Retention of Provisional Intraradicular Retainers Using Fiberglass Pins.

OBJECTIVES: The purpose of this study was to compare the retention properties between fiberglass pins with chemically activated acrylic resin and metallic intraradicular retainers often used for the purpose of temporary prosthetic retention. MATERIALS AND METHODS: Two mechanical tests, pushout and traction, were performed on specimens distributed in three groups (n = 10) for each test; two metal pins G1: Metalpin Ângelus and G2: Provisional Pivot Jon in addition to one fiberglass pin G3: Whitepost DC-E, FGM. One-way analysis of variance (ANOVA) followed by Tukey's post hoc test was used at the level of significance α = 0.05. RESULTS: The fiberglass pins (G3) showed higher values in the traction test than the metal pins (G1 and G2) with a statistically significant difference (P < 0.05); however, they performed similarly to the metal pin groups in the pushout test (P > 0.05). They also presented a lower occurrence of failure in the relining acrylic resin. CONCLUSION: The study pointed out the use of fiberglass pins as suitable alternatives for provisional intracanal metallic retainers.

Effect of shear bond strength of metallic orthodontic brackets bonded with and without dental adhesive / Efeito da resistência ao cisalhamento de braquetes ortodônticos unidos com e sem adesivo dentário

Objective: The aim of this study was to evaluate the shear bond strength (SBS) of two materials for bonding orthodontic brackets on dental enamel before and after thermocycling. Material and Methods: Forty bovine incisors were divided into four groups (n=10). All teeth were etched with 35% phosphoric acid (3M Espe). For bonding of the brackets, G1 and G2 received orthodontic composite resin (Fill Magic Ortodôntico) and G3 and G4, an adhesive (ScotchBond) was used before the orthodontic resin Transbond XT (3M Unitek). G1 and G3 were kept at 37ºC for 24h and G2 and G4 were submitted to thermocycling (5000 cycles, at 5ºC - 55ºC) prior to SBS testing, performed by a universal machine (EMIC) at 1 mm/min, with a 50kgf load cell. Results were analyzed with two-way ANOVA, followed by Tukey's test (p=0.05). Adhesive surfaces were evaluated through stereomicroscopy and classified according to the type of failure presented. Results: Surface treatment with dental adhesive presented higher SBS values, regardless thermocycling (G3: 12.01 MPa; G4: 12.36 MPa) and the lowest values occurred in G2 (8.89 MPa). For groups without adhesive and with thermocycling, a higher number of completely adhesive failures between composite and enamel were present. For groups in which dental adhesive was used, regardless thermocycling, the failures were mainly adhesive between composite and the bracket. Conclusion: Surface etching of enamel with 35% phosphoric acid with or without adhesive showed a positive effect on SBS. The application of adhesive on enamel surface contributed to the maintenance of SBS values after thermocycling (AU)

Objetivo: O objetivo desse estudo foi avaliar a resistência ao cisalhamento de dois materiais para fixação de braquetes ortodônticos ao esmalte dentário antes e após a termociclagem. Material e Métodos: Quarenta incisivos bovinos foram divididos em quatro grupos (n=10). Todos os dentes foram condicionados com ácido fosfórico a 35% (3M Espe). Para a fixação dos braquetes, G1 e G2 receberam a resina composta ortodôntica (Fill Magic Ortodôntico) e G3 e G4, um adesivo dentário (ScotchBond) foi usado antes da resina ortodôntica Transbond XT (3M Unitek). G1 e G3 foram mantidos a 37ºC por 24h e G2 e G4 foram submetidos à ciclagem térmica (5000 ciclos, de 5ºC - 55ºC) anterior ao teste de resistência ao cisalhamento, realizado por máquina universal (EMIC) a 1 mm/min, com célula de carga de 50kgf. Os resultados foram analisados com ANOVA 2-fatores, seguida do teste de Tukey (p=0,05). As superfícies adesivas foram avaliadas através de estereomicroscopia e classificadas de acordo com o tipo de falha presente. Resultados: O tratamento de superfície com adesivo dentário apresentou maiores valores de resistência ao cisalhamento, independente da termociclagem (G3: 12,01 MPa; G4: 12,36 MPa) e os menores valores ocorreram para G2 (8,89 MPa). Para os grupos sem adesivo e com termociclagem, o maior número de falhas predominantemente adesivas entre resina composta e esmalte estava presente. Para os grupos em que o adesivo dentário foi utilizado, independente da termociclagem, as falhas foram principalmente adesivas entre resina composta e o braquete. Conclusão: O condicionamento superficial do esmalte com ácido fosfórico a 35% com ou sem adesivo mostrou um efeito positivo sobre a resistência ao cisalhamento. A aplicação de adesivo na superfície do esmalte contribuiu para a manutenção dos valores de resistência ao cisalhamento após a termociclagem. (AU)

Reação do complexo dentinopulpar aos cimentos utilizados na odontologia restauradora: Revisão de literatura / Dentin-pulp complex reaction to the cements used in the restorative dentistry: review of literature

Esta revisão de literatura abordou a reação do complexo dentinopulpar aos cimentos utilizados na odontologia restauradora. Utilizou-se as bases de dados Pubmed, Scielo e Bireme. Os cimentos podem ser tóxicos às células pulpares: o cimento de fosfato de zinco é irritante, porém o seu efeito tóxico diminui com o tempo; para o cimento de óxido de zinco e eugenol, quanto maior a liberação do eugenol, maior a sua citotoxicidade; em cavidades rasas e médias, os cimentos de policarboxilato de zinco e de ionômero de vidro anidro são biocompatíveis. A liberação dos monômeros resinosos confere uma citotoxicidade aos cimentos de ionômero de vidro modificado por resina composta e resinoso; o cimento de hidróxido de cálcio permite a formação de dentina terciária e deve ser aplicado em cavidades profundas antes de qualquer outro material. Concluiu-se que as substâncias químicas dos cimentos utilizados na odontologia restauradora podem ser altamente tóxicas às células pulpares, além disto, a polpa dental possui mecanismos reparadores que controlam a severidade e as consequências da resposta inflamatória; os cimentos devem interagir com o CDP evitando as injúrias e reparando as já sofridas e tal interação é influenciada pelas suas composições químicas, pelos seus componentes absorvidos e degradados, além da maneira que este complexo responde a eles.

Properties of dental resins submitted to pH catalysed hydrolysis.

OBJECTIVES: This study evaluated the surface microhardness (SM) and roughness (SR) alterations of dental resins submitted to pH catalysed degradation regimens. METHODS: Thirty discs of each TPH Spectrum (Dentsply), Z100 (3M-ESPE), or an unfilled experimental bis-GMA/TEGDMA resin were fabricated, totaling 90 specimens. Each specimen was polymerized for 40 s, finished, polished, and individually stored in deionized water at 37 °C for 7 days. Specimens were randomly assigned to the following pH solutions: 1.0, 6.9 or 13, and for SM or SR evaluations (n = 5). Baseline Knoop-hardness of each specimen was obtained by the arithmetic mean of five random micro-indentations. For SR, mean baseline values were obtained by five random surface tracings (R(a)). Specimens were then soaked in one of the following storage media at 37 °C: (1) 0.1 M, pH 1.0 HCl, (2) 0.1 N, pH 13.0 NaOCl, and (3) deionized water (pH 6.9). Solutions were replaced daily. Repeated SM and SR measurements were performed at the 3-, 7- and 14-day storage time intervals. For each test and resin, data were analysed by two-way ANOVA followed by Tukey's test (α = 0.05). RESULTS: There was significant decrease in SM and increase in SR values of composites after storage in alkaline medium. TPH and Z100 presented similar behaviour for SM and SR after immersion in the different media, whereas unfilled resin values showed no significant change. CONCLUSION: Hydrolytic degradation of resin composites seems to begin with the silanized inorganic particles and therefore depend on their composition. SIGNIFICANCE: To accelerate composite hydrolysis and produce quick in vitro microstructural damage, alkaline medium appears to be more suitable than acidic medium. Contemporary resin composite properties seem to withstand neutral and acidic oral environments tolerably well.

Water sorption of CH3- and CF3-Bis-GMA based resins with additives.

OBJECTIVES: To evaluate the effect of additives on the water sorption characteristics of Bis-GMA based copolymers and composites containing TEGDMA, CH3Bis-GMA or CF3Bis-GMA. MATERIAL AND METHODS: Fifteen experimental copolymers and corresponding composites were prepared combining Bis-GMA and TEGDMA, CH3Bis-GMA or CF3Bis-GMA, with aldehyde or diketone (24 and 32 mol%) totaling 30 groups. For composites, barium aluminosilicate glass and pyrogenic silica was added to comonomer mixtures. Photopolymerization was effected by 0.2 wt% each of camphorquinone and N,N-dimethyl-p-toluidine. Specimen densities in dry and water saturated conditions were obtained by Archimedes' method. Water sorption and desorption were evaluated in a desorption-sorption-desorption cycle. Water uptake (%WU), water desorption (%WD), equilibrium solubility (ES; µg/mm³), swelling (f) and volume increase (%V) were calculated using appropriate equations. RESULTS: All resins with additives had increased %WU and ES. TEGDMA-containing systems presented higher %WU, %WD, ES, f and %V values, followed by resins based on CH3Bis-GMA and CF3Bis-GMA. CONCLUSIONS: Aldehyde and diketone led to increases in the water sorption characteristics of experimental resins.

Water sorption of CH3- and CF3-Bis-GMA based resins with additives

OBJECTIVES: To evaluate the effect of additives on the water sorption characteristics of Bis-GMA based copolymers and composites containing TEGDMA, CH3Bis-GMA or CF3Bis-GMA. MATERIAL AND METHODS: Fifteen experimental copolymers and corresponding composites were prepared combining Bis-GMA and TEGDMA, CH3Bis-GMA or CF3Bis-GMA, with aldehyde or diketone (24 and 32 mol%) totaling 30 groups. For composites, barium aluminosilicate glass and pyrogenic silica was added to comonomer mixtures. Photopolymerization was effected by 0.2 wt% each of camphorquinone and N,N-dimethyl-p-toluidine. Specimen densities in dry and water saturated conditions were obtained by Archimedes' method. Water sorption and desorption were evaluated in a desorption-sorption-desorption cycle. Water uptake (%WU), water desorption (%WD), equilibrium solubility (ES; µg/mm³), swelling (f) and volume increase (%V) were calculated using appropriate equations. RESULTS: All resins with additives had increased %WU and ES. TEGDMA-containing systems presented higher %WU, %WD, ES, f and %V values, followed by resins based on CH3Bis-GMA and CF3Bis-GMA. CONCLUSIONS: Aldehyde and diketone led to increases in the water sorption characteristics of experimental resins.

Mechanical properties and characteristics of developmental copolymers incorporating catechin or chlorhexidine.

OBJECTIVES: This study evaluated catechin and chlorhexidine release from copolymers based on bis-GMA diluted with TEGDMA (R1), propoxylated bis-GMA-CH(3)bis-GMA (R2) or fluorinated bis-GMA-CF(3)bis-GMA (R3). Mechanical properties, degree of conversion, water sorption and solubility were also tested. METHODS: Experimental comonomers (R1, R2, R3) were prepared combining bis-GMA with the diluents (70/30 mol%). Each comonomer had either catechin or chlorhexidine incorporated in the following ratios: 0, 0.2, 1.0, 2.0 wt%. The degree of conversion (%DC) of resins was evaluated by FT-IR spectrophotometry (n=3). Flexural strength and elastic modulus were tested on a universal testing machine at a crosshead speed of 0.5mm/min (n=6). Resin disks (7 mm in diameter × 2 mm high) were immersed in deionized water and mass changes recorded daily. Spectral measurements were made to follow any changes in optical densities of deionized water in order to examine catechin and chlorhexidine release rates (n=6). After a 28-day period, water sorption and solubility were calculated using appropriate equations (n=6). Data within the tests were evaluated by one- and three-way ANOVA and Tukey-Kramer's test (α=0.05). RESULTS: Except for R1 with 2.0% drug none of the groups had changes in degree of conversion and water sorption. Solubility increased with increased drug ratios. Changes in flexural strength and elastic modulus were shown to be variable and material-dependent. All resins presented a ∼24 h burst of drug release. Release rates were drug-ratio dependent and significantly higher for chlorhexidine than for catechin. SIGNIFICANCE: Monomer type, %DC, drug ratio and type lead to different interactions between resins and chlorhexidine/catechin drug particles. It should be possible to develop different resins based on clinical needs.

The role of surface sealants in the roughness of composites after a simulated toothbrushing test.

OBJECTIVES: To evaluate the influence of two surface sealants (BisCover/Single Bond) and three application techniques (unsealed/conventional/co-polymerization) on the roughness of two composites (Filtek Z250/Z350) after the toothbrushing test. METHODS: Seventy-two rectangular specimens (5 mm x10 mm x 3 mm) were fabricated and assigned into 12 groups (n=6). Each sample was subjected to three random roughness readings at baseline, after 100,000 (intermediate), and 200,000 (final) toothbrushing strokes. Roughness (R) at each stage was obtained by the arithmetic mean of the reading of each specimen. Sealant removal was qualitatively examined (optical microscope) and classified into scores (0-3). Data were analyzed by Student's paired t-test, two-way ANOVA/Tukey's test, and by Wilcoxon, Kruskal-Wallis and Miller's test (alpha=0.05). RESULTS: Z250 groups at baseline did not differ statistically from each other. Unsealed Z350 at baseline had lower R values. All the unsealed groups presented gradual decrease in R from baseline to final brushing. From baseline to the intermediate stage, Z250 co-polymerized groups presented a significant reduction in R (score 3). Conventionally sealed groups had no significant changes in R (scores 2-0.8). From baseline to the intermediate stage, the conventionally sealed Z350 Single Bond group had an increase in R (score 1.5). In the final stage, all the conventionally sealed groups presented a reduction in R (scores 0.7-0). Co-polymerized Single Bond groups had a significant reduction in R (scores 2.5-2.7), and co-polymerized BisCover groups an increase in R (scores 2.8-3). CONCLUSIONS: At any brushing stage, sealed composites presented superior performance when compared with unsealed composites.

Influence of glutaraldehyde priming on bond strength of an experimental adhesive system applied to wet and dry dentine.

OBJECTIVES: This study tested the following null hypotheses: (1) there is no difference in resin-dentine bond strength when an experimental glutaraldehyde primer solution is added prior to bonding procedures and (2) there is no difference in resin-dentine bond strength when experimental glutaraldehyde/adhesive system is applied under dry or wet demineralized dentine conditions. METHODS: Extracted human maxillary third molars were selected. Flat, mid-coronal dentine was exposed for bonding and four groups were formed. Two groups were designated for the dry and two for the wet dentine technique: DRY: (1) Group GD: acid etching+glutaraldehyde primer (primer A)+HEMA/ethanol primer (primer B)-under dried dentine+unfilled resin; (2) Group D: the same as GD, except for primer A application; WET: (3) Group GW: the same as GD, but primer B was applied under wet dentine condition; (4) Group W: the same as GW, except for primer A application. The bonding resin was light-cured and a resin core was built up on the adhesive layer. Teeth were then prepared for microtensile bond testing to evaluate bond strength. The data obtained were submitted to ANOVA and Tukey's test (alpha=0.05). RESULTS: Glutaraldehyde primer application significantly improved resin-dentine bond strength. No significant difference was observed when the same experimental adhesive system was applied under either dry or wet dentine conditions. These results allow the first null hypothesis to be rejected and the second to be accepted. CONCLUSION: Glutaraldehyde may affect demineralized dentine properties leading to improved resin bonding to wet and dry substrates.

In vitro wear, surface roughness and hardness of propanal-containing and diacetyl-containing novel composites and copolymers based on bis-GMA analogs.

OBJECTIVE: To evaluate the effect of two additives, aldehyde or diketone, on the wear, roughness and hardness of bis-GMA-based composites/copolymers containing TEGDMA, propoxylated bis-GMA (CH(3)bis-GMA) or propoxylated fluorinated bis-GMA (CF(3)bis-GMA). METHODS: Fifteen experimental composites and 15 corresponding copolymers were prepared combining bis-GMA and TEGDMA, CH(3)bis-GMA or CF(3)bis-GMA, with aldehyde (24 mol% and 32 mol%) or diketone (24 mol% and 32 mol%) totaling 30 groups. For composites, hybrid treated filler (barium aluminosilicate glass/pyrogenic silica; 60 wt%) was added to monomer mixtures. Photopolymerization was affected by 0.2 wt% each of camphorquinone and N,N-dimethyl-p-toluidine. Wear (W) test was conducted in a toothbrushing abrasion machine (n=6) and quantified using a profilometer. Surface roughness (R) changes, before and after abrasion test, were determined using a rugosimeter. Microhardness (H) measurements were performed for dry and wet samples using a Knoop microindenter (n=6). Data were analyzed by one-way ANOVA and Tukey's test (alpha=0.05). RESULTS: Incorporation of additives led to improved W and H values for bis-GMA/TEGDMA and bis-GMA/CH(3)bis-GMA systems. Additives had no significant effect on the W and H changes of bis-GMA/CF(3)bis-GMA. With regard to R changes, additives produced decreased values for bis-GMA/CH(3)bis-GMA and bis-GMA/CF(3)bis-GMA composites. Bis-GMA/TEGDMA and bis-GMA/CH(3)bis-GMA copolymers with additives became smoother after abrasion test. SIGNIFICANCE: The findings correlate with additives ability to improve degree of conversion of some composites/copolymers thereby enhancing mechanical properties.

Effect of toothbrushing abrasion on weight and surface roughness of pH-cycled resin cements and indirect restorative materials.

OBJECTIVE: To evaluate wear resistance, by weight loss and roughness changes, of resin cements and indirect restorative materials to toothbrushing and toothbrushing associated with pH-challenge simulation. METHOD AND MATERIALS: The following materials were studied: Enforce resin cement (Dentsply), Rely X resin cement (3M ESPE), Variolink II resin cement (Ivoclar/Vivadent), Artglass indirect resin composite (Heraeus Kulzer), and Duceram Plus porcelain (Degussa). Twenty cylindrical specimens were prepared for each material for a total of 10 groups (n = 10). After finishing and polishing, the specimens were subjected to toothbrushing. One group of each material was pH cycled before abrasion. For toothbrushing, a machine containing soft-bristle tips, dentifrice, and water was used. One hundred thousand brushing cycles were performed. Weight loss was determined as the percentage difference between initial (before brushing) and final (after brushing) measurements. Roughness changes were evaluated by the difference between initial and final measurements. Data were analyzed with the paired t test, 2-way ANOVA, and Tukey test (alpha = 0.05). RESULTS: Paired t test showed significant differences in weight loss and roughness after toothbrushing (P <.01). Statistically significant differences were found among materials for both weight loss, which ranged from 0.34% (Duceram Plus) to 1.85% (Enforce/pH), and roughness changes, which ranged from -0.03 microm (Duceram Plus) to 0.29 microm (Rely X/pH). CONCLUSIONS: Among cements, Variolink II exhibited the least weight loss and roughness increase. Of all materials, Duceram Plus porcelain presented the lowest weight loss and became smoother after abrasion. pH cycling had no influence on material weight or roughness changes after abrasion.

Effect of resin luting film thickness on fracture resistance of a ceramic cemented to dentin.

PURPOSE: The aim of this study was to evaluate the fracture resistance of ceramic plates cemented to dentin as a function of the resin cement film thickness. MATERIALS AND METHODS: Ceramic plates (1 and 2 mm thicknesses) were cemented to bovine dentin using resin composite cement. The film thicknesses used were approximately 100, 200, and 300 microm. Noncemented ceramic plates were used as control. Fracture loads (N) were obtained by compressing a steel indenter in the center of the ceramic plates. ANOVA and Tukey tests (alpha= 0.05) were used for each ceramic thickness to compare fracture loads among resin cement films used. RESULTS: Mean fracture load (N) for 1-mm ceramic plates were: control-26 (7); 100 microm-743 (150); 200 microm-865 (105); 300 microm-982 (226). Test groups were significantly different from the control group; there was a statistical difference in fracture load between groups with 100 and 300 microm film thicknesses ( p < 0.01). Mean fracture load for 2-mm ceramic plates were: control-214 (111); 100 microm-1096 (341); 200 microm-1067 (226); 300 microm-1351 (269). Tested groups were also significantly different from the control group ( p < 0.01). No statistical difference was shown among different film thicknesses. CONCLUSIONS: Unluted specimens presented significantly lower fracture resistance than luted specimens. Higher cement film thickness resulted in increased fracture resistance for the 1-mm ceramic plates. Film thickness did not influence the fracture resistance of 2-mm porcelain plates.

Contribuição do glutaraldeído como componente de sistemas adesivos dentinários / Influence of glutaraldehyde priming on bond strengths of an experimental adhesive system applied to wet and dry dentin

Neste trabalho foram testadas as seguintes hipóteses nulas: 1) Não há diferença entre os valores de resistência de união entre resina restauradora e dentina quando uma solução aquosa de glutaraldeído é aplicada como primer dentinário antes do emprego do agente adesivo; 2) Não há diferença entre os valores de resistência de união, quando a aplicação do mesmo sistema adesivo se dá em condições de dentina úmida ou seca. Dentes humanos foram selecionados, e tiveram sua porção oclusal desgastada, expondo a parte média da dentina coronária para adesão. Quatro grupos foram formados, variando-se a aplicação ou não do primer de glutaraldeído e a condição de umidade dentinária: úmida ou seca. Após aplicação e fotopolimerização do sistema adesivo experimental, foram confeccionados blocos resina composta de 4mm de altura sobre a superfície oclusal e os dentes foram preparados para o teste de microtração para a avaliação da resistência de união. Os resultados obtidos foram submetidos à análise de variância a um critério e teste de Tukey ('alfa'=0,05). A aplicação do primer de glutaraldeído aumentou significativamente os resultados de resistência de união. Não houve diferença estatística entre o mesmo sistema experimental se aplicado em dentina seca ou úmida. A hipótese 1 não se confirma e aceita-se a hipótese 2.

This work tested the following null hypothesis: 1) There is no difference between resin-dentin bond strengths when a glutaraldehyde primer solution is applied onto demineralized dentin during adhesive bonding. 2) There is no difference between resin-dentin bond strengths when the same experimental adhesives systems are applied whether in dry or wet demineralized dentin conditions. Human, extracted upper third molars were selected. The oclusal surfaces were ground flat, and midcoronal dentin was exposed for bonding. Four groups of six teeth were formed. Two groups were designated for dry dentin technique and two for the wet one. After application and photopolymerization of the bonding system, a 4 mm-high resin core build-up was fabricated over the adhesive layer. Specimens were then prepared for microtensile bond test for bond strengths evaluation. The obtained data were submitted to ANOVA and Tukey test ('alfa'=0.05). Glutaraldehyde primer application significantly improved resin-dentin bond strength. No significant difference was observed when the same experimental adhesive system was applied whether in dry or wet dentin conditions. Such results require to reject the first null hypothesis and accept the second one.

Assessing the tooth-restoration interface wear resistance of two cementation techniques: effect of a surface sealant.

This study compared (1) the tooth-restoration interface width of conventional and "resin coating" cementation techniques, (2) the toothbrushing wear resistance of the two interfaces and (3) this study evaluated the influence of a restoration surface sealing on toothbrush wear resistance on both cementation technique interfaces. Mid-coronal buccal surfaces of 40 bovine teeth were ground to obtain a flat enamel surface. For each specimen, a 3 mm x 4 mm x 3 mm dimension rectangular cavity was prepared. The teeth were divided into four groups. Two groups (RC) received a "resin coating" (ED Primer + Tetric Flow) prior to cementation. The remaining two groups (NC) served as non-coated groups. All teeth were restored with composite inlays (Z250) fabricated by the indirect method and were cemented with dual cure resin cement (Panavia F). After finishing the margins, one group from each of the cementation techniques (RC+S and NC+S) had the tooth-restoration interface protected with a restoration surface sealant (Biscover). The specimens were subjected to 100,000 brushing abrasion cycles. The tooth-restoration width was obtained using a Hommel Tester T 1000-basic profilometer and Turbo Datawin NT 1.34 Software (microm). The interface wear (vertical loss/microm and area/microm2) was calculated with Image Tool 3.0 Software. Data were analyzed with Student t-test, one-way analysis of variance and Tukey test (alpha=0.05). Mean interface width for the NC group was 67 microm and 72 microm for the RC group. The student t-test showed no significant differences between groups (p=0.53). ANOVA showed significant differences (p<0.01) in vertical loss among groups (NC: 49.30 microm; NC+S: 7.90 microm; RC: 27.15 microm; RC+S: 4.74 microm). Also, ANOVA showed significant differences (p<0.01) in worn areas among groups (NC: 2,008 microm2; NC+S: 128 microm2; RC: 1,580 microm2 and RC+S: 88 microm2). No differences were found in tooth-restoration interface width and worn area between conventional and "resin coating" techniques. "Resin coating" interface presented reduced vertical loss. Restoration surface sealing provided reduced wear in tooth-restoration interface for both techniques.

Influence of pH environment on polymer based dental material properties.

OBJECTIVE: This study aims to analyze the influence of different pH environments causing degradation to the properties of polymer based materials. DATA AND SOURCES: Studies were identified by searching published material in medical and dental literature using general and specialist databases, hand searching key dental journals and searching abstracts from conference proceedings. STUDY SELECTION: Evaluation of published laboratory studies regarding the effects of different pH mediums on resin-based material properties. CONCLUSION: For laboratory studies, slightly low pH mediums are the ones of choice to best mimic some in vivo conditions, but the effect seems to be slow acting. If the purpose is to accelerate dental composite hydrolysis and produce quick micro-structural damage to evaluate in vitro mechanical performances, suitable alternatives would be the use of high alkaline or very low acidic mediums.

Evaluating a method of artificially hypermineralizing dentin to simulate natural conditions in bonding studies.

PURPOSE: This study tested an in vitro model of dentin hypermineralization, aiming to simulate naturally hypermineralized dentin for bond strength studies. The effect on bond strength of a double-etching treatment on the artificially hypermineralized substrate was also evaluated. MATERIALS AND METHODS: Extracted human third molars were selected and 2 groups were formed: a group of 3 teeth, called N (normal dentin) and a group of 6 teeth, called H (hypermineralized dentin). Occlusal surfaces were ground flat to expose midcoronal dentin. Group H was subjected to artificial hypermineralization and subdivided into 2 subgroups: Ht and Hd. The exposed dentinal surfaces of group N and subgroup Ht were etched with 37% phosphoric acid for 15 s prior to bonding with Single Bond adhesive. Dentin of the subgroup Hd was etched twice (double etching) prior to bonding with Single Bond. A 4-mm-high Z100 composite buildup was created on each tooth and, after 24 h water storage, bond strengths were evaluated by the microtensile method. The data between group N and subgroup Ht and between subgroups Ht and Hd were compared using the Student's t test (alpha = 0.05). RESULTS: No significant difference was observed between bond strengths of group N and subgroup Ht (p = 0.108). Subgroup Hd was statistically different from Ht (p < 0.0001). CONCLUSIONS: Bond strengths of Single Bond to artificially hypermineralized dentin did not differ statistically from those to normal dentin substrate. The double etching approach significantly reduced bond strengths of artificially hypermineralized dentin.

Clinical evaluation of proximal contacts of Class II esthetic direct restorations.

OBJECTIVE: This study evaluated the effectiveness of proximal contacts in Class II restorations using two types of matrix bands (steel and polyester) with two different restoration techniques (incremental and with prepolymerized particles). METHOD AND MATERIALS: Eighty-eight Class II adjacent restorations using Prodigy resin composite were performed: 44 with the incremental technique (22 with steel matrix bands, 22 with polyester matrix bands) and 44 utilizing prepolymerized resin particles (22 steel matrix, 22 polyester matrix). The restorations were clinically evaluated at baseline and at 6, 12, and 18 months. Proximal contacts obtained immediately after restoration procedure in all restorations were satisfactory. RESULTS: No statistically significant alterations were found in 18 months of evaluation. CONCLUSION: Regardless of the utilized resin composite, there were no differences in the amount of proximal contact variations with respect to tested techniques and matrices.

Surface roughness average and scanning electron microscopic observations of resin luting agents / Alteração de rugosidade superficial e observações em microscopia eletrônica de varredura de cimentos resinosos

O objetivo desse estudo foi avaliar a alteração de rugosidade superficial de três cimentos resinosos após submetê-los a ciclos de escovação simulada e analisar qualitativamente a sua superfície através de observações microscópicas. Os materiais empregados neste estudo foram Enforce Sure Cure (Dentsply), Rely X (3M-ESPE) e Variolink II (Vivadent). Estes foram submetidos à ciclos de escovação simulada (100.000 ciclos para cada espécime) e a alteração de sua rugosidade superficial (antes e após escovação) foi avaliada. Para cada material e condição de rugosidade, espécimes foram selecionados, metalizados e observados em microscopia eletrônica de varredura (DSM 900 Zeiss). Baseado nas observações microscópicas e nos valores de alteração de rugosidade, todos os materiais apresentaram aumento de rugosidade aritmética (Ra) após ciclos de escovação simulada porém, não estatisticamente significante.

Utilizaçao de picnômetro a gás para obtenção da contração de polimerização de resinas compostas / Measuring polymerization shrinkage of composites utilizing a gas pycnometer

O objetivo deste estudo foi analisar a contração volumétrica de polimerização de cinco marcas comerciais de resinas compostas. Um picnometro a gás foi empregado para determinar o volume dos espécimes antes e após a sua fotopolimerização, de forma que a contração total foi obtida. A resina composta nao-polimerizada foi inicialmente pesada em uma balança analítica, inserida na câmara de análise do equipamento (cujo volume é conhecido) e hermeticamente fechada. O volume inicial do espécime foi determinado através da alteraçao de pressao do gás hélio, quando este é injetado na câmara e depois liberado para expansao em reservatório de volume também conhecido. Neste estudo, 15 ciclos de pressurização foram realizados para a detemrinação do volume inicial para cada espécime. O valor final foi obtido através da média aritmética dos dados. Fora da câmara, os espécimes foram polimerizados em incrementose novamente pesados. Para a obtenção do volumefinal as mesmas etapas anteriormente descritas foram realizadas. A porcetagem de contração (P) foi calculadaatravés da seguinte fórmula: P = (SVi - SVf, onde SV é o volume específico e os sufixos i e f indicam as medidas iniciais e finais, respectivamente. A porcetagem de contraçao obtida para os materiais analisados variou entre 0,56 porcento e 3,26 porcento. trata-se de uma metodologia promissora, de facíl exacuçao, e seu mecanismo deve ser mais explorado para o estudo do desempenho de materiais odontológicos.

Surface roughness average and scanning electron microscopic observations of resin luting agents.

The objective of this work was to evaluate the surface roughness changes of three current resin cements after tooth brushing simulation, as well as discuss its relation with scanning electron microscopic observations. The materials employed were Enforce Sure Cure (Dentsply), Rely X (3M-ESPE) and Variolink II (Vivadent). They were subjected to brushing abrasion (100,000 strokes for each specimen) and the surface roughness alterations (before and after strokes) were detected. For each roughness test condition, specimens were coated with gold-palladium and observed on a DSM 900 Zeiss scanning electron microscope. Roughness changes values (Ra) were statistically increased after brushing strokes. Based on the microscopic observations and roughness changes analysis, all cements studied became rougher after brushing strokes.