Bacterial Adhesion and Surface Roughness for Different Clinical Techniques for Acrylic Polymethyl Methacrylate.

This study sought to assess the effect of different surface finishing and polishing protocols on the surface roughness and bacterial adhesion (S. sanguinis) to polymethyl methacrylates (PMMA). Fifty specimens were divided into 5 groups (n = 10) according to their fabrication method and surface finishing protocol: LP (3 : 1 ratio and laboratory polishing), NF (Nealon technique and finishing), NP (Nealon technique and manual polishing), MF (3 : 1 ratio and manual finishing), and MP (3 : 1 ratio and manual polishing). For each group, five specimens were submitted to bacterial adhesion tests and analyzed by scanning electron microscopy (SEM). Two additional specimens were subjected to surface topography analysis by SEM and the remaining three specimens were subjected to surface roughness measurements. Data were compared by one-way ANOVA. The mean bacterial counts were as follows: NF, 19.6 ± 3.05; MP, 5.36 ± 2.08; NP, 4.96 ± 1.93; MF, 7.36 ± 2.45; and LP, 1.56 ± 0.62 (CFU). The mean surface roughness values were as follows: NF, 3.23 ± 0.15; MP, 0.52 ± 0.05; NP, 0.60 ± 0.08; MF, 2.69 ± 0.12; and LP, 0.07 ± 0.02 (µm). A reduction in the surface roughness was observed to be directly related to a decrease in bacterial adhesion. It was verified that the laboratory processing of PMMA might decrease the surface roughness and consequently the adhesion of S. sanguinis to this material.

Comparison of implant-abutment interface misfits after casting and soldering procedures.

The aim of this study was to compare vertical and horizontal adjustments of castable abutments after conducting casting and soldering procedures. Twelve external hexagonal implants (3.75 × 10 mm) and their UCLA abutments were divided according their manufacturer and abutment type: PUN (plastic UCLA, Neodent), PUC (plastic UCLA, Conexão), PU3i (plastic UCLA, Biomet 3i), and PUTN (plastic UCLA with Tilite milled base, Neodent). Three infrastructures of a fixed partial implant-supported bridge with 3 elements were produced for each group. The measurements of vertical (VM) and horizontal (HM) misfits were obtained via scanning electron microscopy after completion of casting and soldering. The corresponding values were determined to be biomechanically acceptable to the system, and the results were rated as a percentage. Statistical analysis establishes differences between groups by chi-square after procedures, and McNeman's test was applied to analyze the influence of soldering over casting (α ≤ .05). For the values of VM and HM, respectively, when the casting process was complete, it was observed that 83.25% and 100% (PUTN), 33.3% and 27.75% (PUN), 33.3% and 88.8% (PUC), 33.3% and 94.35% (PU3i) represented acceptable values. After completing the requisite soldering, acceptable values were 50% and 94.35% (PUTN), 16.6% and 77.7% (PUN), 38.55% and 77.7% (PUC), and 27.75% and 94.35% (PU3i). Within the limitations of this study, it can be concluded that the premachined abutments presented more acceptable VM values. The HM values were within acceptable limits before and after the soldering procedure for most groups. Further, the soldering procedure resulted in an increase of VM in all groups.

Impact of rehabilitation with metal-ceramic restorations on oral health-related quality of life.

Dental ceramics present excellent ability to reproduce the natural teeth regarding esthetic and biomechanics. Recently, due to the advancement of ceramic technology, metal-free restorations were developed. However, the traditional metal-ceramic restorations still present the requirements of high strength, long survival in the oral environment and favorable aesthetics. In this context, it is essential to know the specificity of each ceramic system available in order to apply it properly to various clinical situations. This report describes an integrated rehabilitation using metal-ceramic restorations of a patient at 50 years of age, who presented edentulous spaces, and previous unsatisfactory composite and amalgam restorations, and indirect metallic restorations, leading to compromised quality of life in both functional and psychosocial aspects. The impact on quality of life was measured using a generic instrument, OHIP-14, validated for the World Health Organization, which covers both the biological and the psychosocial dimensions. This instrument was applied to the patient before and after treatment. The patient had an overall OHIP-14 score of 28 before the treatment and after treatment the score decreased to 0, showing that dental and oral health conditions are factors that do impact on the quality of life. Rehabilitation has provided functional and aesthetic restorations, harmony of the stomatognathic system and improvement of life quality.

The effect of prosthesis length and implant diameter on the stress distribution in tooth-implant-supported prostheses: a finite element analysis.

PURPOSE: The goal of this study was to compare the stress distribution of tooth-implant-supported prostheses (TISPs) and solely implant-supported prostheses (ISPs) with two different pontic spans (three units versus four units). MATERIALS AND METHODS: Two-dimensional finite element models were constructed from the radiographs of polyester resin casts to mimic TISPs and ISPs. In all, eight models were analyzed. Occlusal loads of 15 N and 30 N were applied to the premolars and molars, respectively. The lateral and inferior borders of the models were constrained, with all degrees of freedom equal to zero. Eight-node elements with plane strain assumption were used for simulation. RESULTS: The authors found that TISPs with a short span and wider-diameter implants resulted in more homogenous stress distribution and less stress concentration on the implants. The long span yielded higher stress concentrations on the implants and between the pontics. CONCLUSIONS: In all models analyzed, stress concentrations were present in the implants.

Surface treatment of glass fiber and carbon fiber posts: SEM characterization.

Morphology, etching patterns, surface modification, and characterization of 2 different fiber posts: Gfp, Glass fiber post; and Cfp, carbon fiber were investigated by SEM analysis, after different surface treatments. Thirty fiber posts, being 15 Gfp and 15 Cfp were divided into a 5 surface treatments (n = 3): C-alcohol 70% (control); HF 4%-immersion in 4% hydrofluoric acid for 1min; H(3) PO(4) 37%-immersion in 37% phosphoric acid for 30s; H(2) O(2) 10%-immersion in 10% hydrogen peroxide for 20 min; H(2) O(2) 24%-immersion in 24% hydrogen peroxide for 10 min. Morphology, etching patterns, surface modification and surface characterization were acessed by SEM analysis. SEM evaluation revealed that the post surface morphology was modified following all treatment when compared with a control group, for both type of reinforced posts. HF seems to penetrate around the fibers of Gfp and promoted surface alterations. The Cfp surface seems to be inert to treatment with HF 4%. Dissolution of epoxy resin and exposure of the superficial fiber was observed in both post groups, regardless the type of reinforcing fiber, H(2) O(2) in both concentrations. Relative smooth surface area was produced by H(3) PO(4) 37% treatment, but with similar features to untreated group. Surface treatment of fiber post is a determinant factor on micromechanical entanglement to resin composite core. Post treatment with hydrogen peroxide resulted strength of carbon and glass/epoxy resin fiber posts to resin composite core.

Ceramic restoration repair: report of two cases.

The esthetic and functional rehabilitation of patients with multiple missing teeth can be performed with several techniques and materials. Ceramic restorations provide reliable masticatory function and good esthetics. However, fracture can occur in some cases due to their brittle behavior. In some cases, the replacement of an extensive prosthesis is a problem due to the high treatment cost. In this paper, two cases are presented, in which fractures occurred in extensive metal-ceramic fixed partial dentures, and their replacement was not possible. Ceramic repair was chosen and the sequences of treatment with and without presence of the ceramic fragment are also discussed. The cases illustrate that, in some situations, fractured metal-ceramic partial dentures can be successfully repaired when prosthetic replacement is not a choice. Prosthodontists must use alternatives that allow a reliable repair to extensive metal-ceramic fixed partial dentures. Surface preparation of the ceramic with hydrofluoric acid in conjunction with a silane coupling agent is essential for a predictable bonding of composite resin. The repair performed with composite resin is an esthetic and functional alternative when extensive fixed partial dentures cannot be replaced.

Mechanical properties of light-curing composites polymerized with different laboratory photo-curing units.

This study aimed to analyze the microhardness (KHN) and diametral tensile strength (DTS) of two hybrid resin composites (TPH Spectrum and Filtek Z250). To this end, the composites were polymerized with six laboratory photo-curing units (LPUs) and the results compared with an alternative polymerization method using conventional halogen light source in conjunction with additional polymerization in an autoclave (15 minutes/100 degrees C). LPUs were used following the manufacturers' instructions. Diametral tensile strength and Knoop hardness tests were conducted for all groups (n=5). Data were statistically compared using ANOVA and Tukey's test (alpha = 0.05). Among the LPUs, the one that provided light curing in conjunction with heat and nitrogen pressure resulted in a significant increase in KHN and DTS of resin composites. Between the resin composites, Filtek Z250 showed higher hardness values than TPH Spectrum. It was concluded that the use of alternative polymerization with conventional light polymerization and autoclave was feasible with a wide implication for the general public in terms of reduced dental treatment cost.

Effect of previous treatments on bond strength of two self-etching adhesive systems to dental substrate.

PURPOSE: The aim of this study was to evaluate the effectiveness of previous dental substrate treatments on the bond strength of two self-etching adhesives. MATERIALS AND METHODS: One hundred bovine incisors were sectioned at the cementoenamel junction. The labial tooth surface was ground to obtain flat superficial dentin. Teeth were randomly divided into two groups (n = 50): Clearfil Protect Bond and One Up Bond F. The specimens of each group were subdivided into five groups, according the dental substrate treatment, and then the adhesive system was applied as follows (n = 10): C: control, without previous treatment; TA: 37% phosphoric acid etching on enamel and dentin for 15 s; PA: 37% phosphoric acid etching only on enamel for 15 s; SB: Al2O3 sandblasting on dental surface; EDTA: enamel and dentin conditioning with 24% EDTA gel, pH 7.0. Resin composite blocks were fixed to the dental surfaces with dual-polymerized resin cement. Samples were sectioned in the mesiodistal direction and were trimmed to reduce the cross-sectional area to approximately 1.2 mm2. They were tested at a crosshead speed of 0.5 mm/min on a testing machine. Microtensile bond strength values from enamel, superficial dentin, and deep dentin were compared. Mean microtensile bond strength values were expressed in MPa and were analyzed by two-way ANOVA (2 x 3 x 5) and Tukey's tests. RESULTS: A significant difference was observed for interaction (p = 0.00001) among the factors. The highest mean bond strength to enamel was found with previous phosphoric acid etching, and to dentin when EDTA was previously applied. CONCLUSION: The most indicated previous treatment for increasing the bond strength to enamel and dentin simultaneously is EDTA for both self-etching adhesive systems used.

Effect of a bonding resin layer associated with a self-etching adhesive system on the bond strength of indirect restorations.

The aim of this study was to evaluate the influence of a low-viscosity bonding resin applied over a self-etching adhesive system on the microtensile bond strength (microTBS) of indirect restorations. Comparisons were made using One Up Bond F (OB) self-etching adhesive system, Single Bond (SB) one-bottle adhesive system and Scotchbond Multi Purpose Plus (SMP) bonding component. Thirty bovine incisors were extracted and decoronated at the cementoenamel junction. The labial surfaces were ground so that superficial dentin and deep dentin were exposed. The specimens were randomized to three groups (n=10): G1- OB; G2- OB + SMP; G3- SB. In G2, a layer of the SMP bonding was applied over the OB adhesive system. Indirect composite restorations were bonded using dual-cure cement under 500 g load for 5 min. The specimens were serially sectioned with a bonding area of +/- 1.0 mm(2) in 3 regions: enamel (E), superficial dentin (SD) and deep dentin (DD). The sticks were fixed with cyanoacrylate adhesive and submitted to microTBS test at a crosshead speed of 0.5 mm/min in a mechanical testing machine (EMIC DL 2000). The fractured specimens were examined under scanning electron microscopy to determine the failure mode. Data were analyzed by one-way ANOVA followed by Tukey's test (p<0.05). microTBS means (in MPa) were: G1/E: 15.5 +/- 3.5b; G1/SD: 22.7 +/- 7.6a; G1/DD: 19.4 +/- 9.4a; G2/E: 15.9 +/- 5.8b; G2/SD: 19.9 +/- 6.9a; G2/DD: 15.3 +/- 4.9a; G3/E: 23.2 +/- 7.3a; G3/SD: 20.4 +/- 8.2a; G3/DD: 19.1 +/- 8.7a. The results showed that the use of a low viscosity bonding resin did not affect the microTBS means when associated with a self-etching adhesive system. The self-etching adhesive system was significantly more efficient in dentin than in enamel, while the one-bottle system was significantly more efficient in enamel when compared to the self-etching adhesive system.