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At least 253 records · Page 14Linked to original sources
PubMed2001

Global hydration kinetics of tricalcium silicate cement.

We reconsider a number of measurements for the overall hydration kinetics of tricalcium silicate pastes having an initial water to cement weight ratio close to 0.5. We find that the time dependent ratio of hydrated and unhydrated silica mole numbers can be well characterized by two power laws in time, x/(1-x) approximately (t/t(x))(psi). For early times t t(x) a parabolic behavior (psi=1/2). The crossover time is estimated as t(x) approximately 16 h. We interpret these results in terms of a global second-order rate equation indicating that (a) hydrates catalyze the hydration process for t t(x), and (c) the value of the associated rate constant is of magnitude 6 x 10(-7) - 7 x 10(-6) l mol(-1) s(-1). We argue, by considering that the hydration process actually occurs via diffusion limited precipitation, that the exponents psi=5/2 and psi=1/2 directly indicate a preferentially plate-like hydrate microstructure. This is essentially in agreement with experimental observations of cellular hydrate microstructures for this class of materials.

Journal Article↗
PubMed1990

[Comparative biological testing of Ketac-Bond glass ionomer cement].

The biocompatibility of a fast setting glass-ionomer cement and of reference materials (zink-phosphate cement, silicate cement, ZOE, composite) was assessed in a comparative biological study. Cytotoxicity testing revealed 90% counted cell numbers after incubation for 96 hours. Subcutaneous implantation tests resulted in slight, moderate and severe connective tissue reactions. In contrast to these results the three different usage tests revealed slight, reversible pulp reactions in rat incisors, pig and human teeth. After 90 days of testing there was no chronic persistent pulp irritation. It may be concluded that Ketac-Bond, is an acceptable restorative material.

Animals↗
PubMed1998

Evaluation of cytotoxicity of calcium phosphate cement consisting of alpha-tricalcium phosphate and dicalcium phosphate dihydrate.

A newly developed calcium phosphate cement, MM, was evaluated for tissue irritability by means of cell cultures. In this study, MM showed extensive mild cytotoxicity compared with other cements before setting. Inhibition of adhesion of L-929 cells was not observed after contact with MM for 24 hours. The influence of MM on colony formation was approximately the same as that of another calcium phosphate cement and less than that of a glass ionomer cement. Toxicity of MM after setting was compared with four cements; another calcium phosphate cement, glass ionomer cement, silicate cement and zinc oxide eugenol cement, but MM showed the least influence on cell morphology. Judging from these results, MM appears to be less cytotoxic than the cements in current use.

Animals↗
PubMed1990

Placement and longevity of tooth-colored restorations in Denmark.

A survey has been made of the use of materials and the reasons for placement of 2542 tooth-colored restorations in Denmark. In adults 38% of all the restorations were inserted because of primary caries, and 62% were replacements of failed restorations. In children primary caries was the reason for placing 68% of the restorations in deciduous teeth and 77% of those in permanent teeth. Resin-based materials were the most frequently used tooth-colored restorative, except in the treatment of deciduous teeth, for which glass ionomer cement was used preferentially. Silicate cement was used for less than 2% of the tooth-colored restorations, and the few old silicate cement restorations were most often replaced with resin materials. The reasons for replacement of resin restorations were dependent on dentition, age of the patient, and type of restoration. Secondary caries, fracture of restoration, and loss of fillings were the most frequently recorded failures. The age of the resin restorations replaced ranged from 0 to 19 years, and half of the failed restorations in adults were more than 6 years old. In permanent teeth in children half of the failed resin restorations were replaced within 2 years, whereas half of those in primary teeth were replaced within 1 year.

Adolescent↗
PubMed1998

Decay-inhibiting restorative materials: past and present.

Clear differences exist in the fluoride release characteristics and setting reactions of glass-ionomer cements and compomers. Differences in decay inhibition associated with specific materials are less clear. Furthermore, resin added to glass ionomer cement formulations and acids added to composite resins make it difficult to distinguish composite resins from compomers and glass ionomer cements, all of which have reported fluoride release. Optimal fluoride release from a dental restorative depends on several conditions, including oral flora, saliva, diet, mineral content of the dental tissues, and marginal seal of the restoration. Presently, in vitro and in vivo studies suggest that materials which behave similarly to silicate cements in their setting reactions and hydration characteristics will behave as decay-inhibiting restoratives. Until optimal fluoride release from dental restoratives can be quantified, dental clinicians are encouraged to consider clinical outcomes as the best test for decay inhibition. Nearly a century of clinical findings support the anticariogenicity of silicate cements. This article reviews fluoride release and anticariogenicity of restorative materials using silicate cement as a model with a well-defined mechanism for preventing secondary caries. The behavior of newer materials is compared to silicate cement for predicting decay inhibition.

Cariostatic Agents↗
PubMed1976

[Bacterial accumulation on silicate and composite materials].

It was shown in a previous study that more plaque accumulates on composite filling materials than on silicate cement and amalgam. The purpose of the present investigation was to compare the accumulation of Streptococcus mutans on silicate cement and on composite material by scanning electron microscopy. Whether the adhesion was dependent on the presence of sucrose was also tested. Round disks, 6 mm in diameter, were made from the two materials. The disks were submerged in media with and without sucrose and inoculated with S. mutans OMZ 176. The disks were removed after 1 or 30 minutes, rinsed in saline and prepared for SEM. Along the diameter of each disk pictures were taken at similar intervals. From a total of 48 pictures from each material 18 pictures were selected at random and the number of microorganisms counted. The results indicated that bacteria initially adhered to both silicate and composite in about the same number. The presence of sucrose did not influence the initial adsorption. After 30 minutes bacteria were scarcely found on silicate, whereas large clumps of bacteria were attached to the composite. Sucrose increased bacterial accumulation on composites but did not affect the adherence to silicate cement.

Adhesiveness↗
PubMed1998

Pulp reaction to a tri-cure resin-modified glass ionomer.

OBJECTIVE: This study evaluated the pulp response to a tri-cure resin-modified glass ionomer cement and compared this response to those elicited by a zinc oxide-eugenol cement and a silicate cement. Materials were placed in nonexposed class V cavity preparations on human teeth. STUDY DESIGN: Sixty premolars were selected in orthodontic patients in a voluntary group of teenagers. All cavities were prepared according to International Dental Federation specifications. Resin-modified glass ionomer and silicate applications were carried out according to the manufacturers' instructions. RESULT: All teeth were asymptomatic. Pulp responses to the resin-modified glass ionomer cement were slightly greater than to the zinc-oxide-eugenol cement. Bacterial staining attempts were inconclusive with regard to time intervals and pulp responses. No necrotic pulps were seen in any teeth. CONCLUSION: The tri-cure resin-modified glass ionomer cement elicited a slightly greater adverse pulp response than did the zinc-oxide-eugenol cement with respect to the healing process of the pulp.

Composite Resins↗
PubMed1977

Evaluation of biologic effects of dental materials using four different cell culture techniques.

The cytotoxicity of fresh and 1-day-old silicate cement, composite restorative material and zinc oxide-eugenol cement (ZOE) was tested using human epithelial cells (NCTC 2544) in four different cell culture systems: (1) 51Cr-release from prelabeled cells after incubation for 4 and 24 h in the presence of the materials. (2) Implanting the materials on an agar everlay and visualizing any cytotoxic effects after 24 h by neutral red vital stain. (3) Cell growth during 5 d in the presence of the materials. (4) Colony-forming ability after exposure of the cells for 30 min to medium previously incubated with the materials for 24 h. Freshly prepared and 1-day-old ZOE exhibited a prominent cytotoxic effect in all four systems. A less marked effect was found for the composite material in systems 2, 3, and 4, while silicate cement appeared to be the least toxic material in these three systems. Neither silicate cement nor composite showed any cytotoxic effect in system 1 based on 51Cr-release. It is concluded that the effects obtained by the cell culture techniques did not mimic the reactions obtained when the materials are tested under conditions which reflect their clinical use.

Cell Division↗
PubMed1993

Pulpal response to a new light-activated fluoride releasing liner.

The purpose of this study was to investigate the degree of pulp irritation of a newly developed light-activated fluoride-releasing adhesive resin liner using canine teeth compared to the amount caused by a negative control, zinc oxide eugenol cement (ZOE), and a positive control, silicate cement (silicate). In the cases of unexposed pulp, this experimental liner showed none, slight or moderate pulpal changes at 3 d postoperatively. At 30 and 90 d, no pulpal response to the experimental liner was detected in almost all cases. These findings were similar to the ZOE and better than the silicate. There was less evidence of pulpal irritation produced by the experimental liner. This material seems to be safe to the pulp under the conditions of this study.

Analysis of Variance↗
PubMed1986

Dental pulp inflammation; experimental studies in human and monkey teeth.

Data from several studies performed during the last 15 years indicate that bacteria and their products are the main etiological factor for dental pulp inflammation. The present series of investigations was conducted in order to determine the irritating effect from various oral bacterial components and restorative measures on dental pulpal tissue and to ascertain reaction patterns of inflamed pulp tissue. The different bacterial materials were tested in an experimental model where the test substance was applied and enclosed in buccal class V cavities prepared in human or monkey teeth. The pulp tissue response was evaluated from tooth specimens after both short (8 hours) and long time (150 days) challenge with the test substance. Intra and extra cellular components from pure bacterial species, cell wall material and a crude mixture of 8 bacterial species were used as representative test materials for oral bacteria associated with growth on or in dentin. Silicate cement restorations were also used as a pulp irritating restorative procedure. The degree of pulpal inflammation was classified according to a descriptive method. In order to obtain a better evaluation method for pulp tissue reactions, a stereo morphometric technique was developed. This method was used in the last study to evaluate the pulp tissue reactions to silicate cement restorations after dentin treatment with calcium hydroxide. The chemotactic effect of the different bacterial materials were also tested in wound chambers implanted in the back of rats. Results from these studies showed that components from different bacterial species had varying capacity to induce pulpal inflammation over cut dentin. The severity of the early inflammatory response was not altered after decomplementation. The tested bacterial products had a similar chemotactic effect on the pulp tissue as on ordinary connective tissue. If the pulp was challenged with bacterial products for a long time period, healing and repair were frequently found, although if the pulp tissue was primary severely inflamed. The inflammatory reactions and repair patterns in human teeth were similar to those of monkey teeth. Treatment of exposed dentin with calcium hydroxide reduced the pulp irritating effect of silicate cement restorations, but induced only limited volumes of irregular secondary dentin formation.

Animals↗
PubMed1977

[Animal experimental studies on a new dentin and pulp-protective lacquer (Bayer D-520)].

In an ADA experiment on the protective qualities of a new polyurethane varnish (D-520 Bayer) 72 class 5 cavities were prepared on 3 monkeys and treated by the following 4 methods: -- 18 silicate cement (Bio-Trey) with varnish -- 18 silicate cement (Bio-Trey) without varnish -- 18 composite (Adaptic) fillings with varnish -- 18 composite (Adaptic) fillings without varnish. After an observation time of 14 days, a significant positive result for the 520 varnish could be obtained. An experiment lasting 12 weeks was subsequently undertaken.

Animals↗