PubMed Health⌕ Search

Biomedical subjects

J S Hodges

Publications and source records attributed to J S Hodges.

30 records · Page 2Linked to original sources
PubMed2000

Clinical performance of novel-design porcelain veneers for the recovery of coronal volume and length.

The present study evaluated the clinical performance of bonded porcelain veneers (PV) restoring substantial coronal volume and length in the anterior dentition. Forty-eight PVs were placed in 16 patients, with systematic coverage and reconstitution of the incisal edge, including well-defined anterior guidance. A standardized protocol comprising diagnostic steps that integrate additive waxups and acrylic mockups was used. PVs were fabricated using feldspathic and low-fusing porcelains in a refractory die technique. Incisal overlaps featured freestanding porcelain spans ranging from 1.5 to 5.5 mm. After a mean clinical service of 4.5 years, 13 clinical parameters for each tooth and 4 parameters that applied to persons were recorded. Permutation tests evaluated the effects of margin location, incisal edge span of porcelain, overbite, opposing contact location, and restoration age on ceramic failure and clinical marginal adaptation and seal. At recall, 100% of the veneers were satisfactory with minor interventions. The effect of slight marginal defects and porcelain cracking was negligible. Biologic, periodontal, and esthetic parameters showed excellent results, which were supported by 100% patient-reported satisfaction. All patients felt comfortable with the newly defined anterior guidance. Aging was negligible, and there were no significant effects of margin location (P > 0.08), incisal edge span of the ceramic, or overbite (P > 0.22) on ceramic failure and marginal performance. Minor alterations of the palatal margin, however, tended to be more frequent compared to facial locations, and were found especially when the opposing tooth contact in centric occlusion was located on the palatal margin (P = 0.028). Bonded ceramic restorations represent a reliable, effective procedure to restore extensive coronal volume and length in the anterior dentition.

Acrylic Resins↗
PubMed1999

Crack propensity of porcelain laminate veneers: A simulated operatory evaluation.

STATEMENT OF PROBLEM: Anterior teeth are especially subject to the thermal variations of ingested food and drinks. Postoperative cracks of porcelain laminates are considered a possible consequence of polymerization shrinkage, function, and thermocycling. PURPOSE: This investigation was conducted to define the parameters associated with the development of cracks in porcelain veneers using cyclic thermal fatigue. MATERIAL AND METHODS: Twenty-seven maxillary incisors were restored with porcelain laminate veneers and subjected to thermocycling (5 degrees C to 50 degrees C) for 1000 cycles. Ceramic cracks were reported for 11 of the 27 specimens. Teeth were sectioned and prepared for SEM analysis. Measurements of the ceramic and the luting composite thicknesses were performed for each specimen at different restoration locations (facial, incisal, and proximal). RESULTS: No significant differences in the ceramic or the luting composite thicknesses were observed between cracked and uncracked specimens. However, significant differences were observed in the ratio of the ceramic and luting composite thicknesses. Most cracked samples exhibited a ratio at the facial location below 3.0 (2.6 +/- 0.35), whereas most noncracked specimens were above this value (3.9 +/- 0.19). Incisal and especially proximal measurements alone were not significantly different between cracked versus uncracked specimens. Ceramic was slightly thinner in the facial aspect than in the proximal aspect, which was also thinner than the incisal aspect. Composite in the facial aspect was thinner in the cervical area than in the incisal third of the tooth. CONCLUSIONS: Significant cyclic temperature changes can induce the development of flaws in porcelain veneers. Control of tooth reduction and the application of die spacers during laboratory procedures undoubtedly represent key elements; a sufficient and even thickness of ceramic combined with a minimal thickness of luting composite will provide the restoration with a favorable configuration with regard to crack propensity, namely, a ceramic and luting composite thickness ratio above 3.

Analysis of Variance↗
PubMed1999

Effects of processing parameters on physical properties of the silicone maxillofacial prosthetic materials.

OBJECTIVES: Maxillofacial prostheses are commonly fabricated using dental stone molds. However, for evaluating physical properties, maxillofacial materials are most often cured in metal molds. A-2186 is a silicone-based maxillofacial prosthetic material. Because its cure may be inhibited by traces of impurities, its physical properties may be different when it contains additives and is cured in dental stone molds, compared to when it is cured in metal molds without additives. This study's purpose is to determine and compare the physical properties of A-2186 cured in stainless steel molds and stone molds. The effects of additives and cure conditions on the physical properties were also studied. METHODS: Hardness, tensile strength, ultimate elongation, and tear strength of A-2186 cured in dental stone molds, stainless steel molds, and with and without additives were determined. The bonding strength of A-2186 to four adhesives was determined by the peel test. All comparisons were made using analysis of variance (ANOVA). RESULTS: Hardness, tensile strength and ultimate elongation of A-2186 cured in stainless steel molds are significantly higher than those cured in stone molds. Adding a small amount of a pigment, a kaolin and a fiber reduces hardness, tensile strength, ultimate elongation and tear strength. Except for Hydrobond, the bond strength of the adhesives to A-2186 was not significantly affected by the cure conditions and additives. SIGNIFICANCE: Physical properties of A-2186 are affected by the additives commonly used in fabricating maxillofacial prostheses, and use of stone molds for curing degrades A-2186's mechanical properties. In fabricating clinical prostheses, special attention should be exercised to avoid contamination of A-2186 with impurities that could inhibit curing and produce inferior prostheses.

Adhesiveness↗
PubMed1999

Cross-study hierarchical modeling of stratified clinical trial data.

Hierarchical random-effects models can be used to estimate treatment or other covariate effects in single-study analyses coordinated over multiple clinical units and can also be extended to a wide variety of cross-study applications. After reviewing the single-study case, we use data from five trial protocols to look for units that tend to have treatment effects consistently above or below the study-specific grand mean across several studies. As a first step, we summarize the patient-level data as study-specific and unit-specific estimated treatment effects and standard errors using independent Cox regression models. We then compare the results of a hierarchical model using these data summaries as input to those produced by a more fully Bayesian method that uses the actual patient-level survival data. We also compare various different models using a deviance information criterion, a recent extension of the Akaike information criterion designed for hierarchical models. Our procedure appears to be effective at answering the question whether certain clinical units of the Terry Beirn Community Programs for Clinical Research on AIDS are better than others at identifying treatment effects where they exist.

AIDS-Related Opportunistic Infections↗
PubMed1999

A prospective randomized trial of four three-drug regimens in the treatment of disseminated Mycobacterium avium complex disease in AIDS patients: excess mortality associated with high-dose clarithromycin. Terry Beirn Community Programs for Clinical Research on AIDS.

The optimal regimen for treatment of Mycobacterium avium complex (MAC) disease has not been established. Eighty-five AIDS patients with disseminated MAC disease were randomized to receive a three-drug regimen of clarithromycin, rifabutin or clofazimine, and ethambutol. Two dosages of clarithromycin, 500 or 1,000 mg twice daily (b.i.d.), were compared. The Data and Safety Monitoring Board recommended discontinuation of the clarithromycin dosage comparison and continuation of the rifabutin vs. clofazimine comparison. After a mean follow-up of 4.5 months, 10 (22%) of 45 patients receiving clarithromycin at 500 mg b.i.d. had died (70 deaths per 100 person-years) compared with 17 (43%) of 40 patients receiving clarithromycin at 1,000 mg b.i.d. (158 deaths per 100 person-years) (relative risk, 2.43; 95% confidence interval, 1.11-5.34; P = .02). After 10.4 months, 20 (49%) of 41 patients receiving rifabutin had died (81 deaths per 100 person-years) compared with 23 (52%) of 44 patients receiving clofazimine (94 deaths per 100 person-years) (relative risk, 1.20; 95% confidence interval, 0.65-2.19; P = .56). Bacteriologic outcomes were similar among treatment groups. In treating MAC disease in AIDS patients, the maximum dose of clarithromycin should be 500 mg b.i.d.

AIDS-Related Opportunistic Infections↗
PubMed1999

Hierarchical proportional hazards regression models for highly stratified data.

In clinical trials conducted over several data collection centers, the most common statistically defensible analytic method, a stratified Cox model analysis, suffers from two important defects. First, identification of units that are outlying with respect to the baseline hazard is awkward since this hazard is implicit (rather than explicit) in the Cox partial likelihood. Second (and more seriously), identification of modest treatment effects is often difficult since the model fails to acknowledge any similarity across the strata. We consider a number of hierarchical modeling approaches that preserve the integrity of the stratified design while offering a middle ground between traditional stratified and unstratified analyses. We investigate both fully parametric (Weibull) and semiparametric models, the latter based not on the Cox model but on an extension of an idea by Gelfand and Mallick (1995, Biometrics 51, 843-852), which models the integrated baseline hazard as a mixture of monotone functions. We illustrate the methods using data from a recent multicenter AIDS clinical trial, comparing their ease of use, interpretation, and degree of robustness with respect to estimates of both the unit-specific baseline hazards and the treatment effect.

AIDS-Related Opportunistic Infections↗
PubMed1999

Effects of extreme heat on teeth with implications for histologic processing.

This pilot study examined teeth subjected to extreme heat under laboratory conditions, and the subsequent effect of decalcification and histologic processing. Physical and microscopic findings were evaluated in relation to temperature and duration of thermal insult. Microscopic examination following decalcification and histologic processing revealed changes including severe tissue fragmentation, vapor bubbles within dentinal tubules, altered histologic staining, charring and tissue shrinkage. Dentin appeared to be the most reliable microscopic identifier of incinerated dental tissues. Temperatures above 600 degrees C strongly predicted tooth disintegration following decalcification. This finding has implications in incineration cases where histologic evidence must be maintained and examined intact.

Dental Cementum↗
PubMed1997

Rule-based ranking schemes for antiretroviral trials.

Endpoints are a continuing source of controversy in clinical trials of antiretroviral (specifically, anti-HIV) treatments. The most visible disagreement is about the respective roles of morbidity and mortality as endpoints, and laboratory measurements as endpoints. Laboratory measurements have been intensely examined as possible surrogates for clinical outcomes, but the definition of the usual clinical outcome-first occurrence or recurrence of an AIDS-defining condition or death-has received little critical scrutiny. First disease progression has serious weakness as an endpoint, and one should consider alternatives. In this paper, we suggest using rule-based schemes to rank patients' post-randomization histories and then using the ranks as an outcome measure, an extension of the work by Follmann et al. on heart disease. We evaluated six rule-based ranking schemes for antiretroviral trials by applying them to 60 participants in CPCRA 002 and comparing the results to subjective rankings given by five experts. The expert's rankings were in good agreement with each other, and the six rule-based schemes were clearly differentiated by their degree of agreement with the expert's rankings. The ranking scheme most in accord with the experts ranked patients first by seriousness of their most serious AIDS-defining disease, second by the timing of that disease, and the third by the total number of AIDS-defining diseases they experienced. Finally, we used this rule-based rankings to re-analyse CPCRA 002.

Algorithms↗
PubMed1996

Zidovudine alone or in combination with didanosine or zalcitabine in HIV-infected patients with the acquired immunodeficiency syndrome or fewer than 200 CD4 cells per cubic millimeter. Investigators for the Terry Beirn Community Programs for Clinical Research on AIDS.

BACKGROUND: We compared two combinations of nucleosides with zidovudine alone in patients with advanced human immunodeficiency virus (HIV) infection. METHODS: A total of 1102 patients with the acquired immunodeficiency syndrome or fewer than 200 CD4 cells per cubic millimeter were randomly assigned to receive zidovudine alone or zidovudine combined with either didanosine or zalcitabine. Disease progression, survival, toxic effects, and the CD4 cell response were assessed. RESULTS: After a median follow-up of 35 months, disease progression or death occurred in 62 percent of the 363 patients assigned to zidovudine plus didanosine, 63 percent of the 367 assigned to zidovudine plus zalcitabine, and 66 percent of the 372 assigned to zidovudine only (P=0.24). As compared with zidovudine therapy, treatment with zidovudine plus didanosine was associated with a relative risk of disease progression or death of 0.86 (95 percent confidence interval, 0.71 to 1.03), and treatment with zidovudine plus zalcitabine was associated with a relative risk of 0.92 (95 percent confidence interval, 0.76 to 1.10). Survival was similar in the three groups. In a subgroup analysis, combination therapy delayed disease progression or death in patients who had previously received zidovudine for 12 months or less. Therapy with zidovudine plus didanosine resulted in more gastrointestinal adverse effects, and treatment with zidovudine plus zalcitabine, more neuropathy. The mean increases in CD4 cell counts at two months were higher with combination therapy than with zidovudine alone. CONCLUSIONS: In patients with advanced HIV infection, combination therapy with zidovudine and either didanosine or zalcitabine is not superior to zidovudine therapy alone. However, these combinations may be more effective than zidovudine monotherapy in patients with little or no previous zidovudine treatment.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Rating the quality of evidence for clinical practice guidelines.

This article describes the system for rating the quality of medical evidence developed and used during creation of the Agency for Health Care Policy and Research-sponsored heart failure guideline. Previous approaches to rating evidence were not designed for use in the setting of clinical practice guidelines. The present system is based on the tenet that flaws in research design are serious to the extent they threaten the validity of the results of studies. A taxonomy of major and minor flaws based on that tenet was developed for randomized controlled trials and for cohort and medical registry studies. The use of the system is described in the context of two difficult clinical issues considered by the Panel: the role of coronary artery revascularization and the use of metoprolol.

Bias↗