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.

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.

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.

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.

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.

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.

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.

Management of dentinal hypersensitivity.

Dentinal hypersensitivity is a complex condition that can cause considerable concern in the dental office. Despite the large number of available treatment modalities, no current desensitizing agent is considered ideal for managing this uncomfortable condition. Selecting the right therapy requires a complete understanding of how applying a stimulus to the exposed dentin surface can influence the nerve fibers and produce hyperesthesia. This article reviews the etiology and critically analyzes management of dentinal hypersensitivity by reviewing laboratory and clinical investigations.

Advances in methodologies to characterize dentine and dentine hypersensitivity treatments in vitro.

The aim of this paper is to highlight recent advances in the development of analytical and in vitro methodologies to assess the potential efficacy of dentine hypersensitivity treatments. The paper will cover the utility of X-ray computed nanotomography, secondary ion mass spectrometry, dynamic laser scanning confocal microscopy, and x-ray microtomography in the context of characterizing dentine, understanding the permeability and mass transport properties of dentine, and exploring the mechanism of action for purported hypersensitivity treatments. It will be shown that X-ray tomography, secondary ion mass spectrometry, and dynamic fluid flow confocal microscopy provide unsurpassed information pertaining to the ultra-structural and mass transport properties of dentine, properties that underpin the hydrodynamic theory and the therapeutic route for desensitizing treatments. The paper concludes that advances in analytical instrumentation and in vitro methodologies have improved our understanding of the ultra-structural and chemical properties of dentine, mass transport within dentine, and the quality and predictive value of in vitro models. Such understandings aid the development of efficacious dentifrice formulations to treat dentine hypersensitivity.

Ammonium hexafluorosilicate elicits calcium phosphate precipitation and shows continuous dentin tubule occlusion.

UNLABELLED: Diamine silver fluoride [AgF: (NH(3))(2)AgF] has been used clinically in Japan, as it reduces dental caries and dentin hypersensitivity. However, AgF stains the teeth black due to silver precipitation. To overcome this drawback, the authors prepared ammonium hexafluorosilicate [SiF: (NH(4))(2)SiF(6)], which does not stain the teeth, and SiF occluded open dentin tubules completely with silica-calcium phosphate precipitate. OBJECTIVES: The aim of this study was to evaluate the duration of dentin tubule occlusion after SiF treatment in a simulated oral environment. METHODS: To simulate dentin tubules subject to dentin hypersensitivity, dentin disks were treated with EDTA for 2 min. The disks were treated with 0.476 mol/L SiF for 3 min, and then the disks were immersed in synthetic saliva, which was regularly replenished to maintain its ionic concentration, for up to 7 days. The occluding ability of the dentin tubules was evaluated using scanning electron microscopy (SEM), and the hydraulic conductance was measured following Pashley's method at regular intervals. RESULTS: SEM photographs demonstrated that dentin tubules were occluded homogeneously and completely with the precipitate at 7 days after treatment with SiF. In addition, newly formed calcium phosphate precipitate was present at the dentin surface. The dentin permeability showed a consistently low value throughout the experimental period. The values immediately after SiF treatment and 7 days after immersion were 11.9+/-3.7% and 7.9+/-2.9%, respectively. SIGNIFICANCE: Ammonium hexafluorosilicate is useful for the treatment of dentin hypersensitivity, since ammonium hexafluorosilicate induced calcium phosphate precipitation from the saliva; therefore, it has a continuous effect on dentin tubules occlusion under a simulated oral environment.

Influence of tooth age and root section on root dentine dye penetration.

AIM: To investigate dye permeability of root dentine according to patients' age, root section and dye penetration time. METHODOLOGY: A total of 96 extracted human single-rooted teeth, assigned to four age groups (<30, 30-45, 45-60 and >60 years) were separated at the cemento-enamel junction and root canals were enlarged. The root surfaces were coated with cyanocrylate to prevent external dye penetration and centrifuged in distilled water to eliminate air. For dye penetration the root canals were filled with methylene blue 5%. After 1, 30 and 60 days eight roots per age group were cross-sectioned in 1 mm slices. Dye penetrated areas and the complete dentine areas were digitized and measured. Differences between groups were judged with anova and LSD, P < 0.05 or P < 0.01. RESULTS: The root section, the patients' age and the penetration time influenced significantly the penetrated areas (P < 0.05). After 1 and 30 days significant differences could be found only in the apical root sections between all age groups (P < 0.05). Dye penetration areas systematically decreased with increasing age and also from coronal to apical (P < 0.01). CONCLUSIONS: Age influenced dye penetration significantly. Dye penetration also depended on the location (coronal, middle and apical) within the root canal. These findings indicate that there may be a correlation between the tooth age and permeability of root dentine, which may influence the distribution and effectiveness of drugs used for root canal disinfection.

Laser scanning confocal microscopy coupled with hydraulic permeability measurements for elucidating fluid flow across porous materials: application to human dentine.

Laser scanning confocal microscopy (LSCM) coupled to a constant volume flow-pressure measuring system is introduced as a new technique for the quantitative measurement of fluid flow across porous materials. Such processes are ubiquitous from the life sciences to materials science and the methodology herein could find widespread application. The methodology has been applied to the detection of fluid flow through human dentine, in-vitro, and in the assessment of occlusion actives. Dentine is a calcareous material sandwiched between the pulp and enamel in the tooth structure that contains tubules which traverse dentine in the pulp to enamel direction. The tubules become patent during enamel erosion or gum recession, leading to dentinal hypersensitivity. Understanding the nature of fluid flow is important, as a pressure gradient exists across dentine in-vivo and this has implications for the development of suitable treatments. The methodology described herein firstly allows a ready assessment of the general efficacy of treatments via hydraulic permeability measurements. Second, LSCM images allow the nature of the flow process and the mode of action of the treatments to be revealed at high spatial resolution. For the particular case of dentine, we demonstrate how the method allows candidate treatments to be compared and assessed.

Iontophoresis significantly increases the trans-dentinal delivery of osteoprotegerin, alendronate, and calcitonin.

The purpose of this study was to evaluate the delivery of alendronate, calcitonin, and osteoprotegerin (OPG) through human dentin by both diffusion and iontophoresis for the potential treatment of invasive cervical resorption. Radiolabeled alendronate, calcitonin, and OPG were added to the top of a split chamber device that contained 1-mm thick dentin disks devoid of a smear layer. Transdentinal movement of medicaments by either random diffusion or application of an iontophoretic current was measured by analysis of gamma emission of effluent fractions. In addition, calcitonin delivery was evaluated at differing magnitudes of current (0-4 mA) by using the aforementioned chamber. Diffusion of all 3 medicaments was minimal. In contrast, the application of a 3-mA iontophoretic gradient significantly increased delivery for all 3 compounds at 10-, 20-, and 30-minute intervals. In addition, a linear increase in permeability was seen for calcitonin as milliamperes were increased from 0 to 4 (r = 0.947), with more than a 100-fold increase in delivery observed with iontophoresis. Delivery of the tested medicaments by using iontophoresis might prove to be a useful technique for treatment of invasive cervical resorption.

In vitro evaluation of dentin permeability of fluorotic primary teeth with a new electronic hydraulic conductance measurement system with photosensors.

OBJECTIVES: The permeability characteristics of dentin have been used in many in vitro studies to evaluate longitudinally the efficacy of various restorative and preventative procedures. The easiest way to evaluate dentin permeability is to calculate its hydraulic conductance (Lp) by fluid filtration method. There are researches on electronic hydraulic conductance measurement systems which can give more precise and reliable results of permeability of dentine than the classical system. To the authors' knowledge, there are no studies on bonding properties of restoratives to fluorotic primary teeth and dentin permeability of those teeth in the literature. The aim of this in vitro study was to determine the dentin permeability of fluorotic primary molars precisely with a new 'electronic hydraulic conductance measurement system with photosensors' and to compare the data with healthy primary molars. METHODS: A total of 40 fluorotic and healthy primary second molar teeth with 1/3 root resorption, which were extracted for orthodontic purpose and with no caries, restoration, fracture or crack were selected and used in this study. Teeth were classified according to the modified form of dental fluorosis index of Thylstrup&Fejerskov. Dentin discs were placed in the electronic hydraulic conductance measurement system with photosensors which was designed for the measurement of dentin permeability. The amount of distilled water passed through each dentin disk (muL/min) under a constant pressure was determined. Dentin permeability data of the fluorotic and healthy teeth were recorded and analysed statistically. RESULTS: It was observed that dentin permeability decreases, while dental fluorosis severity increases in primary teeth.

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.

Pressure transmission across dentine in response to an external pressure: a laboratory study.

PURPOSE: To determine whether transducers could provide a convenient method of measuring dentine permeability and to investigate the effects of removal of pulp tissue and perfusion time on the pressure increase across human dentine after low-pressure perfusion. METHOD: Human premolar teeth that had been stored for 1-2 months were prepared for full crown preparations. The pulp tissue was removed from half the samples and all the coronal segments perfused with saline at 1.3kPa for varying times. An external pressure was then applied and the response within the pulp chambers recorded with transducers. RESULTS: Extirpation of pulp tissue reduced the rate of rise of pressure inside the pulp chamber by approximately 50%. Perfusion at 1.3kPa for up to 1h had no effect on pressure rise, but 6h of perfusion produced a very significant increase. CONCLUSION: Transducers can provide a relatively simple, convenient and clinically relevant measurement of dentine permeability. For stored coronal segments that have been perfused at physiological pressures, extirpation of pulp tissue and perfusion time have significant effects on pressure transmission across dentine.