Reprinted from Journal of Orallmplantology, Volume XV; Number 3; 1989. Pages 186 thru 192.

Jon R. Wagner, DDS

A Clinical and Histological Case Studyusing Resorbable Hydroxylapatite forthe Repair of Osseous Defects prior toEndosseous Implant Surgery

Abstract

A clinical case-a follow-up clinical and histological study-is presented in this paper, which describes theuse of resorbable hydroxylapatite OSTEoGEN@ (HA Resorb)@, Impladent Ltd., Holliswood, New York11423 for the repair of a large mandibular lesion, followed by the placement of an endosseous dentalimplant six weeks after the graft placement. A comparison of the histological results of four-month and

14-month bone biopsies of resorbable hydroxylaptite grafts is included in this report.

Introduction

The resorption of the alveolar process followingtooth loss has always been a very serious problemfor the restorative dentist and an enigma for theoral implantologist. Today, through the use of se-lected autogenous grafts, allografts, or resorbablealloplastic bone materials, specific defects of theresidual bone or extraction sites can be materiallyimproved in both shape and quality (Finn et ai.,1980; Judy, 1986a). These treated sites can nowbecome eligible for endosseous implants. Even withthe loss of cortical plates of bone, the socket ordefect can be rebuilt with resorbable grafting ma-terials. The osteoconductive materials effectivelyused are autogenous transplants, demineralizedfreeze-dried bone, or resorbable hydroxylapatite(Judy, 1986a,b).

For the past 3lJ2 years, this author has used re-sorbable hydroxylapatite (OsteoGen@) exclusivelyfor repairing most extraction sites, osseous de-fects, and sinus defects (augmentations), and inconjunction with all endosseous implant modali-ties inserted surgically. Resorbable and non-re-sorbable small-particle hydroxylapatite has beenmixed for use in repairing periodontal defectsaround natural teeth as well (Hubbard, 1974;

LeGeros, 1988; Jarcho et ai., 1976; Linkow, 1984,1986).

Materials

OsteoGen@ is a pure, uniquely resorbablehydroxylapatite (HA) implant material used for al-loplastic augmentation and the repair of bone de-fects. The material is chemically andcrystallographically equivalent to the mineral por-tion of human bone, specifically, CalO(P04) 60H2(Hubbard, 1974; LeGeros, 1988; Jarcho et ai.,1976; Linkow, 1986; Cranin et ai., 1987).

Density, crystal size, and porosity determine theresorbability of hydroxylapatite (HA) alloplasticimplant materials. Densely sintered, purehydroxylapatite ceramic has low microporosity,high density, and is prepared in relatively largeparticle size (18-40 mesh in most commerciallyavailable alloplastic preparations), by subjecting itto very slow resorption rates (LeGeros, 1988; Jar-cho et ai., 1976). Conversely, resorbable hydrox-ylapatite (HA) is a highly micro-porous, non-sintered (non-ceramic) material composed of smallparticles measuring 300-400 microns (35-60 mesh),with a controlled, predictable rate of resorption.Sintered (non-resorbable) hydroxylapatite mate-

rials are often subject to fibrous encapsulationrather than becoming a viable part of the host bone(Linkow, 1984, 1986). On the other hand, as non-sintered (resorbable) hydroxylapatite resorbs, it actsas a mineral reservoir and induces new bone for-mation via osteoconductive mechanisms. This"mineral reservoir" concept has been demon-strated by numerous histological studies whichstrongly suggest a direct correlation between in-creasing bone density and maturation with an on-going reduction in the mass of refractile crystal-line particles of HA as a function of time.

The hemostatic microfibrillar collagen used withthe resorbable hydroxylapatite is Avitene@(MedChem Products, Inc.). A one-to-four volumeratio of the microfibrillar collagen hemostat is mixedwith the resorbable hydroxylapatite and freshlydrawn venous blood. The mixture requires only asmall amount of the microfibrillar collagen matrixfor hemostasis to be produced. These materialsare mixed in a sterile porcelain Petri dish to a thickputty-like consistency prior to placement. Al-though hydroxylapatite products are non-inflam-matory and biocompatible, collagen products cancause allergic inflammatory reactions, and a patchtest should be run prior to surgery, especially onpatients who have numerous allergies (Judy, 1986a;Cranin et al., 1987).

Case History

A twenty-nine-year-old male presented with anacute lesion and cellulitis of the lower right sideof his face and chin. A panoramic radiograph (Fig.1) and an oral examination revealed a large peri-apical abscess about 1 cm in diameter in the re-gion of the right mandibular lateral incisor andcuspid. Only six mandibular teeth remained, all ina very poor state, with gross dental caries and gin-gival inflammation. With the exception of his den-tal condition, nothing else was remarkable in themedical history.

An incision and drainage were performed, andantibiotic therapy was instituted. Lincocin@ 600mg 1Mwas given, followed by a ten-day regimen oforal Cleocin@, 250 mg t.Ld. Seven days later, withthe acute infection dissipated, the patient wasprepared, draped, and anesthetized in the usualmanner, and the right lateral incisor and residualroot of the cuspid were removed. The n1ucoperios-teum was reflected, facially and lingually, and a largebony defect was revealed, with most of the facialcortical bone eroded at the extraction sites. A fen-estration of the lingual cortical plate at the lateralincisor socket, approximately 6 mm in diameter,created a through-and-through bony defect at thelevel of the root apex. The area was curetted, de-corticated (Fig. 2), and filled with a mixture of re-

Figure 1. Pre-operative radiograph.

Figure 2. Mandibular right lateral and cuspid bone defect.

sorbable hydroxylapatite, a microfibrillar collagenmatrix, and fresh venous blood. These materialswere mixed with 125 mg of tetracycline powder toa thick putty-like consistency in a sterile porcelainPetri dish. The graft was packed into the socketsand bony defects and placed over the labial andcrestal surfaces of the residual ridge, so that theridge would be recontoured to its normal architec-ture (Fig. 3). The borders of the facial and lingualmucoperiosteal tissue flaps were trimmed of gran-ulation and hypertrophic tissue to allow for coap-tation and complete closure. Primary healing wasuneventful.

Six weeks later, the remaining maxillary andmandibular teeth were extracted for the insertionof immediate dentures. Since the patient's job ne-cessitated his leaving the area for several monthsafter the extractions and dentures placement, it

Figure 3. Resorbable hydroxylapatite graft immediatelyafter placement.

Figure 4. Titanium blade implants partially seated only sixweeks after placement of the resorb able hydroxylapatitegraft in the right cuspid and lateral incisor area.

was decided to insert two submersible titaniumblade implants (Ultimatics, Inc., Springdale, AR)in the cuspid regions bilaterally and to allow theseimplants to heal without their prosthetic abut-ment posts during this interval. The grafted rightcanine and incisor areas were then surgically ex-posed and revealed a firm ridge that had main-tained its architecture and dimensions withregenerating bone in an osteoid state. It was ex-pected that the six-week-old resorbable hydroxyl-apatite graft would be fragile and easily displacedduring the osteotomy or during the insertion ofthe right blade implant; however, the entire graftedlabial plate remained intact. The graft was firmbut still pliable and elastic, and tenaciously at-

Figure 5. Fully seated implants in osteotomy withoutdisplacement of six-week-old resorbable hydroxylapatiteOsteoGen@graft (arrow).

Figure 6. Resorbable hydroxylapatite coagulum fillingosteotomies and fresh extraction sites. Implants' abutmentposts removed and healing collars in place.

tached to the bone substrate. After both osteoto-mies were completed, the two submersible bladeimplants were seated (Figs. 4, 5). The same re-sorbable hydroxylapatite coagulum was used tocover the shoulders of the implants, decorticatedfresh extraction sites, and around the base of eachhealing cap (Figs. 6,7). Complete closure of softtissue flaps allowed healing to occur in a non-func-tional and closed environment beneath the mu-coperiosteal tissues.

Four months post-operatively, the patient wasprepared, draped, and anesthetized. The mandib-ular ridge was surgically exposed from the rightretro-molar pad to the left retro-molar pad, facially

Figure 7. Panorex of submerged titanium implants andgrafts.

Figure 8. Site re-opened after four months, showingossified grafts with bone up to and over the base of theimplant healing collars.

and crestally. The two submerged implants in thecanine region were completely covered to and overthe bases of the healing caps, with newly regen-erated bone (Fig. 8). The healing caps were re-moved, and the trans epithelial prosthetic abutmentposts were affixed to the implants. Two one-piecetitanium double-abutment blade implants weresurgically inserted into the posterior regions bi-laterally, and the implants' shoulders and facialcortical plates were overlaid with the same mixtureof resorbable hydroxylapatite, microfibrillar colla-gen, and fresh venous blood as was described inthe first surgery. A bone core specimen was thenharvested and fixed in 95% ethanol for analysis bymeans of a 5.5-mm trephine instrument and co-pious water irrigation at the previously grafted rightcuspid apex area. The biopsy osteotomy was grafted

Figure 9. Post-op Panorex of seated implants withabutment heads and resorbable hydroxylapatite grafts.

Figure 10. Three-week post-op of healing surgery.

with the resorbable hydroxylapatite coagulum (Fig.9). Complete closure was performed by use of 3/0chromic gut continuous and interrupted sutures.Healing was rapid and uneventful (Fig.IO). A fullarch porcelain veneer bridge was constructed andsubsequently cemented with hard cement (Fig. 11).

ResultsClinical

After a year and a half, radiographic and clinicalevaluation of the patient revealed excellent healthof peri-implant tissue, with probing depths mea-suring between 0.5 and 0.75 mm. No signs of sau-cerization of crestal bone around the necks of thesix abutment posts were discernible.

Figure 11. Finished 14-unit porcelain veneer prosthesis.Note the length of anterior pontics. By retaining thearchitecture of the ridge through grafting procedures, itwas possible for normal-length pontics to be maintained.

Figure 12. Woven cancellous bone containing somerefractile crystalline particles of resorbable hydroxylapatitebordered by substrate of mature natural bone (50 x).

HistologicalA specimen with the HA graft (OsteoGen@) on

the facial aspect of the right canine-lateral incisorarea was sectioned without decalcification andstained with basic fuchsin.

(Specimens were prepared by- the George L.Schultz Laboratories Jor Orthopaedic Research,University oj Medicine and Dentistry oj NewJersey.)

Figure 13. Resorbable hydroxylapatite crystal (B) withwoven bone (C) showing a lack of inflammatory cells and inintimate contact with mature substrate bone (100 x).

Figure 14. J...amellated bone showing organization of newlyformed bone in typical lamellar pattern (D) with an area ofHaversian system formation (E) (100 x).

The slides demonstrate the formation of wovencancellous bone (Fig. 12), showing a lack of in-flammatory cells and in intimate contact with ma-ture substrate bone (Fig. 13). The interface ofregenerating bone and host bone was deficient inthe fibrous elements common with non-resorbablehydroxylapatite. Refractile crystals of the hydrox-ylapatite graft material were observed throughoutthe specimen. Sections taken near the surface ofthe specimen where the cortical plate was replacedshow a typical lamellar pattern and Haversian sys-tem formation (Fig. 14). At higher magnification(200 X), the resorbable hydroxylapatite (OsteoGen@)

Figure 15. Osteoblasts (A) at interface with resorbinghydroxylapatite crystalline particle (B) (200 x).

Figure 16. Resorbable hydroxylapatite particle showingerosion of surface. These particles appear to be largelyintact, as opposed to those seen in Figs. 4-16. This highlysuggests a time-dependent resorption process, since thepreceding graft had been implanted for 14 months, whilein this case the histological study was done after only fourmonths (200 x).

particles show surface erosion illustrating the re-sorption process (Figs. 15, 16).

Discussion

In over 450 applications, this author has exclu-sively used resorbable hydroxylapatite (OsteoGen@)for the repair of severe osseous defects, cysts, cra-ters, apicoectomies, sinus elevation augmenta-tions, and in conjunction with all of his otherroutine endosseous implant surgical cases. Re-sorbable hydroxylapatite can be used in place of

Figure 17. A bone core specimen taken by the author ofanother case after 14 months' implantation in the crypt ofan impacted 3rd molar that was grafted with resorbablehydroxylapatite. Note smaller particle size of refractile HAcrystals and the change of color of the newly formed bonefrom red fuchsin stain to yellow, indicating increasedmineralization. Brown areas indicate high-density areasresistant to the fuchsin stain absorption (100 x).

autogenous or freeze-dried bone grafts with verypredictable results.

The grafting coagulum has been utilized suc-cessfully with submersible and non-submersibletypes of implants. In most cases, the grafts wereplaced in medullary applications to promote theregeneration of cancellous bone. In the alveolarridge repair reported in this paper, a fairly largearea of missing cortical bone was replaced by theregeneration of lamellar bone, with evidence of aHaversian system typical of cortical bone.

Conclusion

OsteoGen@ is a highly micro-porous, non-sin-tered (non-ceramic), bioactive bone grafting ma-terial with a predictable, controlled resorption rate.As the material resorbs, it acts as a mineral res-ervoir and predictably induces new bone forma-tion via osteoconductive mechanisms. The materialappears to be very biocompatible in both hard andsoft tissues. When placed in direct contact withbone, there is little if any intervening soft tissue.OsteoGen@ (H.A. Resorb)@ provides a key raw ma-terial which the body naturally uses to create bone.Further, the crystalline structure of the resorbablehydroxlyapatite (RHA) enhances its chemical com-position by serving as a scaffold upon which thebody can build new bone as it slowly resorbs thematerial. Comparison of the histology of the bonecore specimens taken by this author supports the"mineral reservoir" hypothesis (Fig. 17).

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