Dale E. Grenoble

Elastic Properties of Dental Resin Restorative Materials

The elastic constants of several commercially available filled and unfilled dental resin restorative materials were determined in the 0 to 50 kilobar range of pressure. Measurements of the velocities of propagation of longitudinal and shear ultrasonic waves were used to obtain the Youngs, bulk, and shear moduli and Poissons ratio as a function of pressure; atmospheric pressure values were obtained by back extrapolation from the high pressure data.

Mathematical Modeling and Structural Analysis of the Mandible

The article presents details of mathematical modeling and subsequent structural analysis of the mandible under occlusal load simulation. A three-dimensional model of the mandible has been developed and analyzed using the finite element displacement matrix approach. Both displacement and stress results are presented. The results are compared with tests of a human mandible using holographic inferferometry. The good agreement achieved indicates that the modeling technique is reliable, thereby paving the way to applying the same for detailed dental implant analysis.

Elastic Constants of Three Representative Dental Cements

Ultrasonic techniques at high pressures were used to measure and compare the elastic properties of representative zinc phosphate, zinc silico-phosphate, and silicate cements. High pressures were used to suppress porosity to obtain effective elastic moduli at ideal density. Specimens were prepared from commercially available products according to the manufacturers directions; the three cements used herein were produced by a single manufacturer.* The materials were processed in a cylindrical die, 1 cm in diameter and 3 to 4 mm thick; hand condensation pressures were applied with an amalgam condensing instrument. Samples were allowed to set for seven days before measurements were taken. The velocities of transmission of longitudinal and shear ultrasonic waves were measured with an ultrasonic interferometer and a solid media, high pressure apparatus (AHRENS and KATZ, J Geophys Res 67:2935-2944, 1962). Computer analysis yielded the bulk, shear, and Youngs moduli and Poissons ratio; atmospheric pressure values were obtained by back-extrapolation from the high pressure data. The elastic moduli of these cements as a function of pressure, from atmospheric pressure to 50 kilobars (735,000 psi), are plotted in the illustration. In the table the elastic constants at atmospheric pressure are compared to corresponding values for filled and unfilled resins (NAKCAYAMA, HALL, GRENOBLE, and KATZ, unpublished results) and amalgam (GRENOBLE and KATZ, J Biomed Mat Res 5:489-502, 1971), which were measured in the same way, as well as to the elastic constants of human enamel and dentin (CRAIG, PEYTON, and JOHNSON, J Dent Res 40:936-945, 1961), measured by mechanical methods, and human enamel (REICH, BRENDEN, and PORTER,

Histologic Evaluation of Vitreous Carbon Endosteal Implants in Dogs

A 6-month histologic study of vitreous carbon dental implants in dogs, without occlusion, has demonstrated that vitreous carbon is well tolerated by oral tissues in both permucosal and subgingival applications. Gingival tissues heal routinely and show the same degrees of irritation adjacent to the implant as tissues adjacent to natural teeth. Alveolar bone forms within grooves in the implant surface, providing mechanical retention, and both hard and soft tissues grow into the texture in the implant surface. The resulting interlocking between tissues and the implant appears to function effectively as a bacterial seal. The newly formed bone within the implant grooves appears to become more dense with time, resulting in a layer of dense bone surrounding the implant. No foreign body responses and no inflammation were observed in tissues adjacent to this implant material, and no degradation of the vitreous carbon implants was detected. A subsequent study of the implant under occlusion in dogs is also being conducted.

Histologic Evaluation of Vitreous Carbon Endosteal Implants in Occlusion in Dogs

A 6-7 month histologic study of vitreous carbon endosteal implants in occlusion was conducted in dogs to determine whether the shape of the implant has adverse effects on supporting tissues. Conical vitreous carbon implants were placed in fresh, second, and third premolar extraction sites, and the sites were allowed to heal for periods of 2 to 8 weeks prior to restoration with cast gold crowns. Gingival tissues healed routinely and showed inflammatory conditions similar to tissues adjacent to teeth, and normal sulculur depths were measured. Bone formation was observed within grooves in the implant surface, providing retention and stabilization, normal bone remodeling appeared to be occurring adjacent to the implant sites. No inflammatory responses, foreign body reactions, or infections were observed. Vitreous carbon appears well suited for application as an endosteal implant material.

An Evaluation of VC 1800* as a Soft Tissue Replacement Material

Twenty rabbits were used in a study conducted to determine the soft tissue biocompatibility of vitreous carbon micro-balloons and spheres. Histologic observations were made at designated intervals of 24 hr; 4, 7, and 15 days; and 1, 2, 4, 6, and 8 months.The tissues were stained with hemotoxylin and eosin for microscopic observations. The findings showed that the implant material provoked minimal acute and chronic inflammatory response, which indicates that vitreous carbon is biocompatible and may serve as a soft tissue replacement material.No indication of the rejection phenomena was observed during the entire period of this implant study.

Instrumentation for placement of vitreous carbon endosseous implants.

The instruments required for placement, stabilization, and restoration of vitreous carbon endosseous implants are conventional in character and readily available. With the exception of extra-long burs for socket preparation, all instruments are normally available in dental offices. The surgery instruments should be rigorously sterilized prior to use, including the dental handpiece, burs, suction tip, etc. Gas sterilization techniques provide an effective means of sterilizing the surgical instruments without causing corrosion of burs and the handpiece.