Biomedical subjects

Thomas C Hart

Publications and source records attributed to Thomas C Hart.

30 records · Page 2Linked to original sources

PubMed2004

Hereditary gingival fibromatosis associated with generalized aggressive periodontitis: a case report.

BACKGROUND: Hereditary gingival fibromatosis is a rare, genetically inherited overgrowth condition that is clinically characterized by a benign fibrous enlargement of maxillary and mandibular keratinized gingiva. A syndromic association between gingival fibromatosis and a wide variety of other genetically inherited disorders has been described. However, its coexistence with aggressive periodontitis has not been reported. METHODS: A 24-year-old African-American female, patient (proband X, [Px]) reported with a chief complaint of tooth mobility and gingival enlargement. Clinical examination revealed moderate to severe gingival overgrowth on both mandible and maxilla. Generalized attachment loss and mobility of the teeth were observed. Radiographic evaluation demonstrated severe alveolar bone loss. The patient was diagnosed with gingival fibromatosis and aggressive periodontitis based on the clinical and radiographic findings. Her brother (Bx) and her mother (Mx) were evaluated and diagnosed with gingival fibromatosis suggesting that this is a dominant trait in the family and gingival fibromatosis might be of hereditary origin. In addition, the brother also exhibited localized aggressive periodontitis. Medical history revealed no other systemic or local contributory factors associated with the oral findings in any of the subjects. RESULTS: Surgical therapy included internal bevel gingivectomy combined with open flap debridement procedures for Px and Bx. Only internal bevel gingivectomy was performed for Mx since there was mild bone resorption and no intrabony defects. At the time of surgery, gingival biopsies were obtained and fixed in 4% paraformaldehyde. Multiple serial sections were stained with hematoxylin and eosin. Microscopic evaluation of the gingival specimens revealed large parallel collagen bundles associated with scarce fibroblasts in the connective tissue. The collagen bundles reached into the subepithelial connective tissue where elongated rete-pegs were also observed. Following the completion of the treatment, no signs of recurrence or bone resorption were observed over 2-year follow-up. CONCLUSIONS: This is the first report of hereditary gingival fibromatosis associated with aggressive periodontitis. Combined treatment comprising removal of fibrotic gingival tissue and traditional flap surgery for the elimination of intrabony defects represents a unique treatment approach in periodontal therapy. Two-year follow-up revealed that both the gingival overgrowth and the destructive lesions were successfully treated.

Adult↗

PubMed2004

Status of genetics education in U.S. dental schools.

Genomics research is rapidly increasing our understanding of the genetic basis of normal and abnormal growth, development, and disease. Genetic information and technologies are also being applied to develop new diagnostic and treatment strategies. Many diseases with dental, oral, and craniofacial manifestations have a genetic basis. Effective clinical application of genomics to oral medicine will depend on the education of health care professionals, the general public, and policymakers. Dentists must understand genetics to provide accurate information to patients and be able to discuss benefits and limitations of the biological, clinical, and ethical issues related to genomic-based health care. Genetics education in dental schools will significantly impact the integration of genetics into oral medicine. Fifty-three U.S. dental schools completed a survey in 2001 to assess the status of genetics curricula in dental schools in the United States. Ninety-four percent of schools did not require genetics education for entry to dental school, and a formal genetics course was conducted in only eight of the fifty-three schools (15 percent). The genetics education currently offered to undergraduate dental students is not standardized, and the content varies considerably among schools. These findings suggest more emphasis on genetics education is needed in U.S. dental schools.

Curriculum↗

PubMed2003

Renal manifestations of a mutation in the uromodulin (Tamm Horsfall protein) gene.

BACKGROUND: Uromodulin (Tamm Horsfall glycoprotein) is the most abundant protein found in normal human urine. Its function has yet to be determined. Identifying mutations in the uromodulin gene may be helpful in understanding the function of uromodulin. There has been 1 report of 4 families suffering from mutations in the uromodulin gene, resulting in the autosomal dominant transmission of hypouricosuric hyperuricemia and chronic renal failure. This case report describes another family with similar clinical manifestations. METHODS: A family was identified with clinical characteristics of hypouricosuric hyperuricemia and renal failure occurring in a mother and daughter. Clinical characteristics were identified, and laboratory studies were obtained in the proband and the proband's daughter. A genetic analysis was performed to evaluate for mutations in the uromodulin gene. RESULTS: The proband suffered from hyperuricemia at an early age and progressive renal failure with end-stage renal disease developing at age 49 years. The proband's daughter suffered from hyperuricemia, a reduced fractional excretion of uric acid, and mild renal insufficiency. A g.2105G > A mutation in exon 4 of the uromodulin gene resulting in a substitution of tyrosine for cysteine was identified in both the proband and the proband's daughter. The clinical characteristics were similar to those of other patients suffering from uromodulin mutations and to those of patients suffering from medullary cystic kidney disease type 2 and familial juvenile hyperuricemic nephropathy. CONCLUSION: Uromodulin associated kidney disease results in hyperuricemia and renal failure. The specific uromodulin mutation found in this family is consistent with the hypothesis that mutations disrupt highly conserved cysteine residues in the uromodulin protein. Potential mechanisms for these pathologic changes are discussed. The authors would appreciate referral of other families for screening for mutations.

Amino Acid Substitution↗

PubMed2003

Exclusion of candidate genes in two families with autosomal dominant hypocalcified amelogenesis imperfecta.

The amelogenesis imperfectas (AI) are a group of hereditary enamel defects characterized by clinical and genetic diversity. The most common AI types are inherited as autosomal traits. Three mutations of the enamelin (ENAM) gene have been found in cases of autosomal dominant hypoplastic AI. The gene(s) responsible for hypocalcified forms of AI have not been identified, although a number of autosomal genes have been proposed as candidates for AI based on their expression by ameloblasts, including ameloblastin and enamelin (chromosome 4q13.3), tuftelin (chromosome 1q21), enamelysin (chromosome 11q22.3-q23) and kallikrein 4 (chromosome 19q13.3-q13.4). To localize the gene(s) responsible for autosomal dominant hypocalcified AI, we evaluated support for/against linkage of AI to genetic markers spanning five AI candidate genes in two extended families. Our data excluded all proposed candidate gene regions as causal for autosomal dominant hypocalcified AI in these families. These linkage findings provide further evidence for genetic heterogeneity among families with autosomal dominant AI and indicate that, at least, some forms of autosomal dominant hypocalcified AI are not caused by a gene in the five most commonly reported AI candidate genes.

Amelogenesis Imperfecta↗

PubMed2003

Clinical characterization of a family with a mutation in the uromodulin (Tamm-Horsfall glycoprotein) gene.

BACKGROUND: We have recently identified a mutation in the uromodulin gene in a large family affected with hyperuricemia, gout, and renal failure. The purpose of this investigation is to provide a comprehensive characterization of the clinical findings of this syndrome in family members who had a mutation in the uromodulin gene. METHODS: An extended family suffering from hyperuricemia and gout was identified by a local practitioner. After consent was obtained, patients provided a directed clinical history and blood and urine specimens for chemical and genetic testing. All family members were tested for the presence of uromodulin gene mutations by direct DNA sequence analysis. The clinical and biochemical characteristics of family members carrying the affected mutation were then investigated. RESULTS: Thirty-nine family members were found to have an exon 5 uromodulin gene mutation (g.1966 1922 del), and 29 unaffected family members were identified. The cardinal clinical features in individuals with the uromodulin mutation included hyperuricemia, decreased fractional excretion of uric acid, and chronic interstitial renal disease leading to end-stage renal disease (ESRD) in the fifth through seventh decade. Women did not always develop hyperuricemia or gout, but still developed progressive chronic renal failure. CONCLUSION: Mutation of the uromodulin gene resulted in hyperuricemia, reduced fractional excretion of uric acid, and renal failure. Genetic testing will be required to definitively identify individuals suffering from this condition. We are interested in studying other families that may suffer from this condition and would appreciate any such referrals.

Adolescent↗

PubMed2003

Topically applied minocycline microspheres: why it works.

This article presents the results of a single-arm, open-label, multicenter clinical trial of the topical use of sustained-release minocycline hydrochloride (HCl) microspheres as an adjunct to scaling and root planing. The objective of this study was to evaluate the long-term safety and efficacy of the subgingival application of resorbable minocycline microspheres as an adjunct to scaling and root planing in the treatment of chronic periodontitis. The primary outcome measures were the reduction in probing pocket depth at 9- and 12-month evaluations, and the percent of bleeding upon probing. A total of 173 patients with moderate-to-severe chronic periodontitis were enrolled in this multicenter clinical trial. All patients received full-mouth scaling and root planing plus minocycline microspheres in all periodontal pockets that probed > or = 5 mm. All sites treated at baseline and any new sites > or = 5 mm again received minocycline microspheres at 3- and 6-month follow-up appointments with no further scaling and root planing. Significant improvements in all clinical parameters measured were found at all time points (1, 3, 6, 9 and 12 months). The product was found to be well-tolerated by patients, safe, and easy to deliver. Scaling and root planing with the topical application of minocycline microspheres appeared to give better results than would have been expected with scaling and root planing alone.

Absorbable Implants↗

PubMed2003

Genetics in dental practice: social and ethical issues surrounding genetic testing.

It is evident that human genetic variation is associated with many if not all human diseases including the more prevalent chronic diseases. As a result, genetics is becoming integrated into health care in all medical specialties, including oral medicine and its specialties. At the level of public health, genetic information will become increasingly important in research, policy, and program development. As application of genome technologies moves from the research laboratory to the clinical setting, a complex array of challenges will face dental clinicians in their efforts to use genetic information to improve health care and prevent disease on an individual, family, and community level. The broader social, ethical, and legal implications raised by the clinical use of genomic information have not received the same attention as did recent gene identification aspects of the Human Genome Project. The goal of this review is to foster attention and dialogue within the dental community of the ethical and social issues emerging from the availability of genetic information. Specific areas addressed include genetic testing, confidentiality, discrimination, informed consent, risk communication, and professional education.

Confidentiality↗

PubMed2002

A mutation in the SOS1 gene causes hereditary gingival fibromatosis type 1.

Hereditary gingival fibromatosis (HGF) is a rare, autosomal dominant form of gingival overgrowth. Affected individuals have a benign, slowly progressive, nonhemorrhagic, fibrous enlargement of the oral masticatory mucosa. Genetic loci for autosomal dominant forms of HGF have been localized to chromosome 2p21-p22 (HGF1) and chromosome 5q13-q22 (HGF2). To identify the gene responsible for HGF1, we extended genetic linkage studies to refine the chromosome 2p21-p22 candidate interval to approximately 2.3 Mb. Development of an integrated physical and genetic map of the interval identified 16 genes. Sequencing of these genes, in affected and unaffected HGF1 family members, identified a mutation in the Son of sevenless-1 (SOS1) gene in affected individuals. In this report, we describe the genomic structure of the SOS1 gene and present evidence that insertion of a cytosine between nucleotides 126,142 and 126,143 in codon 1083 of the SOS1 gene is responsible for HGF1. This insertion mutation, which segregates in a dominant manner over four generations, introduces a frameshift and creates a premature stop codon, abolishing four functionally important proline-rich SH3 binding domains normally present in the carboxyl-terminal region of the SOS1 protein. The resultant protein chimera contains the wild-type SOS1 protein for the N-terminal amino acids 1-1083 fused to a novel 22-amino acid carboxyl terminus. Similar SOS1 deletion constructs are functional in animal models, and a transgenic mouse construct with a comparable SOS1 chimera produces a phenotype with skin hypertrophy. Clarification of the functional role of this SOS1 mutant has implications for understanding other forms of gingival fibromatosis and corrective gingival-tissue management.

Amino Acid Sequence↗

PubMed2002

Demonstration of altered splicing with the IVS3-1G --> a mutation of cathepsin C.

Papillon-Lefèvre syndrome is an autosomal recessive palmoplantar keratoderma caused by cathepsin C gene mutations. We present the second family segregating the IVS3-1G --> A mutation and demonstrate for the first time that altered splicing and decreased enzymatic activity occur. RNA analysis revealed two species in carriers, corresponding to wild-type and mutant transcripts, and only the mutant transcript in affected individuals. Sequencing of the mutant transcript revealed that it lacked exon 3, resulting in a frameshift and introduction of a premature termination codon.

Alternative Splicing↗

PubMed2002

Clinical utility of a genetic susceptibility test for severe chronic periodontitis: a critical evaluation.

BACKGROUND: A genetic susceptibility test for severe chronic periodontitis is now commercially available. It detects the simultaneous presence of a specific form of two interleukin genes--allele 2 at the IL1A+4845 and IL1B+3954 loci. Patients are referred to as being "genotype-positive" if both of these alleles are present. A fundamental premise of the test is that a combination of these alleles is responsible for increased secretion of IL-beta, which results in a hyperinflammatory response to a bacterial challenge, thereby predisposing a person to develop severe chronic periodontitis. TYPES OF STUDIES REVIEWED: The authors reviewed controlled clinical trials that assessed the association between specific genotypes and the patient's susceptibility to increased bleeding on probing, periodontitis and loss of teeth or dental implants. RESULTS: The relationship between specific IL-1 genotypes and the level of IL-1beta in the gingival crevicular fluid is unclear. Similarly, the ability of the genetic susceptibility test to forecast which patients will develop increased bleeding on probing, periodontitis, or loss of teeth or dental implants is ambiguous. CLINICAL IMPLICATIONS: Additional prospective clinical trials are needed to determine the risk of developing periodontitis or peri-implantitis when allele 2 at the IL1A+4845 and IL1B+3954 loci is present. Therefore, it is unclear how results of the genetic susceptibility test can be used to alter patients' periodontal maintenance schedules or to change treatment regimens in periodontally symptomatic or asymptomatic patients.

Alleles↗

PubMed2002

A critical assessment of interleukin-1 (IL-1) genotyping when used in a genetic susceptibility test for severe chronic periodontitis.

BACKGROUND: This review addresses the ability of a commercially available genetic susceptibility test to determine the risk of developing severe chronic periodontitis. The test is used to detect the simultaneous occurrence of allele 2 at the IL-1A+4845 and IL-1B+3954 loci. If both of these polymorphisms are present, patients are referred to as being genotype-positive and considered predisposed to becoming afflicted with severe chronic periodontitis. A basic premise of this test is the assumption that individuals who are genotype-positive produce increased amounts of IL-beta in response to microbial lipopolysaccharides, which allegedly predisposes them to an exaggerated inflammatory response and an increased incidence of chronic periodontitis. METHODS: Controlled clinical trials were selected that evaluated the ability of the genetic test to predict which patients were susceptible to bleeding upon probing, periodontitis, peri-implantitis, and tooth loss. RESULTS: Comparison of results from test (genotype-positive) and control groups (genotype-negative) revealed that there is ambiguity with regard to predicting which patients will manifest elevated sub-gingival levels of IL-beta. Similarly, it is questionable if the test is able to forecast which individuals will demonstrate an increased occurrence of bleeding upon probing, diminished clinical attachment, decreased osseous support, or loss of teeth. CONCLUSIONS: There are many unanswered questions concerning the utility of detecting allele 2 at the IL-1A+4845 and IL-IB+3954 loci to foretell which patients will develop severe chronic periodontitis. Therefore, clinicians must cautiously interpret results obtained with the commercially available genetic susceptibility test before they alter maintenance schedules or treatment regimens of symptomatic or asymptomatic patients.

Alleles↗

PubMed2002

Genetic testing considerations for oral medicine.

The availability and integration of genetic information into our understanding of normal and abnormal growth and development are driving important changes in health care. These changes have fostered the hope that the availability of genetic information will promote a better understanding of disease etiology and permit early, even pre-symptomatic diagnosis and preventative intervention to avoid disease onset. Expectations for this proactive health care approach are fueled by the technological and scientific advances that have fundamentally changed how we perceive human diseases. Among the clinical applications of this information, genetic testing applications are likely to expand significantly and may broadly impact the clinical practice of dentistry. In this changing environment, it is vital that dental care providers, policymakers, and consumers become aware of important issues related to genetic testing and the incorporation of genetic information into the diagnosis and treatment of common diseases that involve the oral cavity. We must also guard against unrealistic expectations and calls for genetic tests that are not valid. To realize the promise of this new molecular genetics, we must understand the possibilities and responsibly incorporate newly emergent technologies into the evolving discipline of dentistry. This paper overviews many of the important issues that need to be considered in the application of genetic testing to oral medicine.

Advisory Committees↗