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PubMedDate not supplied

[Sclerotic dentin: aetio-pathogenetic hypotheses].

The situation with regard to current knowledge concerning dentinal sclerosis is examined. SEM and TEM examination of specimens of sclerotic dentin showed changes in diameter and tubular content leading to various degrees of obstruction of the lumen. There is agreement that this is due to the neo-apposition of peri-tubular dentin associated with intra-tubular deposition of crystals of Whitelockite, although the debate is still open on how such deposition may come about. Sclerotic casts are created in the tubules that may completely occlude the lumen or present a central cavity. In general these casts are surrounded by a thin fissure that has been variously interpreted. Many agree that sclerotic dentin has an increased mineral component, but without clarifying whether this is only a quantitative increase or whether it is also due to hyper-mineralisation of pre-existing dentin. An examination of the literature reveals numerous hypotheses surrounding the genesis of sclerotic dentin: some say it is due to passive phenomena of dissolution and precipitation whereas others suggest active involvement of the odontoblastic processes and the pulp. Since no studies have confirmed or confuted these theses, we may continue to think of dentinal sclerosis as a multifactorial event, due both to an increase in the thickness of peri-tubular dentin and to intra-tubular precipitation of calcium salts associated with mineralisation of the organic structures present in the lumen.

Calcium Phosphates↗

PubMedDate not supplied

SEM qualitative evaluation of four self-etching adhesive systems.

AIM: Recently, there has been a tendency to simplify bonding procedures. Current self-etching adhesives combine conditioning, priming and bonding functions thus reducing technique-sensitivity as well as the risk of making errors. Another important advantage of this approach is that it allows the resin to etch and infiltrate the substratum simultaneously thus reducing the risk of any discrepancy between these 2 processes. The aim of this study was to evaluate the bonding quality of 4 self-etching adhesives both on dentin and enamel using SEM analysis. METHODS: Twenty caries-free molars were used. The aprismatic enamel layer was removed from the internal and external slopes of the vestibular cusps using a diamond bur. Each molar was then transversally cut just above the pulp chamber using a diamond saw (composhave 4255 Intensiv) thus obtaining twenty coronal fragments and 20 radicular fragments. Radicular and coronal fragments were then randomly divided into 5 groups. Each group consisted of 8 specimens: 4 coronal and 4 radicular ones. A different adhesive system was used for each group following the manufacturer's directions. Each group underwent the same treatment: a thin layer of flowable composite was applied and then polymerized. Subsequently, a single 2 mm layer of microhybrid composite was added. The coronal and radicular portions were longitudinally cut to show the ground enamel/adhesive, unground enamel/adhesive and dentine/adhesive interfaces. Eighty specimens were obtained and prepared for SEM observation. Forty specimens with an adhesive/enamel interface and 40 with an adhesive/dentine interface. RESULTS: The interfacial exam frequently showed gaps between the substratum and the restoration. The final etching was generally satisfactory on ground enamel, while it was poor on unground enamel. Sometimes gaps were evident at the adhesive interface in dentin specimens. The tested adhesive systems produced a suitable hybrid layer and a lot of resin-tags were present. CONCLUSIONS: Self-etching adhesives showed an adequate adhesion to dentin. However, while they provided encouraging results on ground enamel they did not show to be dependable on unground enamel.

Dental Cements↗