Biomedical subjects

Nadeem Y Karimbux

Publications and source records attributed to Nadeem Y Karimbux.

10 recordsLinked to original sources

PubMed2006

B and T lymphocytes are the primary sources of RANKL in the bone resorptive lesion of periodontal disease.

Receptor activator of nuclear factor-kappaB (RANKL)-mediated osteoclastogenesis plays a pivotal role in inflammatory bone resorption. The aim of this study was to identify the cellular source of RANKL in the bone resorptive lesions of periodontal disease. The concentrations of soluble RANKL, but not its decoy receptor osteoprotegerin, measured in diseased tissue homogenates were significantly higher in diseased gingival tissues than in healthy tissues. Double-color confocal microscopic analyses demonstrated less than 20% of both B cells and T cells expressing RANKL in healthy gingival tissues. By contrast, in the abundant mononuclear cells composed of 45% T cells, 50% B cells, and 5% monocytes in diseased gingival tissues, more than 50 and 90% of T cells and B cells, respectively, expressed RANKL. RANKL production by nonlymphoid cells was not distinctly identified. Lymphocytes isolated from gingival tissues of patients induced differentiation of mature osteoclast cells in a RANKL-dependent manner in vitro. However, similarly isolated peripheral blood B and T cells did not induce osteoclast differentiation, unless they were activated in vitro to express RANKL; emphasizing the osteoclastogenic potential of activated RANKL-expressing lymphocytes in periodontal disease tissue. These results suggest that activated T and B cells can be the cellular source of RANKL for bone resorption in periodontal diseased gingival tissue.

B-Lymphocytes↗

PubMed2006

Dental Admission Test scores and performance on NBDE Part I, revisited.

The purpose of this study was to examine the relationship between performance on the Dental Admission Test (DAT) and Part I of the National Board Dental Examination (NBDE Part I) for students at the Harvard School of Dental Medicine (HSDM). This study was a retrospective cohort study, examining HSDM students over an eight-year period. Data regarding DAT and NBDE Part I scores were obtained from the Office of the Registrar. Descriptive statistics were computed for all study variables. Multiple linear regression analyses were subsequently computed to examine the relationship between DAT subtest scores and performance on NBDE Part I subtests. Goodness of fit for the models was evaluated using the R-squared value. Statistically significant associations were those with p-value =0.05. Data were available for 244 students who matriculated at HSDM during the period of 1995-2002. DAT reading comprehension scores were statistically significantly associated with performance on all four subsections of the NBDE Part I. DAT general and organic chemistry scores were associated with performance on the microbiology and pathology subtest of NBDE Part I. Performance on the perceptual ability test was associated with performance on the dental anatomy and occlusion subtest. Performance on the DAT reading comprehension subtest was the most reliable predictor of performance on the NBDE Part I. However, the variability in NBDE Part I scores is not accounted for significantly by variability in DAT scores.

Boston↗

PubMed2005

Modulating the effects of diabetes on osseointegration with aminoguanidine and doxycycline.

BACKGROUND: The current knowledge of wound healing around implant surfaces is quite limited, particularly as it relates to the effects of systemic diseases such as diabetes. The purpose of our research is to histologically evaluate the effects of aminoguanidine and doxycycline in the modification of peri-implant wound healing around endosseous implants in diabetic rats. METHODS: Thirty-two Sprague-Dawley rats were randomly assigned to four different treatment groups. One group served as the non-diabetic control, while diabetes was induced in other groups. Titanium plasma-sprayed (TPS) implants were placed in the femora of each animal 2 weeks following diabetic induction. One group of diabetic rats was given aminoguanidine via intraperitoneal injection, and another given doxycycline via oral gavage for 28 days beginning on the day of implantation. The third group of diabetic rats received no medication (controls). All animals were sacrificed following 28 days of healing. RESULTS: The results were measured by marrow bone-to implant contact (MBIC) between the groups. Values for MBIC were greater for the non-diabetic control group than the diabetic control group (P < 0.001). Aminoguanidine-treated diabetic animals had a significantly greater MBIC than the diabetic control group (P < 0.01). Diabetic animals receiving doxycycline did not differ significantly from the diabetic control group (P > 0.05). CONCLUSIONS: The results of this study using a rat model con- firm previous reports that diabetes inhibits osseointegration, as defined by MBIC. In addition, this study demonstrates that the detrimental effects of diabetes on osseointegration can be modified using aminoguanidine systemically. However, systemic administration of doxycycline only slightly enhances osseointegration.

Analysis of Variance↗

PubMed2005

Maintenance of osseointegration utilizing insulin therapy in a diabetic rat model.

BACKGROUND: Normal wound healing processes have been shown to be altered in diabetes, and the effect of the diabetes on bone-to-implant contact (BIC) once osseointegration has been established is still unknown. The purpose of this study was to histologically evaluate the bone-to-implant contact in uncontrolled and insulin-controlled rats in which diabetes was induced following the establishment of osseointegration. METHODS: Thirty-two rats were assigned to eight different treatment groups of four each. Titanium plasma-sprayed (TPS) implants were placed in the femora of each animal, and allowed to osseointegrate for 28 days before diabetic induction. Daily insulin injections were given to four groups of rats and the other four groups received no insulin (uncontrolled). The rats were sacrificed at 1, 2, 3, and 4 months following diabetic induction. RESULTS: The results indicated that at 1, 2, 3, and 4 months, there was more BIC in the insulin-controlled groups compared to the uncontrolled groups. The differences were significantly greater at 2, 3, and 4 months (P < or =0.001). CONCLUSIONS: This study demonstrated that osseointegrated dental implants in insulin-controlled diabetic rats maintained bone-to-implant contacts over a 4-month period. However, boneto- implant contact appears to decrease with time in uncontrolled diabetic rats.

Animals↗

PubMed2004

Problem-based learning and research at the Harvard School of Dental Medicine: a ten-year follow-up.

Dental students at the Harvard School of Dental Medicine (HSDM) are required to pursue and complete research projects in order to obtain the doctor of dental medicine (D.M.D.) degree. The purpose of this study was to evaluate the effect of curriculum changes on a set of measurable outcomes related to research pursuits. This study was designed as a retrospective analysis of outcomes data from the period 1992-2002. The predictor variable was program format (non-PBL vs. PBL); the outcome variables were the percentage of students listed as authors on an IADR/AADR abstract during their tenure at HSDM and the percentage of students listed as first and/or presenting authors. Univariate statistics were computed for each class, and independent samples t-tests were used to compare the study groups with regard to our outcomes. For the majority of our outcomes, there was no statistically significant difference between the PBL and non-PBL groups, possibly due to sample size limitations. While the implementation of PBL at HSDM has not universally increased student productivity in research, it has not had an adverse effect either. It is possible that students in the PBL curriculum are nurturing other interests, such as community service, while retaining productivity in research.

Dental Research↗

PubMed2004

Academy: strengthening the educational mission in academic health centers.

A dental school in the modern academic health center often finds that its traditional mission of educating dentists has become more complex as a result of the increased emphasis placed on research and patient care. Although health care education clearly benefits from a rich environment including research and patient care, faculty often find themselves conflicted about their roles in the complex mix of activities in the health center. In order to support faculty in their educational activities, several schools have formed organizational structures with the specific purpose of providing financial and developmental assistance. This article describes a model for an organizational structure within the Harvard School of Dental Medicine designed to promote educational excellence and then describes two academies dedicated to promoting teaching quality at Harvard Medical School and at the University of California at San Francisco.

Academic Medical Centers↗

PubMed2003

Membrane type (MT) 1-matrix metalloproteinase (MMP) and MMP-2 expression in ligature-induced periodontitis in the rat.

BACKGROUND: Matrix metalloproteinases (MMPs) have been shown to be involved in the degradation of the extracellular matrix (ECM). In particular, MMP-2 and MMP-9 (gelatinase A and gelatinase B, respectively) have been identified as the predominant MMPs during periodontitis. Recent studies have indicated that a novel transmembrane MMP, mebrane-type 1 matrix metalloproteinase (MT1-MMP), can activate pro-MMP-2 in tumor metastasis. This study aims to elucidate the presence and localization of MT1-MMP and MMP-2 in periodontitis in a rat model. METHODS: In 2 groups of 40-day-old male Sprague-Dawley rats, periodontitis was initiated by ligating floss around maxillary second molars. A group of control animals were left untreated. Maxillary dentoalveolar segments were isolated after 7 and 21 days postinduction and were prepared for gross and radiographic analysis of bone loss and for histological analysis. Samples were also prepared for gel zymography to detect the presence of MMP-2, and for Northern blot analysis and in situ hybridization with MT1-MMP probes. RESULTS: MMP-2 expression increased at 21 days following ligature placement, in conjunction with MT1-MMP expression. MT1-MMP mRNA expression was observed in epithelial cells, fibroblasts, and in multinucleated cells in the periodontium. CONCLUSION: Our data suggest that MT1-MMP may play a role in extracellular matrix degradation during periodontitis, in concert with MMP-2 and other proteinases.

Animals↗

PubMed2003

Problem-based learning: effects on standard outcomes.

Dental students at the Harvard School of Dental Medicine (HSDM) participate fully in the first two years of the curriculum with the Harvard Medical School (HMS) while also taking parallel dental classes. HSDM students were first exposed to problem-based learning (PBL) in 1987 when the "New Pathway" curriculum was introduced at HMS in the first two years of the medical school curriculum (the HSDM courses remained traditional lecture-based classes). In 1994, HSDM incorporated PBL into the first, second, and third (clinical year) year dental courses, and the curriculum shifted from a five-year curriculum to a four-year curriculum. The purpose of this study was to evaluate the effect of PBL and program length on measurable outcomes for dental education: NBDE Part I scores, attrition and graduation rates, and percentage of graduates entering postdoctoral training programs. This study was designed as a retrospective analysis of outcomes data from 1980 to 2002. Univariate linear regressions were computed for each measure against each outcome. Subsequent bivariate regression analyses revealed that the implementation of PBL has markedly affected NBDE Part I scores, graduation rates, attrition rates, entrance into postdoctoral plans, and percentage of graduates entering GPR/AEGD programs, while program length has had an effect on graduation rates, attrition rates, entrance into postdoctoral programs, and percentage of graduates entering GPR/AEGD programs. The findings of this report suggest that the implementation of PBL combined with a change in program length has been successful for all outcomes measured and that PBL alone has contributed to the rise in NBDE Part I scores among HSDM graduates.

Boston↗

PubMed2002

Learning disabilities in dental education: trends, management, and concerns in U.S. dental schools.

The prevalence of learning disabilities (LD) in higher education has drawn significant attention at the undergraduate level. College freshmen reporting learning disabilities have increased significantly in the past twenty years. Although anecdotal evidence suggests an increase in the number of dental students with learning disabilities, nothing has been published regarding how dental education is affected by this general trend. The purpose of this study was to obtain information from U.S. dental school administrators regarding the incidence and prevalence of learning disabilities in dental education. We hypothesized that there has been an increase in diagnosed cases of learning disabilities in dental education. Following a pilot study to identify individuals responsible for working with students with learning disabilities in U.S. dental schools (response rate 91 percent, n = 49), a eighteen-item survey instrument was distributed to specific contact individuals (response rate 81 percent, n = 44). Mean cumulative incidence of diagnosed cases of learning disabilities was 0.3 percent; mean prevalence of identified diagnosed cases of LD 0.7 percent. Pearson analysis revealed a statistically significant weak positive correlation between mean prevalence and year, suggesting an increase in identified diagnosed cases of LD in U.S. dental schools over the past seven years (r = 0.24, p = 0.002). We conclude that the presence of learning disabilities in dental education is silent, pervasive, and deserves increased attention.

Education, Dental↗

PubMed2002

Tutoring in a problem-based curriculum: expert versus nonexpert.

Many studies have examined whether being an "expert" influences the success of a tutor in a problem-based learning curriculum. There are, however, no established standards by which to determine expertise. The purpose of this study was to examine whether students evaluate expert and nonexpert tutors comparably and to determine whether setting different standards to determine expertise influences the outcome of the above findings. Tutor evaluations, consisting of eight Likert-type questions completed by first-, second-, and third-year dental students, were analyzed. Tutors were ranked by the authorswithin three different categories of expertise based on the highest educational degree they had attained, familiarity with the specific subject matter, and previous problem-based learning (PBL) experience. Linear regression analyses were then performed between each category and student evaluation results. A statistically significant difference was found in the way students evaluated experts, but only when expertise was defined by the tutor's previous tutorial experience. The findings of this study underscore the importance of the retention of dental faculty with PBL experience in a PBL-based curriculum.

Analysis of Variance↗