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Biomedical subjects

S O Hondrum

Publications and source records attributed to S O Hondrum.

At least 19 recordsLinked to original sources
PubMed2001

Changes in properties of nonaqueous elastomeric impression materials after storage of components.

STATEMENT OF PROBLEM: Storage stability, or shelf life, is a critical property of perishable dental materials. PURPOSE: The purpose of this investigation was to document changes in the properties of nonaqueous elastomeric impression materials over time and on exposure to various environmental conditions. MATERIAL AND METHODS: Materials investigated included a polyether impression material, a polysulfide material (light, regular, and heavy consistencies), and an addition-reaction silicone material (light, regular, heavy, and putty consistencies). Tests included viscosity of individual pastes, elastic recovery, working and setting times, strain in compression, dimensional change, creep compliance, and tear energy. Means and standard deviations were calculated for each test interval. Statistical analysis included 2-way ANOVA (variables: time and storage condition) and comparison to baseline values using 1-way ANOVA (variable: time) and Scheffe's multiple comparison test (P < or = 0.05) within each material, consistency, and test. RESULTS: Results over 72 months revealed changes in viscosity, working/setting times, elastic recovery, and creep compliance. Separation of components was seen with polysulfide and addition silicone materials. Some batches of polysulfide base paste and polyether reactor paste solidified in the tube. CONCLUSION: Most batches of the materials and consistencies tested remained efficacious well past their designated shelf lives under a variety of storage and use conditions. Data for the addition-reaction silicone impression material changed little during the 72-month testing period; thus, the material may be considered relatively storage stable. Creep compliance was the most precise storage-stability indicator. The storage stability of perishable materials should be addressed in American Dental Association Specifications.

Analysis of Variance↗
PubMed2000

The comparative radiopacity of Fuji IX-GP, an intermediate restorative material.

The radiopacity of intermediate restorative materials should be sufficient to enable the clinician to distinguish the material from normal and decalcified tooth structure. The purpose of this study was to determine the relative radiopacities of intermediate restorative materials, including a newly introduced high-viscosity, self-cured, condensable glass ionomer material. Radiographs were made of six intermediate restorative materials: two reinforced zinc oxide-eugenol materials (IRM and Zinroc), a conventional glass ionomer material (Ketac-fil), a synthetic resin material (Cavit), a eugenol-free zinc oxide material (Tempit), and a new, general-purpose, condensable glass ionomer material (Fuji IX-GP). Optical density was measured using a densitometer. The optical density of dentin and enamel were used for radiographic comparison. Statistical analysis revealed significant differences among materials: Cavit = IRM = Tempit > Zinroc = Fuji IX-GP > Ketac-fil = enamel > dentin (where > indicates a statistical difference at p < or = 0.05). Although not as radiopaque as some other intermediate materials tested, the radiopacity of Fuji IX-GP appears sufficient to aid diagnosis.

Calcium Sulfate↗
PubMed1999

Storage stability of dental luting agents.

STATEMENT OF PROBLEM: Mechanical properties are considered to be important to the clinical success of dental cements. Storage time of dental luting agents (dental cements) before use and at the manufacturer may have substantial effects on their properties. PURPOSE: This study observed and investigated the changes in the properties of water-based dental luting agents over time and on exposure to various environmental conditions. METHODS AND MATERIAL: Properties of zinc phosphate, zinc polycarboxylate, and glass-ionomer luting agents were recorded at baseline and at intervals past 84 months, whereas the materials were exposed to controlled storage conditions as well as various conditions typical of clinical situations. Tests included viscosity, diametral tensile strength, ultimate compressive strength, rigidity, hardness, and working/setting times. RESULTS: Viscosity increased over 24 to 60 months for the acidic polymer liquids (zinc polycarboxylate and glass ionomer). Tensile and compressive strengths began to decrease after 36 months for all cements, most acutely for glass ionomer. CONCLUSION: Changes in critical properties on aging may not be noticed by the clinician and yet may impact clinical success. These data emphasize the importance of storage stability for perishable dental materials and portend the need for standardized tests.

Analysis of Variance↗
PubMed1998

Resin to metal bond strengths using two commercial systems.

STATEMENT OF PROBLEM: A secure bond between resin and an alloy framework is necessary for clinical success in removable prosthodontics. PURPOSE: This study compared the shear bond strength of composite to composite to metal with two commercially available chemical bonding systems: a silicoating system (Silicoater) and a nitrogenous heterocycle-acrylonitrile system (Kevloc). MATERIAL AND METHODS: Fifty-two nickel-chromium cubes were cast and composite resin was bonded to the alloy surfaces according to manufacturer's directions. After storage at 35 degrees C for 15 days, and thermocycling at 5 degrees C and 55 degrees C for 1200 cycles, the bonds were fractured in shear on a universal testing machine. RESULTS: Mean bond strength for the silicoated sample was 10.93 MPa and for the heterocycle-acrylnitrate system 11.44 MPa. An unpaired t test revealed no difference between the groups (p = 0.60). Visual inspection of the fracture surfaces revealed that failure was adhesive at the resin-to-metal surface in almost all the specimens.

Acrylonitrile↗
PubMed1998

Effects of joint configuration for the arc welding of cast Ti-6Al-4V alloy rods in argon.

STATEMENT OF PROBLEM: Titanium and its alloys are more commonly used in prosthodontics and welding has become the most common modality for their joining. Studies on the welding of titanium and its alloys have not quantified this value, though its importance has been suggested. PURPOSE: This study compared the strength and properties of the joint achieved at various butt joint gaps by the arc-welding of cast Ti-6Al-4V alloy tensile bars in an argon atmosphere. MATERIAL AND METHODS: Forty of 50 specimens were sectioned and welded at four gaps. All specimens underwent tensile testing to determine ultimate tensile strength and percentage elongation, then oxygen analysis and scanning electron microscopy. RESULTS: As no more than 3 samples in any group of 10 actually fractured in the weld itself, a secondary analysis that involved fracture location was initiated. There were no differences in ultimate tensile strength or percentage elongation between specimens with weld gaps of 0.25, 0.50, 0.75, and 1.00 mm and the as-cast specimens. There were no differences in ultimate tensile strength between specimens fracturing in the weld and those fracturing in the gauge in welded specimens; however, as-cast specimens demonstrated a higher ultimate tensile strength than welded specimens that fractured in the weld. Specimens that fractured in the weld site demonstrated less ductility than those that fractured in the gauge in both welded and as-cast specimens, as confirmed by scanning electron microscopy examination. The weld wire showed an oxygen scavenging effect from the as-cast parent alloy. CONCLUSIONS: The effects of the joint gap were not significant, whereas the characteristics of the joint itself were, which displayed slightly lower strength and significantly lower ductility (and thus decreased toughness). The arc-welding of cast titanium alloy in argon atmosphere appears to be a reliable and efficient prosthodontic laboratory modality producing predictable results, although titanium casting and joining procedures must be closely controlled to minimize heat effects and oxygen contamination.

Alloys↗
PubMed1998

Die stone disinfection: incorporation of sodium hypochlorite.

PURPOSE: Previous research has shown that dental gypsum casts may be effectively disinfected by the substitution of 10% of the gauging water with 5.25% solution of sodium hypochlorite. The purpose of this investigation was to determine the properties of gypsum produced from such a solution as opposed to tap water alone. MATERIALS AND METHODS: Tests included setting time, compressive strength, rigidity, diametral tensile strength, setting expansion, hardness, and detail reproduction. RESULTS: The addition of sodium hypochlorite to the gauging water resulted in a statistically significant increase in the compressive strength and rigidity, and a decrease in setting time (p < or = .5). All other properties remained unchanged. CONCLUSIONS: This substitution may be an effective and convenient method of disinfecting gypsum casts in the laboratory without adversely effecting physical and mechanical properties.

Calcium Sulfate↗
PubMed1998

Temporary dental restorative materials for military field use.

New temporary dental restorative materials are an important military requirement. This study compares the critical properties of the currently used temporary material, reinforced zinc oxide-eugenol (ZOE), with those of a glass ionomer restorative material (GI), a high-viscosity modified glass ionomer material (MGI), and two resin-modified glass ionomer materials (RMGIs). Properties tested included compressive and tensile strength, rigidity, hardness, bond strength, working and setting times, and storage stability. Ranked results for compressive strength, rigidity, and hardness were MGI > GI > RMGI > ZOE; for tensile strength they were RMGI > MGI > GI > ZOE; and for storage stability they were ZOE > MGI > GI > RMGI. Working and setting times were all within reasonable clinical limits, and bond strength was heavily dependent on tooth surface preparation. Although none of the materials tested met all of the ideal requirements, the high-viscosity glass ionomer material offers the most promise for military field use.

Composite Resins↗
PubMed1997

Effects of long-term storage on properties of an alginate impression material.

STATEMENT OF PROBLEM: Storage stability is a critical characteristic for perishable dental materials. PURPOSE: The purpose of this shelf-life study was to document changes in the properties of an alginate impression material on exposure to various environmental conditions for more than 78 months. MATERIAL AND METHODS: Properties measured included recovery from deformation, strain in compression, compressive strength, tear strength, working time, and creep compliance. RESULTS: Results revealed increases in strength and working time and a decrease in recovery from deformation at 30 to 50 months: strength and recovery then remained constant past 6 years, whereas working time and creep compliance decreased. Only the most stressful environmental conditions (heat and humidity) caused spontaneous failure of the material to set. CONCLUSIONS: We concluded that, under most storage conditions, properties of the alginate material tested remain within ADA specification limits well past manufacturer's designated shelf life. ADA specifications should require manufacturers to verify that the shelf life of each perishable material is based on valid data. An accelerated aging test was developed to simulate real time property changes and to assist in evaluating similar materials.

Alginates↗
PubMed1997

Resiliency of surface-sealed temporary soft denture liners.

STATEMENT OF PROBLEM: Studies have suggested that coating a temporary soft denture liner with a semiset methyl methacrylate resin extends the period of resiliency of the liner. PURPOSE: This study determined whether coating three temporary soft denture liners with two different denture surface sealants, followed by thermocycling, affected the resiliency of the liners. MATERIAL AND METHODS: thirty 20 x 12.5 mm cylindrical samples each of Lynal, Coe Soft, and Visco-Gel soft lining materials were prepared and divided into three groups of 10 uncoated samples, 10 Palaseal-coated samples, and 10 mono-poly coated samples. Samples were thermocycled from 5 degrees C to 45 degrees C for 500 cycles and then compressed 10 mm on an Instron universal testing machine. Resiliency was determined by measuring the energy absorbed by the soft liners when stressed to a specific yield point. RESULTS: Two-way ANOVA indicated a significant difference among materials (p = 0.0001) and among treatments (p = 0.0001). One-way ANOVA of each material group revealed a significant difference among Lynal groups (p = 0.0001) and a significant difference among Visco-Gel groups (p = 0.030). CONCLUSIONS: Surface-coating Lynal samples with Palaseal or mono-poly and Visco-Gel samples with Palaseal significantly increased the resiliency of these samples in the laboratory when compared with uncoated samples.

Absorption↗
PubMed1997

Force decay and deformation of orthodontic elastomeric ligatures.

This study evaluated commercially available molded gray elastomeric ligatures from seven companies for force decay, dimensional change, and the relationship between ligature dimension and force. The initial wall thickness, inside diameter, outside diameter, and force levels of each ligature were measured. Three of four test groups of ligatures were stretched over stainless steel dowels with a circumference approximating that of a large orthodontic twin bracket. Test group 1 was kept at room temperature and humidity for 28 days and test group 2 in a synthetic saliva bath at 37 degrees C, pH 6.84 for 28 days. The residual forces and dimensional changes were measured. The third test group was placed in a synthetic saliva bath at 37 degrees C, pH 6.84, and force levels recorded at initial, 24 hours, 7 days, 14 days, and 28 days. The fourth test group of unstretched samples was placed in a synthetic saliva bath at 37 degrees C, pH 6.84 for 28 days to evaluate dimensional changes due solely to moisture sorption. The results for stretched samples in a simulated oral environment revealed the following: (1) Moisture and heat had a pronounced effect on force decay and permanent deformation, (2) a positive correlation existed between the wall thickness and force, (3) a negative correlation existed between the inside diameter and force, (4) a weak correlation existed between outside diameter and force, (5) the greatest force loss occurred in the first 24 hours and the decay pattern was similar for all ligatures tested, and (6) unstretched ligatures absorbed moisture in the range of 0.060% to 3.15%. The ligatures tested appear to be suitable for use during initial aligning and leveling. However, the rapid force loss and permanent deformation of these products may preclude their use for rotational and torque corrections.

Analysis of Variance↗
PubMed1996

The relationship between pH and concentrations of antioxidants and vasoconstrictors in local anesthetic solutions.

pH affects the efficacy of local anesthetics by determining the percentage of the lipid-soluble base form of the anesthetic available for diffusion and penetration of the nerve sheath. The purpose of this study was to determine the relationship between pH and the concentrations of antioxidant and vasoconstrictor in dental local anesthetic solutions over real-time and after accelerated aging. Several batches of lidocaine and mepivacaine with vasoconstrictors were tested. Results showed that, immediately upon receipt from the manufacturers, three batches were below the USP pH limit (pH 3.3), and two batches contained less than the minimum limit of vasoconstrictors (90%). Real-time tests on batches that were within normal limits revealed that solutions were stable past 4 yr. Accelerated aging tests revealed a strong correlation between a decrease in pH and loss of antioxidants and vasoconstrictors. In conclusion, a quality batch of local anesthetic should remain efficacious long past the manufacturer's stated shelf life; a batch that is less than optimal, or one that is exposed to environmental stresses, will degrade rapidly, and efficacy may be affected by decreases in pH and loss of vasoconstrictor. pH may be an inexpensive, readily available screening test for efficacy of local anesthetics.

Anesthetics, Local↗
PubMed1995

A three-dimensional comparison of condylar position changes between centric relation and centric occlusion using the mandibular position indicator.

The mandibular position indicator (MPI) was used to compare condylar position between centric relation (CR) and centric occlusion (CO) for 107 patients before orthodontic treatment. The MPI data were examined to determine frequency, direction, and magnitude of CO-CR difference; and data were analyzed for possible correlation to the patient's Angle classification, ANB angular measurement, age, or gender. Only one patient (0.9%) had no measurable CO-CR difference in all three spatial planes. Six subjects (5.6%) showed a shift in condylar position in the transverse plane without a measurable difference in the sagittal plane. Twenty patients (18.7%) experienced a superoinferior (SI) or anteroposterior (AP) condylar displacement of at least 2.0 mm on one or both sides; 17 (15.9%) displayed a transverse shift at the level of the condyles of 0.5 mm or greater. No statistical difference was found between the 31 patients with Class I malocclusions and 72 patients with Class II malocclusions when comparing the amount or direction of CO-CR change. The amount of CO-CR difference was nearly identical for right and left sides with the amount of SI displacement (x = 0.84 mm) consistently greater than AP displacement (x = 0.61 mm). Only weak correlations were found between movements of right and left condyles. The average transverse CO-CR difference was 0.27 mm. Patient age, ANB angle, gender, or Angle classification cannot be used to predict frequency, magnitude, or direction of CO-CR changes at the level of the condyles.

Adolescent↗
PubMed1994

Mechanical and bond strength properties of light-cured and chemically cured glass ionomer cements.

The purpose of this study was to evaluate the mechanical and bond strength properties of a commercially available light-cured glass ionomer cement and of a chemically cured glass ionomer cement. Sixty recently extracted human molars were randomly divided into six equal groups, and the bond strengths of the two cement types were evaluated at 1 hour, 24 hours, and 7 days. Stainless steel lingual buttons were bonded to prepared enamel surfaces, and the samples were placed in a water bath at 37 degrees C until testing. The shear bond strength of each sample was determined with a universal testing instrument. The mechanical strength properties of the two cements were then evaluated. The transverse flexural strength, compressive strength, rigidity, and diametral tensile strength were tested for each cement at 1 hour, 24 hours, and 7 days. The results of the mechanical property strength tests were then compared with the results of the bond strength tests.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1993

Stability of local anesthetics in the dental cartridge.

Recent manufacturer recalls of local anesthetics have emphasized the problems with storage stability. This article reviews the principles of drug stability, mechanisms of degradation of commonly used vasoconstrictors, research on the stability of commercially produced local anesthetic preparations, and possible effects of the container-closure system. The review concludes with a list of practical and clinical suggestions on how to minimize storage stability problems with dental local anesthetics.

Anesthesia, Dental↗
PubMed1992

A review of the strength properties of dental ceramics.

New ceramic materials for restorative dentistry have been developed and introduced in recent years. This article reviews advantages and disadvantages of dental ceramics, concentrating on strength properties. Included are factors affecting the strength of dental ceramic materials and the most common mechanisms for increasing the strength of dental ceramics. The properties of presently available materials such as dispersion-strengthened ceramics, cast ceramics, and foil-reinforced materials are discussed. Current research efforts to improve the fracture resistance of ceramic restorative materials are reviewed. A description of methods to evaluate the strength of ceramics is included, as a caution concerning the interpretation of strength data reported in the literature.

Ceramics↗
PubMed1992

Comparison of the shear bond strength of a light-cured glass ionomer and a chemically cured glass ionomer for use as an orthodontic bonding agent.

Light-cured glass ionomers with an initial set of 20 seconds may produce higher initial bond strengths, as well as decreased sensitivity to moisture contamination and desiccation, than chemically cured glass ionomers making them attractive for use as orthodontic bonding agents. The purpose of this study was to determine and compare the shear bond strength of stainless steel orthodontic attachments to enamel with a light-cured glass ionomer (Zionomer) tested at 60 minutes and 24 hours, and a rapidly setting chemically cured glass ionomer (Ketac-Bond) tested at 60 minutes and 24 hours. Fifty-two recently extracted human premolars were randomly divided into four groups--1-hour and 24-hour light-cured glass ionomer groups and 1-hour and 24-hour chemically cured glass ionomer groups. Stainless steel lingual buttons were bonded to prepared enamel surfaces, and the samples were placed in a water bath at 37 degrees C until ready for testing. The shear bond strength of each sample was determined with a universal testing instrument. Results from the study conclude: (1) The mean shear bond strength of the light-cured glass ionomer is greater than that of the chemically cured glass ionomer at 1 and 24 hours. (2) The mean shear bond strength of both glass ionomers increases from 1 to 24 hours. (3) The mean shear bond strength of the light-cured glass ionomer is not significantly different from 1 to 24 hours, but the shear bond strength of the chemically cured glass ionomer cement is different.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Etching, Dental↗
PubMed1991

The U.S. Army Institute of Dental Research dental materials shelf-life survey: questionnaire results.

To define the nature and the extent of problems that can be related to the storage stability of perishable dental materials in the U.S. Army, questionnaires were sent to each U.S. Army Dental Corps Officer, supply NCO, and laboratory technician. Results reveal that two-thirds of dentists believe that the deterioration of perishable materials is a significant (28%) or occasional (39%) problem in their practice; the most common problem noted by dental clinicians is loss of efficacy of local anesthetics. One-half of clinicians and supply personnel report that they frequently receive perishable supplies at or near the expiration date.

Dental Materials↗