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Biomedical subjects

Ray C Williams

Publications and source records attributed to Ray C Williams.

7 recordsLinked to original sources
PubMed2006

Risk factors for endosseous dental implant failure.

Failures of endosseous dental implants are rare and tend to cluster in patients with common profiles or risk factors. Clinical trials indicate that factors related to implant devices, anatomy, occlusion,systemic health or exposures, microbial biofilm, host immuno-inflammatory responses, and genetics may increase the risk for im-plant complications or loss. In general, factors associated with the patient appear more critical in determining risk for implant failure than those associated with the implant itself. Several risk factors can be modified. For example, the patient can modify smoking and the clinician can modify implant selection, site preparation,and loading strategy. In identifying these factors and making appropriate interventions, clinicians can enhance success rates while improving oral function, esthetics, and patient well-being.

Dental Implantation, Endosseous↗
PubMed2006

Cyclooxygenase-2 inhibition selectively attenuates bone morphogenetic protein-6 synthesis and bone formation during guided tissue regeneration in a rat model.

OBJECTIVES: Bone formation during guided tissue regeneration is a tightly regulated process involving cells, extracellular matrix and growth factors. The aims of this study were (i) to examine the expression of cyclooxygenase-2 (COX-2) during bone regeneration and (ii) the effects of selective COX-2 inhibition on osseous regeneration and growth factor expression in the rodent femur model. MATERIAL AND METHODS: A standardized transcortical defect of 5 x 1.5 mm was prepared in the femur of 12 male rats and a closed half-cylindrical titanium chamber was placed over the defect. The expression of COX-2 and of platelet-derived growth factor-B (PDGF-B), bone morphogenetic protein-6 (BMP-6) and insulin-like growth factor-I/II (IGF-I/II) was analyzed at Days 3, 7, 21 and 28 semiquantitatively by reverse transcriptase-polymerase chain reaction and immunohistochemistry. The effects of COX-2 inhibition by intraperitoneal injection of NS-398 (3 mg/kg/day) were analyzed in five additional animals sacrificed at Day 14. RESULTS: Histomorphometry revealed that new bone formation occurred in the cortical defect area as well as in the supracortical region, i.e. region within the chamber by Day 7 and increased through Day 28. Immunohistochemical evidence of COX-2 and PDGF-B levels were observed early (i.e. Day 3) and decreased rapidly by Day 7. BMP-6 expression was maximal at Day 3 and slowly declined by Day 28. In contrast, IGF-I/II expression gradually increased during the 28-day period. Systemic administration NS-398 caused a statistically significant reduction (P<0.05) in new bone formation (25-30%) and was associated with a statistically significant reduction in BMP-6 protein and mRNA expression (50% and 65% at P<0.05 and P<0.01, respectively). PDGF-B mRNA or protein expression was not affected by NS-398 treatment. CONCLUSION: COX-2 inhibition resulted in reduced BMP-6 expression and impaired osseous regeneration suggesting an important role for COX-2-induced signaling in BMP synthesis and new bone formation.

Animals↗
PubMed2006

Inhibition of experimental gingivitis in beagle dogs with topical mercaptoalkylguanidines.

BACKGROUND: Nitric oxide is a free radical produced in host tissues by constitutive and inducible forms of the enzyme nitric oxide synthase. Nitric oxide plays physiological roles, but it is also involved in the pathophysiology of several inflammatory conditions, including arthritis, ulcerative colitis, and circulatory shock. Local increases in inducible nitric oxide synthase (iNOS) and reactive nitrogen products have also been demonstrated in humans and animals with periodontal disease. This masked, randomized, placebo-controlled preclinical investigation examined the effect of two mercaptoalkylguanidines, mercaptoethylguanidine (MEG) and guanidinoethyldisulfide (GED), which are iNOS inhibitors and reactive nitrogen scavenging compounds, on the development of experimental gingivitis in beagle dogs. METHODS: Fifteen female, 1-year-old beagles first completed a 2-week dose-escalation experiment during which a maximum tolerated dose was determined for MEG and GED gels. Thereafter, all animals were brought to optimal gingival health by mechanical scaling, followed by rigorous daily toothbrushing over a 4-week washout period. Experimental gingivitis was then induced, with cessation of plaque control and institution of a soft diet over 8 weeks. Beagles randomly received 0.3% MEG, 0.3% GED, or placebo (vehicle) gels, topically applied twice daily to premolar teeth. Gingival inflammation, bleeding tendency, and supragingival plaque were clinically measured at baseline and at 2, 3, 4, 6, and 8 weeks. Comparisons among groups and between group pairs (active versus placebo) were made using Kruskal-Wallis tests. RESULTS: From baseline to day 7, all groups expressed similar indices. Thereafter, significant and time-dependent increases in the plaque index (PI), gingival index (GI), and percentage of bleeding on probing (%BOP) were observed in placebo-treated beagles. Mean GI scores for beagles treated with GED or MEG gels remained at or below baseline levels for the entire treatment period. At weeks 2, 3, 4, and 8, GI scores were significantly lower for MEG and GED groups compared to the placebo group (P<0.05). In addition, MEG and GED gels significantly reduced gingival bleeding responses by 8 weeks (P<0.05). Although placebo-treated beagles demonstrated %BOP scores of 43% at week 8, GED- and MEG-treated beagles exhibited %BOP scores of 21% and 26%, respectively. Since no statistical difference among PI scores was noted for any of the time points, neither mercaptoalkylguanidine appeared to affect supragingival plaque levels. CONCLUSION: The data from this preclinical study indicate that mercaptoalkylguanidines, topically administered, may significantly reduce experimental gingivitis in the beagle dog.

Administration, Topical↗
PubMed2005

Prospective evaluation of the systemic inflammatory marker C-reactive protein in patients with end-stage periodontitis getting teeth replaced with dental implants: a pilot investigation.

OBJECTIVES: Serum C-reactive protein (CRP) has been shown to be a risk predictor for cardiovascular disease. Periodontal treatment reduces elevated CRP levels. The aim of this pilot investigation was to evaluate if dental implants placed after extractions in patients with end-stage periodontitis affect the serum CRP levels. MATERIAL AND METHODS: Serum CRP levels in 10 subjects with end-stage periodontitis were measured prior to tooth extraction and placement of dental implants, and at 3-month intervals for a year post-operatively. Univariate repeated measures analysis of variance was used to estimate and test the changes in CRP levels over time. RESULTS: Mean CRP levels decreased significantly following tooth extraction and replacement with dental implants from 3.45 to 1.55 mg/dl after 12 months (P < 0.01). Six-, 9-, and 12-month post-implant placement mean CRP values were statistically significantly different from the mean pre-operative CRP value (P < 0.01). CONCLUSIONS: The pilot data suggest that extraction of advanced periodontally involved teeth and their replacement with dental implants lead to a decrease in CRP levels, and dental implant placement does not change the lowered CRP levels over a 12-month period.

Aged↗
PubMed2003

Locally delivered minocycline microspheres for the treatment of periodontitis in smokers.

AIM: The aim of the present analysis of a larger phase 3 clinical trial was to evaluate the efficacy of 1 mg minocycline hydrochloride microencapsulated in 3 mg of resorbable polymer, subgingivally administered as an adjunct to scaling and root planing (SRP) in smokers with chronic periodontitis. MATERIAL AND METHODS: Two hundred and seventy-one patients who smoked were randomized to one of three treatment groups: (1) SRP alone, (2) SRP plus vehicle (polymer without minocycline) or (3) SRP plus minocycline microspheres. Full mouth SRP was performed for all groups at baseline, and vehicle or minocycline microspheres were administered to the appropriate patients at all periodontal pockets > or =5 mm at baseline, 3 and 6 months. Efficacy was evaluated over 9 months. RESULTS: Significantly greater pocket depth reductions with SRP plus adjunctive minocycline microsphere treatment were observed at 1, 6 and 9 months (p<0.05) versus control treatments. At 9 months, smokers treated with SRP plus minocycline microspheres exhibited a pocket depth reduction of 1.19 mm from baseline, as compared to 0.90 mm for smokers treated with SRP alone. The efficacy of adjunctive minocycline microspheres was consistent among all tested smoking subcohorts, including those based on gender, age and smoking exposures. CONCLUSION: These data indicate that treatment with SRP plus locally delivered minocycline microspheres is more effective than SRP alone in reducing pocket depths in smokers with periodontitis.

Administration, Topical↗
PubMed2002

A century of progress in understanding periodontal disease.

Throughout the 20th century, investigators and clinicians sought to discover the causes and trace the natural history of periodontal disease. Noteworthy progress has been made on several fronts. It was once believed that oral hygiene and age accounted predominantly for variances in the prevalence and severity of periodontal disease; now, a number of innate, acquired, and environmental risk factors have been identified. Light has been shed on the roles in periodontal disease pathogenesis of both specific bacteria and bacterial complexes and host immunoinflammatory responses. Insight into periodontal wound healing has fostered promising approaches to promoting regeneration of damaged periodontal structures. Finally, although theories of "focal infection" as a primary cause of systemic disease have been discredited, recent studies have confirmed the existence of an intimate connection between oral and systemic health. The progress made in understanding the nature of periodontal disease has been complemented by equally noteworthy therapeutic advances. The coupling of surgical and medical approaches to treatment ushers in a new era in the management of periodontal disease.

Disease↗