Interleukin-1beta regulation of adhesion molecules on human gingival and periodontal ligament fibroblasts.

BACKGROUND: Adhesion molecules have been implicated in the pathogenesis of rheumatoid arthritis and may also play a role in the pathogenesis of periodontal disease by promoting the recruitment and retention of leukocytes in gingival tissue. METHODS: The aim of the present study was to evaluate the capacity of interleukin-1beta (IL-1beta) to regulate adhesion molecule expression on clinically healthy human gingival (HGF) and periodontal ligament (PDL) fibroblasts. The HGF (n = 6) and PDL (n = 3) fibroblasts were treated with 1.0 ng/ml of IL-1beta for 24 hours and then incubated with primary intercellular adhesion molecule-1 (ICAM-1) and vascular cellular adhesion molecule-1 (VCAM-1) antibodies followed by FITC-conjugated secondary antibodies. The expression of ICAM-1 and VCAM-1 was measured by immunofluorescence flow cytometry. RESULTS: The levels of ICAM-1 expression in IL-1beta treated HGF and PDL fibroblasts were statistically significant (P < or = 0.05) compared to normal untreated controls using log-transformed data and 3-way analysis of variance. Both cells expressed VCAM-1 after IL-1beta treatment, but the levels were not statistically different from controls. CONCLUSIONS: This study demonstrated that IL-1beta upregulated ICAM-1 expression in both HGF and PDL fibroblasts. Even though the level of VCAM-1 was not statistically different from both HGF and PDL fibroblasts treated with IL-1beta compared to controls, both cells do express the VCAM-1 molecules. These results suggest that ICAM-1 and VCAM-1 might be involved in the pathogenesis of periodontal disease.

Effect of lipopolysaccharide contamination on the attachment of osteoblast-like cells to titanium and titanium alloy in vitro.

Failing implants with loss of alveolar bone are associated with gram-negative bacteria that carry lipopolysaccharide (LPS) in the bacterial cell wall. Bony regeneration around these implants is still an unpredictable procedure due to the many clinical factors involved. One important factor is the presence of contaminants such as LPS on the implant surface. The effect of implant-associated LPS on the attachment of bone cells to the implant surface is unknown. This project investigated the effect of LPS on the attachment of osteoblast-like cells (MC3T3-E1) to titanium and titanium alloy surfaces in vitro. We hypothesized that LPS would inhibit bone cell attachment either through loss of cellular attachment sites or alteration of cellular function. Three experimental approaches were used. First, alloy surfaces were exposed to LPS (100 microgram/mL) before the cells were allowed to attach. In the second approach, the cells were exposed to the LPS before they were allowed to attach. Last, the cells were allowed to attach before exposure to LPS. Cellular attachment to implant materials was measured by using a histochemical stain (MTT). The results indicated that LPS presence did not significantly (P > .05) alter osteoblast attachment to titanium or titanium alloy surfaces whether the exposure occurred before or after cellular adherence. It was concluded that LPS did not directly effect the attachment of the MC3T3-E1 osteoblasts to these implant surfaces in vitro. Further research is needed to define the clinical liabilities of LPS during implant placement and maintenance.

Histologic evaluation of the periodontium of abutment teeth in combination implant/tooth fixed partial denture.

The histologic response of the periodontal tissues of teeth rigidly joined to implants with a fixed partial denture was evaluated using light microscopy. The fourth premolar of a dog was connected to implants placed in the first and second premolar position with a fixed partial denture. The restored teeth were under function for periods of 6, 12, 18, and 24 months, with unrestored fourth premolars as controls. The histology of the periodontal ligament on the fourth premolar was found to be similar in the control and the restored teeth. The periodontal tissues contained a minimal amount of inflammatory cell infiltrate. The crestal bone was cortical in nature, showing no periodontal breakdown. The orientation of the periodontal fibers was easily determined, indicating that minimal remodeling had taken place. The number and morphology of the blood vessels were also similar in the control and the treated teeth. The lack of inflammation and stability of the periodontal tissue suggested that the use of combination implant-to-natural-teeth restorations with rigid joints in this animal model does not result in deleterious effects on the periodontal tissues and that the forces placed on the tissues are within the remodeling capabilities of the teeth.

A relationship between proteinase activity and clinical parameters in the treatment of periodontal disease.

The objective of this research was to determine the effectiveness of a biochemical assay which measures proteolytic enzyme activity in gingival crevicular fluid (GCF) and to relate this enzyme activity to clinical parameters traditionally utilized for periodontitis detection. A clinical trial was conducted on 8 periodontitis subjects with > or =4 sites exhibiting a loss of attachment of > or =5 mm and probing depths of > or =5 mm with bleeding on probing. On each subject, a plaque index was performed, followed by GCF sampling at those sites which exhibited a loss of attachment and probing depths. GCF was analyzed for activity against benzoyl-L-arginine-p-nitroanilide in the presence (BAPNA w/gly-gly) and the absence (BAPNA w/o gly-gly) of glycyl-glycine and against MeOSuc-Ala-Ala-Pro-Val-pNA and Suc-Ala-Ala-Pro-Phe-pNA for neutrophil serine proteinases activity (elastase and cathepsin G, respectively). Subsequently, a gingival index was performed, attachment levels and probing depths were recorded using a constant force probe with bleeding on probing being noted. A split-mouth design was employed and half mouths were randomly assigned to the following treatment groups: group A, half of the mouth received scaling/root planing and polishing: group B, half of the mouth received no treatment (control). Subjects were treated, then instructed on toothbrushing and interdental cleaning. After 4 weeks, subjects returned to receive a plaque index; GCF sampling, gingival index, attachment levels, probing depths and bleeding on probing as described above. Using a paired Student t-test, the findings suggest that BAPNA w/gly-gly was significantly less in treatment sites than in non-treated control sites (p=0.05). No such correlation was found for other activities, including neutrophil serine proteinases which were shown to occur in GCF in free, proteolytically active forms. In addition, significant treatment effects were detected for probing depths (p= 0.03) which reduced by 1.3 mm and attachment levels (p=0.02) which gained 0.7 mm. The reduction of P. gingivalis from treated periodontitis sites as detected by a significant decrease in BAPNA w/ gly-gly may prove to be a valuable marker for periodontal disease activity.

HLA-DR alleles are associated with IDDM, but not with impaired neutrophil chemotaxis in IDDM.

Insulin-dependent diabetes mellitus (IDDM) is a risk factor for periodontitis. Depressed neutrophil chemotaxis has been demonstrated in IDDM and in early-onset periodontitis (EOP). HLA-DR antigens are associated with both IDDM and periodontitis. This investigation sought to determine an association of HLA-DR3, -DR4, and -DR53 with impaired neutrophil chemotaxis in an IDDM sample. The neutrophil chemotaxis index of 41 diabetics and 27 controls was determined by a modified Boyden chamber method, and certain class II HLA genotypes were determined by polymerase chain-reaction amplification of genomic DNA by means of sequence-specific primers (PCR-SSP). The mean chemotaxis index of the diabetics was significantly less than that of the controls (p < or = 0.02). HLA-DR3 (p < or = 0.002), -DR4 (p < 0.003), and -DR53 (p < or = 0.001) were associated with IDDM. Neutrophil chemotaxis and glucose metabolism were not significantly correlated. None of the HLA-DR alleles was associated with impaired neutrophil chemotaxis. Therefore, the neutrophil chemotaxis defect of IDDM appears to be independent of these HLA-DR-associated genes.

Ultrastructural analyses of the attachment (bonding) zone between bone and implanted biomaterials.

This report presents transmission electron and high voltage transmission electron microscopic observations of bone and associated remodeling tissues directly interfacing with endosteal dental implants. Undecalcified interfacial tissues were serially sectioned from mandibular samples encasing 60 implants placed into 30 dogs. Two-dimensional ultrastructural analyses and three-dimensional stereology showed that osteogenesis adjacent to dental implants is a dynamic interaction of osseous cells and a collagenous fiber matrix. This study showed that the interfacial bone consists of a mineralized collagen fiber matrix associated with an inorganic (hydroxylapatite) matrix. This study suggested that an unmineralized collagen fiber matrix initially is laid down directly at the implant surface, and that this matrix then is mineralized. Osteoblasts interacted with this matrix, eventually becoming encased within developing lacunae during the remodeling process. This process formed the cellular (osteocyte) aspects of the developed bone. Osteocyte processes extended through canaliculi directly to the implant surface. Apparently, these processes also were entrapped within canaliculi during the mineralization events. At times, these processes paralleled the implant surface. The bone-implant interfacial zone was primarily fibrillar (both mineralized and unmineralized) in morphology, with an electron-dense, ruthenium positive deposition. This electron-dense material was approximately 20 to 50 nanometers in thickness, and only this thin layer separated the remodeled mineralized bone from the implant.

Composite morphology of the bone and associated support-tissue interfaces to osseointegrated dental implants: TEM and HVEM analyses.

Correlated transmission electron and high-voltage electron microscopic analyses examined the undecalcified bone and associated support tissues of 60 endosseous titanium blade and titanium and ceramic root-form implants in dogs. The implants supported fixed partial dentures for up to 2 years. Data obtained from this investigation suggest that a range of tissues, both mineralized and unmineralized, support osseointegrated dental implants. This study examined the tissues apposing not just isolated aspects of the implant surface, but the entire length of the implant, and found that mineralized and unmineralized tissues existed concurrently. Much of the implant surface was apposed by mandibular bone, and both root-form and blade implants osseointegrated. The densely mineralized collagen fibril matrix was often separated from the implant by only a 20-nm to 50-nm electron-dense, ruthenium-positive deposit. High-voltage electron microscope stereology demonstrated that cellular processes extended directly to the implant from underlying osteocytes. In the same implants, areas containing an unmineralized collagen matrix interposed between the bone and implant surface were observed. In this region osteoblasts interacted with this matrix, and Howship's lacunae, containing vascular elements and osteoclasts, were also observed. The remodeling activities appear to be a homeostasis of catabolic activity (osteoclasts) and metabolic activity (osteoblasts). The apex of the implant was often apposed by a fibrofatty stroma. The support tissue response appears to be the result of the interrelations of osteoblasts, osteocytes, and osteoclasts in association with vascular elements. Therefore, the support tissue response to osseointegrated implants is a dynamic activity that involves the healthy interaction of these cells and tissues along the entire length of the implant.

Multi-center comparative evaluation of subgingivally delivered sanguinarine and doxycycline in the treatment of periodontitis. I. Study design, procedures, and management.

The design and conduct of a 9-month multi-center clinical trial to evaluate the safety and efficacy of subgingivally delivered 5% sanguinarium chloride (SC) and 10% doxycycline hyclate (DH) from a biodegradable drug delivery system in the treatment of adult periodontitis is described. The 3-group randomized study of 180 adults with moderate to severe periodontitis was a modified double-blind parallel design. One group received DH, one group received SC, and the other group received the vehicle control (VC). Patients selected had two quadrants with a minimum of four periodontal pockets > or = 5 mm in depth with two sites > or = 7 mm. All qualifying sites exhibited bleeding on gentle probing. Qualifying sites were treated at baseline and again at 4 months. Clinical response was assessed by measuring attachment level, probing depth, and bleeding on probing at monthly examinations at qualifying sites and the entire dentition. The plaque index was measured monthly to verify oral hygiene status. The parallel design afforded the opportunity to distinguish between treatment effectiveness of SC, DH, and VC independent of possible crossover effects. Also the effectiveness of oral hygiene in untreated sites of the mouth could be evaluated. Finally, treatment effects in moderate (5 to 6 mm) and deep (> or = 7 mm) pockets in both treated and untreated sites could be compared. The design was capable of simulating a periodontal practice maintenance program and assessing the response according to maintenance and treatment history. Study management procedures that emphasized center examiner and therapist training and adherence to protocol and procedures to reduce variability are described.

Multi-center comparative evaluation of subgingivally delivered sanguinarine and doxycycline in the treatment of periodontitis. II. Clinical results.

The clinical safety and effectiveness of a subgingivally delivered biodegradable drug delivery system containing either 10% doxycycline hyclate (DH), 5% sanguinarium chloride (SC) or no agent (VC) was evaluated in a 9-month multi-center trial. The study was a randomized parallel design with 180 patients who demonstrated moderate to severe periodontitis. All patients had at least two quadrants with a minimum of four qualifying pockets > or = 5 mm that bled on probing. Two of the qualifying pockets were required to be > or = 7 mm. At baseline and at 4 months all qualified sites were treated with the test article administered via syringe. Probing depth reduction (PDR), attachment level gain (ALG), bleeding on probing reduction (BOP), and plaque index were determined monthly. Analysis of efficacy data from the 173 efficacy-evaluable patients indicated that all treatments gave significant positive clinical changes from baseline at all subsequent timepoints. DH was superior to SC and VC in PDR at all timepoints (P < or = 0.01 to 0.001) with a maximum reduction of 2.0 mm at 5 months. For ALG, DH was superior to VC at months 2, 3, 4, 5, 6, 8, and 9 (P < or = 0.04 to 0.002) and superior to SC at months 5, 6, 7, 8, and 9 (P < or = 0.01 to 0.001) with a maximum ALG of 1.2 mm at 6 months. For BOP reduction, DH was superior to VC at all time points (P < or = 0.05) and to SC at months 3, 5, 6, 8, and 9 (P < or = 0.03). For DH, the maximum ALG in deep (> or = 7 mm) pockets was 1.7 mm and PDR 2.9 mm compared to 0.8 mm and 1.6 mm, respectively for moderate (5 to 6 mm) pockets. Test articles were applied without anesthesia and no serious adverse events occurred in the trial. The results of this study indicate that 10% doxycycline hyclate delivered in a biodegradable delivery system is an effective means of reducing the clinical signs of adult periodontitis and exhibits a benign safety profile.

2 multi-center trials assessing the clinical efficacy of 5% sanguinarine in a biodegradable drug delivery system.

A biodegradable drug delivery system containing 5% sanguinarium (Sa) was compared to vehicle control (VC), scaling and root planing (SRP), and supragingival plaque control (SPC) in the treatment of adult periodontitis in 2 well-controlled clinical trials. Studies were 4-quadrant (split mouth) designs at 2 centers each, having 94 (Study A) and 107 (Study B) patients. All patients had at least 3 pockets between 5 and 9 mm that bled on probing, in each quadrant. Probing pocket depth (PD), clinical attachment level (AL), bleeding on probing (BOP), and plaque index were recorded at baseline, 14, 30, 60, and 90 days. All treatments gave statistically significant reductions from baseline for PD and BOP, and significant gains for AL. For PD reduction, SRP was superior to all test groups at all time points in both studies (p < 0.001). Sa was superior to VC in Study A at 14 and 30 days and to SPC at all time points. For AL gain at 90 days, in both studies, SRP gave gains of 0.42 and 0.78 mm respectively with superiority seen over the SPC group at 90 days (p < 0.001) in study A only, For BOP reduction, in Study A SRP was superior to Sa, VC, and SPC at 60 and 90 days (p < 0.005) and in Study B superiority to Sa and VC was at 90 days and to SPC at 60 days (p < 0.05). Sa was superior to VC for pocket depth in deep pockets only. Sa failed to demonstrate superiority over VC on a consistent basis. Analysis of residual Sa indicates that Sa potency was insufficient to show an advantage beyond clinical effects inherent in treatments with VC and SPC.

A comparative investigation in dogs: 2-year morphometric results of the dental implant--bone interface.

One hundred twenty titanium and ceramic root-form and titanium blade implants were placed into 30 dog mandibles. Twenty-four implants in six control dogs (in situ for 5 months) did not receive prostheses. Ninety-six implants in 24 dogs supported prostheses for 6, 12, 18, or 24 months. Computerized morphometry data presented the percent of the implant surface apposed directly by bone. A three-way factorial analysis of variance was used to assess significance. Individual implant means ranged from 0% (mobile implant) to 71% bone adaptation. From these data, two-stage titanium root-form implants were shown to be apposed by more bone than the other five systems, and overall, titanium implant systems were apposed by more bone than ceramic systems. Between 41% and 50% of the surface of integrated ceramic implants were apposed by bone, whereas between 50% and 65% of the surfaces of titanium implants were apposed by bone. Also, two-stage surgery for blade implants appears important for implant success. Furthermore, the use of Nomarski differential illumination appears to be useful for examining the quality of interfacial bone to correlate with the amount of bone quantified by morphometric protocols.

Human periodontal ligament and gingival fibroblast response to TGF-beta 1 stimulation.

The purpose of this study was to measure the time-sequence response of RNA and protein synthesis to transforming growth factor-beta 1 (TGF-beta 1) by human periodontal ligament (HPDLF) and gingival (HGF) fibroblasts in culture. HPDLF and HGF were cultured from explants of healthy gingival tissue and freshly extracted teeth. Cultures of 8 x 10(4) cells/ml were exposed to medium containing 3H-uridine and 35S-methionine with TGF-beta 1 at concentrations from 10(-9) M to 10(-21) M, or control medium, for up to 60 hours in order to assess RNA and protein synthesis. Protein concentrations of comparable cultures were also assayed colorimetrically. Results were reported as specific activity (CPM/microgram protein). The results indicate that 10(-9) M TGF-beta 1 treated cultures showed a significant increase in RNA synthesis by HPDLF and HGF over time, as compared to the control cultures. HPDLF showed a significant increase in protein synthesis over time while that by HGF was not significant as compared to the control cultures. Lower concentrations of TGF-beta 1 demonstrated no significant differences from control. Results suggest that the effects of TGF-beta 1 on HPDLF and HGF are both time and dose dependent, with 10(-9) M TGF-beta 1 providing the best response of those concentrations tested. These findings support the concept that TGF-beta 1 may play a role in periodontal regeneration due to its ability to promote fibroblast RNA and protein synthesis. The results also demonstrate that although these two cells types appear morphologically similar, they exhibit distinct biological responses to growth factors such as TGF-beta 1.

Histologic observations of bone remodeling adjacent to endosteal dental implants.

To examine bone morphology associated with endosteal dental implants at various time intervals, we inserted 20 one-stage and 20 two-stage titanium blade implants and 20 one-stage and 20 two-stage titanium root-form implants into 30 dog mandibles. Sixteen implants in 6 control (c) dogs (in situ five months) did not receive bridgework. Sixty-four implants in 24 dogs supported bridges for six, 12, 18, or 24 months. The entire area of the mandible containing the implants was examined by routine light and Nomarski differential interference microscopy (NM) for bone morphology (including osteon orientation) at the implant surface and at regions away from the implant. Control root-form implants were apposed by woven bone, with homogenous compact bone in the cortical plate distant to the implant. After 6 mo of load, immature bone was predominant apposing the implant, but initial osteonal maturation was apparent. NM clearly demonstrated the interstitial and concentric lamellae of the bone. Surprisingly, compact bone formed internal to the cortical plate, an area where trabecular bone is expected. At later periods of load, more mature osteons were seen apposing the implants; however remodeling events were still apparent. These remodeling events extend further away from the implant than was expected if the events resulted only from surgical repair. Also, when the implant inclined so that half was totally in the cortical plate and half in the marrow (in trabecular patterns), osteonal bone appeared to remodel in both areas. Control blade implants and blades loaded for six months were apposed by immature osteons when the implant was placed into the cortical plate. A trabecular meshwork was inferior to the osteonal bone. At 12 mo of load, the bone internal to the cortical plate appeared similar to the lamina dura supporting teeth; however, no PDL existed; the lamina-dura-like pattern directly apposed the implant. Even after 24 mo of load, extensive bone remodeling was apparent adjacent to the implant, markedly different from the bone making up the existing cortical plate. From these data, remodeling activities to blade implants may involve the development of a lamina-dura-like bone morphology after longer periods of load. Osteonal bone was apparent, but only at regions where the implant was inserted into the cortical plate. Further, bone remodeling was apparent even after long periods of load.

Transmission electron and high-voltage electron microscopy of osteocyte cellular processes extending to the dental implant surface.

Examination of the morphology of osteocytes within the bone supporting endosteal dental implants was performed using conventional transmission and high-voltage transmission electron microscopy (HVEM). The in vivo dog model used 72 implants inserted into the premolar region of 18 experimental animals. Forty-eight implants in 12 dogs were used as anterior abutments for fixed bridges for periods up to 12 months. The mineralized matrix of the supporting bone was either directly apposed to the implant surface or was separated from the implant by a narrow region of unmineralized matrix. Osteocytes were routinely observed to be closely associated with the bone-implant interface, as well as at a distance from the implant. Osteocytes were found to extend cellular processes directly to the implant surface through canaliculi. The osteocyte processes contained microfilaments. The three-dimensional capabilities of HVEM elucidated the nature of these cell processes at the point of exit from the osteocyte, as the processes extended through the mineralized matrix, and as the processes terminated at the implant interface. This report suggests that avenues of communication may exist between the implant and the osseous cells, providing intriguing hypotheses regarding biomechanical forces and osteogenesis at the implant interface. Furthermore, an electron-dense deposit was observed upon the inner confines of the canalicular wall, upon the outer aspects of the osteocyte lacuna, and upon the outer aspect of the bone interfacing the implant.

Osteoblast activity at the dental implant-bone interface: transmission electron microscopic and high voltage electron microscopic observations.

The purpose of this report is to present transmission electron microscopic and high voltage transmission electron microscopic (HVEM) observations of a longitudinal investigation examining the activities of osteoblasts and associated tissues apposing titanium and alumina oxide ceramic endosteal dental implants. The HVEM permitted 3-dimensional stereologic observations. All observations were obtained from undecalcified interfacial tissues from this in vivo experimental dog model using commercially available implants placed into the mandible. Two similar implants were placed in both sides of the mandible, with implants in 12 of the 18 dogs supporting fixed bridges for either 6 or 12 months. From the study, we observed that a mineralized matrix exists in direct apposition to the implant. Since bone does not interface the entire length of the implant, other interfacial zones were found to exist which consisted of unmineralized tissues. In such zones, we observed that osteoblasts were routinely found directly at the implant interface to the mandibular bone. These interfacial tissues included unmineralized collagen fibers, proteinaceous material, a finely fibrillar matrix, and the osteoblasts. This study has reinforced the concept that the oral tissue-dental implant interface is a dynamic zone consisting of remodeling activities of the osseous cells and extracellular matrices.

Morphology of the bone that supports endosteal dental implants. Transmission electron microscopic and high voltage electron microscopic observations.

The morphologic features of the bone-dental implant interface were investigated using an in vivo dog model. The undecalcified bone and associated support tissues were serially sectioned and examined with both conventional and high voltage transmission electron microscopy. A varied morphologic appearance of the tissues supporting clinically and radiographically appearing integrated implants was observed. Osteoblasts were observed at the implant interface, and osteocytes were routinely seen encased within lacunae extremely close to the implant surface. Often these osteocytes extended cellular projections to the implant surface. The variable tissue types observed were suggestive of healthy lamellar and appositional type mineralization patterns adjacent to the implants.

Osteogenesis at the dental implant interface: high-voltage electron microscopic and conventional transmission electron microscopic observations.

The osteogenesis of mandibular bone to endosteal dental implants was examined using an in vivo dog model. One half of the implants examined were unloaded implants, with the remaining one half prosthodontically loaded for 6 months. Undecalcified mandibular implant samples were examined with both high-voltage electron microscopy (HVEM) stereology and routine transmission electron microscopy. The osseous interface to integrated implants was shown to vary in its morphology. Mineralized bone was observed directly apposing the implant, often separated from the implant by an electron-dense deposit of approximately 50 nm. Within this densely mineralized matrix, osteocytes were routinely observed. Adjacent areas were shown to contain slightly wider zones of either a less dense mineralized matrix or, alternatively, unmineralized tissue. Other zones consisted of wider unmineralized matrices containing collagen fibers and osteoblasts. These latter zones were consistent with the appearance of an appositional type of bone growth. Because bone is a dynamic, actively remodeling tissue, a varied morphology of the support tissues to dental implant is not unexpected. Areas of mature bone interfacing with successfully integrated implants were demonstrated, as well as areas adjacent to the mature bone that were undergoing remodeling or mineralization. This study has also shown that HVEM stereology is a valuable research tool to investigate the oral tissue interface with dental implants.

Clinical evaluation data from a comparative dental implant investigation in dogs.

This report presents one-year clinical evaluation data from 120 ceramic and titanium cylindrical and titanium blade-type implants placed in the mandibles of 30 adult dogs. Ninety-six of the implants supported fixed bridges. The bone and gingival health was evaluated by the following indices: crevicular fluid volume index; gingival bleeding index; plaque accumulation index; clinical mobility index; and a quantitative mobility index utilizing the Periotest instrument. Results from this investigation suggest that, overall, the ceramic implants exhibited more fractures and had more mobile implants than did the titanium implant systems. Overall, complete one-year clinical evaluation data demonstrate healthy tissue responses to 112 of the 120 implants. Further, the Periotest instrument appears to offer a more quantitative assessment of clinical mobility. Also, it appears that the clinical evaluation protocol utilized in this study is a valid procedure to use for the assessment of clinical serviceability.

Experimental studies of the implant-tissue interface.

This comparative study analyzed the epithelial, gingival connective tissue, and osseous tissue interface with clinically and radiographically integrated endosteal dental implants. Undecalcified interfacial tissues were sectioned for both routine transmission electron microscopy (TEM) and for High Voltage Electron Microscopy (HVEM). A protective perimucosal biological seal was formed by regenerating soft tissues (epithelium and connective tissue). Inferior to this protective soft-tissue attachment seal, the apical support complex was shown to vary in morphology. Mineralized bone was closely apposed to significant regions of the implants, separated only by an electron-dense deposit of approximately 20 nm. Osteoblasts were observed adjacent to the implant, as were osteocytes within the underlying supporting bone. Osteoblasts were observed associated with a connective tissue stroma adjacent to the existent mineralized bone. Osteocyte cellular processes extended toward adjacent osteocytes, toward vascular elements, and directly to the implant surface. These observations demonstrate the healthy interface of mineralized tissues with both root-form and blade implants. Mineralization patterns of the bone supporting the implants appeared consistent with normal mandibular maturation patterns.