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Biomedical subjects

C H Pameijer

Publications and source records attributed to C H Pameijer.

At least 19 recordsLinked to original sources
PubMed1995

Microleakage of "surface-sealing" materials.

PURPOSE: To test several dental materials for their sealing properties by subjecting restored teeth to thermal cycling. MATERIALS AND METHODS: Ten teeth per group were assigned at random to six experimental and six control groups. In the experimental groups a resin composite was surface-sealed with IRM, glass ionomer, amalgam, dentin bonding agent and resin composite, experimental hybrid cement, or zinc oxide and eugenol. These six surface-seal materials were placed in bulk in the control group. After cavity preparation, restoration, cut back and application of the surface-seal material, the teeth were subjected to thermal cycling, imbedded and sectioned. A score of 0-3 was given to the amount of dye leakage observed. RESULTS: Zinc oxide and eugenol demonstrated the most leakage, whereas the resin composite system TPH had the least. The results of this in vitro study render the recommendation of zinc oxide and eugenol as a surface-seal material questionable.

Analysis of Variance↗
PubMed1994

Long term clinical evaluation of three luting materials.

A last critical step in the completion of a cast restoration is permanent cementation. With the development of new luting agents the practitioner has to be aware of the physical and biological properties as well as the long term clinical performance of these materials. In this study three commonly used luting agents were evaluated over a four year period. The three cements, a zinc phosphate, a glass ionomer and a resin cement were tested for their reaction to periodontal tissues, pulpal response and other clinical parameters. In twenty six patients, 61 crowns, onlays or bridge abutments were cemented. Evaluations were made at 0 hour, after 7 days, 6 and 12 months and 4 years. In general the cements performed satisfactorily. Health of periodontal tissues adjacent to the crowns improved considerably after 7 days. Postcementation hypersensitivity appeared to be a negligible problem, which was attributed to the time span between preparation and cementation, which exceeded in most instances four weeks. The choice of a final luting agent should be based on anticipated postoperative pulpal reactions, rather than exclusive reliance on physical properties.

Analysis of Variance↗
PubMed1992

Influence of low-viscosity liners on the retention of three luting materials.

A number of materials are available to protect the pulp from postoperative sensitivity. The effect of a calcium hydroxide liner and a dentinal desensitizing agent (potassium oxalate) on crown retention was investigated. Gold crowns were cemented on standardized crown preparations with zinc phosphate cement, glass-ionomer cement, or one of two resin cements. A tensile force was applied until separation occurred. The mean applied force at rupture varied greatly among the groups, indicating that the pulpal protection agent may have a distinct effect on the retention of cast restorations. In addition, other clinical factors, such as angle of convergence, crown height, and total surface area of the tooth should be considered.

Analysis of Variance↗
PubMed1992

Pulp reactions to resin cements.

Several formulas of a resin-filled cement that successfully passed a series of laboratory tests were evaluated for their pulp reactions in primates. Their performance was compared to three controls: a positive control (silicate cement), a negative control (zinc oxide-eugenol) and a control group with the protection of calcium hydroxide. The chemical cure resin cement scored the lowest reactions for the 5-day evaluation. The intermediate and prolonged periods demonstrated no significant differences while average, acceptable responses were recorded. No resin cement formula scored as low as the negative control for the three time periods. Silicate cement, the positive control, scored the greatest inflammatory reaction of any material in the intermediate period, but this response was resolved after 60 days. When the resin cements were used with calcium hydroxide, the traditional reactions to calcium hydroxide were observed; an initial mild irritation that diminished with time and was completely resolved after 60 days. The resin cements, with or without the calcium hydroxide, compared favorably to the negative control IRM after 60 days. If the resin cements are appropriately applied, they are expected to be well tolerated by the human pulp. The microorganisms associated with microleakage (MLM) were minimal and there appeared to be no correlation between the MLM and pulp inflammation.

Analysis of Variance↗
PubMed1991

Periodontium response to a root canal condensing device (Endotec).

Two Macaca (fascicularis) monkeys were used to study the effect of two warm endodontic condensation techniques (Endotec and vertical condensation method) on periodontal tissues. The specimens were histologically evaluated at 3 and 32 days after the endodontic treatments were completed. In this study the periodontium was divided into coronal, middle, and apical thirds. Results indicated that there was no heat-related damage to periodontal tissues from either of the two methods employed. However, some Endotec specimens generated small, reactive inflammatory infiltrates that were restricted to the root canal opening or adjacent periodontal membrane. Similarly, some vertical condensation specimens developed periapical inflammatory processes as well, but they were more extensive and comprised the alveolar bone and marrow spaces.

Animals↗
PubMed1991

Biocompatibility of a glass ionomer luting agent. 2. Crown cementation.

In this experiment, 64 crown preparations were made in four primates. Final impressions, die fabrication, wax patterns and castings were achieved using conventional established clinical and laboratory techniques. Vented and unvented crowns were cemented with a glass ionomer cement (GI) and a zinc phosphate cement (ZOP). Some preparations were protected with calcium hydroxide liquid. On the same animals, in teeth not used for crowns, Class V cavities were prepared and GI and ZOP inserted by means of a pressure technique imitating hydraulic pressure generated during crown cementation. After periods of 5 and 60 days, the animals were sacrificed, the jaws dissected, fixed in formalin and prepared for histological evaluation. Of the 64 cemented crowns, one was unaccounted for. Of the unvented crowns with GI (5 days), vented crowns with GI (60 days), unvented crowns with ZOP (60 days), Class V with ZOP (5 days) and GI (60 days) with a remaining dentin thickness (RDT) of less than 1 mm, inflammatory responses of greater than or equal to 1 degree (on a scale 1-4 degrees) were observed. The use of liquid calcium hydroxide reduced the intensity of the reactions, in particular when small RDTs were present. It can be concluded that when RDTs of 1 mm or more were present, the cements in all groups were non-toxic. When it is estimated that the RDT is less than or equal to 1 mm, the use of a calcium hydroxide liner is recommended. Placement of luting agents in Class V preparations with pressure resulted in reactions resembling crown cementation.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1987

Simple defluoridation procedures for Kenyan borehole water.

Magnesium oxide and bone meal were used as chemical defluoridating agents to reduce excessive amounts of fluoride from artificial water samples which had been prepared to simulate Kenyan water samples with a fluoride concentration ranging from 1 to 9.3 ppm. The water filtrate from bone meal was clear and palatable. The filtrate from magnesium oxide was slightly slimy and cloudy, but palatable. Either of these chemical agents may be used in simple defluoridation procedures in rural and suburban areas using borehole water to reduce the excess fluoride in the water to beneficial non-toxic levels. Both magnesium oxide and bone meal are inexpensive chemicals and readily available in Kenya.

Biological Products↗
PubMed1986

Tensile bond strength of fluorosed Kenyan teeth using the acid etch technique.

Tensile bond strength tests were performed on 120 enamel specimens equally distributed over 'normal' American, 'normal' Kenyan and fluorosed Kenyan teeth. The mean tensile bond strength for American teeth was 59.08 +/- 15.81 kg/cm2, for normal Kenyan teeth 41.52 +/- 14.64 kg/cm2 and for fluorosed Kenyan teeth prior to removing the surface layer 49.20 +/- 17.67 kg/cm2. There was an increase in the adhesive bond strength for fluorosed teeth after first grinding and polishing with a green stone followed by pumice (58.84 +/- 20.65 kg/cm2). The coefficients of variation were 27% for fluorosed Kenyan teeth prior to grinding and 35% after grinding. The tested etching times varied from 60 to 150 s. The normal Kenyan teeth had the lowest tensile bond strength. This may have been due to the inability to etch adequately these teeth in 60 s. The increase in tensile bond strength indicates removal of the surface layer of fluorosed enamel by grinding then acid etching may improve the bond strength.

Acid Etching, Dental↗
PubMed1985

Enhancing esthetics in porcelain fused to metal through technique modifications.

Three techniques have been discussed and illustrated, with diagrams and examples of clinical cases, that will aid the practitioner to achieve better esthetics when using porcelain fused to metal restorations. The labial butt joint preparation is particularly suitable for upper anterior teeth when the smile line exposes the gingival margin of the restoration and maximal esthetics are demanded. Clinically, the preparation has to be executed in such a way that technically the ceramist does not have to compromise the restoration. Wrong buccal shoulder preparations and too large a space between porcelain and shoulder are the most frequently observed errors. A porcelain sandwich technique in which a thin incisal porcelain layer is condensed between body and translucent porcelain enhances the translucency of the restoration and improves the natural appearance. This technique is particularly suitable for anterior teeth, yet posterior teeth benefit from this method as well, and particularly upper bicuspids are excellent candidates. The third technique uses a blend gold that is applied to the opaque and covered again with another layer of opaque. This method effectively blocks the graying effect often experienced at the gingival margin caused by the underlying metal. A deep chamfer offers the ideal preparation and accommodates the technical requirements best. In conclusion, it can be stated that dentists and dental technicians have available various techniques that make it easier to meet the theoretical and practical requirements of esthetics in dentistry.

Crowns↗