Spectral studies of new luminophors for dental porcelain.

Luminescence spectra of several non-radioactive luminophors that may be suitable for dental porcelain have been obtained. It was found that porcelain composition and maturation temperature have large effects on excitation and emission spectra. Most of the luminophors had excitation maxima lower in wavelength than have been observed for natural teeth.

Suspension culture of myocardial cells from newborn rats.

Myocardial cells from newborn rats were held in a spinner type culture for 2 days and then explanted into culture flasks. Three main cell types were observed: single multipolar cells of embryonic type, cell aggregates containing 10 to 50 connected cells, and bipolar cells retaining some adult characteristics. Except for the latter, up to 95% of intact cells settled and were beating 6 hours after explantation.

Use of the Munsell system to compute color differences in composite resins.

Color changes resulting from immersion of four composite resins in hot distilled water, coffee and tea were measured by a tristimulus colorimeter. Changes are shown as CIE deltaE values and converted to Munsell deltaH, deltaV and deltaC values.

Tissue conditioners as functional impression materials.

Permanent deformation, strain in compression, flow, dimensional stability, reproduction of detail and gypsum compatibility of three commercial tissue conditioners (Coe-Comfort, FITT and Hydro-cast) and one polysulphide base Type I impression material (Coe-flex) were measured according to ADA Specification No. 19. Although the tissue conditioners generally exhibited higher deformations and lower gypsum compatibility than specified by ADA Specification No.

Mechanical properties of tissue conditioners. Part II: creep characteristics.

These static creep characteristics indicate that under functional loads Coe-Comfort could behave satisfactorily as a tissue-conditioning material for periods up to 1 week, particularly for the first 24 hours postinsertion. However, the absence of published data on the tissue loads exerted by dentures in their resting state precludes making judgments as to the absolute efficiency of any of these materials as tissue-conditioning agents. When the present results are considered along with those obtained in an earlier study (Part I), the following general conclusions can be made: 1.

Undercut reproducibility of functional impression materials (tissue conditioners).

Impressions of a laboratory model of an edentulous ridge were made with three commercial tissue conditioners (FITT, Hydro-Cast and Coe-Comfort). Combinations of undercut dimensions and tray relief were tested by using three different sized trays with each tissue conditioner. Greater tray relief increased the accuracy of all materials tested; increasing ageing time from 7 to 24 h resulted in little change of accuracy of the stone models poured from the impressions taken.

The rheological characteristics of elastomeric impression materials.

An indirect extrusion viscometer has been used to assess the shear rate dependence of viscosity of a range of pastes supplied for elastomeric impression materials. A suggested specification for these pastes has been proposed.

Semiprecious alloys for cast restorations: a preliminary report.

A previous clinical evaluation indicated that semiprecious metals had a definite place in the construction of dowels and cores in endodontically treated teeth. 2 The results from the present in vitro study suggest that those alloys do have a place in the fabrication of single castings as type III and IV gold alloy substitutes. Although when compared with a type III gold alloy the behavior of the semiprecious alloys tested was less like that of a noble alloy, the semiprecious alloys appeared less active than the base-metal alloy.

A colorimetric study of coffee and tea staining of four composite resins.

Colorimetric measurements were made on four composite resins before and after controlled immersion treatments. The four composite resins were: Adaptic (Johnson and Johnson), Prestige (Lee Pharmaceuticals), Addent XV (3M Mfg. Co.

A clinical evaluation of semiprecious alloys for dowels and cores.

The semiprecious metals investigated and hard dental gold alloys may be manipulated in a similar manner. The semiprecious metals produced accurate and well-fitted dowels needing minimal adjustment. Being harder than type III gold alloy, they would be ideal for casting dowels and cores.