An evaluation was made of the abrasive wear of six composite thermofixed dental resins subjected to different polymerization times. The method of evaluation was based on sharpness measurements to quantify the abrasive wear resistance of the resins. To this end, a test bench was built, consisting of a rotating porcelain cylinder that wears out a resin-coated cylinder placed above it, thus causing vertical displacement of the contact as the wear progresses. The values of vertical displacement, i.e., the input variables, were read and recorded by means of a computer program to obtain the sharpness values. These data indicated that the resins displayed different behaviors as a function of the polymerization times applied, reinforcing the importance of using a practical and rapid method of analysis in order to ensure that the behavior of new materials is fully understood before they are launched on the market.

In long-term oral rehabilitation treatments, resistance of provisional crowns is a very important factor, especially in cases of an extensive edentulous distal space. The aim of this laboratorial study was to evaluate an acrylic resin cantilever-type prosthesis regarding the flexural strength of its in-balance portion as a function of its extension variation and reinforcement by two types of fibers (glass and polyaramid), considering that literature is not conclusive on this subject. Each specimen was composed by 3 total crowns at its mesial portion, each one attached to an implant component (abutment), while the distal portion (cantilever) had two crowns. Each specimen was constructed by injecting acrylic resin into a two-part silicone matrix placed on a metallic base. In each specimen, the crowns were fabricated with either acrylic resin (control group) or acrylic resin reinforced by glass (Fibrante, Angelus) or polyaramide (Kevlar 49, Du Pont) fibers. Compression load was applied on the cantilever, in a point located 7, 14 or 21 mm from the distal surface of the nearest crown with abutment, to simulate different extensions. The specimen was fixed on the metallic base and the force was applied until fracture in a universal test machine. Each one of the 9 sub-groups was composed by 10 specimens. Flexural strength means (in kgf) for the distances of 7, 14 and 21 mm were, respectively, 28.07, 8.27 and 6.39 for control group, 31.89, 9.18 and 5.16 for Kevlar 49 and 30.90, 9.31 and 6.86 for Fibrante. Data analysis ANOVA showed statistically significant difference (p<0.05) only regarding cantilever extension. Tukey's test detected significantly higher flexural strength for the 7 mm-distance, followed by 14 and 21 mm. Fracture was complete only on specimens of non-reinforced groups.

The purpose of this study was to evaluate the accuracy of the respective dies after polyether elastomeric procedure in the presence or absence of cervical contact of the acrylic resin shell with the cervical region, establishing a comparison to dies obtained with stock trays. This study consisted of three groups with 10 specimens each: 1) acrylic copings without cervical contact, (cn); 2) acrylic copings with cervical contact (cc); 3) perforated stock tray, (st). The accuracy of the resulting dies was verified with the aid of a master crown, precisely fit to the master steel die. ANOVA test found statistically significant differences among groups (p<0.001). Tukey's test found that the smallest discrepancy occurred in group cn, followed by cc, while the st group presented the highest difference (cc x cn: p=0.007; st x cn: p<0.001; st x cc: p<0.001).

This work presents a proposal to assess the abrasive wear of composite resins available in the national market, which are materials largely used in dental clinics for functional and aesthetic tooth restorations. This was achieved by utilizing an experimental set-up on which a dynamic disc covered with proper porcelain (representing hardness close to the human teeth) wears a static disc covered with the resin tested under a constant and pre-determined load. Thus, by means of this set-up and keeping a behavioral status needed to the calculus for all tests, the aggressiveness (referred as to letter k) for all tests was analyzed. Due to the fact that resin characteristic revels how weary the material has become to the abrasion process with other harder material, the strength to wear for such resins was observed. Therefore, a real classification for these materials with their strength to the abrasion wear was made, which is a very important factor in the influence on their lifetime in dental restorations. The classification in descending order for those resins is presented as following: HELIOMOLAR RO, DURAFILL, FILTEK A110, HELIO FILL, POINT 4, FLOW IT; NATURAL FLOW, SUPRAFILL, FILTEK P60, FILTEK Z250, TETRIC FLOW, REVOLUTION, PRODIGY, TETRIC CERAM, HERCULITE, FILLMAGIC, TPH, CHARISMA, Z100.

This paper shows a study about the influence of type and number of sterilizations in the cutting ability of diamond points used in dentistry. As a result, the sterilization using the oven was the process, which didn't result in a decreasing in the cutting ability of the diamond points and, until the second sterilization, it resulted in a increasing of the cutting ability.

This article discusses the development of a test bench and a methodology for the study of composite resin abrasive wear. To evaluate the operation of the test bench and to compare the proposed methodology with other existing ones, a study was made of the five composites most commonly used by dentists. The one-way ANOVA method and the Tukey test were used to statistically analyze the results by multiple comparisons of the groups of resins tested. Using the proposed methodology, these resins were classified in an increasing order of abrasive wear strength, as follows: Charisma (the lowest abrasive wear strength), Tetric, TPH, Herculite and Z-100 (the highest abrasive wear strength) (p < 0.05). In comparison to other methodologies, the results of the proposed methodology presented the lowest coefficient of variation.