Alveolar ridge resorption after tooth loss

Transcription

1 The Art of Block Grafting A Review of the Surgical Protocol for Reconstruction of Alveolar Ridge Deficiency Toscano et al Nicholas Toscano, DDS MS 1 Nicholas Shumaker, DDS MS 2 Dan Holtzclaw, DDS MS 3 Abstract Alveolar ridge resorption after tooth loss is a common phenomenon. After a tooth is extracted the alveolar ridge decreases in width and height very rapidly, with as much as 50% loss in width during the first year, two-thirds of which occurs in the initial 3 months. Often in clinical practice, the loss of a tooth does not coincide with replacement by a dental implant and there is frequently a lag of months to years before an edentulous site presents for therapy. Therefore it is often required that we perform hard tissue ridge augmentation to increase bone volume prior to dental implant placement and restoration. The purpose of this article is to review the modern art of block grafting using the mandibular symphysis and ramus buccal shelf donor sites for alveolar ridge reconstruction in preparation for dental implants. The clinical indications, advantages and disadvantages of each site, and the surgical techniques necessary for optimal outcomes will be discussed. While earlier techniques were rather rudimentary, this article will show how current techniques which integrate the principles of guided bone regeneration ensure minimal resorption during integration and a predictable, time-efficient, and cost effective outcome. KEY WORDS: Bone augmentation, ramus, symphysis, dental implants 1. Private Practice, New York, NY 2. Dental Department Head, Periodontics Department Head, Naval Health Clinic Quantico, VA 3. Private Practice, Austin, TX The Journal of Implant & Advanced Clinical Dentistry 45

2 Introduction and Background Alveolar ridge resorption after tooth loss is a common phenomenon. After a tooth is extracted the alveolar ridge decreases in width and height very rapidly, with as much as 50% loss in width during the first year, two-thirds of which occurs in the initial 3 months. 1 Restorations supported by dental implants are currently a widely accepted and successful treatment modality for the treatment of partial and complete edentulism 2. Often in clinical practice the loss of a tooth does not coincide with its replacement by a dental implant. Unfortunately there is frequently a lag of months to years before an edentulous site presents for dental implant therapy. Therefore it is often required that we perform hard tissue ridge augmentation to increase bone volume prior to dental implant placement and restoration. Several treatment modalities have been described for osseous augmentation of edentulous ridges prior to implant placement. These include guided bone regeneration 3 ) with or without particulate bone grafting, 4,5 ridge splitting, 6,7 distraction osteogenesis, 8 orthodontic tooth movement through a deficient ridge. 9 and grafting of bone blocks harvested intraorally, extraorally, or from cadaveric (allogeneic) sources , 26 Each treatment modality has its own indications and contraindications, as well as advantages and disadvantages. Edentulous ridge augmentation using intraorally harvested bone blocks from the mandibular symphysis and the ramus buccal shelf are attractive techniques for several reasons. The advantages include: 1. Horizontal alveolar bone volume increase documented at up to 7.5mm, compared to only up to 4.5mm increase documented with particulate GBR techniques. 5,16 2. Rapid integration allows early reentry for implant placement, often in 3-4 months compared to the 6-9 months required for 5, 12, 16, 17 particulate GBR techniques. 3. Optimal bone density for implant stability due to the cortical nature of the graft. 4. Reliable space maintenance during healing ensures the shape and stability of the bone block is retained without collapse Locally available donor sites avoid the need for extraoral autogenous bone sources. 26 The purpose of this article is to review the modern art of block grafting using the mandibular symphysis and ramus buccal shelf donor sites for alveolar ridge reconstruction in preparation for dental implants. The clinical indications, advantages and disadvantages of each site, and the surgical techniques necessary for optimal outcomes will be discussed. While earlier techniques were rather rudimentary, this article will show how current techniques which integrate the principles of guided bone regeneration ensure minimal to no resorption during integration, and a predictable, time-efficient, and cost effective outcome. Overview The mandibular symphysis and ramus buccal shelf are excellent intraoral sources to obtain a cortico-cancellous or pure cortical bone block, respectively, for alveolar ridge augmentation. The symphysis has been reported to provide sufficient bone to augment a deficient ridge by 4-6mm in the horizontal dimension, and up to 4mm in the vertical dimension, covering a length of up to a 3-tooth defect. 12,18 Bone block 46 Vol. 2, No. 2 March 2010

3 size available from this location has been found to be an average of 10 mm (height) x 15 mm (width) x 6 mm (thickness), with an average bone volume of approximately 860 mm. 3,19 The symphysis offers over 50% larger graft volume than what can be obtained from the mandibular ramus, with much easier surgical access. 20 The average symphysis graft has been found to be composed of 65% cortical bone and 36% cancellous bone, as opposed to the mandibular ramus, which is nearly 100% cortical in nature. 19 The cortico-cancellous nature of bone harvested from this site facilitates faster vascular in-growth once the block has been placed, resulting in more rapid integration and less potential resorption during healing. 21 Moreover, bone blocks harvested from sites formed by intramembranous mechanisms (intraoral) have been shown to revascularize faster than those from an endochondrally (extraorally) derived formation pathway. 22 The mandibular ramus buccal shelf block graft can provide adequate bone for augmentations involving a span of 2-3 teeth. Horizontal as well as vertical augmentation of 3 to 4 mm can be achieved with this donor site, the former being more predictable. 17, Ramus cortical bone blocks have a maximum thickness of 4 mm, providing a rectangular graft with a length which may approach 35 mm and a height of up to 10mm, depending on patient specific anatomy. The limits of bone block size obtained from the ramus area are generally dictated by clinical access, in addition to the coronoid process, inferior alveolar canal, molar teeth, and width of the posterior mandible. 17,23-25 Therefore the selection of this location requires careful pre-operative planning to ensure adequate block size can be obtained. Specific individual success rates of bone block grafts from the mandibular symphysis and ramus buccal shelf are not well reported in the literature, as most articles group ramus and symphysis grafts together in success data reporting. However, within these data success rates are reported at %, with success usually defined as sufficient bone for implant placement. 11,18,20,26 Advantages and Disadvantages While the mandibular symphysis has many advantages, there are some disadvantages which practitioners must be aware of when selecting this harvest site. Post-operative morbidity is reported after symphysis grafting and is perhaps the largest concern with this site. Misch found that 10.7% of patients experienced incision dehiscence at the donor site, 9.6% had temporary paresthesia for up to 6 months, and 29% had altered lower incisor sensation. 20 Chin ptosis (esthetically unpleasing chin droop) is often a concern surrounding symphysis harvest, however occurrence of post-operative esthetic changes has not been found in most published articles. 20,27-29 One long term follow-up report found that up to 13% of patients have lasting loss of sensation of the local chin area, however when questioned all patients stated that they did not find it bothersome. 28 Also another long-term study found that a small residual radiographic bony defect in the symphysis does persist after healing, however no esthetic changes were associated with this finding. 29 While long-term morbidity after symphysis harvest is minimal, reports show that it is slightly higher than mandibular ramus grafts and therefore this must be taken into consideration when select- The Journal of Implant & Advanced Clinical Dentistry 47

4 Table 1: Comparison of Ramus vs Symphysis block grafting Bone Volume Type of Bone Post-Op Complications Mandibular ~5-10cc Corticocancelious Altered incisor sensation = 29% Symphysis ~4-7mm thick (Intramembranous) Temporary paresthesia = 9.6% ~2cm long Incision dehissence = 10.7% ~1cm in height Ptosis Lip incontinence Mandibular ~5cc Mostly cortical IAN damage Ramus ~4mm thick (Intramembranous) Buccal nerve damage ~3cm long ~1cm in height Trismus Manbibular fracture ing the technique which will achieve the desired ridge augmentation needed for dental implants. The mandibular ramus donor site is associated with fewer postoperative complications, in comparison to the symphysis region (Table 1). 23,24,30,31 Misch found that in fifty block graft cases the ramus donor site was associated with zero complications after 6 months of healing. Incision dehiscence during healing at the ramus donor site occurs with comparatively less frequency. Additionally, patients are less able to discern neurosensory disturbances in the posterior buccal soft tissues compared with the lower lip and chin. 20,23,24 Although the incision along the external oblique ridge could damage the buccal nerve, reports of postoperative sensory loss in the buccal mucosa are rare and will most likely go unnoticed by the patient 20 In contrast to the teeth superior to the symphysis donor site, patients have reported no altered sensation in their molar teeth after ramus block graft harvest. 23,24,30,31 Graft resorption during healing at the recipient site is always a possibility with any bone block grafting procedure. 32 Resorption rates for both symphysis and ramus grafts using modern techniques, however, are reported as very miniscule with published articles finding 0-25% during healing. 12,13,17,20,23-25 Using the techniques described in this article the authors have observed near zero resorption during healing in the majority of cases. Preoperative Assessment and Preparation Proper preoperative assessment is paramount to successful execution of symphyseal and ramus buccal shelf graft harvests. As with any 48 Vol. 2, No. 2 March 2010

5 Resorption Indications Contraindications Advantages Disadvantages 0-25% Ridge augmentation Inadequate donor Access quality Greater post-op for dental implants site without 3-5mm of bone complications (Block or particulate) safety zone to Potential for limited Esthetic concerns Particulate bone mental nerves, particulate marrow (chin ptsosis) source for peridontal lower border, and harvest after regeneration or incisor apices block removal sinus augmentation 0-25% Ridge augmentation Inadequate donor Mostly cortical Access for dental implants site without >1.5cm bone Mostly cortical (Block or particulate) between donor site No esthetic bone Particulate bone and IAN concerns source for peridontal regeneration or sinus augmentation surgery, a thorough medical history must be reviewed. Elective procedures for treatment of partial edentulism are generally reserved for patients in ASA 1 or ASA 2 physical status, which includes patients who are systemically healthy or with only a mild to moderate well controlled systemic disease. 33 Patients with uncontrolled or severe systemic diseases should be medically optimized by their physicians prior to becoming candidates for these procedures. Practitioners should proceed with caution in patients who are tobacco users, as well as patients with metabolic diseases which affect bone metabolism or wound healing when using these procedures, such as diabetes mellitus, osteoporosis, or immunocompromise. Clinical examination for a potential symphyseal or ramus graft patient should include an extraoral exam to rule out any pre-existing esthetic, functional, or neurological defect. The intraoral exam should begin with assessment of the recipient site to be augmented, to ensure the symphysis or ramus can provide sufficient bone volume for the desired final implant position. Pulp testing of the mandibular anterior or posterior teeth nearby should be performed to ensure no pre-existing pulpal necrosis or periapical pathology exists nearby to the area(s) of proposed bone harvest or augmentation. For the symphysis graft an assessment of the height of attachment of the mentalis muscle, the periodontal, caries, and endodontic health of the mandibular anterior teeth should be made. Also a measurement of the width and thickness of attached gingiva at the lower incisors and the depth of the mandibular ante- The Journal of Implant & Advanced Clinical Dentistry 49

6 rior vestibule should be made to assist in the selecting the appropriate incision design. For the ramus buccal shelf graft, clinical assessment is important to identify the location of the inferior alveolar and mental nerve relative to the graft harvest and recipient sites. The periodontal, caries and endodontic health of the mandibular posterior teeth should also be assessed. Radiographic examination is extremely important to assessing whether a patient s specific symphyseal and/or ramus anatomy is sufficient for graft harvest. At a minimum, preoperative radiographs should include 1) a panoramic radiograph to locate adjacent structures, 2) periapical radiographs of the mandibular anterior or posterior teeth to rule-out periapical pathology, 3) a lateral cephalometric radiograph to assess bone thickness and quality of the symphyseal region. Additionally, assessment by conventional or cone-beam computed tomography (CT) is recommended to best evaluate the thickness and quality of the symphyseal and ramus region across the entire length and width of the potential harvest site, as well as the recipient graft site. Examination of the radiographs must ensure that a bone block harvest and fixation of the desired thickness and size will not encroach on surrounding vital structures including the mental foramena (including anterior loops), inferior alveolar nerve (including mental foramen), the apices of the mandibular incisors and canines, the inferior border of the mandible, nor the lingual cortex of the mandibular symphyseal region. For the symphysis graft, the Rule of 5 s should be respected in assessing and performing block harvest (Figure 1). This rule requires that at least 5mm of uninvolved bone is present Figure 1: The rule of 5 s of symphysis bone block harvesting respects the surrounding vital structures to prevent damage to the dentition, sensory innervation of the mental nerve, and the inferior border of the mandible. beyond the proposed osteotomy margins of the block and the surrounding structures, providing a margin of safety to prevent potential morbidity. 34 Symphyseal thickness measured from the lateral cephalometric radiograph must be sufficient for obtaining the desired block size without violating the lingual cortex of the mandible. For the ramus graft it is important to assess the distance from the external oblique ridge to the superior aspect of the inferior alveolar canal. A minimum distance of 10mm is needed to safely remove a ramus block graft without injury to the inferior alveolar nerve. When measuring this distance on two-demensional radiographs the clinician must be aware that the external oblique ridge where ramus graft harvest is often accomplished is not always the most superior point on the panoramic radiograph of this region. Additionally the absence 50 Vol. 2, No. 2 March 2010

7 Figure 2: Three types of incision design options are available for symphysis access. The sulcular approach, the attached gingiva approach, and the vestibular approach. of impacted third molars or retained roots which may complicate harvest should be confirmed. Preoperative Preparation Prior to the day of surgery, patients are started on an oral regimen of steroids and antibiotics to prevent postoperative swelling and infection. Steroid medications consist of either a methylprednisone dose pack, or 12mg per day of dexamethasone tablets beginning the day prior to the surgery. 35 Studies have shown that when steroid medications are delivered prior to surgical incision, anti-inflammatory effects postoperatively are much greater. 35,36 Antibiotics are prescribed preoperatively because during the surgery oral bacteria are most certainly introduced into the bone. Having a blood level of antibiotic in the system preoperatively means that the newly formed blood clot around the graft site will have the benefit of containing antibiotic during early wound healing to assist the body in clearing the oral bacteria introduced during the surgery. Broad spectrum antibiotics such as penicillin or doxycycline are recommended. Bone block grafting surgery can be a very stimulating procedure for many patients. While these procedures can be comfortably delivered under local anesthetic only, anesthetic management of the patient should be evaluated on a case by case basis. Anesthetic options including local anesthetic only, oral sedation, IV conscious sedation, or general anesthesia are appropriate to offer to each patient during the preoperative decision making consultation. Infection control during this type of procedure is of utmost importance. Flap refection and advancement in advanced ridge augmentation procedures involves exposure and entry into several anatomic spaces including the submental, submandibular, sublingual, buccal, and canine spaces, which can put the patient at risk for airway compromise or spread of infection to the brain if postoperative complications present. Prevention of these complications is paramount. Infection control for bone block grafting should include use of sterile drapes, gowns, and preoperative 0.12% chlorhexidine intraoral rinse, as well as perioral skin preparation with an approved surgical scrub, such as 4% chlorhexidine/alcohol swabs. Graft Recipient Site The recipient site to be grafted should be accessed prior to beginning surgery at the donor harvest site. This sequence is important so that the recipient site may be measured and assessed to determine the size, volume and shape of bone block(s) required to achieve the desired result. Use of a surgical guide which indicates the desired final implant position is helpful to assess the amount and position of grafting required. Crestal incision and full thickness flap reflection is the preferred method at the recipient site. Inci- The Journal of Implant & Advanced Clinical Dentistry 51

8 Table 2: Incision design options for symphysis block graft harvest (Gapski 2001) Sulcular Attached Gingiva Vestibular Indications Shallow vestibule Requires 3mm of Periodontally compromised Tense mentalis keratinized gingiva lower incisors Healthy periodontium Crown margins on lower incisors Deep vestibule Advantages Reduced bleeding Prevents gingival Least potential for Reduced trauma recession periodontal compromise Easier flap retraction Reduced bleeding Reduced trauma Easier retraction Easier suturing Disadvantages Potential for Scarring More complicated recession and Need for vertical suturing (must suture crestal bone loss release at distal muscle layer) Exposure of crown extent of incisions Increased dehissence margins if present Gingival recessions Increased bleeding possible if root dehissences exist Increased edema sions and reflection should be wide enough for complete access to the site, and for adequate access for later tissue release for passive closure. Once the desired block size has been measured, the recipient site can be covered with moist gauze while the donor block harvest proceeds. Symphysis Block Graft Harvest Access to the mandibular symphysis area can be achieved by one of three different incision designs, 1) sulcular, 2) attached gingiva, or 3) vestibular (Figure 2). The sulcular and attached gingiva approaches have the benefits of reductions in both post-op wound dehiscence and intraoperative bleeding compared to the vestibular approach, however these two techniques are limited by the clinical situation. Use of the sulcular approach requires that there are no pre-existing periodontal diseases or crown margins which could become exposed by incision in this area. Gapski, et al published an excellent review of incision design options for symphysis graft procedures outlining the indications, advantages and disadvantages of each technique, summarized in Table Selection 52 Vol. 2, No. 2 March 2010

9 of the access incision technique should be made based on clinical findings and provider preference, since all methods offer equally favorable access to the symphyseal region. The sulcular and attached gingiva incisions involve full thickness muco-periosteal flap reflection, lifting the mentalis muscle off with the periosteum as reflection proceeds to the inferior border of the anterior mandible. When performing the vestibular incision, a more technically demanding approach is needed. This incision is made through the mucosa 1-2mm below the mucogingival junction followed by partial thickness dissection apically for 3mm to preserve 3mm of periosteum and mentalis muscle fibers on the bone, which will later be used to reattach the mentalis muscle. Below this point a full thickness incision is made and full thickness reflection proceeds beyond this point. When performing the access incision careful attention must be paid to the position of the mental nerves to prevent trans-section of these areas at the distal extent of the incisions bilaterally. The rule of 5 s should again be respected here, and potential risk for severing of the nerves is least using the sulcular approach. Reflection of the soft tissues away from the anterior mandible is performed by blunt dissection below the periosteum. Elevation should proceed until the mental foramina are located and the inferior border of the mandible is reached. Block harvest can begin once these structures have been identified. Combined with radiographic measurements from the incisal edges or CEJ s of the mandibular anterior teeth, the rule of 5 s can be applied to identify the target area for safe block harvest. Prior to beginning the osteotomy, the Figure 3: Symphysis block osteotomy completed using a saggital saw with 0.7mm thick blade. Note that this block has been harvested to the right of the midline, avoiding violation of the midline bone strut of the symphysis. recipient site should be re-measured and transferred to the symphysis to indicate the desired block size by making notches in the bone at the corners of the block outline. Pikos recommended that the block outline be 2mm larger than the target size to allow for contouring of the block after removal. 2 When selecting the area of the symphysis for block harvest, avoid violating the midline strut of bone in the anterior most portion of the symphysis, known as the mental protuberance. If necessary two blocks can be harvested from each side of the midline, leaving a 3mm midline strut to retain support for the chin profile. 12 Osteotomy can be performed with a rotary bur, saggital saw, or piezotome instrument. The latter two instruments are preferred over a rotary bur due to the narrow width of the resulting cut, reducing bone lost during osteotomy. While most rotary burs are at least 1mm in diameter, use of a saggital saw or piezotome instrument results in a precise cut of only 0.5- The Journal of Implant & Advanced Clinical Dentistry 53

10 Figure 4: The block is loosened with mallet and chisels. The periphery of the osteotomy is redefined with the chisel and the width of the chisel is used to begin shearing the block off it s cancellous base without lifting upwards. Figure 5: Once the block as been freed by shearing forces, it can be lifted by undermining with curved chisels and gently lifted out. The need to use excessive force at this stage indicates the block is not sufficiently free and risks fracture. 0.7mm in width which preserves bone and also results in comparatively less surgical trauma to the bone. 38,39 Osteotomies should penetrate the cortical layer, giving close attention to the depth of each cut relative to the width of the symphysis found on pre-operative radiographic evaluation to prevent violation of the lingual cortex (Figure 3). The terminal end of each cut around the block should cross over itself in an x-like pattern to ensure complete release of the block. Once cuts are complete, narrow chisels can be used to refine the outline of the block and begin to shear the cortico-cancellous block off of the underlying trabecular bed (Figures 4 and 5). Care and patience must be taken when releasing the block to preserve the entire block volume. Overzealous lifting of the block before it is completely free may result in its fracture. After block removal an absorbable collagen sponge is placed in the recipient site for hemostasis (Figure 6). Alternatively, the harvest site may be grafted with Freeze Dried Bone Allograft (FDBA) if desired, especially in cases where a large block has been removed. Closure at the donor site depends on the incision method utilized. When closing the vestibular approach, a resorbable suture is first used to secure the mentalis muscle to the 3mm periosteal/muscle layer left on the bone during the initial incision. This is achieved by interrupted sutures at regular intervals across the mentalis release. The overlying mucosa is then closed with a nonwicking continuous interlocking suture. (Figure 10) For sulcular and attached gingiva incisions the mentalis muscle remains attached to the periosteum and does not need to be sutured. Closure of these latter two incision types involves interrupted sutures at papilla areas (sulcular) or along the attached gingival incision line. Appli- 54 Vol. 2, No. 2 March 2010

11 Figure 6: After the block is removed, the donor site is packed with an absorbable collagen sponge for hemostasis. The site may also be grafted with particulate bone. Figure 7: The block is carefully shaped to assist in stable and close adaptation to the recipient bed. Care should be taken to avoid over-reducing the bone block graft. If excessive changes are needed to achieve stability, then the recipient site should be adjusted as well. Figure 8: The block is fixed with at least two fixation screws to ensure stability and anti-rotation. Screw osteotomies through the block should be lagged so that threads do not engage. Intramarrow penetration is performed under the block, at the recipient bone bed, prior to fixation. Figure 9: The periphery of the bone block is mortised with freeze dried bone allograft (FDBA) and a collagen membrane is placed over the entire graft, extending 3mm beyond the block in all directions. The Journal of Implant & Advanced Clinical Dentistry 55

12 Figure 10: Closure at the donor site. Figure 11: The appearance of the block upon reentry after 4 months of healing indicates a favorable healing outcome. Minimal resorption was observed. Figure 13: Final abutment and restoration in place. Figure 12: Radiographic appearance of the implant placed in the graft at the time of uncovering. cation of an extraoral pressure dressing (elastic chin-cup) to the symphysis area for hours post-operatively is advisable to prevent hemorrhage and promote initial healing which supports reattachment of the mentalis muscle. Ramus Buccal Shelf Block Harvest Harvest of a block bone from the mandibular ramus buccal shelf has features similar to a sagittal split ramus osteotomy (Figures 14-17). The incision design for access to the ramus can proceed by two different approaches: 1) Vestibular or 2) Sulcular. The vestibular incision begins in the buccal vestibule, medial to the external oblique ridge, and extends anteriorly and laterally to the retromolar pad (Figures 18, 19). This technique has the advantage of not disturbing the periodontium of the adjacent teeth. Alternatively, the sulcular incision starts intrasucularly around the mandibular molars and then extends from the distal facial line angle of the 56 Vol. 2, No. 2 March 2010

13 Figure 14: Pre op facial view of Siebert s I defect post extraction of tooth #10 prior to ramus block grafting. Figure 15: Incisal view of Siebert s I Defect tooth # 10 prior to ramus grafting. Figure 16: Flap reflected #10 revealing osseous defect prior to grafting. Figure 17: Facial view of flap reflected #10 revealing the extent of the osseous defect to be grafted. second molar along the external oblique ridge. The sulcular technique is beneficial when the receipient site is nearby, such as the mandibular first molar region. Regardless of the incision design selected, the incision up the ascending ramus should no higher than the level of the occlusal plane. This minimizes the possibility of severing the buccal branch of the facial nerve, the buccal artery or exposing the buccal fat pad, where these structures are located. After the incision, sub-periosteal full thickness flap reflection proceeds by blunt dissection, exposing the anterolateral aspect of the ramus. The flap may elevated superiorly along the external oblique ridge and anterior ramus with a notched ramus retractor or ramus stripper to the base of the coronoid process (Figures 20, 21). The tissues can then be held out of the way with a coronoid clamp for maximum visualization. The ramus osteotomy procedure is accomplished in similar fashion to the symphysis graft with regard to penetrating the cortical layer The Journal of Implant & Advanced Clinical Dentistry 57

14 Figure 18: A surgical marking pen is used to outline area of the vestibular incision. Figure 19: Vestibular incision complete revealing area of ramus buccal self (marking pen outlines area of ramus block to be removed). and controlling effective x-pattern cut-through at the block corners to ensure a free release. As with the symphysis graft, the osteotomy can be accomplished with a rotary bur, piezoelectric saw, or saggital saw, the latter two having 38, 39 the advantage of more conservative cutting. The ramus osteotomy is started anterior and inferior to the coronoid process at a point where adequate thickness develops. The order of the osteotomies proceeds as superior cut, then anterior, then posterior, and finally the inferior cut, facilitated by the pneumonic SAPI. Radiographic verification of the position of the mandibular canal relative to the external oblique ridge and anterior aspect of the ramus must be completed prior to initiation of the osteotomy. The superior cut should reflect the desired length and thickness of the bone block. This cut is usually made approxi- 58 Vol. 2, No. 2 March 2010

15 Figure 20: A ramus stripper produced by KLS Martin, Tuttlingen, Germany. Figure 21: The ramus stripper is used to strip the periosteum off the external oblique ridge to give maximum access to the ramus buccal shelf. Figure 22: Surgical cuts made with a sagital saw prior to outfracture of the ramus block. Figure 23: Ramus block graft is outfractured with chisels via gentle tapping, the periphery of the osteotomy is redefined with the chisel and gentle outfratured. The Journal of Implant & Advanced Clinical Dentistry 59

16 Figure 25: Ramus block graft prior to fixation to the receipt site. Figure 24: Ramus area after removal of the block prior to closure. Figure 26: Incisal view of ramus block graft fixated with two KLS bone fixation screws. mately 4 mm medial to the external oblique ridge but can approach up to 6 mm depending on the anatomy. It may be extended anteriorly as far as the distal aspect of the first molar area, depending on local anatomy. The anterior and posterior vertical cuts are made in parallel to the desired length and width of the block, and are limited in their inferior extent by the anatomic position of the mandibular canal, which determines the block width (Figure 22). The inferior osteotomy will connect the posterior and anterior vertical cuts, completing the outline of the block. This final cut should not generally extended through the cortex, but rather only functions to create a score line to facilitate out-fracture for ultimate removal of the block. Full cortical penetration is avoided in the inferior cut due to it s proximity to the mandibular canal in many cases. More experienced clinicans may prefer to make this cut completely through the cortex; however 60 Vol. 2, No. 2 March 2010

17 Figure 28: Block fixated in place and further is mortised with FDBA and PRP. Prior, Intramarrow penetration is made through the block to the underlying receipt bone to provide blood supply to the block. Figure 27: Side view of the block fixated (Note how much augmentation can be achieved). Figure 29: Block is cover with Ossix membrane and flap is released for passive closure and sutured closed. the authors suggest caution with this practice. Once the osteotomies are completed, narrow chisels are used to progressively re-trace each cut and ensure complete cortical penetration. Once again, care must be used to limit chisel penetration to just beyond the cortical layer and to prevent greenstick fracture of the block if out-fracture is attempted too quickly. Careful control of the chisel penetration and angle is critical, since the inferior alveolar nerve lies within the cancellous bone below the ramus harvest area. Next a wider wedge chisel or Potts elevator may be inserted and carefully levered to loosen the block and pry the segment free. A double chisel technique may also be incorporated to facilitate out-fracture while protecting the lingual plate and inferior alveolar nerve from injury (Figures 23-25). Following removal of the bone block, any sharp edges around the ramus area 62 Vol. 2, No. 2 March 2010

18 are smoothed with a round bur or bone file. A hemostatic dressing or platelet rich plasma may be placed into the donor area. Alternatively a particulate bone allograft (such as FDBA) may be placed in the defect as well, especially in the case of large block harvest (Figures 26-28). Closure of the donor area is best completed with an interrupted or running horizontal mattress resorbable suture to evert the wound edges for maintenance of primary closure during healing (Figure 29). Bone Block Preparation, Fixation, and Closure of the Recipient Site The fixation procedure is essentially the same whether the block is sourced from the ramus or the symphysis. A separate basin of sterile saline is used to store the block and make adjustments with rotary burs in a straight handpiece, holding the block firmly using hemostats designed for this purpose (Figure 7). The free bone block must first be shaped and adapted to the recipient site. The block should be adjusted so that it sits flat upon the receipient site without rocking and with intimate contact with the underlying host bone. Care should be taken not to reduce the block extensively in order to achieve this fit, since this sacrifices critical volume of grafted bone. Alternatively if extensive adjustment is required, the recipient site can also be shaped. Once stability and intimate contact has been achieved, the fixation screw sites should be selected and the block should be penetrated in a lagged fashion with a twist drill which is larger than the final screw diameter so that the fixation screw threads will not engage the block, but rather engage only the cortical Figure 30: Incisal view of ramus block post 4 months healing (Note new ridge augmentated for proper implant placement). bone of the underlying recipient site. Use of at least two screws is recommended, since total immobility of the block graft during healing is a critical factor in successful bone integration. 40 The lagged block should be stabilized in place at the recipient site with a large hemostat and the first screw site should be drilled with the appropriately sized twist drill through the first lagged block hole. A periodontal probe may then be placed in the first hole to retain position, and the second screw site prepared. The block is then removed and intramarrow penetration of the recipient site is performed using a small diameter twist drill (1.0mm) to optimize blood supply and new bone formation around the new graft. 41 The smaller twist drill size will allow the surgeon to differentiate between fixation screw sites and penetration sites. The block can then be repositioned and the first screw may then be inserted, but not fully tightened. Once both screws are in place, they may be tightened to ensure the block is stable against the receipient bed. Use caution not The Journal of Implant & Advanced Clinical Dentistry 63

19 Figure 31: Facial view of Ramus block post 4 months healing after fixation screws removed. Figure 32: Implant placed in site #10 in well healed ramus block graft. to overtighten and fracture the block (Figure 8). Additionally, the block itself may be penetrated to facilitate vascular ingrowth, however this is less necessary with symphyseal grafts due the the cancellous base already present. At this time flap release should be performed to ensure passive closure of the graft, and allow time for hemostasis to occur after periosteal releasing incisions, prior to placement of additional particulate graft material and a barrier membrane. Typically conventional periosteal releasing incisions are adequate for closure, however in larger grafts additional use of mylohyoid muscle release, and/or a superficial split thickness flap technique may be necessary. 42 The surrounding area of the block is then mortised with a particulate bone graft, preferably a mineralized graft such as FDBA or anorganic bovine bone, which can be mixed with additional growth factor matrices to improve wound healing and bone regeneration such as platelet rich plasma (PRP), enamel matrix derivative (EMD), recombinant human platelet derived growth factor (rh-pdgf), or bone morphogenic protein-2 (BMP-2) The mortised graft is then covered with a barrier membrane to prevent epithelial and connective tissue ingrowth into the integrating new bone. (Figure 9) The membrane should extend at least 3mm beyond the graft margins. Comparative studies have shown less bone resorption occurs when membranes are used in conjunction with bone block grafts. 32,46 Closure of the recipient site is critical to success in block grafting. Wound dehissence at the recipient site has been associated with more block resorption or complete loss of the grafted bone. Suture used should be of a nonwicking monofilament type, such as eptfe. Passive closure of the crestal incision directly over the block is achieved by horizontal mattress sutures which evert the wound margins, allowing connective tissue upon connective tissue contact. The everted wound margin and the ridge crest is then secured with interrupted sutures along its length at regular intervals. 64 Vol. 2, No. 2 March 2010

20 POSTOPERATIVE MANAGEMENT Postoperative medications are aimed at control of pain, swelling, and infection. Prescriptions of an NSAID and a narcotic pain medication such as hydrocodone and acetaminophen are adequate for pain control in most patients. Continued use of systemic steroid medication (which began preoperatively, as discussed earlier) is recommended for up to 5 days post-operatively. Completion of the tapered methylprednisone dose pack, or 2-3 further days of 12mg per day dosing of dexamethasone are acceptable. 35 Also continued use of a post-operative antibiotic, while controvertial, is warranted for the reasons discussed earlier. Sutures should be retained in place as long as they appear to be providing wound stability, which in many cases is as long as 14 days. 47 If during post-operative followup wound dehiscence is observed with either exposure of the membrane and bone graft or the donor site may occur. Management should include close followup, continued antibiotic coverage, and topical application of 0.12% Chlorhexidine gluconate with a cotton tipped applicator several times per day. 48 These measures will result in either eventual closure of the dehiscence, or progressive dehiscence and loss of the graft and the course of such complications is dependent on close followup. Implant placement After successful initial healing, symphysis and ramus block grafts should be allowed to mature for 4-5 months prior to uncovering and implant placement. 12,20 During the healing phase the block integrity can be evaluated radiographically. Reentry to the block site requires reincision of the overlying tissue, following the same incision lines used in the first surgery. The block stability should be assessed clinically and fixation screws removed (Figures 11, 30-31). Implants can then be placed using the appropriate drilling protocol specified by the implant manufacturer, and restored after sufficient integration time (Figures 12, 13, 32.) Conclusions Alveolar ridge augmentation is a necessity in many cases which present in clinical practice to facilitate adequate bone volume for implant placement. The bone block grafting techniques described here, which integrate the principles of guided bone regeneration, provide a predictable and efficient technique for achieving desired outcomes with a minimum of block resorption and nominal post-operative morbidity. Correspondence: Dr. Nicholas Toscano 116 Central Park South, Suite 3 New York New York Navygumdoc@aol.com Disclaimer: The views expressed in this article are those of the authors and do not reflect the opinion of the Department of Defense or Navy Medicine. The Journal of Implant & Advanced Clinical Dentistry 65

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