Light and transmission electron microscopy of the intact interfaces between non-submerged titanium-coated epoxy resin implants and bone or gingiva.

This experiment was aimed at studying the intact tissue/implant interface of non-submerged dental implants with a titanium surface. Epoxy-resin replicas were fabricated from 3.05 x 8 mm cylindrical titanium implants with a plasma-sprayed apical portion and a smooth coronal collar. The replicas were coated with a 90-120-nm-thick layer of pure titanium and autoclaved. The coated replicas were inserted as non-submerged endosseous implants in the edentulous premolar region of dog mandibles and allowed to heal for three months. Jaw sections containing the implants were processed for light and electron microscopic study of the intact tissue/implant interface with and without prior demineralization. Gingival connective tissue fibers were closely adapted to the titanium layer, in an orientation more or less parallel to the implant surface. There was no evidence of any fiber insertions into the surface irregularities of the smooth or rough titanium surface. Undemineralized bone was intimately adapted to the titanium surface without any intervening space. In demineralized sections, the collagen fibers of the bone matrix tended to be somewhat thinner and occasionally less densely packed in the vicinity of the implant surface. However, they extended all the way to the titanium surface, without any intervening fibril-free layer.     

A clinical, radiographic, and histological evaluation of permucosal dental implants of dense hydroxylapatite in dogs

A clinical, histological, and radiographic examination was performed on 77 permucosal dental implants, made of dense sintered hydroxylapatite: 34 solid cylinders and 43 hollow cylinders. The hollow cylinders were pre-compressed between two titanium caps. The implants were placed in partly edentulous mandibles of dogs, and were physiologically loaded. Healing was clinically and radiographically evaluated during a six-month to five-year period. At various times, implants with their surrounding tissues were removed and prepared for light and electron microscopy. All implants showed a good initial fit and were maintained in place without undercut or mechanical stabilization. After 18 months, 76% of the solid cylinders had fractured at the implant/bone junction due to fatigue. However, the submerged portions of the solid cylinders were preserved without clinical problems, and became entirely embedded in bone. The pre-stressed implants did not fracture, and 91% were functioning 24 months after placement. The average scores of pocket depths and gingival bleeding showed no significant differences between implants and surrounding natural teeth. Bone deposition occurred on the entire surface of the implant below the crest of the alveolar bone, and intimate bone contact was confirmed by electron microscopy. It was also observed that a layer of bone tissue was deposited on the implant surface in the permucosal area just above the alveolar bone level. Embedding of gingival fibers in this layer resulted in gingival attachment to the implant, comparable with that of natural teeth.     

Characterization, at the bone crystal level, of the titanium-coating/bone interfacial zone

Well integrated and clinically functional titanium dental implants retrieved in humans after 14 and 40 months of settlement were used for the characterization of the interfacial area between the plasma-sprayed coating and the surrounding mineralized bone. Electron microscopic studies were performed from undecalcified intact coating/bone interfaces. The concomitant presence of direct bone tissue apposition on the titanium coating, as well as the interposition of amorphous material along the same interfacial zones emphasizes the dynamic biologic aspect of the osseointegration process. A very striking finding of these ultrastructural and microanalytical investigations was the presence of tiny titanium grains ranging from 5 to 50 nm in diameter at the surface of bulky plasma-sprayed coating particles. High-resolution transmission electron microscopy revealed a continuity between the lattice planes of the coating material and those of the minute titanium grains; thus indicating a chemical binding. The thickness of the granular titanium layer interposed between coating particles and mineralized bone tissue ranged up to 600 nm. The observation of calcium-phosphate needle-like crystallites within the porous layer made of titanium grains indicates a bone ingrowth process, suggesting a bone-binding mechanism to the outer surface of the coated titanium implant.     

Implant‐tissue interfaces following treatment of peri‐implantitis using guided tissue regeneration. A light and electron microscopic study.

This study details the structural and ultrastructural features of the interfaces between titanium implants and their surrounding tissues. The material stemmed from an experiment in dogs in which guided tissue regeneration with Gore‐Text membranes was used to treat peri‐implant, ligature‐induced tissue breakdown around submerged and nonsubmerged com-mercially pure titanium implants. Specimens from the nonsubmerged group were evaluated under light microscopy and scanning and transmission electron microscopy. A healthy gingiva and a gingival sulcus were formed around the implant necks. A regenerated junctional epithelium provided the epithelial union between implant and gingiva. The supracrestal connective tissue was characterized by a 3‐dimensional network of collagen fibers, fibroblasts and blood vessels. Near the implant surface the collagen fibers ran parallel to the titanium surface or were orientated perpendicular to the implant. The connective tissue-implant interface was characterized by a fine fibrillar material interposed between the implant surface and the connective tissue. An unidentified material was also observed between the endings of functionally orientated collagen fibrils and the metallic surface. The apical portions of the implants were anchored in compact bone. At the bone‐implant interface, either mineralized bone matrix was intimately adapted to the titanium surface without any intervening space or a 0.5 μm wide unmineralized layer was interposed. These findings indicate that a perimucosal seal was formed around the implants consisting of a junctional epithelium‐implant union coronally and supported by the connective tissue-implant junction apically. The implants were integrated in connective tissue, but only tightly adapted to bone.     

Peripheral quantitative computer tomographic,histomorphometric, and removal torque analyses of two different non‐coated implants in a rabbit model

Objective: The objectives of this study were (1) to investigate the bone–tissue response to zirconia and titanium implants at the implant‐to‐bone interface and at the periosteal level and (2) to quantitatively measure the mineral density of the peri‐implant bone using peripheral quantitative computer tomography (pQCT). Material and methods: Ten 3.5 mm × 6.6 mm screw‐shaped threaded implants fabricated from titanium and zirconia were inserted into the mid‐tibial diaphysis of five male New Zealand white rabbits. Calcein green was administered at 4 weeks post‐implantation. The animals were sacrificed after 6 weeks and implants were retrieved and analyzed in terms of bone‐to‐implant contact (BIC), bone area (BA), mineralized surface (MS) percentage, inter‐thread calcein labels, removal torque (RT) values, as well as pQCT measurements. Findings: No statistically significant differences were detected between the zirconia and titanium implants in terms of BIC, RT, and pQCT. However, statistically significant higher BA and MS levels were found in the titanium group, while the higher amount of calcein labels occupying the threads were found in the zirconium group. Significant differences were also found in the quantity and the composition of bone at the bone–implant interfacial area vs. the region 1.5 mm away from the bone–implant interface, irrespective of the implant type. Conclusion: Zirconia implants demonstrated a lower bone remodeling activity in the periosteal region. The bone at the bone–implant interface shows a significantly lower cortical bone density, a higher trabecular density, and trabecular mineral content. Finally, zirconia and titanium implants showed similar bone–implant responses in terms of BIC and RT. To cite this article:
Shin D, Blanchard SB, Ito M, Chu T‐MG. Peripheral quantitative computer tomographic, histomorphometric, and removal torque analyses of two different non‐coated implants in a rabbit model.
Clin. Oral Impl. Res. 22 , 2011; 242–250.
doi: 10.1111/j.1600‐0501.2010.01980.x     

Effect of hydroxyapatite and titania nanostructures on early in vivo bone response

Purpose: Hydroxyapatite (HA) or titania nanostructures were applied on smooth titanium implant cylinders. The aim was to investigate whether nano‐HA may result in enhanced osseointegration compared to nano‐titania structures. Materials and Methods: Surface topography evaluation included detailed characterization of nano‐size structures present at the implant surface combined with surface roughness parameters at the micro‐ and nanometer level of resolution. Microstructures were removed from the surface to ensure that bone response observed was dependent only on the nanotopography and/or chemistry of the surface. Early in vivo histological analyses of the bone response (4 weeks) were investigated in a rabbit model. Results: In the present study, nano‐titania‐coated implants showed an increased coverage area and feature density, forming a homogenous layer compared to nano‐HA implants. Bone contact values of the nano‐titania implants showed a tendency to have a higher percentage as compared to the nano‐HA implants (p = .1). Conclusion: Thus, no evidence of enhanced bone formation to nano‐HA‐modified implants was observed compared to nano‐titania‐modified implants. The presence of specific nanostructures dependent on the surface modification exhibiting different size and distribution did modulate in vivo bone response.     

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     

A mechanical evaluation of implants placed with different surgical techniques into the trabecular bone of goats

The aim of the study was to assess the effects of surgical technique and implant surface roughness on implant fixation. A total of 48 screw implants with machined or etched surface topographies were placed into the femoral condyles of goats. The implant sites were prepared by a conventional technique, by undersized preparation, or by the osteotome technique. Bone tissue responses were evaluated after 12 weeks of healing by removal torque testing and histologic analysis using scanning electron microscope. The cumulative removal torque value of the etched implants placed with the undersized technique (98 +/- 29 Ncm) was higher (50 +/- 35 Ncm) to a level of statistical significance than machined surface implants placed by the osteotome technique. Scanning electron microscope evaluation indicated that all implants showed interfacial bone contact. The torque test resulted in fracture at the bone-implant interface for all experimental conditions. Installation of etched implants using an undersized preparation of the implant bed resulted in superior bonding strength with the surrounding bone at 12 weeks after surgery. Evidently, the undersized preparation technique improved the early fixation of oral implants in this study.     

Postmortem histologic evaluation of mandibular titanium and maxillary hydroxyapatite-coated implants from 1 patient.

Postmortem examination of human specimens is an extremely important aspect of evaluating the relative compatibility and long-term success of endosseous implant surfaces. The bone-implant interface of 5 commercially pure titanium screw-type mandibular implants after 85 months of service and 2 hydroxyapatite- (HA) coated maxillary implants after 38 months of service were examined. All implants were stable at the time of the patient's death. The mandibular implants had an average of 65% contact with bone and the maxillary implants had an average of 47% contact. The HA coating had separated from the maxillary implants in some areas and was free within surrounding connective tissue or surrounded by invaginating sulcular epithelium. The arrangement and pattern of bone contact appeared different between HA-coated and titanium implant surfaces.     

Structure of the bone‐titanium interface in retrieved clinical oral implants

7 clinically stable, "osseointegrated", titanium implants, inserted in human jaws for l–16 years, were retrieved for morphological analysis of the bone‐titanium interface, using 3 different preparation techniques. The bone‐titanium interface varied as judged from light microscopy of ground sections. The threads of the implants were well filled 79–95% with dense lamellar bone as quantified with morphometry. A large fraction of the implant surface (56–85%) appeared to be in direct contact with the mineralized bone. In general, the non‐boric areas consisted of pockets with osteocytes, bone marrow tissue and/or vessels. Sections were prepared for light microscopy and transmission electron microscopy using a fracture technique. where the implant was separated from the embedded tissue before sectioning, and an electropolishing technique, where the bulk part of the implant was electrochemically removed. In areas judged as direct mineralized bone‐titanium contact in the light microscope. the interfacial structure varied at the ultrastructural level. In areas along the interface, unmineralized tissue was present either as a narrow 0.5–l μm wide zone containing collagen fibril or as deeper pockets containing osteocytes or vessels. In areas with mineralized bone contact. an amorphous granular layer (100–400 nm wide) with no mineral was observed in the innermost interface bordering the mineralized bone, with an electron‐dense lamina limitans‐like line (approximately 50 nm thick). It is concluded that the bone‐titanium interface of the 7 clinically retrieved titanium oral implants examined in the present study bone was heterogenous. In areas of a direct mineralized bone‐titanium contact at the ultrastructural level. mineralized bone reached close to the implant surface, but was separated by an amorphous layer. 1 being 100–400 nm thick.     

Effect of hydroxyapatite on bone formation around exposed heads of titanium implants in rabbits

Dense hydroxyapatite (HA)--collagen was placed around the protruding heads of titanium and titanium alloy implants in the femurs of 38 rabbits. After 6 months, bone apposition was evaluated by gross examination and scanning electron microscopy. Although bone was observed in direct contact with the implant heads, the extremities of the implant heads were surrounded by connective tissue. Compared with the control animals, packing dense HA-collagen around the implant heads did not increase the area of osteogenesis. When the implants penetrated into bone through previously placed HA-collagen blocks, there was a decrease in the amount of bone attached to the body of the implants compared with the controls. The results of this study suggest that the use of dense HA does not increase the amount of bone tissue formed around titanium implants.     

Bone reaction adjacent to microplasma-sprayed calcium phosphate-coated oral implants subjected to an occlusal load, an experimental study in the dog

Background: A new microplasma spraying equipment (MSE) to deposit calcium phosphate (CaP) ceramic coatings onto titanium substrates has been developed. With this system, it is possible to spray fine particles and to apply textured hydroxylapatite coatings onto titanium surfaces. Moreover, due to the low heat power of the microplasma jet, overheating of the powder particles as well as excessive local overheating of the substrate are diminished. Furthermore, because of the small laminar plasma jet, it is possible to achieve high spray efficiency in the case of spraying for dental implants. Also, the low level of noise (25–50 dB) and hardly any dust makes it possible to operate MSE under conditions of normal workrooms. Objective: The aim was to investigate, in a mandibular dog model, the effect of functional load on soft‐tissue adaptation as well as crestal bone‐level changes around titanium implants provided with newly developed microplasma‐sprayed CaP coatings. Material and methods: For histomorphometrical evaluation, 56 screw‐type titanium implants were inserted into the mandibles of seven adult Beagle dogs. The implants were either acid etched without an additional coating, coated with a conventionally plasma‐sprayed CaP ceramic (PS), coated with a microplasma‐sprayed CaP ceramic (MPS) or with a microplasma‐sprayed coating at only the apical part (aMPS). To assess the effect of occlusal loading, a split‐mouth design was used. Six weeks after implantation, the implants in one half of the mandible of each dog were functionally loaded whereas the contra lateral implants served as control. One year after loading, the animals were sacrificed. Soft‐tissue dimension as well as marginal bone level were histologically assessed. Results: Histometric analysis of undecalcified histologic sections included the evaluation of the sulcus depth, the dimension of the junctional epithelium and the connective tissue as well as the first bone‐to‐implant contact. For MPS‐surfaced implants, functional loading was associated with – compared with the non‐loaded state – unchanged soft‐tissue dimension. Furthermore, the soft‐tissue dimension did not differ from the dimensions around non‐coated, PS and aMPS implants. Moreover, the first bone‐to‐implant contact was not significantly altered by functional loading and comparable non‐coated, PS and aMPS implants. Conclusion: Within the limits of the experiment, we conclude that, in comparison, functional loading does not affect the marginal soft‐tissue response to MPS CaP‐coated implants. However, in comparison, functional loading might affect marginal bone response to MPS CaP‐coated implants. To cite this article:
Junker R, Manders PJD, Wolke J, Borisov Y, Braceras I, Jansen JA. Bone reaction adjacent to microplasma‐sprayed calcium phosphate‐coated oral implants subjected to occlusal load, an experimental study in the dog. Clin. Oral Impl. Res. 22 , 2011; 135–142.
doi: 10.1111/j.1600‐0501.2010.02025.x     

Profilometric and standard error of the mean analysis of rough implant surfaces treated with different instrumentations

PURPOSE: This study evaluated, in vitro, the effects of different instrumentations used in the treatment of peri-implantitis on implant surfaces coated with hydroxyapatite or titanium plasma spray (TPS). MATERIALS AND METHODS: There were 14 cylindrical rough implants used, including 7 hydroxyapatite and 7 TPS coated. Split in 2 parts for a total of 24 experimental surfaces, implants were treated with a stainless-steel curette, plastic curette, ultrasonic scaler tip, and air-powder-water spray. There was 1 hydroxyapatite and 1 TPS implant used as controls. Profilometry and scanning electron microscopy were used to examine instrumented surfaces for variations in surface topography. RESULTS: All experimental procedures determined changes on tested rough implant surfaces. Such alterations were related to the implant coating material, and the procedure consisting in coating removal and/or leveling of surface roughness. CONCLUSION: Although a plastic curette and air-powder-water spray induced less implant surface alterations, these instrumentations left deposits on the surface that may affect, in vivo, the tissue healing process.     

Tissue response to titanium implantation in the rat maxilla, with special reference to the effects of surface conditions on bone formation

Tissue responses to titanium implantation with two different surface conditions in our established implantation model in rat maxillae were investigated by light and transmission electron microscopy and by histochemistry for tartrate-resistant acid phosphatase (TRAPase) activity. Here we used two types of implants with different surface qualities: titanium implants sandblasted with Al2O3 (SA-group) and implants coated with hydroxyapatite (HA-group). In both groups, bone formation had begun by 5 days postimplantation when the inflammatory reaction had almost disappeared in the prepared bone cavity. In the SA-group, however, the bone formation process in the bone cavity was almost identical to that shown in our previous report using smooth surfaced implants (Futami et al. 2000): new bone formation, which occurred from the pre-existing bone toward the implant, was preceded by active bone resorption in the lateral area with a narrow gap, but not so in the base area with a wide gap. In the HA-group, direct bone formation from the implant toward the pre-existing bone was recognizable in both lateral and base areas. Many TRAPase-reactive cells were found near the implant surface. On the pre-existing bone, new bone formation occurred with bone resorption by typical osteoclasts. Osseointegration around the implants was achieved by postoperative day 28 in both SA- and HA-groups except for the lateral area, where the implant had been installed close to the cavity margin. These findings indicate that ossification around the titanium implants progresses in different patterns, probably dependent on surface properties and quality.     

Load-related bone modelling at the interface of orthodontic micro-implants

Abstract: The purpose of this study was to determine the interface reaction of two different titanium micro‐implant systems activated with different load regimens. A total of 200 micro‐implants (100 Abso Anchor^® and 100 Dual Top^®) were placed in the mandible of eight Göttinger minipigs. Two implants each were immediately loaded in the opposite direction by various forces (100, 300 or 500 cN) through tension coils. Three different distances between the neck of the implant and the bone rim (1, 2, 3 mm) were used. The loads provided by superelastic tension coils (which are known to develop a virtually constant force) led to a range of tip moments 0–900 cN mm at the neck of implants. Non‐loaded implants were used as a reference. Bone tissue responses were evaluated by histology, histomorphometry and scanning electron microscopy after 22 and 70 days of loading. Implant loosening was present in the groups where the load reached 900 cN mm. No movement of implants through the bone was found in the experimental groups, for any of the applied loads. A direct bone‐to‐implant contact to various extents was observed at differently loaded implants. Ultrastructural analysis confirmed the clinical and histological finding that implants (except when loaded at 900 cN mm) were well osseointegrated after 22 days. An increase in the bone‐to‐implant contact ratio was observed during the experimental period in the coronal part of the implants in most experimental groups. The difference reached a level of statistical significance at 500 cN mm (Abso Anchor^®) and 600 cN mm (Dual Top^®). We conclude that micro‐implants can not only be loaded immediately without impairment of implant stability but many enhance bone formation at the interface when the load‐related biomechanics do not exceed an upper limit of tip moment at the bone rim.     

Histomorphometric analysis of the osseointegration of four different implant surfaces in the femoral epiphyses of rabbits

Objectives: The surface properties of titanium dental implants are key parameters for rapid and intimate bone–implant contact. The osseointegration of four implant surfaces was studied in the femoral epiphyses of rabbits. Material and methods: Titanium implants were either grit‐blasted with alumina or biphasic calcium phosphate (BCP) ceramic particles, coated with a thin octacalcium phosphate (OCP) layer, or prepared by large‐grit sand blasting and acid‐etched (SLA). After 2 and 8 weeks of implantation, the bone‐implant contact and bone growth inside the chambers were compared. Scanning electron microscopy (SEM) and profilometry showed distinct microtopographies. Results: The alumina‐Ti, BCP‐Ti and OCP‐Ti groups had similar average surface roughness in the 1–2 μm range whereas the SLA surface was significantly higher with a roughness averaging 4.5 μm. Concerning the osseointegration, the study demonstrated a significantly greater bone‐to‐implant contact for both the SLA and OCP‐Ti surfaces as compared with the grit‐blasted surfaces, alumina‐ and BCP‐Ti at both 2 and 8 weeks of healing. Conclusion: In this animal model, a biomimetic calcium phosphate coating gave similar osseointegration to the SLA surface. This biomimetic coating method may enhance the apposition of bone onto titanium dental implants.     

Osseointegration of one‐piece zirconia implants compared with a titanium implant of identical design: a histomorphometric study in the dog

Objective: The aim of this study was to evaluate osseointegration of one‐piece zirconia vs. titanium implants depending on their insertion depth by histomorphometry. Material and methods: Four one‐piece implants of identical geometry were inserted on each side of six mongrel dogs: (1) an uncoated zirconia implant, (2) a zirconia implant coated with a calcium‐liberating titanium oxide coating, (3) a titanium implant and (4) an experimental implant made of a synthetic material (polyetheretherketone). In a split‐mouth manner they were inserted in submerged and non‐submerged gingival healing modes. After 4 months, dissected blocks were stained with toluidine blue in order to histologically assess the bone‐to‐implant contact (BIC) rates and the bone levels (BL) of the implants. Results: All 48 implants were osseointegrated clinically and histologically. Histomorphometrically, BL in the crestal implant part did not differ significantly with regard to material type or healing modality. The submerged coated zirconia implants tended to offer the most stable crestal BL. The histometric results reflected the different healing modes by establishing different BL. The median BIC of the apical implant part of the zirconia and titanium group amounted to 59.2% for uncoated zirconia, 58.3% for coated zirconia, 26.8% for the synthetic material and 41.2% for titanium implants. Conclusions: Within the limits of this animal study, it is concluded that zirconia implants are capable of establishing close BIC rates similar to what is known from the osseointegration behaviour of titanium implants with the same surface modification and roughness. To cite this article:
Koch FP, Weng D, Krämer S, Biesterfeld S, Jahn‐Eimermacher A, Wagner W. Osseointegration of one‐piece zirconia implants compared with a titanium implant of identical design: a histomorphometric study in the dog.
Clin. Oral Impl. Res. 21 , 2010; 350–356.
doi: 10.1111/j.1600‐0501.2009.01832.x     

Histologic evaluation of clinically successful osseointegrated implants retrieved from irradiated bone: a report of 2 patients.

The present study described the histologic findings of 2 implants and surrounding tissues retrieved from human irradiated bone. For the treatment of a malignant tumor, 50 Gy of irradiation after implant placement and 60 Gy of irradiation before implant placement were provided for patients 1 and 2, respectively. In patient 1, the implant and surrounding tissues were removed from the frontal bone 24 months after implant placement because of the patient's death from a tumor recurrence. In patient 2, the implant and surrounding tissue were removed from a maxillectomy site 26 months after implant placement because of tumor recurrence. In each patient, new bone formation surrounding the implants was observed. The ratio of direct bone-implant contact along the threaded implant surface was 61.3% in patient 1 and 69.0% in patient 2. The ratio of the area occupied by mineralized bone in each thread was 75.8% in patient 1 and 81.2% in patient 2. These results indicate the potential of irradiated bone to achieve osseointegration of titanium implants.     

Characterization of the surface properties of commercially available dental implants using scanning electron microscopy, focused ion beam, and high-resolution transmission electron microscopy

Background: Since osseointegration of the respective implant is claimed by all manufacturing companies, it is obvious that not just one specific surface profile including the chemistry controls bone apposition. Purpose: The purpose was to identify and separate out a particular set of surface features of the implant surfaces that can contribute as factors in the osseointegration process. Material and Methods: The surface properties of several commercially available dental implants were extensively studied using profilometry, scanning electron microscopy, and transmission electron microscopy. Ultrathin sections prepared with focused ion beam microscopy (FIB) provided microstructural and chemical data which have not previously been communicated. The implants were the Nobel Biocare TiUnite® (Nobel Biocare AB, Göteborg, Sweden), Nobel Biocare Steri‐Oss HA‐coated (Nobel Biocare AB, Yorba Linda, CA, USA), Astra‐Tech OsseoSpeed? (Astra Tech AB, Mölndal, Sweden), Straumann SLA® (Straumann AG, Waldenburg, Switzerland), and the Brånemark Integration Original Fixture implant (Brånemark Integration, Göteborg, Sweden). Results: It was found that their surface properties had differences. The surfaces were covered with crystalline TiO₂ (both anatase and rutile), amorphous titanium oxide, phosphorus doped amorphous titanium oxide, fluorine, titanium hydride, and hydroxyapatite, respectively. Conclusion: This indicates that the provision of osseointegration is not exclusively linked to a particular set of surface features if the implant surface character is a major factor in that process. The studied methodology provides an effective tool to also analyze the interface between implant and surrounding bone. This would be a natural next step in understanding the ultrastructure of the interface between bone and implants.     

Bone formation at recombinant human bone morphogenetic protein-2-coated titanium implants in the posterior maxilla (Type IV bone) in non-human primates

Background: Studies using ectopic rodent and orthotopic canine models (Type II bone) have shown that titanium porous oxide (TPO) surface implants adsorbed with recombinant human bone morphogenetic protein‐2 (rhBMP‐2) induce local bone formation including osseointegration. The objective of this study was to evaluate local bone formation and osseointegration at such implants placed into Type IV bone. Material and Methods: rhBMP‐2‐coated implants were installed into the edentulated posterior maxilla in eight young adult Cynomolgus monkeys: four animals each received three TPO implants adsorbed with rhBMP‐2 (2.0 mg/ml) and four animals each received three TPO implants adsorbed with rhBMP‐2 (0.2 mg/ml). Contra‐lateral jaw quadrants received three TPO implants without rhBMP‐2 (control). Treatments were alternated between left and right jaw quadrants. Mucosal flaps were advanced and sutured to submerge the implants. The animals received fluorescent bone markers at weeks 2, 3, 4, and at week 16 when they were euthanized for histologic analysis. Results: Clinical healing was uneventful. Extensive local bone formation was observed in animals receiving implants adsorbed with rhBMP‐2 (2.0 mg/ml). The newly formed bone exhibited a specific pinpoint bone–implant contact pattern regardless of rhBMP‐2 concentration resulting in significant osseointegration; rhBMP‐2 (2.0 mg/ml): 43% and rhBMP‐2 (0.2 mg/ml): 37%. Control implants exhibited a thin layer of bone covering a relatively larger portion of the implant threads. Thus, TPO control implants bone exhibited significantly greater bone–implant contact (～75%; p<0.05). There were no statistically significant differences between rhBMP‐2‐coated and control implants relative to any other parameter including peri‐implant and intra‐thread bone density. Conclusion: rhBMP‐2‐coated TPO implants enhanced/accelerated local bone formation in Type IV bone in a dose‐dependent fashion in non‐human primates resulting in significant osseointegration. rhBMP‐2‐induced de novo bone formation did not reach the level of osseointegration observed in native resident bone within the 16‐week interval.