Search

Objectives: The gap that develops at the interface of dentin composite restoration during the polymerization of the resin can be subsequently filled by fluid filtrating from the pulp via the dentinal tubules. This in vitro study was designed to determine the volume of such a gap, at the occlusal floor of class I restoration and as a result of different dentin treatments and restoration procedures., Methods: Fifty-six human third molars had their pulp chambers first sealed and connected to a hydraulic apparatus permitting microlitre fluid shift recordings. The teeth then received class I cavities of uniform dimensions and were sampled into nine groups for three dentin treatments (bonding with a dentin bonding agent, lining with a resin modified light-cured glass ionomer, lining with a zinc phosphate cement) and three restoration procedures (Bulk placement of the composite material, Multilayer, Indirect inlay). Fluid displacements were recorded during the filling procedures and stopped 30 min after the completion of the restorations., Results: Dentin bonding agent treated cavities consistently presented the smallest gap volumes, followed by the GI and the ZnPO4 lined specimen. Multilayer and Indirect restoration techniques reduced the formation of gaps., Conclusions: None of the materials or techniques tested assured a gap-free interface and more effort should be directed at increasing the adhesive and sealing properties of restorative materials to be placed on the dentin.

Cavities were prepared in human premolars scheduled for extraction for orthodontic reasons. The smear layer was removed from the dentin surface by acid etching, and the cavity was sealed using a hollow chamber. The chamber was filled with sterile saline solution and connected via tubing to a hydraulic circuit featuring an adjustable pressure reservoir and a device that measures fluid movement across dentin. In the absence of any exogenous pressure, all cavities exhibited an outward fluid flow rate of 0.36 microliters min-1 cm-2. As exogenous pressure was applied to the cavity, the outward flow slowed. The exogenous pressure that stopped outward fluid flow was taken to be equal to normal pulpal tissue pressure. The mean value was 14.1 cm H2O in five teeth. This simple method permits measurement of dentinal fluid flux, the hydraulic conductance of dentin, and estimates pulpal tissue pressure.

239 noncarious human teeth, freshly extracted (from patients aged 10 to 78 years), were prepared in order to examine microscopically the effects of aging on the pulp-dentinal complex at crown and root level. Microscopical observations included the following elements: predentin, odontoblastic layer with capillaries, pulpal volume, fibro-dentin, collagen fibres, blood vessels, cells and pulpal calcifications. Results showed a gradual narrowing of the circumference of the pulp volume with increasing age, due to the continual apposition of dentin. Dystrophic or degenerating calcifications were also noted alongside compression of collagen fibres (giving an appearance of fibrosis). However, the radicular vascularisation is still effective by observing the persistence of an anabolic activity (fibrodentin apposition) at these levels. These findings demonstrate the physiologic and the pathologic evolution of the pulp-dentinal complex.

The purpose of this study was to establish a correlation between dentinal hypersensitivity and tissular modifications of the pulp-dentinal complex at the level of cervical abrasions. 65 freshly extracted human teeth (from patients aged 20 to 80 years) presenting cervical abrasions without carious lesions were prepared in order to be examined histologically (31 teeth) and by scanning electron microscopy (34 teeth). Open tubules were present on the abraded surfaces in 83.3% of the specimens with presence of cytoplasmic processes in 78.46% of the cases without any correlation with tooth age and depth of the abrasions. The sensitivity could be partially explained by the persistence of cervical dentinal permeability. This permeable dentin seems to be susceptible to mechanical, chemical and bacterial irritations, no matter how thick the reactional dentin is. In the absence of any reliable and biological product capable to seal efficiently the open tubules, only nonabrasive hygiene methods can preserve the integrity of cervical dental tissues.

50 microradiographs taken in a standardized manner of midsagittal ground sections of teeth of individuals aged 18 to 56 years were densitometrically evaluated along a track passing through enamel, dentine and an aluminium stepwedge. Semi-quantitative analysis of mineral density uniformly showed an irregular platform representing circumpulpal dentine and a peripheral down slope in the region of the amelodentinal junction, representing mantle dentine. The width of this less mineralized peripheral zone measured on densitometric recordings averaged 150 microns (+/- 50). Quantitative analysis of the two dentinal regions permitted the calculation of the mineral content in terms of volume percentage using both a graphic method and an electronic computer method. The sections were also examined by polarized light microscopy which clearly visualized the presence of peripheral mantle dentine. The mean mineral density of circumpulpal dentine was 46% according to both the graphic and the computer methods; mantle dentine yielded means close to 42% according by both methods. The 4% difference in density between circumpulpal dentine and mantle dentine proved to be statistically significant; there was no significant difference between the means obtained graphically and those obtained electronically. The need for further investigation of this region of the amelodentinal junction was stressed.

To compare the effectiveness of different irrigation procedures on the removal of the smear layer, 40 curved canals were manually prepared in vitro under copious irrigation with 3 per cent NaOCl. Ten canals served as controls. The remaining 30 were equally distributed in three experimental groups and subsequently irrigated with the following: ultrasound with NaOCl; EDTA; ultrasound with EDTA. In the scanning electron microscope, the appearance of the smear layer was rated over the distribution of dentinal tubule openings for the coronal, middle and apical segments of the canals. Irrigation with NaOCl produced consistently smeared surfaces. Ultrasonic stirring of NaOCl removed the smear layer moderately, while EDTA produced almost smear-free surfaces. Ultrasound in association with EDTA did not enhance the dissolving capability of this chelating agent. A definite decline in the efficiency of the irrigation procedures was also observed along the apical part of the canals.