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

Three-dimensional digital anatomical measurements of pterygoid plates and posterior maxillary region

BACKGROUND

The posterior maxilla and skull base is a region with a complex anatomy. Accurate resection of the pterygoid plate is critical during a maxillectomy procedure. However, there is a paucity of functional and anatomical studies on the pterygoid plate and skull base. This study aimed to investigate functional anatomy of the pterygoid plate and its surrounding structures in the posterior maxilla to provide a better understanding of surgical procedures in this region.

METHODS

3D software was used to measure 3D distances, angles, and areas of key anatomical landmarks on CT images of 100 hemifaces. Morphological classification of pterygoid plates was then performed.

RESULTS

Results of comparing right and left pterygoid plates revealed no significant differences in dimensions or angles. Comparisons between sexes revealed that a few parameters were significantly different (P < 0.01), including pterygoid height on the left side, distance from the zygomatico-maxillary buttress to the infraorbital fissure (Zy-IOF), and area of the left lateral pterygoid plate. The morphology of the lateral pterygoid plate was classified into four types based on the shape of the middle region: middle convex (42%), double concave (36%), flattened (10%), and middle concave (12%). The morphology of pterygoid plates was classified based on the divergence of medial and lateral pterygoid plates, with the narrow type (56%) being more common than the wide type in this study cohort.

CONCLUSIONS

This 3D digital anatomical study measured key landmarks for maxillary resection. Such measurement has never been reported. This anatomical study provides surgeons with information on the anatomy of the posterior maxilla and allows for safer and more accurate resection of the difficult-to-resect posterior maxilla.

Anatomical study of pterygoid implants: artery and nerve passage through bone dehiscence of the greater palatine canal

PURPOSE

Pterygoid implants are an alternative approach to avoid sinus-lifting or other grafting procedures. During pterygoid implant placement, dental surgeons risk damaging the greater palatine canal (GPC). However, they do not have sufficient reasons to avoid GPC injury. This study performed a detailed morphological analysis of the GPC to determine susceptibility to damage during pterygoid implant surgery.

METHODS

To understand the detailed morphology of the GPC, gross anatomical analysis, histological analysis, and bone morphometry via micro-computed tomography were performed.

RESULTS

We found that the medial wall of the GPC communicated with the nasal cavity through the bone dehiscence. The dehiscence appeared near the inferior nasal concha in 72.4% of the cadavers. The nerve and artery passed from the GPC to the nasal mucous membrane through the dehiscence. Given that the greater palatine nerve passed medial to the descending palatine artery in the GPC, the descending palatine artery is damaged first rather than the greater palatine nerve during pterygoid implant surgery.

CONCLUSIONS

Dental surgeons who penetrate the GPC using an implant body may extend the bleeding to the nasal mucosa, which seems to spread the inflammation to the nasal cavity.

Optimizing pterygoid implant placement without sinus intrusion in edentulous vietnamese patients: A comprehensive tomographic analysis and cross-sectional study

Background

Severe maxillary resorption presents challenges in dental implant placement. This research aims to assess the feasibility, angular orientation, and appropriate length of pterygoid implants in patients with significant maxillary atrophy.

Material and Methods

The study examined Cone Beam Computed Tomography (CBCT) scans from 60 completely edentulous patients classified as Cawood and Howell's Classes V or VI, with less than 4mm residual bone height in their posterior maxilla. Experienced oral and maxillofacial surgeons and researchers conducted virtual pterygoid implant placement, evaluating various implant positions.

Results

Position C was the most frequent, comprising 34.6% of cases evaluated. The average antero-posterior angle across all positions was 51.82±5.57 degrees, and the bucco-lingual angle was 74.15±16.53 degrees relative to the Frankfort horizontal plane. The optimal location for implant neck placement was approximately 10 mm from the most distal point of maxillary tuberosity, angled 50 degrees antero-posteriorly and 75 degrees bucco-lingually. While 18 mm implants were typically used, lengths of 20-22 mm were sometimes necessary for bicortical anchorage.

Conclusions

This study demonstrates the viability of pterygoid implants even in cases of significant maxillary atrophy. The findings emphasize the importance of adapting implant placement strategies to individual patient anatomies. Further research may be needed to refine techniques for patients with severe maxillary resorption. Key words:Pterygoid Implant, Edentulous Patient, CBCT (Cone Beam Computed Tomography), Tomographic analysis.

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.

The effects of miniscrew-assisted rapid palatal expansion on the upper airway of adults with midpalatal suture in the last two degrees of ossification

BACKGROUND

Transverse deficiencies of the maxillary basal bone have been treated in adult patients using miniscrew-assisted rapid palatal expansion (MARPE) therapy. However, the midpalatal suture's degree of ossification may affect the upper airway dimensions. This study compared the volumetric changes of the total upper, retropalatal, retroglossal airways, and the minimal transverse airway constriction after MARPE therapy in patients with midpalatal suture in the last stages of ossification.

METHODS

This controlled clinical trial included a total of 20 adult patients (mean age 24.5 ± 6.2 years) with maxillary atresia treated with MARPE. Preoperative (T0) cone-beam computed tomography scans were used to determine the degree of midpalatal suture ossification. Two groups were formed considering the last two stages of sutural ossification "D" or "E" (n = 10 per group). After 120 days of the therapy (T1), cone-beam computed tomography assessments were performed to compare the pre and post-treatment outcomes. The total upper, retropalatal, and retroglossal airways and the minimal transverse airway constriction were evaluated. The three-dimensional reconstruction was performed with OsiriX MD software. The comparisons were carried out using mixed models for repeated measures at fixed time points (α = 0.05).

RESULTS

Groups D and E showed no significant difference for any of the analyzed parameters (P > 0.05). Both groups showed a statistically significant increase for all airway segments after the treatment with MARPE (P < 0.05). The total upper airway increased (11.6% and 16.1%) for groups D and E, respectively (P = 0.3356).

CONCLUSIONS

MARPE therapy resulted in dimensional gains of the upper airway for adult patients, irrespective of the intermaxillary sutural degree of ossification.

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.

Virtual pterygoid implant planning in maxillary atrophic patients: prosthetic-driven planning and evaluation

PURPOSE

The study aims to use cone beam computed tomography (CBCT) to (1) define the virtual valid length of pterygoid implants in maxillary atrophic patients from the prosthetic prioritized driven position and (2) measure the implant length engaged in the pterygoid process according to the HU difference of the pterygoid maxillary junction.

MATERIALS AND METHODS

Virtual pterygoid implants were planned with CBCT of maxillary atrophic patients in the software. The entry and angulation of the implant were planned according to the prosthetic prioritized driven position in the 3D reconstruction image. The planned implant length and the valid length defined as the implant between the pterygoid maxillary junction and pterygoid fossa were recorded. The relationship between the implant and sinus cavity was also evaluated.

RESULTS

A total of 120 CBCT samples were enrolled and virtually planned. The mean age of the patients was 56.2 ± 13.2 years. One hundred and sixteen samples could successfully place virtual implants according to the criterion. The mean implant length and mean implant length beyond the pterygoid maxillary junction were 16.3 ± 4.2 mm (range, 11.5-18 mm) and 7.1 ± 3.3 mm (range, 1.5-11.4 mm), respectively. Ninety percent of virtually planned implants had a close relationship with the sinus cavity, and implants exhibited longer lengths when they had no relation with the sinus.

CONCLUSION

From a prosthetic prioritized driven position with fixed entry and angulation, pterygoid implants achieve adequate bone anchorage length beyond the pterygoid maxillary junction. Due to the individual anatomy and the volume of the maxillary sinus, the implants presented a different positional relationship with the maxillary sinus.

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.

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.