Lateral Ridge Augmentation Using Allograft Blocks and GBR for Implant Sites

Clinicians are increasingly faced with the challenge of reconstructing the alveolar ridge as more patients desire fixed implant-supported restorations. Reconstruction of large horizontal alveolar defects still remains a challenge in implantology. Although autogenous blocks from intraoral sites are proven effective for such defects, donor site morbidity and limited graft availability are major limitations. Allogenic bone blocks have been proposed to overcome these limitations, however, the outcomes reported in the literature are inconclusive. In this case series, the efficacy of allogenic blocks for lateral augmentation of atrophic ridges was evaluated, over a three-year period.

In nineteen edentulous sites from ten patients, cortico-cancellous allogenic blocks (PHOENIX, TBF, France) were shaped to the defect and screw-fixated. A double-layer of autogenous chips and demineralized bovine bone (Bio-Oss, Geistlich Pharma AG, Switzerland) was used to fill the voids. The augmented site was covered by non-cross-linked collagen membrane (Bio-Gide, Geistlich Pharma AG, Switzerland). After a healing period of 9 months, implants were placed and CBCT analysis was performed post-implantation. Following a period of 34 months of function (range 22 to 44 months), patients were clinically and radiographically re-examined.

The present study design is a mono-center three-year follow-up case series study to examined the safety and effectiveness of allograft bone blocks combined with guided bone regeneration (GBR). The study was in accordance to the principles of the Declaration of Helsinki and was approved by the standing ethical committee of the state of Bern, Switzerland.

The preoperative analysis included a complete medical history, clinical examination of the dentition and a thorough analysis of the implant recipient using 3D cone beam computed tomography (3D Accuitomo 170, Morita, Kyoto, Japan).

Surgical Procedure:

The surgical procedures were done in two stages. In the first stage surgery, a full-thickness mucoperiosteal flap was raised on both the facial and palatal aspects. Ridge augmentation was done using a mineralized, cortico-cancellous, delipidized, lyophilized allogenic block (ALB ; PHOENIX allograft, TBF Mions, France). Following hydration of the ALB, the cortico-cancellous part of the block was shaped to fit the recipient site and fixated by two fixation screws (Medartis, Modus, Medartis Holding AG, Basel, Switzerland). Voids around the ALB were filled with autogenous bone chips (AGB) harvested locally from the recipient site. The augmented site was covered by a first layer of deproteinized bovine bone mineral mixed (DBBM; Bio- Oss, Geistlich Pharma, Wolhusen, Switzerland and a non-crosslinked collagen membrane (BG; Bio- Gide, Geistlich AG, Wolhusen, Switzerland) as described previously (Chappuis et al DOI 10.1111/cid.12438). A periosteal-releasing incision was used to provide tension-free flap closure. The wound margins were approximated using non-resorbable poly- amide suture (Seralon, Serag-Wiessner GmbH, Naila, Germany) to obtain primary wound closure. All patients were prescribed an antibiotic regimen with 2g of amoxicillin with clavulanic acid 1 hour preoperatively to be continued as 1g twice daily for 3 days post-surgery. Patients were also prescribed analgesics and chlorhexidine digluconate (0.2%) for chemical plaque control. In patients with post-surgical complications the antibiotic regimen was prolonged. Sutures were removed around 14 days postoperatively. Removable provisionals were adapted, but patients were instructed to not to wear them unless unavoidable during the initial healing phase.

The second stage surgery was performed after a minimal healing period of six months (range 6 to 13months for me this would belong to the results). A paracrestal incision was given to elevate a full thickness mucoperiosteal. The fixation screws from the previous surgery were removed and the implant bed was prepared based on the specific requirements of the site. All implants placed had chemically modified, sandblasted, and acid-etched surface and had either, a tissue level implant (TL) or a bone level implant (BL) design (SLActive, Straumann AG, Basel, Switzerland). Simultaneous re-grafting was performed as required using autogenous bone chips, DBBM and a non-cross linked collagen membrane. A tension-free wound closure was obtained by non-resorbable sutures. The antibiotic and analgesic regimen and post-surgical care as the same as in the first-stage surgery. Sutures were removed after 14 days. Patients were instructed to wear the provisional with caution. After the healing period of 4-6 months the healing abutments were placed for the future prosthetics. The implants were restored with either single-unit crowns (SC), crowns with extensions (SC-E), bridges (B), bridges with extensions (B-E) or ball abutments (BA). All restorations were screw-retained. Patient were given oral hygiene instructions and directed to enroll onto a supportive periodontal therapy to monitor oral health.

Clinical and radiographic follow-up examination after 3 years:

Clinical parameters - Updates on medical conditions, smoking, oral hygiene and enrollment in a maintenance care program were collected from the patients. Clinical examinations were taken by the same examiner (VC) throughout the three-year follow-up period. The clinical parameters were assessed as previously described (Chappuis et al DOI 10.1111/cid.12438): peri-implant suppuration, modified plaque index (mPLI), modified sulcus bleeding index (mBLI), probing depth, DIM (distance from the implant shoulder to the mucosal margin), width of the KM, mobility and full mouth plaque scores.

Radiographic analysis using 2D radiographs and 3D CBCT - The peri-implant bone loss was measured on periapical 2D radiographs analysing the proximal DIB values as the vertical distance from the implant shoulder to the first bone-to-implant contact as described earlier (DIB; mm) (Weber HP et al 1992). The mean DIB value per implant considered was the average of the mesial and distal values.

The horizontal bone gain of the atrophic sites was assessed by with the smallest field of view (3D Accuitomo 170, Morita, Kyoto, Japan). The image analysis was performed by a high-resolution screen, using a specialised software (i-Dixel, Morita, Kyoto, Japan). The 3D analysis included a preoperative analysis of the proposed implant site. A standard reference point, 4mm crestal to the shoulder of the future implant was used for all measurements (Chappuis 2017). CBCT measurements were repeated prior to implant placement, using the same reference point and repeated again at the 2-3year follow-up appointment. The radiographic measurements were done by one examiner (OE).

Assessment of biological, technical complications and patient reported outcome measures (PROMS) - All events of complications, intra-operative and post-operative at each surgical phase (graft surgery and implant surgery), prior to prosthetic treatment and post prosthetic rehabilitation both operator-assessed and self-reported were recorded.

Patient reported outcome measures were assessed by the Oral Health Impact Profile (OHIP) scores and patient satisfaction scores based on a visual analog scale (VAS) were recorded for each patient after the entire treatment was completed and the patients received the prosthetic replacements.

Statistical Analysis:

All data sets were first analysed descriptively and were expressed as mean values with standard deviation. A repeated measures design was chosen and a linear mixed model was fitted for each single factor to assess its impact on the final outcome and co-relations were evaluated. Throughout, p-values less than 0.05 were considered as statistically significant. p-values were not corrected for multiple testing due to the explorative nature of this study. The statistical analysis was performed with the software package R (Version 3.5.1, R Foundation for Statistical Computing, Vienna, Austria).

Eligibility Criteria:
Inclusion Criteria:

1. Atrophy of the alveolar ridge in the horizontal plane (\<4 mm in posterior sites and \<5 mm in anterior sites), or a crest width 5 mm in esthetic sites.
2. Patients who agree to sign an informed consent.

Exclusion Criteria:

1. Patients who had adequate horizontal ridge thickness and did not require ridge augmentation
2. Patients with deficient vertical height of the ridge requiring vertical augmentation
3. Patients who were not ready for implant supported prosthesis