Porous hydroxylapatite as a bone graft substitute in mandibular contour augmentation: a histometric study

The buccal contour of the mandible was augmented in 17 dogs with 5 X 7.5 X 20 mm blocks of porous hydroxylapatite (HA) on one side and two-layered split rib autografts on the other. Both specimens were retrieved at three, six, 12, 24, and 48 months. Undecalcified sections were prepared for microradiography, light and UV microscopy, and histometry. A transmitted light video image digitizing system was used to trace implant and graft perimeters and calculate cross sectional areas. This system was also used to measure graft density and calculate bone and soft tissue compositions. The HA matrix, bone and soft tissue compositions of implant specimens were measured with a backscattered scanning electron microscope imaging digitizing system. All grafts became increasingly resorbed with time whereas all implants remained intact. Mature osteotonic bone ingrowth was present in all implants except one which failed to unite with the mandibular cortex. The mean graft areas decreased from 30.8 mm2 at three months to 0.7 mm2 at 48 months, while the implant areas averaged 35.5 mm2 and remained stable. The graft specimens were composed of 46.6% bone and 53.4% soft tissue or fluid space. The implant specimens were composed of 34.5% HA matrix, 28.6% bone, and 33.9% soft tissue. The HA matrix had a surface area of 9.8 mm2/mm3 that was 61.9% covered with bone ingrowth and 38.1% covered with soft tissue or fluid space. In contrast to the rapid resorption of graft onlays, the porous HA matrix demonstrated a long-term permanence with maintenance of contour and osseous incorporation over the four-year duration of this study.     

Histologic evaluation of threaded HA-coated root-form implants after 3.5 to 11 years of function: a report of three cases

This article presents a histologic evaluation of three hydroxyapatite (HA)-coated root-form implants retrieved from humans after being in function for 3.5 to 11 years. If the coronal portion, where bone loss was observed clinically and radiographically, is excluded, all implants appeared to be well osseointegrated, with intimate contact between the surrounding bone and the coating. There was no sign of resorption or dissolution of the HA coating. The coating had a uniform thickness (50 microm) equal to the thickness originally provided by the manufacturer In the few areas where there was no bone contact, the HA coating appeared to line the implant with no sign of dissolution. The few detached particles had tight contact with the bone, demonstrating the biocompatibility of the HA. The observations from the three reported cases suggest that the HA coating of dental implants may not be susceptible to resorption or dissolution under long-term function.     

Histologic evaluation of hydroxyapatite-coated root-form implant retrieved after 7 years in function: a case report

This case report presents a clinical, radiographic, and histologic evaluation of 2 non-adjacent, hydroxyapatite-coated, root-form implants retrieved from the maxillary canine area of a patient after 7 years in function. Clinical examination revealed immobile implants with no sign of pathosis. Radiographic examination indicated close proximity of the bone to the implant surface without evidence of radiolucency. Histologically, the 2 implants appeared to be well integrated with the surrounding bone; 84% of the surface of the first implant and 79% of the surface of the second implant had close bone apposition at the interface. There was no evidence of dissolution of the hydroxyapatite coating. The bone appeared to be in immediate contact with the coating. These observations suggest that a particular hydroxyapatite coating on root-form implants can resist degradation during long-term function.     

Two human hydroxyapatite-coated dental implants retrieved after a 14-year loading period: a histologic and histomorphometric case report

BACKGROUND: Controversy over the long-term clinical effectiveness of hydroxyapatite (HA)-coated dental implants still persists, despite numerous clinical studies documenting high survival rates. Concerns about the degradation of the coating over the years have been raised; it has been speculated that resorption of the HA could produce a space between the implant and the bone with a resultant mechanical instability. METHODS: Two HA-coated implants were retrieved due to a fracture of the abutment screws after a loading period of 14 years and were treated to obtain thin ground sections for histologic evaluation. RESULTS: At low-power magnification, it was possible to observe that the HA coating was in contact with mature bone. No gaps or connective fibrous tissue was found at the implant-bone interface. No epithelial downgrowth was present. No acute or chronic inflammatory cell infiltrate was present at the implant-bone interface. No foreign body reaction was present in the peri-implant tissues. Some osteocytes were in direct contact with the coating. For implant 1, the percentage of bone-titanium contact was 25% +/- 2.1%, and the percentage of bone-HA contact was 35% +/- 1.4%. The total bone-implant contact was approximately 60%. The HA coating appeared to be resorbed in 46% +/- 3.2% of the implant perimeter, especially in the coronal portions of the implant. For implant 2, the mean percentage of bone-HA contact was 13% +/- 1.8%, and the mean percentage of bone-titanium contact was 15% +/- 2.3%. The total bone-implant contact was approximately 28%. The HA coating appeared to be resorbed for a mean of 68% +/- 4.1% of the implant perimeter, especially in the coronal portion of the implant. CONCLUSIONS: No acute or chronic inflammatory cell infiltrate was present in the peri-implant tissues. No signs of coating infection, fatigue, or failure were observed in two specimens. The HA coating may not be susceptible to degradation or dissolution under long-term function.     

Osteoconduction of a stoichiometric and bovine hydroxyapatite bilayer-coated implant

Objective: To impart rapid and durable osteoconductivity to implants, a commercial titanium screw implant was coated with stoichiometric hydroxyapatite (HA; 50 nm thick), and then with bovine hydroxyapatite (B‐HA; 300 nm thick) using the pulsed laser deposition technique. As control specimens, a commercial implant coated with HA (20 μm thick) using the flame spraying method (sprayed implant) and a simple titanium implant (basic implant) was used. Methods: The osteoconductivities of these three types of implant, after implantation for 4–24 weeks, were histologically evaluated. Results: Peeling of HA from the sprayed implant was observed by scanning electron microscopic observation. In the fourth postoperative week, the bilayered implant was already closely adhered to bone. On the other hand, the basic implant was surrounded by a gap containing connective tissue. With the sprayed implant, the bone adhered to the thick HA coating. Conclusion: The bilayer deposition technique supplies quick and long‐term fixation of implants to bone, because the B‐HA film dissolves to aid osteoconduction right immediately after implantation and the HA thin film maintains osteoconduction without dissolution. Neither of the thin‐film fractures easily compared with thick coatings. To cite this article:
Hayami T, Hontsu S, Higuchi Y, Nishikawa H, Kusunoki M. Osteoconduction of a stoichiometric and bovine hydroxyapatite bilayer‐coated implant.
Clin. Oral Impl. Res. 22 , 2011; 774–776
doi: 10.1111/j.1600‐0501.2010.02057.x     

The effect of non-resorbable membrane on buccal bone healing at an immediate implant site: an experimental study in dogs

Objective: For successful implant treatment in the esthetic area, stable hard tissue and soft tissue are very important. At the buccal side without buccal bone defects, prophylactic guided bone regeneration (GBR) with bone substitute was frequently used for achieving thick buccal bone. The aim of this study was to evaluate the effect of GBR using a non‐resorbable membrane in an immediate implant site without bone defects. Material and methods: Immediate implants were placed into the mandibles of four mongrel dogs. In the experimental group (TM group), a non‐resorbable membrane was placed and fixed onto the buccal bone plate around the implant. In the control group, the implants were placed without membrane coverage. After 12 weeks, the dogs were sacrificed and histological specimens were prepared. The vertical distances from the smooth–rough surface interface (SRI) to the gingiva, the first‐bone contact, and the bone crest were measured on the buccal and lingual sides. The horizontal thicknesses of the gingiva and bone at 0, 1, 2, and 3 mm below the SRI were measured. Results: In the TM group, first‐bone contact on the buccal side was more coronally positioned approximately 0.8 mm than the control group (P=0.041). The buccal bone thickness of the TM group was well preserved and there was no difference between the buccal and lingual sides. Comparing the control group, implants of the TM group had 1 mm thicker buccal bone (P=0.0051 at bone 1 mm level, P=0.002 at bone 2 mm level). In the control group, buccal bone loss was observed and buccal bone was about 1 mm thinner than the lingual bone (P<0.05). Conclusions: GBR with a non‐resorbable membrane and no bone graft substitute could help to preserve buccal bone thickness on the immediate implant site without defects. To cite this article:
Park S‐Y, Kye S‐B, Yang S‐M, Shin S‐Y. The effect of non‐resorbable membrane on buccal bone healing at an immediate implant site: an experimental study in dogs.
Clin. Oral Impl. Res. 22 , 2011; 289–294.
doi: 10.1111/j.1600‐0501.2010.01995.x     

Influence of the 3-D bone-to-implant relationship on esthetics

There are biologic limits of the soft tissue dimension around implants; therefore, the limiting factor for the esthetic result of implant therapy is the bone level at the implant site. Clinicians must focus on the 3-D bone-to-implant relationship to establish the basis for an ideal and harmonic soft tissue situation that is stable over a long period. In some situations, missing bone is a limiting factor for esthetics; in others, it is possible to regenerate new bone around implants. As a certain amount of bone resorption occurs around implants as soon as the implant is in contact with the oral environment, the distance between an implant and adjacent tooth, as well as the distance between two implants, is as important as the bone volume on the buccal side of the implant head and in the papillary area, especially for the long-term result. This article discusses the 3-D bone-to-implant relationship and its influence on soft tissue esthetics around implants.     

Histological evidence of osseointegration in human retrieved fractured hydroxyapatite-coated screw-type implants: a case report

Histological evidence of clinically successful dental implants is very rare. This case report presents histological evidence of osseointegration in human implants retrieved because of fractures at the connected portion between the abutments and fixtures due to a car accident. The duration of functional loading of the implants was 18 months. Two hydroxyapatite (HA)-coated screw-type implants were removed with part of the healthy bone from the mandibular left molar region. A block was prepared using cutting and grinding equipment to obtain a central section approximately 50 microm thick, which was stained with basic fuchsin and methylene blue. Histological examination revealed that the bone was dense and in close relation with the HA coating of the implants. The interspaces of each thread of the implant were filled with mineralized bone. Peri-implant soft tissue was not observed in the section. A high degree of osseointegration was noted, with a bone-to-implant contact of 87.5% (implant corresponding to tooth 36) and 97.4% (implant corresponding to tooth 37). The connection between the 30 and 50 microm HA coating and the metal was uniformly tight and constant. In conclusion, the histological evidence showed a high degree of osseointegration in two HA-coated screw-type dental implants retrieved after functional loading for 18 months.     

Surface modification by cold-plasma technique for dental implants—Bio-functionalization with binding pharmaceuticals

Since biomaterials contact many different tissues, those materials must have optimum surface compatibility with the host bone tissue and soft tissue, as well as anti-microbial properties on an exposed region of the mucosa. Such materials can be created under well-controlled conditions by modifying the surfaces of materials that contact those tissues. This paper is focused on the surface modification of biomaterials for developing “Bio-functional dental implants”, which are compatible with all host tissues, using a cold-plasma technique.At the bone tissue/implant interface, a thin calcium phosphate coating and rapid heating with infrared radiation were effective in controlling the dissolution without cracking the coating. These thin calcium phosphate coatings may directly promote osteogenisis, but also enable immobilization and subsequent drug delivery system (DDS) of bisphosphonates. Simvastatin is also an effective candidate that is reported to increase the expression of BMP-2. The thin-film of hexamethyldisiloxane (HMDSO) was plasma-polymerized onto titanium, and then HMDSO surface was activated by O₂-plasma treatment. A quartz crystal microbalance (QCM-D) technique demonstrated that simvastatin was immobilized on the plasma-treated surfaces due to introduction of O₂-functional groups. At the soft tissue/implant interface, multi-grooved surface topographies and utilizing the adhesive proteins such as fibronectin or laminin-5 may help in providing a biological seal around the implant. At the oral fluid/implant interface, an alumina coating, F⁺-implantation and immobilization of anti-microbial peptides were responsible for inhibiting the biofilm accumulation.     

Immediate implant placement using a biodegradable barrier, polyhydroxybutyrate‐hydroxyvalerate reinforced with polyglactin 910. An experimental study in dogs.

The purpose of this study was to evaluate the use of a biodegradable membrane of polyhydroxybutyrate-hydroxyvalerate copolymer reinforced with polyglactin 910 fibers, as an occlusive barrier over implants placed into fresh extraction sockets. Ten dogs had the 3rd and 4th mandibular premolars extracted bilaterally. Each dog had 4 Astra Dental Implants® placed directly into the fresh extraction sockets. The top of the fixtures was placed at the same level as the top of the buccal cortical bone. The two implants in the right side were covered with the hydrolyzable polyester material (polyhydroxybutyrate‐hydroxyvalerate reinforced with polyglactin 910 fibers; PHB‐HVIPG). and the 2 implants in the left side were controls without occlusive membranes. Soft tissue dehiscences were registered for half of the implants in the test side but were not noted in the control side. The histomorphological measurements after 12 weeks showed that the mean distance from the top of the fixtures to the first bone‐to‐implant contact was significantly greater than for the control side. The membrane‐covered implants without dehiscences showed also significantly less bone fill compared with the control side. Inflammatory cell infiltrates were seen adjacent to all PHB‐HVIPG membranes, and frequently the membrane material was surrounded by a fibrous tissue capsule. The polyester membranes used in this study interfered with the marginal bone healing adjacent to the immediately placed implants. An increased inflammatory reaction and significantly less marginal bone healing was registered in the membrane side compared with the control side.     

Stability of the mucosal topography around single-tooth implants and adjacent teeth: 1-year results

This study evaluated the soft tissue stability around 10 single-tooth implants. All cases were treated following the same protocol, which included guided bone regeneration and connective tissue grafting. One year after prosthesis insertion the soft tissue shrinkage on the buccal side of the implant crown was 0.6 mm on average. The soft tissue volume in the papilla area increased on average by 0.375 mm, and none of the papillae lost volume.     

Ultrastructural in vitro characterization of a porous hydroxyapatite/bone cell interface

In order for the hydroxyapatite implant material interface to new bone to be characterized, osteogenic mouse calvarial mesenchymal cells were grown in vitro in contact with a porous hydroxyapatite (PHA). After the mesenchymal cell culture was incubated for 12 to 13 days, the resulting tissue-containing bone colonies were fixed, embedded, sectioned, and stained for microscopic evaluation. Light and transmission electron microscopy (with conventional staining) and phosphotungstic acid cytochemistry were used to explore and record the optical microscopic and ultrastructural interfaces at the hydroxyapatite surface. Osteoblasts, fibroblasts, bone, and cartilage were observed and photographed at the implant surface. Osteoblasts found in conjunction with well-developed collagen, matrix vesicles in the extracellular matrix, and newly formed hydroxyapatite crystals on the PHA surface confirmed the beginning of woven bone formation. Collagen fibers were observed directly in contact with the PHA when osteoblasts were present. Polysaccharides were localized among the collagen fibers in the implant-cell extracellular space, indicating a rich complex carbohydrate layer in relation to the collagen of immature bone. Fibroblasts and chondroblasts at the implant surface secreted no collagen, but an amorphous layer was visible between the fibroblasts and the implant surface. When polysaccharides were stained, an electron-dense film appeared where the amorphous layer came into contact with the implant material. Collagen was secreted from the cell surface furthest from the implant. Osteoblasts and fibroblasts/chondroblasts, when surrounding PHA, seem to take on two different interfacial functions: Osteoblasts secrete collagen in a bone-initiating extracellular matrix with carbohydrates at the implant surface, whereas fibroblasts/chondroblasts appear to attach to the implant with a carbohydrate-rich attachment substance, but with no collagen at the interface. This study confirms in vivo data that PHA is a viable implant material because it is biocompatible and, unlike several other materials, appears to stimulate, or at least to permit, osteogenesis.     

Human histologic and histomorphometric analyses of hydroxyapatite-coated implants after 10 years of function: a case report

PURPOSE: No consensus exists on the long-term performance of hydroxyapatite (HA) coatings on dental implants. The aim of this study was to evaluate the long-term stability of the HA coating in a human autopsy specimen. MATERIALS AND METHODS: Two mandibular HA-coated implants were retrieved postmortem from a woman after 10 years of functional loading with an implant/tooth-supported fixed partial denture. After ground sectioning, the specimens were histomorphometrically analyzed. RESULTS: Direct bone-implant contact was found at 78.48% of the implant surface. HA coating disappearance had occurred in a few areas (22.75%), but bone was in direct apposition to the titanium surface. Bone volume measured 27.66%, and expected bone-implant contact was 37.55%. No inflammatory reaction was seen in the supracrestal soft tissues or the bone compartment. DISCUSSION: Most of the HA coating was maintained on the implants, and areas lacking HA were directly apposed by bone. This observation suggests that the underlying titanium surface should have a macro-texture to promote the adaptation of bone to the titanium surface in case of HA disappearance, as well as to decrease failure at the HA-titanium interface. CONCLUSIONS: In a patient in whom prosthetic treatment was appropriately performed and proper plaque control was maintained, the HA coating was not damaged and contributed to the success of the implant over 10 years of clinical functioning.     

Immunohistochemical characterization of wound healing at two different bone graft substitutes

The immunohistochemical characteristics of wound healing following application of a biphasic calcium phosphate or a collagen coated natural bone combined with a native collagen membrane in a dog model was assessed. Standardized buccal dehiscence-type defects were surgically created following implant bed preparation in 6 dogs. Following implant placement, defects were randomly filled with a collagen coated natural bone mineral (GBO), or a biphasic hydroxyapatite/beta tricalcium phosphate (SBC), and covered with a native collagen membrane. After 1, 4, and 9 weeks' submerged healing, dissected blocks were processed for immunohistochemical (collagen type I (CI), osteocalcin (OC), angiogenesis (TG)) analysis. At 1 week, GBO and SBC granules were homogeneously surrounded by a well vascularized, non-mineralized tissue (NMT). CI and OC antigen reactivity was commonly observed adjacent to both bone graft substitutes. At 4 and 9 weeks, SBC and GBO granules were completely integrated into a secondly formed network of spongiosa. At 9 weeks, dissolution of some granules was observed in the SBC group. Adjacent to these granules, NMT was significantly increased and revealed a pronounced CI, OC and TG antigen reactivity. The initial pattern of bone regeneration and graft integration was comparable in both groups; bone remodelling was more pronounced with SBC.     

Extraction sockets and implantation of hydroxyapatites with membrane barriers: a histologic study

The purpose of this pilot study was to investigate the effect on extraction socket healing when an absorbable hydroxyapatite (AH) and a nonabsorbable anorganic bovine bone mineral (ABB) covered with either an acellular dermal matrix allograft (ADMA) or expanded polytetrafluoroethylene (ePTFE) membrane barrier were left exposed to the oral cavity. Following tooth extraction, a total of 16 sockets in 15 patients with deficient buccal plates of > or =5 mm were randomly divided into 4 treatment groups: 1) AH covered with ADMA, 2) AH covered with an ePTFE membrane, 3) ABB covered with ADMA, and 4) ABB covered with an ePTFE membrane. Primary coverage was not attempted or obtained in any of the 16 treated sockets. Six to 8 months postextraction at the time of implant placement, histologic cores of the treatment sites were obtained. These cores were processed, stained with Stevenel's blue/van Gieson's picro fuchsin, and histomorphometrically analyzed. Vital bone, connective tissue and marrow, and residual graft particles were reported as a percentage of the total core. The mean vital bone was 34.5% (AH with ADMA), 41.7% (ABB with ADMA), 27.6% (ePTFE and AH), and 17.8% (ePTFE and ABB). The average percentage of vital bone in the 8 sockets covered with ADAMA was 38% compared with an average percentage vital bone of 22% in the 8 sockets covered with ePTFE membrane barriers. Because of the small number of specimens in the 4 groups, statistical analysis was not possible. However, in this pilot study, ADMA-covered sites resulted in more vital bone present 6 to 8 months postsocket treatment than obtained in the ePTFE-covered sites regardless of bone replacement materials used. Further research is warranted to see if these results show a similar difference in bone-to-implant contact after implant placement.     

2种不同种植体植入对种植体周围软组织的影响

目的: 研究2种种植体对种植体周围软组织的影响。方法: 选择2020年12月—2021年2月普陀区眼病牙病防治所收治的单颗后牙缺失且需行种植修复的患者40例,其中植入骨水平种植体10例,软组织水平种植体30例。在完成种植冠修复当天、3个月、6个月及12个月时比较2组种植体的探诊深度,检测种植体龈沟液中天冬氨酸转氨酶（AST）和碱性磷酸酶（ALP）水平。采用SPSS 17.0软件包对数据进行统计学分析。结果: 修复完成当天、3个月、6个月及12个月,软组织水平种植体的探诊深度和ALP水平均显著低于骨水平种植体（P<0.05）。其中修复完成当天,软组织水平种植体的AST显著低于骨水平种植体（P<0.05）。随着时间增加,骨水平种植体龈沟液中的AST迅速降低,最后与软组织水平种植体接近（P>0.05）。结论: 尽管骨水平种植体和软组织水平种植体均具有良好的临床使用效果,但软组织水平种植体周围的软组织表现出更好的稳定性。     

Bone regeneration in alveolar bone dehiscences produced by jiggling forces

The aim of this experiment was to achieve support for the hypothesis that bone resorption, induced by jiggling forces, leaves a component within the supracrestal soft tissue with a capacity of reforming bone. The maxillary lateral incisors and first premolars and the mandibular second premolars in two monkeys were used in the study. Using metal pins inserted into the neighboring teeth as retainers, orthodontic elastics were stretched and placed alternately around the buccal and lingual surfaces of each experimental tooth in order to produce jiggling forces. After 5 months of continuous jiggling, when bone dehiscences were produced on the buccal aspect of the teeth, the elastics were removed. After repositioning of the teeth a split thickness flap was raised. On one side of the jaw the soft tissue within the bone dehiscences was removed. At the contralateral teeth a sham operation was performed maintaining the soft tissue within the bone dehiscences. The monkeys were sacrificed 6 months after surgery. Tissue blocks containing test and control specimens were dissected free and prepared for microscopic analysis. The length of the supracrestal connective tissue attachment and the amount of coronal bone regeneration were assessed in the histological sections. It was found that buccal alveolar bone, reduced in height by jiggling forces, regenerated after discontinuation of the forces. When the soft tissue within the buccal bone dehiscences produced by the jiggling forces was surgically removed, the coronal regeneration of the alveolar bone was markedly reduced. These observations suggest that bone resorption, induced by jiggling forces, leaves a soft tissue component with a capacity of forming bone.     

Peri-implant bone tissue strains in cases of dehiscence: a finite element study

When patients with a narrow alveolar bone ridge are treated with oral implants, a dehiscence can occur. The lack of bony support at the buccal or lingual side of the implant may present an unfavourable situation from a biomechanical point of view. The hypothesis as to whether the presence of dehiscence leads to an increased risk of marginal bone overload was tested by means of the finite element method. Three different situations for a cylindrical oral implant, which was placed in a mandible, were modelled: i) no dehiscence, ii) a dehiscence at the buccal side and iii) dehiscences at the buccal and lingual sides. It was found that the presence of buccal and/or lingual dehiscences led to a marked increase in marginal bone strains at the mesial and distal sides of the implant, thus increasing the risk of bone tissue overload at these locations. Marginal bone strains at the buccal and/or lingual sides, however, did not increase.     

Tissue modeling following implant placement in fresh extraction sockets

OBJECTIVE: To study whether osseointegration once established following implant placement in a fresh extraction socket may be lost as a result of tissue modeling. MATERIAL AND METHODS: Seven beagle dogs were used. The third and fourth premolars in both quadrants of the mandible were used as experimental teeth. Buccal and lingual full-thickness flaps were elevated and distal roots were removed. Implants were installed in the fresh extraction socket. Semi-submerged healing of the implant sites was allowed. In five dogs, the experimental procedure was first performed in the right side of the mandible and 2 months later in the left mandible. These five animals were sacrificed 1 month after the final implant installation. In two dogs, the premolar sites on both sides of the mandible were treated in one surgical session and biopsies were obtained immediately after implant placement. All biopsies were processed for ground sectioning and stained. RESULTS: The void that existed between the implant and the socket walls at surgery was filled at 4 weeks with woven bone that made contact with the SLA surface. In this interval, (i) the buccal and lingual bone walls underwent marked surface resorption and (ii) the height of the thin buccal hard tissue wall was reduced. The process of healing continued, and the buccal bone crest shifted further in the apical direction. After 12 weeks, the buccal crest was located>2 mm apical of the marginal border of the SLA surface. CONCLUSION: The bone-to-implant contact that was established during the early phase of socket healing following implant installation was in part lost when the buccal bone wall underwent continued resorption.     

Tomodensitometric and histologic evaluation of the combined use of a collagen membrane and a hydroxyapatite spacer for guided bone regeneration: a clinical report

In this report, the problems of insufficient bone and soft tissue after extraction of maxillary incisors were addressed concurrently prior to endosseous implant placement, by combining the use of a diphenylphosphorylazide-cross-linked Type I collagen membrane and a resorbable space-making biomaterial composed of 200-micron porous hydroxyapatite granules blended in Type I collagen and chondroitin-4-sulfate. Upon flap reflection 8 months postsurgery, the horizontal deficiencies were almost completely resolved, membranes completely resorbed and the defects filled with hard, bonelike tissue, with a few superficial hydroxyapatite granules. Histologic evaluation of the bone biopsies obtained at the implantation sites revealed dense, well-reconstructed alveolar bone with a few traces of hydroxyapatite granules that had been completely resorbed. Tomodensitometric evaluation indicated that bone regeneration ranged from 14% to 58%, with an average bone gain of 29.77%. Four nonsubmerged ITI titanium implants placed in the augmented bone have been in function for more than 5 years, with no clinical or radiographic signs of hard or soft tissue breakdown. Bacterial sampling at dental sites with periodontitis 1 month prior to periodontal therapy and at implant sites for up to 30 months demonstrated rapid colonization of implant surfaces by periodontopathogens without causing any detrimental effect to implant integration.