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At least 757 records · Page 42Linked to original sources
PubMed1991

[Bond strength of newer dentine adhesive systems].

Introduction of new dentine bonding agents in a practice of dentistry, variety of results on their crucial characteristics in foreign literature and lack of information in our literature led to a necessity to conduct own scientific research on dentine adhesives in order to facilitate the choice of available products. The purpose of this study was to estimate the adhesive strength of different dentine bonding agents to a treated human dentine immediately after light curing of a compatible composite material. Shear and tensile bond strength of Tripton, Gluma, Scotchbond-2 and Dentin Protector was measured. Control material was glass-ionomer base-cement Vitrabond. Human extracted premolars from both jaws were prepared to a flat surface from either occlusal or buccal aspect, and materials were applied, respectively. The results showed: a) values of shear bond strength ranged from 2.01-3.92 MPa with no statistical differences between tested systems; b) tensile bond strength varied from 13.7-26-84 MPa; the highest value showed Scotchbond-2, following by Gluma, but significantly lower values showed Tripton and Dentin Protector; c) the aspect of prepared tooth crown had no significant effect on bond strength with the exception of shear bond strength for Gluma-system, when applied on buccal surface showed significantly higher values than applied occlusally; d) dentine-bonding agents which dissolve smear layer with acid components and remove it from prepared dentine surface showed stronger adhesion than agents which leave this debris on a dentin surface.

Adhesiveness↗
PubMed1991

Genetic and epigenetic regulation of craniofacial development.

This paper reviews a series of odontometric, anthropometric and cephalometric investigations of genetic and epigenetic regulation of dental, occlusal and craniofacial development. The results show that genes encoded with the X and Y chromosomes regulate the development of tooth crowns and roots. The Y chromosome seems to affect general somatic growth by regulating both cell function and mitotic activity. The effects of the X chromosome seem to be more restricted and include influences on the growth of cartilaginous structures and dental enamel. The findings also indicate that high masticatory stress promotes jaw growth and decreases occlusal variation, supporting the hypothesis that masticatory activity regulates occlusal and craniofacial development. In addition, the findings suggest that nerve growth may affect bone growth in the craniofacial skeleton.

Animals↗
PubMedDate not supplied

[The treatment of periodontitis with prolonged-action propolis preparations (clinical x-ray research)].

A 4% alcohol solution of bee glue is suggested to be added to the filler for root-canal filling, besides the traditional treatment of the root canals with bee glue solution. Clinical and x-ray examinations have demonstrated a high efficacy of such technique in acute, exacerbated, and chronic forms of periodontitis. This filler is characterized by an anesthetizing effect; it resolves behind the root canal apex within 3-12 months, is preserved in the root canals, does not stain the tooth crown, promotes regeneration of the bone structures, and prolongs the effect of 0.4% water-alcohol bee glue emulsion.

Delayed-Action Preparations↗
PubMed1988

Prenatal pattern emergence in early human facial development.

This report addresses the emergence of proportional patterns in the early development of the human face. Fifty-nine human embryos and fetuses (7 through 26 weeks fertilization age) constituted a "normal" study sample. Midfacial cephalometric analyses were done on projected histologic sections cut frontally through the maxillary deciduous first molar tooth crowns. The midface was divided into three cephalometric zones. Data show that while each zone increases in absolute width, least change is seen in the central facial zone, with greatest change seen in the lateral-most facial zone. This pattern of proportional stability of the central facial zone becomes evident at 9 weeks gestation, at which time the changing embryonic optical axes have converged toward the midline to within several degrees of their position at birth. These data show that the central portion of the postnatal facial T-zone has a clearly recognizable prenatal antecedent as early as the ninth week in fetal life.

Cephalometry↗
PubMed1993

High resolution electron microscopy of the junction between enamel and dental calculus.

Newly formed dental calculus grows on the enamel surface after the tooth crown is exposed to the oral environment. In order to demonstrate the crystal coherence, the junction between enamel and dental calculus was examined in the high resolution electron microscope. Ultrathin sections were also used for selected area electron diffraction to reveal any newly formed mineral phase. High resolution electron microscopy (HREM) revealed that lattice fringes of dental calculus crystals directly coincided with those of enamel crystals. Two types of coherence were identified at the junction: in one type, a dental calculus crystal contacted the side of an enamel crystal; in the other type, the former contacted the tip of the latter. Tilt boundaries between lattice striations showed varying degrees of curvatures in contact levels. A dislocation of lattice striations was also observed at the junctional regions. Selected area electron diffraction patterns of dental calculus were almost consistent with hydroxyapatite (OH-AP). These findings indicate that the elongation and/or enlargement of lattice fringes of calculus crystals during their growth brings direct coherence with enamel crystals. This suggestion is supported by the fact that it is clinically difficult to completely remove the dental calculus without the loss of the superficial layer of enamel.

Crystallography, X-Ray↗
PubMed1993

Scanning electron microscopic observation on the dentin surface of rat enamel-free areas.

Formation of the enamel covering on the dentin of the tooth crown is thought to depend upon the dentin surface structure during the early stages of enamel development. For this reason, observations were made of the dentin surfaces of both the enamel-free area (EFA) and the region beneath the enamel area. After treatment with sodium hypochlorite and formic acid, scanning electron microscope observations were made of the EFA surface and the exposed dentin surface beneath the enamel of unerupted rat mandibular first molars. Cone-like projections consisting of matrix fibers were observed on the dentin surface covered with the enamel. These cone-like projections formed continuous ridges that connected with the network structure. At the concavities of these network structures these projections were distributed sparsely. Instead of the cone-like projections, the matrix fibers formed a coarse network structure along the surface at the EFA.

Amelogenesis↗
PubMedDate not supplied

Bond strength of glass ionomers to coronal and radicular dentin.

A study was conducted to compare the shear bond strength of a glass-ionomer cement and glass-ionomer base to coronal and radicular dentin. Two different glass ionomers were bonded to paired coronal and radicular human dentin surfaces that had received no surface treatment or had been treated passively for 20 seconds with either 40% or 25% polyacrylic acid. When only the effect of the type of dentin surface was considered, glass-ionomer bonds were greater to radicular dentin than to coronal dentin. With one exception, bond strengths to both dentin surfaces were greater with the base ionomer (Ketac-Bond) than with the luting cement (Ketac-Cem). Bond strengths of both glass ionomers were greater after dentin surface treatment with either 25% or 40% polyacrylic acid than with no treatment.

Acid Etching, Dental↗
PubMed1996

Pulpal temperature changes during low-power hard-tissue CO2 laser procedures.

Thermal insult to pulpal tissue is recognized as a major limitation to the use of lasers for dental hard-tissue procedures. This study examined thermal changes at the level of the dental pulp in human molar teeth irradiated with a CO2 dental laser using a pulsed mode of operation. Sectioned molar teeth were exposed, in vitro, to CO2 laser radiation. The laser parameters were those used clinically for laser desensitization and laser-enhanced fluoride treatment. Fissure regions and root surfaces were irradiated. For settings which might reasonably be used clinically, the temperature rise was not of a magnitude which would be expected to cause pulpal inflammation or necrosis. With regard to thermal properties of tooth structure, times taken to reach the maximum temperature reduced, and times taken to cool to baseline increased with increasing laser exposures.

Analysis of Variance↗
PubMed1993

Morphometric study of teeth in age calculation.

The diagnostic usefulness of some morphometric parameters of teeth in age determination were studied. In the first series 173 central incisors from 13-83 year-old individuals were examined and in the second series 72 teeth from 30 individuals (aged 39 to 80 years). Root transparency and dentinal tubule diameter were the most reliable parameters on the basis of image analysis (IBAS system) of scanning electron microscopic images. These variables were used in multiple linear regression analyses which led to the exclusion of secondary dentine as it did not improve the fit and therefore did not help to explain the dependent variable. The precise measurement of the morphometric variables we used facilitates age determination, reducing the mean error reported by other authors who used subjective estimates. Our results document the limited effectiveness of these parameters in age estimation due to individual variations caused by genetic factors and chewing habits.

Adult↗
PubMed1997

Pre-eruptive coronal radiolucency in a mandibular premolar: a case report and literature review.

This report describes a coronal radiolucency in an unerupted mandibular premolar. This anomaly, which most frequently involves the mandibular second molars, has been variously attributed to dental caries, dentine hypoplasia, inclusions of uncalcified enamel matrix, and resorption. The present instance was considered to be due to external resorption. Because these lesions may enlarge rapidly, frequent radiographic monitoring of an affected tooth is recommended. Early restorative treatment has been shown to be successful even in affected teeth with small pulp exposures.

Adolescent↗
PubMed1997

Clinical morphology of the mesial fossa of the maxillary first permanent molar in relation to operative dentistry.

The purpose of this in vivo study was to identify a previously unreported occlusal enamel ridges in the mesial fossa of the maxillary first permanent molars by using caries detector dye. Seventy two maxillary right and left first permanent molars of thirty-six patients were examined in this study. Horizontal linear measurements in millimeters, location, and shape of the occlusal ridge in the mesial fossa were examined clinically and were compared to the transverse ridge in a percentage form. Five occlusal enamel ridges with different locations, and pathways were detected in addition to the transverse ridge, two major ridges (> 33.33% of the transverse ridge) and three minor ridges (< 33.33%) of the transverse ridge). There were symmetrical patterns of the ridges between right and left maxillary first permanent molars (80.5%).

Contraindications↗