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Biomedical subjects

J P Standlee

Publications and source records attributed to J P Standlee.

At least 19 recordsLinked to original sources
PubMed1992

The retentive and stress distributing properties of split threaded endodontic dowels.

A threaded, parallel-sided endodontic dowel that has a longitudinal split was tested to determine its retention and stress distribution properties. Photoelastic stress analysis revealed high installation stresses unless the dowels were counterrotated. Axial loading created stresses at the threads, with elevated coronal and apical stresses. Even higher coronal stresses were recorded with inclined loads, and shorter dowels generated greater stresses than longer dowels. The retentive values were generally lower than those in comparable studies.

Analysis of Variance↗
PubMed1992

Endodontic dowel retention with resinous cements.

This study compared the capability of three composite resin cements to sustain a standard endodontic dowel. All of the systems incorporated some form of smear layer removal on the dentin of the endodontic channel. One system that used a methyl ethyl ketone drying agent provided inadequate clinical resistance to dislodgment of 5.4 DaN. A second cementing system that used only smear layer removal resisted loads at 54.7 DaN. The third cementing regimen that included a surface-initiated dentinal adhesive and smear layer removal recorded retention of 77.4 DaN. This study supported the concept that passively cemented dowels with composite resin can be as effective as actively seated dowels.

Acrylic Resins↗
PubMed1988

Light cured composites.

Explore the source record for details and available documents.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1981

In vitro analysis of self-shearing retentive pins.

Combining stress, analysis, microscopic examination, mechanical testing of the shear mechanism, and retention of the Reten Pin leads to the following conclusions: 1. The suggested 0.006 inch pin-channel mismatch induces high lateral and apical stresses. Microscopically, this was seen to correlate with injury to the dentin. 2. The degree of retention was increased by using a smaller pin-channel mismatch. This correlates with smaller stresses and reduced dentinal damage. 3. The shear mechanism acts in a uniform manner, with a relatively small variation from the mean. It is suggested that for the best results the manufacturer should supply larger twist drills and pins with a somewhat deeper self-shearing groove to minimize apical involvement during shearing of the handle from the pin.

Dental Pins↗
PubMed1981

The condyle as a stress-distributing component of the temporomandibular joint.

Even though the temporomandibular joint is loaded in function, it often arthroses under heavy use. The effects of stress to the joint are not well understood. This study utilized three-dimensional photo-elastic stress analysis to visualize the intensity and direction of stress within the mandibular condyle generated by various occlusal forces. Functional stress were shown to concentrate in the condylar neck, but were reduced within the condylar head due to its elliptical shape. Stress directions within the condyle were found to be non-preferential, varying with different mandibular positions. This supports the idea that the condyle is designed to receive light varied forces rather than heavy, cyclical unidirectional forces.

Humans↗
PubMed1980

The retentive and stress-distributing properties of a threaded endodontic dowel.

When the Radix Anchor apex was allowed to engage the bottom of the prepared channel, very high apical stresses were generated within the supporting structure. When the coronal flanges engaged the occlusal portion of the model, high lateral stresses occurred in the coronal portion of the channel. These stress concentrations can be avoided by installing the dowel so that only the retentive threads engage dentin. This may be accomplished by "backing off" one half turn when slight resistance to dowel threading is encountered. The Radix endodontic dowel system was more retentive than cemented dowels and less retentive than another dowel which threads into the dentin of the channel wall. The Radix Anchor was more retentive when both diameter and length of imbedment were increased simultaneously.

Crowns↗
PubMed1979

Dowel retention with glass-ionomer cement.

The retentive capacity of the Whaledent Parapost system utilizing ASPA cement was compared at two lengths, three diameters, and with respect to the effect of both medication and citric acid pretreatment. The greatest single factor influencing retention was embedment depth into dentin. No significant differences were observed between the retention values for medicated and unmedicated teeth. Finally, no increase in retention was noted over previously reported values for zinc phosphate, carboxylate, and epoxy resin cements. The glass-ionomer cement tested offers no advantage for post retention.

Acid Etching, Dental↗
PubMed1978

Retention of endodontic dowels: effects of cement, dowel length, diameter, and design.

The retentive capacity of three preformed endodontic dowel designs was compared at two lengths and two diameters, with three different cements. The greatest single factor influencing retention of these devices was the design used. Of the types tested in this study, the most retentive were threaded, parallel-sided dowels screwed into tapped channels. Serrated, parallel-sided dowels cemented in matched cylindrical channels provided intermediate retention, and smooth-sided tapered posts were the least retentive. Another major factor in retention was the length of imbedment into dentin. An increase in dowel imbedment depth usually corresponded to increased retention. The effect of cement type was significant only with tapered dowels. Zinc phosphate cement was most retentive, carboxylate cement exhibited intermediate retention, and the epoxy cement was least retentive. For the other post designs, cement type had no significant effect on retentive capacity. Finally, variations in dowel diameter had no significant effect on retentive ability.

Crowns↗
PubMed1977

Stress trajectories within the mandible under occlusal loads.

A human mandible was duplicated in birefringent resin. The distribution and effect of occlusal forces within the mandible was demonstrated utilizing birefringent resin models compared to natural specimens. The results of this study reinforce those theories that assign function a major role in bone remodeling in the mandible. Further, the condyle is seen to be a stress-bearing structure.

Birefringence↗
PubMed1976

Pins and posts--why, when and how.

Pins and posts retain restorations and protect remaining tooth structure; they are indispensable to conservative operative dentistry. Effective utilization of these pin-post systems requires application of proper biomechanical principles for each clinical situation. No one design will suffice in every case. A parallel, serrated, cemented device in a precise matched channel is the ideal combination of characteristics. When tooth morphology or heavy function require increased retention, it may be achieved by increasing pin-post length, diameter, and number or by utilizing the resilience of dentin. However, the dentist must be aware that the price for more retention is the increasing risk of damaged tooth structure. Optimal long range results will be obtained by utilizing pins and posts in conjunction with veneer types of restorations. When used in this manner, they will save many teeth each year and simultaneously reduce the rate of failures.

Dental Pins↗