Clinical and Histomorphometric Evaluation of Staged Approach Using Bone Augmentation and Autogenous Masticatory Mucosal Graft With Endosseous Implant Placement: A Case Report

After loss of teeth in the posterior maxilla, the alveolar ridge decreases by bone atrophy.1 Various bone-grafting materials have been used in bone augmentation, including autogenous graft,2 freeze-dried bone allograft,3 xenograft,4 and alloplastic material.5 In addition, various techniques have been used to deepen the vestibule and increase the keratinized mucosa.6^,7 However, there is no report evaluating the effect of additional surgery (free gingival graft [FGG]) on the maturation of the bone graft.

In this case report, bone graft in an extraction socket was done followed by FGG, and clinical and histomorphometric evaluation of the grafted area was done afterward.

A 55-year-old male patient presented to the Department of Periodontology at Seoul National University Dental Hospital, Seoul, Korea, seeking clinical evaluation and establishment of a treatment plan. The patient had a noncontributory medical history. The clinical examination revealed that the upper right first molar was hopeless. The patient was referred to the Department of Prosthodontics for further evaluation and fabrication of a treatment plan. Treatment with dental implants was planned after extraction and completion of periodontal treatment.

The patient did not return for a few months and later came to the clinic for treatment of missing teeth. The patient reported that he had his tooth extracted, and the bone augmentation procedure was done at the extraction area 6 weeks ago. The oral exam revealed that keratinized tissue was minimal, with frenal pull (Figure 1). The occlusal view showed that the extraction site was covered with soft tissue (Figure 2). The decision was made to apically displace the attachment of the frenulum and augment the gingival zone through the placement of an FGG, and then place the implant after giving sufficient healing time for the grafted area. The patient was given a detailed explanation concerning the procedure, and informed consent was obtained from the patient.

The autogenous masticatory mucosal graft (FGG) procedure was done 2 months after bone-augmentation procedure. Immediately before the procedure, the patient rinsed for 2 minutes with a 0.12% chlorhexidine digluconate solution (Hexamedine, Bukwang, Seoul, Korea). Following an injection of 2% lidocaine with 1:100 000 epinephrine local anesthetic, a releasing incision was placed between the mucogingival junction and the marginal tissue. A partial-thickness flap was reflected as close to the periosteum as possible to create the bed preparation. The 9 × 6-mm graft (length × height) was obtained from the left palate in the molar area. The graft was trimmed to produce a uniform thickness of approximately 1.00 mm. The raised partial-thickness flap was positioned apically and secured to the periosteum with absorbable sutures (Vicryl, Johnson and Johnson Medical, Inc, Arlington, Tex). The grafts were placed on the firm periosteal bed with the connective tissue side against the periosteum (Figure 3). The prepared graft was placed and stabilized with sutures over the graft. A periodontal dressing was applied, and routine postoperative instructions were given. The patient was placed on 500 mg of amoxicillin 3 times per day for 5 days, 500 mg of mefenamic acid initially, then 250 mg of mefenamic acid 4 times per day for 5 days, and chlorhexidine digluconate 0.12% 3 times per day for 2 weeks. The patient was asked not to chew or brush the surgical area for the first 4 weeks after surgery. Two weeks after surgery, the periodontal dressing and any remaining sutures were removed. The grafted area was carefully cleaned with a 0.12% chlorhexidine solution. No major postoperative problems developed, and pain levels reported by the patient were minimal.The patient received oral hygiene instructions and was shown how to achieve a roll-stroke brushing technique. The patient was seen regularly in order to monitor healing and plaque control. The average increase in the mean amount of keratinized tissue was 5 mm 6 weeks after surgery (Figure 4). The occlusal view showed that the soft tissue covering the extraction socket was under maturation (Figure 5).

Following 5 months of healing of bone grafting, computerized tomographic examination (SOMATOM sensation 10, Forchheim, Germany) was performed to assess the newly formed bone, the condition of the sinus membrane, and the presence of any sinus pathology just before the second surgery (Figures 6 and 7). The maximum available alveolar ridge height was 10 mm.

Six months after bone augmentation, the bony preparation was performed with a 2.75-mm trephine drill (inner diameter) (ACE Surgical Supply Company, Inc, Brockton, Mass) and ostetome for 4.0-mm implant. The 4 × 13-mm implant (AVANA, Osstem, Seoul, Korea) was placed, with an insertion torque of 40 Ncm (Figure 8). The specimen, from the trephine drill, was sent to the Department of Oral Pathology at Seoul National University Dental Hospital for processing for histologic evaluation. Retrieved specimens were fixed in 4% paraformaldehyde in phoshate buffer (pH 7.4), decalcified in 10% formic acid, and embedded in parafin. Subsequently, step-serial sections of the tissue blocks were made perpendicularly to the long axes using a microtome. The most technically satisfactory section was stained with hematoxylin and eosin, then the slide was examined under a light microscope (Olympus BX50, Olympus Optical, Osaka, Japan). Computer-assisted histomorphometric measurements of the newly formed bone were obtained using an automated image-analysis system (TDI Scope Eye, Seoul, Korea). The ratio of bony tissue was calculated as the bone area divided by the whole area.

A histologic view of the biopsy revealed good healing with mature bone (Figure 9). The trabecular bone is lamellar, and lacunae with osteocytes were observed in the specimen. The bone marrow was partly fibrous and partly cellular. Evaluation of the core yielded 34.1% of bone tissue.

The cover screw was exposed 3 months after implant placement. The cover screw was removed, and the healing abutment was placed. The final implant-supported crown was inserted 5 months after implant installation. The implant-supported prosthesis was functioning well up to 3 months, and the keratinized tissue was 3 mm at the final examination (Figures 10 and 11).

In the present case, the apically involved tooth was extracted. The result of bone grafting followed by FGG was evaluated histologically and histomorphometrically. Primary closure achieved at the bone-augmentation procedure seemed to create a soft tissue defect. There is no report evaluating the effect of the additional surgery (FGG) on the maturation of the grafted area.

The keratinized tissue provides increased resistance to the periodontium, contributes to the stabilization of the gingival margin position, and aids in the dissipation of physiological forces that are exerted by the muscular fibers of the alveolar mucosa onto the gingival tissues.8 It was reported that the absence of adequate keratinized mucosa in endosseous dental implants, especially in posterior implants, was associated with higher plaque accumulation and gingival inflammation.9 The shrinkage of FGGs is a well-known clinical phenomenon that occurs during wound healing in the first postoperative month.10 Orsini et al.11 evaluated the vertical dimensional changes of FGGs in prosthetically treated patients at 1, 4, 26, and 52 weeks of follow-up, and the mean shrinkage of the graft size was 10.2%, 28.4%, 37.2%, and 43.25% for the mentioned time points. In the current report, 2.2 mm (35.5%) of shrinkage was seen during a 6.5-week interval, and 3.2 mm (51.6%) of contraction was noted after 49 weeks. The shrinkage was similar but greater than the measure reported by Orsini et al.11 

Mucosal mobility around the peri-implant area was eliminated by means of a technique that augments the band of attached masticatory mucosa with an FGG.12 The vestibule was deepened and the reattachment of muscles was prevented by means of periodontal dressing.

Biopsies were retrieved and processed to evaluate regeneration of hard tissue. The ratio of bony tissue was 34.1%, and this value was comparable with the 7-month results of Carmagnola et al.13 The authors of that study made undecalcified specimens 7 months after filling the extraction sockets with only deproteinized bovine bone mineral and reported that the cylinders were comprised of 26.0 ± 23.7% lamellar bone and 8.4 ± 8.0% woven bone. Artzi et al.4 obtained bone samples from the previously porous bovine bone mineral–grafted sites 9 months after surgery, and decalcified sections were made. Newly formed bone was characterized by abundance of cellular woven-type bone in the coronal area, whereas lamellar arrangements could be identified only in the more apical region. Histomorphometric measurements showed an increase of mean bone-tissue area along the histologic sections from 15.9% in the coronal part to 63.9% apically, with an average of 46.3%.

In the present study, the bone core was detached from the trephine, and decalcified sections were prepared. In the decalcified section, thinner preparation of the specimen could be made compared to the nondecalcified section. There is less chance of overlapping of the tissue and less chance of overestimating of the histologic result.

This case report used bone graft (deproteinized bovine bone) in socket preservation followed by FGG. The additional procedure of FGG performed well as a soft tissue barrier for frenal pull, and the underlying bone showed good healing maturity with a high percentage of new bone formation.