Successful multiple implant-supported prosthetic rehabilitation of Siebert class I alveolar defect at mandibular posterior site utilizing Khoury split bone block graft technique and free gingival grafting

Abstract

Insufficient dimension of alveolar bone and reduced width of keratinized gingiva may be the consequence of tooth loss accompanied by adaptive transformation. It creates a challenging situation for the clinician, especially in terms of implant-supported prosthetic rehabilitation. The present case of a 66-year-old female patient presented with an edentulous span of the right mandibular posterior edentulous site with Siebert class I defect. Literature recommended different bone augmentation procedures for such a clinical situation but are associated with a variety of risks and complications too. Adequate alveolar ridge dimensions are a prerequisite to achieve proper osseointegration; Khoury split bone block (KSBB) technique utilizing combination of thin split autogenous bone and bone particles is a popular intervention that is highly recommended in the literature and was executed in this case. Four months postoperatively Densah bur-assisted osteotomy preparation was done under osseodensification mode followed by implant fixture placement w.r.t tooth no. 45,46,47. Three months postimplant placement, insertion buccal site showed a lack of sufficient width of keratinized tissue. Therefore, free gingival grafting (FGG) was executed in order to maintain the peri-implant tissue health at the buccal aspect of tooth no. 45–47 region, followed by prosthetic rehabilitation at 12 months postoperatively. Clinically, peri-implant tissue was healthy, and no marginal bone loss was observed on radiovisual graph evaluation taken at 1.5 years, postoperatively. It was concluded that KSBB, osseodensification and FGG contributed in the excellent clinical and functional outcome of multiple implant-supported prosthetic rehabilitation at the mandibular posterior edentulous site with Siebert class I defect.

INTRODUCTION

Dimensional alteration of the alveolar process is a frequent outcome to a series of adaptive changes that take place after tooth loss, trauma, etc. Local alveolar ridge defects in the alveolar processes can be seen as deficient volume and extent of bone as well as soft tissue. 50% alveolar bone loss in the buccal-lingual dimension has been described by Schropp et al. in the 1 year following tooth extraction, with resultant dimensional reduction of jaws vertically too.[1] Such insufficient alveolar crests require surgical augmentation before implant placement in a correct position and to prevent compromised implant primary stability.

Reconstruction of a ridge defect is extremely important in areas exhibiting less buccal peri-implant bone thickness, as evaluated by Monje et al. in their study.[2] To obtain an adequate alveolar dimension so as to allow dental implant placement in either a simultaneous or staged approach, distinct reconstructive/regenerative surgical techniques such as bone block, guided bone with or without guided tissue regeneration, and distraction osteogenesis (DO), recommended in a horizontal and vertical deficient implant site have been described in the systematic review of Rocchietta et al.[3] While utilizing autogenous bone block grafts from the mandibular ramus, the Misch and Dietsh technique[4] and Khoury split bone block (KSBB) technique[5] are well reported in literature. The former has the disadvantage such as the block graft resorbed swiftly due to deprived revascularisation during the healing period, etc., as cited by Cordaro et al.[6]

Hence, in order to overcome such drawbacks KSBB technique was recommended which was first introduced and executed by Khoury et al.[5] Gluckman and Toit.[7] reported successful reconstruction of a single-tooth traumatic defect in the anterior maxilla using the SBB technique with 2-year follow-up showing more than 2 mm of bone facial to the implant which is essential for long-term esthetic stability of the soft tissue.

In contrast to the disadvantages associated with different bone augmentation techniques, KSSB technique is advantageous. In addition, extremely insufficient literature is available about KSBB technique pertaining to reconstruction of span of mandibular posterior region with Siebert class 1 defects, which can be a tough chore too other than the presence of complicating anatomical structures such as inferior alveolar nerve, lingual undercut of mylohyoid ridge, and thicker corticals than maxilla especially when multiple implant-supported prosthetic rehabilitation is the treatment of choice.

Therefore, the present case report is novel and/may be rare of its own kind to the best of our knowledge acquired through the web of literature which successfully reconstructed a long span of mandibular posterior region with Siebert class 1 defect utilizing KSBB technique, followed by multiple implant fixture placement in the atrophic posterior mandible with respect to (w.r.t) tooth no. (#) 45–47 utilizing no bone excavation technique as well as further succeeded in increasing the width of keratinized gingiva by utilizing free gingival grafting (FGG) for long-term maintenance of peri-implant soft tissue health and implant success.

CASE REPORT

The present case report is about a 62-year-old educated female patient. She was a nonsmoker, with a healthy systemic condition without any clinically significant para-functional/other habits and presented with a mobile bridge on the lower right posterior side and complained of difficulty in chewing food from that side for past 1 month. Clinical evaluation revealed a flawed mobile bridge and abscess i.r.t tooth no #47 [Figure 1a], which was slightly tender on percussion. Orthopantomogram confirmed the findings showing periapical abscess i.r.t #47 and loss of crown structure due to secondary caries [Figure 1b]. The bridge was removed, exposing grossly decayed #47 beyond restoration and an edentulous buccal lingual alveolar ridge width of <3 mm and 4.5 mm approximately w.r.t # 45 and 46 [Figure 1c], which was further confirmed after flap reflection using bone calliper. The patient willingly submitted the written consent to proceed with the extraction of tooth #47, followed by harvesting of autogenous bone graft from the mandibular ramus for three-dimensional (3-D) ridge augmentation, staged placement of Densah bur assisted 3 dental implants, followed by FGG after 3 months of fixture placement if required after listening to the pros and cons associated with the procedure.

Figure 1.

(a) Defective bridge with inflamed gingiva around #47; (b) Orthopantomogram showing periapical abscess i.r.t #47 with caries; (c) Clinical appearance after bridge removal (arrow shows Siebert class I defect wrt 45 and 46 tooth region) (d) #47 site after extraction; (e) Mucoperiosteal flap elevation to expose donor site and bone block harvested; (f) Bone block sliced into two pieces; (g) bone chips collected with scrapper; (h) titanium fixation screws assisted bone plate fixation at recipient site; (i) jump gap restored with sticky bone; (j) sutring with 6–0 suture

Following strict universal standards of surgical protocol, surgery was executed under 2% local anesthesia with adrenaline in 1:80,000 concentrations. Tooth (#) 47 was extracted [Figure 1d], and apical curettage was performed. Immediately, full full-thickness mucoperiosteal flap was reflected after giving a subcrestal incision extending distally onto the buccal shelf to expose the ascending border of the ramus of mandible to reach the donor site, and the bone block was harvested [Figure 1e] using piezo surgery unit. Bone block was split into two equal thin plates [Figure 1f] using diamond disc attached to a straight hand piece under copious irrigation, followed by scrapping of both the bony plates until a thickness of 1 mm, while collecting a good amount of bone chips simultaneously using a bone scrapper [Figure 1g]. With the help of a large contouring bur, the plates were trimmed to round their sharp edges for best adaptation to the defect site morphology. Once the desired size and shape were achieved, one plate was transferred and fixed to the buccal aspect of the recipient alveolar bone while maintaining 8–10 mm gap using two 1.2 mm diameter titanium bone fixation screws [Figure 1h]. The second thin plate was crushed with the help of bone crusher and sticky bone was made by mixing the collected bone chips with injectable platelet-rich fibrin prepared. The jump space between the recipient bone and grafted bone plate was filled with this sticky bone [Figure 1i]. Finally, the surgical site was covered with PRF membranes and for passive approximation of flaps, periosteum was released on the buccal side and muscle fibers were detached on the lingual side, followed by tension-free closure using 6–0 polypropylene monofilament sutures [Figure 1j]. Postoperative instructions, chlorhexidine mouth wash and drug regimen were prescribed to the patient. Patient reported back after 15 days for suture removal [Figure 2a]. Healing was uneventful without any complications. The patient was recalled after 4 months of healing as per clinicians’ advice for the next phase of treatment [Figure 2b].

Figure 2.

(a) Clinical photograph 15 days postsurgery; (b) Clinical site healed uneventfully; (c) flap reflection presented excellent bone bulk and quality; (d) sequential osteotomies preparation using Densah Bur; (e and e1) three implant fixture placed w.r.t tooth no. 45,46,47 region and radio visual graph taken (f) tension free flap closure; (g) Postoperative view after 15 days showing satisfactory healing of surgical site; (h) arrow denoting reduced width of buccal keratinized mucosa w.r.t # 45–47

Under local anesthesia, a mucoperiosteal full-thickness flap was elevated, which exposed excellent bone bulk and bone quality with bleeding points [Figure 2c]. Titanium screws were removed, and bone thickness of 8–10 mm approximately was observed w.r.t #45, 46, and 47 using UNC 15 probe followed by sequential preparation of three osteotomies using Densah Bur [Figure 2d]. Three conical osstem implant fixtures (4 mm × 10 mm, 4.5 mm × 10 mm, and 4.5 mm × 8.5 mm) were placed, respectively, and radio visual graph taken [Figure 2e and e1] and good primary implant stability measured using resonanace frequency analysis (RFA) (PENGUIN) 65 implant stability quotient (ISQ) average was achieved. The buccal site was packed with PRF membranes prepared as per Choukroun’s protocol before closing the flap with continuous interlocking 4–0 PTFE sutures [Figure 2f]. Suture removal was done after 15 days [Figure 2g].

Clinical evaluation 3 months postimplant placement surgery revealed insufficient width of keratinized mucosa (<2 mm) along with excessive muscle pull on the buccal aspect of grafted buccal alveolar ridge [Figure 2h]. Three weeks postsuture removal partial thickness flap was raised using 15c blade, and recipient bed was prepared to receive donor tissue [Figure 3a]. A wide FGG was harvested from maxillary tuberosity and was split into two halves to cover the entire length of recipient ridge [Figure 3b and c]. FGG was grafted and sutured facially to the implants using 6-0 polypropylene sutures [Figure 3d]. Suture removal was done after 15 days [Figure 3e].

Figure 3.

(a) Partial thickness flap incision w.r.t #45–47 and recipient bed prepared; (b and c) free gingival graft (FGG) harvested and FGG split into two halves; (d) FGG secured at recipient bed; (e) Suture removal after 15 days; (f) Healing abutments placed 1 month post FGG; (g) Soft-tissue collar healed excellently 3 week postabutments (arrow showing increased WKM with respect to buccal aspect of 45-47 implant fixture); (h) Screw retained fixed partial denture delivered and cone beam computed tomography showed all implants are in safe zone; (i and j) healthy keratinized peri-implant tissue and no marginal bone loss observed on radio visual graph

Patient returned after 1 month of soft-tissue healing with abundant peri-implant keratinized mucosal tissue clinically visible. Ten months postfirst surgery, healing abutments were placed [Figure 3f]. Implant soft-tissue collar healed excellently postadditional 3 weeks after gingival former placement [Figure 3g]. Excellent secondary implant stability ISQ 79 was measured using RFA (PENGUIN) with sound and healthy peri-implant mucosa at 12 months, followed by final restorative treatment by screw retained implant prosthesis delivery [Figure 3h].

On a 1.5-year follow up clinically healthy abundant peri-implant keratinised mucosal tissue was observed around the buccal aspect of implant supported fixed prosthesis w.r.t #45-47 [Figure 3i] without any marginal bone loss as observed radiographically [Figure 3j]. Patient is highly satisfied with the fixed teeth treatment outcome without any difficulty in food chewing till the last follow-up.

DISCUSSION

A variety of factors are responsible for the successful restoration of tooth loss when done by implant therapy, but the amount of bone at the projected implant placement location is the prime consideration.[7] Keeping this factor in mind, diverse modus operandi have been described in the literature for the augmentation of existing bone defects. However, systematic reviews have failed to identify any one technique that is particularly effective and reliable for the reconstruction of 3-D ridge defects.[8]

Yamauchi et al.[9] executed DO in 12 patients and confirmed that in spite of predictable hard tissue regeneration at the deficient bone site, the technique had some shortcomings, such as being unacceptable at patients the end due to the intraoral distraction device. A small distracted bone block may also cause exposure of the roots of adjacent teeth, and there is a need of additional bone graft in some cases.[10,11,12] Two separate systematic reviews by Fiorellini and Nevins. concluded that both guided bone regeneration and DO could augment bone vertically, but the results are still inconclusive as to which was the most effective technique because direct comparisons have not been made.[13,14] Moreover, with the use of membranes, a long time of graft healing up to 1 year is required, and an increased risk of dehiscence and infections is observed, which is found to have a detrimental effect on the regenerative outcome of the graft.[15]

Although the use of various bone augmentation materials is recommended in the web of literature but autogenous bone grafting remains the gold standard.[15] Solid bone block graft has its own disadvantage, such as fast resorption rate due to revascularization issue associated to thickened cortical during the healing tenure.[6]

Looking after the capacity of autogenous bone to regenerate and form new bone through its osteoinductive, osteogenic and osteoconductive potential, KSBB technique is a biologic modification of the solid bone block grafting procedure where the harvested bone block was split into two thin plates referred to as laminae which were fixed to the recipient alveolar ridge at a gap of 1–2 mm to recreate the stable bony box with a biologic space available within which autogenous bony particulate scrapped from the harvested bone block was packed.[16] It provides various advantages like faster as well as stable reattachment of the flap, accelerated revascularisation and regeneration due to the stable biologic space between the bone graft and recipient bone filled with autogenous bone chips, which increases the amount of vital osteocytes. Postoperative complications in the form of tissue necrosis and graft exposure are also scarce, as cited in the report of Khoury and Hanser,[16,17] other than reduction in the treatment time, less irritation during the healing phase, etc. Therefore, KSBB technique was planned and executed in the present case in addition to scarce literature pertaining to the same in postmandible. The outcome achieved in the present case was in accordance with the reports of Gluckman and Toit.[7] and Khojasteh et al.[18] who utilized KSBB technique, but they have utilized it in maxilla region.

The reason for the best outcome achieved in the present case in terms of significant ridge augmentation which is one of the prerequisite for achieving osseointegration for long-term implant success; may be because of the ideal conditions created for implant surgery using pure autogenous material via splitting the bone block into two thin blocks KSBB which increases the no. of blocks, offering the possibility of more graft surface in different forms which further allows an acceleration of transplant revascularization as observed on re-entry which showed thoroughly integrated bone graft with macroscopic vascularity, thereby improving bone regeneration.[17] In addition to a reduction in the time and trauma during surgery and reduced anesthesia used due to the proximity of donor as well as grafted sites, the surgery was performed with the use of specified instrumentation and protocol by an experienced clinician. Although dehiscence is the common complication observed in different ridge augmentation techniques, it was not observed in our case which may be due to sufficient soft tissue management, plate preparation, and grafting within the bone envelop.[19]

Another reason which contributed in long-term success of implants was achieved through minimally invasive nonbone excavation technique, utilization via Densah bur-assisted osteotomy preparation, which leads to lateral compaction/autografting of endosseous bone which resulted in increased bone density and bone-to-implant contact; thereby increasing the primary stability.[20]

The risk of inadequate width of keratinized mucosa increases from 2.62 times to 1.65 times in complex and simple bone augmentation procedures for implant placement as reported by Wang et al.[21] Similar observation in terms of inadequate width of keratinized mucosa was observed in the present case too following KSBB augmentation procedure.

Despite controversies pertaining to importance of Width of keratinised mucosa (WKM) still it is important from a patient comfort point of view and ease of plaque removal. In addition, a lack of WKM is claimed to be associated with recession with respect to peri-implant mucosa.[22] Therefore, giving due consideration to the above factors pertaining to the inadequate width of keratinized gingiva, FGG augmentation was executed in the present case, and excellent outcome achieved in terms of gaining the width of keratinized mucosa/gingiva may be because FGG is simple to execute, reliable and prevents the progression of gingival recession.[23]

CONCLUSION

Success of Implant supported prosthesis at Siebert class I alveolar ridge defect and reduced width of keratinized tissue can be best achieved through three staged treatment plan starting with 3-D bone augmentation using KSBB grafting, followed by implant fixture placement after nonbone excavation assisted osteotomies preparation and further succeeded by FGG, which not only improves the quality life of patient but enhances implant success predictability too.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.