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At least 739 records · Page 41Linked to original sources
PubMed1993

Effect of single and repeated application of chlorhexidine varnish on mutans streptococci in plaque from fissures of premolar and molar teeth.

The aim of this study was to determine the effects of one and two applications of 40% chlorhexidine varnish on the numbers of mutants streptococci in human dental fissure plaques from molar and premolar teeth. Twenty-nine subjects (aged 20-30 years) participated in the study and were randomly assigned to one of three groups. In each subject two fissures with high levels of mutants streptococci were selected. The fissures in group 1 (control group) were treated with placebo varnish containing no chlorhexidine. Fissures in group 2 received a single application of 40% chlorhexidine varnish, whereas fissures in group 3 received an additional chlorhexidine varnish application 1 week after the first application. Fissure plaque samples were taken prior to the first application of chlorhexidine varnish and subsequently 1, 2, and 4 months thereafter. Compared with the fissures in the control group, the suppression of mutans streptococci was significant in plaques from group 2 for up to 2 months and in plaques from group 3 for up to 4 months after application. Mutans streptococci were suppressed more strongly in premolar than in molar teeth and more strongly and for a longer period of time in fissures of premolar teeth treated twice than in fissures of premolars treated once.

Adolescent↗
PubMed1997

A clinical and microbiological study of deep carious lesions during stepwise excavation using long treatment intervals.

Concern about the survival of microorganisms in deep carious lesions may often lead to unnecessary exposure of the pulp during final excavation. There are reasons, therefore, to initiate systematic studies on the alternative procedure known as stepwise excavation. Clinical evaluation of stepwise excavation was performed on 31 deep carious lesions considered to result in pulp perforation by traditional excavation. This study examines the clinical and microbiological alterations during the final excavation performed during long intervals (6-12 months) after the initial treatment that included peripheral dentine excavation and removal of the central cariogenic biomass and the superficial necrotic dentine. The dentine colour and consistency were assessed by means of standardized scales before application of a Ca(OH)2 compound and a temporary sealing for 6-12 months. Reassessments were performed before the after final excavation. Microbiological dentine samples were obtained in 19 randomly selected lesions by a sterile bur, transferred to and diluted in reduced transport fluid, and plated on tryptic soy agar. After anaerobic incubation at 37 degrees C for 7 days, total colony-forming units per millilitre were counted from (1) peripheral excavated and hard dentine (control), (2) central demineralized dentine before and final excavation, and (3) central dentine after the final excavation. Six samples of central demineralized dentine were without any cultivable flora increasing to 9 samples after the final excavation. The clinical dentine changes occurring during stepwise excavation were characterized by enhanced hardness of the dentine which was associated with a marked reduction in bacterial growth after the final excavation. Despite the presence of bacteria in the excavated dentine none of the carious lesions resulted in pulp perforation, suggesting that the initial removal of the cariogenic biomass appears to be essential for control of caries progression. Stepwise excavation is not only an appropriate treatment of deep carious lesions but is also considered a suitable model for microbiological studies to determine the bacteria persisting in clinically excavated lesions.

Anaerobiosis↗
PubMed1983

A simulation model for transient thermal analysis of restored teeth.

A theoretical model was developed to analyze the influence of various cement bases on temperature distribution and heat flow in restored teeth. A physical model of a molar was developed to simulate different thermal processes by simple parameter variation. The time-dependent temperature field was calculated using the finite element method (FEM). The values for material properties and thermal load were chosen from the dental literature. The results are in good agreement with clinical experimental research as published by Trowbridge et al. It is concluded that the model is a valid tool for further research with regard to the influence of restorative materials and cavity design on the thermal behavior of restored teeth.

Dental Cavity Lining↗
PubMed1984

The influence of restorative dental materials on heat transmission in human teeth.

Using the finite element method, we analyzed the temperature distribution and heat flow patterns in an axisymmetric tooth model. The models of an unrestored tooth and three teeth restored with different restorative materials were evaluated comparatively. The insulating ability of a calcium hydroxide cement base (Ca(OH)2) is low, which is inherent in its insufficient thermal and poor mechanical properties. In the given conditions, the Ca(OH)2 base reduces the temperature increase at the cement-dentin interface by 12.5% with respect to a restoration of amalgam only. By using a double base (Ca(OH)2 + polymer-modified zinc oxide-eugenol), the reduction is 21.9%. With respect to a sound tooth model, the presence of a double base in the restored tooth caused a temperature increase of only 0.1 degree C at the pulpo-dentinal junction. The thermal conductivity coefficient (lambda) of amalgam does not have any influence on the results of the calculations. The heat transfer coefficient (alpha) turned out to be an essential parameter in this mathematical model.

Calcium Hydroxide↗
PubMed1987

Testing sealing properties of restorative materials against moist dentin.

The objectives of this investigation were (1) to develop a sensitive laboratory system that simulates the physiological and clinical conditions of a prepared human tooth in order to facilitate the determination of the bonding and sealing efficacies of restorative dental materials and (2) to conduct experiments with two dentin bonding agents, two posterior composite resin restorative materials (hybrid and microfilled), and a glass-ionomer type II filling material. The system functioned well and provided data to indicate that, after margination, the two posterior composite resin restorative materials performed equally and both performed better than the glass-ionomer filling material; none of the materials provided a perfect seal immediately after insertion, although some restorations demonstrated perfect seals from 16 hours to 28 days after placement; the seal of the glass-ionomer material improved after 28 days of storage in buffer solution; each successive step in the respective composite resin procedures improved the seal except in one case for the microfilled resin.

Composite Resins↗