Evaluation of collagen/hydroxylapatite for augmenting deficient alveolar ridges: a preliminary report

Internal oblique line implants in severe mandibular atrophies

Background

Maxillary atrophy may be related to mechanical, inflammatory or systemic factors, being a consequence of a reduction in the amount and quality of available bone. Several surgical techniques have been developed for the restoration of bone volume needed for placing dental implants; guided bone regeneration or three-dimensional reconstructions with autologous bone, inter alia, are techniques described in the literature which demonstrate this, all of which preceded by a proper prosthetic surgical assessment. Even when the majority of authors recommend the use of these techniques prior to placing implants, it has been shown that implants with a smaller diameter and length may be placed in severely atrophied jaws without the need for performing any surgery, offering excellent results.

Material and Methods

Twenty-four (24) implants were placed in six patients with severe mandibular atrophy. The implants were placed in the anterior sector and on an internal oblique line. Patients were rehabilitated with a total implant-supported prosthesis, with monitoring over a 10-year period.

Results

After a 12-month monitoring period, all the patients presented successful rehabilitation. Marginal bone loss in general (n=24 implants) was +0.11 mm ± 0.53. In the implants in zones 1 and 4 (posterior) it was +0.06 mm ± 0.48 and in implants in zones 2 and 3 (anterior), +0.14 mm ± 0.57.

Conclusions

Implants can be placed in the anterior zone and on an internal oblique line in patients with severe mandibular atrophy, using a diameter and length adapted to bone availability, for later prosthetic rehabilitation, offering satisfactory results since phonetic and masticatory function can be restored, as well as facial and buccal aesthetics, in a single surgical operation, with minimum morbidity. Key words:Severe atrophy, implants, bone grafts, ridge atrophy, internal oblique line.

Hydroxyapatite calvaria graft repair in experimental diabetes mellitus in rats

Among the systemic conditions that impact negatively on the planning and execution of surgical procedures, diabetes mellitus (DM) is the primary clinical condition responsible for complications. This study investigated bone formation in critical defects surgically filled with hydroxyapatite (HA) in diabetic rats. A descriptive, randomized sample and blinded analysis were conducted to test bone regeneration in critical bone defects surgically performed in rat calvaria. Twenty adult male Wistar rats were randomly divided into two groups: control, normoglycemic animals (CG); and test, streptozotocin-induced hyperglycemic animals (TG). A circular bone defect was filled with HA and maintained subperiosteally. The clinical parameters evaluated were body weight, water and food intake, fasting blood glucose, and bone alkaline phosphatase. Bone-grafted area samples were submitted for histomorphometric and stereological analysis. The TG showed a significantly higher rate of new bone formation compared with the CG, sacrificed 15 days after surgery (p < 0.0001). However, at the end of the study, there was no significant difference in the amount of bone formed between groups (p = 0.077). In parallel, with the increase in osteoblastic activity observed in the TG by the measurement of systemic bone alkaline phosphatase (p = 0.016), the analysis of polarized microscopy and stereology demonstrated a lower level collagen maturation and mineralization in the TG. Quantitatively, the TG showed significantly better results for bone gain in the first 15 days. Qualitative assessments, however, showed fewer collagen fibers and bone maturation in the TG compared with the CG both at 15 and 45 days. Therefore, the postoperative evaluation of bone grafts with HA in hyperglycemic situations should consider the systemic and local effects of this condition on the quality of bone repair, rather than identifying the filling or stability of the grafted area after the process. We conclude that clinically detectable bone repair in diabetic animal models submitted to hydroxyapatite grafts may be satisfactory in the early stages. However, hyperglycemia compromises the quality of the newly formed bone and the collagen cross-linking involved in this process.

Biocomposites and hybrid biomaterials based on calcium orthophosphates

The state-of-the-art of biocomposites and hybrid biomaterials based on calcium orthophosphates that are suitable for biomedical applications is presented in this review. Since these types of biomaterials offer many significant and exciting possibilities for hard tissue regeneration, this subject belongs to a rapidly expanding area of biomedical research. Through successful combinations of the desired properties of matrix materials with those of fillers (in such systems, calcium orthophosphates might play either role), innovative bone graft biomaterials can be designed. Various types of biocomposites and hybrid biomaterials based on calcium orthophosphates, either those already in use or being investigated for biomedical applications, are extensively discussed. Many different formulations, in terms of the material constituents, fabrication technologies, structural and bioactive properties as well as both in vitro and in vivo characteristics, have already been proposed. Among the others, the nanostructurally controlled biocomposites, those containing nanodimensional compounds, biomimetically fabricated formulations with collagen, chitin and/or gelatin as well as various functionally graded structures seem to be the most promising candidates for clinical applications. The specific advantages of using biocomposites and hybrid biomaterials based on calcium orthophosphates in the selected applications are highlighted. As the way from the laboratory to the hospital is a long one, and the prospective biomedical candidates have to meet many different necessities, this review also examines the critical issues and scientific challenges that require further research and development.

A trial to prepare biodegradable collagen-hydroxyapatite composites for bone repair

This paper is a trial to prepare collagen-hydroxyapatite composites in vitro by an alternate immersion method. Collagen sponges of different biodegradabilities were prepared through chemical cross-linking of Type I collagen with glutaraldehyde (GA) at concentrations of 0.2, 1.0, and 2.0 wt%. The sponges were immersed at 37 degrees C in Tris-HCl-buffered solution containing 200 mM CaCl2 (pH 7.4) for 2 h and then in an aqueous solution of 120 mM Na2HPO4 (pH 9.3) for a 2 h further (one immersion cycle). The alternate immersion cycle was repeated for different times to obtain collagen-hydroxyapatite composites. The characterization of the resulting composites was performed by Fourier transform infrared spectroscopy (FT-IR). X-ray diffraction (XRD), and scanning electron microscopy (SEM). The weight of composites increased with an increase in immersion cycles and the rate of increase became greater with higher GA cross-linking levels for collagen sponge preparation. The pH of the phosphate solution decreased with the immersion cycle, which suggests H+ generation accompanied hydroxyapatite formation. Irrespective of the GA concentration and immersion cycle, every composite showed IR absorption bands attributable to phosphate and hydroxyl groups at 950-1100 or 550-650 and 3000-3500 cm(-1) and broad peaks specific to hydroxyapatite on the XRD charts. SEM study revealed small white clusters of hydroxyapatite interspersed uniformly on/in the collagen framework without any preferential orientation. The composite prepared from 0.2 wt% GA cross-linked collagen sponge which showed favourable characteristics was applied to a rat skull defect to evaluate its osteoconductivity as well as biodegradability. The formation of new bone tissue was histologically observed at the defect 12 weeks after application in marked contrast to the collagen sponge alone. The composite degraded without any inflammation reaction. It is concluded that the collagen-hydroxyapatite composite prepared by the present method is a biodegradable biomaterial of osteoconductivity applicable to bone repair.

A new injectable calcium phosphate biomaterial for immediate bone filling of extraction sockets: a preliminary study in dogs

BACKGROUND

Many different bone substitutes, such as autografts, allografts or synthetic biomaterials have been proposed to restore alveolar bone loss and support efficient placement of dental implants. This experimental study evaluated the osteoconductive properties of an injectable bone substitute (IBS) composed of a polymeric carrier and a calcium phosphate mineral phase, used to fill mandibular and maxillary canine extraction sockets.

METHODS

The polymer was a cellulose derivative (methyl-hydroxy-propyl-cellulose, MHPC), and the mineral phase consisted of granules of biphasic calcium phosphate (BCP) ceramics 200 to 500 microm in diameter. Mandibular and maxillary premolars extracted from 3 dogs (a total of 60 extraction sites) were immediately treated with the IBS or left unfilled as control sites. Animals were sacrificed 3 months after implantation and all extraction sockets were prepared for histological evaluation.

RESULTS

Qualitative histological studies showed that the IBS was able to support the extensive apposition of well-mineralized newly formed lamellar bone over the entire socket surface and appeared to prevent alveolar ridge bone loss in treated extraction sites. Quantitative evaluation showed that the amount of newly formed bone was significantly higher in mandibular than maxillary extraction sockets for both treated and control sites.

CONCLUSIONS

An injectable bone substitute composed of a polymeric carrier and calcium phosphate was effective in enhancing the bone fill of extraction sockets. This approach may prove promising for periodontal lesions. The material expressed osteoconductive capacities, and the biological properties of the mineral phase were conserved.

Porous hydroxyapatite reinforced with collagen protein

Porous hydroxyapatite (HAP) with certain porosity and pore size was prepared, and incorporated with bovine collagen protein. The composition and structure of the HAP was confirmed by X-Ray Diffraction (XRD) and ICP. Scanning Electron Microscopy (SEM), mechanical tests and in vitro degradation were performed. Collagen protein with low antigenicity was obtained from bovine tendon by enzyme digestion, and was then forced to fill in the HAP matrix to form composites. Scanning Electron Microscopy (SEM), Mechanical tests and in vitro degradation were performed. The test results show that first, HAP thus made has specific pore size and directions; second, mechanical properties of the composites have been markedly improved; third, the in vitro degradation rate of the composite is almost the same as and mainly controlled by the degradation rate of collagen.

Initiation of alveolar ridge augmentation in the rat mandible by subperiosteal implantation of octacalcium phosphate

The study was designed to investigate the process of bone formation caused by implantation of octacalcium phosphate as well as stability of the bone formed at the alveolar ridge. Synthetic octacalcium phosphate was implanted into a subperiosteal pocket in the rat mandible. Bone formation at the alveolar ridge was examined radiographically and histologically between 1 and 48 week(s) after implantation. Radiopacity of the octacalcium phosphate implant became obvious in week 2. Osteogenesis was initiated from the bone surface near the implantation site and multinucleated giant cells appeared on the implanted octacalcium phosphate in week 1. More apposition of new bone was observed on the implanted octacalcium phosphate in week 2 or later. Some implants were directly enclosed by newly formed bone and no cellular component was seen between the implant and the bone matrix. Many octacalcium phosphate implants were enclosed by bone, whereas the augmented ridge was not seen radiographically in week 24 or later. If its persistence can be improved, octacalcium phosphate could be used to augment atrophic alveolar ridges.

Formation of apatite-collagen complexes

An apatite-collagen complex was prepared in calcium beta-glycerophosphate solutions at pH 9.0 and 37 degrees C with the purpose of developing new bone substitutes that more closely resemble bone than currently available materials. Reconstituted type I collagen as well as sheet collagen were crosslinked in the presence of alkaline phosphatase and egg-yolk phosvitin. The crosslinked collagens were immersed in daily-renewed calcium beta-glycerophosphate solutions for 2 and 4 weeks to induce the deposition of apatite on the collagen fibers. After 2 weeks of reaction, for example, apatites deposited approximately two times the crosslinked collagen in weight. With reconstituted collagen, the complex showed some elasticity but no apatite was visually observed to detach under deformation with fingers and forceps. The complex, moreover, did not disintegrate when immersed in saline or animal blood. Nevertheless, the complex resorbed with no evidence of cytotoxicity when implanted in muscle tissues. These findings suggest that the apatite-collagen complex prepared would be useful as bone substitutes, especially for periodontal osseous lesion repair and alveolar ridge augmentation.

The combined use of hydroxylapatite segments and granules for alveolar ridge reconstruction

Long-term augmentation of the severely resorbed alveolar ridge with particulate hydroxylapatite (HA) has proved problematic. In this study, 70 patients were treated with a combination of HA granules and dense nonresorbable HA particles strung on a resorbable suture matrix. Fifty-five patients have been observed for 12 to 50 months. The combination technique has been successful in all but four cases.

Fate of bioresorbable poly(lactic acid) microbeads implanted in artificial bone defects for cortical bone augmentation in dog mandible

The fate was examined of poly(lactic acid) microbeads implanted in large artificial defects created in cortical bone of dog mandibles. Two poly(lactic acid) polymers--poly(L-lactic acid) (PLA 100) and poly(DL-lactic acid) (PLA 50)--were used to make microbeads by solvent evaporation with poly(vinyl alcohol) as surfactant. Histological observation of non-decalcified mandibular bone showed that no real bone regeneration existed in the experimental bone defects 18 months after PLA 100 microbeads implantation. The same observation was made 6 months after implantation of PLA 50 microbeads. PLA 100 and PLA 50 microbeads appeared unable to induce regeneration of cortical bone defects of dog mandible, in contrast to previous observations in man for PLA 50 large implants. The failure is tentatively assigned to the presence of poly(vinyl alcohol) at the surface of microbeads.

Tissue integration of the collagen-hydroxylapatite implant: histological examination in canine bone and surrounding tissues

Using the dog as an animal model, we have tested an implant material composed of purified fibrillar collagen (PFC) and particulate hydroxylapatite (HA) in the mandible and in surrounding tissues. Bone and tissue samples were taken at 2, 4 and 6 months for histological study. After 2 months, the PFC was replaced by fibro-connective host tissues. After 4 months, some small areas of ossification were observed around the HA particles. After 6 months, the fibro-connective tissue was replaced by neo-formed bone in the mandible. PFC was found to increase the interfaces between the HA particles and the host tissues, permitting HA integration into the bone. The PFC/HA implant was also molded when moistened by blood or saline solution and then became mis-sharpen by local pressures exerted. These findings show that the implant should preferably be reserved for the restoration of bones not subjected to significant forces or local stresses.

Alveolar ridge augmentation with hydroxylapatite using fibrin sealant for fixation. Part II: Clinical application

The use of fibrin as a resorbable biological adhesive permits moulding of HA granules into individually shaped implants. The binder prevents dislocation of granules during delivery, and the moulded implants securely retain their shape until fibrous tissue ingrowth is complete. Three years of clinical experience have shown that, mouldable fibrin-bound HA has so far proved suitable as a bone substitute in preprosthetic as well as in plastic and reconstructive surgery.

Management of the atrophic anterior maxilla by combined hydroxyapatite augmentation and vestibuloplasty: a pilot study

A technique is described to overcome the problem of the grossly resorbed maxillary alveolus and improve denture wear, by combining augmentation and increased soft tissue cover of the alveolar ridge. Manipulation and placement of the hydroxyapatite was facilitated by use of a hydroxyapatite/collagen composite (HAC) block. The procedure has been carried out in ten patients where extensive resorption contraindicated the use of permucosal implants. Six cases have been followed up for 2 to 3 years. After some initial compaction of HAC the improvement in ridge height has been maintained and long term improvement in denture function obtained.

Extracranial and mandibular augmentation with hydroxyapatite-collagen in induced diabetic and nondiabetic rats

This study evaluated three hydroxyapatite (HA) preparations placed subperiosteally in rats given streptozotocin (70 mg/kg) to induce diabetes (ID) (n = 24) and in nondiabetic (ND) rats (n = 24) used as controls. Implants of 1) nonporous HA granules (HAG), 2) HA granules hand-mixed with bovine collagen (HACM), and 3) HA granules and purified fibrillar collagen in a preprocessed block (PFC-HA) were randomly placed in subperiosteal pockets created on the cranium and adjacent to the left/right mandibles of each rat. Six rats from each group were killed at 3, 6, 12, and 24 weeks postimplantation. Animals killed after 3 weeks showed sporadic bone proliferation and bone resorption, whereas those killed after 6, 12, and 24 weeks showed formation of new bone at the implant/bone interface. Contact of the implant with bone was a requirement for osteogenesis, but bone formed only into the basilar layers of the implants. The ID group showed the greatest inflammatory response as well as the greatest degree of osteogenesis at all intervals of time. The addition of collagen to HA appeared to reduce the inflammatory response. Specimens implanted with HACM showed the least inflammation of the three implanted materials in both ID and ND groups.

Alveolar ridge augmentation in rats by combined hydroxylapatite and osteoinductive material

The purpose of this study was to examine if increased bony ingrowth developed when hydroxylapatite was implanted together with an osteoinductive substrate. Dense hydroxylapatite granules (HA) (Calcitite, Calcitek, San Diego, CA, USA) were mixed with equal volumes of allogenic, demineralized, lyophilized dentin or bone and implanted subperiosteally for alveolar ridge augmentation purposes and heterotopically in the abdominal muscles in rats. Light microscopic evaluation revealed that HA was surrounded by fibrous connective tissue containing foreign body giant cells and it had neither an osteoinductive nor an osteoconductive effect. The newly formed bone induced from the implanted allogenic, demineralized, lyophilized dentin or bone was never found in close contact with the HA and did not incorporate the implant.

Histologic evaluation of the bone/graft interface after mandibular augmentation with hydroxylapatite/purified fibrillar collagen composite implants

Samples of the bone/graft interface were evaluated histologically in five patients 1 year after mandibular ridge augmentation with a composite of hydroxylapatite particles in a matrix of purified fibrillar collagen (HA/PFC). The resulting defects were refilled with HA/PFC after the biopsy specimens were obtained. Histologic examination of the specimens yielded no evidence of purified fibrillar collagen. Hydroxylapatite particles were surrounded by dense fibrous host connective tissue, trabeculae of woven and lamellar bone, or both. HA/PFC was found to be biocompatible with human tissue and receptive to direct bone apposition on the hydroxylapatite particles.

Alveolar ridge augmentation using a new design of inflatable tissue expander: surgical technique and preliminary results

Ridge augmentation with particulate hydroxyapatite (HA) is compromised by the propensity for the HA particles to disseminate throughout any surgically created space within the tissues. Several techniques designed to overcome this problem have been described, including the use of inflatable tissue expanders. Some of the residual problems related to this technique are attributable to aspects of expander design and surgical technique. This paper which describes a new design of tissue expander which is completely submerged in use, also describes in detail the surgical technique associated with it. Preliminary results are discussed.

Biological evaluation of collagen gels containing calcium hydroxide and hydroxyapatite

Dentinal chips and different biocompatible materials have been used in the past as apical plugs to enhance healing and simplify obturation. The purpose of this study was to evaluate bone reactions to implants of hydroxyapatite, collagen, and calcium hydroxide, alone or in different combinations. The materials were implanted bilaterally in the mandibles of 36 guinea pigs and the reactions were compared histologically over a period of 16 wk. No major inflammatory reactions were observed in any of the implant combinations. Hydroxyapatite was not resorbed over the examination periods, but calcium hydroxide and collagen implants were partially or totally resorbed and replaced by bony tissue. The results indicate that cylinders which may be useful as apical plugs can be performed and will heal with minimal biological reactions.

Tissue response to hydroxylapatite in induced diabetic and nondiabetic rats: histologic evaluation

This study evaluated the tissue response to the subcutaneous implantation of nonporous hydroxylapatite (HA) in 24 induced-diabetic (ID) and 24 nondiabetic (ND) rats. One cubic centimeter of HA was implanted subcutaneously in each rat's chest. Subgroups of 6 rats from the ID and ND groups were killed at 3, 6, 12, and 24 weeks postimplantation. The implants were removed with the surrounding soft tissues and processed for histologic evaluation. This revealed that soft tissue inflammation was mild at each time interval. There was a decreased response at 6 months in ND rats and a persistent inflammatory reaction in ID rats. Collagen maturity and fibroplasia increased within ND rats, whereas the ID rats showed a marked delay in collagen maturity and density. No osteogenesis was observed in any specimen. Dystrophic calcification was observed at the HA-tissue interface in 37% of ND and 59% of ID specimens. It was concluded that HA elicited a greater inflammatory response in ID than in ND rats when implated subcutaneously.

Subcutaneous implantation of hydroxylapatite/collagen in induced diabetic and non-diabetic rats

To evaluate tissue reaction to hydroxylapatite (HA) and HA/collagen mixtures in rats with uncontrolled induced diabetes, 48 males were divided: 24 with induced diabetes (ID) from Streptozotocin (70 mg/kg) and 24 non-diabetic (ND) controls. Three subcutaneous sites in each chest were randomly implanted with non-porous HA, or non-porous HA and bovine collagen, or non-porous HA and purified fibrillar collagen. Subgroups of 6 ID and 6 ND rats were killed at 4, 6, 12, and 24 weeks post-implantation. Histologic specimens showed that all materials elicited greater inflammatory response in ID than in ND at all intervals. Each specimen had HA particles encapsulated by host fibrous tissue. Compared to ND, ID specimens had markedly reduced ingrowth and maturity of collagen at each time interval. There was no osteogenesis, but there was dystrophic mineralization within the implant sites in both ID and ND. Mixed HA/collagen exceeded HA alone in maintaining implant contour. In soft tissue, no materials were osteoinductive. Adding collagen did not increase or decrease inflammatory reaction nor improve density and maturity of tissue synthesized around implants.

Overview and historical perspective of oral reconstructive surgery

Pioneers in the field of dental reconstruction had little to offer their edentulous patients other than prostheses that were generally fitted without preparation or augmentation of the alveolar ridge. By the mid-1940s, the development of surgical procedures and the introduction of new materials offered significant advances. Increased denture retention was achieved by some implant methods and through use of the mandibular staple bone plate. Improvements in hydroxylapatite provided a material that could be used for alveolar ridge augmentation. It proved effective in limiting resorption and increasing attachment to soft and hard tissue. The recent development of purified fibrillar collagen in combination with hydroxylapatite enhances our ability to provide effective, long-lasting dental prostheses.

The combined use of endosseous dental implants and collagen/hydroxylapatite augmentation procedures for reconstruction/augmentation of the edentulous and atrophic mandible: a preliminary report

The combination of a relatively new alveolar ridge augmentation material composed of purified fibrillar bovine collagen (PFC) and particulate hydroxylapatite (HA) (Alveoform Biograft Collagen Corp., Palo Alto, Calif.), along with endosseous root form dental implants, was simultaneously placed by a combined flap and tunneling technique to reconstruct and augment endentulous and atrophic mandibles. Prosthodontic and patient surveys reported great satisfaction with overdenture stability, retention, comfort, esthetics, speech, and function. Six reported cases showed that clinically significant alveolar ridge augmentation and form were achieved and maintained with the added prosthetic support and improved stability and retention produced by the combination of procedures. Histologic study of core specimens obtained through the ridge augmentation graft material provided evidence of supracortical bone ingrowth into the graft matrix.

Collagen/hydroxylapatite implant for augmenting deficient alveolar ridges: a 24-month clinical and histologic summary

A new alveolar ridge augmentation material composed of purified fibrillar collagen (PFC) and particulate hydroxylapatite (HA) (Alveoform Biograft, Collagen Corp., Palo Alto, Calif.) was evaluated in the treatment of 77 edentulous patients in a multicenter study. All patients had mandibular augmentation; 22 also had maxillary implant augmentation. Mean ridge height was 15.4 mm before surgery. Twenty-four-month data showed a mean ridge augmentation of 4.1 mm. Prosthodontists rated the ridge firmness "good" to "excellent" in 96.6% of patients after 2 years. All adverse effects with the exception of some residual paresthesia/dysesthesia resolved spontaneously within 24 months. Bone-graft interface samples were examined histologically in five patients 1 year after mandibular ridge augmentation. No evidence of PFC was found, and the HA particles were surrounded by dense, fibrous, host-connective tissue or trabeculae of woven and lamellar bone. Assessment of PFC/HA-augmented ridges at 24 months showed clinically and histologically significant results.

Fibrin glue as cement for HA-granules

An easy, economic and safe method is described for handling HA-granules in recontouring procedures of the alveolar ridge with the help of fibrin glue as a cement.

Technical considerations in mandibular ridge reconstruction with collagen/hydroxylapatite implants

A surgical technique for placement of a collagen-hydroxylapatite implant to augment severely atrophic mandibles is described.

Two-stage combined vestibuloplasty and partial mandibular ridge augmentation with hydroxyapatite

The preliminary results of a new two-stage technique for partial augmentation of the edentulous mandibular ridge with hydroxyapatite are reported. The technique, which has been applied to five patients, can be performed under local analgesia, and involves initial placement of temporary silicone spacers, together with submucous vestibuloplasty to preserve sulcus depth. The spacers are later replaced by dense particulate hydroxyapatite, and the connective tissue capsules that remain after removal of the spacers allow control of particle migration and minimize the amount of hydroxyapatite required.

Use of collagen tubes containing particulate hydroxylapatite for augmentation of the edentulous atrophic maxilla: a preliminary report

Collagen tubes of specific configuration containing particulate hydroxylapatite were placed by a palatal approach to augment edentulous atrophic maxillas. Both the ability to chew and comfort of the denture were improved in the 12 reported cases. Eleven cases showed solidification of the implant between 8 and 16 weeks. There was no problem with particle migration or loss of vestibular height.

Radiographic and microscopic evaluation of subperiosteally implanted blocks of hydroxylapatite-gelatin mixture in rabbits

The efficacy of using gelatin as an adherent of particulate hydroxylapitite was studied by implanting preformed blocks of a hydroxylapatite-gelatin mixture subperiosteally on the buccal aspect of the mandible in rabbits. The rabbits were killed at 1, 2, 4, 12, and 24 weeks after implantation. After radiographic examination, excised specimens were decalcified and examined microscopically. The radiographic findings in the hydroxylapatite-gelatin group were essentially consistent with those of the hydroxylapatite group, except that in the hydroxylapatite group migration of particles was seen in some specimens. Microscopically the majority of the gelatin was unidentifiable at 1 week and there was no evidence of a rejection response. The degree of new bone formation and tissue response in hydroxylapatite-gelatin mixture group was essentially the same as in the hydroxylapatite group. The results indicate that gelatin is an excellent adherent for particulate hydroxylapatite, enabling easy handling and proper placement of the material with no inhibitory effect on new bone formation.

Collagen/hydroxylapatite implant for augmenting deficient alveolar ridges: twelve-month clinical data

In a multicenter study, 77 edentulous patients had mandibular augmentation with implants of purified fibrillar collagen combined with dense hydroxylapatite (Alveoform Biograft); 22 of these patients also had maxillary augmentation. Most patients had Class III or IV mandibular atrophy, and had outpatient surgery with the subperiosteal tunneling technique. Temporary splints were worn for 24 hours post-surgery. Mean ridge height was 15.3 mm before surgery and 19.5 mm after 12 months, an augmentation of 4.2 mm. Predictable compaction occurred largely in the first few months after denture loading. Most patients, surgeons, and prosthodontists assessed the results of the procedure as good to excellent at 1 year following implantation. Adverse experiences, largely dehiscence and paresthesia, tended to resolve over time. Sera from ten patients demonstrated antibodies to bovine collagen that were not clinically significant. Alveolar augmentation with collagen/hydroxylapatite achieved clinically significant results that compared favorably with those achieved with other types of ceramic implants.

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

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