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Biomedical subjects

J W Osborne

Publications and source records attributed to J W Osborne.

At least 19 recordsLinked to original sources
PubMed1994

Characterization of induced pulpal hypoxia using 3H-misonidazole.

Tritiated misonidazole (3H-MISO) is a bioreductively activated marker which preferentially binds to cells with decreased oxygen tension (hypoxia). Detection of hypoxia may be an important indicator of metabolic imbalance. For 3H-MISO to be functional as a marker, normal oxygen (normoxic) levels must be distinguishable from increased hypoxic retention. This investigation characterized retention of 3H-MISO in: (a) normoxic pulp, (b) induced hypoxic pulp, and (c) reoxygenated hypoxic pulp. Rats were injected intraperitoneally with either 3H-MISO, unlabeled MISO, or saline, then divided into normoxic and hypoxic groups with appropriate controls. Normoxic animals were maintained at ambient pressure. Hypoxia was induced by placing animals in a hypobaric chamber at 0.5 atm. Pulps were then removed and prepared for liquid scintillation counting. Hypoxic pulps retained significantly more 3H-MISO than normoxic pulps (analysis of variance, p = 0.001). Hypoxic 3H-MISO retention was unaffected by subsequent, transient tissue reoxygenation. 3H-MISO detects changes in pulpal oxygen status that deviate from normal.

Analysis of Variance↗
PubMed1994

Crypt cell thymidine incorporation in ileal urinary pouch. Preliminary report.

This is a brief communication about mucosal change in ileal urinary reservoirs, the earliest reported observations to date. Previous authors described early villous atrophy and crypt elongation, late panmucosal atrophy and metaplasia. Crypt cell proliferation should be a forerunner of these events and therefore warrants quantitative measurement. We studied continent pouches in dogs on postoperative days 42 and 43 using in vivo tritiated thymidine incorporation into crypt cell DNA, a novel application of autoradiography for urinary reservoirs. Adjacent normal ileum provided the internal control. Increased crypt cell thymidine incorporation was confirmed at this early time.

Animals↗
PubMed1993

Mercury in solution following exposure of various amalgams to carbamide peroxides.

Carbamide peroxide (CP) is an easily administered material for whitening teeth. Although toxicological research on CP alone has revealed no adverse health effects, possible oxidation and release of mercury from amalgams have not previously been investigated. This research evaluated the quantitative release of mercury from amalgams into solution by CP. CP preparations can generally be divided into two classes based on the presence or absence of carbopol, an oxygen-releasing inhibitor. Rembrandt (R), a 10% CP with carbopol and White and Brite (WB), a 10% CP without carbopol were used in this study. Four different types of amalgams [Dispersalloy (D), Sybraloy (S), Tytin (T) and Valiant Ph.D. (V)] were selected. Uniform samples of the four amalgams were prepared and stored at 37 degrees C for 1 week. Vials of saline (10 ml), R and WB were prepared. R and WB were mixed with saline to a 50:50 solution to reduce viscosity and facilitate stirring. Magnetic teflon coated stir bars were placed in all vials, and one amalgam specimen was placed in each non-control vial. After being stirred for 8 hours, solutions were analyzed for elemental mercury content using a Jerome Gold Film Mercury Analyzer. All background mercury levels were zero, but following the experiment there were significantly higher amounts of mercury in the CP solutions as compared to the 100% saline solutions. These results suggest there is an active oxidation of the amalgam releasing mercury ions into solution.

Acrylic Resins↗
PubMed1992

A preliminary test of the replicability of a computerized occlusal analysis system.

A system for computerized occlusal analysis was tested in a laboratory. The investigation focused on the ability of the system to replicate results when sensors were used five times under a series of three levels of load that were applied to the occlusion. Also compared were the effects of zero mm immediate side shift and 0.2 mm immediate side shift on the research model. Results showed that there were both statistically significant differences (p less than or equal to 0.05 level) and nonsignificant differences scattered among the data derived from both articulator treatments.

Bite Force↗
PubMed1992

Dental amalgam and mercury vapor release.

Dental diseases are among the most common ailments, and dentists in the United States spend over 50% of their time in dental practice rebuilding carious, malformed, and traumatically injured teeth. It is logical, therefore, that the majority of the dental school curriculum is devoted to the diagnosis, prevention, and treatment of teeth with anomalies. Dentists have several choices of materials they can use to accomplish the task of rebuilding teeth. Besides amalgam, they have ceramic materials, resin composites, base-metal and noble casting alloys, and glass-ionomer cements to use to restore the posterior dentition. Each of these restorative materials has advantages and disadvantages, and the clinical judgment as to when a particular material should be used is given a high priority in dental education. Amalgam is the most widely used of these restorative materials, with 92% of dentists listing it as the material of choice in the posterior of the mouth (Clinical Research Associates, 1990). Dentists have been placing amalgams for over 150 years in the US. They placed 150 million last year, which represents over 75 tons of amalgam alloy. The reasons that dentists use this restorative material so frequently are its durability, ease of manipulation, and low cost. Numerous clinical studies have been conducted on the serviceability of amalgam. Most of these have been on the old, low-copper alloys, and results indicate that they last from 8 to 15 years (Bailit et al., 1979; Osborne et al., 1980; Qvist et al., 1986). In the past 20 years, vast improvements have been made in amalgams with the development of the high-copper systems.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Amalgam↗
PubMed1992

Zinc-containing high copper amalgams: a 3-year clinical evaluation.

Dispersalloy with a 0.9% zinc and a non-zinc composition and Tytin with a 1.0%, 0.33% and a non-zinc formula were evaluated. Thirty-nine patients received 247 amalgam restorations, in which these five formulas were randomly placed. Results after 3 years indicate that the zinc-containing alloys had less fracture at the margins than the non-zinc alloys. The data indicate that small amounts of zinc (approximately 1%) play a beneficial role in the serviceability of high copper amalgams.

Adult↗
PubMed1992

Pulp response to bases and cavity depths.

In cavities of ferret canines, preparation depth and bases were compared as to their effect on odontoblasts and to rate of dentin formation. These were measured by injecting 3H-proline at 0, 20 and 40 days post-preparation. Odontoblast activity was determined by label density in each band; inter-band distances indicated the amount of dentin formed. Correlations were by Pearson's coefficient. The following were determined: 1) cavity depth (remaining dentin thickness) was the major factor in odontoblast response and in dentin formation; deeper cavities suppressed odontoblasts with less subsequent dentin formation at all time periods; 2) basing materials had little effect on odontoblast activity or on the rate of dentin formation. An exception was in deep cavities, with Ca(OH)2 showing more label; this activity was temporary with no increased dentin formation; 3) there was no evidence of a "rebound" response.

Animals↗
PubMed1991

Computerized occlusal analysis: an evaluation of the sensors.

Dentists traditionally depend on their experiences to evaluate occlusion. A computerized system, that enables an objective analysis of dental occlusion has been developed and is currently available. A key component of the system is the disposable sensor. This research tested the sensors' validity and reliability in detection of known interceptive occlusal contact and discovered that the sensors were valid when used just twice.

Analysis of Variance↗
PubMed1991

The effect of powder/liquid ratio on the in vivo solubility of polycarboxylate cement.

A clinical study of the solubility of three powder/liquid ratios of polycarboxylate cement demonstrated a threefold increase in the solubility for the lower powder/liquid ratios. The three liquid/powder ratios tested were within the range recommended by the manufacturer. The data suggest that the higher powder/liquid ratio (1.5:1) is preferable when minimal solubility is a primary requirement.

Crowns↗
PubMed1991

A 14-year clinical assessment of 12 amalgam alloys.

After 14 years, 40 patients from an in vitro/in vivo study of 12 amalgam alloys were evaluated. All these patients had been attending private practitioners over the past 10 years, and the clinical evaluation revealed that 320 restorations were intact and 47 (12.8%) had been lost. The majority (75.0%) of the lost restorations were lost to crown placement or the replacement with another amalgam restoration. The six high-copper alloys exhibited better clinical performance, in both loss rate and fracture at the margins, than did traditional low-copper materials. Fracture at the margins was a better predictor of the loss of a restoration than were mechanical properties.

Copper↗
PubMed1990

13-year clinical assessment of 10 amalgam alloys.

The first commercial high-copper amalgam was developed in the mid-1960's. In 1975, a study to evaluate in vivo/in vitro performance of nine of these new alloys was initiated at Indiana University. These nine high-copper amalgams plus a traditional amalgam were tested for four laboratory properties and their gamma-2 content, and were clinically assessed for fracture at the margins. Originally, 60 restorations of each material were placed in patients and then recalled at six, 12, and 24 months. Recently, 13 years post-operatively, approximately one-third of the original patients were located. These patients were given a clinical exam, and photographs were taken of their restorations. From these recall data, the mean loss of all restorations at 13 years was 11.3%. The alloys Cupralloy, Tytin, and Dispersalloy had the lowest loss rates. The evaluation of the fracture at the margins (ridit means) indicates that there are five groups of alloys with some overlap between groups. The alloys Cupralloy, Indiloy, Dispersalloy, and Phasealloy exhibited the least fracture at the margins. The gamma-2-containing alloys--Optaloy II, Micro II, Velvalloy, and Aristaloy CR--showed the greatest rate of fracture at the margins. A correlation matrix of the ridit means at different years, the loss of restorations at 13 years, and the mechanical properties indicate that the early (one- and two-year) fracture at the margins predicts the 13-year results. Mechanical properties, however, do not predict the clinical performance of the materials at 13 years.

Copper↗
PubMed1990

The prevalence and severity of late effects in normal rat duodenum following intraoperative irradiation.

In humans, a portion of the duodenum is often at risk for radiation-induced complications following intraoperative radiation therapy for pancreatic carcinoma. To determine experimentally the prevalence and severity of late effects in the normal mammalian duodenum, 190 rats received single doses of 0, 15, 20, 25, 30, or 40 Gy orthovoltage X rays to temporarily exteriorized 3 cm circumferential segments of duodenum. The animals were killed 2, 6, 8, or 10 months later. Actuarial survival, change in body weight, and a radiation injury score based on eight histopathologic alterations were used as endpoints. Epithelial atypia, intestinal wall fibrosis, serosal thickening, and vascular sclerosis were the dominant histopathologic alterations at all dose levels throughout the 10-month observation period. The prevalence and severity of histologic radiation injury showed sigmoidal dose-response relationships with the plateaus starting at 20 Gy. Doses of 20 Gy or greater also resulted in a substantial loss of body weight and a high level of early deaths (20-80 days). All endpoints indicate that intraoperative doses of 20 Gy or greater are associated with unacceptable risks of late and irreversible complications.

Animals↗
PubMed1990

Relationship of restoration width, tooth position, and alloy to fracture at the margins of 13- to 14-year-old amalgams.

The effect of width of the restoration, tooth position, and amalgam type on the fracture of the margins of 13- to 14-year-old, high-copper, amalgam restorations was evaluated. The evaluation assessed 193 photographs of restorations by use of ridit analysis and a rank-ordering test. The results indicated that the width of the restoration was the predominant factor and that tooth position and the different high-copper alloys were less significant. Interactions between tooth position and width indicated that lower premolars with conservative restorations exhibited the least fracture at the margins, and upper premolars with a wide preparation exhibited the most. It is postulated that tooth deflection under mastication may play a role in long-term fracture at the margins of amalgams.

Analysis of Variance↗
PubMed1990

Intestinal complications following accelerated fractionated x-irradiation. An experimental study in the rat.

Due to paucity of suitable animal models, it has been difficult to study the development of long-term intestinal complications following fractionated irradiation. We recently developed a model which allows multiple radiation exposures of a short segment of rat ileum without the need for repeated surgery. In the present series, this model was used to study the influence of shortening the total treatment time (accelerated fractionation) on development of radiation enteropathy. Male rats were orchiectomized and a short segment of distal ileum was transposed to the scrotum. Starting 3 weeks after surgery, the scrotum containing the intestinal segment was x-irradiated with 20 fractions of 2.8 Gy (total dose 56 Gy). Two fractionation schedules were compared: One fraction per day (total treatment time 26 days) and 3 fractions per day (total treatment time 7 days). Actuarial survival curves were obtained, and the degree of radiation injury was assessed 2, 8, and 26 weeks after the last radiation exposure using a semiquantitative histopathologic scoring system. There was no mortality from acute radiation injury in either treatment group. All animals of the 1-fraction/day group survived the observation period (26 weeks). In the 3-fraction/day group, there was significant mortality due to intestinal obstruction, and cumulative mortality at 26 weeks was 100%. Radiation injury, as assessed by the histopathologic scoring system, was also more pronounced in this group than in the 1-fraction/day group. We conclude that shortening the total treatment time significantly increases the severity of late intestinal complications. Our data are suggestive of an association between acute mucosal damage and chronic radiation injury of the small intestine.

Animals↗
PubMed1990

Three-year clinical performance of eight amalgam alloys.

Eight amalgam alloys were clinically assessed for fracture at the margins and tarnish after 3 years. The amalgams that exhibited the least fracture at the margins were Epoque. Dispersalloy and Amalcap. The alloys Permite, Lojic and Tytin followed closely behind and the materials Arjalloy and Futura showed the greatest amount of breakdown. Tytin had the highest luster with Lojic and Futura having a generally dark surface after 3 years clinical service. Of the 260 restorations, six had been lost due to (a) tooth fracture (three restorations), (b) bulk fracture of the amalgam (two restorations), and (c) endodontic treatment (one restoration).

Dental Amalgam↗
PubMed1990

3-year clinical evaluation of glass ionomer cements as Class III restorations.

Two glass ionomer restorative materials, Chelon and Ketac-Fil were placed in Class III cavity preparations and compared to a conventional composite resin. Patients were recalled at 6 months, 1 year, 2 years, and 3 years for evaluation using the USPHS-Ryge criteria. The glass ionomer cements compared favorably to the composite resin in color match, anatomic form, and caries rate, but did exhibit substancial cavosurface discoloration and marginal deterioration. However, post-operative sensitivity was not evident, and no restorations required replacement during the 3 years.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1990

A 12-year clinical evaluation of two composite resins.

Two composite resin materials were clinically evaluated after 12 years in vivo. Although the Class III restorations did not have the benefit of acid etching and bevels, all 32 restorations in the nine patients who were located were intact, and none needed to be replaced. Stain was the most prominent problem, both at the margins and on the surface of the restorations. Neither wear or marginal integrity appeared to be a problem.

Color↗