Search PubMed⌕ Search

Biomedical subjects

J D Preston

Publications and source records attributed to J D Preston.

At least 37 records · Page 2Linked to original sources
PubMed1987

Perceived or actual overlap between the scope of prosthodontics and other recognized dental specialties.

Prosthodontics does not overlap with other specialties but is integrated with them. This essential difference between "overlap" and "integration" should be made abundantly clear. No one denies that most of the population's dental needs must be served by the general practitioner, and no specialist can be completely capable within even his or her own specialty. Nevertheless, the prosthodontist, as all specialists, must assume the role of treating patients who require unusual care. It is the prosthodontist who most frequently assumes the primary role in the management of patients who require complex, demanding restorative care, and it is the prosthodontist who has the most intimate understanding of the proper diagnosis, treatment planning, integration of therapy, patient management, and aftercare for these patients.

Attitude of Health Personnel↗
PubMed1982

Measurement of paint-on die spacers used for casting relief.

Three paints used for die spacing were measured for film thickness. Two of the materials are marketed as die spacers, and the third is sold as a model airplane paint. The materials were applied to stone dies in multiple coats. They were embedded in resin, sectioned, and measured photographically through a microscope. The three die spacing materials were capable of achieving clinically acceptable relief in the range of 20 to 40 mu by using a variable number of coats. Different paints produced different thicknesses. The two paints sold specifically for die spacing gave 11 to 13 mu per coat. The hobby shop paint had the smallest film thickness per coat, yielding approximately 5 mu per layer. It also had the smallest standard deviation. This control plus the relative low cost and availabilty make it attractive for this purpose.

Cementation↗
PubMed1982

Effect of oxidation on ceramometal bond strength.

The ceramometal bond strength between SMG-3 gold alloy and Ceramco porcelain was evaluated using seven different oxidation cycles. The control group was not oxidized. Three groups were oxidized under vacuum at a temperature of 1,925 degrees F. The metal was heated (1) just until it reached temperature, (2) for 5 minutes, and (3) for 10 minutes. The last three groups were oxidized without a vacuum, with the time-temperature heat regimen the same as for the previous three groups. The group using an oxidation cycle without a vacuum and a temperature of 1,925 degrees F for 10 minutes was the only group that statistically differed from the control group.

Chemical Phenomena↗
PubMed1982

Post-ceramic soldering of various alloys.

A base metal alloy was soldered to precious and semiprecious alloys using a post-ceramic soldering technique. The specimens were tested by the tensile mode and the results statistically analyzed. The solder joints involving the base metal had strengths comparable to the precious and semiprecious joints. However, a high percentage of the base metal joints were too weak to be tested. Further study using other solders is indicated.

Dental Alloys↗
PubMed1980

An investigation of epoxy resin dies.

1. Complete crown epoxy resin dies are undersized. 2. MOD onlay epoxy resin dies are accurate. 3. Detail duplication of epoxy resin dies is comparable to that of die stone. 4. Hardness values of epoxy resin are generally less than those of die stone. The hardness of Epoxydent closely approached that of die stone.

Calcium Sulfate↗
PubMed1979

A reassessment of the mandibular transverse horizontal axis therory.

1. Within the limits of accuracy imposed by individual operators, equipment, and patient variations, a single transverse horizontal axis can usually appear to be located. 2. Location of a kinematic axis is worthwhile clinical procedure to transfer an arc of rotation in the sagittal plane from the patient to an articulator. 3. Past experiments have been useful, but none have proved or disproved the presence of colinear or noncolinear condyle arcs. Only the arc of the rigid clutch and its associated mechanism is located. Such an apparent arc may result from the resolution of compound condylar movements. 4. The right angle-nonright angle concept is misleading and generally is not applicable to clinical procedures. 5. The anatomic asymmetries of the axis transfer procedure may result in cast dislocations that may produce undesirable alterations in esthetic tooth positions. 6. The single transverse horizontal axis as a fact in articulating instruments and as a theory in the human craniomandibular complex. 7. The terms "transverse horizontal mandibular axis" and "intercondylar axis" should not be confused or used as synonyms. The term "transverse horizontal mandibular axis" ("hinge axis") should be used instead of "condylar" or "intercondylar" axis.

Cephalometry↗
PubMed1979

Preventing ceramic failures when integrating fixed and removable prostheses.

The successful integration of fixed and removable units requires diagnostic skill, careful planning, and adherence to detail in execution. Failures can be either in function or esthetics, may occur in either the fixed or removable segment, and can be catastrophic or insidious. Success demands that all the customary requirements for each independent unit, fixed or removable, be met and then the additional requirements for integration be ascertained and fulfilled. In such situations there are an exponentially greater number of possibilities for failure. When the dentist is alert to the potential for failure he may intercept and prevent it. Meticulous care pays long-term dividends in the lasting satisfaction of a patient who enjoys imporved masticatory performance, preservation of the existing tissues, and self-confidence borne from a smile that does not reveal differences between the natural and the simulation of nature. The integration of fixed and removable units is another manifestation of the skillful blending of science and art.

Ceramics↗
PubMed1978

Light and lighting in the dental office.

For any task, the eye can respond effectively if there is enough light, if that light is properly distributed, if the appropriate color correction is provided, and if visual contrasts are balanced. Dental offices differ in the types of work performed, the number of people engaged in various tasks, and the types of patients treated. Each office and each room can be planned according to the guidelines herein suggested as long as a rational analysis is applied to the result desired and the tasks being accomplished. The authors suggest that all concerned with office design, the architect, the contractors, and even other illuminating engineers be asked to read this article before integrating their efforts, for the dental office presents some variations not frequently encountered by these people. The need for conservation of our energy sources mandates wise use of all our energy expenditures. There is another resource conservation need that is sometimes overlooked--the effective use of talented people such as the dentist and his staff. The employment of adequate illumination design heeds both demands while giving a rewarding pleasantness and enjoyment of the work environment.

Age Factors↗
PubMed1976

A systematic approach to the control of esthetic form.

A systematic, orderly approach to the problem of establishing harmonious phonetics, esthetics, and function in fixed restorations has been described. The system requires an initial investment of time in performing an adequate diagnostic waxing, but recoups that time in many clinical and laboratory procedures. The method has proved a valuable asset in fixed prosthodontic care. The technique can be expanded and combined with other techniques with a little imagination and artistic bent.

Denture Design↗
PubMed1975

Preceramic and postceramic solder joints.

This investigation evaluated preceramic and postceramic soldering procedures. Three gap spaces and two soldering methods were evaluated. Wider gaps produced stronger joints. The strongest joints were achieved by using wider gaps and the oven soldering technique. Very wide gaps (0.76 mm.) are not recommended because of possible distortion through excessive solder shrinkage. However, in practice, many solder joints exceed the 0.31 mm. recommended minimum; these joints will not show decreased strength.

Ceramics↗