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At least 487 records · Page 27Linked to original sources
PubMed2005

Bayesian cure rate frailty models with application to a root canal therapy study.

Due to natural or artificial clustering, multivariate survival data often arise in biomedical studies, for example, a dental study involving multiple teeth from each subject. A certain proportion of subjects in the population who are not expected to experience the event of interest are considered to be "cured" or insusceptible. To model correlated or clustered failure time data incorporating a surviving fraction, we propose two forms of cure rate frailty models. One model naturally introduces frailty based on biological considerations while the other is motivated from the Cox proportional hazards frailty model. We formulate the likelihood functions based on piecewise constant hazards and derive the full conditional distributions for Gibbs sampling in the Bayesian paradigm. As opposed to the Cox frailty model, the proposed methods demonstrate great potential in modeling multivariate survival data with a cure fraction. We illustrate the cure rate frailty models with a root canal therapy data set.

Bayes Theorem↗
PubMed1997

Statistical methodology: II. Reliability and variability assessment in study design, Part A.

Assessment of test reliability and validity is often complex. Although tests of correlation are frequently used to measure interest agreement, such indexes measure only the strength of the linear relationship between variables and may not provide an accurate assessment of the correspondence between test results. Inspection of interest differences, either visually or using the r1, may provide a better indicator of the correspondence between test results and accounts for measurement biases. Strength of association between categorical variables can be measured using related tests such as the kappa statistic. Test reliability may be assessed by retesting, but this is not practical in many cases when subject memory or learning may confound the results of repeated examinations. Several methods exist for determining reliability from a single test administration and for assessing the correspondence between answers to homogeneous test questions. In the continuation article (Part B) on this subject, the concept and assessment of validity will be examined in more detail, and techniques for maximizing the reliability and validity of questionnaires will be discussed.

Emergency Medicine↗
PubMed2001

Effect of an enamel matrix protein derivative (Emdogain) on ex vivo dental plaque vitality.

BACKGROUND: A common clinical observation following surgical periodontal therapy with an enamel matrix derivative (Emdogain) is the improved healing of the soft tissues and the limited inflammation of the operated areas. These clinical observations are empirical and difficult to explain. One of the factors influencing the early wound healing might be a potential antimicrobial effect of Emdogain. AIM: To investigate the effect of Emdogain on the vitality of ex vivo supragingival dental plaque and to compare this effect to that of a standard 0.2% chlorhexidine solution. MATERIALS AND METHODS: 24 patients suffering from adult periodontitis were included in the study. At the beginning of the experiment, all participants were given a professional tooth cleaning. For the following 4 days, they had to refrain from any kind of oral hygiene measures. At day 5, from each of the volunteers, a voluminous plaque biofilm sample was taken with a sterile curette from the vestibular surfaces of the 1st lower molars and divided into 5 equal parts. Each part was mounted with 5 microl of the following solutions: (1) NaCl, (2) enamel matrix derivative dissolved in water (EMD), (3) enamel matrix derivative dissolved in the vehicle (Emdogain), (4) vehicle (propylene glycol alginate, PGA), (5) 0.2% chlorhexidine digluconate (CHX). After a reaction time of 2 min the test solutions were sucked off, and subsequently the biofilm was stained with a fluorescence dye. The vitality of the plaque flora after the treatments was evaluated under the fluorescence microscope (VF%). RESULTS: Plaque samples treated with NaCl showed a mean vitality of 76.8+/-8%. The EMD, Emdogain, PGA and CHX showed VF values of 54.4+/-9.2, 21.4+/-10.6%, 19.6+/-11.6% and 32.3+/-11.8%, respectively. Emdogain, PGA and CHX showed statistically highly significant reductions (p<0.0001) in terms of bacteria vitality when compared to water (negative control) and EMD. Both Emdogain and PGA were found to be statistically significantly different compared to CHX (p<0.001) (positive control). CONCLUSION: The results of this study indicate that Emdogain might have an antibacterial effect on the vitality of the ex vivo supragingival dental plaque flora.

Adult↗
PubMed2006

A comparison of the visual and technical assessment of preparations made by dental students.

The preparation of acrylic teeth in a simulated clinical environment (phantom head) plays an essential role in pre-clinical dental education where evaluation is performed visually by instructors. The aim of this investigation was to verify the quality criteria of a tooth preparation for a metal-ceramic crown (tooth No. 21) with the help of digital measurement. Thirty-six acrylic teeth were prepared by students and one tooth was prepared ideally by a trained dentist: These were examined and compared. Five experienced instructors independently assessed the quality criteria with the use of a criterion list. Afterwards, the teeth were scanned with the 3D-laser scanner 'es1' (Etkon Company, Munich, Germany). The calculation of the correlation coefficient demonstrated a satisfactory correlation between visual and digital rating concerning convergence angle, shoulder width and occlusal reduction. Greater differences between experimental groups were observed with regards to other criteria on the applied criterion list. A directed calibration of the evaluators and a re-evaluation of some measurements would be necessary to gain more precise results.

Computer-Assisted Instruction↗
PubMed2000

Production of volatile sulphur compounds in diseased periodontal pockets is significantly increased in smokers.

OBJECTIVE: This study was undertaken in order to test the hypothesis that the consequences of tobacco smoking may include increased synthesis of toxic volatile sulphur compounds in diseased periodontal pockets. DESIGN: A cross-sectional, parallel study comparing groups of smokers and non-smokers with periodontitis and the level of volatile sulphur compounds in the gingival sulci of these subjects. PATIENTS AND METHODS: Levels of volatile sulphur compounds were measured in diseased periodontal sites of 12 smokers and 11 non-smokers using a portable sulphide monitor. Anaerobic and aerobic counts of the total cultivable subgingival microflora of both groups were also determined. RESULTS: The percentage of sites per subject with high levels of sulphides (> or = 10 units) detected in moderate (4-6 mm) and deep (> or = 7 mm) periodontal pockets was found to be significantly higher in smokers, compared to non-smokers (P = 0.040 and P = 0.005, respectively). No significant difference in the microbiological parameters tested were observed between the two groups. CONCLUSIONS: Increased production of volatile sulphur compounds may represent a further mechanism of increased susceptibility to periodontitis in smokers and also help to explain the reported association between smoking and halitosis.

Adult↗
PubMed2000

Interleukin-1 beta, interleukin-6, and tissue inhibitor of metalloproteinase-1 in the synovial fluid of the temporomandibular joint with respect to cartilage destruction.

OBJECTIVE: The distribution and biological roles of interleukin (IL)-1 beta, IL-6, and tissue inhibitor of metalloproteinase-1 (TIMP-1) in the synovial fluid of patients with non-inflammatory chronic temporomandibular joint (TMJ) disorders were evaluated in relation to pain upon joint movements and X-ray and magnetic resonance imaging (MRI) findings. MATERIALS AND METHODS: TMJ aspirates were obtained from 48 patients (48 joints) with chronic TMJ disorders and from 18 controls (18 joints). The IL-1 beta and IL-6 levels in the aspirates were determined by using an enzyme-linked immunosorbent assay and the TIMP-1 level was measured by an enzyme immunoassay. Following examinations for pain upon joint movements and X-ray and MRI observations, the IL-1 beta, IL-6, and TIMP-1 levels and frequencies of their detection were compared. RESULTS: The IL-1 beta level and frequency of detection showed no correlation with pain upon joint movements or with the X-ray and MRI findings. In the frequency of detection of IL-6, there were significant differences between control (no detection) and all chronic TMJ disorder groups that were classified by imaging diagnosis (P < 0.001). A correlation was also noted between the presence of IL-6 and pain upon joint movements. The IL-6 level was correlated with the TIMP-1 level and with pain upon joint movements. TIMP-1 level was correlated with pain upon joint movements. The TIMP-1 was present in higher level from patients with chronic TMJ disorders who exhibited osseous changes on the X-ray images. CONCLUSION: The results indicated that the IL-6 and TIMP-1 levels in the TMJ aspirates of patients with chronic TMJ disorders have been raised. The former was not detected in the TMJ aspirates of the control. These findings suggest that IL-6 and TIMP-1 might play a role in the etiology of chronic TMJ disorders, but further studies are needed to validate this.

Adult↗
PubMed2000

A histomorphometric and biomechanical study of the effect of delayed titanium implant placement in irradiated rabbit bone.

BACKGROUND: The time interval from irradiation to implant surgery has been considered an impact factor for implant integration in irradiated bone and the importance of a long interval between the radiation trauma and reconstructive bone surgery has been suggested. PURPOSE: The present study was undertaken to histomorphometrically and biomechanically analyze the effect of delayed implant placement on bone healing around titanium implants in irradiated bone. MATERIALS AND METHODS: Rabbits were given a single dose of 15 Gy Cobalt60 radiation to one hind leg, the other hind leg serving as a control. Titanium screws were inserted into the femur and tibia directly and at 12 weeks and 52 weeks after irradiation. The implants were evaluated after a healing time of 8 weeks. The torques necessary for removal of the implants were measured. Histomorphometry with respect to bone-metal contact and amount of bone surrounding the implants was performed. RESULTS: The biomechanical force necessary to unscrew the titanium implants in the irradiated bone was significantly increased after a resting period of 1 year between irradiation and implant placement, compared to direct implant placement. The histomorphometric evaluation showed an improvement of bone healing around the implants in the irradiated bone, both after a resting period of 12 weeks and after 1 year compared to direct implant placement. CONCLUSIONS: It is concluded that a relatively long interval between irradiation and reconstructive bone surgery will improve osseointegration of titanium implants in irradiated rabbit bone.

Animals↗
PubMed2001

Deproteinized bovine bone used as an adjunct to guided bone augmentation: an experimental study in the rat.

BACKGROUND: Promising results have been reported following treatment of periodontal and peri-implant bone defects with deproteinized bovine bone grafts, but their influence on bone formation has not been clarified. PURPOSE: The goal of this study was to examine whether implantation of deproteinized bovine bone (Bio-Oss, Geistlich AG, Wolhusen, Switzerland) influences bone formation when used as an adjunct to guided bone augmentation (GBA). MATERIALS AND METHODS: A rigid, hemispherical, Teflon capsule was loosely packed with a standardized quantity of Bio-Oss and placed with its open part facing the lateral surface of the mandibular ramus (test) in 30 rats. At the contralateral side of the jaw, an empty capsule was placed (control). Groups of 10 animals were sacrificed after 1, 2, and 4 months. The volumes of the space created by the capsule and of the (1) newly formed bone, (2) remaining Bio-Oss particles, (3) soft connective tissue, and (4) acellular space in the capsule were estimated by a point-counting technique in three or four histologic sections, taken by uniformly random sampling. RESULTS: Bone formation at 1 month was limited in both tests and controls. After 2 months, the mean volume of the newly formed bone occupied 9.0% of the space created by the capsule in the test specimens compared with 23.8% in the control specimens (p < .01). After 4 months, the respective figures were 11.6% (tests) versus 38.7% (controls) (p < .01). CONCLUSION: It can be concluded that Bio-Oss, used as an adjunct to GBA, interferes with bone formation.

Animals↗
PubMed2002

Bone reactions to oxidized titanium implants with electrochemical anion sulphuric acid and phosphoric acid incorporation.

BACKGROUND: The importance of the surface properties of implants for a successful osseointegration has been emphasized. It is generally known that bone response to implant surfaces is considerably related to the various surface properties. PURPOSE: The purpose of this study was to investigate bone tissue reactions to multifactorial biocompatibility of the surface oxide of electrochemically oxidized titanium implants. The ultimate objective was to improve surface quality, resulting in enhancement of clinical outcomes of osseointegrated implants. MATERIALS AND METHODS: Three different surface types of commercially pure titanium (c.p. Ti) implants were prepared. Turned implants were used for controls and test implants were prepared by the micro arc oxidation (MAO) method, either in sulphuric acid (S implants) or in phosphoric acid (P implants). Implants were inserted in the femur and tibia of 10 mature New Zealand White rabbits. The bone response was evaluated by biomechanical tests, histology, and histomorphometry. The follow-up time was 6 weeks. RESULTS: The mean peak values of the removal torque showed significant differences between control and test S implants (p =.022) but showed no significant differences between control and test P implants (p =.195) or between test S and test P implants (p =.457). In addition, the histomorphometric comparisons of the bone-to-metal contact around entire implants demonstrated 186% increase in S implants (p =.028) and 232% increase in P implants (p =.028) compared with the paired control groups. Quantification of the bone area in the threads did not show any significant differences. CONCLUSIONS: The present results suggest that the primary mode of action in strong bone response to S implants is mechanical interlocking, and to P implants, it is biochemical interaction. It is possible that the phosphate groups in the titanium oxide of P implants provide potential chemical bonding sites for calcium ions and hydroxyapatite of the bone matrix during biologic mineralization. key words: bone responses, histomorphometry, oxidized implants, removal torque test, surface oxide properties

Animals↗
PubMed2002

Evaluation of microleakage in cervical margins of various posterior restorative systems.

PURPOSE: The purpose of this in vitro study was to evaluate the microleakage and dye penetration patterns of various restorative systems in the cervical margins of Class II cavities using the dye penetration technique. MATERIALS AND METHODS: Ninety bovine incisors were selected and part of the crown was sectioned producing a standardized occlusogingival margin of 4 mm. Standardized Class II box cavities were designed on the mesial (MO) and distal (OD) surfaces with the gingival margin in dentin. The cavities were randomly divided into six groups (n = 30): group 1 (control), Etch & Prime 3.0 (Degussa AG) + Definite (Degussa AG); group 2, Prime & Bond NT (Dentsply De Trey) + Definite; group 3, Etch & Prime 3.0 + flowable composite resin Wave (SDI) + Definite; group 4 (control), Prime & Bond NT + TPH Spectrum (Denstply De Trey); group 5, Etch & Prime 3.0 + TPH Spectrum; group 6, Prime & Bond NT + Wave + TPH Spectrum. After they were finished and polished, the specimens were subjected to 1500 thermal cycles in baths of 5 degrees+/-2 degrees C and 55 degrees+/-2 degrees C with 60 seconds of dwell time for each bath. After the thermocycling, the specimens were sealed with acid-resistant varnish, leaving a 1-mm window around the cervical margin interface, and immersed in 2% methylene blue buffered solution for 4 hours. Then the specimens were sectioned longitudinally in half and qualitatively evaluated under stereomicroscopy at 45 times magnification, using ranked scores for the dentin cervical margin (0-4). The dye penetration pattern (adhesive or dentinal) was also evaluated. The data were subjected to a reproducibility kappa test, and the mean of the three examiners' scores was analyzed by the Kruskal-Wallis nonparametric test and a multiple comparison nonparametric test. Fisher's exact test was used to evaluate the dye penetration pattern. RESULTS: The rank sums of the groups were expressed in decreasing order: group 4, 67.23a; group 3, 72.58ab; group 6, 78.43ab; group 5, 93.19bc; group 2, 112.97c; group 1, 113.52c. (Statistically significant differences are expressed by different superscript letters.) The results indicate that none of the systems used in this study was able to impede microleakage, and that the use of a flowable resin decreases the values of leakage only for Definite composite resin. The dye penetration pattern for the groups that used Prime & Bond NT was predominantly dentinal, whereas the pattern for Etch & Prime 3.0 groups was adhesive. CLINICAL SIGNIFICANCE: An ormocer-based resin that was developed to improve the physical properties of composite resin and a self-etching primer adhesive system obtained higher values of microleakage compared with a one-bottle adhesive system and a microhybrid composite resin. The flowable composite resin decreased the values of microleakage only for the ormocer-based resin.

Animals↗
PubMed2002

Effect of resin-coating technique on dentin tensile bond strengths over 3 years.

PURPOSE: The resin-coating technique has been developed to protect prepared dentin and underlying pulp tissue. The purpose of this study was to evaluate the resin-coated dentin bond durability over a period of 3 years of a resin cement and to compare it with two representative resin cements. MATERIALS AND METHODS: Ten bovine dentin specimens were tested for tensile bond strengths with each of the following three materials: CLAPEARL DC with a resin-coating technique (CDRC), Panavia 21 (PA21), and Super Bond C&B (SBCB) at 1 day, 6 months, 1 year, and 3 years. Mean bond strengths were compared statistically by two-way analysis of variance and Fisher's PLSD test (p < .05). The mode of failure was classified by scanning electron microscope observation and analyzed using the Mann-Whitney U-test. RESULTS: The 3-year bond strengths of all resin cements were significantly lower than those at the other experimental periods except for 1 year (p < .05). There was no significant difference in mean bond strength between CDRC and SBCB (p > .05). Regarding the fracture modes, in the case of CDRC, an increase in adhesive failure at the resin-dentin interface was observed as the time period lengthened. Statistical differences were observed between SBCB and the other materials at 1 year (p < .05) and between PA21 and the other materials at 3 years (p < .05). CLINICAL SIGNIFICANCE: The mean tensile bond strengths of the three resin cements to dentin decreased at different rates during the study; the rate at which the bond decreases is likely to affect the long-term durability of restorations.

Acid Etching, Dental↗
PubMed2001

Influence of psychological factors on the acceptance of complete dentures.

OBJECTIVES: To assess the influence of psychological factors on the acceptance of complete dentures in a population wearing dentures judged to be clinically satisfactory. DESIGN: Subjects were asked to complete personality profiles and also to rate their dentures using a denture satisfaction questionnaire. SETTING: The survey was conducted in the prosthetics clinic of a teaching hospital. SUBJECTS: Patients were selected from those who had new complete dentures constructed in the department within the previous two years. INTERVENTION AND MAIN OUTCOME MEASURES: The personality inventory was a self-administered questionnaire comprising 240 items covering the five domains of personality. Denture satisfaction was scored on a nine item scale with four Likert type responses to each. RESULTS: A group of 16% consistently complained about their dentures. Statistical analysis showed that personality factors especially Neuroticism had a significant relationship with denture satisfaction. CONCLUSION: Psychological factors significantly influence denture satisfaction and profiles may provide useful in predicting potential difficult denture wearers.

Aged↗
PubMed2002

Health-related quality of life in patients with primary Sjögren's syndrome and xerostomia: a comparative study.

OBJECTIVE: To compare the health status of groups of Primary Sjögren's and Xerostomia patients, using the Medical Outcomes Short Form 36 (SF-36). The SF-36 is a generic measure, divided into eight domains, used in the assessment of health-related quality of life. PATIENTS AND METHODS: The SF-36 was given to 2 groups: Group 1 comprised 43 patients diagnosed with Primary Sjögren's Syndrome (1 degrees SS) and an unstimulated whole salivary flow rate (UFR) of <0.1 ml/min). Group 2 (n = 40) reported Xerostomia but had an UFR >0.2 ml/min. Sub groups of patients in Groups 1 and 2 were compared with community normative data, for the SF-36. RESULTS: There were trends to suggest lower SF36 scores for 1 degrees SS patients but there were no significant differences between the mean domain scores of Groups 1 and 2. 1 degrees SS and Xerostomia patients registered lower mean scores across all 8 domains, compared with normative community data. CONCLUSION: The SF-36 was unable to detect significant differences between subjects with 1 degrees SS and Xerostomia but a larger sample size is required to confirm these findings. The results of this limited study suggest that a disease-specific measure is required to assess the impact 1 degrees SS on health-related Quality of life (QOL).

Activities of Daily Living↗
PubMed2002

Pulpal heat changes with newly developed resin photopolymerisation systems.

Composite resin is a widely-used direct tooth coloured restorative material. Photoactivation of the polymerisation reaction can be achieved by visible blue light from a range of light sources, including halogen lamps, metal halide lamps, plasma arc lamps, and Light Emitting Diode (LED) lights. Concerns have been raised that curing lights may induce a temperature rise that could be detrimental to the vitality of the dental pulp during the act of photoactivation. The present study examined heat changes associated with standardised class V restorations on the buccal surface of extracted premolar teeth, using a curing time of 40 seconds. The independent effects of type of light source, resin shade, and remaining tooth thickness were assessed using a matrix experimental design. When a conventional halogen lamp, a metal halide lamp and two different LED lights were compared, it was found that both LED lamps elicited minimal thermal changes at the level of the dental pulp, whereas the halogen lamp induced greater changes, and the metal halide lamp caused the greatest thermal insult of all the light sources. These thermal changes were influenced by resin shade, with different patterns for LED versus halogen or halide sources. Thermal stress reduced as the remaining thickness of tooth structure between the pulp and the cavity floor increased. From these results, it is concluded that LED lights produce the least thermal insult during photopolymerisation of composite resins.

Acid Etching, Dental↗
PubMedDate not supplied

A comparison of oral health in elderly populations seeking and not seeking dental care.

The General Oral Health Assessment Index (GOHAI) has been recommended for use as an outcome measure in the evaluation of dental treatment. This study was designed to assess the ability of the GOHAI in the evaluation of differences in those actively seeking dental care compared with those not seeking care. GOHAI was self-administered to two samples of elderly individuals, over 65 years of age, in the Columbus, OH, area. The first sample was ambulatory individuals living in a nursing home in Columbus, and the second sample consisted of patients accessing dental care at The Ohio State University (OSU) dental school clinics. Other variables used in this study were age, gender, self-rated oral and general health, and use of prostheses. Overall mean GOHAI score in the nursing home respondents was significantly higher (32.1 +/- 3.0) when compared with that of dental patients (mean, 30.4 +/- 3.9, p = 0.01). Mean GOHAI scores for all categories of variables used were consistently higher (better) in the nursing home respondents than for the dental patients. Results of this study show that self-assessed oral health measured by the GOHAI was higher for those individuals not seeking dental care than for those actively seeking dental care. The GOHAI is sensitive as an outcome measure in differentiating between individuals actively seeking care and those not seeking care.

Age Factors↗