The restoration of endodontically treated teeth is a topic that is extensively studied and yet remains controversial. This article emphasizes the characteristics of endodontically treated teeth and some principles to be observed when restorations of these teeth are planned. It was concluded that the amount of remaining coronal tooth structure and functional requirements determine the best way to restore these teeth, indicating the material to be used, direct or indirect restorations, associated or not to posts.

Several impression materials are available in the Brazilian marketplace to be used in oral rehabilitation. The aim of this study was to compare the accuracy of different impression materials used for fixed partial dentures following the manufacturers' instructions. A master model representing a partially edentulous mandibular right hemi-arch segment whose teeth were prepared to receive full crowns was used. Custom trays were prepared with auto-polymerizing acrylic resin and impressions were performed with a dental surveyor, standardizing the path of insertion and removal of the tray. Alginate and elastomeric materials were used and stone casts were obtained after the impressions. For the silicones, impression techniques were also compared. To determine the impression materials' accuracy, digital photographs of the master model and of the stone casts were taken and the discrepancies between them were measured. The data were subjected to analysis of variance and Duncan's complementary test. Polyether and addition silicone following the single-phase technique were statistically different from alginate, condensation silicone and addition silicone following the double-mix technique (p ≤ .05), presenting smaller discrepancies. However, condensation silicone was similar (p ≥ .05) to alginate and addition silicone following the double-mix technique, but different from polysulfide. The results led to the conclusion that different impression materials and techniques influenced the stone casts' accuracy in a way that polyether, polysulfide and addition silicone following the single-phase technique were more accurate than the other materials.Descriptors: Dental impression materials; Dental impression technique; Fixed partial denture.

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Aim: To evaluate the loss of applied torque (detorque) values in cast and pre-machined abutments for external hex abutment/implant interface of single implant-supported prostheses subjected to mechanical cycling. Methods: Ten metal crowns were fabricated using two types of UCLA abutments: cast and pre-machined with metal base in NiCrTi alloy and tightened to regular external hex implants with a titanium alloy screw, with an insertion torque of 32 N.cm, measured with a digital torque gauge. Samples were embedded with autopolymerizing acrylic resin in a stainless steel cylindrical matrix, and positioned in an electromechanical machine. Dynamic oblique loading of 120 N was applied during 5 x 10 5 cycles. Then, each sample was removed from the resin and detorque values were measured using the same digital torque gauge. The difference of the initial (torque) and final (detorque) measurement was registered and the results were expressed as percentage of initial torque. The results of torque loss were expressed as percentage of the initial torque and subjected to statistical analysis by the Student's t-test (p<0.05) for comparisons between the test groups. Results: Statistical analysis demonstrated that mechanical cycling reduced the torque of abutments without significant difference between cast or pre-machined UCLA abutments (p=0.908). Conclusions: Within the limitations of this in vitro study, it may be concluded that the mechanical cycling, corresponding to one-year use, reduced the torque of the samples regardless if cast or pre-machined UCLA abutments were used.

PURPOSE.The aim of the present study was to evaluate if a smaller morse taper abutment has a negative effect on the fracture resistance of implant-abutment connections under oblique compressive loads compared to a conventional abutment. MATERIALS AND METHODS. Twenty morse taper conventional abutments (4.8 mm diameter) and smaller abutments (3.8 mm diameter) were tightened (20 Ncm) to their respective implants (3.5 × 11 mm) and after a 10 minute interval, implant/abutment assemblies were subjected to static compressive test, performed in a universal test machine with 1 mm/min displacement, at 45�inclination. The maximum deformation force was determined. Data were statistically analyzed by student t test. RESULTS. Maximum deformation force of 4.8 mm and 3. Cafe′ , s/n, Monte Alegre, Ribeirão Preto -SP, Brazil. CEP 14040-904 Tel. 55 (16) 3602-4005: e-mail, renata@forp.usp.br Received June 5, 2012 / Last Revision July 26, 2012 / Accepted August 8, 2012 screwed prostheses, allowing change of planning after abutment placement. Thus, the hypothesis to be studied is that abutments of reduced diameter presents fracture resistance similar to conventional abutments. The aim of the present study was to evaluate fracture resistance of these implant-abutment connections under oblique compressive loads. MATERIALS AND METHODSTwenty morse taper implants (3.5×11mm, Pross, Dabi Atlante, Ribeirão Preto, Brazil) were embedded in stainless steel cylinders of 21.3 mm in diameter and 25.6mm in height simulating 3 mm osseous resorption.6 Flex abutments (Pross, Dabi Atlante) measuring 3.8 mm (n = 10) and 4.8 mm (n = 10) in diameter (Fig. 1) were installed into the implants with 20 Ncm torque, as recommended by the manufacturer, measured by a digital torquemeter (TQ 680, Instrutherm Measure Instruments, São Paulo, Brazil). Oblique compressive loading tests were performed in a universal testing machine (DL-2000, EMIC, São Jose ′ dos Pinhais, Brazil). Tests were performed using 20 sets (10 implants/3.8 mm abutments and 10 implants/ 4.8 mm abutments) positioned at 45 degree angle (Fig. 2), using a load cell of 1,000 kgf and 1 mm/min speed. The loading point was at a distance of 11 mm from cylinder surface.3 The values of maximum deformation force and fracture resistance were noted. The data were analyzed by Student's t test using SPSS software (version 17.0, SPSS Inc., Chicago, IL, USA). RESULTSMaximum deformation force of 4.8 mm and 3.8 mm abutments are presented in Table 1. No fractures were noted after mechanical test. Statistical analysis demonstrated that the evaluated abutments were statistically similar (P=.230), as expected because the diameter where bending occur was the same. Fig. 3 represents implant/abutment sets after mechanical test. The apparent difference in abutment flexural dynamics was suggested as a result of higher head deformation in narrow abutments.The Fig. 4 represents longitudinal section of implant/abutment sets before (A and B) and after (C and D) mechanical test. DISCUSSIONThe intimate contact between im...