Background: Reconstruction of the deficient maxillary ridge in three dimensions is crucial for the successful placement of implants. Prebent titanium meshes are an established modality for GBR, while patient-specific PEEK meshes have recently emerged with some possible advantages over the former. This study compared the effectiveness of these two modalities for bone augmentation.

Materials and Methods: 14 patients with 28 augmented sites in the maxillary ridges of primarily horizontal bone deficiencies, often associated with minor vertical components, were randomly assigned to two groups. The control group (n=7) was augmented with a prebent titanium mesh, while the study group (n=7) was augmented with a customized milled PEEK mesh. Both were grafted with a mixture of autogenous bone and xenograft. The primary outcome was horizontal bone gain. Secondary outcomes included vertical bone gain, gained bone volume, and graft resorption. These parameters were assessed by CBCT preoperatively, immediately postoperatively, and at 6 months before implant placement.

Subjects and Methods:

Sample Size Calculation: Sample size was calculated using the primary outcome variable, which was horizontal bone gain (mm), and data derived from a previous randomized clinical trial (Mounir et al., 2019)[5]. To calculate the sample size, a procedure was conducted by applying an independent-samples t-test using the software package G*Power version 3.1.9.7. There is no specific procedure for calculating the sample size for a mixed-effects model. It was conducted based on the primary outcome of interest, which was horizontal bone gain. In this case, the effect size (Cohen's d) was 0.75, α was set at 0.05, and the power was set at 80%, or 1-β = 0.80.

The primary outcome measured in this study was horizontal bone gain, which was used to determine the sample size. The secondary outcomes were vertical bone gain, gained bone volume, and graft resorption.

Study Setting:

The present study included 14 patients with 28 sites of augmented maxillary ridges, primarily presenting with horizontal deficiencies, sometimes accompanied by minor vertical components, which hinder implant placement. All patients were recruited and treated at the Faculty of Dentistry, Suez Canal University, where all clinical procedures were performed.

Randomization and Patient Grouping:

Fourteen patients were divided randomly into two equal groups using a research randomizer software (https://www.randomizer.org/). The unit of randomization was the patient (n = 14), and the measurements of outcome were obtained at the site level (28 augmented sites). Some patients had two sites augmented, and both sites were included in the analysis. Therefore, the statistical analysis accounted for the clustering effect within patients.

Participants were included by the principal investigator based on the inclusion and exclusion criteria. Allocation concealment was ensured by an independent staff member not involved in the recruitment of patients or the surgical procedure.

Although the randomization of the patients was done, all included defects satisfied the specified inclusion criteria in terms of horizontal width. However, the detailed baseline dimensions of defects for each group were not analyzed, which could have been a potential bias.

Blinding:

Blinding of the surgeon and the patients was not feasible owing to the nature of the procedures and the distinct physical properties of the meshes. Outcome assessment was performed by a single examiner (B.A.A). Although the CBCT scans were anonymized prior to evaluation, and group allocation was concealed during data analysis, it was not possible to blind the assessor completely due to the inherent radiographic differences between titanium and PEEK meshes.

To minimize measurement bias, all the measurements were performed twice at a two-week interval to assess the intra-examiner reliability. The reliability of the measurements was confirmed by the intraclass correlation coefficient (ICC) results, which showed good agreement (>0.90). Statistical analysis was conducted using coded groups.

Group 1: 7 patients with 14 augmented sites in maxillary ridges were augmented using prebent titanium mesh (served as a control group) Group 2: 7 patients with 14 augmented sites in maxillary ridges were augmented using patient-customized milled PEEK mesh. (served as a study group) All patients were evaluated by CBCT preoperatively and immediately after the bone augmentation procedure, and 6 months postoperatively, before the mesh removal. All augmented ridges were evaluated for horizontal and vertical bone gain and for the ability to place implants in the augmented segments.

Patient Selection:

Inclusion Criteria:

1. Adult patient of both sexes presenting with a partially edentulous maxillary ridge with a horizontal bone defect.
2. The horizontal ridge dimension measured 2mm below the alveolar crest should range from 2-5 mm.
3. No local pathosis that may interfere with bone healing.
4. Good oral hygiene.
5. Age between 20 and 65 years old.

Exclusion Criteria:

1. Patient taking any medication that may interfere with normal bone physiology or impair bone healing.
2. All patients suffering from any systemic disease that may affect bone healing.
3. Heavy smokers (more than 10 cigarettes per day)
4. Patients with parafunctional habits such as bruxism and clenching
5. Poor interest and cooperation from the patient.
6. Patients who have undergone any horizontal augmentation procedure at the site of interest

CBCT Segmentation and Volumetric Analysis:

All the DICOM images obtained from the CBCT scans were exported and analyzed using specific 3D image analysis software (OnDemand 3D, Cybermed, Korea). Standardization of orientation for all images was conducted prior to evaluation, in which the maxillary plane is parallel to the horizontal reference plane.

Horizontal gain of the bone was measured by standardized reference points perpendicular to the alveolar ridge, and vertical gain of the bone was compared against a fixed anatomical reference plane.

Segmentation of the augmented area was performed using a semi-automatic thresholding method. A uniform range of threshold values for all images was applied to isolate the mineralized tissue, followed by manual editing to remove artifacts and adjacent anatomical structures.

For volumetric measurements, a region of interest (ROI) was defined for the grafted area in the immediate postoperative scan, and the same ROI was duplicated for the 6-month scan. The superimposition between time points was done using voxel-based registration, focusing on stable anatomic structures such as adjacent teeth and basal bone.

The bone gain is defined as the difference in volume between the preoperative and immediate postoperative measurements, while graft resorption is defined as the difference in volume between the immediate postoperative and 6-month measurements.

I- Preoperative assessment:

• A thorough preoperative assessment for all enrolled candidates is carried out, including history taking, clinical, and radiographic examination.
• Medical history was taken from patients preoperatively to exclude medically compromised patients or patients with bad habits affecting osseointegration.
• Oral hygiene of the patients was assessed and referred to the Perio department to undergo scaling and polishing for the patients preoperatively
• A preoperative digital panoramic radiograph (OPG) with 1:1 magnification has been taken for each patient as a primary survey to identify the deficient areas and exclude the presence of any lesion in the area of interest.
• A CBCT scan is ordered for the enrolled candidates to assess the extent of the defect and evaluate the ramus donor site.

II- Clinical examination:

Interocclusal arch space was determined preoperatively. Bone width was determined clinically.

III- Pre-operative Radiographic evaluation:

• Radiographic assessment pre-operatively by CBCT to detect the patient's vertically and horizontally deficient maxillary ridge that impairs implant placement and examine the adjacent teeth for any periapical infection. All CBCT measurements were performed by a single blinded assessor (B.A.).
• Preoperative cone beam computed tomographic radiographs using the Scanora3D imaging system, using a CMOS flat panel detector with isotropic voxel size 133 μm, the x-ray tube, which is used to scan the patients, possesses a current intensity of 10 mA, 90 kVp, and a focal spot size of 0.5mm.
• The scanning time is 14seconds of pulsed exposure, resulting in an effective exposure time of 3.2 seconds to scan the FOV (field of view) of 14 cm height ×16.5 cm width. FOV adjustment is guided by three laser light beams to centralize the area of interest within the scanning field. The primary reconstruction time for a DICOM data set is 2 minutes. Then, the raw DICOM data set images will be imported to the On-Demand software for secondary reconstruction and image analysis.
• Each patient was evaluated for bone quantity, quality, as well as the relation to the mental foramen, and the detection of the remaining roots or any suspected pathological lesions. Cone beam computed tomographic evaluation will be performed to allow for a more comprehensive overall view and better interpretation of the anatomic structures. As well as the patients who have neighboring remaining roots or carious lesions are planned for treatment.

IV- Preoperative medication:

All patients received strict oral hygiene instruction to maintain periodontal health in the form of oral rinses with 0.12% chlorohexidine gluconate * 3 times per day.

Each patient was instructed to administer a prophylactic antibiotic in the form of Amoxicillin 875mg. & Clavulanic acid 125mg twice daily, one day before surgery, and continued for 5 days after surgery.

V- Surgical procedure All the surgical procedures were performed by the same surgeon using a standardized technique under aseptic conditions. All patients were operated under local anesthesia, which was injected at the defect site (articaine 4%, Septodont, France) for hemostasis. All the patients were anesthetized by the infiltration technique for the buccal mucoperiosteum and the infiltration technique for the palatal mucoperiosteum.

The proportions of autogenous bone to xenograft were not standardized across the groups, and the ratios were intentionally altered based on the unique biological and physical properties of the individual meshes. For the prebent titanium mesh group (control), the ratio of autogenous bone to xenograft was 60:40. This ratio is a well-established and validated approach in the literature for use with titanium meshes [9].

In the customized PEEK mesh group (study), a 70:30 combination of autogenous bone and xenograft material was used. This change was made to account for the decreased porosity and permeability of the PEEK material when compared to titanium mesh material. It was thought that a higher percentage of autogenous osteogenic cells and factors would be necessary to encourage vascularization and graft incorporation through the less-permeable PEEK material. Although this difference in graft composition was deemed clinically relevant and necessary in order to provide the best outcome for each material, it is recognized as one of the major methodological differences which precluded a direct and isolated assessment of the mesh material. The study, therefore, assesses two different treatment protocols, not the material itself as a separate entity.

Group 1 (control group): a stereolithographic (STL) model is designed from the reformatted DICOM files obtained from the CBCT, onto which the deficient site would be virtually augmented and 3-D printed. The Ti mesh would then be modified and adapted over the model before the surgery, as shown in Figure 1.

Stereolithographic (STL) model fabrication:

1. A specific program (Mimics 19, Materialize NV, Belgium) was used to import DICOM files. In order to create a space for the particulate graft intraoperatively, the design process began with a virtual 3D (horizontal & vertical) incremental increase for the deficient ridge until acquiring the required dimensions. The virtually grafted 3D stereolithographic model was then created using 3D printing technology (Envisiontec GMBH, Gladbeck, Germany) as a guide for prebinding a readymade titanium mesh [5].

2. The alveolar bone was then exposed by raising a full-thickness mucoperiosteal flap, which comprised a para-crestal incision with one or two vertical releasing incisions, depending on the location and severity of the lesion. Next was a full-thickness reflection of the palatal and labial mucoperiosteal flaps [5]. Group 2 (study group) :

1. Depending on the position and size of the defect, one or two vertical releasing incisions were made in addition to a para-crestal incision, and full-thickness mucoperiosteal flaps were lifted to reveal the cortical bone. Next, the labial and palatal mucoperiosteal flaps were reflected in full thickness. The entire length of the alveolar ridge's facial cortical plate was revealed by extending the reflection.
2. To facilitate graft consolidation, bleeding sites (decortication) were created using a tiny, rounded surgical bur to reveal the underlying marrow.
3. After exposing a full-thickness mucoperiosteal flap for the donor location (the mandibular ramus), it is raised.
4. Particulate autogenous chips were harvested using an auto chip maker ACM bur.
5. The PEEK mesh was loaded with the graft mixture, which is 70% autogenous bone and 30% xenograft, as shown in Figures 9 and 10.

PEEK mesh fabrication:

As seen in Figure 13, a 0.5 mm thick perforated meshwork was created to cover the buccal, crestal, and palatal sides of the alveolar bone. This allowed for the intended particle graft site to be placed between the fitting portion of the mesh and the resorbed native bone. Five five-axis milling machines were used to fabricate the final shape of the tailored device for this patient group utilizing medically grade PEEK blocks (Juvora).

Post-operative management:

1. All patients were instructed to maintain optimal oral hygiene,
2. Avoid chewing solid textured food, and apply icepacks during the first day and then warm packs for the following two days
3. Use 0.12% chlorohexidine gluconate solution and betadine mouthwash as a mouth rinse daily for 2 weeks to aid in the maintenance of oral hygiene.
4. Patients were instructed to continue the antibiotic (Amoxicillin trihydrate 875mg + Clavulanate potassium 125mg) course for 5 days after surgery.
5. Ibuprofen 400mg was prescribed as an analgesic 3 times a day.
6. After 10 days, the sutures were removed.

Postoperative follow-up:

After 6 months, clinical evaluation of the operated site was carried out. A CBCT scan was done for all candidates to assess the amount of 3D bone gain, then a subperiosteal flap was reflected, the mesh was removed. After 6 months, CBCT evaluation was performed to assess the bone gain in three dimensions. Then, the mesh was removed, and implant placement was performed in the augmented sites.

The Prosthetic Phase After 4 months, a crestal incision was made to expose the implant's platform, and a healing abutment was attached to each implant, and then the soft tissue was sutured around it.

After two weeks, an open tray impression technique was used to fabricate cement-retained porcelain-fused-to-metal (PFM) restorations.

Inclusion Criteria:

1. Adult patient of both sexes presenting with a partially edentulous maxillary ridge with a horizontal bone defect.
2. The horizontal ridge dimension measured 2mm below the alveolar crest should range from 2-5 mm.
3. No local pathosis that may interfere with bone healing.
4. Good oral hygiene.
5. Age between 20 and 65 years old.

Exclusion Criteria:

1. Patient taking any medication that may interfere with normal bone physiology or impair bone healing.
2. All patients suffering from any systemic disease that may affect bone healing.
3. Heavy smokers (more than 10 cigarettes per day)
4. Patients with parafunctional habits such as bruxism and clenching
5. Poor interest and cooperation from the patient.
6. Patients who have undergone any horizontal augmentation procedure at the site of interest

Outcome assessment was performed by a blinded examiner during CBCT analysis.