Development of nanobiosilicate, tricalcium phosphate and chlorhexidine materials for biomineralization with crystallographic similarity to hydroxyapatite and biomodified collagen.

OBJECTIVES: The aim of this work is to test experimental cements, doped with a silicate based bioactive nanoparticle (NanoBiosilicate). Methods, we synthesized a glass nanoparticle by Sol-Gel Stöber method, used to be incorporated in a dental material for endodontic uses. MATERIALS AND METHODS: We assess the mineralizing properties and biocompatibility. Besides the crystallography characterization of the resultant new crystals. Results, After analysis, and comparison with commercial materials, the material tested was similar in mechanical properties required by ISO, The ion release was effective after 2 hr. of setting and the novel material was cell compatible accepted by ISO. RESULTS: We found new formed Calcium Phosphate peaks in the spectroscopic analysis (FTIR), remarkably the crystals formed were comparable to hydroxyapatite when analyzed with a Selected Area Electron Diffractometer, with rings of 2.84 Å for 002, and the 2.77 Å is also visible for 210. The 6.83 Å and 6.88 Å, for respective 222 and 004. The incorporation of Chlorhexidine was not detrimental for this property, Significance, the features mentioned represented a progress in biomineralization field that was associated to an improved mineral structure formation with increased crystallographic similarity to natural hydroxyapatite. When chlorhexidine was added a favorable biomodification of the remaining collagen in dentinal walls and antimicrobial activity potential were also observed.

Effect of Tricalcium Silicate on Direct Pulp Capping: Experimental Study in Rats.

OBJECTIVES: Conduct a histological comparison of the pulp response to different materials, with a focus on the continuity and morphology of the mineralized barrier after direct pulp capping. MATERIALS AND METHODS: One hundred and eight maxillary first molars of 54 Wistar rats were subject to direct pulp capping and divided into three groups according to the materials used: calcium hydroxide (CH), mineral trioxide aggregate (MTA), and Biodentine. All cavities were sealed, and the animals were euthanized at 7, 14, and 21 days. Descriptive histological evaluation of the inflammation and formation of the mineralized barrier was performed. STATISTICAL ANALYSIS: Statistical analyses were performed using the Kruskal-Wallis test, which was complemented by the Dunn test; differences with p < 0.05 were considered statistically significant. RESULTS: The results showed that MTA and Biodentine elicited less intense inflammatory reactions than CH. With respect to the formation and quality of the dentin barrier formed, differences were observed at 21 days between the analyzed groups; the best results being obtained following treatment with MTA and Biodentine. CONCLUSION: MTA and Biodentine induced formation of a more continuous and uniform mineralized barrier with less intense pulp response than CH.

Bonding Strength of Luting Cement to Zirconia-Based Ceramic Under Different Surface Treatments.

OBJECTIVES: The aim of this study was to evaluate the bonding strength of self-adhesive luting cement to zirconia under different surface treatments. MATERIALS AND METHODS: Thirty-two zirconia samples were randomly divided into eight experimental groups based on the surface treatment employed (Control: no surface treatment; PMM: wear with diamond bur; JAT: blasting with glass beads; PMA: wear with a medium-roughness milling machine; Primer: primer application on the surface without treatment; PMM +Primer: PMM treatment plus primer application; JAT+Primer: JAT treatment plus primer application; and PMA+Primer: PMA treatment plus primer application). Cement cylinders were built on the ceramic surfaces, and the groups were subdivided according to the storage time employed (i.e., 24 hours or 60 days). After storage, the samples were subjected to microshear testing. STATISTICAL ANALYSIS: The Kruskal-Wallis test followed by the Dunn test was employed for comparison between the groups (p < 0.05). RESULTS: The PMM group yielded the optimal results and the mean values increased after both storage times following the primer application. The Control, PMA, and JAT groups gave similar results after 24 hours, while the JAT group gave superior results following primer application over this storage time. After 60 days of storage, all groups gave improved results following chemical treatment with a primer. CONCLUSION: It was concluded that mechanical preparation using the diamond bur followed by primer application significantly improved the bond strength between the ceramic and the luting cement.

Degradation of Adhesive-Dentin Interfaces Created Using Different Bonding Strategies after Five-year Simulated Pulpal Pressure.

PURPOSE: To compare after five-year simulated pulpal pressure (SPP) the degradation of adhesive-dentin interfaces created using two simplified adhesives applied with different bonding strategies. MATERIALS AND METHODS: A two-step self-etch (CSE: Clearfil SE Bond) adhesive was used as a control multistep adhesive. The tested experimental materials were two simplified adhesives, a one-step self-etch (CS3: Clearfil S3 Bond) and a self-priming etch-and-rinse adhesive (SB2: Adper Single-Bond 2). Half of the bonded specimens were submitted to microtensile bond strength (µTBS) testing after 24 h. The other half submitted to SPP for five years before µTBS testing. Nonfractured sticks were evaluated using transmission electron microscopy (TEM). Scanning electron microscopy (SEM) was used to evaluate silver-nitrate nanoleakage within the interface. Data were statistically analyzed by two-way ANOVA and Tukey's test (p < 0.05). RESULTS: Prolonged SPP induced bond-strength reduction for both SB2 and CS3. All bonding approaches showed increased nanoleakage after aging. The two simplified adhesives showed severe degradation at the resin-dentin interface. TEM revealed that the main degradation patterns for the etch-and-rinse adhesive SB2 was collagen breakdown, while polymer hydrolysis along with filler debonding was mainly observed in CS3. CONCLUSIONS: Simplified adhesives applied in etch-and-rinse mode are mainly characterized by hydrolysis and collagen degradation. In self-etch mode, simplified adhesives may principally show hydrolysis of the polymeric matrix and/or at the interface of fillers and coupling agent. The use of multistep self-etching adhesives may guarantee greater dentin bond durability compared to simplified adhesives.

A new arginine-based dental adhesive system: formulation, mechanical and anti-caries properties.

Secondary caries at the margins of composite restorations has been attributed to adhesive failure and consequent accumulation of cariogenic biofilms. OBJECTIVES: To develop and evaluate an etch-and-rinse adhesive system containing arginine for sustainable release and recharge without affecting its mechanical properties. Arginine metabolism by oral bacteria generates ammonia, which neutralizes glycolytic acids and creates a neutral environmental pH that is less favorable to the growth of caries pathogens, thus reducing the caries risk at the tooth-composite interface. METHODS: Experimental adhesives were formulated with methacrylate monomers and arginine at 5%, 7%, and 10% or no arginine (control). Adhesives were tested for: (i) mechanical properties of true stress (FS and UTS), modulus of elasticity (E), degree of conversion (DC), Knoop hardness number (KHN) and dentin microtensile bond strength (µ-TBS), (ii) arginine release and recharge, and (iii) antibacterial activities. Data was analyzed by t-test, one-way ANOVA and Tukey's tests. RESULTS: FS and UTS results showed no statistically significant differences between the 7% arginine-adhesive and control, while the results for E, DC, KHN and µ-TBS showed no difference among all groups. The 7% arginine-adhesive showed a high release rate of arginine (75.0µmol/cm2) at 2h, and a more sustainable, controlled release rate (up to 0.2µmol/cm2) at 30days. CONCLUSIONS: Incorporation of 7% arginine did not affect the physical and mechanical properties of the adhesive. Arginine was released from the adhesive at a rate and concentration that exhibited antibacterial effects, regardless of shifts in biofilm conditions such as sugar availability and pH. CLINICAL SIGNIFICANCE: Secondary caries is recognized as the main reason for failure of dental restorations. The development of an arginine-based adhesive system has the potential to dramatically reduce the incidence and severity of secondary caries in adhesive restorations in a very economical fashion.

Surface detail reproduction and dimensional accuracy of molds: influence of disinfectant solutions and elastomeric impression materials / Reprodução de detalhes da superfície e estabilidadedimensional de moldes: influência das soluçõesdesinfetantes e elastômeros

This study compared the surface detail reproduction anddimensional accuracy of molds after disinfection using 2% sodium hypochlorite, 2% chlorhexidine digluconate or 0.2% peracetic acid to those of molds that were not disinfected, forfour elastomeric impression materials: polysulfide (Light Bodied Permlastic), polyether (Impregum Soft), polydimethylsiloxane(Oranwash L) and polyvinylsiloxane (Aquasil Ultra LV). Themolds were prepared on a matrix by applying pressure, using aperforated metal tray. The molds were removed followingpolymerization and either disinfected (by soaking in one of thesolutions for 15 minutes) or not disinfected. The samples werethus divided into 16 groups (n=5). Surface detail reproductionand dimensional accuracy were evaluated using opticalmicroscopy to assess the 20 ­µm line over its entire 25 mm length. The dimensional accuracy results (%) were subjectedto analysis of variance (ANOVA) and the means were comparedby Tukey’s test (α=5%). The 20 ­µm line was completelyreproduced by all elastomeric impression materials, regardlessof disinfection procedure. There was no significant difference between the control group and molds disinfected with peraceticacid for the elastomeric materials Impregum Soft (polyether)and Aquasil Ultra LV (polyvinylsiloxane). The high­leveldisinfectant peracetic acid would be the choice material for disinfection.

Este estudo comparou a reprodução de detalhes da superfície e estabilidade dimensional de moldes obtidos após desinfecção utilizando hipoclorito de sódio 2%, digluconato de clorexidina 2%, ou ácido peracético 0,2% a moldes que não foram desinfetados com quatro elastômeros: polissulfeto (Light Bodied Permlastic), polieter (Impregum Soft), silicona reação porcondensação (Oranwash L) e silicona reação por adição (Aquasil Ultra LV). Os moldes foram preparados sobre matriz conten dolinhas de 20, 50 e 75 µm realizado sob pressão com moldeirade metal perfurada. Os moldes foram removidos após a polimerização e desinfetados (utilizando uma das soluções porimersão, armazenados em frascos fechados durante 15 minutos)ou não desinfetados. Assim, as amostras foram divididas em 16grupos (n=5). A reprodução detalhes da superfície e a precisão dimensional foram avaliadas usando microscopia óptica na linha 20 µm com 25 mm de comprimento, de acordo com a norma ISO 4823. Os resultados de precisão dimensional (%) foram submetidos à análise de variância (A NOVA) e as médias comparadas pelo teste de Tukey com 5% de nível de significância. A linha de 20 µm foi completamente reproduzida por todos os elastômeros, independentemente do processo de desinfecção. Não houve diferença estatisticamente significativa entre o grupo controle e moldes desinfetados com acido peracético para os elastômeros Impregum Soft (polieter) e Aquasil Ultra LV (siliconareação por adição). O desinfetante de alto nível ácido peracético seria o material de escolha para a desinfecção.

Bonding performance of experimental bioactive/biomimetic self-etch adhesives doped with calcium-phosphate fillers and biomimetic analogs of phosphoproteins.

OBJECTIVES: This study examined the bonding performance and dentin remineralization potential of an experimental adhesive containing calcium-phosphate (Ca/P) micro-fillers, and self-etching primers doped with phosphoprotein biomimetic analogs (polyacrylic acid-(PAA) and/or sodium trimetaphosphate-(TMP)). METHODS: Experimental self-etching primers doped with biomimetic analogs (PAA and/or TMP), and an adhesive containing Ca(2+), PO4(-3)-releasing micro-fillers (Ca/P) were formulated. Sound human dentin specimens were bonded and cut into sticks after aging (24h or 6 months) under simulated pulpal pressure (20cm H2O), and tested for microtensile bond strength (µTBS). Results were analyzed using two-way ANOVA and Tukey's test (p<0.05). Interfacial silver nanoleakage was assessed using SEM. Remineralization of EDTA-demineralized dentin was assessed through FTIR and TEM ultrastructural analysis. RESULTS: Application of the Ca/P-doped adhesive with or without dentin pre-treatments with the primer containing both biomimetic analogs (PAA and TMP) promoted stable µTBS over 6 months. Conversely, µTBS of the control primer and filler-free adhesive significantly decreased after 6 months. Nanoleakage decreased within the resin-dentin interfaces created using the Ca/P-doped adhesives. EDTA-demineralized dentin specimens treated the Ca/P-doped adhesive and the primer containing PAA and TMP showed phosphate uptake (FTIR analysis), as well as deposition of needle-like crystallites at intrafibrillar level (TEM analysis). SIGNIFICANCE: The use of Ca/P-doped self-etching adhesives applied in combination with analogs of phosphoproteins provides durable resin-dentin bonds. This approach may represent a suitable bonding strategy for remineralization of intrafibrillar dentin collagen within the resin-dentin interface.

Influence of adding nanoparticles on the hardness, tear strength, and permanent deformation of facial silicone subjected to accelerated aging.

STATEMENT OF PROBLEM: The efficiency of adding nanoparticles to silicone protection has proven to prevent color degradation. However, reports of other physical property changes in facial silicone are scarce. PURPOSE: The purpose of this in vitro study was to evaluate the influence of adding nanoparticles on the hardness, tear strength, and permanent deformation of a facial silicone. MATERIAL AND METHODS: Specimens were made for each test, with 140 for the hardness test, 140 for the permanent deformation test, but 280 for the rupture test. This higher number was due to the fact that the first 140 specimens were ruptured and unusable after the initial reading. ZnO, BaSO4, and TiO2 nanoparticles at concentrations of 1% and 2% of silicone were used, as well as specimens without nanoparticles that consisted of only oil paint and of only silicone. Outcomes were measured before and after 1008 hours of accelerated aging. Data were analyzed by nested analysis of variance (ANOVA) and Tukey honest significant differences test (α=.05). RESULTS: Results showed that the presence of nanoparticles influenced the properties of the assessed groups. The nanoparticles decreased hardness values. The highest values of tear strength were observed for the groups with addition of BaSO4. The 1% ZnO group without oil paint showed the lowest values of permanent deformation. CONCLUSIONS: Based on the findings of this in vitro study, the use of ZnO nanoparticles is recommended, since they did not negatively affect the properties of the materials evaluated.

Influence of alginate impression materials and storage time on surface detail reproduction and dimensional accuracy of stone models.

This study compared the surface detail reproduction and dimensional accuracy of stone models obtained from molds prepared using different alginate impression materials (Cavex ColorChange, Hydrogum 5, or Jeltrate Plus) and with different storage times (1, 3, and 5 days) to models from molds that were filled immediately with no storage time. The molds were prepared over a matrix containing 50-µm line, (ISO 1563 standard) under pressure with a perforated metal tray. The molds were removed 2 minutes after loss of sticky consistency and either filled immediately or stored in closed jars at 100% relative humidity and 37°C for 1, 3, or 5 days. The molds were filled with dental plaster (Durone IV). Surface detail reproduction and dimensional accuracy were evaluated using optical microscopy on the 50-µm wide line, which was 25 mm in length, according to ISO 1563 standard. The dimensional accuracy results (%) were subjected to analysis of variance. The 50-µm wide line (ISO 1563 standard) was completely reproduced by all alginate impression materials regardless of the storage time. There was no statistically significant difference in the mean dimensional accuracy values of stone models made from molds composed of different alginate impression materials and with different storage times (p = 0.989). In conclusion, storing the mold for five days prior to filling did not change the surface detail reproduction or dimensional accuracy of the alginates examined in this study.

Impact of hydrophilicity and length of spacer chains on the bonding of functional monomers.

OBJECTIVES: 10-Methacryloyloxy-decyl-dihydrogen-phosphate (10-MDP) is currently considered as one of the most effective functional monomers for dental bonding, this in part thanks to its long and relatively hydrophobic spacer chain, adequately separating the polymerizable from the phosphate functionalities. This study compared functional monomers with different spacer chains' length and hydrophilicity to 10-MDP on their dentin and enamel bonding performance. METHODS: Atomic absorption spectroscopy (AAS) was used to characterize the chemical interaction. Micro-tensile bond strength (µTBS) and fractographic analyses were performed after 24h and one year. Confocal micro-permeability and SEM nanoleakage assessments were also undertaken. The tested functional monomers were 2-MEP (2-carbon spacer), 10-MDP (10-carbon), 12-MDDP (12-carbon), MTEP (high hydrophilic polyether spacer chain) and CAP-P (intermediate hydrophilic ester spacer). RESULTS: AAS revealed clear differences (p<0.05) in monomer-calcium salt formation in this order: 12-MDDP=10-MDP>CAP-P>MTEP>2-MEP. The highest initial dentin µTBS was obtained using 10-MDP or 12-MDDP. After 1-year aging, a significant drop (p<0.05) in µTBS was observed for the adhesives with MTEP (enamel and dentin), 2-MEP (enamel) and CAP-P (enamel). MTEP presented the highest micro-permeability, while 2-MEP, CAP-P and MTEP showed increased nanoleakage after aging. SIGNIFICANCE: These outcomes showed that more hydrophilic and shorter spacer chains may compromise the chemical interaction with calcium and the dentin/enamel bonding performance.

The role of spacer carbon chain in acidic functional monomers on the physicochemical properties of self-etch dental adhesives.

OBJECTIVES: To evaluate the effects of acidic functional monomers with different hydrophilicity and spacer carbon chain length on the degree of conversion (DC), wettability (contact angle), water sorption (WS) and ultimate tensile strength (UTS) of experimental one-step self-etch adhesives (1-SEAs). METHODS: A series of standard resin blends was prepared with each formulation containing 15mol% of each acidic monomer. The structural variations of the acidic monomers were MEP (spacer chain with 2 carbons), MDP (10-carbons), MDDP (12-carbons), MTEP (more hydrophilic polyether spacer) and CAP-P (intermediate hydrophilicity ester spacer). Dumbbell-shaped and disc specimens were prepared and tested for UTS and WS, respectively. DC was assessed by FTIR, while the wettability of each 1-SEA was evaluated on glass slides and flat dentine surfaces. Results were analysed with one-way ANOVA and Tukey's test (p<0.05). RESULTS: The outcomes showed lower UTS for CAP-P, control blend and MEP than MTEP, MDDP and MDP (p<0.05). The degree of conversion was statistically similar for all resins (p=0.122). On dentine, the wettability was higher (lower contact angle) with the most hydrophilic monomer MTEP. Higher WS was attained using MTEP. Different lengths of the spacer chains did not result in different wettability and WS (p>0.05). CONCLUSION: At similar molar percentage, different acidic functional monomers induced similar degree of conversion and different UTS when included in a 1-SEA. However, the inclusion of highly hydrophilic monomer may increase the wettability on dentine and the WS.

Effect of photoactivation mode on the hardness and bond strength of methacrylate- and Silorane monomer-based composites.

PURPOSE: To evaluate the Knoop hardness (KH) and the bond strength (BS) at the tooth/restoration interface of conventional methacrylate- (Filtek Supreme) and silorane-based (Filtek P90) composites photoactivated by different methods using an LED Freelight 2. MATERIALS AND METHODS: Bond strength was tested in a universal testing machine by the "push-out" test in restored cavities measuring 2 × 1.5 × 2 mm with a C-factor of 2.2, prepared in 60 bovine teeth. To restore the cavities, the respective adhesive system of each composite was used (Single Bond 2 and P90 system adhesives). The composites were photoactivated by 3 different methods: continuous light: 40 s at 1000 mW/cm²; soft-start: 10 s at 150 mW/cm² + 38 s at 1000 mW/cm²; pulse delay: 5 s at 150 mW/cm², followed by a 3-min wait (without photoactivation) and 39 s at 1000 mW/cm². Before the push-out test was performed, the KH was analyzed at the top and bottom of the restorations. Data were statistically anaylzed using ANOVA and Tukey's test. RESULTS: The photoactivation methods produced no differences in BS or KH in the same composite, while Filtek P90 (28.0 MPa) showed higher BS values than Filtek Supreme (22.3 MPa) and a lower KH. CONCLUSION: The composite Filtek P90 was capable of increasing bond strength, but presented lower Knoop hardness.

Hydrolytic degradation of the resin-dentine interface induced by the simulated pulpal pressure, direct and indirect water ageing.

OBJECTIVES: The aim of this study was to compare the hydrolytic effects induced by simulated pulpal pressure, direct or indirect water exposure within the resin-dentine interfaces created with three "simplified" resin bonding systems (RBSs). METHODS: A two-step/self-etching (CSE: Clearfil SE Bond), one-step/self-etching (S3: Clearfil S3) and etch-and-rinse/self-priming (SB: Single-bond 2) adhesives were applied onto dentine and submitted to three different prolonged (6 or 12 months) ageing strategies: (i) Simulated Pulpal Pressure (SPP); (ii) Indirect Water Exposure (IWE: intact bonded-teeth); (iii) Direct Water Exposure (DWE: resin-dentine sticks). Control and aged specimens were submitted to microtensile bond strength (µTBS) and nanoleakage evaluation. Water sorption (WS) survey was also performed on resin disks. Results were analysed with two-way ANOVA and Tukey's test (p < 0.05). RESULTS: The µTBS of CS3 and SB dropped significantly (p < 0.05) after 6 months of SPP and DWE. CSE showed a significant µTBS reduction only after 12 months of DWE (p = 0.038). IWE promoted no statistical change in µTBS (p > 0.05) and no evident change in nanoleakage. Conversely, SPP induced a clear formation of "water-trees" in CS3 and SB. WS outcomes were CS3 > SB = CSE. CONCLUSION: The hydrolytic degradation of resin-dentine interfaces depend upon the type of the in vitro ageing strategy employed in the experimental design. Direct water exposure remains the quickest method to age the resin-dentine bonds. However, the use of SPP may better simulate the in vivo scenario. However, the application of a separate hydrophobic solvent-free adhesive layer may reduce the hydrolytic degradation and increase the longevity of resin-dentine interfaces created with simplified adhesives.

Pino anatômico com resina composta: relato de caso / Anatomic fiber post with composite resin: case report

O protocolo restaurador de dentes tratados endodonticamente é um desafio na odontologia adesiva atual, já que existem vários tipos de retentores intrarradiculares à disposição no mercado, com características ópticas e mecânicas que promovem um tratamento satisfatório. Dessa forma, a técnica de pino de fibra anatômico reembasado com resina composta direta torna-se eficiente para uso na clínica odontológica, especialmente em casos de condutos largos e tamanho reduzido de férula. Para tanto, o pino é limpo, aplica-se o silano e adesivo, além da resina composta não polimerizada para moldar o conduto radicular. Após, o pino é tratado novamente e cimentado com uma pequena espessura de linha de cimentação. Nesse artigo, o caso clinico abordará as etapas necessárias para a confecção do pino anatômico, além das estratégias de cimentação adesiva e a restauração com resina composta, trabalhando os conceitos da manutenção de uma delgada linha de cimentação para uma adequada reabilitação dental mantendo biomecânica e retenção do pino de fibra no interior do conduto radicular.

The restorative protocol for endodontically treated teeth is a challenge in adhesive dentistry, since there are several available types of intracanal posts with optical and mechanical characteristics that promotea satisfactory treatment. Thus, the anatomical fiber post technique is efficient for the use in dental practice, especially in cases of large root canals and small dental ferrules. So, the post is cleaned and then the silaneagent and adhesive system are applied, followed by the placement of the non-polymerized composite for root canal modeling. After this, the anatomical fiber post is treated again and followed by the luting procedure, showing a small cementation thickness. In this paper, the case report will address the necessary steps to realize the anatomical fiber post technique using strategies and adhesive cementation with composite resin restoration, working the concepts of maintaining a thin cement line and an adequate dental rehabilitation.

Effect of repeated microwave disinfections on bonding of different commercial teeth to resin denture base.

OBJECTIVE: To verify the influence of repeated microwave disinfections on the shear bond strength of two commercial types of teeth to acrylic resin, when the ridge lap surfaces were unmodified, bur abraded, bur grooved or etched by monomer. MATERIAL AND METHODS: Eighty specimens (n = 10) were adhered to the tooth ridge lap surface, polymerised in a water bath at 74°C for 9 h. Microwaved specimens were individually immersed in 150 ml of water and submitted to five simulated disinfections in a microwave oven calibrated at 650 W for 3 min. Control specimens were not microwave treated. Shear bond strength tests were performed in an Instron machine with a cross-speed of 1 mm/min. The fracture load values were transformed into shear bond strength as a function of the bonding area (0.28 cm(2)). Data were submitted to ANOVA and Tukey's test (α = 0.05). Fractured areas were classified as adhesive, cohesive (resin or tooth) or mixed failures. RESULTS: Repeated microwave disinfections increased the shear strength of the tooth/resin bond. Mechanical retention in microwaved and non-microwaved procedures improved the shear bond strength. CONCLUSIONS: The different commercial types of teeth influenced shear bond strength values, with Biotone teeth showing the lower values.

Effect of polymerization techniques on vertical dimension and tooth position in complete dentures.

Due to the changes in the composition and processing of acrylic resins, it seems appropriate to evaluate the influence of polymerization methods about the alteration of occlusal vertical dimension and the horizontal positioning of artificial teeth of total dentures. For this, 64 specimens were made, simulating a maxillary total denture waxed from a standard maxillary denture. The experimental samples were divided into two groups: Group 1 - The resins were submitted to polymerization in a hot water bath, Group 2 - The same resins were submitted to poly-merization by microwave energy. The samples were measured horizontally and vertically before and after the polymerization process. Based on the results, it can be concluded that there was no statistically significant difference between the conventional polymerization method and the polymerization method by microwave, related to the stability of occlusal vertical dimension and horizontal positioning of artificial teeth on the specimens evaluated.

Effect of ridge-lap surface treatments on the bond of resin teeth to denture base.

PURPOSE: To test in vitro the shear bond strength of resin teeth to an acrylic resin denture base given different ridgelap surface treatments. MATERIALS AND METHODS: Ninety rectangular dies were made with wax and traditionally invested in metallic or plastic flasks. The stone molds were covered with silicone, in which were included an acrylic molar with a wax stick fixed on the ridge lap surface. After deflasking, the wax sticks were removed, the teeth were cleaned with detergent, the ridge lap surface was submitted to different treatments (unmodified, bur-cut grooves, aluminum oxide particle sandblasting, monomer swelling, and primer swelling), and the teeth were replaced in the silicone molds. Metallic flasks were placed in a thermopolymerizing unit to polymerize heat-curing denture-base polymer, and plastic flasks were placed in a domestic microwave oven at 900 W to polymerize microwaveable denture base polymer. After deflasking, the specimens were submitted to the shear bond test in an Instron machine at a cross-speed of 1 mm/min. Results were submitted to ANOVA and Tukey's test (5%). RESULTS: Shear bond strength values were influenced by the ridge-lap surface treatments only in the microwaved polymer. Sandblasting + monomer swelling and sandblasting + primer swelling interactions yielded lower strengths for microwaved polymer. Only the unmodified surfaces presented a significant difference when the resins were compared, where the microwaved polymer showed a higher value. CONCLUSION: Different tooth ridge-lap surface treatments promoted different strengths of the tooth/resin bond.

Influence of opacifiers on dimensional stability and detail reproduction of maxillofacial silicone elastomer.

BACKGROUND: We evaluated the influence of chemical disinfection and accelerated aging on the dimensional stability and detail reproduction of a silicone elastomer containing one of two opacifiers. METHODS: A total of 90 samples were fabricated from Silastic MDX 4-4210 silicone and divided into groups (n = 10) according to opacifier content (barium sulfate or titanium dioxide) and disinfectant solution (neutral soap, Efferdent, or 4% chlorhexidine). The specimens were disinfected 3 times per week during 60 days and then subjected to accelerated aging for 1008 hours. Dimensional stability and detail reproduction tests were performed after specimens' fabrication (baseline), chemical disinfection and periodically during accelerated aging (252, 504, and 1008 hours). The results were analyzed using 3-way repeated-measures ANOVA and the Tukey HSD test (α = 0.05). RESULTS: All groups exhibited dimensional changes over time. The opacifier (p = .314), period (p < .0001) and their interactions (p = .0041) affected the dimensional stability of the silicone. Statistical significant dimensional differences occurred between groups with (0.071) and without opacifiers (0.053). Accelerated aging influenced the dimensional stability of the samples. All groups scored 2 in the detail reproduction tests, which represents the fully reproducing of three test grooves with accurate angles. CONCLUSIONS: Incorporation of opacifiers alters the dimensional stability of silicones used in facial prosthetics, but seems to have no influence on detail reproduction. Accelerated aging is responsible for most of the dimensional changes in Silastic MDX4 4210, but all dimensional changes measured in this study remained within the limits of stability necessary for this application.

Luting glass ceramic restorations using a self-adhesive resin cement under different dentin conditions.

OBJECTIVES: The aim of this study was to investigate the bond strength of ceramic restorations luted using a self-adhesive resin cement (RelyX Unicem, 3M ESPE) under different dentin conditions. MATERIAL AND METHODS: In the experimental groups, ceramic restorations were luted to bovine incisors with RelyX Unicem under the following conditions: [Dry dentin]: surface was dried using air stream for 15 s; [Moist dentin]: excess dentin moisture was removed with absorbent paper; [Bonding agent]: Clearfil SE Bond (Kuraray) self-etching adhesive system was previously applied to dentin. In the Control group, cementation was done using an etch-and-rinse adhesive (Excite DSC) and Variolink II resin cement (Ivoclar Vivadent). Photoactivation of the resin cements was performed with UltraLume LED 5 unit (Ultradent). The restorations (n=5 per group) were sectioned into beams and microtensile testing was carried out. Data were subjected to ANOVA and Tukey's test (p<0.05). Failure modes were classified under Scanning Electron Microscopic (SEM) (x120 magnification). RESULTS: The bond strength was dependent on the moisture status of the dentin. Bond strength in the "dry dentin group" was significantly lower than that of all other groups, which showed similar results. A predominance of mixed failures was detected for the control group, while a predominance of adhesive failures was observed for the "bonding agent" and "dry dentin" groups. The "moist dentin" group presented predominantly cohesive failures within the luting material. The previous application of a self-etching adhesive showed no significant effect. CONCLUSIONS: Only excess dentin moisture should be removed for the cementation of ceramic restorations with self-adhesive resin cements.