Efecto de la aplicación activa con aplicadores mejorados de un adhesivo universal / Effect of the active application of a universal adhesive with improved applicators

RESUMEN Introducción: La permeabilidad dentinaria es conocida como el paso de fluidos, iones, partículas, moléculas y bacterias a través de la dentina bajo ciertas condiciones. Objetivo: Determinar la influencia de la aplicación activa con un aplicador mejorado de un adhesivo dentinario sobre la conductancia hidráulica dentinaria humana, in vitro. Métodos: Estudio experimental in vitro en 40 terceros molares libres de caries, con indicación de exodoncia, provenientes de pacientes sanos entre 15 y 30 años, previo consentimiento informado. Posteriormente se limpiaron, desinfectaron y conservaron para ser incluidos en bloques de resina epóxica. Luego se realizaron cortes transversales y se obtuvieron discos dentinarios de 1,5 mm de espesor y 25 mm de diámetro. Se dividieron en dos grupos de 20 unidades cada uno, se sometieron a grabado con ácido ortofosfórico al 37 por ciento, y se lavaron y secaron. Sobre una balanza de precisión se les aplicó adhesivo dentinario fotopolimerizable, registrando la fuerza ejercida. En el grupo 1 se usó un microbrush en la aplicación y en el grupo 2 un aplicador mejorado diseñado especialmente. Posteriormente cada muestra fue sometida a una cámara de difusión para obtener la tasa de flujo y luego calcular la conductancia hidráulica, la cual otorga información acerca de la permeabilidad de la dentina. Resultados: los resultados obtenidos fueron levemente menores en el grupo 2, sin embargo, experimentaron una distribución normal. Conclusiones: no existen diferencias significativas, al ser analizados estadísticamente bajo diversas pruebas, en los valores de conductancia hidráulica. Tampoco se pudo establecer una relación inversa entre la fuerza de aplicación de un adhesivo en forma activa con un aplicador mejorado y la conductancia hidráulica, por lo cual no se aconseja el uso de dicho instrumento(AU)

ABSTRACT Introduction: Dentin permeability is defined as the passage of fluids, ions, particles, molecules and bacteria through the dentin under certain conditions. Objective: Determine the effect of the active application of a dentin adhesive with an improved applicator on human dentin hydraulic conductance in vitro. Methods: An in vitro experimental study was conducted of 40 caries-free third molars with an indication of exodontia from healthy patients aged 15-30 years, prior informed consent. The molars were cleaned, disinfected and preserved to be included in epoxy resin blocks. Cross-sectional cuts were then made to obtain dentin discs 1.5 mm thick and 25 mm in diameter. These were divided into two 20-unit groups, were subjected to etching with 37 percent orthophosphoric acid, and were washed and dried. On a precision scale photopolymerizable dentin adhesive was applied, recording the force exerted. Application was performed with a Microbrush applicator in Group 1 and with an improved dedicated applicator in Group 2. The samples were then placed in a diffusion chamber to determine flow rate and subsequently estimate hydraulic conductance, thus obtaining information about dentin permeability. Results: Results were slightly lower in Group 2, but they displayed normal distribution. Conclusions: Statistical analysis with various tests did not find any significant differences in hydraulic conductance values, nor could an inverse relation be established between the force of active application of an adhesive with an improved applicator and hydraulic conductance. Therefore, use of that instrument is not advised(AU)

Evaluation of dentin permeability of fluorotic permanent teeth.

OBJECTIVE: The in vitro permeability characteristics of dentin have been studied extensively and used to evaluate the efficacy of various preventative and restorative procedures. The aim of this in vitro study was to precisely determine the dentin permeability of fluorotic premolar teeth using an electronic hydraulic conductance measurement system with photosensors and to compare the data with healthy premolars. METHODS: In total, 40 fluorotic and healthy premolar teeth with complete root formation that were extracted for orthodontic purposes and had no caries, restoration, fractures, or cracks were selected for this study. Teeth were classified according to a modified form of the dental fluorosis index of Thylstrup and Fejerskov. The dentin discs were placed in an electronic hydraulic conductance measurement system equipped with photosensors, which was designed for measurements of dentin permeability. The amount of distilled water passed through each dentin disc (µL/min) under a constant pressure was determined. Dentin permeability data of the fluorotic and healthy teeth were recorded and analyzed statistically. RESULTS: The present study showed that fluorosis influenced the volume of fluid that passed through the dentin and the dentin permeability was decreased, whereas dental fluorosis severity was increased in permanent teeth. CONCLUSION: The number of teeth with fluorosis is increasing, depending on fluorine sources, so more appropriate treatments will need to be evaluated by standardizing the methods employed in related studies.

Dentin permeability of carious primary teeth.

BACKGROUND: Many in vitro studies have used dentine permeability to evaluate the efficacy of various restorative and preventative procedures. The easiest way to evaluate dentine permeability is to calculate its hydraulic conductance (Lp) using fluid filtration methods. Research has examined electronic hydraulic conductance measurement methods that give more precise and reliable results for the permeability of dentine than the classical method. To our knowledge, no study has examined the dentine permeability of carious primary teeth. AIM: This in vitro study determined the dentine permeability of carious primary molars precisely with a new electronic hydraulic conductance measurement system and compared them with healthy primary molars. DESIGN: The study examined 60 carious and noncarious primary second molars with no restorations, fractures, or cracks at different root resorption stages. RESULTS: The results showed that the dentine permeability increased with the severity of caries in primary teeth. CONCLUSION: The dentine permeability of carious primary teeth was higher than that of noncarious primary teeth. Therefore, treatment of primary teeth should be performed more quickly.

The influence of intrinsic water permeation on different dentin bonded interfaces formation.

OBJECTIVES: To determine the effects of intrinsic wetness on the formation of dentin bonding interfaces of four resin cement systems bonded to dentin under different pulpal pressures. METHODS: Thirty-six freshly extracted third molars were selected and processed for dentin µTBS. The teeth were randomly assigned into 12 experimental groups, according to the adhesive luting system [Adper Single Bond Plus (3M ESPE) combined with two luting agents RelyX ARC (3M ESPE) and heated Filtek Z250 Universal Restorative (3M ESPE), Clearfil CD Bond (Kuraray) combined with Clearfil Esthetic Cement (Kuraray), and RelyX Unicem 2 Automix (3M ESPE)] and pulpal pressure (0, 5, and 20 cm of simulated pulpal pressure). Leucite-reinforced glass-ceramic slabs (IPS Empress CAD, Ivoclar Vivadent) of 3mm thickness were bonded to dentin. The samples were stored in distilled water for 24h and then sectioned in X/Y directions across the adhesive interface to obtain specimens with a cross section of 0.8 ± 0.2mm(2). All sticks were fractured by tension at a crosshead speed of 1.0mm/min and the data were submitted to Kruskal-Wallis and Mann-Whitney Tests (α=0.05). Ultrastructural analysis of the interfaces was performed using Confocal Laser Scanning Microscopy (CLSM) and Scanning Electron Microscopy (SEM). RESULTS: The statistical analyses showed that pulpal pressure decreased µTBS for all groups. Significantly higher µTBS values were obtained in heated Z250 group restored without any pulpal pressure. CLSM showed that the uptake of water through the dentin tubuli and their anastomosis of lateral branches during the adhesive luting procedures prevented adequate formation of the dentin bonding interfaces. SEM showed that the luting film created is material- dependent and all adhesive failure occurred at the resin-dentin interface. CONCLUSION: The constant intrinsic wetness replenishment prevents adequate formation of the hybrid layer. CLINICAL SIGNIFICANCE: Intrinsic moisture during adhesive luting procedures significantly affects the interaction between luting materials and dentin subtract and decreases the quality and bonding strength of the resin-dentin bond.

Longitudinal Effect of Surface Treatments Modified by NaOCl-Induced Deproteinization and Nd:YAG Laser on Dentin Permeability.

OBJECTIVE: The purpose of this study was to evaluate dentin permeability after dentin hypersensitivity treatments: fluoride, adhesive system, and collagen deproteinization with and without Nd:YAG laser exposure, and after erosive and abrasive challenges. MATERIALS AND METHODS: Dentin permeability was assessed by measuring dentinal fluid flow using a permeability device. Eighty bovine dentin specimens (6 mm diameter/1 mm thickness) had permeability measured in the presence of the smear layer and after removal of the smear layer by ethylenediaminetetraacetic acid (EDTA). They were then divided into eight groups according to treatment (n = 10): Group C, control; Group L, Nd:YAG laser; Group F, fluoride; Group FL, fluoride plus Nd:YAG laser; Group A, adhesive; Group AL, adhesive plus Nd:YAG laser; Group D, 10% NaOCl plus adhesive; and group DL, NaOCl plus adhesive plus Nd:YAG laser. Nd:YAG laser was irradiated at 60 mJ/pulse/10 Hz/47.7 J/cm2/1 W and applied freehanded without contact for 60 sec. Permeability was measured 24 h after the treatments. The specimens were exposed to erosive and abrasive challenges for 5 days. Erosive challenge was done by immersion in Coca-Cola, four times a day/90 sec each. After the first and last erosive challenge of the day, the abrasive challenge was conducted by brushing the specimens (24,000 cycles/3.8 cm range/200 g weight), and permeability was measured again. Results were analyzed statistically using two factor ANOVA and Tukey tests (α = 0.05). RESULTS: With the exception of groups FL and A, all treatments reduced permeability. A significant reduction in permeability was seen when the treatments were combined with laser exposure. The association of adhesive and Nd:YAG laser led to the lowest rate of permeability after 24 h. NaOCl-induced deproteinization associated with Nd:YAG laser showed the lowest permeability rate after erosive/abrasive challenges. CONCLUSIONS: Dentin hypersensitivity treatments reduced dentin permeability when associated with Nd:YAG laser, even after erosive/abrasive challenges.

A photochemical method for in vitro evaluation of fluid flow in human dentine.

OBJECTIVE: To evaluate the flow dynamics of dentine fluid using a chemiluminescence method in vitro. MATERIALS AND METHODS: Horizontally sliced coronal dentine specimens with thicknesses of 1.4, 1.6, 1.8, and 2.0mm (n=10 each) were prepared from extracted human third molars. After cleaning with EDTA, a mounted specimen was clamped between 2 acrylic chambers attached to both the occlusal and pulpal sides. The occlusal chamber, which was closed with a glass coverslip, was filled with a chemiluminescent solution (0.02% luminol and 1% sodium hydroxide in water). A trigger solution of 1% hydrogen peroxide and 1% potassium ferricyanide was injected into the pulpal chamber at a constant pressure of 2.5 kPa, and allowed to immediately flow into the patent dentinal tubules. Four consecutive measurements (T1-T4) were performed on each sample by recording the emission of chemiluminescence with a photodetector. The relationship between the crossing time of the liquid through the slice and dentine thickness was examined. RESULTS: An apparent time delay was detected between the starting points of the trigger solution run and photochemical emission at T1. Dt (Dt, s) values of each thickness group were 13.6 ± 4.25 for 1.4mm, 18.1 ± 2.38 for 1.6mm, 28.0 ± 2.46 for 1.8mm, and 39.2 ± 8.61 for 2.0mm, respectively. Dt significantly decreased as dentine became thinner towards the pulp chamber (P<0.001). CONCLUSIONS: The velocity of fluid flow increased both with increasing dentine depth or reduction of remaining dentine thickness.

Replacing Amalgam Restorations: A Standardized Protocol Based on Analyzing Tissue Physicochemical Modifications.

Almost 60% of operative dentistry is devoted to replacing restorations. When practitioners have to replace an amalgam restoration, they tend to opt for an adhesive restoration, as it is conservative of tooth tissues and mimics the natural appearance of teeth. Based on a literature review, the aim of this article is to determine the best tissue approach when replacing an old amalgam by a new adhesive restoration. After analyzing and understanding tissue alterations due to the amalgam corrosion process, the authors propose an analytical approach to managing the situation. Both tissue orientated and specific mechanical approaches are developed and should be implemented to carry out the optimal clinical procedure and achieve the most conservative and durable treatment.

Adhesive sealing of dentin surfaces in vitro: A review.

PURPOSE: This review describes the evolution of the use of dental adhesives to form a tight seal of freshly prepared dentin to protect the pulp from bacterial products, during the time between crown preparation and final cementation of full crowns. The evolution of these "immediate dentin sealants" follows the evolution of dental adhesives, in general. That is, they began with multiple-step, etch-and-rinse adhesives, and then switched to the use of simplified adhesives. METHODS: Literature was reviewed for evidence that bacteria or bacterial products diffusing across dentin can irritate pulpal tissues before and after smear layer removal. Smear layers can be solubilized by plaque organisms within 7-10 days if they are directly exposed to oral fluids. It is likely that smear layers covered by temporary restorations may last more than 1 month. As long as smear layers remain in place, they can partially seal dentin. Thus, many in vitro studies evaluating the sealing ability of adhesive resins use smear layer-covered dentin as a reference condition. Surprisingly, many adhesives do not seal dentin as well as do smear layers. RESULTS: Both in vitro and in vivo studies show that resin- covered dentin allows dentin fluid to cross polymerized resins. The use of simplified single bottle adhesives to seal dentin was a step backwards. Currently, most authorities use either 3-step adhesives such as Scotchbond Multi-Purpose or OptiBond FL or two-step self-etching primer adhesives, such as Clearfil SE, Unifil Bond or AdheSE.

Effect of sonic application mode on the resin-dentin bond strength and dentin permeability of self-etching systems.

PURPOSE: To compare manual and sonic adhesive application modes in terms of the permeability and microtensile bond strength of a self-etching adhesive applied in the one-step or two-step protocol. MATERIALS AND METHODS: Self-etching All Bond SE (Bisco) was applied as a one- or a two-step adhesive under manual or sonic vibration modes on flat occlusal dentin surfaces of 64 human molars. Half of the teeth were used to measure the hydraulic conductance of dentin at 200 cm H2O hydrostatic pressure for 5 min immediately after the adhesive application. In the other half, composite buildups (Opallis) were constructed incrementally to create resin-dentin sticks with a cross-sectional area of 0.8 mm² to be tested in tension (0.5 mm/min) immediately after restoration placement. Data were analyzed using a two-way ANOVA and Tukey's test (α = 0.05). RESULTS: The fluid conductance of dentin was significantly reduced by the sonic vibration mode for both adhesives, but no effect on the bond strength values was observed for either adhesive. CONCLUSION: The sonic application mode at an oscillating frequency of 170 Hz can reduce the fluid conductance of the one- and two-step All Bond SE adhesive when applied on dentin.

Dentinal hypersensitivity: a narrative review.

INTRODUCTION: Dentinal hypersensitivity is an exaggerated response to a sensory stimulus that usually causes no response in a normal healthy tooth. It is a source of chronic irritation that can severely affect an individual's eating and drinking habits. The management of tooth hypersensitivity by oral healthcare professionals requires an appreciation of the complexity of the problem together with knowledge of available treatments. AIM: To review the symptoms, contributing oral factors, prevalence, measurement and mechanisms of dentinal hypersensitivity, together with current and potential future therapies for the condition. METHOD: Narrative literature review. PRINCIPLE FINDINGS: The permeability and fluid movement in open, exposed dentinal tubules has provided a favoured theory for stimulus transmission through dentine. Occlusion of dentinal tubules has been identified as a potential method of reducing pain associated with sensitive teeth. Current treatments work to occlude dentinal tubules. However these treatments can be expensive and their effects are often transient. In comparison, future therapies could be based upon either laser or iontophoresis techniques. CONCLUSION: Future therapies may provide a more permanent and cost effective way of treating dentinal hypersensitivity for health care professionals and their patients.

Development and validation of an in vitro model for measurements of cervical root dentine permeability.

OBJECTIVES: The aim of this series of studies was the development and validation of a new model for evaluation of dentinal hypersensitivity (DH) therapies. MATERIALS AND METHODS: Roots from extracted human teeth were sealed with a flowable composite. In the cervical area, a 3-mm-wide circular window was ground through the seal 1 mm deep into dentine. The pulp lumen was connected to a reservoir of artificial dentinal fluid (ADF) containing protein, mineral salts and methylene blue. At increased pulpal pressure, the ADF released through the said window was collected in containers each with 20 ml of physiologic saline for a consecutive series of 30-min intervals and ADF concentration (absorption) was determined photometrically. The model was verified by three experiments. In experiment 1, the lower limit of quantification (LLoQ, coefficient of variation = 20 % and difference of 5 standard deviations (SD) from blank) of ADF in physiologic saline was determined by measuring the absorption of 15 dilutions of ADF in physiologic saline (containing 0.625 ng to 12.5 µg methylene blue/ml) photometrically for ten times. In experiment 2, long-term linearity of ADF perfusion/outflow was investigated using 11 specimens. The ADF released through the window was collected in the said containers separately for each consecutive interval of 30 min for up to 240 min. Absorption was determined and analysed by linear regression over time. In experiment 3, perfusion before (2×) and after single treatment according to the following three groups was measured: BisGMA-based sealant (Seal&Protect®), an acidic fluoride solution (elmex fluid®) and control (no treatment). RESULTS: In experiment 1, the LLoQ was 0.005 µg methylene blue/ml. In experiment 2, permeability was different within the specimens and decreased highly linearly with time, allowing the prediction of future values. In experiment 3, Seal&Protect® completely occluded dentinal tubules. elmex fluid® increased tubular permeability by about 30 % compared to control. CONCLUSIONS: A model comprising the use of artificial dentinal fluid was developed and validated allowing screening of therapeutic agents for the treatment of DH through reliable measurement of permeability of cervical root dentine. CLINICAL RELEVANCE: The described in vitro model allows evaluation of potential agents for the treatment of DH at the clinically relevant cervical region of human teeth.

Laboratory validation of a new gas-enhanced dentine liquid permeation evaluation system.

AIM: To validate a new automated dentine permeability testing platform based on pressure change measurements. METHODOLOGY: A split chamber was designed allowing for concomitant measurement of fluid permeation and pressure difference. In a first test, system reliability was assessed by interposing a solid metal disk, embedded composite resin disks, or teeth by consecutively measuring eight times under standardized conditions. Secondly, the repeatability and applicability of the method was tested in a dentine wound model by using intact third molars: Class I (2 × 5 mm) and a full occlusal preparation as well a ceramic restoration were consecutively performed and repeatedly measured eight times each. In the last test, the system detection limit as well correlation between gas pressure difference and liquid permeation were evaluated: Again, third molars were used and occlusal preparations of increasing size (2 × 5, 3 × 5, 4 × 5, and 5 × 5 mm and full occlusal preparations, respectively) were made. Data was analyzed for the linearity of measurement, and R (2) values were calculated. RESULTS: The embedding procedure allowed for perfect separation of the two chambers, and no significant variation in repeated measurements of evaluated samples for the respective treatments (p = 0.05) was found. The detection was 0.002 hPa/min for the pressure slope and 0.0225 µl/min for the fluid infiltration, respectively. The saline volume was highly correlating to the gas pressure changes (R (2) = 0.996, p < 0.0001). CONCLUSIONS: The presented method is a reliable and exact tool to assess dentine permeability by nondestructive and repeatable measurements. CLINICAL RELEVANCE: This method is suitable for measurements and comparison of the effectiveness of dentine wounds sealing materials.

Influence of type of bur and acid etching on dentin hydraulic conductance

El objetivo de este estudio fue comparar la tasa de filtración ex vivo (conductancia hidráulica) en discos de dentina humana tratados mecánicamente con fresas de diamante de diferente granulometría y carbide con o sin grabado ácido. Método: 60terceros molares sanos recientemente extraídos de pacientes entre 18-30 años, fueron limpiados, desinfectados (0.1% timol) e incluidos en bloques de resina epóxica. Los discos de dentinase obtuvieron mediante la reducción de la superficie oclusal con instrumentos rotativos cilíndricos, formando los siguientes nueve grupos de 12 muestras c/u: 1: grano fino (FG); 2: granomedio (MG); 3: grano grueso (CG); 4: fresas de carburotungsteno (C); 5: FG con grabado ácido (AO); 6: GM con AO;7: GG con AO; 8: C con AO; 9: sólo grabado ácido. Se determinó la conductancia hidráulica en el modelo experimental bajo presión constante de 200 mm de altura de H2O. No seobservaron diferencias entre la conductancia hidráulica entre los diferentes tipos de fresas (p = 0,5).Se encontraron diferencias en la conductancia hidráulica de discos de dentina con y sin grabado ácido (p < 0,001). El tipo de fresa no afecta la conductacia hidráulica dentinaria.El grabado ácido aumenta significativamente la conductanciahidráulica dentinaria

How can sensitive dentine become hypersensitive and can it be reversed?

This paper reviews a number of studies in oral biology and endodontics that deal with the reactivity of the pulpo-dentine complex in response to mechanical and immunological stimuli. It can be hypothesized that these reactions could also apply to changes in dentine sensitivity following periodontal procedures. Some of these changes involve neurogenic inflammation of the pulp under exposed open tubules; this increases the rate of outward fluid flow through the tubules, making the overlying exposed dentine more sensitive. Other changes may be due to inflammation-related nerve sprouting of pulpal nerves, which can lead to innervation of more tubules than normal. Changes may also involve upregulation of new, more sensitive ion channels in the membranes of these nerves. The goal of the paper is to increase awareness of the complex issues involved in dentine sensitivity, so that future investigators may develop agents or techniques to stimulate mechanisms that mitigate dentine sensitivity, or to block mechanisms that aggravate the condition, for therapeutic effect.

The durability of phosphoric acid promoted bioglass-dentin interaction layer.

OBJECTIVES: Phosphoric acid-Bioglass 45S5 paste can create an interaction layer formed of calcium-phosphate crystals on the dentin surface. In this study, the efficiency of decreasing the dentin permeability exerted by the interaction layer formed between bioglass and dentin was compared to a resin-containing oxalate desensitizing agent (MS Coat One) and a resin-free oxalate desensitizing agent (Super Seal). METHODS: Dentin permeability was measured before/after a brushing abrasion challenge, followed by examining the top and the fractured dentin surfaces with a field emission scanning electron microscope. Moreover, the chemical nature of the compounds formed on top of the dentin surface was examined using the field emission scanning electron microscope (FE-SEM) equipped with an energy-dispersive X-ray spectroscope (EDS), and the crystalline structures of the dentinal surfaces were examined by X-ray diffraction (XRD). RESULTS: The results showed that application of 45S5 bioglass paste to dentin was able to occlude patent dentinal tubule orifices with a layer of calcium-phosphate crystals, while the oxalate containing agents were able to form small crystals which were found in dentinal tubule orifices and scattered along the superficial parts of the dentinal tubule lumen. The brushing-abrasion challenge significantly increased the permeability of dentin treated by Super Seal and MS Coat One, while these challenges had no significant effect on the dentin permeability of specimens treated with 45S5 bioglass paste. SIGNIFICANCE: The new technique provided better durability than two products available on the market. Moreover, our previous research showed the biocompatibility of using this technique on dental pulp cells, suggesting that this technique can aid in treating dentin hypersensitivity cases.

In vitro evaluation of dentinal hydraulic conductance and tubule sealing by a novel calcium-phosphate desensitizer.

In the current trend of materials used for dentin hypersensitivity treatment, calcium-phosphate-containing desensitizers are expected to have advantages in oral environment. A newly formulated desensitizer containing tetracalcium phosphate and dicalcium phosphate anhydrous (CPD-100) was evaluated in comparison to oxalate containing desensitizer (SS) regarding permeability reduction (PR%) by measuring hydraulic conductance on the etched dentin discs in vitro. CPD-100 exhibited mean PR% of 91%, which significantly increased to 98% after immersion in artificial saliva (AS) for 4 weeks (p < 0.001), while SS showed a significant decrease from 99% to 93% (p < 0.01). SEM observation showed newly formed crystallites on CPD-100 treated dentin, which did not exist in SS treated dentin after AS immersion, suggesting that calcium oxalate inhibited formation of new calcium-phosphate minerals. Five-minute acid challenge did not significantly affect PR% of dentin treated by any of the desensitizers. The energy dispersive X-ray spectroscopy (EDS) analysis indicated that the formed layer of CPD-100 were minerals with similar Ca/P ratio to hydroxyapatite. In conclusion, the newly developed calcium-phosphate desensitizer has the potential to exhibit long-term stability in the oral environment, owing to its chemical properties that promote the crystal growth in salivary fluid.

Influence of type of bur and acid etching on dentin hydraulic conductance.

The aim of this study was to compare ex vivo filtration rate (hydraulic conductance) in human dentin discs mechanically treated with diamond and carbide burs of different grain size with or without acid etching. Method: 60 healthy third molars, recently extracted from patients aged 18-30 years, were cleaned, disinfected (0.1% thymol) and embedded in epoxy resin blocks. Dentin discs were obtained by cutting the occlusal surface with cylindrical rotary instruments, forming nine groups containing 12 specimens each: 1: fine grain (FG); 2: medium grain (MG); 3: coarse grain (CG); 4: carbide (C) burs; 5: FG with acid etching (AE); 6: MG with AE; 7: CG with AE; 8: C with AE; 9: only AE. Hydraulic conductance was determined in the experimental model under constant pressure of 200mm H2O. No difference in hydraulic conductance was observed among dentin discs treated with different types of burs (p = 0.5). Differences were found in the hydraulic conductance of etched and non-etched dentin discs (p < 0.001). The type of mechanical bur treatment does not affect dentin hydraulic conductance. Acid etching significantly increases dentin hydraulic conductance.

Influence of type of bur and acid etching on dentin hydraulic conductance. / Influence of type of bur and acid etching on dentin hydraulic conductance.

The aim of this study was to compare ex vivo filtration rate (hydraulic conductance) in human dentin discs mechanically treated with diamond and carbide burs of different grain size with or without acid etching. Method: 60 healthy third molars, recently extracted from patients aged 18-30 years, were cleaned, disinfected (0.1

thymol) and embedded in epoxy resin blocks. Dentin discs were obtained by cutting the occlusal surface with cylindrical rotary instruments, forming nine groups containing 12 specimens each: 1: fine grain (FG); 2: medium grain (MG); 3: coarse grain (CG); 4: carbide (C) burs; 5: FG with acid etching (AE); 6: MG with AE; 7: CG with AE; 8: C with AE; 9: only AE. Hydraulic conductance was determined in the experimental model under constant pressure of 200mm H2O. No difference in hydraulic conductance was observed among dentin discs treated with different types of burs (p = 0.5). Differences were found in the hydraulic conductance of etched and non-etched dentin discs (p < 0.001). The type of mechanical bur treatment does not affect dentin hydraulic conductance. Acid etching significantly increases dentin hydraulic conductance.

Dentin hypersensitivity.

CONTEXT: In dental practice, dentin hypersensitivity is a commonly presenting condition, which consists of sharp pain arising from exposed dentin in response to a varied assortment of stimuli; for example, dietary factors, such as an ice-cold beverage, to even environmental considerations, such as the exposure to atmospheric air on a cold winter's day. The heterogeneity of this presentation, ranging from minor inconvenience to the patient, to a near incapacitating quality-of-life disturbance, as well as the wide range of treatment strategies, as is discussed in this article, certainly pose a challenge to the clinician. EVIDENCE ACQUISITION: A search was performed on the MEDLINE database (2002 to present) by way of OVID. Search terms, such as dentin hypersensitivity and variants (eg, dentinal hypersensitivity, cervical dentin hypersensitivity) were used. Select references of review-type articles from the original search were sought. EVIDENCE SYNTHESIS: Efforts were made to identify multiple comparative clinical treatment studies that were of highest quality study design-specifically, randomized control trials. Efforts also were made to identify rigorous meta-analysis in the literature on the subject of dentin hypersensitivity treatment. CONCLUSION: Although multiple treatment approaches appear to provide clinical success in managing dentin hypersensitivity, the entire body of clinical research literature is far from being unequivocal in pronouncing one superior strategy. Equally as important is the clinician's consideration of the predisposing factors that initially localized the lesion on the tooth surface. Together, personalized preventive measures and therapies focusing on disrupting pathophysiology form the core of effective dentin hypersensitivity management.

Tricalcium silicate induced mineralization for occlusion of dentinal tubules.

BACKGROUND: The aim of this study was to evaluate the dentinal tubule occluding ability of tricalcium silicate (Ca(3) SiO(5) or C(3) S) in vitro. METHODS: Dentine discs were prepared from extracted caries-free human third molars and etched with 0.02 M citric acid (pH 4) for 3 minutes in order to produce patent dentinal tubules. Tricalcium silicate pastes of different viscosities were applied to the surface of the dentine specimens for 3 minutes and then removed with a swab followed by deionized water rinse. The dentine specimens were immersed in artificial saliva for 7 days. The tubule occlusion, sealing depth and chemical composition of the dentine specimens and bonding force between the dentine matrix and mineralized layer were evaluated by scanning electron microscopy, energy dispersion X-ray spectroscopy, X-ray diffraction analysis and a nanoscratch test. RESULTS: A homogeneous layer of mineral crystals was precipitated onto the dentine surface and caused significant occlusion of the dentinal tubules. The dentine permeability and sealing depth of the C(3) S increased with the decrease of viscosity of the paste. With a proper viscosity of C(3) S pastes, the interface between the mineralized layer and the dentine matrix bonded well. CONCLUSIONS: This study suggests that C(3) S may be an effective agent for the treatment of dentine hypersensitivity.