8: Hard Tissue Surgery and Bone Grafting

CHAPTER 8 Hard Tissue Surgery and Bone Grafting

ARMAMENTARIUM

GENERAL GUIDELINES

Bone Management

The best protection for bone is an uninjured periosteal envelope. The dangers of overheating bone should also be recognized. Temperatures above 47° C (116.6° F) for only 30 seconds can cause serious, irreparable damage. Staff members must make sure that burs, twist and spade drills, trephines, and bone taps are sharp and are replaced frequently (i.e., depending on bone hardness, after every sixth to tenth implant). After every use, a notch should be made on the shank to keep an accurate count of the number of uses. Replacement drills should always be kept at hand.

Both internal and external irrigation should be used when possible (this feature is not available on all systems), and hollowed drills should be cleaned immediately after each use to ensure future patency (Fig. 8-1). The dental surgeon need not always use the drilling systems supplied by implant manufacturers. Generic consoles, motors, handpieces, and drills are available that offer irrigation systems (which keep endosteal sites cool) and assist the final steps in making osteotomies (see chapters 9 and 10 for specifics). Using drills with 0.5-mm diameter increments results in minimal bone injury and allows the drill to be used a greater number of times.

When performing alveoloplasties, osteoplasties, sinus floor elevations, and bone-tapping procedures, the surgeon must keep a steady, copious source of irrigation on the bone and on all cutting instruments. If the surgeon’s attention must be diverted from the operative site, the site must be kept dressed with saline-soaked sponges at all times to prevent dehydration.

The greatest care must be taken when electrosurgical units are used for implant surgery. Vascularity must be encouraged to ensure the best prognosis for healing. If an electrode tip touches any part of an implant, the current is conducted throughout the entire implant body (although at a dissipated intensity), creating the possibility of widespread bone injury.

Bone grindings should be preserved, when possible, by placement of a filter in the suction system (Fig. 8-2). The recovered osseous coagulum (mixed with a synthetic particulate grafting material, if necessary) can be used for bone repair, after implant placement, or in the floor of the maxillary sinus after an elevation procedure.

Every implantologist should become competent in the use of synthetic bone grafting materials (Table 8-1). These materials offer a number of benefits and may be needed unexpectedly.

Table 8-1 Categories of Grafting Materials

  Advantages Shortcomings
Autografts
(Bone self-donated by the patient)
Iliac crest Patient’s own bone
Osteogenic
Readily available
Second site morbidity
Requires general anesthesia
Prolonged postoperative recovery
Ascending ramus or symphysis of mandible Patient’s own bone
Osteogenic
Readily available
Second site morbidity
Prolonged postoperative recovery
Torus Patient’s own bone
Osteoconductive
Host site availability
Second site morbidity
Cortical bone only
Rib or tibial plateau Patient’s own bone
Osteogenic
Readily available
Second site morbidity
Requires general anesthesia
Prolonged postoperative recovery
Calvarium Patient’s own bone
Osteogenic
Readily available
Second site morbidity
Requires general anesthesia
Prolonged postoperative recovery
rhPDGF-BB
(Highly purified additives derived from recombinant human platelet-derived growth factors [rhPDGF-BB]; used with allografts, xenografts, or alloplasts or alone in a resorbable carrier matrix (Infuse only); used in an infrabony defect or an area where natural host bone is absent but required.
Types: OP-1/BMP-7, GEM-21S, INFUSE)
Bioactive protein
Accelerated growth and bone maturation, more predictable and shows greater bone fill than without
Readily available
Very costly
May not be acceptable to patient
Homografts/Allografts
(Bone donated from a human source other than the patient; obtained from bone banks)
Demineralized freeze-dried bone (DFDB)* Readily available
Osteoinductive/conductive
Biologic acceptability
Replaced by patient’s own bone
Cost
May not be acceptable to patient
Freeze-dried bone matrix Readily available
Osteoconductive
Biologic acceptability
Replaced by patient’s own bone
Cost
May not be acceptable to patient
Irradiated bone Readily available
Osteoconductive
Biologic acceptability
Replaced by patient’s own bone
Cost
Increased concern about disease transmission as a result of decreased processing
Fresh-frozen bone Readily available
Osteoconductive
Replaced by patient’s own bone
Cost
Significant risk of disease transmission and graft-host reaction
Human bone ash (Osteomin) Readily available (Pacific Coast Tissue Bank)
Osteoconductive (human hydroxyapatite [HA])
Resorbable
No risk of disease transmission
Cost
An HA based on human bone
Xenografts
(Mineralized bone matrix from a species other than humans; bovine source)
Bio-Oss Readily available
Osteoconductive
Patient acceptance
Biologic acceptability
Cost
Similar to HA
Alloplasts
(Synthetic bone materials available from a variety of manufacturers)
Nonresorbable polymer (hard tissue replacement [HTR]) Readily available
Osteoconductive
Hydrophilic
Patient acceptance
Biologic acceptability
Cost
Nonresorbable
Ceramic HA
(i.e. Calcitite, Osteograf D, Interpore)
Readily available
Osteoconductive
Patient acceptance
Biologic acceptability
Cost
Nonresorbable (HA component)
Ceramic HA (35%) in a resorbable medium CaSO4 (65%)
(Hapset)
Readily available
Osteoconductive
Patient acceptance
Cost
Nonresorbable (HA component)
Resorbable ceramic
(B-TCP) (i.e., Augmen, Synthograf)
Readily available
Osteoconductive
Acceptable to patient
Biologic acceptability
Cost
Absorbability
Predictability
Ceramic (HA)
(i.e., Osteogen, OsteoGraf LD, OsteoGraf/N)
Readily available
Osteoconductive
Acceptable to patient
Biologic acceptability
Cost
Absorbability
Bioactive glass
(i.e., BioGran, PerioGlas)
Readily available
Osteoconductive
Acceptable to patient
Biologic acceptability
Cost
Absorbability
Bone banks
(See Appendix L for members of the American Association of Tissue Banks.)

* Available in various forms: cortical or cancellous powder, cortical chips, monocortical or bicortical blocks, as a gel in combination with glycerol (Grafton/Osteotech), or in thin cortical sheets to be used as a membrane (Lambone/Pacific Coast Tissue Bank).

Grafting for repair, augmentation, osteosynthesis, or morphologic maintenance may be performed with autogenous or allogeneic bone, xenografts, or synthetic versions (particulate or porous solid block forms) of both resorbable and nonresorbable osteoconductive biomaterials. Table 8-2 presents the names and other significant characteristics of these grafting materials. The techniques for their use are essentially the same for all, except that some have different handling characteristics. Indications differ for the use of some of the synthetic bone materials (i.e., TCP and other resorbable substances). The clinician may be able to change both the quantity and quality of a patient’s bone by using bone-replacement materials.

Table 8-2 Guided Tissue Regenerative Membranes (GTRMs)

Name Material Resorbable or Nonresorbable Manufacturer Advantages Shortcomings
Gore-Tex Expanded polytetrafluoroethylene (e-PTFE) Nonresorbable W.L. Gore & Associates Proven track record
Established good standard
Available with titanium reinforcement variations
Nonresorbable, requires removal surgery
Exposure results in inflammation possibly less favorable results
TefGen-FD Nonexpanded PTFE Nonresorbable Lifecore Biomedical Some clinical studies suggest primary closure not 100% necessary
Nonporous surface inhibits bacterial colonization
Nonporous structure may result in increased exposure
Nonresorbable
Regentex TXT-200/GBR-200 Nonexpanded PFTE Nonresorbable Osteogenics Biomedical Some clinical studies suggest primary closure not 100% necessary Nonporous structure may result in increased exposure
Nonresorbable
Cytoplast Ti-250 Titanium reinforced     Nonporous surface inhibits bacterial colonization  
Biobarrier
AlloDerm GBR
PFTE
Acellular dermal matrix
Nonresorbable
Resorbable
Imtec
Biohorizons
Resorbable
Primary closure not 100% necessary
Enhanced soft tissue quality and esthetics
Somewhat technique sensitive
Bio-Mend
Bio-Mend–Extend
Bovine type I collagen Resorbable Sulzer Calcitek Resorbable Difficult to manipulate when wet
BioGwide Porcine type I and type III collagen Resorbable Osteohealth (Approved by the FDA for use around implants) Resorbable Short track record
Vicryl mesh Polyglactin 910 (9:1 ratio of polylactic acid to polyglycolic acid) Resorbable Ethicon Resorbable
Easy to position and place
Easily collapsible into defect
Resolute XT Polyglycolide and Polylactide polymers Resorbable W.L. Gore & Associates Resorbable
Retains form once shaped
Stiff, difficult to bend and adapt
Ossix Plus Porcine collagen Resorbable Orapharma Resorbable
Easy to position and place
Must be rehydrated in saline for 5-15 min
Atrisorb Poly DL–lactide in N-methyl-2-pyrolidone Resorbable Block Chairside fabrication
Resorbable
Mildly adherent to tooth
Short track record
Learning curve
Can be difficult to adapt
Lambone Freeze-dried demineralized allogenic laminar bone sheets Replaced by bone Pacific Coast Tissue Bank Replaced by bone
Available in variable thickness
Must be rehydrated in saline for 5-30 min
Thicker pieces more difficult to adapt
May not be acceptable to patient
Capset Calcium sulphate Resorbable LifeCore Resorbable
Custom adapted at time of placement
Does not require bone tacks or suturing
Somewhat technique sensitive

GBR, Guided bone regeneration; FDA, U.S. Food and Drug Administration.

An essential aspect of the application of grafting materials is the use of resorbable and nonresorbable guided tissue regenerative membranes (GTRMs). A small but stalwart contingent of practitioners remains loyal to the traditional nonresorbable designs, but those materials offer no advantages over the resorbable type, and they require a second operation for removal.

The first part of this chapter presents the more basic procedures of bone grafting, such as ridge maintenance, ridge augmentation, and the general application of membranes and techniques for their fixation. This background serves as a guide for the second part of the chapter, which describes bone alteration and grafting techniques designed for ridges with dimensional deficiencies that prevent routine implant procedures. The methods of selecting donor sites and obtaining grafts also are discussed.

Basic Grafting Procedures

Periodontal Defect Correction

Only teeth that are or can be made clinically firm should be included in the treatment plan. If the teeth are mobile, they must be bonded with stainless steel wire or acrylic intracoronal splints or in some other fashion completely immobilized. If periodontal-endodontic involvement is a possibility, presurgical pulp canal therapy must be performed (Figs. 8-3 and 8-4).

Flaps should be planned carefully, and incisions should be made at least one tooth anterior and one tooth posterior to the anticipated surgical site. Crevicular incisions should be made with a No. 12 blade using the inverted bevel design, so that involved epithelium and granulomas are left in situ, which facilitates excision. The crevicular incisions are connected with those that are vertical and/or oblique. The flaps should be widest at their vestibular bases. Papillae should never be split; rather, they should be included entirely within the flap (Fig. 8-5).

Flaps are reflected with great care so that they are not torn. A sharp, fine periosteal elevator or sharpened No. 7 wax spatula is useful. The alveolar bone need not be exposed any more than 1 to 2 mm apically beyond the periodontal defect. Serious postoperative sequelae occur (e.g., pain and swelling) when reflections extend apically beyond the attached gingival level. Of course, depending on anatomic factors and pocket depth, reflection may need to extend beyond the vestibular attachments.

After facial and lingual flaps have been reflected, impeccable care must be taken to curette and plane all exposed root surfaces. The bone should not be blunted, ramped, or altered in any way. The higher the residual walls, the better the prognosis for osseous repair with graft materials. Cortical perforations can be made with a No. ½ round bur for additional sites for retention.

Hemostasis must be achieved to ensure particle stabilization; however, slight bleeding is important, because blood is necessary for particulate incorporation and to encourage osseous repair. Active bleeding, on the other hand, often washes the new graft material away. Periodontal particulate graft material should be a fine grain size (40 mesh or 250 to 350 μm in diameter). When mixed with the patient’s blood and allowed to remain in a dappen dish for 15 minutes, the material should take on a texture that allows easy handling. It clumps quite naturally and reliably remains in position. Of course, improper condensing, poor suturing, brisk bleeding, or incorrect operative design (e.g., defects without walls) may be responsible for a less-than-perfect result.

When the operative site is absolutely free of granulomas, plaque, and calculus, the graft material can be placed in the defect. It can be delivered with a nylon-tipped amalgam carrier; the old-fashioned, all-plastic, back-end plunger type, kept sterile and reserved for grafting use, is preferable.

After the graft material has been placed in the furcation or against one of several (at least two) remaining bony walls and tamped with a moistened cotton applicator, firm pressure is applied until fibrin becomes incorporated into and stabilizes the particles (Fig. 8-6). Suturing should follow, using 4-0 violet-dyed polyglactic acid or glycomer on a cutting needle (see Chapter 6). Watertight closures that replace each papilla accurately are mandatory to ensure particle fixation (Figs. 8-7 and 8-8).

When a bony peri-implant defect is adjacent to an edentulous area, classic wedging is performed. After a full-thickness flap has been reflected, the pocket and opposing implant surface are treated as described in the section on failing implants in Chapter 28. Then, a spatula osteotome, placed at the ridge crest and 3 to 4 mm from the lesion, is tapped gently with a mallet to a depth equal to that of the pocket. The osteotome is directed inferobliquely toward the failing implant. When the osteotome reaches the depth of the defect, it is used as a lever to mobilize the new triangle of bone. The wedge is pushed against the denuded implant surface and maintained in this position by pressing some nonresorbable, 40-mesh HA particles into the donor site that supplied the triangular graft. Simple closure completes the procedure. Pocket measurements should not be attempted for at least 3 months, and even after that, they should be attempted only with great care (Fig. 8-9).

If the patient’s and practitioner’s expectations are realistic, and the home and office care regimens meet the stringent requirements of most periodontal systems, the results can be quite pleasing (Fig. 8-10). If GTRMs are used, the grafting of peri-implant and other defects mentioned in this and other chapters becomes simpler and is more successful (see Table 8-2).

Use of Resorbable and Nonresorbable Guided Tissue Regeneration Membranes

The use of membranes to cover osseous repairs does not automatically ensure an improved prognosis. In fact, improper use may result in delayed healing, breakdown of the suture line, and a compromised operative site. A wide variety of membranes is available. Before selecting one, the surgeon must decide whether a particular choice would be beneficial.

Essentially, membranes are used in the following situations:

If the operated area presents no irregularities and closure can be accomplished without tension, membranes should not be used.

GTRMs may be applied with or without bone-grafting materials for perforations of the cortical plates, saucerization phenomena (Figs. 8-11 through 8-18), thin ridges, exposed implant cervical areas, other intraosseous defects, voids that remain after implants have been placed in immediate extraction sites, and ridge maintenance after extractions with accompanying synthetic grafting materials.

Some membranes require rehydration, and others have a crystalline or granular composition; some are grossly porous, whereas others are microporous or nonporous.

The resorbable membranes generally are polymers that hydrolyze over time (usually about 40 days). A homologous resorbable membrane that serves as more than just a barrier is laminar bone, which is retrieved from human specimens and treated with demineralization and sterilization techniques.

The nonresorbable groups are synthesized. They most often consist of polytetrafluoroethylene (PTFE) or nonporous or microporous material. They may require primary soft tissue coverage (i.e., Gore-Tex), or they may be used without the wound flaps coming into direct contact, allowing the membrane to be exposed (i.e., TefGen or Cytoplast GBR 200). The surgeon must make the choice. The decision is influenced by the surgeon’s familiarity with the product, its ease of use, the cost, compliance, and the desire to avoid a second or retrieval operation.

Membranes require reliable fixation. In most instances, undermining the surrounding mucosa and wedging the membrane periphery firmly beneath it satisfies this requirement. If this technique is not practicable, membrane tacks or miniscrews can be placed at strategic sites. Ordinarily, the device (membrane, slurry, or laminar bone) should fit intimately over the operative site. Its purpose is to discourage epithelial ingrowth, and an accurate adaptation helps prevent this. Tucks and alterations are made when indicated; these maneuvers are completed, and the ability to achieve primary flap closure is determined before the graft material is placed. If not performed in advance, membrane manipulations and flap undermining disturb the stability of particulate graft material. On completion of the operative procedure and graft placement, the precontoured membrane is slipped back into position, fastened and tucked as needed, and a primary closure is performed.

At sites that require dimensional enlargement, the guided tissue device must be “tented.” This sometimes is a challenging procedure, particularly when a soft or compliant membrane is used. Contour corrections are most readily made with firmer devices, such as laminar bone or Gore-Tex with titanium reinforcement. Of course, a less stiff membrane is required when it is supported by underlying graft material.

To enable the GTRM to fulfill its function, which is promoting bone proliferation into a defect, a space equivalent to the area that needs filling must be left beneath the membrane. With saucerization defects and similar problems, this space occurs quite naturally, because the lesion’s peripheral bone margins keep the membrane in a tented configuration. With cortical plate perforations, protruding implant apices or bodies, and knife-edge ridges, however, graft material must be used in block or particulate form, and the membrane is placed over it.

Before using any graft material, the surgeon must eliminate all residual infection, treat the implant appropriately (see Chapter 28), and make sure that adequate tissue is available for primary closure with mattress sutures.

Incisions should be crestal, not S-shaped or visor type, to protect the vascularity of the flaps.

After the site has been exposed adequately (4 to 5 mm of normal bone on all sides of the defect), a membrane of the closest proper size is selected, and sharp scissors are used to trim it to fit competently over the entire area. Sharp corners must be avoided, and a 3-mm overlap must be created to cover adjacent cortex. If a natural tooth exists adjacent to the operative region, its periodontal space is circumvented. The GTRM is tailored with precision. If space beneath the membrane is required, a selected bone-grafting material is chosen and firmly tamped into position, and the membrane is then implanted (Figs. 8-19 through 8-29). If a convex configuration is required, one or several nips and tucks are made to allow an additional dimension to be formed. Fibrin should be allowed to maintain it in its new shape before closure.

Fixation of the GTRM before wound closure is essential to the ultimate success of bone-generation procedures. The peripheral margins of the membrane may be wedged gently beneath the periosteum or even sutured with an absorbable material to the periosteum at strategic peripheral locations. Small fixation tacks are available from Steri-Oss, and in most maxillae, they can be forced into the bone with finger pressure. These sharp, titanium tacks are available in a set that includes an instrument that grasps a tack’s head and carries it to the site where the membrane is to be stabilized. The mandible, which has a denser cortex, usually does not yield to the sharp point of the tack unless a preliminary bur hole starts the process (the bur is supplied in the kit), followed by a few light mallet taps applied to the end of the seating instrument (Figs. 8-30 through 8-35). Additional tack and screw systems are supplied by Straumann, 3i, Ace Surgical, and others.

If the repair area is pericervical and the ailing implant has a healing screw, a hole is cut in the membrane with a diameter that is only large enough to allow entry of the threaded portion of the screw. After the graft material has been placed, the GTRM is positioned poncho fashion, and the cover screw is tightened to anchor it firmly (Figs. 8-36 and 8-37).

Closure is done with polyglactic sutures using the horizontal mattress technique. Care must be taken to ensure that the membrane does not become wrinkled, that it is firmly fixed, and that its rounded margins extend well beyond the defect on the cortical bone. The overlying flaps should not be sutured under tension (see chapters 6 and 7), and an absolute primary closure must be achieved (Figs. 8-38 through 8-42).

The sutures are removed after 7 to 10 days or allowed to resorb. If the selected membrane is nonresorbable, it can be removed at any time after 3 months. If allowed to remain longer, the intimate relationship of the overlying soft tissues to the membrane may make removal troublesome and threaten the integrity of the mucosa.

If the membrane becomes exposed because of a dehiscent suture line, the prognosis becomes less positive; however, the membrane’s continued presence should be encouraged by gentle Peridex irrigation and debridement. The patient should be taught to practice this on a daily basis between professional visits. Bone regeneration may take place successfully despite the wound’s loss of integrity.

Ridge Maintenance

In most cases, maintaining the alveolar ridge morphology after dental extractions is a worthy preventive measure and may offer patients the ridge form, height, and shape that make denture fabrication simpler and more successful and fixed prosthesis pontic construction more realistic looking, hygienic, and comfortable. In addition, if implants are planned, larger and more generous host sites may be available in which to place them.

Maintenance procedures may be more immediately and tangibly valuable to a patient in two circumstances: after mandibular third molar extraction and after molar hemisection procedures. In the latter case, endodontic therapy must be performed on the planned residual root before sectioning. In both cases, grafting prevents the potential hazards of significant bone loss to adjacent teeth and spares a predictable array of periodontal complications. In each situation, the technique of placing particulate graft material and membrane at a deficit site is performed by completing the extraction with preservation of as much bone as possible. Sectioning molars makes this goal easier to achieve. The vacated sites are debrided thoroughly, all granulomas and epithelia are removed, and fresh bleeding is encouraged. The 20-mesh graft material (650 to 850 μm in diameter) is introduced by syringe or periosteal elevator and tamped firmly to eliminate spaces. Then, after overlapped bone is covered with a membrane, the procedure is completed with primary closure. If tissue is inadequate, interdigitation of facial and lingual papillae often solves the problem.

IMPORTANT NOTE

To avoid packing graft material into the antrum or mandibular canal, the surgeon should determine whether an opening has been made into one of these structures. (Chapter 28 presents the symptoms of antral or canal penetration.) If such a finding is confirmed, or even suspected, a piece of Colla-Cote or Colla-Plug is tailored to fit the defect and laid or tamped gently at its base with a saline-moistened plug of cotton. This serves as a protective dam, against which the particles can be placed. Bleeding must be controlled before implantation, or the graft material will be carried away. Tamponade is a sound maneuver for achieving hemostasis and stabilizing the fibrin-particulate slurry.

Next, the extractions, hemisections, or impaction removals are performed in the usual manner, with care taken to preserve as much of the bony socket as possible (Figs. 8-43 and 8-44).

The operative sites are inspected carefully. All forms of follicles, cysts, and granulomas are eliminated by sharp dissection with a No. 12 or No. 15 blade (described in Chapter 6); this is followed by aggressive application of periodontal and surgical curettes.

When clean, bony beds are evident, the flaps’ ability to close primarily over the entire operative site must be confirmed. If the flaps do not come together anatomically, an attempt should be made to slide the facial and lingual flaps one-quarter tooth in opposite directions from one another. This often allows the papillae to interdigitate into a sawtooth relationship. Bone is valuable and should not be removed to allow the flaps to close. The buccolingual plates are necessary for long-term maintenance of ridge width and height. The graft materials alone cannot supply the area with bone, nor will the achieved level result in a dimension greater than the highest level of bone. If all else fails, the surgeon must use the undermining technique to achieve primary closure (see Chapter 7). When primary coverage capabilities have been assured or created, the assistant should retract the flaps to allow irrigation, debridement, and hemostasis.

Depending on the size of the defect, a special syringe or amalgam carrier may be used to deliver the graft materials (Fig. 8-45). If the plan is to use a particle-loaded syringe, moisture is added to the material while it is still in the barrel. A nonvasoconstrictive local anesthetic solution, sterile saline, or the patient’s blood can be used for this purpose. Blood derived from bone marrow appears to offer greater possibilities of osteogenesis than peripheral blood. In addition, it is easier and more convenient to aspirate blood with a 3-mL syringe (without a needle) from a bony wound than from a phlebotomy.

A simple method of moistening the graft material is to place the chosen diluent in a sterile dappen dish and add the particles of graft material. Then, an amalgam carrier or the blade of a periosteal elevator is used to carry the mixture to the host site, where it can be tamped firmly into the defect (Fig. 8-46). In an alternative method of wetting the particles, the plunger of the syringe with the graft particles is withdrawn almost to the breach of the barrel; then, while the syringe with the graft particles is held in one hand, the blood or fluid has been withdrawn and stored in a separate syringe, the blood or fluid then is injected with a fine needle that has been inserted directly into the syringe with the particles (Fig. 8-47).

The syringe or carrier remains untouched for 2 to 3 minutes. Then, gently but firmly, a slurry of particles is introduced into each well-controlled, well-visualized defect, to a level just to the highest point of bone. The particles are tamped with a moistened cotton applicator to condense them. The surgeon must confirm that blood has impregnated the entire mass. Closure is best accomplished with a continuous box-lock technique using 4-0 dyed polyglactic suture. Stable hemostasis is confirmed before the patient is dismissed (Fig. 8-48, A and B).

Also before the patient is dismissed, the surgeon should take well-oriented, long cone, standardized, reproducible radiographs, because a baseline must be established for future comparisons of particle retention and host site density and morphology.

Prosthodontic work should wait until at least 12 weeks have elapsed. If endosteal implants are to be placed in these ridges, 6 months are allowed for osseous maturation (Fig. 8-49). Also, if endosteal implants are planned for the grafted sites, nonresorbable HA cannot be used, because it prevents precise, effective drilling for implant placement. Instead, the surgeon should use a resorbable ceramic (TCP, osteogen), an allograft (DFDB), a xenograft (Bio-Oss), an alloplast (hard tissue replacement [HTR]) or, preferably, autogenous bone from a nearby tuberosity.

Ridge Augmentation

Even if a ridge has not been maintained with grafting materials at the time of extractions and is found to be resorbed, it can be augmented with a natural or synthetic biomaterial. Flat, atrophied, or knife-edged ridges can be treated with a variety of resorbable and nonbiodegradable materials (see Table 8-1). These materials are available in two forms, particulate (syringe loaded) and porous block. They can be inserted either by a “closed” technique (i.e., tunneling) or an “open” technique (incision, flap creation, and flap reflection). Each approach has its advocates, and both forms have their proponents.

From a surgical point of view, tunneling would seem to be less invasive and certainly faster. Fewer sutures are used and much shorter incisions are made, and closure is not done over or even near the implanted allograft. However, other factors may influence the selection of this surgical approach. If the mandibular canal appears to be dehiscent radiographically or the mental foramen is seen to be less than the width of the periosteal elevator blade from the ridge crest, the potential exists that tunneling will result in an iatrogenic neuropathy. In such cases, open procedures are safer, because vital structures can be seen and avoided.

Tunneling Technique

The following steps are used if a closed procedure is chosen for the mandible.

2. If the ridge is high but knife edged and the mentomandibular bundles are well below the crest and encased in canals, a vertical incision is made in the labial gingiva of each canine area from crest to vestibule (Fig. 8-50). The dimensions of the incision must be sufficient to admit the wide end of the periosteal elevator and the muzzle of a delivery syringe or an augmentative block.

Rigid blocks are soaked in a mixture of the patient’s blood and an aqueous antibiotic solution (e.g., 80 mg of gentamicin in 10 mL of sterile saline) for 20 minutes before implantation. The collagen vehicle cannot be treated in this fashion, because it allows the block to become soft before insertion, which impedes placement.

The major disadvantage of rigid porous blocks is that if dehiscence occurs and causes exposure of even the tiniest portion of the block’s surface, the chance of preserving the block or even a part of it is lost. No matter how aggressively surgical efforts are made to salvage a dehiscent porous block, they will fail. Exposure requires removal of the block.

Autogenous bone blocks from the ribs or iliac crest or precut DFDB slivers or wedges from the Pacific Coast Bone Laboratory offer the best chances for success.

8. If the particulate form of graft material has been chosen, the tunnel opening is elevated and retained with a suture or toothed Gerald or Adson forceps. After the particles have been moistened (and the breech cap, if present, has been removed), the barrel of the syringe is inserted into the tunnel to its most distal extent (Fig. 8-52). The plunger is stabilized with the opposite hand as the barrel is withdrawn; this allows extrusion of a smooth, symmetric, blood-soaked, cylindric slurry of particles, which is deposited in the center of the tunnel. Care must be taken not to make the tunnel larger than the minimal size required to accommodate the syringe or to allow it to penetrate beyond the vestibular attachment. Impeccably made tunnels determine the stability of the particles after implantation and, ultimately, the success of the graft (Figs. 8-53 and 8-54).
9. If a block is planned, the lip of the tunnel is retracted. A rongeur forceps is used to trim the block to the correct size (Fig. 8-55). Blocks may not be ground or adjusted with rotary instruments, because grinding clogs the surface pores. The surgeon slides the block into place by pushing it gently with a cotton-tipped applicator, and it is maneuvered into position using the thumb and forefinger on the overlying tissues (Figs. 8-56 through 8-58).
Jan 5, 2015 | Posted by in Implantology | Comments Off on 8: Hard Tissue Surgery and Bone Grafting
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