Biomedical subjects

D L Cochran

Publications and source records attributed to D L Cochran.

At least 19 recordsLinked to original sources

PubMed2003

Persistent acute inflammation at the implant-abutment interface.

The inflammatory response adjacent to implants has not been well-investigated and may influence peri-implant tissue levels. The purpose of this study was to assess, histomorphometrically, (1) the timing of abutment connection and (2) the influence of a microgap. Three implant designs were placed in the mandibles of dogs. Two-piece implants were placed at the alveolar crest and abutments connected either at initial surgery (non-submerged) or three months later (submerged). The third implant was one-piece. Adjacent interstitial tissues were analyzed. Both two-piece implants resulted in a peak of inflammatory cells approximately 0.50 mm coronal to the microgap and consisted primarily of neutrophilic polymorphonuclear leukocytes. For one-piece implants, no such peak was observed. Also, significantly greater bone loss was observed for both two-piece implants compared with one-piece implants. In summary, the absence of an implant-abutment interface (microgap) at the bone crest was associated with reduced peri-implant inflammatory cell accumulation and minimal bone loss.

Analysis of Variance↗

PubMed2002

Osteoblast-mediated mineral deposition in culture is dependent on surface microtopography.

Osteoblast phenotypic expression in monolayer culture depends on surface microtopography. Here we tested the hypothesis that mineralized bone nodule formation in response to osteotropic agents such as bone morphogenetic protein-2 (BMP-2) and dexamethasone is also influenced by surface microtopography. Fetal rat calvarial (FRC) cells were cultured on Ti implant materials (PT [pretreated], Ra = 0.6 microm; SLA [course grit blasted and acid etched], Ra = 4.0 microm; TPS [Ti plasma sprayed], Ra = 5.2 microm) in the presence of either BMP-2 (20 ng/ml) or 10(-8) M dexamethasone (Dex). At 14 days post-confluence, a homogenous layer of cells covered the surfaces, and stacks of cells that appeared to be nodules emerging from the culture surface were present in some areas on all three Ti surfaces. Cell proliferation decreased while alkaline phosphatase specific activity (ALPase) and nodule number generally increased with increasing surface roughness in both control and treated cultures. There was no difference in cell number between the control and Dex-treated cultures for a particular surface, but BMP-2 significantly reduced cell number compared with control or Dex-treated cultures. Treatment with Dex or BMP-2 further increased ALPase on all surfaces except for PT cultures with Dex. Dex had no effect on nodule area in cultures grown on PT or SLA disks, yet increased nodule number by more than 100% in cultures on PT disks. Though the effect of BMP-2 on nodule number was the same as Dex, BMP-2 increased nodule area on all surfaces except TPS, where area was decreased. Ca and P content of the cell layers in control cultures did not vary with surface roughness. However, cultures treated with Dex had increased Ca content on all surfaces, but the greatest increase was seen on SLA and TPS. BMP-2 increased Ca content in cultures on all surfaces, with the greatest increase on the PT surface. BMP-2 treatment increased P content on all surfaces, whereas Dex only increased P on rough surfaces. Of all cultures examined, the Ca/P weight ratio was 2:1 only on rough surfaces with BMP-2, indicating the presence of bone-like apatite. This was further validated by Fourier transform infrared (FTIR) imaging showing a close association between mineral and matrix on TPS and SLA surfaces with BMP-2-treated cells, and individual spectra indicated the presence of an apatitic mineral phase comparable to bone. In contrast, mineral on the smooth surface of BMP-2-treated cultures and on all surfaces where cultures were treated with Dex was not associated with the matrix and the spectra, not typical of bone apatite, implying dystrophic mineralization. This demonstrates that interactions between growth factor or hormone and surface microtopography can modulate bone cell differentiation and mineralization.

Alkaline Phosphatase↗

PubMed2002

Shear force modulates osteoblast response to surface roughness.

Previous studies have shown that osteoblasts are sensitive to surface roughness. When cultured on Ti, MG63 osteoblast-like cells exhibit decreased proliferation and increased differentiation with increasing surface roughness. In vivo, osteoblasts also are subjected to shear force during osseointegration. To examine how shear force modulates osteoblast response to surface roughness, MG63 cells were cultured on glass disks or Ti disks with three different R(a) values and topographies (PT: R(a) = 0.60 microm; SLA: R(a) = 3.97 microm; TPS: R(a) = 5.21 microm) in a continuous flow device, resulting in shear forces of 0, 1, 5, 14, and 30 dynes/cm(2). Confluent cultures were exposed to fluid flow for 1 h. After an additional 23 h, cell number, alkaline-phosphatase-specific activity, and levels of osteocalcin, TGF-beta1, and PGE2 in the conditioned media were determined. Cell numbers on smooth surfaces (glass and PT) were unaffected by shear force. In contrast, shear force caused a dose-dependent reversal of the decrease in cell numbers seen on rough SLA and TPS surfaces. Alkaline-phosphatase-specific activity was unaffected on glass or PT, but shear force caused a biphasic reduction in the roughness-dependent increase on SLA and TPS that was maximal at 14 dynes/cm(2). There was a similar effect seen with TGF-beta1 levels. Osteocalcin was unaffected on smooth surfaces; shear force caused a dose-dependent reduction in the roughness-stimulated increase seen on SLA and TPS. PGE2 production was increased by shear force on all surfaces. There was a twofold increase in PGE2 levels in the media of MG63 cells cultured on glass and PT in response to 14 dynes/cm(2), but on SLA and TPS, 14 dynes/cm(2) shear force caused a 9-10-fold increase. These results show that osteoblastic response to shear force is modulated by surface topography. The shear-force-mediated decrease in osteoblast differentiation seen in cultures on rough surfaces may be due to increased production of PGE2.

Alkaline Phosphatase↗

PubMed2002

Response of normal female human osteoblasts (NHOst) to 17beta-estradiol is modulated by implant surface morphology.

Titanium (Ti) surfaces with rough microtopographies enhance osteogenic differentiation, local factor production, and response to osteogenic agents in vitro and increase pullout strength of dental implants in vivo. Estrogens regulate bone formation, resorption, and remodeling in females and may be important in implant success. Here, we tested the hypothesis that estrogen modulates osteoblast response to implant surface morphology. Primary female human osteoblasts were cultured to confluence on three Ti surfaces (pretreatment, PT - R(a) 0.60 microm; sandblasted and acid-etched, SLA - R(a) 3.97 microm; and Ti plasma-sprayed, TPS - R(a) 5.21 microm) and treated for 24 h with 10(-7) or 10(-8) M 17beta-estradiol (E(2)). Cell number decreased with increasing surface roughness, but was not sensitive to E(2). Alkaline phosphatase specific activity of isolated cells and cell layer lysates was lower on rough surfaces. E(2) increased both parameters on smooth surfaces, whereas on rough surfaces, the stimulatory effect of E(2) on alkaline phosphatase was evident only when measuring cell layer lysates. Osteocalcin levels were higher in the conditioned media of cells grown on rough surfaces; E(2) had no effect in cultures on the plastic surfaces, but increased osteocalcin production on all Ti surfaces. TGF-beta1 and PGE(2) production was increased on rough surfaces, and E(2) augmented this effect in a synergistic manner; on smooth surfaces, there was no change in production with E(2). The response of osteoblasts to surface topography was modulated by E(2). On smooth surfaces, E(2) affected only alkaline phosphatase, but on rough surfaces, E(2) increased levels of osteocalcin, TGF-beta1, and PGE(2). These results show that normal adult human female osteoblasts are sensitive to surface microtopography and that E(2) can alter this response.

Alkaline Phosphatase↗

PubMed2002

Clinical, radiographic and biochemical assessment of IL-1/TNF-alpha antagonist inhibition of bone loss in experimental periodontitis.

OBJECTIVES: To assess clinical, radiographic, and biochemical markers as diagnostic indicators of disease activity by comparing ligature-induced bone loss in the presence or absence of IL-1/TNF-alpha antagonist inhibition of bone loss in a primate model. MATERIAL AND METHODS: 6 animals with a naturally-occurring gingivitis were evaluated over a 6-week time period following the placement of silk ligatures and initiation of a soft diet. Three animals received intrapapillary injections of soluble receptors (blockers), capable of blocking the biologic activity for both IL-1 and TNF-alpha, and 3 animals received vehicle (control) injections. Injections were given 3X per week over the course of the study. Clinical assessments included a gingival index and quantification of gingival crevicular fluid (GCF) levels. Collected GCF samples were then used in the biochemical assessment of pyridinoline (PYD) and bone alkaline phosphatase (BAP). Radiographic assessment was made using computer-assisted subtraction radiography to measure both bone density (CADIA) values and linear changes in crestal bone height. RESULTS: Significant (p<0.01) changes using both radiographic measures occurred between 2 and 4 weeks following initiation of disease in this model. The use of the blockers significantly (p<0.01) reduced the levels of radiographic bone loss by approximately 50% over that found in the control sites. Both biochemical markers showed the greatest increase during the first two weeks of the study with PYD levels increased 35-fold over baseline levels after 1 week. This difference in response was significantly (p<0.05) greater than the levels found in the non-ligated teeth or in the ligated teeth receiving blockers injections. BAP levels showed significant increases in ligated teeth compared to non-ligated teeth, but failed to show any significant differences between animals treated with vehicle and those treated with IL-1/TNF antagonists. In contrast to these radiographic and biochemical effects, there were no significant differences detected between animals treated with antagonists and the control group for any of the clinical measures. CONCLUSIONS: The results of this study demonstrate that both subtraction radiography and PYD crevicular fluid levels can detect relative differences in periodontal disease progression, while BAP crevicular fluid levels cannot.

Alkaline Phosphatase↗

PubMed2002

Evaluation of a prototype trilayer membrane (PTLM) for lateral ridge augmentation: an experimental study in the canine mandible.

The objective of this animal study was to evaluate a biodegradable/bioresorbable prototype trilayer membrane (PTLM) consisting of two collagen layers and an internal polylactide layer for lateral ridge augmentation in conjunction with two different bone grafting materials: particulate autograft or deproteinized bovine bone mineral (DBBM). In four mongrel dogs, two lateral bone defects per side were created in the mandible. The four defects per dog were randomly subjected to the following grafting treatments 3 months later: 1. PTLM+DBBM, 2. PTLM+particulate autograft, 3. ePTFE membrane+DBBM, 4. ePTFE membrane+particulate autograft. After a healing period of 4 1/2 months, the dogs were sacrificed for histological and histomorphometrical analysis. Percentage calculations for areas showing bone regeneration within the former defect outline were 56.8% for PTLM+DBBM, 85.2% for PTLM+autograft, 52.3% for ePTFE+DBBM, and 96.9% for ePTFE+autograft (differences between autograft and DBBM sites were significant at P<0.01 to P<0.05). Measurements of ridge enlargement (horizontal bone gain) were also significantly better for autograft+ePTFE sites compared to the other three grafting treatments. Histology demonstrated for most PTLM sites a moderate infiltration of lymphocytes and plasma cells adjacent to empty spaces corresponding to polylactide fragments. In addition, these reactions appeared to provoke subsequent resorption of newly formed bone. No such findings were seen in ePTFE sites. The tested prototype membrane cannot be recommended for clinical application.

Absorbable Implants↗

PubMed2002

Long-term changes in soft tissue height on the facial surface of dental implants.

The success of osseous healing around dental implants has allowed for an increased emphasis on soft tissue healing and esthetic results. However, there is limited information profiling the long-term healing of the soft tissues following prosthesis placement. The purpose of this study was to assess the long-term changes in the position of the facial soft tissue margins following restoration of a one-stage implant system. One hundred and six one-stage ITI implants were evaluated in 39 patients. Implants were placed in maxillary and mandibular anterior regions. Clinical assessment of the soft tissues on the midfacial aspect of the implants was performed over a 2-year period, at 3 and 6 month intervals, following placement of the final restoration. A total of 63 implants were placed as multiple units in the mandible, 23 as single units in the maxilla, and 20 as multiple units in the maxilla. There were no implant failures over this time period. Overall, on the facial aspect of 61% of the 106 implants there was 1 mm or more of soft tissue recession, whereas 19% of the implants showed 1 mm or more of gain in soft tissue height. There was a significantly (P < 0.01) greater number of implants showing a gain in soft tissue levels in the mandibular implants compared with the maxillary implants. Of the 39 patients assessed, 24 showed a loss and five showed a gain of 1 mm or more of the soft tissue levels around the implants. Overall, there was a significant decrease in the mean levels of tissue height of 0.6 mm within the first 6 months, with relatively little change afterward. However, in evaluating only patients showing a loss in tissue height around one or more implants, the mean loss in tissue height was 1.6 mm after 24 months. These results suggest that the potential for significant changes in soft tissue levels after completion of restorative therapy need to be considered for implant therapy in esthetic areas.

Adolescent↗

PubMed2002

Effect of porcine fetal enamel matrix derivative on chondrocyte proliferation, differentiation, and local factor production is dependent on cell maturation state.

Recent studies have shown that porcine fetal enamel matrix derivative (EMD) can enhance the osteoinductive ability of demineralized freeze-dried bone allograft (DFDBA) in a nude mouse muscle implantation model. This suggests that one or more components of EMD can regulate the process of endochondral ossification initiated by DFDBA. To substantiate this hypothesis, in the current study, chondrocytes in the endochondral pathway at two stages of maturation were tested for their response to EMD. Chondrocytes were isolated from the resting zone and growth zone (prehypertrophic and upper hypertrophic cell zones) of the costochondral growth plate cartilage of adolescent rats. The results showed that the relatively immature resting zone cells responded to EMD with an increase in proliferation and a decrease in differentiation as measured by alkaline-phosphatase-specific activity. In addition, EMD stimulated a fivefold increase in PGE(2) production, but was without effect on collagen synthesis, proteoglycan sulfation, and TGF-beta(1) production. The more mature growth zone cells also responded to EMD with increased proliferation, but alkaline-phosphatase-specific activity was unchanged, and there was only a modest increase in PGE(2) production. In contrast to resting zone cells, growth zone cells exhibited a decrease in collagen synthesis, proteoglycan sulfation, and TGF-beta(1) production. These observations indicate that EMD has prominent effects on cells in the endochondral pathway. In particular, EMD stimulates the production of more cells, but inhibits their maturation. This would increase the pool of cells available for subsequent differentiation in response to other factors.

Alkaline Phosphatase↗

PubMed2002

Amelogenin is a cell adhesion protein.

Amelogenin, the major protein component of tooth enamel, is shown to be a cell adhesion protein. Since it had been shown that an amelogenin-containing preparation, Emdogain, possessed cell-adhesive activity, we tested the hypothesis that amelogenin was responsible for cell-adhesive activity. Recombinant amelogenin was found to promote adhesion at less than 15 micro g/60-mm plate and requires divalent cations for activity. While we found that amelogenin does not bind to collagen or heparin under physiological conditions, it was demonstrated previously that amelogenin does bind to hydroxyapatite. The cell-adhesive activity of amelogenin may play a role in development and may provide a partial explanation for the therapeutic effects of Emdogain in periodontal regeneration.

Amelogenin↗

PubMed2001

Osteoblast response to titanium surface roughness and 1alpha,25-(OH)(2)D(3) is mediated through the mitogen-activated protein kinase (MAPK) pathway.

When osteoblasts are cultured on surfaces of increasing microroughness, they exhibit decreases in proliferation, increases in differentiation and local factor production, and enhanced response to 1alpha,25(OH)(2)D(3). The cells interact with surfaces through integrins, which signal by the same pathways used by 1alpha,25(OH)(2)D(3), including protein kinase C via phospholipase C and protein kinase A via phospholipase A(2). This provides opportunities for crosstalk that may contribute to the synergistic effects of surface roughness and the vitamin D metabolite. Because these pathways converge at mitogen-activated protein kinase (MAPK), we tested the hypothesis that the extracellular signal-regulated kinase (ERK1/2) subclass of MAPKs mediates the effects of surface roughness and 1alpha,25(OH)(2)D(3). MG63 osteoblast-like osteosarcoma cells were cultured on commercially pure Ti disks with various surface roughnesses: pretreatment (PT; 0.6 microm average roughness [Ra]), coarse grit-blasted and acid-etched (SLA; 4 microm RA), and titanium plasma-sprayed (TPS; 5.2-microm R(a)). At confluence, cells were treated for 24 h with control media or media containing 10(-7) M 1alpha,25(OH)(2)D(3). One-half of the cultures received 1 microm or 10 microm PD98059, a specific inhibitor of the ERK family of MAPKs. PD98059 alone did not affect proliferation, osteocalcin production, or production of transforming growth factor-beta1 or nitric oxide, regardless of the surface roughness. Alkaline phosphatase was reduced by the inhibition of the ERK family kinases on all surfaces to a comparable extent. However, when PD98059 was added to the cultures with 1alpha,25(OH)(2)D(3), the effects of the seco-steroid were blocked, including the synergistic increases seen in MG63 cells cultured on SLA or TPS. These results indicate that ERK1/2 MAPK is required for the maintenance of alkaline phosphatase at control levels and that the effects of 1alpha,25(OH)(2)D(3) are mediated by ERK1/2. However, the effects of surface roughness are not due to the ERK family of MAPKs. This suggests that alternative pathways may be used, including those mediated by other MAPK subclasses.

Cell Adhesion↗

PubMed2001

Both cyclooxygenase-1 and cyclooxygenase-2 mediate osteoblast response to titanium surface roughness.

Previous studies suggest that the enhanced expression of the osteoblastic phenotype exhibited by MG63 osteoblast-like cells on rough Ti surfaces (R(a) 4-5 microm) involves increased production of prostaglandin. Inhibition of prostaglandin synthesis by indomethacin blocks surface-roughness-dependent decreases in cell proliferation and increases in alkaline phosphatase activity and the production of osteocalcin and TGF-beta1. This study examined the hypothesis that the increase in expression of the osteoblastic phenotype noted in MG63 cells cultured on rough Ti surfaces is mediated by inducible cyclooxygenase-2 (Cox-2) whereas Cox-1 modulates prostaglandin production and phenotypic expression of the cells under standard conditions and on smooth Ti surfaces. MG63 cells were cultured on tissue culture plastic, smooth Ti (PT, R(a) = 0.60 microm), and two rough Ti surfaces with differing morphologies (SLA, R(a) = 3.97 microm and TPS, R(a) = 5.21 microm). At 24 h after plating, media were replaced with media containing the general Cox inhibitor indomethacin (10(-7)M), the Cox-1 inhibitor resveratrol (1 or 10 microM), or the Cox-2 inhibitor NS-398 (1 or 10 microM). Media were changed again after 48 h. Five days after plating, osteocalcin, PGE(2), and TGF-beta1 content of the conditioned media were determined. Cell numbers were assessed in the same cultures used for determination of osteocalcin production. Cell layer protein and alkaline phosphatase specific activity were assessed in cultures used to measure PGE(2) and TGF-beta1. Indomethacin, resveratrol, and NS-398 had no effect on cell number. Indomethacin blocked the surface-roughness-dependent increase in PGE(2) production by up to 80%. Similarly, resveratrol inhibited up to 50% of the PGE(2) production on smooth surfaces and up to 80% on rough surfaces. In contrast, NS-398 had no effect on PGE(2) production by cells on smooth surfaces but caused a 60% reduction in cultures on rough surfaces. Indomethacin reduced alkaline phosphatase on all surfaces below basal levels. However, neither resveratrol nor NS-398 had an effect. Indomethacin blocked the stimulatory effect of surface roughness on osteocalcin production while resveratrol only partially reduced osteocalcin production, and NS398 completely blocked the surface-dependent increase. TGF-beta1 production on rough surfaces was blocked by indomethacin. The effects of resveratrol and NS-398 were dose dependent, but neither agent caused total inhibition of the increase noted on SLA, and only resveratrol blocked the increase on TPS. These results indicate that both Cox-1 and Cox-2 are involved in the response of osteoblasts to surface roughness with respect to production of PGE(2), TGF-beta1, and osteocalcin. While prostaglandin mediates the effects of surface roughness on alkaline phosphatase, neither Cox-1 nor Cox-2 appears to be involved, at least with respect to the two inhibitors used.

Alkaline Phosphatase↗

PubMed2001

Tissue response and osteoinduction of human bone grafts in vivo.

Freeze-dried human bone allograft is used clinically as an adjunct to autologous bone graft. When freeze-dried human bone allograft is demineralized, the allograft is osteoinductive, since it causes bone to form heterotopically. Both types of allograft are also used alone, such as in spinal fusions, critical size defects, and periodontal therapy. The purpose of this study was to determine the effect of demineralization on the osteoinductive potential of human bone grafts obtained from two different groups of patients. One group consisted of six patients younger than 42 years of age, while the other group consisted of six patients who were older than 70 years of age. The harvested material was lyophilized and divided into two portions, one of which was used directly while the other was demineralized. Osteoinductive ability was established using an in vivo assay for heterotopic bone formation. Activity in these bone grafts was compared with a batch of commercially prepared demineralized, freeze-dried human bone grafts that had been previously shown to be active and another batch that had been shown to display low ('inactive') osteoinductive ability. A bone induction score was determined for each group of grafts based on the number and size of any ossicles formed. In addition, the area of new bone formation and area of residual particles were determined histomorphometrically. Tissue response to the bone grafts varied with donor age and whether the samples had been demineralized or not. Only demineralized, freeze-dried bone graft from patients younger than 42 years of age was osteoinductive; all other batches displayed little or no osteoinductive activity. In the demineralized, freeze-dried bone from donors younger than 42 years of age, the bone induction score and new bone area were significantly higher than in the other batches of bone graft, and the area of residual particles was reduced. Both demineralized and nondemineralized bone graft from patients older than 70 years of age were encapsulated in dense, fibrous connective tissue. These results may help explain the observed differences in clinical outcome when demineralized, freeze-dried bone graft or nondemineralized, freeze-dried bone graft from different donors is used in bone regeneration applications.

Adult↗

PubMed2001

Local factor production by MG63 osteoblast-like cells in response to surface roughness and 1,25-(OH)2D3 is mediated via protein kinase C- and protein kinase A-dependent pathways.

Titanium (Ti) surface roughness affects bone formation in vivo and osteoblast attachment, proliferation and differentiation in vitro. MG63 cells exhibit decreased proliferation and increased differentiation when cultured on rough Ti surfaces (Ra > 2 microm) and response to 1,25-(OH)2D3 is enhanced, resulting in synergistic increases in TGF-beta1 and PGE2. To examine the hypothesis that surface roughness and 1,25-(OH)2D3 exert their effects on local factor production through independent, but convergent, signaling pathways, MG63 cells were cultured on tissue culture plastic or on smooth (PT, Ra = 0.60 microm) and rough (SLA, Ra = 3.97 microm; TPS, Ra = 5.21 microm) Ti disks. At confluence (5 days), cultures were treated for 24h with 10(-8) M 1alpha,25-(OH)2D3 and active and latent TGF-beta1 in the conditioned media measured by ELISA. Cell layers were digested with plasmin and released TGF-beta1 was also measured. 1,25-(OH)2D3 regulated the distribution of TGF-beta1 between the media and the matrix in a surface-dependent manner; the effect was greatest in the matrix of cells cultured on SLA and TPS. Inhibition of PKA with H8 for the last 24 h of culture increased PGE2 on SLA and TPS, but when present throughout the entire culture period H8 caused an increase in PGE2 on all surfaces. 1,25-(OH)2D3 reduced the effect of H8 on PGE2 production in cultures treated for 24 h. H8 had no effect on TGF-beta1 in the media by itself but caused a complete inhibition of the 1,25-(OH)2D3 dependent increase. Inhibition of PKC with chelerythrine increased PGE2 in a surface-dependent manner and 1,25-(OH)2D3 reduced the effect of the PKC inhibitor. Chelerythrine also increased TGF-beta1 but the effect was not surface dependent; however, 1,25-(OH)2D3 reduced the effects of chelerythrine with the greatest effects on the smooth surface. Thus, the distribution of TGF-beta1 between the media and the matrix is regulated by 1,25-(OH)2D3 in a surface-dependent manner. Surface roughness exerts its effects on TGF-beta1 production via PKC but not PKA. The effect of 1,25-(OH)2D3 on TGF-beta1 production is not via PKC. PKA is involved in the surface-dependent regulation of PGE2 but not in the regulation of PGE2 by 1,25-(OH)2D3 on rough surfaces. Regulation of PKC affects PGE2 production but it is not involved in the surface roughness-dependent response to 1,25-(OH)2D3. These results suggest two independent but interconnected pathways are involved.

Animals↗

PubMed2001

Inhibition of cyclooxygenase by indomethacin modulates osteoblast response to titanium surface roughness in a time-dependent manner.

Prostaglandin E2 (PGE2) and transforming growth factor-beta 1 (TGF-beta 1) production are increased in cultures of osteoblasts grown on rough surfaces and prostaglandins are involved in osteoblast response to surface roughness. In the present study, we examined the effect of inhibiting cyclooxygenase on this response. MG63 osteoblast-like cells were cultured on cpTi disks with Ra values of 0.60 micron (PT), 3.97 microns (SLA), and 5.21 microns (TPS) in the presence or absence of 10(-7) M indomethacin. Treatment was begun on days 1, 2, 3, or 4 after seeding, and all cultures were harvested on day 5. Indomethacin decreased PGE2 release by the cells to less than 50% of basal levels when the cells were cultured on plastic. Cell number decreased with increasing surface roughness and indomethacin treatment abrogated the surface roughness effect over time. Alkaline phosphatase specific activity (ALP) increased with surface roughness; after one day with indomethacin, ALP was decreased on smooth surfaces, but increased on rough surfaces. Over time, ALP decreased on all surfaces examined and remained greater than plastic only in cultures on TPS. Indomethacin also caused a time-dependent decrease in osteocalcin production on rough surfaces, eventually abrogating the increases due to surface roughness, but had no effect on osteocalcin production on smooth surfaces. TGF-beta 1 levels in the cell layer and media were sensitive to surface roughness; on rougher surfaces, TGF-beta 1 shifted from the media to the matrix. Indomethacin reduced TGF-beta 1 levels over time, but the surface roughness effect was still evident at 4 days. This indicates that prostaglandin production mediates the effects of surface roughness, since indomethacin causes a time-dependent abrogation of the response, but has no effect on proliferation, osteocalcin release, or TGF-beta 1 levels on smooth surfaces. Indomethacin's effect was not immediate, suggesting that clinical protocols could be designed that would reduce inflammation without preventing osteoblastic differentiation. The effect of indomethacin was not complete, since TGF-beta 1 and ALP remained elevated on rough surfaces, suggesting that pathways or factors other than prostanoids are involved. TGF-beta 1 is preferentially stored in the matrix, acting on the cells through autocrine signaling, and may contribute to ALP even in the presence of indomethacin. These results demonstrate the importance of local factors in the autocrine regulation of osteogenesis and the potential for factors released in response to surface morphology to act in a paracrine manner.

Alkaline Phosphatase↗

PubMed2001

Lateral ridge augmentation using different bone fillers and barrier membrane application. A histologic and histomorphometric pilot study in the canine mandible.

Lateral ridge augmentation has become a standard treatment option to enhance the bone volume of deficient recipient sites prior to implant placement. In order to avoid harvesting an autograft and thereby eliminating additional surgical procedures and risks, bone grafting materials and substitutes are alternative filler materials to be used for ridge augmentation. Before clinical recommendations can be made, such materials must be extensively studied in experimental models simulating relevant clinical situations. The present pilot study was conducted in three dogs. Different grafting procedures were evaluated for augmentation of lateral, extended (8 x 10 x 14 mm) and chronic bone defects in the mandibular alveolar ridge. Experimental sites received tricalcium phosphate (TCP) granules or demineralized freeze-dried bone allograft (DFDBA) particles. Barrier membranes (ePTFE) were placed for graft protection. These approaches were compared to ridge augmentation using autogenous cortico-cancellous block grafts, either with or without ePTFE-membrane application. After a healing period of six months, the sites were analyzed histologically and histomorphometrically. Autografted sites with membrane protection showed excellent healing results with a well-preserved ridge profile, whereas non-protected block grafts underwent bucco-crestal resorption, clearly limiting the treatment outcome. The tested alloplastic (TCP) and allogenic (DFDBA) filler materials presented inconsistent findings with sometimes encapsulation of particles in connective tissue, thereby reducing the crestal bone width. The present pilot study supports the use of autografts with barrier membranes for lateral ridge augmentation of extended alveolar bone defects.

Alveolar Process↗

PubMed2001

Biologic Width around one- and two-piece titanium implants.

Gingival esthetics around natural teeth is based upon a constant vertical dimension of healthy periodontal soft tissues, the Biologic Width. When placing endosseous implants, however, several factors influence periimplant soft and crestal hard tissue reactions, which are not well understood as of today. Therefore, the purpose of this study was to histometrically examine periimplant soft tissue dimensions dependent on varying locations of a rough/smooth implant border in one-piece implants or a microgap (interface) in two-piece implants in relation to the crest of the bone, with two-piece implants being placed according to either a submerged or a nonsubmerged technique. Thus, 59 implants were placed in edentulous mandibular areas of five foxhounds in a side-by-side comparison. At the time of sacrifice, six months after implant placement, the Biologic Width dimension for one-piece implants, with the rough/smooth border located at the bone crest level, was significantly smaller (P<0.05) compared to two-piece implants with a microgap (interface) located at or below the crest of the bone. In addition, for one-piece implants, the tip of the gingival margin (GM) was located significantly more coronally (P<0.005) compared to two-piece implants. These findings, as evaluated by nondecalcified histology under unloaded conditions in the canine mandible, suggest that the gingival margin (GM) is located more coronally and Biologic Width (BW) dimensions are more similar to natural teeth around one-piece nonsubmerged implants compared to either two-piece nonsubmerged or two-piece submerged implants.

Analysis of Variance↗

PubMed2001

Human histology of new attachment after root coverage using subepithelial connective tissue graft.

BACKGROUND, AIMS: Connective tissue grafts are used successfully in periodontal therapy for root coverage. However, reports on the histologic interface between the root surface and the grafted tissue have been few in number. This report describes a case study in which a subepithelial connective tissue graft was placed in a 27-year-old female on the maxillary left side. METHODS: The graft (15 mm long, 10 mm wide, 1.5 mm thick) included palatal periosteum and was placed with the periosteal side facing the exposed bone and root surfaces. RESULTS: 15 weeks after grafting, the teeth presented with residual recessions of 1 mm, and buccal probing depths were approximately 1 mm. 14 months post-surgery, the 1st maxillary premolars on both sides were extracted for orthodontic therapy. Clinical parameters at the graft site remained as at 15 weeks. Histologic analysis of tooth #24 showed that the sulcular epithelium was keratinized; epithelium lining the dentin exhibited rete ridges projecting into the gingival connective tissue; and junctional epithelium extended over new cementum. New connective tissue attachment was also observed, including periodontal ligament. CONCLUSION: Biological width was comparable pre- and post-surgery, indicating a real gain in attachment of 3.9 mm.

Adult↗

PubMed2001

Influence of the size of the microgap on crestal bone changes around titanium implants. A histometric evaluation of unloaded non-submerged implants in the canine mandible.

BACKGROUND: Endosseous implants can be placed according to a non-submerged or submerged approach and in 1- or 2-piece configurations. Recently, it was shown that peri-implant crestal bone changes differ significantly under such conditions and are dependent on a rough/smooth implant border in 1-piece implants and on the location of an interface (microgap) between the implant and abutment/restoration in 2-piece configurations. Several factors may influence the resultant level of the crestal bone under these conditions, including movements between implant components and the size of the microgap (interface) between the implant and abutment. However, no data are available on the impact of possible movements between these components or the impact of the size of the microgap (interface). The purpose of this study was to histometrically evaluate crestal bone changes around unloaded, 2-piece non-submerged titanium implants with 3 different microgap (interface) dimensions and between implants with components welded together or held together by a transocclusal screw. METHODS: A total of 60 titanium implants were randomly placed in edentulous mandibular areas of 5 hounds forming 6 different implant subgroups (A through F). In general, all implants had a relatively smooth, machined suprabony portion 1 mm long, as well as a rough, sandblasted, and acid-etched (SLA) endosseous portion, all placed with their interface (microgap) 1 mm above the bone crest level and having abutments connected at the time of first-stage surgery. Implant types A, B, and C had a microgap of < 10 microns, approximately 50 microns, or approximately 100 microns between implant components as did types D, E, and F, respectively. As a major difference, however, abutments and implants of types A, B, and C were laser-welded together, not allowing for any movements between components, as opposed to types D, E, and F, where abutments and implants were held together by abutment screws. Three months after implant placement, all animals were sacrificed. Non-decalcified histology was analyzed histometrically by evaluating peri-implant crestal bone changes. RESULTS: For implants in the laser-welded group (A, B, and C), mean crestal bone levels were located at a distance from the interface (IF; microgap) to the first bone-to-implant contact (fBIC) of 1.06 +/- 0.46 mm (standard deviation) for type A, 1.28 +/- 0.47 mm for type B, and 1.17 +/- 0.51 mm for type C. All implants of the non-welded group (D, E, and F) had significantly increased amounts of crestal bone loss, with 1.72 +/- 0.49 mm for type D (P < 0.01 compared to type A), 1.71 +/- 0.43 mm for type E (P < 0.02 compared to type B), and 1.65 +/- 0.37 mm for type F (P < 0.01 compared to type C). CONCLUSIONS: These findings demonstrate, as evaluated by non-decalcified histology under unloaded conditions in the canine mandible, that crestal bone changes around 2-piece, non-submerged titanium implants are significantly influenced by possible movements between implants and abutments, but not by the size of the microgap (interface). Thus, significant crestal bone loss occurs in 2-piece implant configurations even with the smallest-sized microgaps (< 10 microns) in combination with possible movements between implant components.

Alveolar Bone Loss↗