Tissue reactions to a new restorative material

Improving bond strength through acid etching of dentin and bonding to wet dentin surfaces

A bonding system using moisture on the tooth surface can be an enormous benefit as obtaining dentin dryness in the mouth is nearly impossible. The author describes a system that bonds to both wet and dry surfaces.

Pulp response to a composite resin inserted in deep cavities with and without a surface seal

The objective of the present investigation was to observe pulp response to a composite material (Occlusin) placed in deep cavities with and without a zinc oxide-eugenol covering. Deep cavities were prepared in 116 teeth of four young baboons and divided into four groups. In group 1, Occlusin material was placed directly into the cavity, without etching, to approximately half the depth, cured, and covered to the surface with zinc oxide-eugenol. In group 2, the cavities were etched, a bonding agent was applied, and Occlusin material was used and cured in two increments to fill the cavities up to the surface. In group 3, the composite resin was placed in two increments as in group 2, but without etching and bonding; and in group 4 (control), the cavities were filled up to the surface with zinc oxide-eugenol. Follow-up times were 5, 30, and 90 days. Light microscopy revealed that, although some differences were observed, a good pulp response was evident in all groups.

Lipid peroxidation as a possible cause of benzoyl peroxide toxicity in rabbit dental pulp--a microsomal lipid peroxidation in vitro

The toxicity of composite resin on rabbit dental pulp was investigated biochemically. A microsomal fraction of rabbit dental pulp was incubated with each of the components of composite resins, and the formation of peroxide was determined by the thiobarbituric acid reaction. Benzoyl peroxide (BPO), the most widely used catalyst, was the most effective on peroxidation, but monomers were not. Cations such as Cu2+ or Fe2+ were required for acceleration of this reaction. Authentic polyunsaturated fatty acids and phospholipids were extensively converted into their peroxides by BPO, but amino acids and carbohydrates were not. Among the active oxygens, hydroxyl radicals were thought to be responsible for BPO-dependent peroxidation. The results presented in this paper indicate that the lipid portion of the cells may be attacked by hydroxyl radicals produced by BPO and copper or iron. Therefore, BPO is considered to be the major factor responsible for the toxicity of composite resins.

The gingival response to well-finished composite resin restorations

Within the limits of this study, the following conclusions are made: 1. Well-finished and contoured composite resin restorations do not adversely affect the health of the gingiva. 2. The gingiva exhibits less inflammatory response to a well-finished and contoured composite resin restoration than to an open carious lesion. 3. The gingival inflammatory changes which do occur are independent of the presence of well-finished and contoured composite resin restorations. 4. Observation over an extended period of time is necessary to determine if composite resin restorations ultimately become gingival irritants.

The histological effects of composite resin materials on the pulps of monkey teeth

Pulpal response of three bis glycol methacrylate composite resins, Smile, Simulate and Experimental Composite no. 2 were tested on primary and permanent monkey teeth using zinc oxide eugenol (ZOE) and silicate as controls. All materials were placed in Class V cavity preparations in Rhesus monkey teeth and evaluated at 3 days and 5 and 8 weeks. The materials were randomly placed in anterior and posterior teeth utilizing 75 primary and 75 permanent teeth. Following perfusion the teeth were prepared by routine histological procedures. The 3 day response of the composite resins was moderate, characterized by disruption of the odontoblasts, vacuolization and mild inflammatory response underlying the cavity. At 5 weeks the formation of reparative dentin and a decrease in the inflammatory response was similar for all resins observed. At 8 weeks a slight increase in reparative dentin and continued decrease in inflammation was noted when compared to the 5 weeks responses. At all time intervals ZOE produced the least pulpal response while silicate produced the most severe response.

Observations on cavity liners for composite resin restorations

Adhesion or surface roughness and discoloration at the interface between pulpinsulating materials and composite resins were taken as indications for interaction between the resins and the insulating materials. Some interaction occurred between all insulating materials and resins investigated. After separation of the restorative resins, the interaction of Dycal with the different composite resins varied considerably and decreased in the following sequence: Opotow, Natural, and Adaptic. The interactions of ZOE with Natural and with Adaptic were similar and more pronounced than the interaction at the Adaptic-Dycal interface but less pronounced than at the Dycal-Natural interface. A very thin film of Tubulitec was found to adhere to the composite resins in some areas. The adherence of liners containing calcium hydroxide to dentin was found to be generally stronger than the bond between these liners and composite resins. Separation of the composite resins caused tears in the varnishes and frequently in Hydroxyline. Almost completely intact layers of the varnish Copalite were observed on dentin, but Zahnlack apparently dissolved to a great extent in the resins. Among the liners containing calcium hydroxide, Dycal and Tubulitec were found to give rise to a high pH in samples of saliva, but Hydroxyline did not. Porosity and a folded surface were observed for Hydroxyline, indicating the entrapment of the solvent beneath a dry superficial layer.

Pulpal response of monkeys to modifications of a bisphenol A composite resin and cement

This investigation demonstrated the minimal pulpal response of the teeth of monkeys to bisphenol A restorative materials in the form of a cement and as a composite resin. Each material was thinned with a monomer of methyl methacrylate or of dimethacrylate.