Biomedical subjects

David L Cochran

Publications and source records attributed to David L Cochran.

31 records · Page 2Linked to original sources

PubMed2003

Guided bone regeneration around titanium plasma-sprayed, acid-etched, and hydroxyapatite-coated implants in the canine model.

BACKGROUND: Endosseous dental implants with rough surfaces have been designed to improve early healing, especially in areas of poor bone or insufficient bone quantity. The aim of this study was to histomorphometrically assess the bone-to-implant contact on 3 different rough-surfaced implants following guided bone regeneration. METHODS: Mandibular premolars and first molars were extracted in 12 dogs, and healing was allowed for 6 months. Six implant osteotomy sites were prepared, 3 per side, followed by the creation of 7.3 mm wide by 5 mm deep surgical defects in the coronal section of the osteotomy sites. Ten-mm long titanium screw-type implants with titanium plasma-sprayed (TPS), hydroxyapatite-coated (HA), or acid-etched (AE) surfaces were placed; the surrounding defects were filled with canine demineralized freeze-dried bone allograft; implants/grafts were covered with expanded polytetrafluoroethylene membranes; and the tissue was closed. Following a healing period of 4 months, the animals were sacrificed and mandibular blocks were harvested for histomorphometric analysis. RESULTS: The mean percentage of bone-to-implant contact in the defect and non-defect areas for the different implant surfaces was: AE 16.24% defect, and 28.78% non-defect; TPS 25.08% defect, and 16.96% non-defect; and HA 48.25% defect and 26.60% non-defect. Within the defect, the mean difference in the bone-to-implant contact was significant for HA compared to TPS (P < 0.0001) and HA versus AE (P < 0.0001); TPS versus AE was not significant (P = 0.063). In the non-defect areas, the mean difference in the bone-to-implant contact was significant for AE versus TPS (P = 0.010); all other comparisons were not significant. There were 18 membrane exposures in the 72 implant sites. Data were analyzed again to assess the impact of membrane complications. Using a 1-way analysis of variance, the bone-to-implant contact was compared between the sites with and without membrane complications. No significant differences were seen in the defect areas or in the non-defect areas between the sites with and without membrane complications. CONCLUSION: In this study, the bone-to-implant contact in regenerated bone was greatest when an HA-coated implant was used.

Acid Etching, Dental↗

PubMed2003

Evaluation of human recession defects treated with coronally advanced flaps and either enamel matrix derivative or connective tissue. Part 2: Histological evaluation.

BACKGROUND: A number of surgical procedures are effective in covering denuded root surfaces. The first paper in this series evaluated the subepithelial connective tissue graft and the coronally advanced flap with enamel matrix derivative (EMD). That paper revealed no significant difference in the percent of root coverage between the two treatments (P = 0.82). There is limited human histological evidence of the type of attachment achieved with these types of procedures. This paper presents a human case report detailing the histological nature of the attachment of these two treatments to the root surfaces previously exposed by recession. METHODS: One patient presented with two hopeless teeth that were randomized to receive either a subepithelial connective tissue graft or a coronally advanced flap plus EMD. The surgery was accomplished in accordance to the protocol previously described. The teeth and a small collar of tissue were removed at 6 months and underwent histological analysis. RESULTS: Histological evaluation of the subepithelial connective tissue graft revealed a connective tissue attachment between the tooth and graft, and no histological evidence of cementum, bone, or periodontal ligament (PDL) and, therefore, regeneration. In addition, there appeared to be some resorption of the dentin adjacent to the graft. Histological evaluation of the coronally advanced flap with EMD revealed new cementum, organizing PDL fibers and islands of condensing bone at a constant distance from the root surface. CONCLUSIONS: The subepithelial connective tissue graft in this study was found to have adhered to the root surface primarily by a connective tissue attachment with some evidence of root resorption. The coronally advanced flap with EMD was found histologically to have all the tissues necessary for regeneration: new cementum, organizing PDL fibers, and islands of condensing bone. These histologic sections strongly suggest that enamel matrix derivative works in a biomimetic fashion by mimicking the natural process of tooth development.

Adult↗

PubMed2003

Periodontal regeneration with a combination of enamel matrix proteins and autogenous bone grafting.

BACKGROUND: Attempts to stimulate periodontal regeneration in the past have focused on either filling the defect with some type of material or providing a space for host cells to repopulate the site and elicit new tissue. In some cases, these approaches have been combined with the assumption that the filler material will help maintain the space necessary for the host cells to invade the area. Growth stimulating substances such as growth factors and other proteins have also been used to encourage periodontal tissue regeneration and histological evaluation supports the use of these substances. Thus, the role for and the necessity of a certain amount of space maintenance for periodontal regeneration is not exactly understood. In addition, it is not known if there is some critical size required for space maintenance or for exactly how long the space must be maintained in order for the host cells to stimulate new cementum, periodontal ligament, and bone. The goal of this study was to evaluate periodontal regeneration in intrabony defects of various sizes treated with a combination of enamel matrix proteins and autogenous bone graft. METHODS: Periodontal defects ranging in size from 1 to 6 mm were randomized and created bilaterally beside three teeth in the mandibles of baboons. Plaque was allowed to accumulate around wire ligatures placed into the defects. After 2 months, the wire ligatures were removed, the teeth and roots scaled and root planed, and a notch was placed with a chisel at the base of the defect. On one side of the mandible, neutral ethylene diamine tetracetic acid and enamel matrix derivative (EMD) were first used to treat the defect. Autogenous bone taken from the same surgical site was treated with enamel matrix derivative in a dampen dish and then added to the EMD-treated defects. The other side of the mandible served as control with neutral ethylene diamine tetracetic acid and scaling and root planing. Flaps were sutured and the animals were allowed to heal without oral hygiene procedures. After 5 months, the animals were sacrificed and the teeth were processed for histological evaluation. RESULTS: The results revealed new cementum, periodontal ligament with Sharpey's fibers, and new bone tissue similar to native periodontal tissues. Remnants of the autogenous bone chips were still present at this 5-month post-healing period. Thus periodontal regeneration occurred in all sizes of the periodontal defects. In general, EMD plus autogenous graft treatment resulted in greater tissue formation than controls. In fact, in many cases, very dramatic tissue formation occurred far coronal to the base of the defects in the EMD plus autogenous graft-treated lesions. In addition, horizontal bone fill occurred in the defects and was prominent in the 4 or 6 mm wide lesions. When evaluating the combined 1 and 2 mm defects, the height of new cementum with EMD plus graft was 3.88 mm versus 2.03 mm in the controls, a statistically significant (P < 0.005) difference. In the wider (4 and 6 mm) lesions, this difference was not significant and was much less between treated and control lesions with 2.78 and 2.57 mm of new cementum respectively. In the case of new bone height, in the smaller lesions EMD plus graft resulted in 4.00 mm new bone versus 2.22 mm in the controls, again a statistically significant (P < 0.005) difference. In the larger lesions, EMD plus autogenous bone graft had 3.24 mm new bone height compared to 2.71 mm in the controls, a difference that was not statistically significant. Additionally, in the smaller lesions, new cementum width at the level of the notch was twice as great (statistically significant, P < 0.015) in the EMD plus graft sites compared to control. The width of the periodontal ligament at the coronal aspect of the new bone tissue was similar in the smaller lesions between treated and control sites. The results from the wider defects must be interpreted cautiously as the interproximal bone heights were remodeled adjacent to the wider defects and likely limited the potential for regeneration. CONCLUSIONS: The combination of enamel matrix derivative plus autogenous bone graft stimulated statistically significant periodontal regeneration in the more narrow 1 and 2 mm lesions. No statistically significant difference was observed in the wider 4 and 6 mm lesions. In many cases, dramatic amounts of new cementum, Sharpey's fibers, periodontal ligament, and bone tissue were formed far above the notch placed at the base of the contaminated defects. This was especially significant considering the width of some of the defects and the fact that no oral hygiene was performed over the 5-month healing period. This periodontal regeneration occurred in the absence of exogenous growth factors or barrier membranes. In summary, the combination of enamel matrix derivative and autogenous bone represents a therapeutic combination that can be highly effective in stimulating significant amounts of periodontal regeneration.

Alveolar Bone Loss↗

PubMed2003

Platelet-derived growth factor-BB stimulated cell migration mediated through p38 signal transduction pathway in periodontal cells.

BACKGROUND: Intracellular signaling pathways mediate specific responses to growth factors. The manipulation of these pathways ultimately may be used to control the clinical outcomes of periodontal regenerative therapy. The purpose of this study was to examine the role of the p38 signal transduction pathway in the responses of periodontal cells to platelet-derived growth factor-BB (PDGF). METHODS: Primary cultures of human periodontal ligament cells (PDLs) and gingival fibroblasts (GFs) were used for all experiments. Cell numbers, 3H-thymidine incorporation, and Boyden chamber assays were used to characterize the effects of SB 203580 (SB), a specific inhibitor of the p38 signaling pathway, on cell proliferation and migration. An in vitro wound model also was used to assess the effects of SB. For the in vitro wound assay, triplicate wells were incubated for 1, 3, 5, and 7 days using 0.1% fetal bovine serum (FBS), 10% FBS +/- 10 microM SB, or 20 ng/ml PDGF +/- 10 microM SB. Digital histomorphometric analysis assessed cellular fill within the wound area. RESULTS: SB specifically inhibited PDGF-induced migration in the Boyden chamber assays without affecting cell proliferation. The wound model data showed similar levels of wound fill for PDLs and GFs in 10% FBS. Relative to 10% FBS, PDLs stimulated with PDGF showed significantly (P < 0.01, analysis of variance) greater wound fill (74%) than GFs (12%). SB inhibited the PDGF-induced wound fill of PDLs and GFs by 64% and 57%, respectively. This inhibition was significant (P < 0.01, ANOVA) only for PDLs. The addition of SB to 10% FBS did not significantly affect the wound fill response of either cell type compared to 10% FBS alone. CONCLUSIONS: These results demonstrate that periodontal cells possess distinct responses to PDGF that may be altered at the signal transduction level. The manipulation of these responses through the use of inhibitors to specific signaling pathways may enhance our control of periodontal regeneration in the future.

Adult↗

PubMed2003

Clinical and histologic evaluation of bone-replacement grafts in the treatment of localized alveolar ridge defects. Part 2: bioactive glass particulate.

The purpose of this study was to evaluate the feasibility of using a bioactive alloplast and a physical barrier to augment localized alveolar ridge defects for the subsequent placement of dental implants. Twelve systemically healthy patients (aged 29 to 55 years) with inadequate dental alveolar ridge widths were selected for study. All patients completed initial therapy, which included scaling, root planing, and oral hygiene instruction. All ridge defects were augmented with a bioactive glass alloplast and a titanium-reinforced e-PTFE barrier. Vertical (height) and horizontal (width) hard tissue measurements were taken the day of ridge augmentation surgery (baseline) and at the 6-month reentry surgery. The change in ridge width varied from a loss of 1 mm to a gain of 4.5 mm, with a mean gain of 1.1 mm (P < .03). Eight of the 12 sites gained 1 mm or less. The difference in mean ridge width gain between maxillary and mandibular sites was not statistically significant (P > .08). Mean ridge width gain was 1.1 mm for both maxillary and mandibular sites. There was a loss in bone height of 0.3 mm from baseline. Four implants in four patients could not be placed because of inadequate ridge width augmentation. Histologic examination of the grafted sites revealed connective tissue encapsulation of most residual graft particles. In this study, bioactive glass particulate and an e-PTFE barrier did not consistently augment localized ridge defects for dental implant placement.

Adult↗

PubMed2003

Healing of periapical lesions with complete loss of the buccal bone plate: a histologic study in the canine mandible.

This study evaluated periapical healing of induced apical lesions with concomitant loss of the buccal bone plate in a dog model using four foxhounds. In an initial surgery, pulp cavities of mandibular premolars were exposed to induce apical lesions. In the same session, the cortical bone covering the buccal root surfaces was surgically removed to simulate buccal bone loss. After radiographic confirmation of the development of apical lesions, sites were reentered for surgical treatment. Following apical and buccal debridement, root-end resection, and root-end filling, sites were subjected to three different treatment modalities: (1) flap readaptation (controls); (2) placement of a collagen membrane covering the apical defect and denuded root surface; or (3) placement of an anorganic bovine bone filler into the apical defect and onto the exposed buccal root surface, with additional application of a collagen membrane. Animals were sacrificed 7 months following the second surgery. Step sections were analyzed histometrically and morphometrically for periapical healing. Sites with membrane + filler showed a statistically significantly lower mean percentage of new bone formation within the former defect compared to both membrane-alone and control sites. No significant differences were found for tissue components deposited on the cut root face across treatment groups. Formation of a continuous thin layer of new cementum covering the exposed dentin surface and root-end filling material was a frequent finding. Analysis of the tissue regeneration on the buccal root aspect as well as the clinical periodontal parameters will be presented in a separate article.

Absorbable Implants↗

PubMed2002

Biomechanical comparison of the sandblasted and acid-etched and the machined and acid-etched titanium surface for dental implants.

To make a direct biomechanical comparison between the sandblasted and acid-etched surface (SLA) and the machined and acid-etched surface (MA), a well-established animal model for implant removal torque testing was employed, using a split-mouth experimental design. All implants had an identical cylindrical solid-screw shape with the standard ITI thread configuration, without any macroscopic retentive structures. After 4, 8, and 12 weeks of bone healing, removal torque testing was performed to evaluate the interfacial shear strength of each surface type. Results showed that the SLA surface was more powerful in enhancing the interfacial shear strength of implants in comparison with the MA surface. Removal torque values of the SLA-surfaced implants were about 30% higher than those of the MA-surfaced implants (p = 0.002) except at 4 weeks, when the difference was at the threshold of statistical significance (p = 0.0519). The mean removal torque values for the SLA implants were 1.5074 Nm at 4 weeks, 1.8022 Nm at 8 weeks, and 1.7130 Nm at 12 weeks; and correspondingly, 1.1924 Nm, 1.3092 Nm, and 1.3226 Nm for the MA implants. It can be concluded that the SLA surface achieves a better bone anchorage than the MA surface, and that sandblasting before acid etching has a beneficial effect on the interfacial shear strength. As regards the bone-implant interfacial stiffness calculated from the torque-rotation curve, the SLA implants showed an overall more than 5% higher stiffness compared with the MA implants, although the difference did not reach the statistical significance level.

Acid Etching, Dental↗

PubMed2002

The use of reduced healing times on ITI implants with a sandblasted and acid-etched (SLA) surface: early results from clinical trials on ITI SLA implants.

ITI dental implants are available with two bone-anchoring surfaces, a titanium plasma-sprayed (TPS) surface, and a recently introduced sandblasted and acid-etched (SLA) surface. Cell culture and animal tests demonstrate that the SLA surface stimulates bone cell differentiation and protein production, has large amounts of bone-to-implant contact, and results in large removal torque values in functional testing of the bone contact. As a result of these studies, a prospective human clinical trial was initiated to determine whether the 4.1 mm diameter SLA ITI solid screw implants could be predictably and safely restored as early as six weeks after implant placement surgery. The protocol restricted the use of the reduced healing time to a) healthy patients with sufficient bone volume to surround the implant, and b) those patients who had good bone quality (classes I-III) at the implant recipient site. Patients with poorer bone quality (class IV) did not have restorations until 12 weeks after implant placement. The clinical trial is an ongoing multicenter trial, with six centers in four countries, and with follow-up over five years. The primary outcome variable was abutment placement with a 35 Ncm force, with no countertorque and no pain or rotation of the implant. A secondary outcome was implant success, as defined by no mobility, no persistent pain or infection, and no peri-implant radiolucency. To date, 110 patients with 326 implants have completed the one-year post-loading recall visit, while 47 patients with 138 implants have completed the two-year recall. Three implants were lost prior to abutment connection. Prosthetic restoration was commenced after shortened healing times on 307 implants. The success rate for these implants, as judged by abutment placement, was 99.3% (with an average healing time of 49 days). Life table analyses demonstrated an implant success rate of 99.1%, both for 329 implants at one year and for 138 implants at two years. In the 24-month period after restoration, no implant losses were reported for the 138 implants. These results demonstrate that, under defined conditions, solid screw ITI implants with an SLA endosseous surface can be restored after approximately six weeks of healing with a high predictability of success, defined by abutment placement at 35 Ncm without countertorque, and with subsequent implant success rates of greater than 99% two years after restoration.

Acid Etching, Dental↗

PubMed2002

Role of glutathione metabolism of Treponema denticola in bacterial growth and virulence expression.

Hydrogen sulfide (H(2)S) is a major metabolic end product detected in deep periodontal pockets that is produced by resident periodontopathic microbiota associated with the progression of periodontitis. Treponema denticola, a member of the subgingival biofilm at disease sites, produces cystalysin, an enzyme that catabolizes cysteine, releasing H(2)S. The metabolic pathway leading to H(2)S formation in periodontal pockets has not been determined. We used a variety of thiol compounds as substrates for T. denticola to produce H(2)S. Our results indicate that glutathione, a readily available thiol source in periodontal pockets, is a suitable substrate for H(2)S production by this microorganism. In addition to H(2)S, glutamate, glycine, ammonia, and pyruvate were metabolic end products of metabolism of glutathione. Cysteinyl glycine (Cys-Gly) was also catabolized by the bacteria, yielding glycine, H(2)S, ammonia, and pyruvate. However, purified cystalysin could not catalyze glutathione and Cys-Gly degradation in vitro. Moreover, the enzymatic activity(ies) in T. denticola responsible for glutathione breakdown was inactivated by trypsin or proteinase K, by heating (56 degrees C) and freezing (-20 degrees C), by sonication, and by exposure to N alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK). These treatments had no effect on degradation of cysteine by the purified enzyme. In this study we delineated an enzymatic pathway for glutathione metabolism in the oral spirochete T. denticola; our results suggest that glutathione metabolism plays a role in bacterial nutrition and potential virulence expression.

Cystathionine gamma-Lyase↗

PubMed2002

Influence of the size of the microgap on crestal bone levels in non-submerged dental implants: a radiographic study in the canine mandible.

BACKGROUND: Accumulating evidence suggests that alveolar crestal bone resorption occurs as a result of the microgap that is present between the implant-abutment interface in dental implants. The objective of this longitudinal radiographic study was to determine whether the size of the interface or the microgap between the implant and abutment influences the amount of crestal bone loss in unloaded non-submerged implants. METHODS: Sixty titanium implants having sandblasted with large grit, acid-etched (SLA) endosseous surfaces were placed in edentulous mandibular areas of 5 American fox hounds. Implant groups A, B, and C had a microgap between the implant-abutment connection of <10 microm, 50 microm, or 100 microm, respectively, as did groups D, E, and F, respectively. Abutments were either welded (1 -piece) in groups A, B, and C or non-welded (2-piece screwed) in D, E, and F. All abutment interfaces were placed 1 mm above the alveolar crest. Radiographic assessment was undertaken to evaluate peri-implant crestal bone levels at baseline and at 1, 2, and 3 months after implant placement whereupon all animals were sacrificed. RESULTS: The size of the microgap at the abutment/implant interface had no significant effect upon crestal bone loss. At 1 month, most implants developed crestal bone loss compared with baseline levels. However, during this early healing period, the non-welded group (D, E, and F) showed significantly greater crestal bone loss from baseline to one month (P <0.04) and 2 months (P < 0.02) compared with the welded group (A, B, and C). No significant differences were observed between these 2 groups at 3 months (P > 0.70). CONCLUSIONS: Crestal bone loss was an early manifestation of wound healing occurring after 1 month of implant placement. However, the size of the microgap at the implant-abutment interface had no significant effect upon crestal bone resorption. Thus, 2-piece non-welded implants showed significantly greater crestal bone loss compared with 1-piece welded implants after 1 and 2 months suggesting that the stability of the implant/abutment interface may have an important early role to play in determining crestal bone levels. At 3 months, this influence followed a similar trend but was not observed to be statistically significant. This finding implies that implant configurations incorporating interfaces will be associated with biological changes regardless of interface size and that mobility between components may have an early influence on wound healing around the implant.

Alveolar Bone Loss↗

PubMed2002

Factors that modulate the effects of bone morphogenetic protein-induced periodontal regeneration: a critical review.

The healing process initiated by a single molecular species of bone morphogenetic protein (BMP) such as BMP-2 or BMP-7 sets in motion a cascade of cellular events resulting in differentiation of progenitor cells into phenotypes involved in periodontal regeneration. For example, animal studies show that a single dose of recombinant human (rh) BMP-2 increases the rate of normal intramembranous bone formation and enhanced cementum formation during periodontal wound healing. However, the optimal effects of BMPs are modulated by a range of factors that need careful evaluation in clinical studies. These factors include the influence of root conditioning, occlusal loading, BMP dose, and the release characteristics of the carrier as well as the suitability of the model to evaluate the efficacy of BMPs. Each of these factors may affect the rate of BMP-induced osteogenesis and cementogenesis and subsequent periodontal ligament (PDL) formation during the early and late stages of periodontal wound healing. Although BMP-2 initiates stem cells along an osteogenic pathway, the dose may have to be of sufficient concentration to ensure other growth and differentiation factors do not redirect or retard the osteogenic potential of the cell. Understanding when to manipulate the cell's differentiation pathway with the application of single or multiple doses of BMPs at the appropriate concentration is required to optimize the effect of BMPs in periodontal wound healing. Therefore, different release profiles from the same carrier may be particularly important in tissues with mixed cell populations such as in the periodontium, where similar tissues like bone and cementum grow at different rates. Furthermore, treatment of intrabony defects with BMPs are likely to not only require appropriate temporal release of the BMP(s), but also a carrier that can serve as a template for new tissue formation providing space maintenance and supporting the mucoperiosteal flap. Many of these issues have not been adequately addressed from a periodontal standpoint; therefore the purpose of this review is to clarify our current understanding of the factors that are likely to modulate the effects of BMP-induced periodontal regeneration. Moreover, assessing the importance of these factors is essential prior to conducting expensive human clinical trials.

Acid Etching, Dental↗

PubMedDate not supplied

Resonance frequency measurement of implant stability in vivo on implants with a sandblasted and acid-etched surface.

PURPOSE: To determine the changes in stability as a reflection of early healing around single-stage, roughened-surface implants in humans utilizing resonance frequency analysis (RFA). RFA makes use of a transducer, attached to an implant, which is excited over a range of sound frequencies with subsequent response analysis. MATERIALS AND METHODS: Twenty patients had 1 to 4 implants placed in the posterior maxilla or mandible. Bone type was classified into 1 of 4 groups according to the Lekholm and Zarb index (1985). RFA was used for direct measurement of implant stability on the day of implant placement and consecutively once per week for 6 weeks and at weeks 8 and 10. RESULTS: Twenty-seven ITI SLA implants placed in the premolar and molar regions of the maxilla and mandible were evaluated. Early failure occurred with 1 implant related to parafunction. The remaining 26 implants were distributed as follows: 29.6% in Type 1 bone, 37% in Type 2 or 3 bone, and 33.3% in Type 4 bone. The lowest mean stability measurement was at 3 weeks for all bone types. The percentage decrease in stability from baseline to 3 weeks was highest for Type 4 bone (8.6%), as was the percentage increase in stability from 3 to 10 weeks (26.9%). A Bonferroni adjusted Student t test comparison of bone groups at each time point revealed highly significant differences between implant stability in Types 1 and 4 bone at 3 weeks (P = .004) and a moderately significant difference between Types 2, 3, and 4 bone (P = .08) at 3 weeks. Implant stability did not change significantly during the 10-week period in Type 1 bone (P > .10). With the same test, by 5 weeks, no bone groups showed any difference in implant RFA measurements (P = 1.0). DISCUSSION: This study demonstrated the lowest values for implant stability at 3 weeks after placement for all bone types. This effect was statistically significant and most pronounced in Type 4 bone. CONCLUSION: There was no significant difference in the pattern of stability changes among different bone types after 5 weeks of healing.

Acid Etching, Dental↗

PubMedDate not supplied

The effect of a machined collar on coronal hard tissue around titanium implants: a radiographic study in the canine mandible.

PURPOSE: The purpose of this study was to radiographically evaluate the effect of a machined titanium coronal collar on the marginal bone around 1-part endosseous dental implants placed at different heights relative to the bone crest. MATERIALS AND METHODS: Sixty dental implants were placed in edentulous spaces bilaterally in 5 foxhounds. Thirty test implants had a sandblasted, large-grit, dual acid-etched surface (SLA) over the entire length of the implant. The other 30 implants (control) had a machined collar around the most coronal 1.8 mm of the implant; an SLA surface covered the remainder of the implant. Both control and test implants were placed at 3 distinct levels relative to the bone crest. Six implants (3 control and 3 test) were randomly placed side by side in each hemimandible. Radiographs were taken at placement (baseline) and monthly for 6 months postplacement using a standardized radiographic template. RESULTS: Fifty-eight of the implants integrated and were analyzed on each proximal surface. Bone loss occurred around all implants over the 6 months of the study. In general, implants placed with the top of the SLA surface above the bone crest had significantly less bone loss than implants with the top of the SLA surface placed flush with the bone level. Apically placed implants had greater bone loss than coronally placed implants. The magnitude of bone loss around paired control and test implants was approximately the same. DISCUSSION AND CONCLUSION: The least bone loss with each implant type was observed when the top of the implant was placed above the alveolar crest. When there was no machined collar, the least distance from the implant top to the bone crest (not, however, the least bone loss) was observed when the top of the implant was level with the bone crest.

Alveolar Bone Loss↗