Accuracy of drilling guides for transfer from three-dimensional CT-based planning to placement of zygoma implants in human cadavers

Hygienic maintenance in patients with maxillae atrophy and in oncological patients with maxillary resection rehabilitated with zygomatic implants: A nested monocentric prospective cohort study

OBJECTIVE

To assess peri-implant soft tissues condition, comparing clinical parameters of implants placed in patients with atrophic upper jaws and patients who underwent maxillary resection for oncological reasons.

BACKGROUND

Zygomatic implants (ZIs) in oncologic patients could be affected by more complications compared to implants placed in atrophic maxillae. The soft tissue condition is an essential requirement for implant success, but few studies have investigated this topic.

METHODS

A nested monocentric prospective parallel cohort (atrophic vs. oncological patients) study was performed. Clinical visits and professional hygiene sessions were performed every three months, and bleeding on probing (BOP), probing pocket depth (PPD), gingival index (GI), plaque index (PI) and implant mobility were recorded by a blind outcome assessor.

RESULTS

In total, 77 ZIs placed in 21 patients were evaluated: 54 (70.1%) ZIs were inserted in patients belonging to the atrophic cohort (PAM) and 23 (29.9%) ZIs in the oncologic cohort (OP). The probability of having BOP at the considered mean follow-up (27 months) was 24.8% (95% CI 19.0-31.9) for PAM and 22.9% (95% CI 15.1-33.9) OP. The mean PPD values were 2.78 ± 1.28 (range 1-8) in PAM and 2.91 ± 1.98 (range 0-10) in OP. None of the implants showed mobility. No associations between group belongingness and the entity of PPD, PI, GI and the risk of BOP were found, adjusting for the considered confounding factors (age, smoking and implant position).

CONCLUSIONS

Under a strict supportive hygiene therapy protocol ZIs in oncologic patients showed similar peri-implant tissue conditions to that of patients with maxillary atrophy.

Modified Technique to Rehabilitate American Society of Anesthesiology-III Patient, Through Flapless Procedure With Computed Tomography-Guided Surgery

PURPOSE

The aim was to evaluate the safety and effectiveness of a computed tomography-guided surgery implant placement with a flapless technique and immediate functional loading in an American Society of Anesthesiology-III patient.

METHODS

This technical note involved a 64-year-old American Society of Anesthesiology-III patient. Her hopeless teeth were extracted and a restorative evaluation was provided as a prosthetic reference. The surgical procedure was based on the flapless technique that let us to use local anesthesia. The authors used an All-on-4 concept restoration for maxilla and conventional fixed prosthesis procedures for jaw rehabilitation. The authors placed 4 tilted implants in the upper maxilla and 6 right implants in the jaw. Implants were loaded with a provisional prosthesis on the same day of surgery. Five months later, provisional restoration was removed; the authors placed into the ceramic crowns 2 Procera Implant Bridge (Nobel Biocare) frameworks, developed through computer-aided design/computer-aided manufacturing technology.

CONCLUSIONS

Computed tomography-guided surgery is a minimally invasive technique that allows, through a flapless approach, safer and more predictable procedures. In this technical note, the authors achieved accurate implant placement and precise fit of restoration with natural looking appearance; this patient-oriented-treatment led to a reduced healing time with better compliance.

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.

The Accuracy of Zygomatic Implant Placement Assisted by Dynamic Computer-Aided Surgery: A Systematic Review and Meta-Analysis

PURPOSE

The present systematic review aimed to investigate the accuracy of zygomatic implant (ZI) placement using dynamic computer-aided surgery (d-CAIS), static computer-aided surgery (s-CAIS), and a free-hand approach in patients with severe atrophic edentulous maxilla and/or deficient maxilla.

METHODS

Electronic and manual literature searches until May 2023 were performed in the PubMed/Medline, Scopus, Cochrane Library, and Web of Science databases. Clinical trials and cadaver studies were selected. The primary outcome was planned/placed deviation. Secondary outcomes were to evaluate the survival of ZI and surgical complications. Random-effects meta-analyses were conducted and meta-regression was utilized to compare fiducial registration amounts for d-CAIS and the different designs of s-CAIS.

RESULTS

A total of 14 studies with 511 ZIs were included (Nobel Biocare: 274, Southern Implant: 42, SIN Implant: 16, non-mentioned: 179). The pooled mean ZI deviations from the d-CAIS group were 1.81 mm (95% CI: 1.34-2.29) at the entry point and 2.95 mm (95% CI: 1.66-4.24) at the apex point, and angular deviations were 3.49 degrees (95% CI: 2.04-4.93). The pooled mean ZI deviations from the s-CAIS group were 1.19 mm (95% CI: 0.83-1.54) at the entry point and 1.80 mm (95% CI: 1.10-2.50) at the apex point, and angular deviations were 2.15 degrees (95% CI: 1.43-2.88). The pooled mean ZI deviations from the free-hand group were 2.04 mm (95% CI: 1.69-2.39) at the entry point and 3.23 mm (95% CI: 2.34-4.12) at the apex point, and angular deviations were 4.92 degrees (95% CI: 3.86-5.98). There was strong evidence of differences in the average entry, apex, and angular deviation between the navigation, surgical guide, and free-hand groups (p < 0.01). A significant inverse correlation was observed between the number of fiducial screws and the planned/placed deviation regarding entry, apex, and angular measurements.

CONCLUSION

Using d-CAIS and modified s-CAIS for ZI surgery has shown clinically acceptable outcomes regarding average entry, apex, and angular deviations. The maximal deviation values were predominantly observed in the conventional s-CAIS. Surgeons should be mindful of potential deviations and complications regardless of the decision making in different guide approaches.

Autonomous dental robotic surgery for zygomatic implants: A two-stage technique

Zygomatic implants (ZIs) can be a treatment option for patients with severe atrophy in the maxilla, but deviation during ZI placement could lead to serious complications. Surgical guides and dynamic navigation have been used to improve the accuracy of ZI placement, but both techniques are subject to human error. A 2-stage technique is described that enabled an autonomous dental robot to overcome mouth-opening restrictions for ZI placement. The technique enables the complete digitalization of ZI placement, further improving the accuracy of the drilling process.

Retrospective analysis of the predictability of using three-dimensional models for preoperative planning of the length of zygomatic implants

PURPOSE

This present study aimed to retrospectively evaluate the predictability of using three-dimensional models (TDMs) to plan the preoperative lengths of zygomatic implants (ZIs).

METHODS

The records of all patients that received such implants between March 2007 and March 2019 were evaluated. The ZI lengths predicted on the TDMs were compared to the lengths of the implants the patients received.

RESULTS

In total, the records of 74 patients were evaluated, of which 37 records met the criteria of inclusion, and were included in the study. Twenty-seven (73%) of the patients were female and 10 (27%) were male, ranging from 34 to 80 years of age, with the average age being 55.7 years. Seventeen (43.2%) of these patients were classified as ASA I and 21 (56.8%) as ASA II. A total of 142 ZIs were planned and installed in the time frame mentioned. Without distinguishing the region of the maxilla, the implants used were, on average, 1.1 mm larger in length than those initially planned.

CONCLUSION

Overall, the data indicates moderate agreement between the planned and surgical lengths of the ZIs and indicates that using TDMs is a predictable and reliable preoperative planning technique of the length of posterior ZIs.

Direct guided restorations from planning to definitive restoration: A clinical report

A direct composite resin placed by using digitally planned prototyped 3D guides and retained with a digitally guided fiberglass micropin was used to restore an extensively damaged maxillary left central incisor.

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.

Fully Guided Zygomatic Implant Surgery

INTRODUCTION

Rehabilitating a severely atrophic maxilla is a complex procedure. In case of severe resorption, zygomatic implants are indicated and loading of the implants at the end of the surgery is desirable. We present a new method by means of guided surgery for the placement of zygomatic implants, using specially designed metal templates that should be supported by bone.

METHODS

The treatment planning for completely guided prosthetic rehabilitation of the maxilla with zygomatic implants was digitally performed. A radiographic template was designed for the prosthetic treatment planning. A surgical template was used to replicate the digitally planned steps in vivo.

RESULTS

The procedure ended with the positioning of a custom-made temporary prosthesis. This method can reduce the surgery duration, simplify the procedure, and optimize the outcome. It requires equal cooperation among technicians, prosthodontists, and surgeons. Nineteen out of twenty patients included in the study presented successful implants and prosthesis at the moment of analysis.

CONCLUSIONS

The present approach addressed the needs for zygomatic-implant surgery. The surgical and prosthetic plan, position, emergence, the shape of the implants, the position of the temporary prosthesis, the inter-arch relationships, and surgical templates were designed in a completely virtual environment and performed by the surgeon on stereolithographic models beforehand. Consequently, the surgical procedure was considerably simplified.

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.

A zygomatic bone study using virtual dental implant planning software

This study evaluated the anatomical factors that influence the virtual planning of zygomatic implants by using cone beam computerized tomography (CBCT) scans. CBCT scans of 268 maxilla edentulous patients were transferred to a specialized implant planning software (Galaxis, Sirona) for the following measurements: maxillo-sinus concavity size (small, medium, and large), Zygoma width, implant insertion angle, implant length, and implant apical anchorage. Concavity sizes found were as follows: 34.95% small, 52.30% medium, and 7.35% large. The mean insertion angle was 43.2 degrees and the average implant apical anchorage was 9.1mm. The most frequent implant length was 40mm. Significant differences were found when the different types of concavities in relation to the installation angle, the distance of the apical portion of the implant in contact with the zygomatic bone and the lateral-lateral thickness of the zygomatic bone were compared (p<0.001). Medium-sized maxillary sinus concavity presented greater apical anchorage of the implant (9.7mm) and was the most frequent type (52.30%). The zygomatic bone is a viable site for zygomatic fixtures and the use of specialized implant planning software is an important tool to achieve predictable outcomes for zygomatic implants and allows good visualization of the implant-anatomical structures relation.

The Morpho-Functional Three-Dimensional Analysis for Zygomatic Implants: A Clinical Tool With Surgical Implications

ABSTRACT

Zygomatic implants (ZIs) have been used successfully for the rehabilitation of jaws with severe atrophy for the past 2 decades. The development of computed tomography, three-dimensional (3D) analysis software, and stereolithographic models has positively impacted the development of preoperative planning. This article describes the protocol developed by the Department of Oral and Maxillofacial Surgery of El Bosque University, Bogotá, Colombia, through 10 years of experience, for the installation of ZIs, covering from the times when the implants were placed through intraoperative guidance, until now, in which drilling guides developed by computer-aided design and computer-aided manufacturing are used, without neglecting in their design multiple factors that must be considered. To date, this protocol for the treatment of patients with atrophic jaws through ZIs includes a detailed clinical examination, in which variables such as bone and dental relationship between the jaws, oral opening and dynamic interaction between soft cervicofacial tissues are considered. It also includes a 3D computed tomography planning for the design and preparation of surgical guides whose insertion patterns must be executable during surgery. Together, clinical and imaging analysis converge in what it has been called morpho-functional 3D planning.

Combined bone- and mucosa-supported 3D-printed guide for sinus slot preparation and prosthetically driven zygomatic implant placement

The use of zygomatic implants to rehabilitate the severely atrophic maxilla has been well documented since first being introduced by Brånemark. Placement of zygomatic implants is technically complex, with catastrophic complications and numerous prosthetic challenges resulting from imprecise placement. The purpose of this report was to demonstrate a technique that allows transfer of the preoperatively planned sinus slot position to the surgical field by using cone beam computed tomography (CBCT) and an implant planning software program to fabricate a combined bone- and mucosa-supported 3D-printed surgical guide. This facilitates optimal zygomatic implant positioning and promotes favorable biomechanics with a predictable prosthetic outcome.

Dentomaxillofacial CBCT: Clinical Challenges for Indication-oriented Imaging

This critical review discusses the clinical challenges for patient-specific and indication-oriented dentomaxillofacial cone beam computed tomography (CBCT). Large variations among units and protocols may lead to variable degrees of diagnostic and three-dimensional model accuracy, impacting both specific diagnostic tasks and treatment planning. Particular indications, whether diagnostic or therapeutic, may give rise to very specific challenges with regard to CBCT unit and parameter setup, considering the required image quality, segmentation accuracy, and artifact level. Considering that dental materials are in the field of view needed for diagnosis or treatment planning, artifact expression is a dominant factor in proper CBCT selection. The heterogeneity of dental CBCT units and performances may highly impact the scientific results. Thus research findings cannot be simply generalized as published evidence, and a demonstrated clinical applicability for a specific indication should not be simply extrapolated from one CBCT unit to another.

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.

Quad Zygoma: Technique and Realities

Four zygomatic implants may be used in patients with severe maxillary atrophy for rehabilitation with a fixed or removable prosthesis. Immediate loading is also typically performed, providing patients with a less invasive and more efficient solution for rehabilitation. Options for immediate loading are presented. The indications, contraindications, procedure, and complications are reviewed. Appropriate treatment planning and work-up are highlighted, as they are required for success in conjunction with advanced surgical skill. Scientific evidence, although lacking in quantity, suggests that the quad zygoma approach offers a predictable solution for the challenge of severe maxillary atrophy; high implant survival rates are noted.

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.

Cone Beam Computed Tomography in Oral and Maxillofacial Surgery: An Evidence-Based Review

Cone Beam Computed Tomography (CBCT) is a valuable imaging technique in oral and maxillofacial surgery (OMS) that can help direct a surgeon’s approach to a variety of conditions. A 3-dimensional analysis of head and neck anatomy allows practitioners to plan appropriately, operate with confidence, and assess results post-operatively. CBCT imaging has clear indications and limitations. CBCT offers the clinician 3-dimensional and multi-planar views for a more accurate diagnosis and treatment without the financial burden and radiation exposure of conventional computed tomography (CT) scans. Furthermore, CBCT overcomes certain limitations of 2-dimensional imaging, such as distortion, magnification, and superimposition. However, CBCT lacks the detailed depiction of soft tissue conditions for evaluation of pathologic conditions, head and neck infections, and temporomandibular joint (TMJ) disc evaluation. This review evaluates the evidence-based research supporting the application of CBCT in the various fields of oral and maxillofacial surgery, including dentoalveolar surgery, dental implants, TMJ, orthognathic surgery, trauma, and pathology, and will assess the value of CBCT in pre-operative assessment, surgical planning, and post-operative analysis when applicable. Additionally, the significant limitations of CBCT and potential areas for future research will be discussed.

Reliability and accuracy of skin-supported surgical templates for computer-planned craniofacial implant placement, a comparison between surgical templates: With and without bony fixation

INTRODUCTION

The purpose is to determine the accuracy of guided implant placement in the orbital, nasal, and auricular region using computer-aided designed stereolithographic skin-supported surgical templates with and without bone fixation pins.

MATERIALS AND METHODS

Preoperatively, cone-beam CT (CBCT) and multiple detector computed tomography (MDCT) scans were acquired from 10 cadaver heads, followed by virtual planning of implants in the orbital margin, auricular region and nasal floor. Surgical skin-supported templates were digitally designed to allow flapless implant placement. Fixation pins were used for stabilization comprising half of all templates in predetermined bone areas. The accuracy of the surgical templates was validated by comparing the achieved implant location to its virtual planned implant position by calculating the linear and angular deviations.

RESULTS

Surgical templates with the use of bone fixation pins produced statistically significant greater implant deviations as compared to the non-fixated surgical templates.

CONCLUSION

The results of this study indicate that significant deviation has to be taken into account when placing cranio-maxillofacial implants using skin-supported surgical templates. Surprisingly, the use of bone-fixated pins worsened the accuracy.

Accuracy of computer-guided implant placement in anterior regions

STATEMENT OF PROBLEM

Implant placement in the anterior regions is often challenging because of limited space and bone volume availability.

PURPOSE

The purpose of this clinical study was to investigate the accuracy of computer-guided surgery with a long drill key to place implants in the anterior regions.

MATERIAL AND METHODS

Computer-guided implant surgery was performed for 32 participants requiring implants in anterior regions. The procedure involved using a 12-mm-long drill key to guide the 2.0-mm-diameter drill. Deviations between the planned and actual implant positions were evaluated by using cone beam computed tomography (CBCT) scans obtained before and after surgery. A t test was used for comparisons between the planned and placed implants and to determine the influence of the arch (maxilla/mandible) and time (immediate/delayed) on accuracy.

RESULTS

A total of 40 implants (20 implants in the maxilla and 20 implants in the mandible) were placed. The mean linear deviation was 0.46 mm (range, 0 to 1.15 mm) for the implant shoulder and 0.67 mm (range, 0.14 to 1.19 mm) for the implant apex. The mean angular deviation was 1.40 degrees (range, 0.30 to 2.57 degrees). The mean depth deviation was 0.15 mm (range, 0.10 to 0.82 mm).

CONCLUSIONS

This clinical study showed that the accuracy of computer-guided implant placement may be enhanced by using a long drill key and may thus enable more accurate implant placement in anterior regions.

Cone beam computed tomography in implant dentistry: recommendations for clinical use

BACKGROUND

In implant dentistry, three-dimensional (3D) imaging can be realised by dental cone beam computed tomography (CBCT), offering volumetric data on jaw bones and teeth with relatively low radiation doses and costs. The latter may explain why the market has been steadily growing since the first dental CBCT system appeared two decades ago. More than 85 different CBCT devices are currently available and this exponential growth has created a gap between scientific evidence and existing CBCT machines. Indeed, research for one CBCT machine cannot be automatically applied to other systems.

METHODS

Supported by a narrative review, recommendations for justified and optimized CBCT imaging in oral implant dentistry are provided.

RESULTS

The huge range in dose and diagnostic image quality requires further optimization and justification prior to clinical use. Yet, indications in implant dentistry may go beyond diagnostics. In fact, the inherent 3D datasets may further allow surgical planning and transfer to surgery via 3D printing or navigation. Nonetheless, effective radiation doses of distinct dental CBCT machines and protocols may largely vary with equivalent doses ranging between 2 to 200 panoramic radiographs, even for similar indications. Likewise, such variation is also noticed for diagnostic image quality, which reveals a massive variability amongst CBCT technologies and exposure protocols. For anatomical model making, the so-called segmentation accuracy may reach up to 200 μm, but considering wide variations in machine performance, larger inaccuracies may apply. This also holds true for linear measures, with accuracies of 200 μm being feasible, while sometimes fivefold inaccuracy levels may be reached. Diagnostic image quality may also be dramatically hampered by patient factors, such as motion and metal artefacts. Apart from radiodiagnostic possibilities, CBCT may offer a huge therapeutic potential, related to surgical guides and further prosthetic rehabilitation. Those additional opportunities may surely clarify part of the success of using CBCT for presurgical implant planning and its transfer to surgery and prosthetic solutions.

CONCLUSIONS

Hence, dental CBCT could be justified for presurgical diagnosis, preoperative planning and peroperative transfer for oral implant rehabilitation, whilst striving for optimisation of CBCT based machine-dependent, patient-specific and indication-oriented variables.

An Anatomical Study of Maxillary-Zygomatic Complex Using Three-Dimensional Computerized Tomography-Based Zygomatic Implantation

Objective

To obtain anatomical data of maxillary-zygomatic complex based on simulating the zygomatic implantation using cadaver heads and three-dimensional computerized tomography (3D-CT).

Methods

Simulating zygomatic implantation was performed using seven cadaver heads and 3D-CT images from forty-eight adults. After measuring the maxillary-zygomatic complex, we analyzed the position between the implantation path and the maxillary sinus cavity as well as the distance between the implantation path and the zygomatic nerve.

Results

The distance from the starting point to the endpoint of the implant was 56.85 ± 5.35 mm in cadaver heads and 58.15 ± 7.37 mm in 3D-CT images. For the most common implantation path (80.20%), the implant went through the maxillary sinus cavity completely. The projecting points of the implant axis (IA) on the surface of zygoma were mainly located in the region of frontal process of zygomatic bone close to the lateral orbital wall. The distances between IA and zygomatic nerve in 53 sides were shorter than 2 mm.

Conclusion

The simulating zygomatic implantation on cadaver skulls and 3D-CT imaging provided useful anatomical data of the maxillary-zygomatic complex. It is necessary to take care to avoid the zygomatic nerve injury during implantation, because it frequently appears on the route of implantation.

Computer-guided implant surgery and immediate loading with a modifiable radiographic template in a patient with partial edentulism: A clinical report

Computer-guided implant surgery in fresh extraction sites is an underdeveloped procedure. The presence of teeth that will be extracted makes the creation of an appropriate radiographic template for virtual simulation of the rehabilitation impossible. A modified radiographic template is presented to define a digital restorative simulation for the maxillary rehabilitation of a patient with partial edentulism. This modification enables 3-dimensional prosthetic virtual information in regions where teeth will be extracted.

Accuracy of a flapless protocol for computer-guided zygomatic implant placement in human cadavers: expectations and reality

BACKGROUND

This work evaluated the accuracy and safety of a protocol for minimally-invasive flapless zygomatic implant placement that uses computer-guided stereolithographic mucosa-supported surgical templates.

METHODS

A total of six zygomatic implants were placed in three formalin-fixed human cadaver heads, with edentulous and severely atrophic posterior maxillae. CT scans of each cadaver head were performed after zygomatic implant placement, to evaluate the lateral error (LE) at implant tip and base, and the angular error (AE) of the implant body.

RESULTS

Excluding the implant placed outside the drilling channel, the LE at the implant base was less than 1 mm in all cases. The average LE at the tip was 3.86 mm, and the AE was less than 6° in all cases, with an average of 4.5°.

CONCLUSION

Computer-guided minimally-invasive flapless zygomatic implant surgery remains challenging. Careful planning and perfect stability of the surgical guide are essential.

Accuracy of computer-aided implant placement

AIM

To assess the accuracy of static computer-guided implant placement.

MATERIAL AND METHODS

Electronic and manual literature searches were conducted to collect information on the accuracy of static computer-guided implant placement and meta-regression analyses were performed to summarize and analyse the overall accuracy. The latter included a search for correlations between factors such as: support (teeth/mucosa/bone), number of templates, use of fixation pins, jaw, template production, guiding system, guided implant placement.

RESULTS

Nineteen accuracy studies met the inclusion criteria. Meta analysis revealed a mean error of 0.99 mm (ranging from 0 to 6.5 mm) at the entry point and of 1.24 mm (ranging from 0 to 6.9 mm) at the apex. The mean angular deviation was 3.81° (ranging from 0 to 24.9°). Significant differences for all deviation parameters was found for implant-guided placement compared to placement without guidance. Number of templates used was significant, influencing the apical and angular deviation in favour for the single template. Study design and jaw location had no significant effect. Less deviation was found when more fixation pins were used (significant for entry).

CONCLUSION

Computer-guided implant placement can be accurate, but significant deviations have to be taken into account. Randomized studies are needed to analyse the impact of individual parameters in order to allow optimization of this technique. Moreover, a clear overview on indications and benefits would help the clinicians to find the right candidates.

Zygoma implant reconstruction of acquired maxillary bony defects

The reconstruction of acquired maxillary bony defects after pathologic ablation, infectious debridement, avulsive trauma, or previously failed reconstructions with zygoma implants represents a treatment alternative that is safe, predictable, and cost-effective. Still the single most important factor for treatment success of these complex reconstructions is the implementation of a team approach between the surgeon and the restorative dentist. The focus of this article is to review the surgical and prosthetic nuances to successfully reconstruct acquired maxillary defects with zygoma implants.

Linear and angular deviations of implants placed in experimental casts with stereolithographic drill guides fixed by o'ring ortho implant devices

The aim of this study was to evaluate whether the introduction of a device, resulting from the combination of an o'ring attachment with an orthodontic implant (o'ring ortho implant, O'ROI), to affix the surgical template of CAD/CAM-guided implant surgery contribute to minimizing the deviations in the position and inclination of implants at the time of their placement. Ten models simulating bone tissue were fabricated and randomly divided into 2 groups: 5 with the scanning and surgical template of the usual technique, representing the Control Group (C), and 5 with scanning and surgical templates fixed by o'ring ortho implants (O'ROI), representing the Test Group (T). Forty implants measuring 4×11 mm were placed in the groups, using the respective templates. The results were evaluated by the fusion of CT images of the planned and placed implants. The locations and axes were compared. There were no statistically significant differences for the angular (Tukey's test F = 1.06 and p = 0. 3124) and linear (ANOVA F = 2.54 and p = 0.11) deviations. However, the angular values of Group T showed a lower standard deviation in comparison with those of Group C. The use of o'ring ortho implants (O'ROI) is able to minimize the angular and linear deviation of implants at the time of their placement.

Accuracy of Cone Beam Computerized Tomography and a Three-Dimensional Stereolithographic Model in Identifying the Anterior Loop of the Mental Nerve: A Study on Cadavers

The objective of this ex vivo cadaver study was to determine the accuracy of cone beam computerized tomography (CBCT) and a 3-dimensional stereolithographic (STL) model in identifying and measuring the anterior loop length (ANLL) of the mental nerve. A total of 12 cadavers (24 mental nerve plexus) were used for this study. Standardized CBCT scans of each mandible were obtained both with and without radiographic contrast tracer injected into the mental nerve plexus, and STL models of the two acquired CBCT images were made. The ANLL were measured using CBCT, STL model, and anatomy. The measurements obtained from the CBCT images and STL models were then analyzed and compared with the direct anatomic measurements. A paired sample t test was used, and P values less than .05 were considered statistically significant. The mean difference between CBCT and anatomic measurement was 0.04 mm and was not statistically significant (P = .332), whereas the mean difference between STL models and anatomic measurement was 0.4 mm and was statistically significant (P = .042). There was also a statistical significant difference between CBCT and the STL model (P = .048) with the mean difference of 0.35 mm. Therefore, CBCT is an accurate and reliable method in determining and measuring the ANLL but the STL model over- or underestimated the ANLL by as much as 1.51 mm and 1.83 mm, respectively.

In-vitro study on the accuracy of a simple-design CT-guided stent for dental implants

Purpose

An individual surgical stent fabricated from computed tomography (CT) data, called a CT-guided stent, would be useful for accurate installation of implants. The purpose of the present study was to introduce a newly developed CT-guided stent with a simple design and evaluate the accuracy of the stent placement.

Materials and Methods

A resin template was fabricated from a hog mandible and a specially designed plastic plate, with 4 metal balls inserted in it for radiographic recognition, was attached to the occlusal surface of the template. With the surgical stent applied, CT images were taken, and virtual implants were placed using software. The spatial positions of the virtually positioned implants were acquired and implant guiding holes were drilled into the surgical stent using a specially designed 5-axis drilling machine. The surgical stent was placed on the mandible and CT images were taken again. The discrepancy between the central axis of the drilled holes on the second CT images and the virtually installed implants on the first CT images was evaluated.

Results

The deviation of the entry point and angulation of the central axis in the reference plane were 0.47±0.27 mm, 0.57±0.23 mm, and 0.64±0.16°, 0.57±0.15°, respectively. However, for the two different angulations in each group, the 20° angulation showed a greater error in the deviation of the entry point than did the 10° angulation.

Conclusion

The CT-guided template proposed in this study was highly accurate. It could replace existing implant guide systems to reduce costs and effort.

[Zygomatic anchorage concept in full edentulism]

The zygoma anchorage concept for severe atrophy of the maxilla was developed by Brånemark in the 1980s. It concerned patients having undergone maxillectomy as well as patients with edentulous upper jaws and mild to severe maxillary atrophy. The concept was created and clinically developed in 1997, by placing two zygomatic implants and four standard ones to compensate sub-sinus bone resorption. It was applied later to patients presenting extremely severe maxillary atrophy, using the "zygoma quad" concept with the placement of four zygomatic implants. Zygoma anchorage is reliable in terms of osseo-integration and biomechanical support of screwed prostheses, according to frequently published data (overall survival rate ranging between 91 and 100%). The increasing practice of immediate loading makes it the treatment of choice for oral rehabilitation. It decreases surgical invasiveness and the delay between surgery and oral rehabilitation. It allows a quick social and professional reinsertion and increases the comfort and quality of life for patients with fully edentulous maxilla with mild, moderate, or severe atrophy.

The influence of exposure parameters on jawbone model accuracy using cone beam CT and multislice CT

OBJECTIVE

The main purpose of this study was to investigate the influence of exposure parameters on jawbone model accuracy when using cone beam CT (CBCT) and multislice CT (MSCT).

METHODS

A lower and an upper edentulous human cadaver jaw were scanned using micro-CT (Skyscan 1173 high energy spiral scan micro-CT; Skyscan NV, Kontich, Belgium) at 35 μm to serve as true reference. The in vitro samples were exposed using six CBCT units and one MSCT system. CBCT exposure protocols were chosen according to clinically available settings. The variables were kilovoltage, milliamperage, voxel size and/or scan time. Image segmentation was based on local thresholds using profile lines. The resulting jawbone segmentations were registered with the reference and image processing was done to internally fill the segmentations. A point-based distance calculation was performed between the three-dimensional objects and reference scans and deviation percentages were calculated for 2 mm, 1 mm and 0.5 mm intervals.

RESULTS

All points of the MSCT surface models lay within a 1 mm deviation range and 98.5% within 0.5 mm compared with micro-CT. For the different CBCT systems, accuracy came close to MSCT with mean percentages of 98.9% within 1 mm deviation and 92.8% within 0.5 mm. A difference of approximately 1% between lower and upper jaws could be perceived. For the specific CBCT exposure protocols, only scan time and voxel size revealed certain significant differences.

CONCLUSION

Jawbone model accuracy using CBCT was comparable with MSCT. The surface models of the upper jaws deviated slightly more than those for lower jaws. CBCT exposure settings had a limited influence on accuracy with scan time and voxel size as the main factors.

Zygomatic implants: a critical review of the surgical techniques

PURPOSE

The purpose of the present study is to identify and describe the different surgical techniques for placement of zygomatic implants reported in the literature and discuss the differences between them.

METHODS

An electronic search was undertaken in July 2011. The titles and abstracts from these results (n = 130) were read for identifying studies, which reported different surgical techniques for placement of zygomatic implants, which resulted in 41 articles.

RESULTS

Five different surgical approaches were identified: (1) the classical approach, (2) the sinus slot technique, (3) the exteriorized approach, (4) the minimally invasive approach by the use of custom-made drill guides, and (5) the computer-aided surgical navigation system approach. When the maxilla is severely resorbed, the concavity formed by the ridge crest is small, and the original classical technique should be used. When maxillary resorption generates a large concavity, it would be better to exteriorize the zygomatic implant. The externalized technique has fewer surgical steps than the classical and sinus slot methods, is less invasive, and reduces surgical time. It is recommended that utilization of the sinus slot technique together with the CT-based drilling guide would enhance the final results. Although the technique that uses the computer-aided surgical navigation system approach may produce an improved precision in the clinical procedure, its use is expensive, prolongs the operation time, and is limited to centers that have the necessary equipment for the surgery.

CONCLUSIONS

Preference for one technique over the other should take into consideration the concavity formed by the ridge crest, maxillary sinus, and region of implant insertion in the zygomatic bone.

Zygomatic implants/fixture: a systematic review

Patients with moderate to severe atrophy challenge the surgeon to discover alternative ways to use existing bone or resort to augmenting the patient with autogenous or alloplastic bone materials. Many procedures have been suggested for these atrophied maxillae before implant placement, which include Le Fort I maxillary downfracture, onlay bone grafts and maxillary sinus graft procedures. A zygomatic implant can be an effective device for rehabilitation of the severely resorbed maxilla. If zygomatic implants are used, onlay bone grafting or sinus augmentation would likely not be necessary. The purpose of this article is to review the developments that have taken place in zygomatic implant treatment over years, including anatomic information for installing the zygomatic implants, implant placement techniques, stabilization, and prosthodontic procedures.

Computer guided surgery for implant placement and dental rehabilitation in a patient undergoing sub-total mandibulectomy and microvascular free flap reconstruction

A 58-year-old patient presented with an extensive, destructive, recurrent pleomorphic adenoma occupying the mandibular body and the soft tissues of the mouth and neck. Resection of the mandible from right ramus to left condylar process, and implant rehabilitation in both jaws with fixed bridgework was planned. Comprehensive presurgical prosthetic work up was carried out to record the existing dental relationship and guide all stages of the reconstruction. The jaw was first grafted with a segmented, fibular microvascular free-flap, which was fixed in place with a fixation plate prebent on a Rapid Prototype Anatomical Model of the jaw. Reconstruction with implant supported fixed partial dentures took place to the dental scheme planned preresection, using a computer guided approach to implant placement in the complex and unfamiliar anatomy of the extensively grafted mandible. This approach facilitated and expedited implant surgery such that treatment could take place using a minimally invasive approach relatively soon after surgery, prior to commencement of radiotherapy, and highlights the importance of a multidisciplinary approach to treatment for patients having extensive surgery to the jaws. The patient's personal assessment 2 years post surgery was recorded using 1999 University of Washington Quality of Life Questionnaire.

Zygomatic implant placement with flapless computer-guided surgery: a proposed clinical protocol

PURPOSE

The aim of the present report is to describe a procedure for zygomatic implant placement using image-guided implant surgery. This is an innovative technique and includes a new clinical approach to provide the direction to guide drilling.

MATERIALS AND METHODS

The ethical committee of the University of Genoa approved the study. All patients had clinical indications of severe maxillary atrophy (Class 4 Cadwood-Howell). A total of 25 implants were placed, of which 17 were in the premaxilla, 7 in the zygomatic area, and 1 in the pterygoid bone. The treatment was performed in 2 phases. The first phase included cone-beam acquisition to exclude sinus disease and evaluate the anatomy of the residual premaxillary bone in 3 dimensions. The success of osseointegration achieved by the primary implants (PIs) was confirmed after temporary loading and before proceeding with the second phase, in which all patients were scheduled for zygomatic implants. A total of 3 or 4 regular platform MK III implants (17 in all) were placed in the premaxilla using conventional implant surgery. A model within the analogs of the PIs was prepared (master model), taking a conventional impression. Next, a radiologic template was prepared on the same master model and stabilized on the PIs, using dedicated prosthetic components. The guide was screwed onto the PIs during computed tomography acquisition to determine a fixed and repeatable position of the guide. In the second phase, after routine planning, a mucosa-supported stereolithographic SurgiGuide with sleeves for the zygomatic implants and the corresponding stereolithographic model, including the mucosa, were received from the manufacturers. The guide was repositioned on the master model to replace the sleeves for the PIs in the same position. With an original customized surgical kit, including an innovative intrasinus device, we next simulated surgery on the stereolithographic model to determine and control the direction of the osteotomies and the final depth of drilling. The SurgiGuide was anchored onto the PIs before the zygomatic osteotomy, after which flapless surgery was performed to place the zygomatic implants according to the plan.

RESULTS

Two PIs in the premaxillary area failed (and were replaced before the zygomatic step). No zygomatic implants failed. The follow-up examinations at 4 to 39 months showed good esthetic, phonetic, and functional results.

CONCLUSIONS

The results of the proposed surgical procedure appear to be encouraging. Although it is difficult to achieve the correct driven angle of osteotomies for zygomatic implants, in all patients we achieved correct zygomatic positioning, in agreement with previous planning. Additional research and randomized clinical trials are needed to assess the predictability of the procedure.

Computerized navigation for immediate loading of dental implants with a prefabricated metal frame: a feasibility study

PURPOSE

To study the probability of using Image Guided Implantology (IGI) for planning and execution of a dental plan of 3 implants in a geometric pattern that fits a prefabricated metal frame accurately, simulating provisional restoration in immediate loading.

MATERIAL AND METHODS

Ten mandible models were imaged by standard computed tomography. Three implants, two in the premolar and one in the molar area on each side of the jaws, were planned by use of the IGI system (Image Navigation Ltd, Moshav Ora, Israel). Two millimeter drilling and subsequent 3 millimeter widening drilling was performed with the real-time computerized navigation technology in the 120 sampling sites. In each step, parallel pins were inserted, and metal gauging frames with preplanned holes of incremental diameters and in the predefined geometric pattern were placed on the pins to evaluate the precision of fit.

RESULTS

Full success was obtained in fitting all three 3-mm pins, with frames having clearance of 0.5 or 1 mm, and in matching pairs of pins 2 or 3 mm in diameter at clearances of 0.5 mm or greater. With more constrained clearances, matching of all 3 pins was 80% and 95% successful with 2-mm pins (clearance of 0.25 and 0.5 mm, respectively) and 60% and 95% successful with 3-mm pins (clearance of 0 and 0.25 mm, respectively). Some laterality bias was observed.

CONCLUSIONS

This preliminary study shows that the IGI system enables accurate planning of implant number and location to be achieved together with planning for a prefabricated metal frame for immediate loading.