Periodontobgv 2000, Vol. 1. 1993, 92-99 Printed in Denmark . All rights reserved

Copyright 8 Munksgaard 1993

PERIODONTOLOGY 2000 ISSN 0906-6713

Svnthetic bone grafts in periodontics RAYMOND A. YUKNA

History of bone grafts in periodon tics

The reconstruction or restoration of osseous defects caused by inflammatory periodontal disease is a con- tinuing challenge in periodontal therapy. Although many attempts have been made to regenerate al- veolar bone support and the attachment apparatus, predictable success has proved elusive. Historically, autogenous and/or allogeneic bone graft materials have been used with moderate clinical success (9,15, 18). Osseous grafts are the only type for which ample histologic evidence is available of periodontal recon- struction in humans, including new cementum, al- veolar bone and a functional periodontal ligament (3, 5). Despite the success demonstrated with trans- plants of osseous material, however, the use of such grafts is frequently either impractical or impossible. I t is often difficult to procure sufficient autogenous bone and there is some concern about the possibility (albeit remote) of disease transfer with freeze-dried bone allografts.

The ideal graft material remains to be found. Such a material would induce osteogenesis and cemento- genesis that would result in regeneration of a new periodontal attachment complex at a more coronal level. I t would be completely biocompatible and would not be carcinogenic, toxic or antigenic or ef- fect round-cell infiltration responses. It would also be easily obtainable, relatively inexpensive and would not cause the patient or the therapist un- necessary inconvenience.

Development of synthetic bone graft materials

An inorganic synthetic material would seem to fulfill the criteria for an ideal graft material. Several allo-

plastic implant materials have been used in an attempt to improve clinical conditions and regener- ate bone in periodontal infrabony defects (Table 1). The most successful of these materials have been cer- amics of either the bioresorbable or nonresorbable type.

Early studies using calcium phosphate materials focused on the principle that local release of calcium ions would stimulate bone formation at the site. These early studies with soluble calcium powders yielded equivocal results and led to further studies with tricalcium phosphate (19, 20) and modified forms of hydroxyapatite (12, 14, 16, 21, 22).

Clinical results with synthetic graft materials are essentially similar to results obtained with autogen- ous or allogeneic materials, both in direct or com- parative studies and in cross-sectional comparisons of similar evaluations or studies. The choice of ma- terial then becomes based more on availability, cost, morbidity and ease of handling than on clinical su- periority.

The available doplastic materials can be classified generally as resorbable or nonresorbable. In general terms, plaster of Paris, calcium carbonate, tricalcium phosphate and resorbable hydroxyapatite resorb tot- ally or partially in oral and periodontal surgery sites and the polymers and dense hydroxyapatites do not.

Table 1. AlloDlastic graft materials Plaster of Paris Polymers Calcium carbonate Ceramics

Resorbable 'I'ricalcium phosphate Resorbable hydroxyapatite

Dense hydroxyapatite Porous hydroxyapatite Bioalass

Nonresorbable

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Fig. 1. a Bony defect on distal of mandibular right canine after debridement. This was grafted with dense hydroxy- apatite. b. Re-entry showing bone fill 6 months after graft- ing. c. Preoperative radiograph. d. Postoperative radio-

graph taken 6 months after grafting. Reprinted with the permission of W.B. Saunders Co. Source: Levine N. Cur- rent treatment in dental practice. 1986, p. 266.

There is some controversy as to which of these bio- logic results is preferable in dental usage, and selec- tion of one type or another may depend on the actual clinical application. All of the commercially available alloplastics listed, except plaster of Paris, have a par- ticle size between 300-500 pm in diameter. This par- ticle size is felt to be optimum for periodontal usage (25).

Animal and human wound-healing studies have uniformly demonstrated the biocompatibility of the listed materials. A lack of local or systemic toxicity, a lack of inflammatory or foreign body response, and the ability to become directly bonded to bone are all positive attributes of these materials (2, 7, 8, 11, 13, 23, 24).

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Rationale for the use of synthetic grafts in periodontics The decision to use alloplastic grafting materials dur- ing surgical periodontal treatment is made on the same basis as the decision to graft in the first place. Practitioners with advanced training or extensive ex- perience in periodontal surgical techniques and who entertain a reconstructive philosophy are likely users of synthetic or other bone-grafting materials.

Periodontal bony defects are treated because they complicate the definitive elimination of active pocket defects, compromise the support of the tooth and the tooth’s ability to withstand functional stresses and complicate maintenance of an arrested pocket de- fect. The ideal result is correction of bony defects by regeneration of lost supporting bone and periodontal ligament (Fig. 1).

At the present time, bone replacement grafts are the only modality of therapy for which there is histo- logic evidence, in humans, of regeneration of new attachment composed of new bone, cementum and periodontal ligament coronal to the base of a pre- vious osseous defect (3). This does not imply that all bone replacement grafts are uniformly successful, routinely predictable or will heal with restoration of the entire attachment complex. Partial repair often occurs with adherence of a long junctional epithel- ium to the root surface andlor adhesion of connec- tive tissue fibers oriented pardel to the root. Never- theless, regeneration of a complete new attachment occurs frequently enough with bone replacement grafts to warrant their use in selective cases. Guided tissue regeneration techniques, on the other hand, do not appear to routinely induce the formation of periodontal supporting bone (1, 10). Furthermore, there is evidence that supracrestal bone regeneration is possible when certain bone replacement grafting materials are used. This has not been observed with other forms of regenerative periodontal therapy, which attempt to eliminate bony defects without a bone replacement graft material (4, 17).

The indications for using alloplastic bone replace-

ment grafts as part of surgical periodontal pocket therapy include: 0 Deep infrabony defects associated with chronic in-

flammatory periodontal disease. While narrow 3- wall defects may respond equally well to grafting or debridement (flap curettage) alone, the response of wide 3-wall, 2-wall, 1-wall and combination de- fects is enhanced by the addition of alloplastic grafts compared with nongrafted controls.

0 The need for increased bone support for a tooth. Such procedures may restore sufficient functional stability to make the tooth an acceptable abutment for restorative dentistry and preserve arch integrity.

0 Localized juvenile periodontitis lesions, because they have shown consistent success when treated with alloplastic grafts. Their use in this condition has eliminated the wholesale extraction of involved teeth and has often regenerated almost the entire amount of previously lost support (6).

0 Maintenance of an aesthetic gingival margin height. If periodontal pockets associated with shal- low bone defects are treated by osseous resection and apically positioned flaps, the longer clinical crowns may be aesthetically unacceptable. Recon- struction of these defects with alloplastic grafts and the subsequent retention of the gingival margin close to the cementoenamel junction may preserve aesthetics.

Alloplastic grafts are indicated for the patients who have the time for a rigorous treatment regimen and postsurgical maintenance program. The use of such grafts is also dictated by patient acceptance, financial factors, availability of graft material, past experience with bone-grafting procedures, case selection, etc. The therapist’s lack of clinical experience often leads to discouraging results. Moreover, bone replacement grafts are only indicated when the patient has met the therapist’s criteria for case selection.

Case selection is particularly important to the use and success of bone replacement grafts. The patient must be highly motivated and denionstrate the abil- ity to effectively remove bacterial plaque from every surface of every tooth on a daily basis. Baseline rec- ords and a plaque index are essential in determining

Fig. 2 (page 95). Series of photographs in a nonhuman primate showing the technical steps in bone replacement grafting with hydroxyapatite. a. Mucoperiosteal flap reflected to obtain access. b. The bone defect on the mesial of the maxillary first molar is curetted free of soft tissue and root surfaces are meticulously scaled and root-planed. c. Flaps are presutured prior to placement of graft material. d. Graft material is placed in bony defects. e. The graft material (hydroxyapatite) is placed in increments and condensed to completely fill the bony defect. f. Flaps are replaced and sutured to obtain primary closure. Reprinted with the permission of W.B. Saunders Co. Source: Levine N. Current treatment in dental practice. 1986, pp. 263-265.

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the patient’s progress. The patient’s attitude toward therapy must be positive. Treatment should be per- sonally accepted as a worthwhile investment of time and effort. The patient’s gingival tissue response to initial preparation should indicate some resolution of inflammation. Likewise, the patient’s age, health and emotional status, social habits such as smoking and tolerance for lengthy dental appointments are important considerations. These criteria wiU limit the number of patients who are good candidates for re- generative therapy. Unless these factors are favor- able, the clinician invites failure and alloplastic grafts may be contraindicated.

Bone graft technique

The general surgical technique used in periodontal bone replacement grafting uses many of the same basic, tedious, painstaking procedures used for other forms of periodontal surgery. Although they do not guarantee success, the following steps in the pro- cedure provide a road map that leads toward success most the time. 1. Remove all etiologic factors. Local and systemic

factors must be under control for grafts to be suc- cessful. This control would optimally have been accomplished presurgically.

2. Stabilize teeth if necessary. Generally, temporary, provisional or permanent stabilization of teeth undergoing grafting is not necessary. Teeth with slight to moderate mobility appear to heal just as well whether splinted or not. However, extremely mobile teeth that are going to be treated may benefit from provisional stabilization for at least 6 months postsurgically. At the very least, this stabilization allows for proper control of the oc- clusion and the performance of therapeutic measures such as root planing.

3. Flap design with a plan for closure. Internally be- veled scalloped incisions with full gingival pres- ervation are necessary to be able to completely close the site at the completion of surgery. Full thickness flaps, reflected beyond the mucogingi- val junction, are recommended (Fig. 2a). Vertical releasing incisions should be used as necessary for proper access to the defects.

4. Degranulation of defect and f lap . All granulo- matous soft tissues should be removed from the bony walls of the defect and the associated tooth surfaces (Fig. 2b). The inner aspect of the flap should be checked for tissue tags and epithelial remnants, and these should also be removed.

~ ~~~ ~~ ~~~

5 . Root preparation. It is essential that all calculus, bacterial plaque, other soft debris and altered ce- mentum be removed from the involved root sur- faces. Ultrasonic and hand instruments as well as finishing burs are useful for this purpose. This aspect of therapy is the most tedious, difficult and time-consuming of the entire procedure (Fig. 2b). It is also the most essential aspect. There is some suggestion that the use of chemi- cals such as citric acid or tetracycline paste may be an aid in root detoxification and in making the root surface more biologically acceptable for healing.

6. Encourage a bleeding bony surface. This is gener- ally already accomplished by proper defect de- bridement (Fig. 2c). However, if the defect walls are relatively dry and/or glistening, healing may be enhanced by intramarrow penetration to en- courage bleeding and allow the ingress of repara- tive cells, vessels and other tissues. Such penetra- tions can be accomplished with a small round bur or hand instruments.

7. Presuturing. Loose placement of sutures, left un- tied, prior to the filling of the defect reduces the possibility of displacing the graft material during the suturing process (Fig. 2c). It also simplifies the last steps of the procedure, in that once de- fect fill has been completed, the already placed sutures need only to be tied to complete the sur- gical procedure.

8. Condense grafi materials well. The commercial availability of alloplastic materials eliminates the problem of not having enough graft material. The graft material should be placed in small in- crements (Fig. 2d). Useful in this regard are ster- ile plastic or Teflon-lined amalgam carriers to place the material and sterile amalgam squeeze cloths to use over the suction tip to dry the defect without removing any of the graft material. Small increments of material are placed in the defect, gently packed into the angles and base of the defect with small pluggers or curettes, and dried with the squeeze-cloth covered suction tip. The process is repeated until the defect is filled (Fig. 2e).

9. Fill to a realistic level. Except in unusual circum- stances, defects should be filled with the syn- thetic graft materials only to the level of the de- fect walls, There is little suggestion that overfilling with these materials results in supra- crestal bone formation. Overfilling may actually be counterproductive in that it may preclude proper flap closure, thereby retarding healing

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and possibly resulting in loss of the graft ma- terial.

10. Good tissue coverage. If flap design (item 3) has been good, primary closure with replaced flaps and contact of the interproximal papillae can usually be obtained (Fig. 20. If tissue coverage of the alloplastic graft material is not satisfactory, additional releasing incisions or reflection may be necessary. Another possible treatment is the use of an autogenous free gingival graft or freeze- dried skin or dura mater allograft to cover the bone graft site.

11. Periodontal dressing. The use of a firm, protective

periodontal dressing for 10 days following bone replacement graft surgery is suggested. An anti- biotic ointment under the dressing to help seal the area may be useful. It has become popular not to use dressing for many periodontal surgical procedures, but prudence would seem to suggest that the possible impingement of foreign ma- terials into the graft site, flap displacement and loss of graft material that would jeopardize the success of treatment make the use of protective dressings preferable.

12. Antibiotic covercage. A growing body of research data lends support to empirical clinical use of

Fig. 3. Wide 3-wall circumferential defect lingual to tooth No. 29. Defect depth=5 mm. a Surgical exposure of defect. b. Hydroxyapatite placed with slight overfill. c. Surgical re- entry at 6 months demonstrating complete resolution of defect. Amount of fill=4 mm. Resorptiond mm. Tooth has reduced mobility and still serves as abutment for the same removable partial denture. d. Original pretreatment radio- graph. e. Radiograph prior to surgical re-entry at 6 months. Reprinted with the permission of Journal of Peri- odontology 1981: 52: 680-689.

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13.

antibiotics perisurgically when bone grafts are used. Tetracycline-type drugs are the antibiotics of choice for immediate postsurgical plaque sup- pression due to their broad spectrum of activity, attraction to healing wound sites and concen- tration in gingival crevicular fluid. They are ad- ministered in therapeutic doses for the first 10 days following surgery or until the patient can practice proper plaque control in the area. Posrsurgical cure. If the dressing and sutures are removed prior to 10 days, another dressing is often indicated. When the first postoperative treatment is at 10 or more days following surgery, additional dressings are rarely indicated. The pa- tient is started immediately on gentle but thorough plaque-control methods, including the use of antibacterial rinses, and is scheduled for professional plaque control in the office as fol- lows: 0 every 10 days for 3 visits; 0 every month for 2 visits; and 0 every 3 months, perhaps alternating with the

referring dentist. At these visits, a plaque score is taken and oral hy- giene procedures are reviewed with, demonstrated to and practiced by the patient. The patient is rendered plaque-free by office personnel prior to leaving the office. Occasionally, the grafted area may be lightly curetted to help with debridement and retard epi- thelial downgrowth. The grafted areas should not be probed prior to 3 months postsurgically, and radio- graphs taken prior to 6 months provide uncertain information.

Results using synthetic graft materials

Company-generated and independent research re- ports have consistently demonstrated positive clin- ical results with synthetic graft materials similar in magnitude and frequency to those obtained with other graft materials. A mean defect fill of about 60-70% has been shown with all the listed materials (Table 1) with no essential difference between them (Fig. 3) (14, 16, 21, 22, 23). The research reports also show that failures occur about 10% of the time. Com- plete defect fills also occur with about the same fre- quency. These findings indicate that grafting with al- loplastic materials is not universally successful but does offer the prospect of positive clinical results for the majority of defects in the majority of patients. The partial success often achieved may be the only

treatment needed or may allow additional therapy such as additional grafting or osseous recontouring to further reduce the defect.

The use of bone replacement grafts in periodontics provides the most predictable possibility of regenera- tion of the entire periodontal attachment apparatus. Additional support for and retention of teeth with substantial vertical bone loss can be achieved. Pocket reduction and growth of alveolar bone are commonly observed. True histologic new attachment is less fre- quent and less predictable.

Alloplastic graft materials may have their greatest usefulness as autograft extenders, being added to available autogenous bone to provide a sufficient total volume of graft material. They may also be used as carriers for growth factors, antibiotics or other substances.

Synthetic bone grafting materials offer promise in periodontal therapy, but they are far from a panacea. They are not better clinically than autogenous or allo- geneic graft materials. All graft materials are only one aspect of the treatment of infrabony periodontal de- fects. More important than the type of graft material is proper case selection and appropriate surgical management of the defect and the root surface. There is no synthetic substitute for properly per- formed periodontal surgery.

References

1. Becker W, Becker B, Berg L, Prichard J, Caffesse R, Rosen- berg E. New attachment after treatment with root isolation procedures: report for treated Class I11 and Class I1 fur- cations and vertical osseous defects. Int J Periodont Re- storative Dent 1988: 8 (3): 2-16.

2. Boetto J, Freeman E. Histologic evaluation of durapatite in experimental periodontal defects. J Can Dent Assoc 1984: 50: 239-244.

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Bowers GM, Chadroff B, Carnevale R et al. Histologic evalu- ation of new attachment apparatus formation in humans. Part 111. J Periodontol 1989: 60: 683-693. Bowers GM, Vargo JW, Levy B, Emerson JR, Berquist JJ. Histologic observations following the placement of tricalci- um phosphate implants in human intrabony defects. 1 Periodontol 1986: 57: 286-287. Dragoo MR, Sullivan HC. A clinical and histological evalu- ation of autogenous iliac bone grafts in humans. I. Wound healing 2 to 8 months. J Periodontol 1973: 44: 599-613. Evans GH, Yukna RA, Sepe WW, Mabry TW, Mayer ET. Effect of various graft materials with tetracycline in local- ized juvenile periodontitis. J Periodontol 1989: 60: 491- 497. Frank RM, Gineste M, Benque EP, Hemmerle J, Duffort JF, Heughebaert M. Etude ultrastructurale de I’induction osseuse aprbs implantation de bioapatites chez I’homme. J Biol Buccale 1987: 15: 125-135.

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8. Froum SJ, Kushner L, Scopp IW, Stahl SS. Human clinical and histologic responses to durapatite implants in intraos- seous lesions. Case reports. J Periodontol 1982: 53: 719-725.

9. Froum SJ, Thaler R, Scopp IW, Stahl SS. Osseous autografts. I. Clinical responses to bone blend or hip marrow grafts. J Periodontol 1975: 46: 515-521.

10. Gottlow I, Nyman S, Lindhe J, Karring T, WennstrBm J. New attachment formation in the human periodontium by guided tissue regeneration. Case reports. J Clin Periodontol 1986 13: 604-616.

11. Jarcho M, Kay JF, Gumaer KI, Doremus RH, Drobeck HP. Tissue, cellular and subcellular events at a bone-ceramic hydroxylapatite interface. J Bioeng 1977: 1: 7S92.

12. Kenney EB, Lekovic V, Han T, Carranza FA Jr, Dimitrijevic B. The use of a porous hydroxylapatite implant in peri- odontal defects. J Periodontol 1985: 5 6 82-88.

13. Meffert RM, Thomas JR, Caudill RF. Hydroxyapatite im- plantation: clinical and histologic analysis of a treated lesion and speculations regarding healing phenomena. Int J Periodont Restorative Dent 1986: 6 (6): 61-66.

14. Meffert RM, Thomas JR, Hamilton KM, Brownstein CN. Hydroxyapatite as an alloplastic graft in the treatment of human periodontal osseous defects. J Periodontoll985: 56:

15. Mellonig IT. Decalcified freeze-dried bone dograft as an implant material in human periodontal defects. Int J Peri- odont Restorative Dent 1984: 4 (6): 41-55.

16. Rabalais ML, Yukna RA, Mayer ET. Evaluation of durapatite

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ceramic as an alloplastic implant in periodontal osseous defects. I. Initial six month results. J Periodontol 1981: 52: 680-689.

17. Sapkos SW. The use of Periograf in Periodontal defects - histologic findings. J Periodontol 1986: 57: 7-13.

18. Schallhorn RG. Present status of osseous grafting pro- cedures. J Periodontol 1977: 48: 570-576.

19. Snyder AJ, Levin MP, Cutright DE. Alloplastic implants of tricalcium phosphate ceramic in human periodontal oss- eous defects. J Periodontol 1984: 55: 273-277.

20. Strub JR, Gaberthuel TW, Firestone AR. Comparison of tricalcium phosphate and frozen allogenic bone implants in man. J Periodontol 1979: 50: 624-629.

21. Yukna RA, Harrison BG, Caudill RF, Evans GH, Mayer ET, Miller S. Evaluation of durapatite ceramic as an alloplastic implant in periodontal osseous defects. 11. Twelve-month reentry results. J Periodontol 1985: 56: 540-547.

22. Yukna RA, Cassingham RJ, Caudill RF et al. Six month evaluation of Calcitite (hydroxyapatite ceramic) in peri- odontal osseous defects. Int J Periodont Restorative Dent 1986: 6(3): 35-45.

23. Yukna RA. HTR polymer grafts in human periodontal oss- eous defects. I. 6 month clinical results. J Periodontol 1990: 61: 633-642.

24. Yukna RA. Human gingival tissue response to HTR poly- mer. J Biomed Mater Res 1992: 26: 517-527.

25. Zaner DJ, Yukna RA. Particle size of periodontal bone graft- ing materials. J Periodontol 1984: 55: 406-409.

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