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Biomedical subjects

Stephen T Chen

Publications and source records attributed to Stephen T Chen.

7 recordsLinked to original sources
PubMed2005

A prospective clinical study of bone augmentation techniques at immediate implants.

The efficacy of combinations of membranes and autogenous bone grafts at immediate implants were compared in a prospective study. Sixty-two consecutively treated patients each received an immediate implant for a single tooth replacement at a maxillary anterior or premolar site. Dimensions of the peri-implant defect at the implant collar were measured as follows: vertical defect height (VDH), horizontal defect depth (HDD) and horizontal defect width (HDW). Each implant randomly received one of five augmentation treatments and were submerged with connective tissue grafts: Group 1 (n=12)--expanded polytetrafluoroethylene membrane only, Group 2 (n=11)--resorbable polylactide/polyglycolide copolymer membrane only, Group 3 (n=13)--resorbable membrane and autogenous bone graft; Group 4 (n=14)--autogenous bone graft only, and Group 5 (n=12)--no membrane and no bone graft control. At re-entry, all groups showed significant reduction in VDH, HDD and HDW. Comparisons between groups showed no significant differences for VDH (mean 75.4%) and HDD (mean 77%) reduction. Significant differences were observed between groups for HDW reduction (range, 34.1-67.3%), with membrane-treated Groups 1, 2 and 3 showing the greatest reduction. In the presence of dehiscence defects of the labial plate, HDW reduction of 66.6% was achieved with membrane use compared with 37.7% without membranes. Over 50% more labial plate resorption occurred in the presence of a dehiscence defect irrespective of the augmentation treatment used. The results indicate that VDH and HDD reduction at defects adjacent to immediate implants may be achieved without the use of membranes and/or bone grafts.

Adult↗
PubMed2004

Immediate or early placement of implants following tooth extraction: review of biologic basis, clinical procedures, and outcomes.

PURPOSE: The aim of this article was to review the current literature with regard to survival and success rates, along with the clinical procedures and outcomes associated with immediate and delayed implant placement. MATERIALS AND METHODS: A MEDLINE search was conducted of studies published between 1990 and June 2003. Randomized and nonrandomized clinical trials, cohort studies, case-control studies, and case reports with a minimum of 10 cases were included. Studies reporting on success and survival rates were required to have follow-up periods of at least 12 months. RESULTS: Thirty-one articles were identified. Most were short-term reports and were not randomized with respect to timing of placement and augmentation methods used. All studies reported implant survival data; there were no reports on clinical success. Peri-implant defects had a high potential for healing by regeneration of bone, irrespective of healing protocol and bone augmentation method. Sites with horizontal defects (HD) of 2 mm or less healed by spontaneous bone fill when implants with rough surfaces were used. In the presence of HDs larger than 2 mm, or when socket walls were damaged, concomitant augmentation procedures with barrier membranes and bone grafts were required. Delayed implant placement allowed for resolution of local infection and an increase in the area and volume of soft tissue for flap adaptation. However, these advantages were diminished by simultaneous buccolingual ridge resorption and increased requirements for tissue augmentation. DISCUSSION: Immediate and delayed immediate implants appear to be predictable treatment modalities, with survival rates comparable to implants in healed ridges. Relatively few long-term studies were found. Successful clinical outcomes in terms of bone fill of the peri-implant defect were well established. However, there was a paucity of data on long-term success as measured by peri-implant tissue health, prosthesis stability, and esthetic outcomes. CONCLUSIONS: Short-term survival rates and clinical outcomes of immediate and delayed implants were similar and were comparable to those of implants placed in healed alveolar ridges.

Alveolar Ridge Augmentation↗
PubMed2003

Oral focal mucinosis: report of 15 cases and review of the literature.

AIMS: To describe 15 cases of oral focal mucinosis (OFM) and compare these to previously reported cases. METHODS: Cases diagnosed as OFM in the period 1981-2003-were reviewed. Clinical information provided at the time of submission of each specimen was retrieved and supplemented by additional clinical details provided by the respective clinician at the time of compilation of this paper. The literature was reviewed. RESULTS: OFM presented as an innocuous soft tissue swelling that may be either pedunculated or sessile. The gingiva was confirmed as the most common site for OFM, with a predominance of females affected. Microscopically, OFM is characterised by an area of myxoid tissue which is usually well-defined. The lesion is periodic acid-Schiff (PAS)-negative and alcian blue-positive, with pre-digestion with hyaluronidase preventing the alcian blue staining. As the differential diagnosis includes myxoid neural lesions, S100 staining is important in establishing the diagnosis, with cases of OFM being negative. CONCLUSIONS: The cause of OFM remains unknown. The cases presented in this paper bring OFM to the attention of anatomical pathologists when considering the differential diagnosis of myxoid lesions of the oral cavity.

Adolescent↗
PubMed2003

Delusional thoughts and regional frontal/temporal cortex metabolism in Alzheimer's disease.

OBJECTIVE: Delusional thoughts are common in patients with Alzheimer's disease and contribute prominently to morbidity. The pathophysiologic underpinnings for delusions in Alzheimer's disease are not well understood. In this study the authors examined the relationship between delusional thoughts and regional cortical metabolism in patients with Alzheimer's disease. METHOD: Twenty-five patients with probable Alzheimer's disease were included. None was taking psychotropic medication. Severity of delusions and other neuropsychiatric symptoms was assessed by using a semistructured interview and the Neurobehavioral Rating Scale just before the imaging procedure. [(18)F]Fluorodeoxyglucose positron emission tomography was used to measure resting cerebral glucose metabolic rates in the cortical lobes and in anatomically defined subregions of the frontal and temporal cortexes. RESULTS: A linear regression model, controlling for the effects of cognitive deficits, revealed a significant relationship between severity of delusional thought and the metabolic rates in three frontal regions: the right superior dorsolateral frontal cortex (Brodmann's area 8), the right inferior frontal pole (Brodmann's area 10), and the right lateral orbitofrontal region (Brodmann's area 47). Bivariate partial correlation analysis indicated that severity of delusions was associated with hypometabolism in additional prefrontal and anterior cingulate regions. Robust relationships with metabolism in regions of the temporal cortex were not apparent. CONCLUSIONS: Dysmetabolism in specific regions of the right prefrontal cortex may be associated with delusional thought in Alzheimer's disease. Delusions appear to reflect the pathophysiologic state of particular cortical regions. Activity across distributed neuronal networks and the specific content of delusional thoughts may modulate these relationships.

Aged↗
PubMed2002

Subcortical hyperintensities in Alzheimer's disease: associated clinical and metabolic findings.

The authors measured subcortical hyperintensities (SH) on magnetic resonance images (MRI) in 18 patients with probable Alzheimer's disease and examined the relationships of SH severity with cortical metabolic function and clinical symptoms. Severity of SH was not correlated with absolute metabolic rates in cortical lobes. However, anterior SH severity was inversely correlated with frontal/ parietal metabolic ratios after covarying for cognitive impairment. SH severity in some areas was associated with the severity of global neuropsychiatric symptoms, but marked effects on individual symptoms were not apparent. The small sample size and multiple variables limit conclusions that can be drawn. These preliminary findings indicate that subcortical MRI hyperintensities may play a role in the pathophysiology and clinical expression of Alzheimer's disease.

Aged↗
PubMed2002

Digital subtraction radiographic analysis of GTR in human intrabony defects.

The relationship between radiographic crestal alveolar bone mass and changes in clinical periodontal attachment level following guided tissue regeneration (GTR) was evaluated in this retrospective study. A total of 12 intrabony two- or three-walled defects and 12 adjacent nondiseased proximal sites in 10 nonsmoking adult subjects received subgingival debridement and GTR using resorbable (Resolut; five sites) or nonresorbable (Gore-Tex; seven sites) barrier membranes. At a mean of 48.8 months posttreatment, clinical periodontal attachment level alterations were measured, and crestal alveolar bone mass changes on digital subtraction radiographic images derived from serial periapical radiographs were analyzed to correct for between-film geometric and contrast density differences. Intrabony defects exhibited a mean clinical periodontal attachment level gain of 2.3 +/- 0.4 mm, in contrast to a mean loss of 0.5 +/- 0.2 mm in adjacent nondiseased interproximal sites. Digital subtraction radiography revealed an increase in crestal alveolar bone mass at all intrabony sites treated with GTR and a decrease in three of the adjacent nondiseased sites. Site-based analysis yielded an odds ratio of 36 (P < .001) for the association between radiographic increases in crestal alveolar bone mass and clinical periodontal attachment level gains of > or = 2 mm. These results suggest a strong concordance between digital subtraction radiographic assessments of crestal alveolar bone mass and clinical periodontal attachment level in evaluating the long-term effects of GTR at human interproximal intrabony defects.

Absorbable Implants↗