Anatomical and radiological approach to pterygoid implants: a cross-sectional study of 202 cone beam computed tomography examinations

Comparison of the accuracy of dynamic navigation and the free hand approaches in the placement of pterygoid implants in the completely edentulous maxilla: An in vitro study

Background/purpose

Pterygoid implant is a promising solution for patients with a partially or fully edentulous atrophic maxilla. However, whether dynamic navigation system will improve the accuracy of pterygoid implant surgery is still unknown. This study aimed to compare the accuracy of dynamic navigation and free-hand approaches in pterygoid implant placement in completely edentulous maxilla models.

Materials and methods

Twenty three-dimensional (3D)-printed edentulous maxilla models were assigned to two groups: the dynamic navigation system group and the free-hand group. Two pterygoid implants were planned in the bilateral pterygomaxillary area and then placed in each model. The entry, exit and angle deviations of the pterygoid implants were measured after pre- and post-operative cone-beam CT (CBCT) image fusion. Student's t test and Mann-Whitney U test were used. A P value < 0.05 was considered statistically significant.

Results

A total of 40 pterygoid implants were placed in 20 models. The comparison deviation of the dynamic navigation group and the free-hand group showed a mean (±SD) entry deviation of 0.93 ± 0.46 mm vs. 2.28 ± 1.08 mm (P < 0.001), an exit deviation of 1.37 ± 0.52 mm vs. 3.14 ± 1.82 mm (P < 0.001), and an angle deviation of 2.41 ± 1.24° vs. 10.13 ± 4.68° (P < 0.001). There was no significant difference in the accuracy with regard to the side factors between the navigation group and the free-hand group.

Conclusion

The dynamic navigation system has higher accuracy for pterygoid implant placement in a complete edentulous maxilla than the free-hand approach.

Clinical achievements of implantology in the pterygoid region: A systematic review and meta-analysis of the literature

The purpose of the study is to evaluate the survival rate of pterygoid implants compared to implants placed in different maxilla area and to settle as an alternative solution for the rehabilitation of the posterior maxilla atrophy. Studies that were included for this systematic review were selected using different database of references: PubMed Medline, Lilacs and Cochrane Library. Other journal platforms were also used for the research. Five articles met the strict inclusion/exclusion criteria of the 180 articles founded. This systematic review was registered on Prospero (CRD42023409706) and followed PRISMA statement. A total of 768 implants placed presented 97.43 % with a peak of 100 % of survival rate. Follow-up period varies from a minimum of 1 year to a maximum of six years. Pterygoid implants could be a valid alternative in patients presenting a posterior maxilla atrophy, but results should be interpreted cautiously due to the difficulty of the surgical technique. Further studies in the future should be taken in consideration to confirm the success rate of pterygoid implants since there is only one prospective RCT, potentially incorporating modern technologies such as guided surgery or navigated surgery could be a solution for the success of pterygoid implants, minimizing the risk and less dependent on the operator.

Identifying an optimal approach for the placement of pterygoid implants: A 3D finite element analysis

STATEMENT OF PROBLEM

A consensus on the optimal approach to the placement of pterygoid implants is lacking.

PURPOSE

The purpose of this finite element analysis study was to determine the optimal approach to the placement of pterygoid implants by comparing biomechanical behavior.

MATERIAL AND METHODS

An edentulous and moderately atrophic maxilla with the anatomic structure of the pterygomaxillary region was constructed. Complete arch restorations with 4 standard anterior implants and pterygoid implants in 3 approaches were simulated: L70, long pterygoid implants (4.1×18 mm) inclined at 70 degrees relative to the Frankfort horizontal plane with anchorage in the pterygoid process; L45, long pterygoid implants (4.1×20 mm) inclined at 45 degrees with anchorage in the pterygoid process; and S45, shorter pterygoid implants (4.1×13 mm) inclined 45 degrees without apical anchorage. The L70, L45, and S45 groups were classified as D or S depending on the bone quality: D3 (dense trabecular bone) or D4 (sparse trabecular bone). A total of 6 finite element models were built. The bone failure theory, based on the von Mises theory, was used to judge yielding of the trabecular bone. The von Mises stress (σVM) distribution was measured in the cortical bone, the trabecular bone, and on the implant surface. Deformation (DF) distribution was obtained for the entire bone (DFB) and bone surrounding the pterygoid implant (DFP).

RESULTS

L70 showed a lower maximum σVM value (maxσVM), more uniform σVM distribution in the cortical bone, trabecular bone, and on the implant surface and a lower maximum DFp value (maxDFp), especially in the D4 bone. The biomechanical behaviors were similar in L45 and S45 with no stress distribution in the pterygoid process. In the D4 bone, L70, L45, and S45 exceeded the limited stress of the bone failure theory by 50%, 130%, and 130%, while all values were under the limit in D3 bone.

CONCLUSIONS

The approach of pterygoid implants inclined at 70 degrees relative to the Frankfort plane with anchorage in the pterygoid process was optimal, providing improved biomechanical behavior. Clinically, in the case of D4 bone, the inclined angulation of pterygoid implants should be 70 degrees to minimize the risk of failure.

Radiographic analysis of critical anatomical structures for pterygoid implant placement in Chinese patients with a severely atrophied maxilla

The pterygoid implant is a feasible alternative for posterior dental rehabilitation without grafting; however, the ideal pterygoid implant placement continues to be debated. The aim of this study was to identify effective landmarks and establish valid guidelines to determine the ideal pterygoid implant placement. Cone beam computed tomography (CBCT) data of 100 severely atrophied maxillae requiring implant rehabilitation, obtained between January 2015 and December 2018, were included. The CBCT data were obtained in DICOM format from the radiographic database and imported into Nobel Clinician software (Nobel Biocare) for radiographic analysis. Virtual pterygoid implant placement was successful in 67 maxillae: a 13-mm virtual implant in four maxillae (6.0%), 15-mm in 52 maxillae (77.6%), and 18-mm in 11 maxillae (16.4%). For the virtual pterygoid implant, the mean implant angulation± standard deviation in the anteroposterior axis (sagittal view) was 45.08 ± 2.56° relative to the Frankfort plane. In the buccopalatal axis (coronal view), the mean implant angulation was 64.30 ± 4.99° relative to the Frankfort plane and the mean value for the shortest linear distance between the palatine canal and apical tip of the virtual implant was 3.91 ± 0.62 mm. A 15-mm pterygoid implant placed at 45° in the anteroposterior axis and 60° in the buccopalatal axis (relative to the Frankfort plane), is generally recommended in this Chinese patient population.

Pterygoid and tuberosity implants in the atrophic posterior maxilla: A retrospective cohort study

STATEMENT OF PROBLEM

Rehabilitation of the partially or completely edentulous posterior maxilla using dental implants is a clinical challenge because of the presence of the maxillary sinus, as well as the low quality and quantity of bone in that region. In addition to bone augmentation procedures, posterior maxillary rehabilitation using implants includes their anchoring in bones such as the zygoma, pterygoid, and maxillary tuberosity, as well as in short implants. However, the performance of pterygoid and tuberosity implants in the atrophic posterior maxilla is unclear.

PURPOSE

The purpose of this retrospective cohort study was to evaluate the survival of tuberosity and pterygoid implants in patients with posterior maxillary atrophy.

MATERIAL AND METHODS

A nonprobability convenient sample of patients who had received fixed prostheses on implants placed in the maxillary tuberosity or pterygoid regions was analyzed retrospectively. Demographic variables included sex (male, female) and age. Implant-related variables included surface characteristics, site of placement, implant design, length, diameter, and anteroposterior insertion angle. Prosthetic-related variables included the type of reconstruction for rehabilitation and loading protocols. Implant survival, complications, crestal bone loss, and follow-up intervals were also documented. Collected data were analyzed at both patient and implant levels. The demographics and implant characteristics of patients receiving pterygoid or tuberosity implants were analyzed with a statistical software program (α=.05). Survival analysis was estimated by using the nonparametric Kaplan-Meier curve.

RESULTS

A total of 119 patients had 183 pterygoid or tuberosity implants inserted. Most implants in the pterygoid region (71.5%) were Ø4.1 mm (87.4%) and 15 mm in length (60.1%). The most common prostheses were complete maxillary reconstructions (49.2%) with late loading (74.3%). The average implant anteroposterior insertion angle was 60.8 degrees. The cumulative survival rate was 97.3% (n=178) during the mean follow-up period of 57 months (range 1 to 168 months). Among all implants placed, 2.7% failed (n=5) within 2 months of their placement. The statistically significant differences noted between tuberosity and pterygoid implants were related to design, surface characteristics, and loading. The average crestal bone loss was 1.5 mm.

CONCLUSIONS

The survival of the implants placed in the maxillary tuberosity and pterygoid regions was high in patients with posterior maxillary atrophy.

A Radiographic Study on Pterygoid Implants with Hamulus as a Landmark for Engaging the Pterygoid Plate - A Retrospective Study

Introduction

Rehabilitating the posterior maxilla with pterygoid implants can be quite challenging as the area entails many hindrances for implant placement. Although few studies have reported the three-dimensional angulations according to various planes (Frankfort horizontal (FH), sagittal plane, occlusal or maxillary planes), no anatomical landmarks have been identified to guide their placement. This study aimed at analysing the three-dimensional angulation of pterygoid implants using the hamulus as an intraoral guide.

Methods

Pre-operative cone-beam computed tomography scans (axial and parasagittal sections) of 150 patients rehabilitated with pterygoid implants were retrospectively analysed to determine the horizontal and vertical angulations in relation to the hamular line and FH plane, respectively.

Results

The results showed horizontal buccal and palatal safe angulations of 20.8° ± 7.6° and -20.7° ± 8.5° in relation to the hamular line. Maximum and minimum vertical angulations of 61.6° ± 7.0° and 37.2° ± 10.3° were observed, with a mean of 49.8 ± 8.1 in relation to FH plane. The post-operative scans showed that around 98% of the implants placed along the hamular line were successfully engaging the pterygoid plate.

Discussion

Comparing with the results of previous studies, this study concludes that when implants are placed along the hamular line, they are more likely to engage the centre of the pterygomaxillary junction resulting in an excellent prognosis of pterygoid implants.

Digital Approach for the Rehabilitation of the Edentulous Maxilla with Pterygoid and Standard Implants: The Static and Dynamic Computer-Aided Protocols

A full-arch rehabilitation of the edentulous upper jaw without grafting procedures exploits the residual alveolar or the basal bone, with the necessity of long implants placed with a particular orientation. The precision in planning and placing the fixtures is fundamental to avoid clinical problems and to allow an acceptable connection with the prosthesis. The computer-aided implantology resulted in more accuracy than the traditional one, with a high standard of correspondence between the virtual project and the real outcome. This paper reports about the two different digital protocols, static and dynamic, as support to implant-borne prosthetic rehabilitation of edentulous maxillae. Two pterygoid and two/four anterior standard implants were seated in both cases by two different operators, without flap raising, and immediately loaded. This approach avoided the posterior cantilever by-passing the maxillary sinus and was adequately planned and realized without any surgical or prosthetic error. The two digital flow-charts were described step by step, underlining each other’s advantages and drawbacks compared to a free-hand approach.

Immediate fixed rehabilitation supported by pterygoid implants for participants with severe maxillary atrophy: 1-Year postloading results from a prospective cohort study

STATEMENT OF PROBLEM

Few investigations concerning the use of pterygoid implants have reported reproducible and consistent data, making survival data controversial.

PURPOSE

The purpose of this clinical study was to investigate the 1-year survival and success rates of pterygoid implants and prostheses in participants affected by severe atrophy of the posterior maxilla requiring a complete-arch immediate fixed prosthesis.

MATERIAL AND METHODS

Fifteen participants, either completely edentulous or with failing dentition in the maxillary arch and with severe atrophy of the posterior maxilla, were enrolled in the study. All participants underwent prosthodontic rehabilitation after implant placement in both the anterior maxilla areas and the pterygoid regions. The survival data of the implants were evaluated at the time of abutment connection by means of a mobility test for each implant. After placement of the prostheses, survival was assessed by means of marginal bone maintenance as assessed by panoramic radiographs and the absence of pain or symptoms of infection. The t test was used for evaluating the difference in age between men and women (α=.05). Correlations between categorical variables (Fisher exact test) were used to evaluate the possible association between the number of implants and both the age and presence of comorbidities (α=.05).

RESULTS

During the 1-year follow-up, high prosthesis stability and no implant loss were observed for all participants. In addition, participants did not report any pain or paresthesia. No peri-implant radiolucency was detected in the panoramic radiographs. Survival and success rates in the follow-up period were 100%.

CONCLUSIONS

The present study supports the conclusion that pterygoid implants have a high success rate with minimal or no complications.

Accuracy Evaluation of 14 Maxillary Full Arch Implant Treatments Performed with Da Vinci Bridge: A Case Series

The use of pterygoid implants can be an attractive alternative to sinus bone grafting in the treatment of posterior atrophic maxilla. This technique has not been widely used because of the difficulty of the surgical access, the presence of vital structures, and the prosthetic challenges. The use of dynamic computer aided implantology (DCAI) allows the clinician to utilize navigation dental implant surgery, which allows the surgeon to follow the osteotomy site and implant positioning in real time. A total of 14 patients (28 pterygoid implants and 56 intersinusal implants) were enrolled in the study for a full arch implant prosthetic rehabilitation (4 frontal implants and 2 pterygoids implants), using a dynamic navigation system. The reported accuracy of pterygoid implants inserted using DCAI was 0.72 mm at coronal point, 1.25 mm at apical 3D, 0.66 mm at apical depth, and 2.86° as angular deviation. The use of pterygoid implants in lieu of bone grafting represents a valid treatment opportunity to carry out a safe, accurate, and minimally invasive surgery, while reducing treatment time and avoiding cantilevers for a full implant prosthetic rehabilitation of the upper arch.

Three-dimensional descriptive study of the pterygomaxillary region related to pterygoid implants: A retrospective study

The objective of this study was to analyze three-dimensionally the morphological characteristics of the pterygomaxillary region related to pterygoid implants. Volume, height, width and bone density were studied in relation to age, sex and dental status. This retrospective observational study analyzed the CBCT of 52 hemi-maxillas three-dimensionally (females n = 28, males n = 24; dentate = 31, edentulous = 21). Patients were exposed between September 2009 and October 2014, and data collection was performed between November 2015 and May 2016. Bone density, volume, height and width were analyzed in various locations of the maxilla and pterygoid process, and the variables age, gender and dental status patients were compared. The results show that the mean width of the pterygomaxillary joint was 7.5 mm (SD 1.00 mm), mean height was 12.51 mm (SD 1,82 mm) and mean volume was 321.7 mm³ (SD 142.02 mm³). Statistically significant differences between dentate and edentulous patients were found, showing a higher osseous density in dentate patients in the pterygoid process (758.2, SD 106.8, 95% CI 729.2 to 787.3 GSD - Gray Scale Density - compared to 689.9, SD 107.3, 95% CI 660.8 to 719.1 GSD; P = 0.022). In the maxilla, density was statistically significant lower in female subjects (571.0, SD 74.1, 95% CI 594.9 to 645.4 GSD) than in male subjects (620.2, SD 93.8, 95% CI 594.4 to 645.4 GSD, P = 0.047). In conclusion, due to the significant variation in the morphological characteristics of the pterygomaxillary region among subjects, personalized pre-surgical radiological assessment should always be performed. Gender, age and dental status are critical factors as they significantly affect bone density in this region.

Rehabilitation of an Extremely Edentulous Atrophic Maxilla with a Pseudoskeletal Class III Relationship

The skeletal class III relationship presents complex dentoalveolar problems, requiring multidisciplinary treatment. In edentulous people, severe atrophy of the jawbone simulates the clinical appearance of a skeletal class III relationship (pseudoskeletal class III), which presents major problems for rehabilitation. This article describes the rehabilitation of a 67-year-old patient with a pseudoskeletal class III relationship. The mandible was restored with two implant-supported bar-retained overdentures using clips for retention. The extremely atrophic maxilla was restored with a combination of sinus augmentation, implant placement, and classic prosthodontic treatment using an electroformed mesostructured overdenture with swivel lock attachments on an implant-supported bar. By performing minimal augmentative and implant surgeries and using the possibilities and advantages of classic prosthetic dentistry, the clinical situation described here could be managed and the atrophic maxilla could be rehabilitated.

Clinical outcomes of pterygoid implants: Systematic review and meta-analysis

The aim of this systematic literature review was to analyze clinical outcomes of pterygoid implant for the treatment of patients with atrophic posterior maxillae and to provide clinical recommendations for this dental implant technique. An extensive search of electronic databases (PubMed/Medline, Science Direct, Lilacs, Embase, and Cochrane Library) was conducted, for articles published between January 1995 and January 2018, to identify literature presenting clinical outcomes of pterygoid implants in the treatment of patients with atrophic posterior maxillae. The systematic review was performed in accordance with PRISMA/PICO statement guidelines, and the risk of bias was assessed (Australian National Health and Medical Research Council scale). The relative risk of implant failure was analyzed within a 95% confidence interval (95% CI). After screening 331 abstracts from the electronic databases, 36 full-text articles were accessed for eligibility, and a total of 6 studies were included in this systematic review (after applying the inclusion and exclusion criteria). All studies were retrospective in nature and were classified with a poor level of evidence. A total of 634 patients received 1.893 pterygoid implants, with a mean implant survival rate of 94.87%. The mean prevalence of implant failure was 0.056 with a 95% CI of 0.04-0.077. This study demonstrates that pterygoid implants can be successfully used in patients with atrophic posterior maxilla. However, the results should be interpreted with caution, given the presence of uncontrolled confounding factors in the included studies.