Comparison of three methods of stabilization of particulate hydroxylapatite for augmentation of the mandibular ridge

J Oral Maxillofac 46:766-766.

Surg

1966

Comparison of Three Methods of Stabilization of Particulate Hydroxylapa tite for Augmentation of the Mandibular Ridge MOHAMED

EL DEEB, DDS, DOS, MS

This study compares stabilization of hydroxylapatite (HA) augmented phic mandibular ridges using no stabilization, an acrylic stent, and rubber urethral catheter (RRUC). Displacement of the HA particulates seen in 60% of the cases where the stent was used, 30% where no lization was used, and in no cases when the RRUC was used.

rial within the augmented area of the ridge during the immediate postoperative period. The use of a stent in mandibular augmentations, however, has been controversial. Kent et al.’ stated that “generally, no stent or modified denture was used in the augmented mandibular cases.” In a later publication, Kent et al. stated that “few stents are used for mandibular cases to maintain the convex shape of the implant.“’ On the other hand, many clinicians prefer the use of a stent of the patient’s hollowedout denture for 2 to 3 weeks to stabilize the mandibular alveolar ridge augmentation.3-7.‘0.” Other surgical techniques besides complete stents have also been used to contain the particulate HA. Propper” recommended placing buccolingual sutures in a horizontal mattress stitch to limit migration of the granules. Bedford and associates’3 advocated the use of segmented stents. Pham14 has advocated use of the open stent technique to stabilize the augmenting HA particulate. Kent and Jarcho” reported confinement of HA particles with intraoral nasogastric tubes that were sutured extraorally to a red rubber catheter with horizontal mattress sutures. Lambert had developed a twopiece surgical stent to facilitate augmentations of mandibular alveolar ridge with HA.16 The purpose of this article is to present a method for stabilizing particulate HA placed for augmenting the mandibular ridge involving the use of a red rubber urethral catheter (RRUC), and to compare the results achieved with this technique with those achieved with the stent technique and with a group of patients where no means of stabilization was used.

Augmentation of an atrophic mandible with particulate hydroxlyapatite (HA) has been shown by many clinicians to significantly increase height of the alveolar ridge. I-7 In spite of the success associated with the use of HA, however, complications still exist. Rothstein and associates* reported 203 patients who had alveolar ridges augmented at five major institutions. Fourteen per cent of these patients had migration of HA particles. El Deeb et al., 9 in an evaluation of 42 alveolar ridges augmented with HA, reported displacement of HA in 40% of the cases. The majority of the displaced HA material was not removed; however, in 19% of the cases a second surgical intervention was needed to recontour or remove some of the displaced material.’ Most clinicians agree that in maxillary cases a stent is needed to contain the particulate HA mate-

Associate Professor, Department of Oral and Maxillofacial Surgery, School of Dentistry, University of Minnesota, Minneapolis, Minnesota. Presented in part at the 67th Annual Meeting of the American Association of Oral and Maxillofacial Surgeons. Washington. DC, October 3-7, 1985; and at the 9th International Congress for Oral and Maxillofacial Surgeons, Vancouver, BC, Canada, May, 1986. This paper is supported by a grant from Dr. and Mrs. Ray Peterson. Address correspondence and requests to Dr. El Deeb: Associate Professor. Department of Oral and Maxillofacial Surgery, 7-174 Moos Tower, School of Dentistry University of Minnesota, 515 Delaware St. SE, Minneapolis, MN 55455. 0 1988 American geons

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Materials and Methods Fifty edentulous patients received augmentation of the mandibular alveolar ridge using particulate hydroxylapatite (HA). They were randomly assigned to three treatment groups. No device was used to stabilize the material in ten patients (group 1); in 20 cases, the stent technique was used (group 2); in another 20 cases, RRUC was used as a stabilizing device (group 3). Postoperative observation was carried out by one oral and maxillofacial surgeon and one prosthodontist at intervals of 1 week and 1, 3, 6. 12, 18, and 24 months. The methods of evaluation included clinical and radiographic examination using panoramic and occlusal radiographs to verify the immediate postoperative complications and displacement of the HA. Soft tissue incision lines and the augmentation sites were examined for inflammation, ulceration, sloughing, sensory loss, infection, incision line healing, and material displacement. The surgical technique used for cases having no stabilization and those in which stents were placed was that described by Kent et al.“* All the stents covered the full mandibular alveolar ridge and were maintained with circumandibular sutures for 2 to 3 weeks. When the RRUC was used in patients who had adequate bone anteriorly and severe resorption posteriorly, two vertical incisions were made anterior to the mental nerve in the area of the canine/first premolar. A subperiosteal dissection was then performed using a sharp periosteal elevator to create the subperiosteal tunnel (Fig. 1). The mental nerve was identified and freed from the overlying tissues by careful dissection to avoid traumatization of the

FIGURE I. Schematic drawing showing the incision and the creation of the subperiosteal tunnel with a periosteal elevator.

nerve and to obtain adequate relaxation of its overlying soft tissues. The periosteal elevator was then introduced buccally below the mental foramen and parallel to the inferior mandibular border, and the overlying mucoperiosteum and buccinator muscle were reflected from the superior surface of the posterior area of the mandible. This dissection was restricted to the denture-bearing area. The mylohyoid muscle was reflected lingually (Fig. 2). After obtaining adequate relaxation of the overlying tissue, a traction suture was placed along the incision line to keep the subperiosteal pocket open while no. 0 Tevdek circumandibular sutures were passed with a mandibular passing awl in the canine and molar areas (Fig. 3). Placement of the suture in the awl created a lingual loop and two free ends located buccally. Both the lingual loop and the two ends were then grasped and moved in a sawing motion through the soft tissue so that the suture lit around the inferior border of the mandible (Fig. 3). After a similar set of sutures were placed on the contralateral side, a sterilized no. 16gauge French RRUC (CR. Brad, Inc., Brad Urological Division, Murray Hill, NJ) was then trimmed into two segments: a longer tube to be placed buccally extending from the area of the second molar to the area of the canine, and a shorter tube to be placed lingually extending from the area of the third molar to the site of the tirst premolar. Before the tubes were placed into the lingual loops and buccal suture, slits were made in each tube to receive the sutures and prevent displacement. The lingual tube was placed into the lingual loops first. Then the buccal suture was

FIGURE 2. Schematic drawing showing cross-section of postsurgical dissection of the buccinator and mylohyoid muscles. This allows for more relaxation of the mucoperiosteal tissue.

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FIGURE 3. Schematic drawings showing the technique for passing the circummandibular sutures while the created subperiosteal tunnel is held open by traction-sutures. Sawing motion is used to adapt the circummandibular sutures around the inferior surface of the mandible.

pulled to secure the tube against the lingual mandibular cortex. The buccal tube was placed between the two ends of each buccal suture and secured in position with double knots. It was found to be important to suture the lingual and buccal tubes while the subperiosteal pocket was open. The latter was easily accomplished by the traction-suture technique (Fig. 4A) or by introducing the syringe of hydroxylapatite into the created subperiosteal pocket prior to tying the circumandibular sutures together (Fig. 4B). The HA was then delivered over the area where augmentation was desired (Fig. 4C). Additional material was added until the desired augmentation was obtained. A similar procedure was performed on the contralateral side and the incisions were closed with 3.0 Dexon’s’ sutures. Precautions were taken to avoid overextension of the tubes buccally and lingually because this might lead to ulceration of the soft tissue. If the ends of the tubes were sharp, a soft white wax was placed over the ends. When stabilization with an RRUC was used for a total mandibular augmentation a surgical procedure similar to that previously described was used for augmentation of the posterior mandible. However, the two verticle incisions in the area of the canine and first premolar were extended buccally into the FIGURE 4. Schematic drawing of mandibular cross-section showing lingual tube secured to the buccal tube with circumandibular sutures. Notice that the suture is tied while the subperiosteal pocket is kept open. B, clinical photo showing the syringe with the hydroxylapatite in place while the lingual tube is sutured to the buccal tube. C, schematic drawing showing cross-section for the stabilized augmented hydroxylapatite material with the lingual and buccal tubes.

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vestibule of the lip about 0.5 cm from the vermilion border. A dissecting scissors was then introduced into one of the incisions and a submucosal dissection was carried out from that incision to the contralateral side to relax the overlying mucosa (Fig. 5 A). The scissors were then opened and a no. 15 blade was used to incise the mucosa over the superior edge of the scissor and connect the vertical incisions (Fig. 5B). The tissue was then sharply dissected until the superior border of the mandible was reached (Fig. 5C). The lingually based flap was reflected only to the superior surface of the lingual cortex, to uncover the portion of the alveolar ridge in need of augmentation. Careful dissection was done to prevent trauma to the lingual tissues; this area contains the main source of blood supply to the flap. The periosteum and mentalis muscle were then incised over the superior aspect of the anterior mandible and the tissues were reflected buccally (Fig. 5

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D) and sutured in a manner similar to the lip switch technique. The lingually based flap was then sutured inferior to the periosteum along the facial aspect of the inferior mandibular surface and a traction-suture was placed along each edge of the flap (Fig. 6). Four circumandibular sutures were placed posteriorly, similarly to those described in the posterior augmentation technique. Additionally, two sutures were placed anteriolabially to create two loops and these loops were brought out extraorally with a passing needle or mandibular awl (Fig. 7A). The RRUC was trimmed into three pieces: two small tubes are placed through the posterior lingual loops as previously described and a larger buccal tube was passed through the two labial loops anteriorly and then into the four free ends of the posterior circumandibular suture (Fig. 7A). The buccal tube was held in place by suturing it to the two small lingual tubes posteriorly and by suturing it extraorally to a Silastic@ button placed over a piece of

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FIGURE 5. A, schematic drawing showing submucosal dissection using a surgical scissors. E, schematic drawing showing initiation of the lingually based flap by incising the mucosa over the superior surface of the opened scissors. C. schematic drawing showing the lingually based flap reflected lingually and incision of the mentalis muscle and periosteum. D, schematic drawing showing reflection of the mentalis muscle and the periosteum buccally to expose the anterior mandibular alveolar ridge.

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FIGURE 6. Schematic drawing showing suturing of the lingually based flap to the vestibular tissues.

Telfa@ to avoid ulceration of the skin anteriorly (Fig. 7A). The HA was then delivered into the areas to be augmented (Fig. 7B). A total lingual tube was not used because: 1) the blood supply of the lingually based flap depends upon the lingual tissues. so that using a total lingual tube might compromise the blood supply to this flap; 2) lingual tissue is not elevated from the bone and for that reason the HA will not be displaced lingually; and 3) the high position of the anterior mandibular floor and the presence of the salivary glands may cause discomfort for the patient and may lead to lingual ulceration. The incisions are closed with 3.0 Dexon@ suture (Fig. 7C). All the tubes were maintained in place for about 2 to 3 weeks. Following surgery, all patients were placed on penicillin VK, 500 mg every six hours for 2 weeks. Patients allergic to penicillin received erythromytin, 250 mg for seven days. All patients received ibuprophen, 800 mg every six hours for 2 weeks, for postoperative pain. A backup prescription for acetemenophen and 30 mg codeine was given, and patients were instructed to take one or two tablets if ibuprofen was ineffective in controlling their pain. The patients were placed on a clear liquid diet for 24 hours and then advanced to full liquid, pureed, and finally to a soft diet as tolerated up to the time of denture insertion. All patients had instructions to remove the upper denture at night. Results Fifty patients (42 women and eight men), varying in age from 26 to 77 years (mean age, 56 years) had augmentation of the mandibular alveolar ridge using particulate hydroxylapatite. Of the 20 patients for whom the technique using the RRUC was chosen, eight received total mandibular augmentation and 12 posterior mandibular augmentation. Twelve pa-

FIGURE 7. A, schematic drawing showing the buccal tube fixed to the lingual tubes posteriorly and anteriorly to an extraoral Silastica button. B, schematic drawing showing delivering the hydroxlyapatite material over the mandibular ridge while the two lingual tubes sutured to the buccal tubes posteriorly and of the buccal tube secured extraorally to the silastic button. C. schematic drawing showing closure of the two vertical incisions following augmentation of the mandible.

tients had Class II deficiencies, six has Class III, and two had Class IV, according to the classification of Kent et al. ’ The RRUC was maintained in place for an average of 17 days (range, 14 to 22 days). Vestibuloplasty was not needed by any of the patients for up to 2 years postoperatively.

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Of the 20 patients for whom regular stenting techniques were chosen, ten received total mandibular augmentation and ten posterior augmentation. Thirteen patients had Class II deficiencies, six had Class III, and one had a Class IV. The stents were maintained in place for an average of 14 days (range, 10 to 18 days). Three patients (15%) required skin-graft vestibuloplasty. Of the ten cases where no stabilization was used, six received total mandibular augmentation and four received posterior mandibular augmentation. Six patients had Class II deficiencies, three had Class 111, and one had a Class IV deficiency. Vestibuloplasty was performed in three cases (30%). The HA became consolidated in all cases within 3 to 4 weeks. All the patients had temporary dentures placed at 6 to 8 weeks postoperatively. Permanent dentures were placed at between 6 and 12 months postoperatively, the mean being 8 months. Postoperative complications are summarized in Table 1. Paresthesia of the mental nerve occurred in 35 cases (70%). Of these cases, 25 (71%) regained all sensation in the lower lip within 6 months and two (6%) regained all sensation within 1 year. The other eight had partial numbness (they regained up to 50% of sensation in the lower lip) over a mean period of 24 months postoperatively. No statistically significant differences were found among the three treatment groups when results concerning residual paresthesia of the mental nerve were compared (Table 1). Postoperative inflammation, seen for up to 9 weeks, was worst in patients for whom the stent technique had been used. Fourteen cases (70%) had some evidence of inflammation. By contrast, when the RRUC technique or no stabilization was used, 30% showed some signs of inflammation. This dif-

ference was statistically significant (p < 0.05, Table 1). Dehiscence of the incision and sloughing of part of the overlying mucosa were seen more often when the stent technique was used than when the RRUC technique or no stabilization was used (Table 1). Chi-square analysis, however, revealed no statistically significant differences among the three treatment groups. Postoperative ulceration was present more often in the group using the stent technique. Differences among the three treatment groups with respect to ulceration were statistically significant (p < 0.05). Displacement of the HA was seen in 12 cases (60%) when the stent technique had been used (Fig. 8A). Three cases (30%) that had no stent also had displacement of the material (Fig. 8B). None of the cases where the RRUC technique had been used had displacement of HA. Chi-square analysis revealed differences among the three groups to be statistically significant (p < 0.001). The amount of postoperative pain associated with the stent technique was much more than that with the RRUC technique. This lead the surgeon to remove the stent earlier (mean, 14 days) than the RRUC (mean, 17 days). The postoperative pain associated with the RRUC, however, was greater than that observed when no means of stabilization was used. Because of the radiopacity of the HA, it was difficult to assess any evidence of formation or resorption of bone at the HA/bone interface. Quantitative changes in the particulate HA were difficult to assess because of the various degrees of magnification associated with the nonstandardized panoramic radiograph technique. Clinical subjective evaluation of the conformation of ridge-shape was comparable

Table 1. Postoperative Complications of Augmentation of Mandibular Alveolar Ridge with Hydroxylapatite Method of Stabilization GROUP1 NOW

Complication Paresthesia, Lower Lip. 12 months + Inflammation l-9 weeks Dehiscence of Incision Line Abscess Around Suture Displacement of Implant Sloughing of Part of Overlying Mucosa Ulceration + p < 0.05 * p < 0.01

GROUP? stem\

GROUP3 RRUC

tn = 101

in = 201

(n = ?U)

3(30%) 3(30%)

2( IO%) 14(7O%‘c)

3(15%) 6(30%)

2(20%) l(lO%) 3(30%)

8(40%) 4(20%) 12(60%)

4(20%) 3(15%) O-

0 0

3(15%‘c) 8(40%)

O2(10%)

Chi-Square p-Value 2.01 7.73

0.366 0.021*

2.38 0.304 0.52 0.771 17.14 o.OO** 4.79 8.75

0.091 0.012*

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FIGURE 8. A. mandibular occlusal radiograph showing labial and buccal displacement of particulate hydroxylapatite that rolled under the flanges of the stent in a case where a full stent had been used for stabilization. B. mandibular occlusal radiograph showing lingual displacement of particulate hydroxylapatite in a case where no stent had been used.

between cases where RRUCs had been used and where stents had been used (Fig. 9). Detailed evaluation of dentures, retention/stability, and overall prosthodontic evaluation were beyond the purpose of this paper. Discussion Displacement of particulate hydroxylapatite beyond the desired denture-bearing area is considered to be a major disadvantage of augmentation of the mandibular alveolar ridge with this material. The problem is related to difficulty in confining the granules to the augmented ridge. Granules become displaced into the buccal vestibule or into the floor of the mouth, and may cause some problem in properly seating the denture, or they may cause an esthetic problem by unfavorably changing the mento-

labial angle if anteriolabial displacement occurs. Displacement may occur as a result of: 1) aggressive development of the subperiosteal tunnel; 2) pressure on the granules of HA before the material has consolidated; and/or 3) inadvertent misplacement of the material by the surgeon. One of the methods for stabilizing HA most commonly reported in the literature is use of the stent technique. This technique is useful in cases of augmentation of the maxillary alveolar ridge, where the palatal shelf acts as a stopping point, allaying the effect of any vertical force that might act against the augmentation while the particulate HA stabilizes and hardens. Larsen et al.” stated that the advantages of a stent as a means of stabilizing augmentations with particulate HA are: 1) it minimizes the migration of the HA before fibrosis occurs; 2) it aids in placement of HA to achieve the desired form and

EL DEEB

FIGURE 9. Panoramic radiographs showing the mandibular ridge preoperatively. immediately postoperatively, 1 year postoperatively, and 2 years postoperatively (top to bottom) in a case where the RRUC was used. Note good adaptation of the hydroxylapatite.

width of the arch: 3) it maintains the health of overlying soft tissues during healing; and 4) it reduces the amount of HA required. Unfortunately, augmentation of the mandibular ridge with particulate HA is not so exact because it is a procedure that depends on the clinician’s judgment. If the stents are made too loose or too tight, problems increase. Our previous experience indicates that the disadvantages of improper fit or design of stents may lead to increase in the following postoperative complications: mucosal ulceration, dehiscence of soft tissues, extrusion of material, displacement of material, and severe postoperative pain and difficulty in swallowing.’ In this study, the incidence of postoperative inflammation, ulceration, dehiscence of the incision, and sloughing of the overlying mucosa was greater in cases in which stent techniques were used than in those where the RRUC was used. The increased incidence of postoperative complications and pain in stented cases is usually due to an overextended

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stent, a stent that is too tight, or overbuilding of the augmenting material. The lower incidence of complications with the RRUC might be explained by the fact that the RRUC can adapt more readily to individual variations than do rigid stents. The results of this study revealed that in cases where no stabilization was used, and especially in those where the stenting technique was used, the incidence of displacement of granules of HA was much higher than it was in those where the RRUC had been used. DesjardinsZ4 also found, as we did, that attempts to control augmenting HA material with a stent are not effective because the stent will force the particles further laterally or medially if the periosteum has been raised from the alveolar bone. In the RRUC technique, the tubes are stabilized against the lingua1 and buccal mandibular bone and secured to the superior border prior to delivering the HA material to prevent displacement. Confinement of the HA particles was also reported by Kent and Jarcho,‘j who used Silastic@ or nasogastric tubes intraorally that were sutured extraorally to a red rubber catheter using horizontal mattress sutures. This technique differs from the one described here in that it does not use any lingual tubes, which could increase the incidence of lingual displacement . Adding any resorbable alloplastic material to particulate HA for the purpose of decreasing the incidence of HA displacement may result in more settling than when the HA granules are used alone. When plaster of Paris was added to particulate HA, the plaster resorbed, leaving thicker collagen fibers between the particles of HA than when HA was used alone.‘3 Similar histologic reactions may be seen when any resorbable material is added to the granules of HA. The higher the ratio of soft tissue to HA, the greater the chances that compacting may occur under the forces of mastication. The more the hydroxylapatite is compacted, the more it leads to adjustments in dentures, relining, and remakes.lx Mehlish et al. also found that HA combined with collagen lost 22% of augmented height within 6 months.‘3 This loss was due to the high ratio of soft tissue to HA resulting from resorption of the collagen. A similar finding was also noted in an animal study in which a mix of HA and collagen had been used; compaction occurred as a result of replacement of the collagenous component by dense fibrous connective tissue.” If the HA displacement problem can be solved by the RRUC surgical technique, adding any resorbable material to the HA for the purpose of alveolar ridge augmentation should not be needed. The technique described in this article solves the problem of displacement of particulate HA in aug-

766 mentation of the alveolar ridge. The advantages of the technique using the RRUC are that it: 1) is readily available in sterile packages; 2) does not require any laboratory procedures; 3) is less expensive; 4) fits individual ridge-form; 5) causes less postoperative pain by decreasing the incidence of postoperative ulceration; 6) contains the augmenting granules within the area of the alveolar ridge until soft tissue has infiltrated between them, thus reducing the incidence of displacement of the material; 7) reduces the incidence of postoperative ulceration, dehiscence, and extrusion of material; and 8) maintains vestibular depth and helps reposition the mylohyoid muscle, therefore decreasing the need for a secondary vestibuloplasty.

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Acknowledgment The author thanks Dr. Theodore Morstad for the prosthetic management of the patients used in this study.

References 1. Kent JN, Quinn JH, Zide MF, et al: Correction of alveolar ridge deficiencies with nonresorbable hydroxylapatite. J Am Dent Assoc 105:993. 1982 2. Kent JN, Quinn JH, Zide MF. et al: Alveolar ridge augmentation using nonresorbable hydroxylapatite with or without autogenous cancellous bone. J Oral Maxillofac Surg 41:692, 1983 3. Hones GH. Fielding AF, Boyczuk E, et al: Hydroxylapatite ridge augmentation. J Phil City Dent Sot 49:13. 1983 4. Shafer SC. Pamell AG: Hydroxylapatite augmentation of the mandible with simultaneous mucosal graft vestibuloplasty. J Oral Maxillofac Surg 42:749, 1984 5. Waite DE, El Deeb ME, Morstad AT: Alveolar ridge augmentation and the edentulous patient: Current clinical considerations. New Dimen Oral Surg 7:7, 1984 6. Rothstein SS, Paris DA, Sage B: Use of Durapatite for the rehabilitation of resorbed alveolar ridges. J Am Dent Assot 109:571, 1984 7. Alling CC: Hydroxylapatite augmentation of edentulous ridges. J Prosthet Dent 52:828, 1984 8. Rothstein SS, Paris DA, Zacek MP: Use of hydroxylapatite for the augmentation of deficient alveolar ridges. J Oral Maxillofac Surg 42:224, 1984 9. El Deeb ME, Gatto DC. Waite DE: Hydroxylapatite as a

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ridge implant-preliminary report. Abstract presented at the 65th annual meeting of the AAOMS, 1983, p 48 Parnell AC. Shafer S. Prentice L: Clinical experience in the surgical implantation of Durapatite with a vestibuloplasty for mandibular ridge augmentation. New Dimen Oral Surg 102:l. 1984 Larsen HD, Guerro LR. Finger IM: Hydroxylapatite: Prosthodontic clinical considerations. Compend Cont Educat 10:786, 1984 Propper RH: A technique for controlled placement of hydroxylapatite over atrophic mandibular ridges. J Oral Maxillofac Surg 43:469, 1985 Bedford WG, Carter JB, Cossett DL: A new segmented stem design for hydroxylapatite mandibular ridge augmentation. Abstract presented at the 67th annual meeting of the AAOMS. Washington, 1985, p 66 Pham H: Use of an open splint in ridge augmentation with hydroxylapatite. J Oral Maxillofac Surg 4:80, 1986 Kent JN. Jarcho M: Reconstruction of the alveolar ridge with hydroxylapatite, in Fonseca RM, Davis HW (eds): Reconstructive Preprosthetic Oral and Maxillofacial Surgery. 1st ed. Philadelphia, WB Saunders, 1986. pp 314325 Lambert PM: Two piece surgical splint to facilitate hydroxylapatite augmentations of the mandibular alveolar ridge. J Oral Maxillofac Surg 44:329. 1986 Piecuch JF, Topazian Rd. Skoly S, et al: Experimental ridge augmentation with porous hydroxylapatite implant. J Dent Res 62: 148, 1983 El Deeb ME. Tompach PC, Morstad AT: Porous hydroxylapatite granules and blocks of alveolar ridge augmentation materials: A preliminary report. Abstract presented at the AAOMS meeting, Anaheim, CA, 1987 Bochlogyros PN. Hensher R. Becker R, et al: A modified hydroxylapatite implant material. J Maxillofac Surg 13:213, 1985 Harvey WK. Pincock JL, Lemons JE: Evaluation of a subcutaneously implanted hydroxylapatite-Avitene mixture in rabbits. J Oral Maxillofac Surg 43:277. 1985 Gongloff RK, Montgomery CK: Experimental study of the use of collagen tubes for implantation of particulate hydroxylapatitk. J Oral Maxillofac Surg 43:845, 1985 Mehlish DR. et al: Evaluation of collarrenihvdroxvlauatite for augmenting deficient alveolar ridges: ‘A prehm’inary report. J Oral Maxillofac Surg 45:408, 1987 Frame JW. Rout PGJ. Brown RM: Ridge augmentation using solid and porous hydroxylapatite particles with and without autogenous bone and plaster. J Oral Maxillofac Surg 45:77l. 1987 Desjardins RP: Hydroxylapatite for alveolar ridge augmentation: Indications and uroblems. J Prosthet Dent 54:374. 1985 Hatcher JE. Lemons JE. Matukas VJ, et al: Laboratory animal studies of apatite and collagen biomaterials. J Dent Res 651347. 1986