Histologic study of tissue response to implanted hydroxylapatite in two patients

Does the Use of High-Temperature-Processed Xenografts for Ridge Augmentation Result in Ridge Width Stability Over Time?

PURPOSE

Alveolar ridge augmentation is often required before implant placement. The purpose of the present study was to determine whether maxillary and mandibular ridge augmentation with a high-temperature xenograft remains stable over time.

MATERIALS AND METHODS

A retrospective case series was performed of subjects who had undergone maxillary anterior or posterior ridge augmentation with a high-temperature xenograft (HTX). The primary predictor variable was the HTX. The primary outcome variable was the ridge width, measured T0 (before augmentation), T1 (immediately after augmentation), T2 (4 to 6 months after augmentation), and T3 (>4 years after augmentation). The secondary outcome variable was implant success. Analysis of variance and linear regression analysis were used to determine significance. A P value < .05 was considered statistically significant.

RESULTS

A total of 31 patients (age, 52.4 ± 18 years; 61.3% women) were identified who had undergone ridge width augmentation performed using HTX. Of these, 23 had cone-beam computed tomography scans available 4 to 10 years after augmentation had been performed. At the anterior maxilla, the initial ridge augmentation (T1) was 4.7 ± 1.3 mm, which had decreased to 3.7 ± 1.0 mm within 6 months of augmentation (T2) and to 3.3 ± 1.1 mm after an average of 7 years (T3) of follow-up (P < .05). At the posterior mandible, the initial ridge augmentation was 5.4 ± 0.9 mm, which had decreased to 4.1 ± 0.7 mm within 6 months of augmentation and to 3.5 ± 1.0 mm at an average of 7 years of follow-up. A total of 61 implants had been placed in these 23 patients, 3 (4.9%) of which had failed to integrate.

CONCLUSIONS

The use of HTX does result in long-term stability for ridge augmentation.

Characteristics and osteogenic effect of zirconia porous scaffold coated with β-TCP/HA

PURPOSE

The purpose of this study was to evaluate the properties of a porous zirconia scaffold coated with bioactive materials and compare the in vitro cellular behavior of MC3T3-E1 preosteoblastic cells to titanium and zirconia disks and porous zirconia scaffolds.

MATERIALS AND METHODS

Titanium and zirconia disks were prepared. A porous zirconia scaffold was fabricated with an open cell polyurethane disk foam template. The porous zirconia scaffolds were coated with β-TCP, HA and a compound of β-TCP and HA (BCP). The characteristics of the specimens were evaluated using scanning electron microscopy (SEM), energy dispersive x-ray spectrometer (EDX), and x-ray diffractometry (XRD). The dissolution tests were analyzed by an inductively coupled plasma spectrometer (ICP). The osteogenic effect of MC3T3-E1 cells was assessed via cell counting and reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

The EDX profiles showed the substrate of zirconia, which was surrounded by the Ca-P layer. In the dissolution test, dissolved Ca(2+) ions were observed in the following decreasing order; β-TCP > BCP > HA (P<.05). In the cellular experiments, the cell proliferation on titanium disks appeared significantly lower in comparison to the other groups after 5 days (P<.05). The zirconia scaffolds had greater values than the zirconia disks (P<.05). The mRNA level of osteocalcin was highest on the non-coated zirconia scaffolds after 7 days.

CONCLUSION

Zirconia had greater osteoblast cell activity than titanium. The interconnecting pores of the zirconia scaffolds showed enhanced proliferation and cell differentiation. The activity of osteoblast was more affected by microstructure than by coating materials.

Histologic evaluation of a hydroxyapatite onlay bone graft retrieved after 9 years: a clinical report

Because of the limited observations of published studies, the condition of hydroxyapatite after a long period of intraoral function remains a concern. This clinical report describes the histologic evaluation of a 9 year-old hydroxyapatite specimen retrieved from a human subject. The residual hydroxyapatite particles showed no sign of resorption, and tight contact with the surrounding bone was observed.

The effects of bone chips dehydrated with solvent on healing bone defects

The effect of bone chips dehydrated with solvent on the healing of bone defects was evaluated. Solvent-dehydrated spongiose bone chips were placed in experimentally formed cavities in the right back tibia of rabbits. After 10, 20 and 30 days, histopathological cross-sections from the bone grafts were examined microscopically for bone healing and formation of spongiose bone, cortex and bone marrow. Spongiose bone chips had a positive and accelerating influence on the healing of bone defects in the 10-day period after transplantation, but no significant differences were observed between the treated and control groups 20 and 30 days after transplantation.

Multi-center clinical comparison of combination anorganic bovine-derived hydroxyapatite matrix (ABM)/cell binding peptide (P-15) and ABM in human periodontal osseous defects. 6-month results

BACKGROUND

Intraosseous periodontal defects present a particular treatment problem. New bone replacement grafts offer promise for improved results.

METHODS

The role of a synthetic cell-binding peptide (P-15), combined with anorganic [corrected] bovine-derived hydroxyapatite bone matrix (ABM), was compared to ABM alone in human periodontal osseous defects in a controlled, monitored, multi-center trial. Following appropriate initial preparation procedures, flap surgery with defect and root debridement was performed. Two osseous defects per patient were treated randomly with each procedure after surgical preparation. Appropriate periodontal maintenance schedules were followed, and at 6 to 7 months, re-entry flap surgery was performed for documentation and finalization of treatment.

RESULTS

T test and Mann-Whitney U analyses of patient mean values from 33 patients revealed that the combination ABM/P-15 grafts demonstrated significantly better mean defect fill of 2.9 +/- 1.2 mm (72.9%) versus a mean defect fill of 2.2 +/- 1.4 mm (50.67%) for defects treated with ABM (P<0.05). Other hard tissue findings showed similar clinically superior results with the use of ABM/P-15. Relative defect fill results showed 81% positive (50% to 100% defect fill) responses with ABM/P-15 and 67% positive responses with ABM. There were 3.5 times as many optimal results (> or = 90% defect fill) with ABM/P-15 and twice as many failures (minimal response) with ABM. Soft tissue findings showed no significant differences between treatments.

CONCLUSIONS

These results suggest that the use of the P-15 synthetic cell-binding peptide combined with ABM yields better clinical results than the ABM alone in intrabony periodontal defects.

Multi-center clinical evaluation of combination anorganic bovine-derived hydroxyapatite matrix (ABM)/cell binding peptide (P-15) as a bone replacement graft material in human periodontal osseous defects. 6-month results

A synthetic cell-binding peptide (P-15) combined with anorganic bovine-derived hydroxyapatite bone matrix (ABM) was compared to demineralized freeze-dried bone allograft (DFDBA) and open flap debridement (DEBR) in human periodontal osseous defects in a controlled, monitored, multi-center trial. Following appropriate initial preparation procedures, flap surgery with defect and root debridement was performed. Three osseous defects per patient were treated randomly with one of three procedures after surgical preparation. Appropriate periodontal maintenance schedules were followed, and at 6 to 7 months re-entry flap surgery was performed for documentation and finalization of treatment. Analysis of variation (ANOVA) and t test analyses of patient mean values from 31 patients revealed that the combination ABM/P-15 grafts demonstrated significantly better mean defect fill of 2.8 +/- 1.2 mm (72.3%) versus a mean defect fill of 2.0 +/- 1.4 mm (51.4%) for defects treated with DFDBA (P <0.05) and a mean defect fill of 1.5 +/- 1.3 mm (40.3%) (P <0.05) for defects treated with DEBR. Other hard tissue findings showed similar clinically superior results with the use of ABM/P-15. Relative defect fill results showed 87% positive (50% to 100% defect fill) responses with ABM/P-15, 58% positive responses with DFDBA, and 41% positive responses with DEBR. There were 8 to 9 times more failures (minimal response) with DFDBA and DEBR (26% to 29% frequency) than with ABM/P-15. Soft tissue findings showed no significant differences among treatments except for greater clinical attachment level gain with ABM/P-15 compared to DEBR. These results suggest that the use of the P-15 synthetic cell-binding peptide combined with ABM yields better clinical results than either DFDBA or DEBR. Further studies are needed to determine the relative roles of the ABM and/or the P-15 in these improved results.

Long-term stability of atrophic ridges reconstructed with hydroxylapatite: a prospective study

PURPOSE

This article reports the results of an investigation of the long-term efficacy and stability of reconstructive surgery of atrophic ridges using dense hydroxylapatite (HA).

PATIENTS AND METHODS

Subperiosteal HA was used as a first stage of reconstruction in 678 ridges, 645 mandibular and 35 maxillary, followed after 4 to 5 weeks by a total lowering of the floor of the mouth, vestibuloplasty, and skin graft in the mandible: a same-stage submucous vestibuloplasty was done in the maxilla. Patients were followed for an average of 5.3 +/- 2.7 years by the same surgical and prosthodontic team. The presence of severe or moderate radiographic change was analyzed in relation to gender, age, severity of atrophy, postoperative complications, clinical changes, patient satisfaction, and type of HA particles used alone or with a binder.

RESULTS

Seventy-seven percent of cases had no observable radiographic changes, 13% had moderate changes, and 10% had severe changes, of which fewer than half also had severe clinical changes. Relationships were established between the presence of radiographic change and certain parameters, especially postoperative delay in healing, severe or moderate clinical changes, and type of HA particles used.

CONCLUSION

Hydroxylapatite, when used alone or with binding agents, and in association with basic techniques of reconstructive surgery and soft tissue handling, is a predictable and stable biomaterial for ridge reconstruction.

Reaction of the dental pulp to hydroxyapatite

The purpose of this study was to evaluate the action of hydroxyapatite (HA) (Osteogen HA Resorb, GBD Marketing Group Inc., Valley Stream, N.Y.) on the dental pulp of rats. Four upper molar pulps in 45 rats were exposed and capped with synthetic HA (Osteogen) with a stereoscopic microscope. Pulps capped with calcium hydroxide (Dycal, L.D. Caulk Co., Milford, Del.) served as controls. The cavities were filled with amalgam, and the molars on each side of the maxilla were protected by the placement of a pedodontic steel crown. Pulp inflammation and dentin repair were compared by histologic observations and computer image analysis after 7, 14, and 28 days. After 7 days a partial acute pulpitis were observed in specimens treated with Osteogen or Dycal. Reparative dentin formation along the pulp walls was also seen. After 14 days the pulpitis was more extensive in the Osteogen-treated teeth than in the control teeth. Dentin formation as measured by morphometric analysis was more pronounced in Osteogen-treated teeth. Neo-odontoblasts were observed after the use of both materials. After 28 days an acute inflammatory reaction was still evident in the Osteogen-treated group. A complete dentinal bridge was observed more frequently with Dycal than with Osteogen. Despite the putative abilities of HA to be osteoconductive, osteogenic, and dentinogenic, the results of this study indicate that it should not be used as a pulp-capping agent because of its tendency to cause scattered dystrophic calcification in the dental pulp, which could interfere with future endodontic treatment.

Electron microscope characteristics of dentin repair after hydroxylapatite direct pulp capping in rats

In order to study the osteogenic action of hydroxylapatite (HA) on the dental pulp, a pulp capping experiment was designed using the rat upper molar. Under general anesthesia, molar teeth in 14 male Sprague-Dawley rats were pulp capped with Osteogen (HA) or with Dycal as a control material. After pulp capping, the maxillary molars cavities were restored with amalgam and a pedodontic steel crown was adjusted and sealed over the molar teeth on either side of the maxilla. After 7 days, the areas of necrosis and acute inflammation were more evident in the pulps treated with Dycal than with Osteogen. Hard tissue formation began to appear around dentinal chips in the pulp and extended from the cavity walls into the pulp regardless of the material that was used. Furthermore, this calcified material was scattered throughout the pulp when Osteogen was used, but was not observed in the Dycal treated pulps. The hard tissue formation was thought to be due to the putative fibroblasts and odontoblasts found in the pulp. After 28 days dense dentinal tissue was observed bridging the exposure site when Dycal was used. The dentinal tissues formed with Osteogen was always of a globular type, and showed an irregular distribution. Since Osteogen tends to cause areas of dystrophic calcification in the pulp, its use is not be recommended for pulp capping purposes in humans, because these areas of calcification would make future endodontic treatment difficult.

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.

Bone replacement with porous hydroxyapatite blocks and titanium screw implants: an experimental study

The aim of this experimental study was to examine whether porous hydroxyapatite (HA) blocks, fixed with titanium screw implants, could be used as a bone graft substitute. Twenty minipigs received coralline HA blocks for augmentation of surgically created defects in edentulous mandibles. Each block was fixed with two titanium screw implants. Two types of porous HA blocks that differed in pore diameter were used. A high rate of HA loss occurred in the group of animals that had received the HA block with small pore sizes, and fractures of the block occurred in the vicinity of the titanium implants in 12 of the remaining 13 cases. Histologic examination showed that the HA blocks with larger pore size were homogenously penetrated by bone that extended into the central pores and even incorporated the dislocated block fragments. The titanium implants were in close contact with the newly formed bone in these blocks. Little contact between bone and implants was seen in the HA blocks with the smaller pore size. The results indicate that, with improved mechanical properties, a combined augmentation with porous HA blocks and screw implants may be useful in primary reconstruction of bone defects.

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.

Human tissue response to porous hydroxyapatite implants. A case report

Histological examination of 2 porous hydroxyapatite implants removed from a patient showed a pattern of ossification similar to that reported in a previous animal study. New bone was laid down on the surface of the hydroxyapatite but did not progress to occupy all the pores. Although porous hydroxyapatite blocks are biocompatible and well tolerated by the tissues, they are not recommended for augmentation of the resorbed alveolar ridge where the overlying mucosa is thin and atrophic, because of the risk of mucosal dehiscence and implant exposure. They are suitable in situations where they are deeply buried in the tissues and not subjected to direct trauma.