An Introduction to Silanes and Their Clinical Applications in Dentistry

Purpose: This overview presents a description of organofunctional trialkoxysilane coupling agents (silanes), their chemistry, properties, use, and some of the main clinical experiences in dentistry. Materials and Methods: The main emphasis was on major dental journals that have been reviewed from 1958 up to the latest research news from 2002. A MEDLINE search with the key words “dental silanes” was used. Special silane literature and journals outside dentistry were also cited. Results: The main emphasis is on the use of silanes in prosthetic and restorative dentistry. Clinical relevance was based mainly on either short- or long-term tests. The interpretation of various results is not given, mainly because of controversial observations that may be very difficult to explain. Nevertheless, the majority of the clinical results pointed to silanes playing a significant role in the adhesion process. Silane reaction mechanisms were not entirely understood, and there exist several theories for bonding mechanisms for silanes and substrates. Conclusion: Dental materials offer a continuously challenging forum for silanes, and silanes will play an essential role in material developmen

Assessment of CAD-CAM polymers for digitally fabricated complete dentures

Statement of problemInformation on the mechanical properties of the materials used for manufacturing computer-engineered complete dentures is scarce.PurposeThe purpose of this in vitro study was to evaluate the mechanical properties of 3 prepolymerized polymethyl methacrylate (PMMA) resins used in the fabrication of computer-aided design and computer-aided manufacturing (CAD-CAM) milled complete dentures (CDs), as well as 2 denture base polymers used for conventionally fabricated CDs.Material and methodsThree CAD-CAM materials were evaluated: Degos Dental L-Temp, IvoBase CAD, and Zirkonzahn Temp Basic Tissue. Two materials used for conventionally manufactured dentures were also included as controls (Palapress and Paladon 65). Each material type was sectioned into bars for flexural strength, nanohardness, elastic modulus, and surface microhardness evaluation (n=8/material). Half of the specimens were stored in water for 30 days, while the other half was dry-stored. A 2-way ANOVA was conducted to detect the effect of material and storage on the evaluated properties (α=.05). Linear contrasts were conducted to compare the differences among the 3 types of CAD-CAM material and the conventional ones.ResultsMaterial type and storage had a significant influence on the flexural strength, nanohardness, elastic modulus, and surface hardness of the materials investigated (PP=1.000). In terms of nanohardness, no difference was found when comparing Palapress with Paladon, as well as IvoBase CAD with Zirkonzahn Temp Basic (P=1.000). A nonsignificant interaction in terms of surface hardness was also found between IvoBase CAD and Palapress (P=.575).ConclusionsThe tested materials showed variation in their mechanical properties, with satisfactory behavior of the CAD-CAM materials. However, the results obtained when testing the materials used for the conventional fabrication of complete dentures suggest that their use might still be advisable.</div

Silane-Treated E-Glass Fiber-Reinforced Telechelic Macromer-Based Polymer-Matrix Composites

The aim of this in vitro study was to investigate the water sorption and flexural properties of fiber reinforced composites (FRC) prepared from telechelic macromer extended urethane dimethacrylate (PEG-400-E-UEDMA)(PEG), hydroxypropyl methacrylate (HPMA) and E-glass fibers. Three experimental groups of test specimens based on poly(PEG-400-E-UEDMA-HPMA) polymer matrices and continuous unidirectional E-glass fibers were light polymerized and stored in deionized water for 0, 4, 12 or 24 weeks. The weight ratios (%) of PEG-HPMA were 27.5–70.5, 49.0–49.0 and 70.5–27.5 with an initiator-activator percentage of 1.0–1.0. After each time period of storage the water absorption and flexural properties were measured. There were six test specimens in each of the test groups (N = 6) and the specimen’s fracture surfaces were analyzed using scanning electron microscopy (SEM). All the PEG-HPMA groups exhibited the highest water absorption at the time point of two days (5.5 to 6.4 %), which thereafter decreased to the level of 3.8–4.7 % at the time point of 30 days. The flexural strength varied from dry specimens’ 128 to 283 MPa to the 30 days water-stored specimens’ of 30 to 49 MPa. The flexural modulus exhibited values from 7.9 to 14.8 GPa (dry specimens) and ca. 0.5 to 1.8 GPa after 30 days of water-storage. Both the flexural strength and modulus decrease dramatically with a longer water storage time. The SEM images showed good adhesion between the fibers and the resin matrix. In the wet conditions, the telechelic macromer based hydrophilic PEG polymer-matrix FRCs formed a plasticized composite that decreased the flexural properties

A structured analysis of in vitro failure loads and failure modes of fiber, metal, and ceramic post-and-core systems.

Item does not contain fulltextPURPOSE: This study sought to aggregate literature data on in vitro failure loads and failure modes of prefabricated fiber-reinforced composite (FRC) post systems and to compare them to those of prefabricated metal, custom-cast, and ceramic post systems. MATERIALS AND METHODS: The literature was searched using MEDLINE from 1984 to 2003 for dental articles in English. Keywords used were (post or core or buildup or dowel) and (teeth or tooth). Additional inclusion/exclusion steps were conducted, each step by two independent readers: (1) Abstracts describing post-and-core techniques to reconstruct endodontically treated teeth and their mechanical and physical characteristics were included (descriptive studies or reviews were excluded); (2) articles that included FRC post systems were selected; (3) in vitro studies, single-rooted human teeth, prefabricated FRC posts, and composite as the core material were the selection criteria; and (4) failure loads and modes were extracted from the selected papers, and failure modes were dichotomized (distinction was made between "favorable failures," defined as reparable failures, and "unfavorable failures,"defined as irreparable [root] fractures). RESULTS: The literature search revealed 1,984 abstracts. Included were 244, 42, and 12 articles in the first, second, and third selection steps, respectively. Custom-cast post systems showed higher failure loads than prefabricated FRC post systems, whereas ceramic showed lower failure loads. Significantly more favorable failures occurred with prefabricated FRC post systems than with prefabricated and custom-cast metal post systems. CONCLUSION: The variable "post system" had a significant effect on mean failure loads. FRC post systems more frequently showed favorable failure modes than did metal post systems

Computed tomography: Why use it in small animal practice?

The influence of various drying time of a commercial silanes on the shear bond strength of a composite resin to silica-coated base and noble alloys was discussed. The drying time of MPS silane on tribochemically silica coated base and noble alloys did not show a significant difference in the bond strength of resin composite. The flow of work was optimized by reducing the drying time of MPS silane to 1 min for both base and noble alloys. It was observed that the bond strengths of resin composite to base alloys were higher than the bond strength of noble alloys at 2,3 and 5 min.link_to_subscribed_fulltex