tooth gap) via the surgical guide on a model fixed to a manikin. Pre- and post-operative computed tomography (CT) images of the models were superimposed, and the positional and angular deviations of the implants were measured with metrology software. An analysis of variance (ANOVA) test was performed to evaluate the intergroup differences. No significant differences were found for all the positional and angular deviations among the three implant sites, except the bucco-lingual deviation at the implant platform in the #47 position (0.43 ± 0.19 mm) that was significantly larger than the #46 (0.21 ± 0.14 mm) and #36 (0.24 ± 0.25 mm) positions (p < 0.0001). Within the limits of this study, we conclude that, in distal extension situation of missing mandibular molars, adding a bone-supported strut in the distal part of the surgical guide can be beneficial to the accuracy of the sGIS.

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.

Accuracy and clinical safety of guided root end resection with a trephine: a case series

Background

Root-end resection is an endodontic surgical intervention that requires high precision so that all ramifications and lateral canals so as infected tissues are eliminated. An exploratory study was conducted to justify the clinical safety and accuracy of guided root-end resection with a trephine.

Methods

Fourteen root-end resections were performed in 11 patients. With the aid of computer tomography and rapid prototyping a stereolithographically fabricated, tooth-supported surgical template was used to guide trephinations. Surgery was performed using the printed surgical stent and a trephine was used not only for the osteotomy but for the root end resection as well.

Results

The root end was successfully and completely resected by the trephine in all cases. No intraoperative complications were observed in any of the cases, and the patients were free of symptoms indicating recurrence or complications at the 6-month follow-up. The median angular deviation of the trephination was 3.95° (95% CI: 2.1–5.9), comparable to the angular deviation of guided implant surgery. The mean apex removal error (ARE) was 0.19 mm (95% CI: 0.03–0.07). The mean osteotomy depth error (ODE) was 0.37 mm (95% CI: 0.15–1.35). Overpenetration was a characteristic finding, which indicates the necessity of a stop-trephine.

Conclusions

Within the limitations of this study, we conclude that our results support the use of guided trephination for root-end resection.

Use of three points to determine the accuracy of guided implantation

Aim

'This study aims to establish an open-source algorithm using Python to analyze the accuracy of guided implantation, which simplifies interstudy comparisons.

Methods

Given ≥3 landmark pairs, this Tri-Point (TriP) method can register images. With ≥4 landmark pairs, TriP can calculate system errors for image registration. We selected 8 indicators from the literature. Considering development errors in new bone on cone beam computed tomography (CBCT), we added the indicators of apical rectified deviation (ARD) and coronal rectified deviation (CRD), providing accurate references but neglecting depth deviations. Our program can calculate and output these indicators. To evaluate the TriP method’s feasibility, an implantation group assisted by a Visual Direction-INdicating Guide (VDING) was analyzed. Accuracy was measured with the traditional and proposed TriP methods. Factors affecting the system error of the method were then analyzed.

Results

Comparisons with paired-sample t-tests showed that our TriP method was similar to the traditional method in evaluating implantation accuracy, with no significant difference (P>0.05). The average system error was 0.30±0.10 mm when the TriP method evaluated the VDING template. The results showed that increasing the provided landmarks from 4 to 5 pairs decreased the between-group differences significantly (P<0.05). With ≥6 pairs of landmarks, the system error tended to be stable, and the groups showed no statistically significant differences (P>0.05). Large distances between landmarks are helpful in reducing system error, as demonstrated with a geometric method.

Conclusions

This study established an open-source algorithm to analyze the accuracy of guided implantation with system errors reported.

Guided implant surgery risks and their prevention

Ideal implant placement may reduce surgical complications, such as nerve injury and lingual cortical plate perforation, and minimize the likelihood of functional and prosthetic compromises. Guided implant surgery (GIS) has been used as the means to achieve ideal implant placement. GIS refers to the process of digital planning, custom-guide fabrication, and implant placement using the custom guide and an implant system-specific guided surgery kit. GIS includes numerous additional steps beyond the initial prosthetic diagnosis, treatment planning, and fabrication of surgical guide. Substantial errors can occur at each of these individual steps and can accumulate, significantly impacting the final accuracy of the process with potentially disastrous deviations from proper implant placement. Pertinent overall strategies to reduce or eliminate these risks can be summarized as follows: complete understanding of the possible risks is fundamental; knowledge of the systems and tools used is essential; consistent verification of both diagnostic and surgical procedures after each step is crucial; proper training and surgical experience are critical. This review article summarizes information on the accuracy and efficacy of GIS, provides insight on the potential risks and problems associated with each procedural step, and offers clinically relevant recommendations to minimize or eliminate these risks.

In vivo accuracy of tooth surface reconstruction based on CBCT and dental MRI-A clinical pilot study

OBJECTIVES

Guided implant surgery (GIS) requires alignment of virtual models to reconstructions of three-dimensional imaging. Accurate visualization of the tooth surfaces in the imaging datasets is mandatory. In this prospective clinical study, in vivo tooth surface accuracy was determined for GIS using cone-beam computed tomography (CBCT) and dental magnetic resonance imaging (dMRI).

MATERIALS AND METHODS

CBCT and 3-Tesla dMRI were performed in 22 consecutive patients (mean age: 54.4 ± 15.2 years; mean number of restorations per jaw: 6.7 ± 2.7). Altogether, 92 teeth were included (31 incisor, 29 canines, 20 premolars, and 12 molars). Surfaces were reconstructed semi-automatically and registered to a reference standard (3D scans of stone models made from full-arch polyether impressions). Reliability of both methods was assessed using intraclass correlation coefficients. Accuracy was evaluated using the two one-sided tests procedure with a predefined equivalence margin of ±0.2 mm root mean square (RMS).

RESULTS

Inter- and intrarater reliability of tooth surface reconstruction were comparable for CBCT and dMRI. Geometric deviations were 0.102 ± 0.042 mm RMS for CBCT and 0.261 ± 0.08 mm RMS for dMRI. For a predefined equivalence margin, CBCT and dMRI were statistically equivalent. CBCT, however, was significantly more accurate (p ≤ .0001). For both imaging techniques, accuracy did not differ substantially between different tooth types.

CONCLUSION

Cone-beam computed tomography is an accurate and reliable imaging technique for tooth surfaces in vivo, even in the presence of metal artifacts. In comparison, dMRI in vivo accuracy is lower. Still, it allows for tooth surface reconstruction in satisfactory detail and within acceptable acquisition times.

Pilot-drill guided vs. full-guided implant insertion in artificial mandibles-a prospective laboratory study in fifth-year dental students

Background

As a growing field in dentistry, the practical education during the undergraduate curriculum in implant dentistry should be extended. Not only the theoretical background but also practical skills are crucial to place implants in patients. In order to determine the exact implant position, several positioning aids are available. In the present laboratory study, the accuracy of implant insertion using two different guiding modes in a group of inexperienced participants was assessed.

Methods

After three-dimensional planning using the data of a cone beam computed tomography of artificial mandibles, surgical templates were manufactured by thermoforming. In region 35, a sleeve for the pilot drill was used, whereas in region 45, a sleeve allowing a full-guided implant insertion was inserted. Subsequently, a total of 104 implants were placed by 52 undergraduates. Radiographical assessment of the three-dimensional accuracy was performed. Furthermore, the time required to insert the implants was recorded. Statistical analysis followed.

Discussion

When comparing the three-dimensional accuracy of the virtually planned to the actual inserted implant, a statistically significantly higher accuracy in three-dimensional angulation was achieved for the full-guided (3.388 ± 1.647°) compared to the pilot-drill guided mode (5.792 ± 3.290°). Furthermore, the time required to insert the implant was shorter for the full-guided template (6.23 ± 1.78 min) vs. for the pilot-drill guided (8.84 ± 2.39 min). Both differences reached a statistical significance (p < 0.001).

Conclusion

Within the limit of this laboratory study, the results suggest that inexperienced surgeons benefit from a full-guided implant insertion. However, the clinical effects have to be discussed as the mismatch was varying in the decimillimeter range.

Factors that Influence Direction Deviation in Freehand Implant Placement

PURPOSE

This retrospective study investigates the accuracy of freehand implant placement and whether the factors of presence of an adjacent tooth, implant quadrant, number of missing teeth, and location of the implant site influence direction and angulation deviations.

MATERIALS AND METHODS

According to specific inclusion and exclusion criteria, a total of 112 implants from 75 partially edentulous patients were recruited for this retrospective study. The implants were inserted using a freehand approach by one experienced clinician (right-handed). The full thickness flap was elevated to expose the alveolar bone in the implant surgery, and the implant crown consisted of an all-ceramic restoration retained by cement. The planned implant position was preoperatively determined using implant planning software. The postoperative implant position was determined by analyzing the alignment after optically scanning the dentition using a specifically designed registration model in Geomagic Studio software. The deviations between the planned and postoperative implant positions were then calculated. The outcomes included direction and angulation deviations between the planned and postoperative implant positions. All data were analyzed by ANOVA, Bonferroni correction, regression analysis, and one-sample t-tests conducted using SPSS.

RESULTS

The 3D deviations between planned and postoperative implant positions were 1.22 ± 0.63 mm at the entrance point, 1.91 ± 1.17 mm at the apical point, and 7.93 ± 5.56° in angulation. The presence of adjacent teeth influenced deviations in the mesiodistal (F = 4.338, p = 0.006) and buccolingual directions (F = 3.017, p = 0.033) at the entrance point and mesiodistal angulation (F = 7.979, p < 0.001). The quadrant influenced deviation in the buccolingual direction at the apical point (F = 6.093, p = 0.001) and buccolingual angulation (F = 6.457, p < 0.001). The number of missing teeth had no effect on deviations of direction and angulation of implants. The location of the implant site affected the deviation in the buccolingual direction at the entrance point (F = 3.096, p = 0.049) and the mesiodistal direction at the apical point (F = 3.724, p = 0.027).

CONCLUSION

The 3D accuracy of freehand-placed implants could be acceptable in clinical situations. The results showed that the presence of an adjacent tooth and the quadrant and the location of the implant site influenced the direction and angulation deviations of the implant position; however, the factor of number of missing teeth did not.

The accuracy of static vs. dynamic computer-assisted implant surgery in single tooth space: A randomized controlled trial

OBJECTIVES

The aim of this RCT was to compare the accuracy of implant placement between static and dynamic computer-assisted implant surgery (CAIS) systems in single tooth space.

MATERIALS AND METHODS

A total of 60 patients in need of a single implant were randomly assigned to two CAIS groups (Static n = 30, Dynamic n = 30) and implants were placed by one surgeon. Preoperative CBCT was transferred to implant planning software to plan the optimal implant position. Implants were placed using either stereolithographic guide template (Static CAIS) or implant navigation system (Dynamic CAIS). Postoperative CBCT was imported to implant planning software, and deviation analysis with the planned position was performed. Primary outcomes were the deviation measurements at implant platform, apex, and angle of placement. Secondary outcome was the distribution of the implant deviation into each 3D direction.

RESULTS

The mean deviation at implant platform and implant apex in the static CAIS group was 0.97 ± 0.44 mm and 1.28 ± 0.46 mm, while that in the dynamic CAIS group was 1.05 ± 0.44 mm and 1.29 ± 0.50 mm, respectively. The angular deviation in static and dynamic CAIS group was 2.84 ± 1.71 degrees and 3.06 ± 1.37 degrees. None of the above differences between the two groups reached statistical significance. The deviation of implants toward the mesial direction in dynamic CAIS group was significantly higher than that of the static CAIS (p = 0.032).

CONCLUSIONS

Implant placement accuracy in single tooth space using dynamic CAIS appear to be the same to that of static CAIS. (Thai Clinical Trials Registry TCTR20180826001).

Is Digital Guided Implant Surgery Accurate and Reliable?

The digital workflow for computer-aided implant surgery includes a range of steps leading to generation of a prosthetically driven, 3-dimensional virtual plan, which is transitioned into the patient's mouth by the surgical guide and protocol. Guided implant surgery is believed to be accurate and reliable compared with free-handed implant surgery. However, deviation between implant virtual plan and implant real position may occur as a result of accumulated errors throughout the digital workflow. This article reviews the digital workflow of static computer-aided implant surgery. Factors that may affect the accuracy and clinical outcome of the guided surgery are also reviewed.

Accuracy of linear measurements on CBCT images related to presurgical implant treatment planning: A systematic review

OBJECTIVE

The aim of this systematic review was to identify, review, analyze, and summarize available evidence on the accuracy of linear measurements when using maxillofacial cone beam computed tomography (CBCT) specifically in the field of implant dentistry.

MATERIAL AND METHODS

The search was undertaken in April 2017 in the National Library of Medicine database (Medline) through its online site (PubMed), followed by searches in the Cochrane, EMBASE, ScienceDirect, and ProQuest Dissertation and Thesis databases. The main inclusion criterion for studies was that linear CBCT measurements were performed for quantitative assessment (e.g., height, width) of the alveolar bone at edentulous sites or measuring distances from anatomical structures related to implant dentistry. The studies should compare these values to clinical data (humans) or ex vivo and/or experimental (animal) findings from a "gold standard."

RESULTS

The initial search yielded 2,516 titles. In total, 22 studies were included in the final analysis. Of those, two were clinical and 20 ex vivo investigations. The major findings of the review indicate that CBCT provides cross-sectional images that demonstrate high accuracy and reliability for bony linear measurements on cross-sectional images related to implant treatment. A wide range of error has been reported when performing linear measurements on CBCT images, with both over- and underestimation of dimensions in comparison with a gold standard. A voxel size of 0.3 to 0.4 mm is adequate to provide CBCT images of acceptable diagnostic quality for implant treatment planning.

CONCLUSIONS

CBCT can be considered as an appropriate diagnostic tool for 3D preoperative planning. Nevertheless, a 2 mm safety margin to adjacent anatomic structures should be considered when using CBCT. In clinical practice, the measurement accuracy and reliability of linear measurements on CBCT images are most likely reduced through factors such as patient motion, metallic artefacts, device-specific exposure parameters, the software used, and manual vs. automated procedures.

Methods Used to Assess the 3D Accuracy of Dental Implant Positions in Computer-Guided Implant Placement: A Review

The purpose of this review is to examine various assessment methods in order to compare the accuracy between the virtually planned and clinically achieved implant positions. In this review, comparison methods using pre- and post-operative computed topography (CT) data and digital impressions for definitive prosthesis will be described. The method for the displacement and strain for quantification of the error will also be explored. The difference between the planned and the actual implant placement position in guided implant surgery is expressed as an error. Assessing the accuracy of implant-guided surgery can play an important role as positive feedback in order to reduce errors. All of the assessment methods have their own inevitable errors and require careful interpretation in evaluation.

Computer-based implant planning involving a prefabricated custom tray with alumina landmark structures

The purpose of this technical report was to describe a method for the fabrication of a custom tray with landmark structures to coordinate cone beam computed tomography and scan data for use in guided implant surgery in patients with numerous artifact-causing metal prostheses. The fabricated custom tray can be used to coordinate cone beam computed tomography data and scan data from the dentition, as well as to fabricate the prostheses.

The accuracy of a 3D printing surgical guide determined by CBCT and model analysis

PURPOSE

The aim of this clinical study was to assess the accuracy of the implants placed using a universal digital surgical guide.

MATERIALS AND METHODS

Among 17 patients, 28 posterior implants were included in this study. The digital image of the soft tissue acquired from cast scan and hard tissue from CBCT have been superimposed and planned the location, length, diameter of the implant fixture. Then digital surgical guides were created using 3D printer. Each of angle deviations, coronal, apical, depth deviations of planned and actually placed implants were calculated using CBCT scans and casts. To compare implant positioning errors by CBCT scans and plaster casts, data were analyzed with independent samples t-test.

RESULTS

The results of the implant positioning errors calculated by CBCT and casts were as follows. The means for CBCT analyses were: angle deviation: 4.74 ± 2.06°, coronal deviation: 1.37 ± 0.80 mm, and apical deviation: 1.77 ± 0.86 mm. The means for cast analyses were: angle deviation: 2.43 ± 1.13°, coronal deviation: 0.82 ± 0.44 mm, apical deviation: 1.19 ± 0.46 mm, and depth deviation: 0.03 ± 0.65 mm. There were statistically significant differences between the deviations of CBCT scans and cast.

CONCLUSION

The model analysis showed lower deviation value comparing the CBCT analysis. The angle and length deviation value of the universal digital guide stent were accepted clinically.

Real Versus Virtual Position of Single Implants Installed in Premaxilla via Guided Surgery: A Proof of Concept Analyzing Positional Deviations

The aim of this research letter was to report the results of a pilot study designed to compare the real and virtual position of implants placed using computer-guided flapless implant surgery for single restorations in the premaxilla. A total of 8 patients (2 men and 6 women) with a mean age of 40 years old (range: 32-73 years) had a total of 11 implants inserted using a tooth-supported stereolithographic guide. After implant placement, the positions (coronal, central, and apical) and angulation of the implants installed in relation to those planned were determined via the superposition of pre- and postoperative 3-dimensional models using Dental Slice software (Bioparts, Brasília, Brazil). The mean angular deviation was 2.54° ± 0.71°. The deviations found for the coronal, central, and apical positions were 1.3 ± 0.77 mm, 1.49 ± 0.58 mm, and 2.13 ± 1.32 mm, respectively.

Accuracy of the match between cone beam computed tomography and model scan data in template-guided implant planning: A prospective controlled clinical study

BACKGROUND

Template-guided implant placement is a method for optimal implant positioning from a prosthetic and surgical viewpoint. The treatment planning is based on three-dimensional X-ray data and model scan data, as well as on prosthetic planning (set-up). These data are matched (superimposed) with the aid of an X-ray template or by manual matching without special referencing.

PURPOSE

The objective of this prospective controlled clinical study was to determine and compare the accuracy of the match with and without an additional X-ray template.

MATERIALS AND METHODS

The DICOM data of the cone beam computed tomography (CBCT) were converted into surface data sets and then superimposed on model scan data using three different methods (manually, based on an X-ray template, or semi-automatically with computer assistance). The mean deviations between these results of these matching methods were investigated.

RESULTS

The procedures achieved a matching accuracy of 0.2 mm on average. This corresponds to the resolution of the CBCT (0.2 voxels). Further studies are necessary to verify the procedure even for patients with few (0-4) residual teeth.

CONCLUSION

In the presence of a sufficient number of residual teeth, the manual matching of model scan data with CBCT data is sufficiently accurate for implant planning and template-guided implementation. The results of the present study suggest that X-ray templates can be dispensed with saving the patient a substantial amount of time and money.

Flapless dental implant surgery and use of cone beam computer tomography guided surgery

Flapless implant surgery is increasing in popularity, particularly due to advances and increased usage of cone beam computed tomography (CBCT) and dental implant treatment planning software allowing three-dimensional assessment of the implant site. It is the aim of the article to provide an overview of flapless implant surgery and CBCT guided flapless implant surgery and summarise the literature with regard to the effectiveness of this surgical technique.

Registration of cone beam computed tomography data and intraoral surface scans - A prerequisite for guided implant surgery with CAD/CAM drilling guides

OBJECTIVES

Guided implant surgery (GIS) is performed with drilling guides that are produced on the virtual tooth model using CAD/CAM technology. The prerequisite for this workflow is the alignment of patients cone beam computed tomography CBCT and surface scan (registration). Dental restorations may cause deteriorating imaging artifacts in CBCT data, which in turn can have an impact on the registration process. The influence of the user and the preprocessing of data and of image artifacts on the registration accuracy were examined.

MATERIAL AND METHODS

CBCT data and intraoral surface scans of 36 patients were used for virtual implant planning in coDiagnostiX (Dentalwings, Montreal, Canada). CBCT data were reconstructed to a three-dimensional anatomical model with the default settings provided by the software and also manually by four different examiners. Subsequently, the CBCT and intraoral surface models were registered by each examiner with the help of anatomical landmarks. Patients' data were subdivided into four groups (A-D) according to the number of metallic restorations: A = 0-2 restorations, B = 3-5 restorations, C = 6-8 restorations and D > 8 restorations. After registration, the distances between CBCT and dental surface models were measured. Linear regression models were used to assess the influence of the segmentation, the examiner and to the number of restorations (P < 0.05).

RESULTS

The deviations between surface scan and CBCT models accounted to 0.54 mm (mean). The mean deviations were 0.69 mm (max. 24.8 mm) and 0.4 mm (max. 9.1 mm) for default and manual segmentation, respectively. Mean deviations of 0.36 mm (Group A), 0.43 mm (Group B), 0.67 mm (Group C) and 1.01 mm (Group D) were recorded. The segmentation (P = 0.000), the user (P = 0.0052) and the number of restorations (P = 0.0337) had a significant influence on the registration accuracy.

CONCLUSIONS

The deviation between CBCT and surface scan model resulting from inaccurate registration is transferred to the surgical field and results in a deviation between the planned and actual implant position. The registration accuracy in commercial virtual implant planning software is significantly influenced by the preprocessing of imported data, by the user and by the number of restorations resulting in clinically non-acceptable deviations encoded in drilling guides.

Accuracy of computer-assisted implant placement with insertion templates

Objectives: The purpose of this study was to assess the accuracy of computer-assisted implant insertion based on computed tomography and template-guided implant placement.

Material and methods: A total of 246 implants were placed with the aid of 3D-based transfer templates in 181 consecutive partially edentulous patients. Five groups were formed on the basis of different implant systems, surgical protocols and guide sleeves. After virtual implant planning with the CoDiagnostiX Software, surgical guides were fabricated in a dental laboratory. After implant insertion, the actual implant position was registered intraoperatively and transferred to a model cast. Deviations between the preoperative plan and postoperative implant position were measured in a follow-up computed tomography of the patient’s model casts and image fusion with the preoperative computed tomography.

Results: The median deviation between preoperative plan and postoperative implant position was 1.0 mm at the implant shoulder and 1.4 mm at the implant apex. The median angular deviation was 3.6º. There were significantly smaller angular deviations (P=0.000) and significantly lower deviations at the apex (P=0.008) in implants placed for a single-tooth restoration than in those placed at a free-end dental arch. The location of the implant, whether in the upper or lower jaw, did not significantly affect deviations. Increasing implant length had a significant negative influence on deviations from the planned implant position. There was only one significant difference between two out of the five implant systems used.

Conclusion: The data of this clinical study demonstrate the accuracy and predictable implant placement when using laboratory-fabricated surgical guides based on computed tomography.