Ultrasonic agitation reduces the time of calcium hydroxide antimicrobial effect and enhances its penetrability.

OBJECTIVES: The objective of the present work was to evaluate the ultrasonic agitation, time and vehicle (propylene glycol or distilled water) on the antimicrobial potential and penetrability of calcium hydroxide pastes on infected dentin by means of Confocal Laser Scanning Microscopy (CLSM) and microbiological culture (MC). MATERIALS AND METHODS: Dentin specimens were infected with Enterococcus faecalis using a new contamination protocol of 5 days. The specimens were divided into eight groups and dressed with the pastes for 7 or 15 days: G1) calcium hydroxide (CH) + propylene glycol (prop)/7 days (d), G2) CH + prop/7d + ultrasonic agitation (U), G3) CH + distilled water (dw)/7d, G4) CH + dw/7d + U, G5) CH + prop/15d, G6) CH + prop/15d + U, G7) CH + dw/15d, G8) CH + dw/15d + U. The ultrasonic activation was made for 1 min in both directions with a plain point insert. After medications removal, the images obtained by CLSM showed the viable (green) and dead (red) bacteria with Live and Dead dye. By the MC, the dentinal wall debris obtained by burs were collected for colony counts. For the penetration test, the Rodamine B dye was added to the CH pastes and analyzed by CLSM. RESULTS: The 7 and 15-days CH + prop+U pastes performed better antimicrobial efficacy, followed by the CH + dw+U/15d paste. CONCLUSIONS: All pastes demonstrated better penetration and antimicrobial activity against E. faecalis when agitated with ultrasound, even in periods of up to seven days. The propylene glycol vehicle showed better results. CLINICAL RELEVANCE: Agitation of the dressing that remains for less time inside the root canal can optimize the decontamination of endodontic treatment.

Effect of ultrasonic activation on dentinal tubule penetration of calcium silicate-based cements.

This study investigated the dentinal tubule penetration of mineral trioxide aggregate (MTA), NeoMTA Plus and Biodentine placed by either manual condensation or ultrasonic activation in simulated open apex model. Standardized divergent open apex models were created using palatal roots of 60 human maxillary molars and divided into six groups according to the used cements and activation methods (n = 10): MTA-manual condensation, MTA-ultrasonic activation, NeoMTA Plus-manual condensation, NeoMTA Plus-ultrasonic activation, Biodentine-manual condensation, Biodentine-ultrasonic activation. For the measurement of penetration, the cements were mixed with 0.1% Rhodamin B and 6-mm apical portions of each root canal were obturated in an orthograde direction. The roots were embedded into acrylic blocks, and 1-mm-thick sections were obtained at 3 mm from the apex. Specimens were mounted onto glass slides and scanned under a confocal laser scanning microscope (CLSM) and stereomicroscope. Dentinal tubule penetration areas, depth and percentage were measured using LSM and ImageJ software. The data were analyzed using two-way analysis of variance (anova) with Bonferroni correction (α = 0.05). No correlation was found between stereomicroscope and CLSM analyses (p > .05). CLSM analysis showed no significant differences between MTA, NeoMTA Plus, and Biodentine groups when manual condensation was used (p > .05). Ultrasonic activation did not increase the tubular penetration of MTA, NeoMTA Plus or Biodentine as compared to manual condensation of each material (p > .05). MTA, NeoMTA Plus and Biodentine showed similar tubular penetration when manual condensation was used. Ultrasonic activation of these cements had no effect on tubular penetration of each material as compared to the manual condensation counterparts.

Responsive antimicrobial dental adhesive based on drug-silica co-assembled particles.

Most dental resin composite restorations are replacements for failing restorations. Degradation of the restoration-tooth margins by cariogenic bacteria results in recurrent caries, a leading cause for restoration failure. Incorporating antimicrobial agents in dental adhesives could reduce interfacial bacterial count and reduce recurrent caries rates, inhibit interfacial degradation, and prolong restoration service life, while minimizing systemic exposure. Direct addition of antimicrobial compounds into restorative materials have limited release periods and could affect the integrity of the material. Attempts to incorporate antimicrobial within mesoporous silica nanoparticles showed theoretical promise due to their physical robustness and large available internal volume, yet yielded short-term burst release and limited therapeutic payload. We have developed novel broad-spectrum antimicrobial drug-silica particles co-assembled for long-term release and high payload incorporated into dental adhesives. The release of the drug, octenidine dihydrochloride, is modulated by the oral degradative environment and mathematically modeled to predict effective service life. Steady-state release kills cariogenic bacteria, preventing biofilm formation over the adhesive surface, with no toxicity. This novel material could extend dental restoration service life and may be applied to other long-term medical device-tissue interfaces for responsive drug release upon bacterial infection. STATEMENT OF SIGNIFICANCE: This study describes a novel dental adhesive that includes a broad-spectrum antimicrobial drug-silica co-assembled particles for long-term antimicrobial effect. The release of the drug, octenidine dihydrochloride, is modulated by the oral degradative environment and mathematically modeled to predict effective release throughout the service life of the restoration. Steady-state drug-release kills caries-forming bacteria, preventing biofilm formation over the adhesive surface, without toxicity. This novel material could extend dental restoration service life and may be applied to other long-term medical device-tissue interfaces for responsive drug release upon bacterial infection. Since recurrent cavities (caries) caused by bacteria are the major reason for dental filling failure, this development represents a significant contribution to the biomaterials field in methodology and material performance.

[An experimental study on a slow-release complex with rifampicin-polylactic-co-glycolic acid-calcium phosphate cement].

OBJECTIVE: To prepare the slow-release complex with rifampicin (RFP)-polylactic-co-glycolic acid (PLGA)-calcium phosphate cement (CPC) (RFP-PLGA-CPC complex), and to study its physical and chemical properties and drug release properties in vitro.
 METHODS: The emulsification-solvent evaporation method was adopted to prepare rifampicin polylactic acid-glycolic acid (RFP-PLGA) slow-release microspheres, which were divided into 3 groups: a calcium phosphate bone cement group (CPC group), a CPC embedded with RFP group (RFP-CPC group), and a PLGA slow-release microspheres carrying RFP and the self-curing CPC group (RFP- PLGA-CPC complex group). The solidification time and porosity of materials were determined. The drug release experiments in vitro were carried out to observe the compressive strength, the change of section morphology before and after drug release. 
 RESULTS: The CPC group showed the shortest solidification time, while the RFP-PLGA-CPC complex group had the longest one. There was statistical difference in the porosity between the CPC group and the RFP-CPC group (P<0.05); Compared to the RFP-PLGA-CPC complex group, the porosity in the CPC group and the RFP-CPC group were significantly changed (both P<0.01). There was significant difference in the compressive strength between the RFP- PLGA-CPC complex group and the CPC group (P<0.01), while there was significant difference in the compressive strength between the RFP-CPC group and the CPC group (3 days: P<0.05; 30 and 60 days: P<0.01). The change of the compressive strength in the CPC was not significant in the whole process of degradation. The sizes of PLGA microspheres were uniform, with the particle size between 100-150 µm. The microspheres were spheres or spheroids, and their surface was smooth without the attached impurities. There was no significant change in the section gap in the CPC group after soaking for 3 to 60 days. The microstructure change in the RFP-CPC group was small, and the cross section was formed by small particles. The pores of section in the RFP-PLGA-CPC complex group increased obviously, and PLGA microspheres gradually disappeared until the 60th day when there were only empty cavities left. The RFP-PLGA-CPC complex group had no obvious drugs sudden release, and the cumulative drug release rate was nearly 95% in the 60 days. The linear fitting was conducted for the drug release behavior of the complex, which was in accordance with zero order kinetics equation F=0.168×t.
 CONCLUSION: The porosity of RFP-PLGA-CPC complex is significantly higher than that of CPC, and it can keep slow release of the effective anti-tuberculosis drugs and maintain a certain mechanical strength for a long time.

Effect of different mixing methods on the bacterial microleakage of calcium-enriched mixture cement.

BACKGROUND: Calcium-enriched mixture (CEM) cement is used in the field of endodontics. It is similar to mineral trioxide aggregate in its main ingredients. The present study investigated the effect of different mixing methods on the bacterial microleakage of CEM cement. METHODS: A total of 55 human single-rooted human permanent teeth were decoronated so that 14-mm-long samples were obtained and obturated with AH26 sealer and gutta-percha using lateral condensation technique. Three millimeters of the root end were cut off and randomly divided into 3 groups of 15 each (3 mixing methods of amalgamator, ultrasonic and conventional) and 2 negative and positive control groups (each containing 5 samples). BHI (brain-heart infusion agar) suspension containing Enterococcus faecalis was used for bacterial leakage assessment. Statistical analysis was carried out using descriptive statistics, Kaplan-Meier survival analysis with censored data and log rank test. Statistical significance was set at P<0.05. RESULTS: The survival means for conventional, amalgamator and ultrasonic methods were 62.13±12.44, 68.87±12.79 and 77.53±12.52 days, respectively. The log rank test showed no significant differences between the groups. CONCLUSIONS: Based on the results of the present study it can be concluded that different mixing methods had no significant effect on the bacterial microleakage of CEM cement.

Effect of aluminum chloride hemostatic agent on microleakage of class V composite resin restorations bonded with all-in-one adhesive

Objectives: Since hemostatic agents can induce changes on enamel and dentin surfaces and influence composite resin adhesion, the aim of the present study was to evaluate the effect of the aluminum chloride hemostatic agent on the gingival margin microleakage of class V (Cl V) composite resin restorations bonded with all-in-one adhesive. Study design: Cl V cavities were prepared on the buccal surfaces of 60 sound bovine permanent incisors. Gingival margins of the cavities were placed 1.5 mm apical to the cemento-enamel junction (CEJ). The teeth were randomly divided into two groups of 30. In group 1, the cavities were restored without the application of a hemostatic agent; in group 2, the cavities were restored after the application of the hemostatic agent. In both groups all-in-one adhesive and Z250 composite resin were used to restore the cavities with the incremental technique. After finishing and polishing, the samples underwent a thermocycling procedure, followed by immersion in 2% basic fuschin solution for 24 hours. The samples were sectioned and gingival microleakage was evaluated under a stereomicroscope. The non-parametric Mann-Whitney U test was used to compare microleakage between the two groups. Statistical significance was defined at P<0.05. Results: A statistically significant difference was observed in microleakage between the two groups (P<0.001). Conclusions: Contamination of Cl V composite resin restorations bonded with all-in-one adhesive with aluminum chloride hemostatic agent significantly increases restoration gingival margin microleakage (AU)

An in vitro comparison of different adhesive strategies on the micropush-out bond strength of a glass fiber post

Objectives: To evaluate in vitro the push-out bond strengths of a glass fiber post adhesively luted with self-etchingresin based and self-adhesive luting cements, as well as modified application procedure of self-adhesive lutingcements in combination with single step self-etch adhesives.Materials and methods: Fifty single-rooted human maxillary central incisor teeth were endodontically treated anddivided into five groups (n=10). Glass fiber posts (RelyX Fiber Post) were cemented with the following materials:group 1: ED Primer II/Panavia F 2.0 (PAN); group 2: RelyX Unicem (RU); group 3: Maxcem (MC); group 4:Adper Prompt L-Pop (PLP)/RelyX Unicem; group 5: Optibond all-in-one (OB)/Maxcem. Bonded specimens werecut (1-mm-thick sections) and push-out tests were performed (crosshead-speed, 0.5 mm/min). Data were analyzedby one-way ANOVA followed by the Tukey-HSD test for post hoc comparisons at á = 0.05.Results: The highest bond strength was recorded for groups 4 and 2, with no statistically significant differencesamong them (p>0.05). Group 4 showed significantly higher bond strength than group 1 (p<0.001), group 3(p<0.0001) and group 5 (p<0.0001). Group 1 showed significantly higher bond strength than the group 3 (p<0.05).No statistically significant differences were observed among group 1 and group 2, group 1 and group 5, group 3and group 5. Group 3 showed significantly lower push-out bond strength than the all other luting strategies exceptfor the group 5.Conclusions: The push-out bond strength values of modified application procedure of self-adhesive luting cements(RU and MC) in combination with single step self-etch dentin adhesives (PLP and OB) did not improve the pushoutbond strength of fiber post when compared with those where the conventional use of self-adhesive cements (AU)

Differential hydrolytic degradation of dentin bonds when lutingcarbon fiber posts to the root canal

Objective: The purpose of the study was to evaluate the effect of water storage, adhesive system and root canalregion on the hydrolytic degradation of dentin bonds to carbon fiber posts.Study design: Fiber posts were bonded to the root canals using different adhesive systems and composites: SB1XT group (Scotchbond 1 XT/RelyX ARC), OBF group (One Up Bond F Plus/Ionotite F), and AB2 group (All Bond2/C&B) After water storage (10 days), all roots were sectioned into 1 mm beams and divided into coronal or apicalgroup. The specimens were stored in water at 22-26 °C temperature for 15 or 60 days and tested for microtensilebond strength at a crosshead speed of 0.9 mm/min after the calculation of the bonding area. Statistical analysis wasperformed with ANOVA followed by Tukey test to detect differences between groups (α=0.05). SEM investigationwas performed to determine the mode of fracture.Results: Bond strength at coronal and apical half showed significant differences between experimental groupsboth after 15 and 60 days of water storage. Premature failures were observed in 16-20% of specimens beforestorage in water.Conclusions: For the bonding systems tested, clinicians should consider that bond strength inside the root canal atapical half is lower than at coronal half irrespective of the adhesive system. The adhesion within the root canal ispossible for SB1 XT and OBF groups unlike the AB2 group where adhesion to root canal dentine is not reliable.Nevertheless, apical half represents the worst scenario in which is possible to obtain a durable adhesion (AU)

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Assessment of the penetration depth of dental adhesives through deproteinized acid-etched dentin using neodymium:yttrium-aluminum-garnet laser and sodium hypochlorite.

The objective of this study was to assess the penetration depth of dental adhesive systems through acid-etched dentin, deproteinized by neodymium:yttrium-aluminum-garnet (Nd:YAG) laser or 10% sodium hypochlorite (NaOCl) solution, using fluorescent light microscopy. Sixty extracted human upper premolars were selected to be given standardized buccal and lingual class V cavities. The teeth were randomly divided into two groups, each one consisting of 30 teeth and each group subdivided into three subgroups, each having ten teeth (20 cavities): group 1, Excite bonding system, which was subdivided into group 1a, acid etch/Nd:YAG laser plus Excite bond, group 1b, acid etch/10%NaOCl plus Excite bond, and group 1c, acid etch plus Excite bond; group 2, Solobond Plus bonding system, which was subdivided into group 2a, acid etch/Nd:YAG laser plus Solobond Plus bond, group 2b, acid etch/10%NaOCl plus Solobond Plus bond, and group 2c, acid etch plus Solobond Plus bond. The teeth were prepared for fluorescent light microscopy (FLM) analysis, and the results showed that treatment of the acid-etched dentin with Nd:YAG laser had led to a significant increase in the penetration depth of the adhesive bonding system, and that the maximum penetration depth of the adhesive bonding system through acid-etched, Nd:YAG-lased dentin was significantly more than that of acid-etched, 10% NaOCl-treated dentin. The Solobond Plus bonding system showed maximum penetration depth, more than that of the Excite bonding system.

Zinc polycarboxylate dental cement for the controlled release of an active organic substance: proof of concept.

The potential of employing zinc polycarboxylate dental cement as a controlled release material has been studied. Benzalkonium chloride was used as the active ingredient, and incorporated at concentrations of 1, 2 and 3% by mass within the cement. At these levels, there was no observable effect on the speed of setting. Release was followed using an ion-selective electrode to determine changes in chloride ion concentration with time. This technique showed that the additive was released when the cured cement was placed in water, with release occurring by a diffusion mechanism for the first 3 h, but continuing beyond that for up to 1 week. Diffusion coefficients were in the range 5.62 x 10(-6) cm(2) s(-1) (for 1% concentration) to 10.90 x 10(-6) cm(2) s(-1) (for 3% concentration). Up to 3% of the total loading of benzalkonium chloride was released from the zinc polycarboxylate after a week, which is similar to that found in previous studies with glass-ionomer cement. It is concluded that zinc polycarboxylate cement is capable of acting as a useful material for the controlled release of active organic compounds.

Comparative assessment of the flow rate of root canal sealers / Estudo comparativo do escoamento de cimentos obturadores endodônticos

Purpose: This study evaluated the flow rate of the Acroseal, AH Plus, Endomethasone N, Sealapex, and ActiV GP according to the standards of the ISO specification 6876/2001. Methods: A volume of 0.05 mL of the cement mixed according to the manufacturer's recommendations was placed on a glass plate. At 180±5 s after the commencement of mixing, the second glass plate was placed on top of the sealer, followed by the weight of mass approximately 100 g to make a total mass on the plate of 120±2 g. Ten min after the start of mixing, the weight was removed and the value of the diameter of the compressed disc of sealer was measured. The mean of three such determinations for each sealer was taken as the flow of the material. The mean values were compared using ANOVA and Tukey's tests. Results: The results obtained were: Acroseal 21.24 mm, AH Plus 22.72 mm, ActiV GP 24.90 mm, Endomethasone N 18.76 mm, and Sealapex 25.15 mm. Conclusion: Only the Endomethasone N did not conform to ISO Specification that requires that a sealer shall have a diameter of not less than 20 mm. The Sealapex achieved the greatest flow, but it did not differ from Activ GP and AH Plus (P>0.5).

Objetivo: Este estudo avaliou o escoamento do Acroseal, AH Plus, Endomethasone N, Sealapex e ActiV GP de acordo com a especificação ISO 6876/2001. Metodologia: Um volume de 0,05 mL do cimento manipulado de acordo com as recomendações do fabricante foi colocado numa placa de vidro. Aos 180±5 s após o início da espatulação, uma segunda placa de vidro foi colocada sobre o cimento, seguida por um peso de massa de 100 g para fazer um total de 120±2 g. Dez minutos após o começo da manipulação o peso foi removido e o valor do diâmetro do disco de cimento foi mensurado. A média de 3 mensurações para cada cimento foi tomada como o escoamento do material. Os dados foram comparados estatisticamente pelos testes ANOVA e Tukey. Resultados: Os escoamentos obtidos foram: Acroseal 21.,4 mm, AH Plus 22,72 mm, ActiV GP 24,90 mm, Endomethasone N 18,76 mm e Sealapex 25,15 mm. Conclusão: Apenas o Endomethasone N não se enquadrou na especificação ISO a qual requer que o cimento tenha um diâmetro não inferior a 20 mm. O Sealapex alcançou o melhor escoamento, mas não foi estatisticamente diferente do Activ GP e AH Plus (P>0,05).

Comportamiento del tejido osteomedular de ratones después de la implantación de mineral trióxido agregado o cemento a base de pasta zinquenólica / Marrow bone reaction of rats after implantation of mineral trioxide aggregate or a zinc-oxide eugenol sealer

El objetivo de este estudio fue evualar las respuestas del tejido osteomedular de ratones a través de la colocación de tubos provistos de mineral trióxido agregado o cemento a base de pasta zinquenólica con adición de agentes radiopacificadores (yodoformo o subnitrato de bismuto) con y sin hidróxido de cálcio. Transcurridos 30, 60 Y 90 días de la implantación, el análisis microscópico y estadístico de los especímenes con los testes Kruskall Wallis y Mann Whitney revelaron que la inflamacion fue más exacerbada en los grupos que presentaban oxido de zinc y eugenol, pero disminuyó con el correr del tiempo, llegando a igualarse a los 60 días, con la inflamación referente al trióxido mineral agregado (MTA) (ps 0,05). Solamente los grupos de MTA y control presentaron neoformación ósea en contacto (ps 0,05). Basandonos en estas observaciones, se puede afirmar que el reparo intraóseo en presencia de MTA es mas rapido que el observado con el o óxido de zinc y eugenol

The marrow bone reaction to mineral trioxide aggregate or a potential zinc-oxide eugenol sealer, added up of radiopaque substances and calcium hydroxide, were studied with using an intraosseous implant technique. The tubes containing the distinct materials were introduced surgically into rat and femur tibias. Control tubes were left empty. After 30, 60 and 90 days, the specimens were histologically processed and microscopically evaluated. The statistical analysis revealed that the MT A cement samples displayed no inflammatory response and direct bone apposition after 30 days, while the response of zincoxide based sealer was characterized by granulation tissue regression and mineralized barrier up to 60 days IpsO.05). Based on these results, repair seems to occur in advance when mineral trioxide aggregate is used

Behaviour of an injectable calcium phosphate cement with added tetracycline.

A calcium phosphate cement containing an antibiotic can be used for filling bone defects and to ensure local antibiotherapy. A calcium phosphate cement (already marketed under the name of Cementek can become injectable thanks to the addition of silicone. For dental applications, the behaviour of this injectable cement with added tetracycline was investigated. The tetracycline hydrochloride does not allow maturation of the cement: the tetracycline has to be treated with a calcium sulphate solution. The treated tetracycline (TTC) allowed maturation of the cement towards hydroxyapatite. But the setting time was longer and the mechanical properties decreased. Study in a continuous flow cell showed that the tetracycline is released in a continuous manner: thus, after 6 days, 60% of the antibiotic was released into the surrounding medium.

[Release of fluoride ions into saliva from some dental materials]. / Uwalnianie jonów fluorkowych do sliny z wybranych materialów stomatologicznych.

The aim of the study was to evaluate fluoride release from dental materials: resin composites--Tetric Ceram and Degufill Mineral, fissure sealants--Conseal F and Admira seal, compomer--Freedom and glass-ionomer cement--Vitremer. Release to the patient's unstimulated mixed saliva was studied after treatment with the material. The study group comprised 72 patients and fluoride concentrations were measured with an ion-selective electrode (Orion). The following release of fluoride in decreasing order was found: Vitremer (6.03 microM), Degufill Mineral (2.79 microM), Teric Ceram (2.54 microM), Freedom (2.52 microM), Admira seal (1.85 microM) and Conseal F (1.80 microM).

Estudo químico comparativo de cimentos endodônticos quanto a presença de hidróxido de cálcio: velocidade de dissoluçäo e análise térmica / Comparative chemical study of endodontics sealers according to the presence of calcium hydroxide: dissolution velocity and thermal analysis

A utilizaçäo de cimentos endodônticos contendo cálcio na forma de hidróxido (Sealer 26) ou de óxido (Sealapex), vem sendo objeto de vários estudos nos últimos anos, principalmente no que diz respeito ao selamento, biocompatibilidade, atividade antimicrobiana, prevençäo das reabsorçöes externas, capacidade de alterar o pH e outros. Nesse experimento, com intuito de verificar a alcalinizaçäo do meio mediante mediçäo do pH, desenvolveu-se um sistema de fluxo contínuo em que um eletrólito (soro fisiológico) circula ininterruptamente sobre a superfície do corpo de prova contendo amostra do cimento a ser estudado. Todavia, inicialmente determinou-se por fotometria de emissäo atômica em chama a concentraçäo de cálcio nos cimentos estudados que näo é fornecida pelos fabricantes. Os resultados indicaram que a concentraçäo de íons cálcio no cimento Sealapex é o dobro do cimento Sealer 26. A velocidade de dissoluçäo proveniente da solubilizaçäo do hidróxido de cálcio foi calculada a partir das medidas de pH. Os resultados dessas mediçöes mostraram uma maior alcalinizaçäo do cimento Sealapex, bem como uma velocidade de dissoluçäo estimada, 20 vezes maior quando comparado ao Sealer 26. A seguir, procurou-se estimar a profundidade sob a superfície dos cimentos contidos nos corpos de prova, sujeita a empobrecimento, após exposiçäo ao fluxo de eletrólito por um longo período de tempo. Para isso recorreu-se a análise térmica para estudar o comportamento térmico de fraçöes dos cimentos retirados dos corpos de prova. Para uma melhor compreensäo desse estudo, levantou-se as curvas TG/DTG dos cimentos sob as mais variadas situaçöes experimentais. Os resultados mostraram diminuiçäo superficial da concentraçäo de cálcio, devido a solubilizaçäo do hidróxido de cálcio. Em relaçäo as outras condiçöes analisadas, o cimento Sealapex mostrou um comportamento mais complexo, comparado ao cimento Sealer 26

Propriedades físicas dos cimentos endodônticos Endobalsam e N-Rickert / Physical properties of root canal sealers Endobalsam and N-Rickert

Este estudo compara os cimentos endodônticos Endobalsam e N-Rickert quanto a escoamento, tempo de trabalho, espessura da película e radiopacidade. Foi empregada a metodologia descrita na especificaçäo n§ 57 da ADA. Os resultados mostraram diferenças significantes entre o Endobalsam e o N-Rickert com relaçäo ao escoamento (46 e 44 mm, respectivamente), ao tempo de trabalho (5'00 e 5'30"), à espessura da película (40 e 75 mm) e à radiopacidade (equivalente a escada de alumínio de 4 mm e além de 10 mm). Quanto ao escoamento, ambos cumpriram com as especificaçöes da ADA. Com relaçäo ao tempo de trabalho e à espessura da película, o cimento N-Rickert mostrou valores maiores, mas näo atende a especificaçäo da ADA quanto à espessura do filme. A radiopacidade dos cimentos testados foi exigida pela ADA

Bioavailability of components of resin-based materials which are applied to teeth.

Chemical components of many materials used in dental practice can move into the local biophase, where they can have beneficial or adverse effects. The strongest indirect evidence that components of resin-based materials used in dentistry can move into the biophase are the many reports of allergic dermatitis in dental personnel. Direct measurement of component release has shown that triethylene glycol dimethacrylate (TEGDMA), hydroxyethyl methacrylate (HEMA), and, in the case of some orthodontic cements, bis-glycidyl methacrylate and benzoyl peroxide can move into an aqueous medium from a range of resin-based materials which are applied to teeth as part of oral care. In the case of resin composite restorations, HEMA and TEGDMA are available in microgram quantities via the salivary surface in the minutes and hours after clinical placement and via dentin and pulp in the hours and days after placement. Fortunately, moderate thickness of dentin protects pulp tissue against local toxicity. There are no data which suggest that systemic toxicity is a risk with any of these materials. There are some case reports of allergic responses to the monomers in patients, but the incidence of such responses appears at present to be much lower than that in dental personnel.

Movement of resin cement components through acid-treated dentin during crown cementation in vitro.

This study examined the hypothesis that components of crown cements may be forced through acid-treated dentin during cementation. Freshly extracted, human third molar teeth were prepared to accept full crowns. Roots were removed to allow irrigation of the pulp chamber with saline before, during, and after crown placement with resin dentin bond and resin composite cement. Saline samples were collected and analyzed by high performance liquid chromatography to identify and quantify resin components arriving in the pulp space. Two components of the bond-cement system used were identified in the pulp space samples immediately after crown cementation. These were 2-hydroxyethylmethacrylate and 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane. The amounts of these components in the pulp space decreased when the bonding agent was cured prior to crown placement. The results of this study supported the hypothesis that crown cementing components may flow through acid-treated dentin during crown cementation.

Enamel, cementum and dentin fluoride uptake from a fluoride releasing resin composite.

The purpose of this study was to determine the fluoride release by and the enamel, cementum and dentin fluoride uptake from a visible light-cured fluoride-containing resin composite. Seven circular discs of the composite were prepared and the fluoride release in distilled water determined at daily intervals for 14 days, and then after 30, 90, 180, 365 and 550 days. The baseline fluoride concentrations in enamel and cementum were determined in three successive depths by an acid etch biopsy procedure and in dentin by an abrasion biopsy procedure. Composite slabs were prepared and ligated to the enamel, cementum and dentin surfaces and the teeth were suspended in synthetic saliva for 7 or 30 days. After removal of the composite, similar biopsy procedures were performed. The teeth were then immersed in 1 M KOH for 24 hours and similar biopsies done. The fluoride concentrations were adjusted to standardized depths of 2.0 microns for enamel, 4.0 microns for cementum and 10.0 microns for dentin, and the total and bound fluoride uptake calculated. The fluoride release from the composite dropped sharply after 1 day and after 180 days reached a plateau which remained relatively constant up to 550 days. The results of this in vitro study indicated that the mineralized dental tissues acquired fluoride at various depths.

Systemic release of corticosteroids following intra-dental use.

Concern has been expressed in the past that the use of corticosteroids within root canal medicaments or pulp capping agents may lead to deleterious systemic effects. Calculations of the highest possible amounts that could be used, plus an analysis of the release and diffusion characteristics, and comparisons with known endogenous levels of corticosteroids, reveal that the intradental use of Ledermix paste and Ledermix cement is unlikely to result in any systemic side-effects.