Aim of the study was to compare the trimming and non-trimming variants of the microtensile technique with the 'micro' push-out test in the ability to measure accurately the bond strength of fiber posts luted inside root canals. In 15 endodontically treated teeth (Group A), fiber posts were cemented with Excite DSC in combination with Variolink II (Ivoclar-Vivadent). In 15 roots RelyX Unicem (3M-ESPE) was used for fiber post luting (Group B). Within each group, the bond strength of cemented fiber posts was assessed with the trimming and non-trimming microtensile technique, as well as with the push-out test. The great number of premature failures (16.9% in Group A, 27.5% in Group B) and the finding of high standard deviation values make questionable the reliability of the trimming microtensile technique. With the non-trimming microtensile technique, only five sticks were obtained from a total of six roots. The remaining specimens failed prematurely during the cutting phase. With the push-out test no premature failure occurred, the variability of the data distribution was acceptable, and regional differences in bond strength among root levels could be assessed. Relatively low values of bond strength were, in general, recorded for luted fiber posts. In conclusion, when measuring the bond strength of luted fiber posts, the push-out test appears to be more dependable than the microtensile technique.

The adhesion between fiber posts and root canal walls: comparison between microtensile and push-out bond strength measurements.

Geometric factors affecting dentin bonding in root canals: a theoretical modeling approach.

Monoblocks in root canals: a hypothetical or a tangible goal.

OBJECTIVE: The restoration of endodontically treated teeth has long been guided by empirical rather than biomechanical concepts. Part I of this literature review presented up-to-date knowledge about changes in tissue structure and properties following endodontic therapy, as well as the behavior of restored teeth in monotonic mechanical tests or finite element analysis. The aim of the second part is to review current knowledge about the various interfaces of restored, nonvital teeth and their behavior in fatigue and clinical studies. REVIEW METHOD: The basic search process included a systematic review of articles contained in the PubMed/Medline database, dating between 1990 and 2005, using single or combined key words to obtain the most comprehensive list of references; a perusal of the references of the references completed the review. RELEVANT INFORMATION AND CONCLUSIONS: Nonvital teeth restored with composite resin or composite resin combined with fiber posts resisted fatigue tests and currently represent the best treatment option. In comparison to rigid metal and/or ceramic posts, when composite resin or composite resin/fiber posts fail, the occurrence of interfacial defects or severe tooth breakdown is less likely. Adhesion into the root, however, remains a challenge because of the unfavorable ovoid canal configuration, as well as critical dentin microstructure in the deepest parts of the canal. Thus, specific combinations of adhesives and cements are recommended. The clinical performance of post-and-core restorations proved satisfactory overall, in particular with a contemporary restorative approach using composite resin and fiber posts. However, the clinical literature does not clearly isolate or identify exact parameters critical to success. This, in turn, emphasizes the importance and relevance of in vitro studies to further improve the quality and long-term stability of prosthetic foundations.

Biomechanical considerations for the restoration of endodontically treated teeth: a systematic review of the literature, Part II (Evaluation of fatigue behavior, interfaces, and in vivo studies).

The specific biomechanical alterations related to vitality loss or endodontic procedures are confusing issues for the practitioner and have been controversially approached from a clinical standpoint. The aim of part 1 of this literature review is to present an overview of the current knowledge about composition changes, structural alterations, and status following endodontic therapy and restorative procedures. The basic search process included a systematic review of the PubMed/Medline database between 1990 and 2005, using single or combined key words to obtain the most comprehensive list of references; a perusal of the references of the relevant sources completed the review. Only negligible alterations in tissue moisture and composition attributable to vitality loss or endodontic therapy were reported. Loss of vitality followed by proper endodontic therapy proved to affect tooth biomechanical behavior only to a limited extent. Conversely, tooth strength is reduced in proportion to coronal tissue loss, due to either caries lesion or restorative procedures. Therefore, the best current approach for restoring endodontically treated teeth seems to (1) minimize tissue sacrifice, especially in the cervical area so that a ferrule effect can be created, (2) use adhesive procedures at both radicular and coronal levels to strengthen remaining tooth structure and optimize restoration stability and retention, and (3) use post and core materials with physical properties close to those of natural dentin, because of the limitations of current adhesive procedures.

/pdf/biomechanical-considerations-for-the-restoration-of-20ki607nts.pdf

Biomechanical considerations for the restoration of endodontically treated teeth: a systematic review of the literature--Part 1. Composition and micro- and macrostructure alterations.

https://archive-ouverte.unige.ch/unige:85018/ATTACHMENT01

Microtensile bond strength between adhesive cements and root canal dentin.

For 6 months in 1963-64, one of us (L.J.B.) was in the South Seas to study broadly the problems of human biology, such as dental dysplasia related to malnutrition. Three types of these conditions were observed: one that prevailed in the deciduous dentitions, which the French call \"Cmelanodontia\" the Anglo-Saxons sometimes term \"odontoclasia,\" and whose clinical and histopathologic criteria have been little defined (Figs. 1, 2). Another condition, apparently unknown in the literature, refers to a dysplasia of the permanent teeth of Tahitians. The teeth in this condition are highly susceptible to rampant decay; we termed the dysplasia \"yellow teeth\" (Fig. 3). The third consisted of a mild-to-brown mottling of enamel found in the Polynesians ot distant islands who still adhere to traditional food habits (Fig. 4). Th. evidence that these three conditions are related to nutrition-it may be stated from the beginning-is only circumstantial, based on cross sectional, prevalencetype dental and nutrition surveys.\" 2 A more direct, chronologic approach consists in dating dental dysplasias histologically by the incremental lines of enamel and dentin, such as recently has been used by Bergman and others.3 This method is actually applied in our laboratory to complement our field studies, which will be described first.

Dental Dysplasia Related to Malnutrition, with Special Reference to Melanodontia and Odontoclasia

The anodic behavior of the Sn, the Sn8Hg (γ2) phase and the dental amalgam in a chloride solution has been investigated by means of the linear potential sweep and of the intensiostatic pulse method. The results indicate that anodic current varies with chloride concentration and that dissolution occurs prior to passivation of the electrode. The anodic charge needed for the passivation is smallest for the dental amalgam.

J.-M. Meyer

Papers

Microtensile bond strength between adhesive cements and root canal dentin.

Dental Dysplasia Related to Malnutrition, with Special Reference to Melanodontia and Odontoclasia

Potential Sweep and Intensiostatic Pulse Studies of Sn, Sng Hg and Dental Amalgam in Chloride Solution

Electrochemical behavior of Sn8Hg (gamma-2) and dental amalgam in a phosphate buffer solution

Electrochemical behavior of 8:1 tin-mercury alloy (gamma-2) and dental amalgam in a phosphate buffer solution