Indiana University-Purdue University Indianapolis (IUPUI) / Certain properties of a representative composite material were evaluated by in vitro testing and compared to those of other types of restorative materials. A clinical study designed to evaluate the performance of the composite material as compared to amalgam for Class II restorations was initiated and one-year results are reported. Laboratory tests for abrasion resistance, hardness, marginal leakage, strength, color stability, staining characteristics, solubility, and water sorption were conducted. The clinical study is still in progress but the results after one year indicated that the composite resin test restorations, as well as the amalgam control restorations, were generally satisfactory. In overall clinical performance neither material was superior to the other. The amalgam restorations received a superior rating for anatomic form while the composite restorations were superior in terms of marginal adaptation. No clinical evidence of recurrent caries, associated with any of the restorations, was detected. Surface discoloration was a significant finding on the composite restorations, but it was confined to proximal areas and may be related to the difficulty of cleaning these areas with a toothbrush. No conclusions can yet be made regarding the long-term clinical performance of the composite resin used in this investigation as a Class II restorative material.

Indiana University-Purdue University Indianapolis (IUPUI) / This clinical study evaluated the effects of conditioning agents for pit and fissure sealants on the bacteria present in occlusal grooves and fissures in permanent molars. The conditioning agents, 50 percent phosphoric acid and 50 percent phosphoric acid attenuated with 7 percent zinc oxide, with distilled sterile water being used as a control, were compared for their ability to kill bacteria in carious occlusal lesions. Eighty-six teeth from children eight to twelve years of age were conditioned with one of the randomly assigned agents using a blind method to prevent bias. The teeth were then cultured with a method that measured results as to growth or no growth after incubation. The culturing was done at both the occlusal surface and the depth of the lesion. A chi square test demonstrated that there were no significant differences between the conditioners on either the occlusal or depth of the lesion cultures (x2 = .31, df = 2, a = .05). The two conditioners did not totally kill the bacteria in occlusal lesions often enough to justify their use as bactericidal agents before sealants are applied.

Indiana University-Purdue University Indianapolis (IUPUI) / A method was devised to evaluate the effect of the "frozen slab" mixing technique on the physical properties of a zinc phosphate, zinc silicophosphate, hydrophosphate and polycarboxylate cement. Those properties studied were the setting time, compressive strength, tensile strength and solubility. Standardized mixing procedures were employed using predetermined powder/liquid ratios. Setting and working times were increased for all cements when mixed on glass slabs chilled to -15 c. All cements kept on the cold slab were still unset after 32 minutes. Compressive and tensile strengths were adversely affected by the "frozen slab" technique. All cements gave parallel reductions of the two strengths on the order of 20 percent except the polycarboxylate which exhibited only a 5 percent reduction in tensile strength. The polycarboxylate exhibited the highest tensile strength while its compressive strength was one half the others tested. Solubility samples were prepared and placed in 0.001M acetic acid at pH4. Solutions were changed daily and solubility was determined by the gravimetric method. The solubility of all cement was adversely affected. The zinc silicophosphate exhibited the highest and the polycarboxylate the lowest solubility of the cements tested. It was recommended that cements be mixed above the dew point and multiple mixes be used to ensure optimum physical properties.

Thesis (M.Sc.D.)--Boston University School of Graduate Dentistry, June 1967. / 168 pages plates 29 cm.

Thesis (M.S.)--University of Michigan, 2001. / Includes bibliographical references.

published_or_final_version / abstract / Dental Surgery / Master / Master of Dental Surgery

published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

published_or_final_version / Dentistry / Master / Master of Dental Surgery

published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

The demand for posterior aesthetic restorations has dramatically increased in recent years. Several new materials have been developed with improved aesthetic, adhesive and mechanical properties. However, microleakage elimination, especially if the margins are on dentine or cementum, and attainment of optimum mechanical properties for posterior use, are still questionable. The aim of this study was to investigate microleakage and surface microhardness of a nanofilled, a nanohybrid and an ormocer based nano-ceramic composite restorative material.