[Microbial permeability of dentin]. / Mikrobiake diaperatoteta tes odontines.

This is a review of the literature about the contemporary aspects of microbial permeability of dentin. They are discussed the factors that are responsible for this question and analytically: the structure of dentin, the composition of dentin in organic and inorganic ingredients, the response mechanisms of dentin, that is the irritation dentin and sclerotic dentin, the hypermineralized zone under carious lesions, the role of saliva and dentinal fluid, the role of pulp and its microcirculation against the invasion of microbes and, the role of smear layer. Also this article refers to the immunological reaction of the pulp and finally to the role of dentist in the permeability of dentin, because the more conservative is a tooth preparation the less is the permeability of dentin. In conclusion, the microbial permeability of dentin is a very complicated biological phenomenon that needs more study and further investigations.

[Antimicrobial action of dental materials used in operative dentistry: a review]. / Antimikrobiake drase odontiatrikon ylikon, pou chresimopoiountai sten odontike cheirourgike.

This is a review of the literature about the antimicrobial action of dental materials used in operative dentistry. There are referred to the usefulness of the antimicrobial action of dental materials, and to the methods used by the investigators for the study of the antimicrobial properties. The methods used were: the examination of the in vitro antimicrobial action of the materials against several microbes, The in vivo antimicrobial action of the materials against the microbes that are enclosed underneath them in dental cavities, where some carious material was left on the floor of the cavities. Some other methods, as so as the adsorption of microbes on the experimental materials, in vivo and in vitro. There are presented the results of a lot of investigators for the antimicrobial action of dental amalgams, composite resins, silicate cements, glass-ionomer cements, zinc-phosphate, zinc oxide-eugenol and polycarboxylate cements, calcium hydroxide bases and also for varnishes and liners, since the time of Miller (1890) up to now. From these researches we can come to the following conclusions: 1) All dental materials have some antibacterial activities against several microbes when they are freshly mixed. Their action reduces with the past of time. 2) The responsible antibacterial factors are unknown. May be more than one factors. 3) In clinical practice it is not known what material is better, because the conditions are different from tooth to tooth and from mouth to mouth. 4) More researchers are necessary for this purpose because the antibacterial properties must be regarded as a part of the other biological properties of dental materials and the recurrent caries may be inhibited because of the antibacterial properties of filling and base materials.

Coronal fractures in posterior teeth.

Coronal fractures of posterior teeth are not rare in clinical practice. Most of the time they constitute a restorational problem for the clinician, since they usually end below the free gingival crest. Two hundred coronal fractures of posterior teeth were examined in this study, with respect to several factors. Some of the factors were the sex and age of the patient, type and location of the tooth, and vitality of the pulp. The results showed that frequency of fractures is not influenced by the sex or age of the patient, the type or location of the tooth, or the vitality of the pulp. Factors that significantly affect the appearance of a fracture include caries, restored surfaces, and tooth morphology. Lingual cusps fracture more often than buccal cusps, fractures ended more frequently above or at the gingival crest in teeth with vital pulps, and in nonvital teeth fractures ended more frequently below the crest. Conservative cavity designs for tooth restorations and conservative access to the root canals for endodontic treatment will decrease the frequency of tooth or restoration fracture.

[New aspects for the caries of deep cavities]. / Eugchrones apopseis gia ten teredona stis batheies koilotetes.

This article refers to the contemporary aspects about the carious lesions in the deepest parts of a cavity near the pulp. In these situations the problem that arises is to how deeply this carious dentine should be excavated without the risk of destroying the pulp. On this question there have been expressed two divergent opinions based also on two divergent theories. The one theory supports that during the carious process the microorganisms proceed the decalcification of the dentin, whereas the other theory supports the opposite view. According to the new aspects, in acute carious lesions the decalcification proceeds the bacteria, while in chronic caries the microorganisms, the discoloration and the bacterial invasion are closer to each other. This article also refers to the microflora of deep carious lesions and to the fate of bacteria that remain under the fillings. From this paper we come to the following conclusions: 1) In certain clearly defined conditions some carious dentine should be left at the base of a cavity in order to avoid the pulp exposure. But the periphery of the cavity must be unquestionably caries-free. 2) Few microbes always remain after the excavation of the carious cavities. 3) These microbes under well-fitting restorations do not proliferate and gradually die. 4) The defensive properties of the pulp play also a significant role, because pulp immunoglobulins are able to react upon invasive bacteria. 5) Finally, it must be emphasized that the clinical dentist must not underestimate the microbial role and action.

[Compressive and bend strength of experimental admixed high copper alloys]. / Antoche ste thlipse kai kampse peiramatikon meikton amalgamaton.

Mixed alloys for dental amalgams have been used mainly in the form of admixed alloys, where eutectic spheres are blend with conventional flakes. In the present study the compressive strength, bend strength and microstructure of two high-copper alloys (Tytin, Ana-2000) is compared with three experimental alloys prepared of the two high copper by mixing them in proportions of 3:1, 1:1 and 1:3 by weight. The results revealed that experimental alloys inherited high early and final strength values without any significant change in their microstructure.