Translucency changes of direct esthetic restorative materials after curing, aging and treatment.

The purpose of this article was to review the changes in translucency of direct esthetic restorative materials after curing, aging and treatment. As a criterion for the evaluation of clinical translucency changes, visual perceptibility threshold in translucency parameter difference (ΔTP) of 2 was used. Translucency changes after curing were perceivable depending on experimental methods and products (largest ΔTP in resin composites = 15.9). Translucency changes after aging were reported as either relatively stable or showed perceivable changes by aging protocols (largest ΔTP in resin composites = -3.8). Translucency changes after curing, aging and treatment were perceivable in several products and experimental methods. Therefore, shade matching of direct esthetic materials should be performed considering these instabilities of translucency in direct esthetic materials.

Bone cement with a modified polyphosphate network structure stimulates hard tissue regeneration.

In this study, a calcium polyphosphate cement (CpPC) consisting of basic components was investigated to assess its potential for hard tissue regeneration. The added basic components for improving the structural stability, which controlled the setting time, where the setting reaction resulted in the formation of amorphous structure with a re-constructed polyphosphate. Moreover, the characteristics were controlled by the composition, which determined the polyphosphate structure. CpPC exhibited outstanding dissolution rate compared with the common biodegradable cement, brushite cement (2.5 times). Despite high amounts of dissolution products, no significant cytotoxicity ensued. Induction of calcification in MG-63 cells treated with CpPC, the level of calcification increased with increasing CpPC dissolution rate. Induced calcification was observed also in CpPC-treated ST2 cells, in contrast with MG-63 and ST2 treated with brushite cement, for which no calcification was observed. In vivo tests using a rat calvarial defect model showed that resorbed CpPC resulted in favorable host responses and promoted bone formation. Additionally, there was a significant increase in defect closure, and new bone formation progressed from CpPC mid-sites as well as defect margins. From these results, CpPC exhibits significant potential as biodegradable bone substitute for bone regeneration.

Criteria for clinical translucency evaluation of direct esthetic restorative materials.

The purpose of this review was to suggest practical criteria for the clinical translucency evaluation of direct esthetic restorative materials, and to review the translucency with these criteria. For the evaluation of reported translucency values, measuring instrument and method, specimen thickness, background color, and illumination should be scrutinized. Translucency parameter (TP) of 15 to 19 could be regarded as the translucency of 1 mm thick human enamel. Visual perceptibility threshold for translucency difference in contrast ratio (ΔCR) of 0.07 could be transformed into ΔTP value of 2. Translucency differences between direct and indirect resin composites were perceivable (ΔTP > 2). Universal and corresponding flowable resin composites did not show perceivable translucency differences in most products. Translucency differed significantly by the product within each shade group, and by the shade group within each product. Translucency of human enamel and perceptibility threshold for translucency difference may be used as criteria for the clinical evaluation of translucency of esthetic restorative materials.

Opalescence of human teeth and dental esthetic restorative materials.

Human tooth enamel is opalescent, which renders teeth bluish in reflected and orange in transmitted color. The aim was to review opalescent property of teeth and application and mimetic reproduction in esthetic restorations. A PubMed search for articles published in English till 2015 on the opalescence of teeth and esthetic materials revealed 29 relevant papers. Opalescence was measured with OP-RT index, which was calculated as the difference in the yellow-blue and red-green color coordinates between the reflected and transmitted colors. Mean OP-RT value of human enamel was 22.9. OP-RT values of direct resin composites changed after polymerization, and the range in these materials was 5.7-23.7. OP-RT value ranges were 1.6-6.1 and 2.0-7.1 for the core and veneer ceramics, respectively. Since the OP-RT values of esthetic materials were lower than that of enamel, it is recommended that materials that can reproduce the opalescence of enamel be further designed.

Translucency and color match with a shade guide of esthetic brackets with the aid of a spectroradiometer.

OBJECTIVE: Since the color of esthetic brackets should match that of teeth, the aims of this study were to determine the color and translucency of esthetic brackets by means of the clinically relevant use of a spectroradiometer, and to compare the color of brackets with that of a commercial shade guide. METHODS: The color of central and tie-wing regions of four plastic and four ceramic brackets was measured according to the CIE L*a*b* color scale over white and black backgrounds. Brackets were classified into five groups based on their composition. The color of Vitapan Classical Shade Guide tabs was also measured. Translucency parameter (TP) and contrast ratio (CR) were calculated to determine translucency. RESULTS: Color differences between brackets and the shade guide tabs were 10.4 - 34.5 ∆E*ab units. TP and CR values for the central region were 16.4 - 27.7 and 0.38 - 0.58, whereas for the tie-wings they were 24.0 - 39.9 and 0.25 - 0.45, respectively. The color coordinates, TP and CR values were significantly influenced by bracket composition and brand (p < 0.05). CONCLUSIONS: Esthetic brackets investigated herein showed unacceptable color differences (∆E*ab > 5.5) compared with the shade guide tabs. Differences in the translucency of brackets by brand were within the visually perceptible range (∆CR > 0.07). Therefore, brackets showing the best matching performance for each case should be selected considering esthetic and functional demands.

Translucency and color match with a shade guide of esthetic brackets with the aid of a spectroradiometer

ABSTRACT Objective: Since the color of esthetic brackets should match that of teeth, the aims of this study were to determine the color and translucency of esthetic brackets by means of the clinically relevant use of a spectroradiometer, and to compare the color of brackets with that of a commercial shade guide. Methods: The color of central and tie-wing regions of four plastic and four ceramic brackets was measured according to the CIE L*a*b* color scale over white and black backgrounds. Brackets were classified into five groups based on their composition. The color of Vitapan Classical Shade Guide tabs was also measured. Translucency parameter (TP) and contrast ratio (CR) were calculated to determine translucency. Results: Color differences between brackets and the shade guide tabs were 10.4 - 34.5 ∆E*ab units. TP and CR values for the central region were 16.4 - 27.7 and 0.38 - 0.58, whereas for the tie-wings they were 24.0 - 39.9 and 0.25 - 0.45, respectively. The color coordinates, TP and CR values were significantly influenced by bracket composition and brand (p < 0.05). Conclusions: Esthetic brackets investigated herein showed unacceptable color differences (∆E*ab > 5.5) compared with the shade guide tabs. Differences in the translucency of brackets by brand were within the visually perceptible range (∆CR > 0.07). Therefore, brackets showing the best matching performance for each case should be selected considering esthetic and functional demands.

RESUMO Objetivo: considerando-se que a cor dos braquetes estéticos deve corresponder à cor dos dentes, os objetivos do presente estudo foram determinar a cor e a translucidez de braquetes estéticos, por meio do uso clinicamente relevante de um espectroradiômetro, e comparar a cor desses braquetes com a cor de uma escala comercial de cores. Métodos: a cor das regiões central e da aleta de quatro braquetes plásticos e quatro braquetes cerâmicos foi medida segundo o sistema de cores CIE L*a*b*, sobre fundos branco e preto. Os braquetes foram classificados em cinco grupos, de acordo com a sua composição. A cor das peças da escala de cores Vitapan Classical(r) também foi medida. O parâmetro de translucidez (PT) e a razão de contraste (RC) foram calculados para se determinar a translucidez. Resultados: as diferenças de cor entre os braquetes e as peças da escala de cores variaram de 10,4 a 34,5 unidades ∆E*ab. Os valores de PT e RC, respectivamente, variaram de 16,4 a 27,7 e de 0,38 a 0,58 na região central; já para a região das aletas, esses valores variaram de 24,0 a 39,9 e de 0,25 a 0,45. As coordenadas de cor e os valores de PT e RC foram significativamente influenciados pela marca e composição dos braquetes (p < 0,05). Conclusões: os braquetes estéticos investigados nesse estudo demonstraram diferenças de cor inaceitáveis (∆E*ab > 5,5), quando comparados às peças da escala de cores. As diferenças de translucidez entre as marcas de braquetes estavam dentro do limite visualmente perceptível (∆RC > 0,07). Portanto, ao selecionar os braquetes com a melhor correspondência de cor, deve-se levar em consideração as exigências estéticas e funcionais de cada caso.

Color Correlations among Six Types of Permanent Anterior Teeth.

STATEMENT OF PROBLEM: When multiple teeth are missing, the color for missing teeth should be estimated based on the color of remaining teeth. PURPOSE: The purpose was to determine the strength of color correlations among six types of permanent anterior teeth. METHODS: Color of 12 anterior teeth was measured by Shade Vision System for 47 volunteers. The color coordinates in each type of teeth such as maxillary central incisor (MX1), lateral incisor (MX2), and canine (MX3), and mandibular central incisor (MD1), lateral incisor (MD2), and canine (MD3) were determined. Correlations and differences among the corresponding color coordinates of each type of teeth were determined. RESULTS: Compared with MX1, the differences were in the range of -3.2 to -6.5 in L*, 0.5 to 2.7 in a*, -0.7 to 7.5 in b*, and the color difference (ΔE*ab ) was 4.5 to 10.3. The color difference by ΔE00 formula was 3.1-6.7. Although the color coordinates were different by tooth type, they generally showed correlations (p < 0.001). CONCLUSIONS: For the color estimation of missing MX1, the color coordinates of MD1 were the strongest predictors. In case of missing MX3, L* and a* of MD3 and b* of MX1 were the strongest predictors for each corresponding coordinates. CLINICAL SIGNIFICANCE: The color for missing teeth, especially for maxillary central incisor and maxillary and mandibular canines, could be estimated based on those of the same type teeth on the opposing arch. These results should be applied for clinical color selection for missing teeth.(J Esthet Restor Dent 28:S5-S13, 2016).

Bone Tissue Engineering by Using Calcium Phosphate Glass Scaffolds and the Avidin-Biotin Binding System.

Highly porous and interconnected scaffolds were fabricated using calcium phosphate glass (CPG) for bone tissue engineering. An avidin-biotin binding system was used to improve osteoblast-like cell adhesion to the scaffold. The scaffolds had open macro- and micro-scale pores, and continuous struts without cracks or defects. Scaffolds prepared using a mixture (amorphous and crystalline CPG) were stronger than amorphous group and crystalline group. Cell adhesion assays showed that more cells adhered, with increasing cell seeding efficiency to the avidin-adsorbed scaffolds, and that cell attachment to the highly porous scaffolds significantly differed between avidin-adsorbed scaffolds and other scaffolds. Proliferation was also significantly higher for avidin-adsorbed scaffolds. Osteoblastic differentiation of MG-63 cells was observed at 3 days, and MG-63 cells in direct contact with avidin-adsorbed scaffolds were positive for type I collagen, osteopontin, and alkaline phosphatase gene expression. Osteocalcin expression was observed in the avidin-adsorbed scaffolds at 7 days, indicating that cell differentiation in avidin-adsorbed scaffolds occurred faster than the other scaffolds. Thus, these CPG scaffolds have excellent biological properties suitable for use in bone tissue engineering.

Engineered microstructure granules for tailored drug release rate.

Biomaterials developed for controlled drug delivery have demonstrated excellent results in the present study. A biomaterial prepared using hydroxyapatite (HAp) was shown to have a hollow structure with the presence of interconnected pores to house drug carriers. The poly(lactic-co-glycolic acid) particles were used as drug carriers loaded with dexamethasone, a corticosteroid that is known to promote osteoinduction. The surface of the drug carriers was modified using polyethyleneimine, and then conjugated to the surface of HAp granules. The hollow HAp granules had drug carriers on both their inner and outer surfaces and showed a controlled drug release rate that was comparable to that of granules containing drug carriers on their outer surface alone. The pores were designed for insertion of drug carriers and preosteoblasts. Consequently, the biomaterials influenced cellular behavior by first promoting cell proliferation and then inducing early stage osteogenic differentiation. The effects of controlled release rate were evidenced for up to two weeks after cell seeding, resulting in an increase of osteogenic differentiation. In summary, drug carriers loaded onto hollow HAp granules were shown to be suitable for patients who require replacement of missing bone for repair of bone fractures that are extremely complex, pose a significant health risk to the patient, or fail to heal properly.

Fluorescence properties of human teeth and dental calculus for clinical applications.

Fluorescent emission of human teeth and dental calculus is important for the esthetic rehabilitation of teeth, diagnosis of dental caries, and detection of dental calculus. The purposes of this review were to summarize the fluorescence and phosphorescence of human teeth by ambient ultraviolet (UV) light, to investigate the clinically relevant fluorescence measurement methods in dentistry, and to review the fluorescence of teeth and dental calculus by specific wavelength light. Dentine was three times more phosphorescent than enamel. When exposed to light sources containing UV components, the fluorescence of human teeth gives them the quality of vitality, and fluorescent emission with a peak of 440 nm is observed. Esthetic restorative materials should have fluorescence properties similar to those of natural teeth. Based on the fluorescence of teeth and restorative materials as determined with a spectrophotometer, a fluorescence parameter was defined. As to the fluorescence spectra by a specific wavelength, varied wavelengths were investigated for clinical applications, and several methods for the diagnosis of dental caries and the detection of dental calculus were developed. Since fluorescent properties of dental hard tissues have been used and would be expanded in diverse fields of clinical practice, these properties should be investigated further, embracing newly developed optical techniques.

Translucency of human teeth and dental restorative materials and its clinical relevance.

The purpose was to review the translucency of human teeth and related dental materials that should be considered for the development of esthetic restorative materials. Translucency is the relative amount of light transmission or diffuse reflection from a substrate surface through a turbid medium. Translucency influences the masking ability, color blending effect, and the degree of light curing through these materials. Regarding the translucency indices, transmission coefficient, translucency parameter, and contrast ratio have been used, and correlations among these indices were confirmed. Translucency of human enamel and dentine increases in direct proportion to the wavelength of incident light in the visible light range. As for the translucency changes by aging, limited differences were reported in human dentine, while those for enamel proved to increase. There have been studies for the adjustment of translucency in dental esthetic restorative materials; the size and amount of filler and the kind of resin matrix were modified in resin composites, and the kind of ingredient and the degree of crystallization were modified in ceramics. Based on the translucency properties of human enamel and dentine, those of replacing restorative materials should be optimized for successful esthetic rehabilitation. Biomimetic simulation of the natural tooth microstructure might be a promising method.

Translucency of Dental Ceramic, Post and Bracket.

Translucency of dental ceramics, esthetic posts and orthodontic brackets was reviewed. Translucency parameter (TP) and contrast ratio (CR) are generally used for translucency evaluation. For the evaluation of translucency, two criteria such as the translucency of human teeth (TP = 15-19, 1 mm thick) and the visual perceptibility threshold for the translucency difference (∆CR > 0.07 or ∆TP > 2) were used. In ceramics, translucency differences were in the perceptible range depending on the type of material and the thickness. However, variations caused by the difference in the required thickness for each layer by the material and also by the measurement protocols should be considered. As to the translucency of esthetic posts, a significant difference was found among the post systems. Translucency was influenced by the bracket composition and brand, and the differences by the brand were visually perceptible.

Color assimilation of resin composites with adjacent color according to the distance.

STATEMENT OF PROBLEM: Color of esthetic restorative materials shifts toward color of adjacent material. PURPOSE: The purposes were to determine the amount of distance-dependent color shift in resin composites toward the color of adjacent materials and to define a color shift parameter (CSP) that can quantify this phenomenon. METHODS: Three brands of resin composites, two shades for each, were investigated. Specimens of 2 (thickness) × 4 (width) × 16 (length) mm(3) were fixed in an adjustable XY stage in contact with black and white ceramic tiles at each end. Color was measured by a spectroradiometer at seven separated points in 2-mm intervals, in which P1 was 2 mm away from the black tile. Mean value of the color differences (ΔE*ab ) between P1 and each of the other measurement points (P2-P6) was defined as the CSP, in which higher CSP value indicated smaller color assimilation toward P1 color. RESULTS: The range of the CSP was 7.5-12.4, which was influenced by the brand and shade of resin composites (p < 0.05). CONCLUSIONS: The CSP defined in this study provided the amount of color shift of esthetic materials toward adjacent color, which indicated the color assimilation effect of these materials. CLINICAL SIGNIFICANCE: The CSP investigated in the present study might be used to compare the tendency of color assimilation of esthetic restorative materials, and proper CSP ranges for optimal color assimilation or color blocking should be further determined.

Tomographic and histometric analysis of autogenous bone block and synthetic hydroxyapatite block grafts without rigid fixation on rabbit calvaria.

PURPOSE: The preferred material for bone augmentation beyond the envelope of skeletal bone is the bone block graft, due to its dimensional stability. We evaluated the necessity of rigid fixation for the bone block graft, and compared the bone regeneration and volume maintenance associated with grafting using a synthetic hydroxyapatite block (HAB) and an autogenous bone block (ABB) without rigid fixation on rabbit calvaria over two different periods. METHODS: Cylinder-shaped synthetic HAB and ABB were positioned without fixation on the rabbit calvarium (n=16). The animals were sacrificed at 4 or 8 weeks postoperatively, and the grafted materials were analyzed at each healing period using microcomputed tomography and histologic evaluation. RESULTS: Integration of the graft and the recipient bed was observed in all specimens, although minor dislocation of the graft materials from the original position was evident in some specimens (six ABB and ten HAB samples). A tendency toward progressive bone resorption was observed in the grafted ABB but not in the grafted HAB, which maintained an intact appearance. In the HAB group, the area of new bone increased between 4 and 8 weeks postoperatively, but the difference was not statistically significant. CONCLUSIONS: The nonfixed HAB was successfully integrated into the recipient bed after both healing periods in the rabbit calvaria. In spite of limited bone formation activity in comparison to ABB, HAB may be a favorable substitute osteoconductive bone material.

Correlation between three color coordinates of human teeth.

The objective was to determine whether there were significant correlations in the three color coordinates within each of two color coordinate systems, such as the Commission Internationale de l'Eclairage (CIE) L*a*b* system, and the lightness, chroma, and hue angle system, of human vital teeth. The color of six maxillary and six mandibular anterior teeth was measured by the Shade Vision System. Pearson correlations between each pair of the color coordinates were determined (α=0.01 ). The influence of two color coordinates on the other color coordinate was determined with a multiple regression analysis (α=0.01 ). Based on correlation analyses, all the color coordinate pairs showed significant correlations except for the chroma and hue angle pair. The CIE L* was negatively correlated with the CIE a*,b*, and chroma, but positively correlated with the hue angle. The CIE a* was positively correlated with the CIE b* and chroma. Tooth color coordinates were correlated each other. Lighter teeth were less chromatic both in the CIE a* and b* coordinates. Therefore, it was postulated that the three color coordinates of human teeth were harmonized within certain color attribute ranges, and a lack of correlations in these coordinates might indicate external/internal discolorations and/or anomalies of teeth.

Illuminating light-dependent color shifts in core and veneer layers of dental all-ceramics.

The color of an object is perceived differently depending on the ambient light conditions. Since dental all-ceramic restorations are fabricated by building up several layers to reproduce the tooth shade, the optical properties of each layer should be optimized for successful shade reproduction. This study aimed to determine the separate contributions of the color shifts in each of the core and veneer layers of all-ceramics by switching the illuminating lights on the color shifts of layered ceramics. Specimens of seven kinds of core ceramics and the corresponding veneer ceramics for each core were fabricated with a layered thickness of 1.5 mm. A sintering ceramic was used as a reference core material. The Commission Internationale de l'Eclairage (CIE) color coordinates of core, veneer, and layered specimens were measured with a spectroradiometer under the CIE illuminant D65 (daylight), A (incandescent lamp), and F9 (fluorescent lamp) simulating lights. Color shifts of the layered specimens were primarily determined by the CIE a shifts (D65 to A switch) or by the CIE b shifts (D65 to F9 switch) of the veneer layer. The color coordinates shifts in the constituent layers differentially influenced those of the layered specimens by the kind of switched lights. Therefore, the optical properties of the constituent layers of all-ceramics should be controlled to reflect these findings.

Seeding cells on calcium phosphate scaffolds using hydrogel enhanced osteoblast proliferation and differentiation.

Internal pores in calcium phosphate (CaP) scaffolds pose an obstacle in cell seeding efficiency. Previous studies have shown inverse relationships between cell attachment and internal pore size, which mainly resulted from cells flowing to the bottom of culture plates. In order to overcome this structure-based setback, we have designed a method for cell seeding that involves hydrogel. CaP scaffolds fabricated with hydroxyapatite, biphasic calcium phosphate, and ß-tricalcium phosphate, had respective porosities of 77.0, 77.9, and 82.5% and pore diameters of 671.1, 694.7, and 842.8 µm. We seeded the cells on the scaffolds using two methods: the first using osteogenic medium and the second using hydrogel to entrap cells. As expected, cell seeding efficiency of the groups with hydrogel ranged from 92.5 to 96.3%, whereas efficiency of the control groups ranged only from 64.2 to 71.8%. Cell proliferation followed a similar trend, which may have further influenced early stages of cell differentiation. We suggest that our method of cell seeding with hydrogel can impact the field of tissue engineering even further with modifications of the materials or the addition of biological factors.

Acid neutralizing, mechanical and physical properties of pit and fissure sealants containing melt-derived 45S5 bioactive glass.

OBJECTIVES: The aim of this study was to examine the effects of 45S5 bioactive glass (BAG) on the acid neutralizing, mechanical and physical properties of pit and fissure sealants. METHODS: 45S5BAG (<25 µm) was mixed with the silanized glass (180 ± 30 nm) and added into a resin matrix [Bis-GMA/TEGDMA 50/50 (wt%) containing 1% of DMAEMA/CQ 2:1 (wt%)] with varying filler proportions; 0% 45S5BAG+50% glass (BAG0); 12.5% 45S5BAG+37.5% glass (BAG12.5); 25% 45S5BAG+25% glass (BAG25); 37.5% 45S5BAG+12.5% glass (BAG37.5); and 50% 45S5BAG+0% glass (BAG50). To evaluate the acid neutralizing properties, specimens were immersed in lactic acid solution (pH 4.0). Then, the change in pH and the time required to raise the pH from 4.0 to 5.5 were measured. In addition, flexural strength, water sorption and solubility were analyzed. RESULTS: The acid neutralizing properties of each group exhibited increasing pH values as more 45S5BAG was added, and the time required to raise the pH from 4.0 to 5.5 became shorter as the proportion of 45S5BAG increased (P<0.05). Additionally, the flexural strength decreased according to the increasing proportions of 45S5BAG added (P<0.05). Water sorption showed an increasing trend with increasing proportions of 45S5 BAG added (P<0.05). However, the solubility results were similar among the groups (P>0.05), except for BAG50. SIGNIFICANCE: The novel pit and fissure sealants neutralized the acid solution (pH 4.0) and exhibited appropriate mechanical and physical properties. Therefore, these compounds are suitable candidates for caries-inhibiting dental materials.

Perceived color shift of ceramics according to the change of illuminating light with spectroradiometer.

PURPOSE: Perceived color of ceramics changes by the spectral power distribution of ambient light. This study aimed to quantify the amount of shifts in color and color coordinates of clinically simulated seven all-ceramics due to the switch of three ambient light sources using a human vision simulating spectroradiometer. MATERIALS AND METHODS: CIE color coordinates, such as L*, a* and b*,of ceramic specimens were measured under three light sources, which simulate the CIE standard illuminant D65 (daylight), A (incandescent lamp), and F9 (fluorescent lamp). Shifts in color and color coordinate by the switch of lights were determined. Influence of the switched light (D65 to A, or D65 to F9), shade of veneer ceramics (A2 or A3), and brand of ceramics on the shifts was analyzed by a three-way ANOVA. RESULTS: Shifts in color and color coordinates were influenced by three factors (P<.05). Color shifts by the switch to A were in the range of 5.9 to 7.7 ΔE*ab units, and those by the switch to F9 were 7.7 to 10.2; all of which were unacceptable (ΔE*ab > 5.5). When switched to A, CIE a* increased (Δa*: 5.6 to 7.6), however, CIE b* increased (Δb*: 4.9 to 7.8) when switched to F9. CONCLUSION: Clinically simulated ceramics demonstrated clinically unacceptable color shifts according to the switches in ambient lights based on spectroradiometric readings. Therefore, shade matching and compatibility evaluation should be performed considering ambient lighting conditions and should be done under most relevant lighting condition.

Cytotoxicity test of dentin bonding agents using millipore filters as dentin substitutes in a dentin barrier test.

OBJECTIVES: The purpose of this study was to find proper dentin substitute for standardized dentin barrier test and perform the cytotoxicity test of commercial bonding agents with the proper substitute. MATERIALS AND METHODS: The three-dimensional cells attached to dentin disc or millipore filters as the dentin substitute were tested in a dentin barrier test by perfusion. MTT assay was performed as an evaluation method for the cell survival rate. The cytotoxicity test of serial phenol dilution by bovine dentin disc was done to determine a standard toxic material, and the test of this proper phenol by using various millipore combinations was performed to find the suitable dentin substitute. Also, the cytotoxicity test of bonding agents was performed by this standardized substitute. The cell viability was expressed as percentages of untreated group. RESULTS: Phenol concentration of 0.05 % was selected as the standard toxic material. The different combinations of millipore filters--two sheets of 0.45 µm, two sheets of 0.22 µm, and the combination of 0.65, 0.45, and 0.22 µm--showed similar cytotoxicity to natural dentin discs by 0.05 % phenol (p > 0.05). The millipore combination of 0.65, 0.45, and 0.22 µm that had structural similarity to natural dentin discs was used as the substitute for cytotoxicity test of bonding agents. The toxic level of Adper Prompt L-Pop using the selected substitute was significantly the highest among four kinds of dentin bonding agents (p < 0.05). Also, the dentin barrier test by the substitute showed constant results compared with the one by the natural dentin disc. CONCLUSIONS: The millipore filter combination of 0.65, 0.45, and 0.22 µm could be used as the substitute for the cytotoxicity test of materials applied to dentin. CLINICAL RELEVANCE: Dentin barrier test by standardized substitutes would be helpful for considering the potential toxicity of dentin bonding agents prior to clinical adaptations and reducing the variations of natural bovine dentin that has individually different characteristics.