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Apical Direction (apical + direction)
Selected AbstractsSealing evaluation of the cervical base in intracoronal bleachingDENTAL TRAUMATOLOGY, Issue 6 2003Luciane Dias De Oliveira Abstract,,, Discoloration of non-vital teeth is an esthetic deficiency frequently requiring bleaching treatment. The purpose of this study was to evaluate in vitro the cervical base efficacy in order to prevent or to minimize the leakage along the root canal filling and into the dentinal tubules. Thirty-eight extracted single-root human teeth were used, which were biomechanically prepared, filled, and divided into three experimental groups: G1, a cervical base was applied (3 mm of thickness) below the cemento-enamel junction, with resin-modified glass-ionomer cement (Vitremer); G2, the base was done with glass-ionomer cement (Vidrion R); and G3 (Control), did not receive any material as base. A mixture of sodium perborate and hydrogen peroxide 30% was placed inside the pulp chamber for 3 days, and the access opening was sealed with Cimpat. This procedure was repeated thrice. Soon after this, a paste of calcium hydroxide was inserted into the pulp chamber for 14 days. All teeth were covered with two layers of sticky wax, except the access opening, and immersed in blue India Ink for 5 days. The results did not show statistically significant differences between the three groups concerning the leakage inside the dentinal tubules. Regarding the apical direction, a statistical difference (anovaP < 0.05) was observed among the experimental group G1 and control group G3. No statistically significant difference was observed between G2 and G3 groups. Therefore, the placement of a cervical base before internal bleaching procedures is still recommended. [source] Distribution and structure of the initial dental enamel formed in incisors of young wild-type and Tabby miceEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2009Amer Sehic Mouse incisor enamel can be divided into four layers: an inner prism-free layer; an inner enamel with prism decussation; outer enamel with parallel prisms; and a superficial prism-free layer. We wanted to study how this complex structural organization is established in the very first enamel formed in wild-type mice and also in Tabby mice where enamel coverage varies considerably. Unworn incisors from young female wild-type and Tabby mice were ground, etched, and analyzed using scanning electron microscopy. In both wild-type and Tabby mice, establishment of the enamel structural characteristics in the initially formed enamel proceeded as follows, going from the incisal tip in an apical direction: (i) a zone with prism-free enamel, (ii) a zone with occasional prisms most often inclined incisally, and (iii) a zone where prism decussation was gradually established in the inner enamel. The distribution of enamel in Tabby mice exhibited considerable variability. The sequence of initial enamel formation in mouse incisors mimics development from a primitive (prism-free) structure to an evolved structure. It is suggested that genes controlling enamel distribution are not associated with genes controlling enamel structure. The control of ameloblast configuration, life span, organization in transverse rows, and movement is important for establishing the characteristic mature pattern of mouse incisor enamel. [source] Coronal sealing ability of three sectional obturation techniques , SimpliFill, Thermafil and warm vertical compaction , compared with cold lateral condensation and post space preparationAUSTRALIAN ENDODONTIC JOURNAL, Issue 3 2006Velayutham Gopikrishna mds Abstract The purpose of this study was to evaluate the effect post space preparation has on the coronal seal of root canals obturated with cold lateral condensation of gutta-percha compared with the corsonal sealing ability of three sectional obturation techniques not requiring post space preparation. Sixty-eight human maxillary central incisors were divided equally into four groups: cold lateral condensation (Group I), SimpliFill (Group II), Thermafil (Group III) and warm vertical compaction (Group IV). After coronal flaring, all four groups were cleaned and shaped with Lightspeed rotary instruments to a size 60 master apical rotary. After obturation Peeso Reamers were used to create a post space for Group I, while Groups 2, 3 and 4 incorporated the post space in the obturation (sectional technique) and did not require making a post space after obturation. The teeth were then stored in 100% humidity for 1 week and then kept in rhodamine B fluorescent dye for 3 weeks. The teeth were then split open, and the linear dye penetration from a coronal to apical direction (coronal seal) was evaluated with a fluorescent light microscope. Statistical analysis showed that Group I (cold lateral condensation followed by post space made with Peeso Reamers) leaked significantly more (P < 0.05) than the remaining three sectional obturation groups. It was concluded that stresses generated during post space preparation might be detrimental to the seal obtained by the obturation. Sectional obturations with their superior sealing ability offer a viable alternative. [source] Discuss That The Coronal Seal Is More Important Than The Apical Seal For Endodontic SuccessAUSTRALIAN ENDODONTIC JOURNAL, Issue 3 2002Anjella Sritharan One of the main principles for successful root canal treatment is the prevention of microorganisms and toxins from the oral flora penetrating through the root canal system into the periapical tissues (1). This is achieved by obturating the root canal system completely, including the coronal and apical ends. Inadequate obturation of the root canal system has been found to be the most frequent cause of failure after endodontic treatment (2). A number of studies have indicated that leakage, whether from a coronal or apical direction, adversely affects the success of root canal treatment (3,7). The significance of the coronal seal has been increasingly recognized in the dental literature (4, 5, 8, 9) and in more recent times, it has been suggested that apical leakage may not be the most important factor leading to the failure of endodontic treatment , but that coronal leakage is far more likely to be the major determinant of clinical success or failure (10). This paper will discuss aspects of: endodontic success and failure; the use of leakage studies to assess the quality of the seal; the significance of both apical and coronal leakage; followed by a review of the literature. [source] Characterization and astrocytic modulation of system L transporters in brain microvasculature endothelial cellsCELL BIOCHEMISTRY AND FUNCTION, Issue 3 2008Yadollah Omidi Abstract Brain trafficking of amino acids is mainly mediated by amino acids transport machineries of the blood,brain barrier (BBB), where astrocytes play a key maintenance role. However, little is known about astrocytes impacts on such transport systems, in particular system L that consists of large and small neutral amino acids (NAAs) transporters, that is, LAT1/4F2hc and LAT2/4F2hc, respectively. In the current investigation, functionality and expression of system L were studied in the immortalized mouse brain microvascular endothelial b.End3 cells cocultured with astrocytes or treated with astrocyte-conditioned media (ACM). LAT2/4F2hc mediated luminal uptake of L -phenylalanine and L -leucine resulted in significantly decreased affinity of system L in b.End3 cells treated with ACM, while LAT2/4F2hc mediated luminal uptake of L -alanine remained unchanged. Gene expression analysis revealed marked upregulation of LAT1 and 4F2hc, but downregulation of LAT2 in b.End3 cells cultured with ACM. The basal to apical transport of L -phenylalanine and L -alanine appeared to be significantly greater than that of the apical to basal direction in b.End3 cells indicating an efflux functionality of system L. No marked influence was observed for transport of L -phenylalanine in b.End3 cells cocultured with astrocytes, while a slight decrease was seen for L -alanine in the basal to apical direction. Based on our findings, we propose that system L functions as influx and/or efflux transport machinery displaying a greater propensity for the outward transport of large and small NAAs. Astrocytes appeared to modulate the transcriptic expression and uptake functionalities of system L, but not the transport activities. Copyright © 2008 John Wiley & Sons, Ltd. [source] Tissue modeling following implant placement in fresh extraction socketsCLINICAL ORAL IMPLANTS RESEARCH, Issue 6 2006Mauricio G. Araújo Abstract Objective: To study whether osseointegration once established following implant placement in a fresh extraction socket may be lost as a result of tissue modeling. Material and methods: Seven beagle dogs were used. The third and fourth premolars in both quadrants of the mandible were used as experimental teeth. Buccal and lingual full-thickness flaps were elevated and distal roots were removed. Implants were installed in the fresh extraction socket. Semi-submerged healing of the implant sites was allowed. In five dogs, the experimental procedure was first performed in the right side of the mandible and 2 months later in the left mandible. These five animals were sacrificed 1 month after the final implant installation. In two dogs, the premolar sites on both sides of the mandible were treated in one surgical session and biopsies were obtained immediately after implant placement. All biopsies were processed for ground sectioning and stained. Results: The void that existed between the implant and the socket walls at surgery was filled at 4 weeks with woven bone that made contact with the SLA surface. In this interval, (i) the buccal and lingual bone walls underwent marked surface resorption and (ii) the height of the thin buccal hard tissue wall was reduced. The process of healing continued, and the buccal bone crest shifted further in the apical direction. After 12 weeks, the buccal crest was located>2 mm apical of the marginal border of the SLA surface. Conclusion: The bone-to-implant contact that was established during the early phase of socket healing following implant installation was in part lost when the buccal bone wall underwent continued resorption. [source] | ||||||||||