PubMed Health⌕ Search

Biomedical subjects

J A Stackhouse

Publications and source records attributed to J A Stackhouse.

14 recordsLinked to original sources
PubMed1989

Effect of substrate condition and substituted phenols and methacrylates on toluene diisocyanate/dentin bond strengths.

One aim of this in vitro investigation was to determine the effect of substituting four phenols and two methacrylates with vinyl functions on the dentin bond strengths of several new experimental dentin bonding agents. Another objective was to determine the effect of postextraction age and dentin level within the tooth on tensile bond strengths of these toluene diisocyanate-derived adhesives. Extracted third molars were divided into postextraction age groups and sectioned into three slices approximately 400 microns thick. The four substituted phenols were: eugenol, o-methoxyphenol, o-chlorophenol, and p-cresol. Substituted methacrylates with vinyl ligands were 2-hydroxyethyl methacrylate (HEMA) and 6-hydroxyhexyl methacrylate (HHMA). Results showed that adhesives made with o-chlorophenol, p-cresol, and methoxyphenol with HEMA were the best, while those made with eugenol and HHMA were the worst. The post extraction age of the tooth and the dentin depth had no consistent effect on most adhesive bond strengths which were generally around 10.3 MPa (1500 psi).

Acrylates↗
PubMed1987

A study of bubbles in a rubber elastomer manipulated under clinical conditions.

One hundred addition reaction silicone impressions were made by students and faculty members using two types of syringes with two syringe tip sizes. A count of the bubbles in the impressions revealed a total of 439 with only one impression completely free of bubbles in either the posterior or anterior test regions. Faculty members, presumably more experienced, confirmed the last out-fewer bubbles hypothesis developed in a previous laboratory investigation, but some students did not. A pneumatically activated syringe produced no fewer bubbles than did the conventional hand-powered syringe but most of the students and faculty members thought it was advantageous. Half believed that more practice with it would be beneficial. We recommend that practicing dentists try to minimize bubbles by extruding the first part of the syringe contents onto the mixing pad or in a distant intraoral location before injecting around the critical tooth preparations.

Air↗
PubMed1985

Relationship of syringe-tip diameter to voids in elastomer impressions.

An in vitro study was done to determine the relationship between syringe-tip diameters and the number of bubbles in extruded strips of two vinyl silicone impression materials. Results disclosed the following. There were highly significantly fewer bubbles in impression material extrusions from the second half of the syringeful than from the first half (p less than .001). The smaller-tip orifices, 0.6 and 0.67 mm in diameter, caused highly significantly fewer bubbles in the extruded impression materials than did the larger tips (p less than .001). The reasons and clinical implications for these effects are unknown and are being explored. From subjective observations, it was concluded that the pneumatically powered syringe provided an easier means of extruding the impression material through small syringe-tip orifices than did the conventional hand-powered syringe.

Dental Impression Materials↗
PubMed1981

Impression materials.. and electrodeposits. Part I: Impression materials.

1. When compared to the master die, all five impression material specimens showed a shrinkage of from 0.07% to 0.23%. When used as substrates for electrodeposition, these dimensions partly predetermined the dimensions of the electrodeposits. (This will be discussed in Part II of this study). 2. When polymerized and maintained at room temperature, both President and Polyjel demonstrated a slight polymerization shrinkage then remained stable during a 3-week bench set. 3. When polymerized at higher temperatures, both President and Polyjel demonstrated considerable dimensional changes during the first hour as they cooled to room temperature then remained stable during the 3-week dry bench set. 4. President was little affected by a 5-hour immersion in an acid electroplating bath. 5. Polyjel, during 5 hours of immersion, tended to expand in both acid and alkaline electroplating baths.

Calcium Sulfate↗
PubMed1981

A study of interocclusal record materials.

An investigation of casts assembled by the use of seven interocclusal record materials and manipulated by three operators disclosed that: 1. Aluwax was the most variable and least reliable of all materials. 2. Superbite consistently resulted in open cast relationships. 3. The five elastomers consistently resulted in the least amount of errors. 4. The two different thicknesses of elastomeric records resulted in statistically significant different mounting discrepancies. 5. On an average, an inexperienced student performed as well as the two experienced dentists.

Dental Articulators↗
PubMed1981

Impression materials and electrodeposits. Part II: Electrodeposits.

1. Of 13 substrate/electrodeposit combinations tested, the six satisfactorily completed were modeling compound/copper, Permlastic/silver, Elasticon/nickel, Polyjel/silver, Polyjel/nickel, and President/copper. 2. The seven remaining substrate/electrodeposit combinations could not be completed because of pitting, discoloration, or high stresses within the electrodeposits. 3. In some instances, the electrodeposit dimensions were significantly different from those of the substrate. The combination with the largest substrate/electrodeposit difference was that of President/copper. 4. The combinations which demonstrated the least change from the master die were Polyjel/nickel and Elasticon/nickel. The completed nickel electrodeposits were not significantly different from each other nor from the master die. 5. The ultimate length of the electrodeposit in some combinations appeared to be dependent upon the substrate temperature, water sorption, polymerization shrinkage, and stresses within the electrodeposit. 6. These results contradict those who maintain that die inaccuracy is due solely to the impression material and support those who believes that both the impression material and the electrodeposit itself can contribute to die inaccuracy.

Chemical Phenomena↗