Search PubMed⌕ Search

Biomedical subjects

R Dunford

Publications and source records attributed to R Dunford.

At least 19 recordsLinked to original sources
PubMed2000

Loss of heterozygosity in spontaneous and X-ray-induced intestinal tumors arising in F1 hybrid min mice: evidence for sequential loss of APC(+) and Dpc4 in tumor development.

Min (multiple intestinal neoplasia) mice carry a mutant allele of the murine Apc (adenomatous polyposis coli) locus and are predisposed to intestinal adenoma formation in the intestinal tract. Early studies have shown complete loss of function of Apc by whole chromosome loss on the tumor-sensitive C57BL/6J genetic background and in AKR x B6 F1 hybrids. Gamma-radiation-induced chromosomal losses focus the critical region on wt Apc, but because of the limited number of polymorphic markers used, no other critical regions of loss on chromosome 18 were identified. Using intestinal tumors arising spontaneously and induced by X-rays in CBA/H x C57BL/6J F1 hybrid mice and high-resolution microsatellite loss of heterozygosity (LOH) techniques, we provide mapping data for wt Apc loss, which confirms and extends earlier observations. In addition, high-frequency loss events at the Dpc4 locus were found in both spontaneous and radiation-induced tumors. These data identified LOH of Dpc4 as a critical secondary event following complete functional loss of Apc. LOH across the Trp53 genomic region of chromosome 11 was not observed. No LOH was recorded for the Mom1 candidate gene Pla2g2a or for 9 out of 10 polymorphic markers from the Mom1 genomic region on murine chromosome 4. One marker mapping distal to Pla2g2a showed LOH in a small minority of spontaneous tumors. These data support the contention that Mom1 does not act as a classical tumor suppressor. Overall, our data indicates a significant role for Dpc4 mutation in intestinal tumor progression in the mouse and provides further evidence for the importance of interstitial chromosome losses in radiation tumorigenesis.

Animals↗
PubMed2000

Outcome variables in periodontal research: means and threshold-based site changes.

BACKGROUND: The exclusive use of mean measurements in periodontal research might at times be misleading, as changes in different sites in the same individual might nullify each other. The purpose of the present study was to compare disease progression and response to periodontal therapy using both individual site activity with thresholds and mean patient changes. METHODS: Seventy-nine (79) subjects with established periodontitis were monitored for 1 year (no treatment [NTx] group); 108 subjects who received scaling, root planing, and quarterly prophylaxis were observed in a similar time interval (treatment [Tx] group). Probing depth (PD), attachment level (AL) and alveolar crestal height (ACH) were measured at baseline and 1 year using pressure-sensitive probes and computer-assisted image analysis of radiographs. RESULTS: Mean reduction in PD (0.50 mm) was observed in the Tx group compared to a small increase (-0.04 mm) in the NTx group (P= 0.0001). Treatment resulted in mean AL gain (0.44 mm) compared to net AL loss (-0.21 mm) in the NTx group (P= 0.0001). Subjects in the Tx group had twice as many sites with AL gain (beyond the threshold) compared to NTx subjects (16.64+/-1.07% versus 8.11+/-0.68%) which was highly significant (P = 0.0001, Student t test). Similarly, although in the opposite direction, percentage of sites with AL loss beyond threshold was 6.21+/-0.47% (Tx group) and 14.02+/-1.15% (NTx group) which was also highly significant (P = 0.0001, Student t test). Change in ACH was minimal for the Tx group (-0.07+/-0.03 mm) while NTx subjects experienced greater bone loss throughout the year (-0.16+/-0.02 mm); percentage of sites with ACH loss was similar for both groups, while the Tx group had 3 times the number of sites with ACH gain (11.76% versus 3.42%), suggesting that the reduction in mean bone loss in the Tx group did not result from a reduction in losing sites, but rather from an increase in gaining sites. The use of both means and binary data seems to supplement the information regarding the nature and mechanism of disease progression and arrest. CONCLUSIONS: The characteristics of periodontal disease with its multifactorial patient, local, and site-related etiology support the use of both mean and site-based changes in clinical studies of periodontal disease and treatment.

Adult↗
PubMed2000

The relationship between bone mineral density and periodontitis in postmenopausal women.

BACKGROUND: Systemic bone loss has been proposed as a risk factor for periodontal disease; however, the relationship between these two diseases is still not clear. The objective of this study was to assess the relationship between systemic bone mineral density and periodontal disease, controlling for known confounders. METHODS: The study population included 70 postmenopausal Caucasian women aged 51 to 78 (mean +/- SD: 62.10 +/- 7.1 years). Skeletal bone mineral density (BMD) was assessed by dual energy x-ray absorptiometry (DXA) at the neck, trochanter, intertrochanter, Ward's triangle, and total regions of the femur, and from the anterior-posterior view of the lumbar spine. Periodontal disease severity was represented by clinical attachment loss (CAL) and interproximal alveolar bone loss (ABL). Other measures of periodontal status included probing depth (PD), supragingival plaque, gingival bleeding on probing, and calculus. DXA and oral examinations were performed by calibrated examiners. Partial correlation coefficients (r) were obtained from multiple linear regression analysis adjusting for age, age at menopause, estrogen supplementation, cigarette smoking, body mass index, and supragingival plaque. RESULTS: Mean ABL was significantly correlated with BMD of the trochanter (r =- 0.27), Ward's triangle (r = -0.26), and total regions of the femur (r = -0.25). Mean CAL appeared to be related to BMD consistently at all regions of the skeleton, although the association did not reach statistical significance. CONCLUSIONS: We can conclude that skeletal BMD is related to interproximal alveolar bone loss and, to a lesser extent, to clinical attachment loss, implicating postmenopausal osteopenia as a risk indicator for periodontal disease in postmenopausal Caucasian women.

Absorptiometry, Photon↗
PubMed1999

Longitudinal study of predictive factors for periodontal disease and tooth loss.

Longitudinal assessment of risk factors for periodontal disease is necessary to provide evidence that a putative risk factor or risk indicator is a true risk factor. The purpose of the present study was to explore longitudinally a variety of markers as possible periodontal risk factors in subjects with little or no periodontal disease at baseline. 415 subjects with mild or little periodontal disease were examined: medical and dental history; socioeconomic profile, clinical measurements, microbial samples and radiographic assessment of bone height were performed at baseline, and at a follow-up examination 2 to 5 years later. Mean probing pocket depth (PPD) at baseline was 1.99+/-0.37 mm while mean overall change was 0.1 mm which amounts to an annual rate of 0.04 mm. Overall mean clinical attachment level (1.75+/-0.6 mm) at baseline resulted in mean attachment change of 0.28 mm (0.12 mm annually). Alveolar crestal height (ACH) at baseline (mean 2.05+/-0.85 mm) resulting in a mean net loss of 0.1 mm. Approximately 10% of all sites presented for the second visit with attachment loss exceeding the threshold (4.4% annually), while only 2.2% of all sites exhibited attachment gain (0.88% annually). Older individuals exhibited greater mean bone loss but the least amount of attachment loss. Current smokers exhibited greater disease progression compared to non-smokers. Tooth morbidity (0.17 teeth/patient/year) was associated with greater baseline CAL and ACH loss, and an assortment of systemic conditions. Subjects who harbored Bacteroides forsythus (Bf) at baseline had greater loss in ACH; likewise, these subjects experienced greater proportions of losing sites and twice as much tooth mortality compared to Bf-negative patients. Baseline clinical parameters correlated strongly with the outcome, i.e., subjects with deeper mean pocket depth at baseline exhibited greater increase in pocket depth overtime; while subjects with greater attachment loss at baseline exhibited greater attachment loss between the 1st and 2nd visits.

Adult↗
PubMed1999

Molecular mapping of chromosome 2 deletions in murine radiation-induced AML localizes a putative tumor suppressor gene to a 1.0 cM region homologous to human chromosome segment 11p11-12.

Radiation-induced acute myeloid leukemias (AMLs) in the mouse are characterized by chromosome 2 deletions. Previous studies showed that a minimal deleted region (mdr) of approximately 6.5 cM is lost from one homologue in chromosome 2-deleted AMLs. An AML tumor suppressor gene is proposed to map within this mdr. In this study, we refine the mdr to a I cM interval between markers D2Mit126 and D2Mit185 by microsatellite analysis of 21 primary radiation-induced F I AMLs. The construction of a partial yeast artificial chromosome (YAC) contig spanning the mdr and the location of six known genes indicated that the 1 cM mdr is homologous to human 11p11-12, a region implicated in some human AMLs. Screening of five cell lines derived from primary radiation-induced AMLs for homozygous loss of microsatellites and genes mapping within the mdr revealed loss of both copies of the hemopoietic tissue-specific transcription factor Sfpi1(PU.1/Spi1) in one cell line. Studies of primary and F1 AMLs failed to implicate Sfpi1 as the AML tumor suppressor gene. YAC contig construction, together with data suggesting that the critical gene flanks Sfpi1, represents significant progress toward identifying an AML tumor suppressor gene.

Animals↗
PubMed1998

Radiographic and clinical responses to periodontal therapy.

Mechanical periodontal therapy is widely used for a variety of periodontal conditions. While the clinical efficacy of this treatment has been validated, the radiographic response has not been studied in depth. The purpose of the present study was to examine the clinical and radiographic response to mechanical periodontal therapy, and assess the factors associated with these changes. One hundred and eight patients, with established periodontitis, received oral hygiene instruction and mechanical periodontal therapy for a period of 4 to 5 weeks. Scheduled maintenance visits were performed at 3, 6, 9, and 15 months. Probing depth (PD) and attachment level (AL) measurements were performed at baseline, and at 3 and 15 months. Intraoral radiographs were taken at baseline and 12 to 15 months postsurgery using a Rinn alignment system. Alveolar crestal height (ACH) measurements were performed on a pair of digitized images of the previously taken radiographs. An overall mean of patients' changes for PD, AL, and ACH was initially computed. Active sites (gainers and losers) were determined using a threshold method, and expressed as patient's percentage of active sites (number of active sites of the total sites measured in each patient). Mean overall probing reduction and AL gain was 0.5 mm and 0.44 mm, respectively. Of all sites measured, 16.6% exhibited AL gain, while only 6.2% of all sites exhibited AL loss. Mean overall change in ACH was -0.07 mm, of which 11.8% of all sites exhibited ACH gain, while 15.1% exhibited loss beyond the threshold. Non-smokers presented no change in bone loss, while smokers continued to lose bone at an annual rate of 0.17 mm, despite treatment (P <0.005). Likewise, the average percent of sites per patients showing attachment gain beyond the threshold were much greater in non-smokers (13.9%) compared to 9.0% in smokers (P <0.01). Mean probing reduction was 50% greater among non-smokers (0.6 mm) when compared to smokers (0.4 mm), which was also statistically significant (P <0.05). A positive and significant correlation was established between the percentage of sites with AL gain and sites with ACH gain (Rho =0.40; P=0.0001). It is suggested that monitoring sites for AL and ACH gain expressed as changes beyond a selective threshold is an important outcome variable in treatment studies.

Adult↗
PubMed1997

Chemical oxidation and DNA damage catalysed by inorganic sunscreen ingredients.

Titanium dioxide (TiO2) has been noted (US Federal Register, 43FR38206, 25 August 1978) to be a safe physical sunscreen because it reflects and scatters UVB and UVA in sunlight. However, TiO2 absorbs about 70% of incident UV, and in aqueous environments this leads to the generation of hydroxyl radicals which can initiate oxidations. Using chemical methods, we show that all sunscreen TiO2 samples tested catalyse the photo-oxidation of a representative organic substrate (phenol). We also show that sunlight-illuminated TiO2 catalyses DNA damage both in vitro and in human cells. These results may be relevant to the overall effects of sunscreens.

Catalase↗
PubMed1997

Longitudinal study of prognostic factors in established periodontitis patients.

Numerous indicators for disease progression have been described in the last decade. The purpose of this study was to examine, longitudinally, a large battery of clinical, microbiological, and immunological indicators, to try to determine whether the presence of one or a combination of these parameters at baseline, would correlate positively with increased attachment and or bone loss (true prognostic factors). Following initial screening, 79 patients with established periodontitis were monitored longitudinally for one year. Whole mouth clinical measurements, plaque gingival and calculus indices, together with pocket depth and attachment level measurements, were repeated every three months. Full mouth radiographic survey, performed at baseline and 12 months, served to determine changes in crestal bone height using an image enhancement technique. Subgingival plaque samples were taken at baseline and every 3 months. Immunofluorescence assays were performed for the a battery of target microorganisms. Serum and GCF samples for IgG subclasses analysis were obtained at each visit and assayed using ELISA techniques. Likewise blood, samples were also drawn at each visit for a quantitative analysis of serum cotinine level. The overall mean attachment loss (AL) and bone loss (BL) were almost identical (0.159 mm and 0.164 mm, respectively). Individual patients variation was large (-0.733 to +1.004 mm). An overall 6.89% of sites were active; individual patients' means ranged from 0-28.9%. Mean pocket depth (PD) showed minimal change over the study period (-0.033 mm) thus suggesting that most if not all the AL was accompained by concomitant gingival recession. Smokers exhibited greater AL and radiographic BL compared to non-smokers. Likewise, patients' cotinine level showed direct correlation with outcomes of progressive periodontal breakdown. Past severity of periodontal involvement, as reflected in the patients baseline PD, AL and crestal bone height, showed good correlation with longitudinal changes in the periodontium. This correlation was higher for crestal BL as the outcome variable, while somewhat smaller for change in AL as the outcome variable. Bacteroides forsythus (Bf.), Prevotella intermedia (Pi.) and Porphyromonas gingivalis (Pg.) were frequently found in these patients. The presence of these microorganisms at baseline was associated with further disease progression. Subjects with mean baseline pocket depth equal or greater than 3.2 mm were at greater risk for future bone loss 1 year later (O.R. 2.97; C.I. 1.02-8.70). Smokers were at significantly greater risk for further attachment loss when compared to non-smokers (O.R. 5.41; C.I. 1.50-19.5). Subjects that harbored B. forsythus at baseline, were at seven times greater risk for increased pocket depth (O.R. 7.84; C.I.1.74-35.3). In conclusion, past periodontal destruction, smoking habits, Bf., Pg., & Pi. are prognostic factors for further periodontal breakdown. When designing clinical trials, or when evaluating epidemiological data, it is most important to balance for these factors. Also, treatment strategies should attempt to eliminate or modify these factors.

Adult↗
PubMed1997

The relationship between radiographic and clinical changes in the periodontium.

Change in clinical attachment level (CAL) and radiographic change in crestal bone height are often used to assess periodontal breakdown and disease progression. These two variables are also used to monitor the effect of treatment. The purpose of the present longitudinal study was to evaluate the correlation between changes in CAL and alveolar bone loss. Following initial screening, 79 subjects with established periodontitis were monitored quarterly for 1 yr, using a pressure-sensitive automated probe. CAL and relative attachment level (RAL) were recorded at 6 sites for each tooth. Radiographs were obtained at baseline and 1 yr. Crestal bone changes were determined using an image enhancement technique. Mean change in attachment level was 0.16 mm. Similarly, mean proximal bone loss measured radiographically was 0.16 mm. In 6.9% of all the sites, and 13.7% of all pooled interproximal sites, AL loss was in excess of the threshold defined as 2 s.d. of repeated measurements (mean 1.54 mm). Similar percentages of sites (12.9%) had radiographic evidence of proximal bone loss exceeding the threshold (0.55-1.08 mm). A site-based analysis of active sites revealed an overall poor correlation between the 2 variables (kappa value = 0.03) which was the result of a very poor sensitivity (0.16) despite a relatively good specificity (0.81). A patient-based comparison of clinical and radiographical changes revealed an overall kappa value of 0.08, with sensitivity and specificity of 0.51 and 0.56, respectively. However, baseline CAL and crestal bone height showed good correlation (r = 0.73; p = 0.0001). It is suggested that changes in CAL and radiographic bone level progress somewhat independently. Over a short-term period of time they might not follow the same course; however, in the long term, these differences seem to level off. For longitudinal monitoring of disease progression and response to therapy both methods may be needed; while for cross-sectional evaluation and long-term prospective studies, either variable may be used alone.

Adult↗
PubMed1996

Purification and properties of four phosphoenolpyruvate carboxylase isoforms from the green alga Selenastrum minutum: evidence that association of the 102-kDa catalytic subunit with unrelated polypeptides may modify the physical and kinetic properties of the enzyme.

Four isoforms of phosphoenolpyruvate carboxylase (PEPC1, PEPC2, PEPC3, PEPC4) have been purified from the green alga Selenastrum minutum. PEPC1 is a homotetramer with a subunit M(r) of 102 kDa. PEPC2, PEPC3, and PEPC4 have respective native M(r)S of approximately 984, 1186, and 1590 kDa. SDS/PAGE analysis revealed that the latter three isoforms contain polypeptides having M(r)S of 102, 73, 70, 65, and 61 kDa. Immunoblot analyses and CNBr cleavage patterns suggest that the 102-kDa polypeptide present in all four isoforms is the same PEPC catalytic subunit. Our data suggest that the three high M(r)S PEPC isoforms are heteromeric protein complexes consisting of the 102-kDa PEPC1 catalytic subunit and immunologically unrelated polypeptides. Attempts to measure other enzyme activities associated with the protein complexes gave negative results. However, PEPC1 had immunological, physical, and kinetic properties very different from those of the larger M(r) PEPC isoforms: (i) the anti-PEPC1 immune-serum was relatively inefficient for immunoprecipitating PEPC2, PEPC3, or PEPC4; (ii) immune-serum raised against a mixture of PEPC2, PEPC3, and PEPC4 had relatively weak immunoprecipitating activity toward PEPC1; (iii) PEPC1 was more heat sensitive than the other three isoforms; (iv) PEPC1 had a pH optimum of 9 versus 8.5 for the PEPC protein complexes; (v) the high Mr PEPCs had greater apparent affinity for phosphoenolpyruvate compared to PEPC1 and (vi) PEPC1 activity was far more sensitive to metabolite activators (Gln and dihydroxyacetone phosphate) and inhibitors (Asp, Glu, 2-oxoglutarate and malate). We conclude that the interaction of the PEPC catalytic subunit with unrelated polypeptides is responsible for the observed differences between PEPC1 and the high molecular mass isoforms. We propose that this interaction possibly regulates PEPC activity in vivo.

Chlorophyta↗
PubMed1996

Cigarette smoking increases the risk for subgingival infection with periodontal pathogens.

Cigarette smoking has been found to increase the risk for periodontitis. The present study examined the association between cigarette smoking and subgingival infection with periodontal pathogens to determine if smokers are more likely to be infected with certain periodontal pathogens than non-smokers. Self-reported data on 1,426 subjects, aged 25 to 74, from the Erie County Study were obtained including data on 798 subjects who were current or former smokers. Mean clinical attachment loss was used to estimate the severity of periodontal destruction. Subgingival infection with target periodontal pathogens was determined by indirect immunofluorescence microscopy. Smokers harbored significantly higher levels and were at significantly greater risk of infection with Bacteroides forsythus than non-smokers. Adjusting for disease severity, the risk of subgingival infection with B. forsythus in current smokers was 2.3 times that of former smokers or non-smokers. The relative risk of B. forsythus infection also increased 1.18 times for every category of smoking as the amount of smoking measured in packyears increased from very light to heavy. Adjusting for disease severity, Porphyromonas gingivalis was also more likely to subgingivally infect smokers than non-smokers; however, there was not a significantly higher relative risk for infection with this bacterium. The data from this study indicate that cigarette smoking increases the likelihood of subgingival infection with certain periodontal pathogens. This may partly explain the increased risk for periodontitis seen in smokers.

Adult↗
PubMed1996

Long-term stability of Class II furcation defects treated with barrier membranes.

The present longitudinal study was designed to explore the long-term efficacy of guided tissue regeneration (GTR) in Class II furcation defects and establish the factors that might be responsible for modifying this response. Subjects with two or more mandibular molars, one of which had Class II furcation defects, received the hygienic phase of therapy followed by baseline clinical measurements and subgingival plaque sampling. GTR procedure was performed in furcation defect sites using expanded polytetrafluoroethylene (ePTFE) membranes, while the other non-furcated molars received only scaling and root planning. Twenty-eight subjects (13 females, 15 males) aged 27 to 66 were included in this longitudinal analysis. Post-surgical treatment included routine home care supplemented with daily chlohexidine rinse and systemic tetracycline. Membranes were retrieved 4 to 6 weeks after surgery. During the first year, patients were initially seen bi-weekly and subsequently monthly for professional prophylaxis. At the end of this year, clinical measurements and samples were obtained. For the next 2 years, patients were seen bi-annually for maintenance visits. Clinical measurements and microbiological samples were then repeated. Next, a tighter maintenance protocol was established and patients were seen quarterly for scaling and oral hygiene reinforcement. Final measurements and samples were taken again 1 year later (4 years postoperative). Significant probing reduction (3.00 mm) and gain in horizontal attachment (2.59 mm) were obtained 1 year postsurgery for the GTR sites. These changes were maintained over 4 years with a slight decline at the end of year 3. Changes in probing depth (PD) from year 1 to 4 served to dichotomize the sites into stable (delta PD < or = 0.9 mm), and unstable (PD increase > or = 1 mm). Of the 54 sites available for this analysis only 5 (9.3%) were unstable while 49 (90.7%) were stable or even further improved. Sites which exhibited minimal or no plaque (plaque index [PI] < or = 1) over the tight maintenance period had a further decrease in mean probing depth (0.43 mm) compared with a slight increase (-0.06 mm) in mean probing depth in sites with PI > or = 2 mm (P = 0.0235). The same phenomenon was observed for changes in relative attachment level (RAL): mean gain in RAL was 0.61 mm compared to 0.25 mm for the 2 groups, respectively (P = 0.07). Actinobacillus actinomycetemcomitans was only isolated from 2 sites at year 3, and none at year 4, compared to 21.45% of the sites at baseline. Porphyromonas gingivalis positive sites showed a continual decline over the years: 14.28% at baseline, 10.71% at year 1, and 5.1% at year 4. On the contrary, Prevotella intermedia (Pi) and Bacteroides forsythus (Bf) infected sites remained at approximately the same rate throughout the 4 years of the study (40% to 50% and 30% to 40% for Pi and Bf, respectively). Of these, Pi-infected sites exhibited less favorable clinical results compared to sites which were not infected with this microorganism. In summary, furcation defects treated with membrane barriers can be maintained in health for at least 4 years; however, good oral hygiene and frequent recall visits as part of a complete anti-infective therapy are essential. Finally, once treated, these teeth are comparable to similar molar teeth with no previous history of furcation pathosis.

Adult↗
PubMed1995

Interaction of melanin with carbon- and oxygen-centered radicals from methanol and ethanol.

The interaction of dopa-melanin (DM) and cysteinyldopa-melanin (CDM) with carbon- and oxygen-centered radicals generated by benzophenone-photosensitized hydrogen abstraction from ethanol, or by pulse radiolysis of aqueous solutions of methanol and ethanol, is reported. Photosensitized formation of carbon-centered radicals and their interaction with melanin was monitored by electron paramagnetic resonance (EPR) spin trapping using DMPO, and via the melanin free radical signal itself. In the pulse radiolysis experiments, the interaction of DM or CDM with hydroxymethyl, hydroxyethyl, and the corresponding methanol peroxyl radical was monitored by recording time-dependent changes of the melanin absorbance at selected wavelengths. The data indicate that both melanins are good scavengers of carbon-centered radicals, with corresponding rate constants in the range of 10(7) to 10(8) M-1 s-1. Significantly, compared to DM, CDM is also an exceptionally efficient scavenger of oxygen-centered radicals derived from methanol with corresponding rate constants of 2.7 x 10(4) and 2 x 10(6) M-1 s-1 for DM and CDM, respectively. The results are discussed with reference to the potential role of melanin in protecting the integrity of melanosomes by inhibiting peroxidation of lipid components of the organelle membrane.

Benzophenones↗
PubMed1995

Assessment of risk for periodontal disease. II. Risk indicators for alveolar bone loss.

This study examined the risk indicators for alveolar bone loss associated with periodontal infection. A cross-section of 1,361 subjects aged 25 to 74 years, from Erie County, NY were evaluated for interproximal alveolar bone loss and potential explanatory variables including age, gender, history of systemic diseases, smoking, and presence of 8 subgingival bacteria. Interproximal alveolar bone loss was measured from the alveolar crest to the CEJ and a mean computed for each subject. The mean bone loss per subject (BL) ranged from 0.4 to 8.8 mm, and this outcome variable was grouped into 4 ordered categories. The degree of association between the explanatory variables and BL was examined utilizing an ordinal stepwise logistic regression model. Factors which were positively associated with more severe bone loss included subgingival colonization with B. forsythus (O.R. 2.52; 95% CI: 1.98 to 3.17) or P. gingivalis (O.R. 1.73; 95% CI: 1.27 to 2.37), race (Native American, Asian, or Pacific Islanders) with an O.R. 2.40 (95% CI: 1.21 to 4.79), and gender with males having higher odds than females. Smokers had greater odds for more severe bone loss compared to non-smokers ranging from 3.25 (95% CI: 2.33 to 4.54) to 7.28 (95% CI: 5.09 to 10.31) for light and heavy smokers, respectively. Individuals at older ages also showed more severe levels of bone loss. History of kidney disease (O.R. 0.55; 95% CI: 0.35 to 0.89) and history of allergies (O.R. 0.76; 95% CI: 0.59 to 0.98) were inversely associated with severity of bone loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Gingival recession and exposure of barrier membrane: effect on guided tissue regeneration of Class II furcation defects.

The purpose of the present study was to evaluate the effect of barrier membrane exposure on the success of guided tissue regeneration in Class II furcation defects. Twenty-six subjects with mandibular Class II furcation defects received initial periodontal therapy followed by guided tissue regeneration surgery. The membrane was placed and the flaps were repositioned so that the membrane was totally submerged. Membranes were removed 4 to 6 weeks later, at which time the extent of their exposure was recorded. An overall improvement in all clinical parameters was observed for all subjects 1 year after surgery. Half of the patients had experienced no membrane exposure, while the other 13 subjects had experienced mild to pronounced exposure; both groups showed similar improvement in all clinical and surgical parameters. In light of the comparable results obtained in exposed sites, and the anatomic difficulties sometimes encountered in covering a membrane completely, in some of these cases the membrane may be left only partially submerged. This approach will allow for tighter occlusal "seal" of the tooth-membrane interface and preservation of the keratinized gingiva.

Adult↗
PubMed1994

Clinical, microbiological, and histological factors which influence the success of regenerative periodontal therapy.

The primary objectives of this double-blind, controlled clinical trial were to assess factor(s) which affect the success of guided tissue regeneration (GTR) procedures in mandibular Class II buccal furcation defects. Thirty subjects, with mandibular Class II furcation defects, were randomly assigned to one of two treatment groups; patients in Group A received oral hygiene instructions with scaling and root planing, while subjects in Group B received similar treatment but without subgingival scaling and root planing at the affected site. After initial oral hygiene instructions and scaling and root planing, GTR surgery was performed using ePTFE barrier membranes. Membranes were retrieved at 6 weeks and subjected to histological examination. Twelve months after regenerative therapy, clinical measurements and re-entry surgical measurements were repeated. Probing reduction (2.61 mm), horizontal probing attachment gain (2.59 mm), and vertical probing attachment gain (0.95 mm) were all significantly better compared to baseline. Likewise, significant improvements in furcation volume (8.0 microliters) and in bone measurements were observed at re-entry. There was no discernible difference between subjects for whom complete anti-infective therapy was deferred to the time of the surgery (Group B) compared to subjects in whom complete anti-infective therapy was performed as part of the hygienic phase of therapy (Group A). Pre-operative pocket depth was directly correlated with the magnitude of attachment gain as well as the amount of new bone formation in the furcation area. Subjects who maintained good oral hygiene and who had minimal gingival inflammation throughout the study demonstrated consistently better regenerative response.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Stabilisation of a yeast artificial chromosome containing plant DNA using a recombination-deficient host.

The large genomes of many plant species contain numerous dispersed repeat sequences. The problem of large-scale structural instability due to the presence of such repeats in yeast artificial chromosome (YAC) clones was assessed. The feasibility of stabilising plant sequences prone to rearrangement in YACs was demonstrated using a host yeast strain deficient in recombination.

Chromosomes, Fungal↗