Accuracy of a real-time surgical navigation system for the placement of quad zygomatic implants in the severe atrophic maxilla: A pilot clinical study

Accuracy of freehand versus dynamic computer-assisted zygomatic implant placement: An in-vitro study

OBJECTIVE

To compare the accuracy of zygomatic implant placement using a dynamic computer-assisted implant surgery system (D-CAIS) versus the traditional freehand approach.

METHODS

An experimental in vitro study was conducted using 10 stereolithographic models randomized to two groups: D-CAIS (test group) and freehand placement (control group). A single zygomatic implant was placed on each side of the models. The accuracy of implant placement was assessed by superimposing the actual postoperative implant position, obtained via cone-beam computed tomography (CBCT), with the virtual preoperative surgical plan from the preoperative CBCT. Additionally, the operated side and surgery duration were recorded. Descriptive statistics and bivariate analyses were performed to evaluate the data.

RESULTS

The D-CAIS group demonstrated significantly greater accuracy across most outcome variables. Reductions in angular (MD = -5.33°; 95 %CI: -7.37 to -3.29; p < 0.001), coronal global (MD = -2.26 mm; 95 %CI: -2.97 to -1.55; p < 0.001), coronal horizontal 2D (MD = -1.96 mm; 95 %CI: -2.60 to -1.32; p < 0.001) and apical global deviations (MD = -3.37 mm; 95 %CI: -4.36 to -2.38; p < 0.001) were observed. Accuracy in the freehand group varied significantly between operated sides. However, the surgical procedures in the D-CAIS group were significantly longer (MD = 11.90 mins; 95 %CI: 9.37 to 14.44; p < 0.001).

CONCLUSIONS

D-CAIS navigation systems offer significantly greater accuracy in zygomatic implant placement compared to the traditional freehand technique. Additionally, D-CAIS systems may minimize discrepancies in accuracy between operated sides, though their use is associated with an increase in the duration of surgery.

CLINICAL SIGNIFICANCE

D-CAIS navigation systems improve the accuracy of zygomatic implant placement. However, an increase in the duration of surgery is to be expected.

Accuracy of freehand surgery, static and dynamic computer assisted surgery on zygomatic implant placement: A systematic review and meta-analyses

Real-time surgical navigation systems (dynamic computer-aided surgery, d-CAIS) and static guided surgery (static computer-aided surgery, s-CAIS) have been shown to enhance the accuracy of zygomatic implant (ZI) placement. The objective of this systematic review was to evaluate and compare the accuracy and risk of complications associated with d-CAIS and s-CAIS in ZI placement. A systematic review of published studies involving more than 4 patients was conducted to assess and compare the accuracy of d-CAIS and s-CAIS in zygomatic implant placement. Only one study included freehand ZI placement as a control. The primary outcomes measured were the accuracy of implant placement relative to preoperative planning, with a secondary focus on evaluating any potential complications. Out of 903 screened studies, 14 met the inclusion criteria. Freehand zygomatic implant placement was used as a control in only 1 study. The results revealed a mean apex deviation of 2.07 mm (95% CI: 2.01 to 2.13; I2 = 83.14%) for d-CAIS, 1.29 mm (95% CI: 1.15 to 1.43; I2 = 94.5%) for s-CAIS, and 4.98 mm (95% CI: 3.59 to 6.37; I2 = not assessable) for freehand placement. Reported complications included mucositis, reversible bilateral sinusitis, oroantral fistula, unspecified reversible postoperative complications, and fracture of the anterior wall of the zygoma. Both CAIS systems demonstrated high accuracy and safety in ZI placement, with a nearly 99% success rate at 6 months of follow-up. These findings suggest that both d-CAIS and s-CAIS are reliable methods for improving the precision and reducing the risks associated with ZI procedures.

Dynamic navigation-guided robotic placement of zygomatic implants

OBJECTIVES

To assess the feasibility and accuracy of a new prototype robotic implant system for the placement of zygomatic implants in edentulous maxillary models.

METHODS

The study was carried out on eight plastic models. Cone beam computed tomographs were captured for each model to plan the positions of zygomatic implants. The hand-eye calibration technique was used to register the dynamic navigation system to the robotic spaces. A total of 16 zygomatic implants were placed, equally distributed between the anterior and the posterior parts of the zygoma. The placement of the implants (ZYGAN®, Southern Implants) was carried out using an active six-jointed robotic arm (UR3e, Universal Robots) guided by the dynamic navigation coordinate transformation matrix. The accuracy of the implant placement was assessed using EvaluNav and GeoMagicDesignX® software based on pre- and post-operative CBCT superimposition. Descriptive statistics for the implant deviations and Pearson's correlation analysis of these deviations to force feedback recorded by the robotic arm were conducted.

RESULTS

The 3D deviations at the entry and exit points were 1.80 ± 0.96 mm and 2.80 ± 0.95 mm, respectively. The angular deviation was 1.74 ± 0.92°. The overall registration time was 23.8 ± 7.0 min for each side of the model. Operative time excluding registration was 66.8 ± 8.8 min for each trajectory. The exit point and angular deviations of the implants were positively correlated with the drilling force perpendicular to the long axis of the handpiece and negatively correlated with the drilling force parallel to the long axis of the handpiece.

CONCLUSION

The errors of the dynamic navigation-guided robotic placement of zygomatic implants were within the clinically acceptable limits. Further refinements are required to facilitate the clinical application of the tested integrated robotic-dynamic navigation system.

CLINICAL SIGNIFICANCE

Robotic placement of zygomatic implants has the potential to produce a highly predictable outcome irrespective of the operator's surgical experience or fatigue. The presented study paves the way for clinical applications.

Combined static and dynamic computer-guided surgery for prosthetically driven zygomatic implant placement

OBJECTIVES

To propose and validate a minimally invasive combined static and dynamic computer assisted implant surgery (CAIS) workflow for zygomatic implant (ZI) placement.

METHODS

A combined approach leveraging static CAIS for initial positioning, complemented by dynamic CAIS for real-time control of the angle, depth and width was proposed. Fourteen consecutive patients (age: 60.3±9.8 years; 8 females) seeking ZI-supported restoration were enrolled. A single anatomically and prosthetically driven ZI on either the unilateral zygoma or bilateral zygomata was planned and placed using the proposed approach. The zygomatic anatomy-guided approach (ZAGA) type and the ZI length were recorded. The angular, coronal global, and apical global deviation between the planned and placed positions were measured by overlapping post- and pre-operative cone beam computer tomography. Comparisons were made between the left and right sides across the ZAGA type and ZI length. Statistical significance was set at P<0.05.

RESULTS

22 ZIs were placed using the combined approach and 13 immediate loading prostheses were delivered, with one patient restored 6 months after surgery. The angular deviations and coronal global deviations were 1.99±0.17° and 1.21±0.45 mm, respectively. The median apical global deviation was 1.67 mm (interquartile range [IQR]: 1.11-1.93 mm). No significant differences were found between the left and right sides across the ZAGA type or ZI length. All ZIs remained stable over a median follow-up of 14.5 months (IQR: 7-20 months).

CONCLUSIONS

The proposed combination of static and dynamic CAIS is safe, reliable, accurate, and robust for ZI placement.

CLINICAL SIGNIFICANCE

This pilot study proposed a minimally invasive ZI placement method that combined static and dynamic computer-guided surgery. The implant positioning accuracy achieved using this approach validated its safety, reliability, accuracy, and robustness. The combined approach may reduce the technique sensitivity of ZI placement, facilitating future rehabilitation of severely atrophic or defective maxillae.

Accuracy of augmented reality navigated surgery for placement of zygomatic implants: a human cadaver study

Purpose

Placement of zygomatic implants in the most optimal prosthetic position is considered challenging due to limited bone mass of the zygoma, limited visibility, length of the drilling path and proximity to critical anatomical structures. Augmented reality (AR) navigation can eliminate some of the disadvantages of surgical guides and conventional surgical navigation, while potentially improving accuracy. In this human cadaver study, we evaluated a developed AR navigation approach for placement of zygomatic implants after total maxillectomy.

Methods

The developed AR navigation interface connects a commercial navigation system with the Microsoft HoloLens. AR navigated surgery was performed to place 20 zygomatic implants using five human cadaver skulls after total maxillectomy. To determine accuracy, postoperative scans were virtually matched with preoperative three-dimensional virtual surgical planning, and distances in mm from entry-exit points and angular deviations were calculated as outcome measures. Results were compared with a previously conducted study in which zygomatic implants were positioned with 3D printed surgical guides.

Results

The mean entry point deviation was 2.43 ± 1.33 mm and a 3D angle deviation of 5.80 ± 4.12° (range 1.39-19.16°). The mean exit point deviation was 3.28 mm (±2.17). The abutment height deviation was on average 2.20 ± 1.35 mm. The accuracy of the abutment in the occlusal plane was 4.13 ± 2.53 mm. Surgical guides perform significantly better for the entry-point (P = 0.012) and 3D angle (P = 0.05); however, there is no significant difference in accuracy for the exit-point (P = 0.143) when using 3D printed drill guides or AR navigated surgery.

Conclusion

Despite the higher precision of surgical guides, AR navigation demonstrated acceptable accuracy, with potential for improvement and specialized applications. The study highlights the feasibility of AR navigation for zygomatic implant placement, offering an alternative to conventional methods.

Comparison of robotic system and dynamic navigation for zygomatic implant placement: An in vitro study

OBJECTIVES

To compare the accuracy of robotic and dynamic navigation systems in assisting zygomatic implant (ZI) using an in vitro model experiment.

METHODS

Preoperative cone-beam computed tomography (CBCT) images of patients who underwent ZI treatment between 2011 and 2023 were collected from local databases. Corresponding three-dimensional resin models were printed and assigned to two groups: the robotic and dynamic navigation system groups. Following preoperative plans, ZIs were placed in the models with the assistance of either a robotic or dynamic navigation system. Deviations in the in vitro navigation surgery were measured and compared between the groups.

RESULTS

A total of 110 ZIs were placed in 56 models, with 55 ZIs in each group. No significant differences were observed in entry and angle deviations between the groups (p>0.05). However, the exit deviation in the robotic system group (2.39±1.24 mm) was larger than that in the dynamic navigation group (1.83±1.25 mm) (p<0.05). On the exit side, the Z-axis deviation in the robotic group (left: -0.28±1.43 mm, right: -0.21±1.30 mm) was smaller than that in the dynamic navigation group (left: 0.76±1.11 mm, right: 0.85±1.52 mm) (p<0.05), while no significant differences were found in X- and Y-axis deviations (p>0.05).

CONCLUSIONS

Compared with the dynamic navigation system, the robotic system can effectively prevent ZI overextension. However, its accuracy on the exit side is slightly lower than that of the dynamic navigation system.

CLINICAL SIGNIFICANCE

This preliminary in vitro study showed that the accuracy of the robotic system was slightly inferior to that of the dynamic navigation system in terms of exit deviation when used in ZI placement. Further clinical studies are required to confirm these findings.

NextLens-The Next Generation of Surgical Navigation: Proof of Concept of an Augmented Reality System for Surgical Navigation

Objective  The aim of this work was the development of an augmented reality system including the functionality of conventional surgical navigation systems. Methods  An application software for the Augmented Reality System HoloLens 2 from Microsoft was developed. It detects the position of the patient as well as position of surgical instruments in real time and displays it within the two-dimensional (2D) magnetic resonance imaging or computed tomography (CT) images. The surgical pointer instrument, including a pattern that is recognized by the HoloLens 2 sensors, was created with three-dimensional (3D) printing. The technical concept was demonstrated at a cadaver skull to identify anatomical landmarks. Results  With the help of the HoloLens 2 and its sensors, the real-time position of the surgical pointer instrument could be shown. The position of the 3D-printed pointer with colored pattern could be recognized within 2D-CT images when stationary and in motion at a cadaver skull. Feasibility could be demonstrated for the clinical application of transsphenoidal pituitary surgery. Conclusion  The HoloLens 2 has a high potential for use as a surgical navigation system. With subsequent studies, a further accuracy evaluation will be performed receiving valid data for comparison with conventional surgical navigation systems. In addition to transsphenoidal pituitary surgery, it could be also applied for other surgical disciplines.

A hybrid robotic system for zygomatic implant placement based on mixed reality navigation

BACKGROUNDS

Zygomatic implant (ZI) placement surgery is a viable surgical option for patients with severe maxillary atrophy and insufficient residual maxillary bone. Still, it is difficult and risky due to the long path of ZI placement and the narrow field of vision. Dynamic navigation is a superior solution, but it presents challenges such as requiring operators to have advanced skills and experience. Moreover, the precision and stability of manual implantation remain inadequate. These issues are anticipated to be addressed by implementing robot-assisted surgery and achieved by introducing a mixed reality (MR) navigation-guided hybrid robotic system for ZI placement surgery.

METHODS

This study utilized a hybrid robotic system to perform the ZI placement surgery. Our first step was to reconstruct a virtual 3D model from preoperative cone-beam CT (CBCT) images. We proposed a series of algorithms based on coordinate transformation, which includes image-phantom registration, HoloLens-tracker registration, drill-phantom calibration, and robot-implant calibration, to unify all objects within the same coordinate system. These algorithms enable real-time tracking of the surgical drill's position and orientation relative to the patient phantom. Subsequently, the surgical drill is directed to the entry position, and the planned implantation paths are superimposed on the patient phantom using HoloLens 2 for visualization. Finally, the hybrid robot system performs the processed of drilling, expansion, and placement of ZIs under the guidance of the MR navigation system.

RESULTS

Phantom experiments of ZI placement were conducted using 10 patient phantoms, with a total of 40 ZIs inserted. Out of these, 20 were manually implanted, and the remaining 20 were robotically implanted. Comparisons between the actual implanted ZI paths and the preoperatively planned ZI paths showed that our MR navigation-guided hybrid robotic system achieved a coronal deviation of 0.887 ± 0.213 mm, an apical deviation of 1.201 ± 0.318 mm, and an angular deviation of 3.468 ± 0.339° This demonstrates significantly better accuracy and stability than manual implantation.

CONCLUSION

Our proposed hybrid robotic system enables automated ZI placement surgery guided by MR navigation, achieving greater accuracy and stability compared to manual operations in phantom experiments. Furthermore, this system is expected to apply to animal and cadaveric experiments, to get a good ready for clinical studies.

Long-term survival and complications of Quad Zygoma Protocol with Anatomy-Guided Approach in severely atrophic maxilla: A retrospective follow-up analysis of up to 17 years

INTRODUCTION

The objective of the study was to provide long-term clinical outcomes and complications in the severely atrophic edentulous maxillae treated by means of the quad zygoma protocol (QZP) using the Anatomy-Guided Approach (AGA).

METHODS

This was a retrospective cohort study of all consecutive patients with severely atrophic edentulous maxilla and insufficient bone height and width in the anterior and posterior regions bilaterally, who underwent rehabilitation with the QZP between May 2006 and December 2021. All patients were followed for at least 1 year. All zygomatic implants (ZIs) were placed by the same surgeon. The primary endpoint of the study was the implant survival rate. Secondary endpoints were implant success rate, prosthesis success rate, complications, and Oral Health-Related Quality of Life using the OHIP-14 questionnaire.

RESULTS

A total of 56 patients (men 16, women 40) with 224 ZIs (Nobel Biocare, n = 204; Straumann, n = 16; Southern Implant, n = 4) placement were included with a mean follow-up period 8.8 ± 3.9 years (range, 1.2-17.0). The survival (success) rate was 97.7%. Five ZIs in four patients failed. The mean time between implant placement and failure was 8.6 years (range, 0.5-13.3). All patients received immediate loading with acrylic prosthesis. The successful rates for the definitive prosthesis were 98.2%. Forty-two patients received posterior cantilever for rehabilitation of fixed definitive prosthesis. Local orofacial inflammation (35.7%) and Sinusitis (12.5%) were the most common complications, occurring at a mean follow-up of 10.0 (range, 4.2-14.9) and 10.3 (range, 4.3-16.2) years, respectively. In 48 patients, the mean score of the OHIP-14 questionnaire was 1.7 ± 2.6 with the follow-up period of 9.0 ± 4.1 years.

CONCLUSIONS

The rehabilitation of severely atrophic edentulous maxilla using the QZP has shown a predictable and high survival rate in the long term. The implementation of an immediate loading protocol offers potential benefits in stabilizing ZIs with cross-arch stabilization. Moreover, the use of a posterior cantilever in reconstruction can effectively establish functional occlusion through well-distributed ZIs, eliminating the need for additional implant placement.

Accuracy of 3 calibration methods of computer-assisted dynamic navigation for implant placement: An in vitro study

STATEMENT OF PROBLEM

Dynamic navigation for implant placement has been reported to be more accurate than freehand surgery. However, the accuracy of the calibration methods used for navigation in partially edentulous individuals with distal extensions remains unknown.

PURPOSE

The purpose of this in vitro study on dental models was to evaluate the accuracy of 3 calibration methods of dynamic navigation for implant placement in the distal extension of partially edentulous arches.

MATERIAL AND METHODS

Eleven standardized polyurethane mandibular models with distal extensions were prepared. The left first molar, second molar, and second premolar from each model (33 tooth sites) were randomly assigned to 1 of the 3 calibration methods: U-shaped tube embedded with radiopaque markers, anatomic tooth cusps, and bone markers with the random number table method. Preoperative and postoperative cone beam computed tomography images were obtained for deviation analyses. The primary outcomes were 3-dimensional (3D) deviation at the implant platform and apex and angular deviation. Differences among the test groups were analyzed by using a 1-way analysis of variance (ANOVA) and the least significant difference (LSD) post hoc test (α=.05).

RESULTS

The mean ±standard deviation 3D deviations were 0.78 ±0.34, 1.86 ±0.91, and 1.44 ±0.57 mm at the implant platform and 0.79 ±0.35, 2.19 ±1.01, and 1.49 ±0.50 mm at the apex in the U-shaped tube, tooth cusp, and bone marker groups, respectively. The 3D deviations at the implant platform and apex were significantly different among the groups (P<.01). The angular deviation was 1.36 ±0.54, 2.95 ±2.07, and 2.92 ±2.45 degrees, with no significant differences among the groups (P=.092).

CONCLUSIONS

In the dynamic navigation of implant placement in the distal extension of partially edentulous arches, the U-shaped tube calibration with radiopaque markers was more accurate than the anatomic tooth cusp or bone marker calibration.

Accuracy and efficiency of a calibration approach in dynamic navigation for implant placement: An in vitro study

Background/purpose

Computer-assisted dynamic navigation surgery could provide accurate implant placement. However, its low efficiency was always criticized by dental surgeons. The purpose of this study was to evaluate the accuracy and efficiency of a calibration approach with reflective wafers in dynamic navigation for implant placement.

Materials and methods

Eighty implants were placed in the standardized polyurethane mandibular models under dynamic navigation and divided into 2 groups according to the calibration methods (n = 40). The U-shaped tube (UT) group used a prefabricated U-shaped tube embedded with radiopaque markers. The reflective wafers (RW) group used a fixation with 3 round reflective wafers as markers. Postoperative cone beam computed tomography images were obtained for implants deviation analyses. The calibration time was used to evaluate the efficiency of the 2 methods.

Results

Significant differences were found in the trueness and efficiency between the 2 groups (P < 0.05). The 3D deviations at the implant platform and apex were smaller in UT group (0.89 ± 0.28 and 0.79 ± 0.30 mm, respectively) than in the RW group (0.99 ± 0.28 and 0.98 ± 0.30 mm, respectively). The angular deviation was larger in the UT group (2.16 ± 1.12°) than in the RW group (1.53 ± 0.88°). The calibration approach of RW group was more efficient than the UT group (2.05 ± 0.55 and 7.50 ± 0.71 min, respectively).

Conclusion

The calibration method of RW improved the efficiency significantly and achieved equivalent trueness with UT for dynamic navigation during implant placement.

Stepwise osteotomy protocol for zygomatic implant placement under navigation in patients with extra-sinus trajectory

This technical note describes a stepwise osteotomy for zygomatic implant placement with an extra-sinus trajectory under navigation using virtual markers for registration. The stepwise osteotomy protocol divides the trajectory of the zygomatic implant osteotomy into three consecutive co-axial components. The aim is to achieve better control of the osteotomy under navigation and to minimize or eliminate any intermittent free-hand drilling. The stepwise osteotomy protocol facilitates the use of shorter drills to finish the zygomatic implant osteotomy at the entry location before switching back to the long drill to complete the whole osteotomy. This protocol has been applied in a patient and the preliminary result is promising. However, the clinical effectiveness of this approach requires further investigation in prospective clinical studies.

Feasibility and accuracy of a task-autonomous robot for zygomatic implant placement

STATEMENT OF PROBLEM

Zygomatic implants (ZIs) should be placed accurately as planned preoperatively to minimize complications and maximize the use of the remaining bone. Current digital techniques such as static guides and dynamic navigation are affected by human error; therefore, new techniques are required to improve the accuracy of ZI placement.

PURPOSE

The purpose of this clinical study was to assess the feasibility and accuracy of a task-autonomous robot for ZI placement.

MATERIAL AND METHODS

Patients indicated for ZI placement were enrolled, and an appropriate surgical positioning piece was selected based on the presence of natural teeth in the maxilla. Preoperative cone beam computed tomography (CBCT) scanning was performed with the surgical positioning piece, and virtual implant design and socket preparation procedures were initiated. Implant socket preparation and placement were automatically performed by the robot according to the preoperative plan under the supervision of the surgeon. Postoperative CBCT scanning was performed to evaluate deviations between the virtual and actual implants. All quantitative data were expressed as standardized descriptive statistics (mean, standard deviation, minimum, maximum, and 95% confidence interval [CI]). The Shapiro-Wilk test was used to assess the normal distribution of all variables (α=.05).

RESULTS

Six participants were enrolled, and 8 ZIs were inserted. No intraoperative or postoperative complications were observed. Robotic ZI placement showed a global coronal deviation of 0.97 mm (95% CI: 0.55 to 1.39 mm), a global apical deviation of 1.27 mm (95% CI: 0.71 to 1.83 mm), and an angular deviation of 1.48 degrees (95% CI: 0.97 to 2.00 degrees).

CONCLUSIONS

Task-autonomous robots can be used for ZI placement with satisfactory accuracy. Robotic ZI surgery can be an alternative to static guidance and dynamic navigation to improve the accuracy of implant placement.

Clinical efficacy of computer-assisted zygomatic implant surgery: A systematic scoping review

STATEMENT OF PROBLEM

Digital technology can improve the success of zygomatic implant (ZI) surgery. However, the reliability and efficacy of computer-assisted zygomatic implant surgery (CAZIS) need further analysis.

PURPOSE

The purpose of this scoping review was to provide an overview of the placement accuracy, implant survival, and complications of CAZIS.

MATERIAL AND METHODS

A systematic search of English and Mandarin Chinese publications up to May 2023 was conducted in PubMed, Web of Science, Embase, and Wanfang database. The nonpeer-reviewed literature was searched in the trial register (clinicaltrials.gov). Clinical studies and cadaver studies on CAZIS were included. After data extraction and collection, the findings were critically reviewed, analyzed, interpreted, and discussed.

RESULTS

Forty-one studies met the inclusion criteria. After excluding publications with duplicate data, retaining the most recent, 28 articles were included in this scoping review. Of these, 18 were on static computer-assisted zygomatic implant surgery (sCAZIS), 8 on dynamic computer-assisted zygomatic implant surgery (dCAZIS), and 2 on robot-assisted zygomatic implant surgery (rAZIS). Excluding the outliers, the mean deviations of ZIs in the sCAZIS group (with 8 articles reporting implant placement accuracy, 183 ZIs involved) were: 1.15 ±1.37 mm (coronal deviation), 2.29 ±1.95 mm (apical deviation), and 3.32 ±3.36 degrees (angular deviation). The mean deviations of dCAZIS (3 articles, 251 ZIs) were: 1.60 ±0.74 mm (coronal), 2.27 ±1.05 mm (apical), and 2.89 ±1.69 degrees (angular). The mean deviations of rAZIS (2 articles, 5 ZIs) were: 0.82 ±0.21 mm (coronal), 1.25 ±0.52 mm (apical), and 1.46 ±0.35 degrees (angular). Among the CAZIS reported in the literature, the implant survival rate was high (96.3% for sCAZIS, 98.2% for dCAZIS, and 100% for rAZIS, specified in 14 of 21 clinical studies). The incidence of complications was low, but, because of the few relevant studies (4/21 specified), valid conclusions regarding complications could not be drawn.

CONCLUSIONS

CAZIS has demonstrated clinical efficacy with high implant survival rates and placement accuracy. Of the 3 guided approaches, rAZIS showed the smallest 3-dimensional deviation.

Effect of a dynamic navigation device on the accuracy of implant placement in the completely edentulous mandible: An in vitro study

STATEMENT OF PROBLEM

A less invasive and more convenient workflow is needed for dynamic navigation-guided implant surgery for the edentulous arch.

PURPOSE

The purpose of this in vitro study was to evaluate the accuracy of a novel dynamic navigation device developed for the completely edentulous mandible.

MATERIAL AND METHODS

Two temporary 1-piece mini-implants were placed in the anterior region of a completely edentulous mandibular model for fixation of the navigation device. A total of 40 implants were inserted in 10 completely edentulous mandibular models with the aid of the dynamic navigation device. The accuracy of placement was determined by overlapping the preoperative plan with the postoperative cone beam computed tomography (CBCT) scans. The difference in the accuracy at different implant positions was compared by MANOVA and Bonferroni-corrected ANOVAs. The difference in accuracy between implants #1-20 and #21-40 was assessed for learning progression.

RESULTS

The deviation of the implants (mean ±standard deviation) was 1.14 ±0.50 mm at the entry point and 1.29 ±0.48 mm at the apex. The mean ±standard deviation angular deviation was 3.02 ±1.32 degrees. No significant difference was seen between the planned and the placed deviation among the 4 implant positions. After repeated placement with this dynamic approach, implant accuracy at the entry (P=.001) and apex (P=.017) improved significantly.

CONCLUSIONS

The navigation device achieved acceptable implant placement accuracy in the edentulous mandible. Deviations between the planned and placed locations were not affected by different implant positions. After repeated operations with this dynamic approach, accuracy at the entry and apex improved significantly.

Dynamic navigation for zygomatic implant placement: A randomized clinical study comparing the flapless versus the conventional approach

OBJECTIVES

The assessment of the accuracy of flapless placement of zygomatic implants in edentulous maxilla using dynamic navigation.

METHODS

A randomized controlled trial was carried out on 20 patients. Patients were randomized into two groups, the flapless (Group 1; n=10) and the conventional (Group 2; n=10). In each case two zygomatic implants were inserted under local anaesthesia, one on the right and one on the left side guided by a dynamic navigation system. The surgical procedure was identical in the two groups except for the reflection of the mucoperiosteal flap which was eliminated in the flapless cases. Postoperative CBCT scans were used to assess the accuracy of the placement of zygomatic implants.

RESULTS

Osseointegration was achieved for all the implants, except one case in the flapless group. Statistically significant differences in the accuracy of the position of the zygomatic implants was found between the flapless and the conventional groups, measured at the apex and the entry points of the implants (p < 0.01). The average apical and coronal deviations were 5 mm and 3 mm, respectively; the angular deviation was 6°, and 2 mm vertical apical disparity was detected between the planned and the achieved surgical position. Perforation of the Schneiderian membrane was noted in three cases, one in flapless group and two in the conventional group.

CONCLUSIONS

Flapless placement of zygomatic implants guided by dynamic navigation offered satisfactory safety and accuracy.

CLINICAL SIGNIFICANCE

This is the first clinical trial to prove the feasibility and accuracy of flapless placement of zygomatic implant with minimal morbidity. The study highlights the innovative reflection of the Schneiderian membrane under guided surgical navigation. The procedure can be performed under local anaesthesia, which offers clinical advantages. Adequate training on the use of dynamic navigation is mandatory before its use in clinical cases.

Accuracy of a Computer-Aided Dynamic Navigation System in the Placement of Zygomatic Dental Implants: An In Vitro Study

The objective of this in vitro study was to evaluate and compare the accuracy of zygomatic dental implant (ZI) placement carried out using a dynamic navigation system. Materials and Methods: Forty (40) ZIs were randomly distributed into one of two study groups: (A) ZI placement via a computer-aided dynamic navigation system (n = 20) (navigation implant (NI)); and (B) ZI placement using a conventional free-hand technique (n = 20) (free-hand implant (FHI)). A cone-beam computed tomography (CBCT) scan of the existing situation was performed preoperatively to plan the surgical approach for the computer-aided study group. Four zygomatic dental implants were placed in anatomically based polyurethane models (n = 10) manufactured by stereolithography, and a postoperative CBCT scan was performed. Subsequently, the preoperative planning and postoperative CBCT scans were added to dental implant software to analyze the coronal entry point, apical end point, and angular deviations. Results were analyzed using the Student’s t-test. Results: The results showed statistically significant differences in the apical end-point deviations between FHI and NI (p = 0.0018); however, no statistically significant differences were shown in the coronal entry point (p = 0.2617) or in the angular deviations (p = 0.3132). Furthermore, ZIs placed in the posterior region showed more deviations than the anterior region at the coronal entry point, apical end point, and angular level. Conclusions: The conventional free-hand technique enabled more accurate placement of ZIs than the computer-assisted surgical technique. In addition, placement of ZIs in the anterior region was more accurate than that in the posterior region.

Reliability and accuracy of dynamic navigation for zygomatic implant placement

Objectives

To assess the accuracy of a real‐time dynamic navigation system applied in zygomatic implant (ZI) surgery and summarize device‐related negative events and their management.

Material and methods

Patients who presented with severely maxillary atrophy or maxillary defects and received dynamic navigation‐supported ZI surgery were included. The deviations of entry, exit, and angle were measured after image data fusion. A linear mixed‐effects model was used. Statistical significance was defined as p < .05. Device‐related negative events and their management were also recorded and analyzed.

Results

Two hundred and thirty‐one zygomatic implants (ZIs) with navigation‐guided placement were planned in 74 consecutive patients between Jan 2015 and Aug 2020. Among them, 71 patients with 221 ZIs received navigation‐guided surgery finally. The deviations in entry, exit, and angle were 1.57 ± 0.71 mm, 2.1 ± 0.94 mm and 2.68 ± 1.25 degrees, respectively. Significant differences were found in entry and exit deviation according to the number of ZIs in the zygomata (p = .03 and .00, respectively). Patients with atrophic maxillary or maxillary defects showed a significant difference in exit deviation (p = .01). A total of 28 device‐related negative events occurred, and one resulted in 2 ZI failures due to implant malposition. The overall survival rate of ZIs was 98.64%, and the mean follow‐up time was 24.11 months (Standard Deviation [SD]: 12.62).

Conclusions

The navigation‐supported ZI implantation is an accurate and reliable surgical approach. However, relevant technical negative events in the navigation process are worthy of attention.

A novel guided zygomatic implant surgery system compared to free hand: a human cadaver study on accuracy

OBJECTIVES

The aim of this human cadaver study was to compare the accuracy of guided versus free-hand zygomatic implant placement. For the guided implant placement laser sintered titanium templates were used.

METHODS

Forty zygomatic implants were placed in ten cadavers heads. For each case two implants were inserted using the guided protocol(Ezgoma guide, Noris Medical, Israel) and the related surgical kit and the other two by using a free hand approach. Post-operative computed tomography (CT) scans were carried out to assess the deviations between planned and inserted implants. The accuracy was measured by overlaying the post-operative Ct scan (with the final position of the achieved implants)with the pre-operative CT scan (with the planned implants).

RESULTS

The difference of the mean between planned and placed zygomatic implants by using surgical guides or free hand were statistically significant for all the variables evaluated: angular deviation (1.19°±0.40° and 4.92°±1.71° p<0.001), linear distance deviation at coronal point (0.88 mm±0.33 mm and 2.04 mm±0.56 mm p<0.001), at apical point (0.79 mm±0.23 mm and 3.23 mm±1.43 mm p<0.001)and at apical depth (0.35 mm±0.25 mm and 1.02 mm±0.61 mm p<0.001).

CONCLUSIONS

The proposed surgical guided system exhibited a higher accuracy for all the investigated variables compared to the free hand technique.

A single-arm clinical trial investigating the feasibility of the zygomatic implant quad approach for Cawood and Howell Class 4 edentulous maxilla: An option for immediate loading

INTRODUCTION

The traditional way to treat maxillary edentulous Cawood and Howell Class 4 (CH4) patients who exhibit the knife-edge ridge form of edentulous jaws that are adequate in height and inadequate in width is extensive autologous bone grafting for conventional implant placement.

PURPOSE

To evaluate the feasibility of the zygomatic implant (ZI) quad approach in edentulous CH4 patients who presented a knife-edge ridge form in the anterior maxilla for immediate loading.

MATERIAL AND METHODS

Eligible patients with maxillary CH4 edentulism treated with the ZI quad approach were enrolled. Bone reduction and implant placement were performed under the guidance of a navigation system according to preoperative planning. The outcome variable was the implant survival rate, and additional variables were the ratio of immediate loading, complications and the relationship of the zygomatic implant path to the sinus wall. Statistical analysis was performed with the SAS statistical package.

RESULTS

Fifteen patients (3 men, 12 women; age range, 19-71 years; average age 47.2 years) eligible for the study received the ZI quad approach from January 2017 through January 2020. All ZIs achieved osseointegration, with no implant loss after early healing and a mean follow-up of 17.2 ± 6.2 months. Thirteen of 15 patients (86.7%) received immediate loading. No critical anatomic structure injuries occurred during surgery. Most mesially placed implants (23/30, 76.6%) presented ZAGA 2 and 3, and most distally placed implants were distributed in ZAGA 0 (20/30, 66.7%).

DISCUSSION

In terms of realizing immediate loading in CH4 patients with a knife-edge ridge form in the anterior maxilla, quad approaches have advantages over other grafting methods. At the same time, it seems the survival rate of zygomatic implants is comparable with that of other indications. With the limitations of this study, the quad approach might be a feasible option to realize edentulous maxillary reconstruction and to make immediate loading possible.

A Novel Guided Zygomatic and Pterygoid Implant Surgery System: A Human Cadaver Study on Accuracy

The aim of this human cadaver study was to assess the accuracy of zygomatic/pterygoid implant placement using custom-made bone-supported laser sintered titanium templates. For this purpose, pre-surgical planning was done on computed tomography scans of each cadaver. Surgical guides were printed using direct metal laser sintering technology. Four zygomatic and two pterygoid implants were inserted in each case using the guided protocol and related tools. Post-operative computed tomography (CT) scans were obtained to evaluate deviations between the planned and inserted implants. Accuracy was measured by overlaying the real position in the post-operative CT on the virtual presurgical placement of the implant in a CT image. Descriptive and bivariate analyses of the data were performed. As a result, a total of 40 zygomatic and 20 pterygoid implants were inserted in 10 cadavers. The mean deviations between the planned and the placed zygomatic and pterygoid implants were respectively (mean ± SD): 1.69° ± 1.12° and 4.15° ± 3.53° for angular deviation. Linear distance deviations: 0.93 mm ± 1.23 mm and 1.35 mm ± 1.45 mm at platform depth, 1.35 mm ± 0.78 mm and 1.81 mm ± 1.47 mm at apical plane, 1.07 mm ± 1.47 mm and 1.22 mm ± 1.44 mm for apical depth. In conclusion, the surgical guide system showed accuracy for all the variables studied and allowed acceptable and accurate implant placement regardless of the case complexity.

Dynamic-Assisted Navigational System in Zygomatic Implant Surgery: A Qualitative and Quantitative Systematic Review of Current Clinical and Cadaver Studies

PURPOSE

The goal of this systematic review is to assess the accuracy and complications (including failure) of dynamic navigation in placing zygomatic implants.

METHODS

PubMed, Cochrane Library (CENTRAL), trial register (clinicaltrial.gov), and Google Scholar were searched systematically up to May 2020. In addition, the reference lists of included systematic reviews were hand searched. The New Castle Ottawa and Joanna Briggs Institute Critical Appraisal Checklist for Case Reports were used for quality assessment.

RESULTS

Ninety-four studies were assessed, and finally, 12 articles were included. According to Joanna Briggs Institute tool, the mean score of case reports (±standard deviation) was 6.4 (range, 5/9 to 8/9) and the mean score of observational studies (±standard deviation) was 5.66 (range, 5/9 to 7/9) as measured by New Castle Ottawa tool. Included materials pointed out that higher accuracy and drastic cut down on the risk of perioperative/postoperative complications were reported by using the dynamic navigation system compared with freehand implant placement.

CONCLUSIONS

Application of dynamic navigation systems is a reliable technology for zygomatic implant placement, especially in difficult cases with a history of maxillary deficiency. Evidence of reliability and accuracy of dynamic navigation technique in multicenter large randomized and prospective controlled studies is still lacking.

Comparison of the accuracy of dental implant placement using static and dynamic computer-assisted systems: an in vitro study

OBJECTIVES

The study aimed to compare the accuracy of implant placement between static and dynamic computer-assisted systems (CAS) in a partially edentulous mandible model.

MATERIALS & METHODS

A total of 80 implants was placed in mandible models. The implants were placed using either static or dynamic computer-assisted system. Deviations of implant hex, apex and angulation were measured between preoperative planning and postoperative CBCT in planning software.

RESULTS

The mean deviations of implant hex, apex and angulation in static CAS group were 1.15 ± 0.34 mm, 1.37 ± 0.38 mm and 2.60 ± 1.11 degree, while in dynamic CAS group were 0.40 ± 0.41 mm, 0.34 ± 0.33 mm and 0.97 ± 1.21 degree, respectively. Implant placement with dynamic CAS showed less deviations of shoulder, apex and angulation than with static CAS significantly.

CONCLUSIONS

The implant accuracy using CAS system could be influenced by the guiding technique.

Dynamic Navigation for Zygomatic Implants: A Case Report about a Protocol with Intraoral Anchored Reference Tool and an Up-To-Date Review of the Available Protocols

Dynamic Navigation is a computer-aided technology that allows the surgeon to track the grip instruments while preparing the implant site in real time based on radiological anatomy and accurate pre-operative planning. The support of this technology to the zygoma implant placement aims to reduce the risks and the errors associated with this complex surgical and prosthetic treatment. Various navigation systems are available to clinicians currently, distinguished by handling, reliability, and the associated economic and biological benefits and disadvantages. The present paper reports on the different protocols of dynamic navigations following a standard workflow in correlation with zygomatic implant supported rehabilitations and describes a case of maxillary atrophy successfully resolved with this technology. An innovative and minimally invasive dynamic navigation system, with the use of an intraoral anchored trust marker plate and a patient reference tool, has been adopted to support the accurate insertion of four zygomatic implants, which rapidly resolved maxillary atrophy from a 75-year-old male system. This approach provided an optimal implant placement accuracy reducing surgical invasiveness.

Comparative accuracy of cone-beam CT and conventional multislice computed tomography for real-time navigation in zygomatic implant surgery

BACKGROUND

Cone-beam computed tomography (CBCT) and conventional multislice CT (MSCT) are both used in zygomatic implant navigation surgery but the superiority of one technique versus the other remains unclear.

PURPOSE

This study compared the accuracy of CBCT and MSCT in zygomatic implant navigation surgery by calculating the deviations of implants.

MATERIAL AND METHODS

Patients with severely atrophic maxillae were classified into two groups according to the use of CBCT- or MSCT-guided navigation system. The entry and apical distance deviation, and the angle deviation of zygomatic implants were measured on fused operation images. A linear effect model was used for analysis, with statistical significance set at P < .05.

RESULTS

A total of 72 zygomatic implants were inserted as planned in 23 patients. The comparison of deviations in CBCT and MSCT groups showed a mean (± SD) entry deviation of 1.69 ± 0.59 mm vs 2.04 ± 0.78 mm (P = .146), apical deviation of 2 ± 0.68 mm vs 2.55 ± 0.85 (P < .001), and angle deviation of 2.32 ± 1.02° vs 3.23 ± 1.21° (P = .038).

CONCLUSION

Real-time zygomatic implant navigation surgery with CBCT may result in higher values for accuracy than MSCT.

Computer-Aided Rehabilitation Supported by Zygomatic Implants: A Cohort Study Comparing Atrophic with Oncologic Patients after Five Years of Follow-Up

The aim of this study was to evaluate the survival and clinical success rate, complications, and patients’ quality of life after computer-aided rehabilitation supported by zygomatic implants in cases of severe maxillary atrophy (ten patients) and in bone defects in oncologic patients (ten patients). All patients underwent computer-aided planning and surgery. Seventy-three zygomatic implants were placed. The mean follow-up period was 39.9 months. Implant survival and clinical success rate, the effectiveness of planning the implant length, biological and prosthetic complications, and the quality of life were evaluated. The five-year implant survival rate for patients with maxillary atrophy and oncologic patients was 97.4% and 96.7%, respectively. The prosthetic survival rate was 100%. Two implant failures occurred in the first year. One implant failure was observed in each group. Minor biological and prosthetic complications occurred in both groups without significant differences. All complications were managed without affecting the treatment. The quality of life increased by 71.3% in the atrophic group and by 82.9% in the oncologic group. Zygomatic implant rehabilitation seems to be a reliable technique for patients with maxillary atrophy and for oncologic patients. The three-dimensional computer-aided approach allows the surgeon to plan the surgery and increase its predictability. Early prosthesis loading certainly allows for better functional outcomes.

Three-Dimensional Radiographic Evaluation of the Malar Bone Engagement Available for Ideal Zygomatic Implant Placement

Zygomatic implant rehabilitation is a challenging procedure that requires an accurate prosthetic and implant plan. The aim of this study was to evaluate the malar bone available for three-dimensional zygomatic implant placement on the possible trajectories exhibiting optimal occlusal emergence. After a preliminary analysis on 30 computed tomography (CT) scans of dentate patients to identify the ideal implant emergencies, we used 80 CT scans of edentulous patients to create two sagittal planes representing the possible trajectories of the anterior and posterior zygomatic implants. These planes were rotated clockwise on the ideal emergence points and three different hypothetical implant trajectories per zygoma were drawn for each slice. Then, the engageable malar bone and intra- and extra-sinus paths were measured. It was possible to identify the ideal implant emergences via anatomical landmarks with a high predictability. Significant differences were evident between males and females, between implants featuring anterior and those featuring posterior emergences, and between the different trajectories. The use of internal trajectories provided better bone engagement but required a higher intra-sinus path. A significant association was found between higher intra-sinus paths and lower crestal bone heights.

A novel extraoral registration method for a dynamic navigation system guiding zygomatic implant placement in patients with maxillectomy defects

Zygomatic implants (ZIs) are used for the oral rehabilitation of patients with maxillectomy defects as an alternative to extensive bone grafting surgeries. New technologies such as computer-assisted navigation systems can improve the accuracy and safety of ZI placement. The intraoral anchorage of fiducial markers necessary for navigation registration is not possible in the case of a severe maxillary defect and lack of residual bone. This technical note presents a novel extraoral registration method for a dynamic navigation system guiding ZI placement in patients with maxillectomy defects. Titanium microscrews were inserted in the mastoid process, supraorbital ridge, and posterior zygomatic arch as registration markers. The mean fiducial registration error (FRE) was 0.53 ± 0.20 and the deviations between the planned and placed ZIs were 1.56 ± 0.54 mm (entry point), 1.87 ± 0.63 mm (exit point), and 2.52 ± 0.84° (angulation). The study results indicate that the placement of fiducial markers at extraoral sites can be used as a registration technique to overcome anatomical limitations in patients after maxillectomy, with a clinically acceptable registration accuracy.

Pilot study of a surgical robot system for zygomatic implant placement

Zygomatic implant technology has been regarded as an alternative treatment to massive grafting surgery in the severe atrophic maxillary. Nowadays, the assistant method with a real-time surgical navigation has been applied to reduce the risks of zygomatic implant placement. However, the accuracy of the complex operation is highly dependent on the experience of the surgeon. In order to avoid disadvantages of traditional surgical navigation systems, a novel surgical robot system for the zygomatic implant placement has been designed and developed. Firstly, the drilling trajectory of the zygomatic implant placement is designed through the pre-operative planning system. Secondly, the real-time positions of the surgical instruments are constantly updated with the guidance of the optical tracker. Finally, through a coordinate transformation algorithm, the drilling performance can be conducted with the control of a six degree of freedom robot. In order to evaluate the accuracy of the robot, phantom experiments had been carried out. The angle, entry point and exit point deviation of the robotic system are 1.52 ± 0.58°, 0.79 ± 0.19 mm, and 1.49 ± 0.48 mm, respectively. Meanwhile, a comparison between the robotic and manual operation demonstrates that the use of the surgical robot system for the zygomatic implant placement can improve the accuracy of the operation.

A novel noise filtered and occlusion removal: navigational accuracy in augmented reality-based constructive jaw surgery

PURPOSE

Augmented reality-based constructive jaw surgery has been facing various limitations such as noise in real-time images, the navigational error of implants and jaw, image overlay error, and occlusion handling which have limited the implementation of augmented reality (AR) in corrective jaw surgery. This research aimed to improve the navigational accuracy, through noise and occlusion removal, during positioning of an implant in relation to the jaw bone to be cut or drilled.

METHOD

The proposed system consists of a weighting-based de-noising filter and depth mapping-based occlusion removal for removing any occluded object such as surgical tools, the surgeon's body parts, and blood.

RESULTS

The maxillary (upper jaw) and mandibular (lower jaw) jaw bone sample results show that the proposed method can achieve the image overlay error (video accuracy) of 0.23~0.35 mm and processing time of 8-12 frames per second compared to 0.35~0.45 mm and 6-11 frames per second by the existing best system.

CONCLUSION

The proposed system concentrates on removing the noise from the real-time video frame and the occlusion. Thus, the acceptable range of accuracy and the processing time are provided by this study for surgeons for carrying out a smooth surgical flow.

Long-term Schneiderian membrane thickness changes following zygomatic implant placement: A retrospective radiographic analysis using cone beam computed tomography

OBJECTIVES

The purpose of this retrospective study was to evaluate the long-term changes in the thickness of Schneiderian membranes after zygomatic implant placement using cone beam computed tomography (CBCT).

MATERIAL AND METHODS

Twenty-five consecutive patients were included in this study. All the patients underwent bilateral zygomatic implant placement. Schneiderian membrane thickness (SMT) in 49 maxillary sinuses (one sinus was not included because of early loss of the zygomatic implants) was measured using CBCT before and at least 1 year after zygomatic implant placement. Ostium patency of each sinus was also evaluated and recorded.

RESULTS

In total, 84 zygomatic implants and 30 regular implants were placed in included patients. Two unilateral maxillary zygomatic implants in one patient were removed 2 months after implant placement. The SMT increased from 1.03 mm (inter-quartile range: 1.57 mm) to 1.33 mm (inter-quartile range: 1.98 mm) after a median follow-up time of 23.00 months (inter-quartile range: 14 months), and the difference was statistically significant. Before zygomatic implant insertion, 24.5% (12/49) of sinuses had SMT greater than 2 mm, whereas this value was 28.6% (14/49) after zygomatic implant placement. The percentage of sinuses observed with ostium patency also increased from 2.0% (1/49) to 12.2% (6/49).

CONCLUSIONS

Chronic Schneiderian membrane thickening could result from zygomatic implant insertion. Intensive postoperative care and clinical and radiographic monitoring are recommended after zygomatic implant placement.