Objective: To investigate the potential of resin coating materials in protection of enamel agains... more Objective: To investigate the potential of resin coating materials in protection of enamel against demineralization using nanoindentation. Methods: Forty-five blocks were prepared from buccal enamel of bovine incisors (6×3×3 mm) and embedded in epoxy resin. Five specimens were used as control and the rest were partially coated using a resin-based coating material in four groups (n = 10/group) as follow: (1) Shield Force Plus (SFP, Tokuyama Dental), (2): Clearfil SE Protect (SEP, Kuraray Noritake Dental), (3): PRG Barrier Coat (PBC, Shofu), (4): Vanish XT (VXT, 3M/ESPE). The specimens were subjected to water storage (37° C, 24 h) and thermal stress challenge (5000 cycles, 5 and 55 °C), and then exposed to demineralization for one week in an acidic solution (pH 4.5) at 37°C. The specimens were embedded, cut perpendicular to the coated surface and fine polished for nanoindentation. Hardness of enamel beneath the coat and adjacent area was measured using a Berkovich tip under 2 mN load ...
Objectives: To evaluate the marginal adaptation of different restorative materials in class-I cav... more Objectives: To evaluate the marginal adaptation of different restorative materials in class-I cavity using optical coherence tomography (OCT) and their microtensile bond-strength (MTBS). Methods: Round-shaped class-I cavities (3 mm diameter x 1.5 mm depth) were prepared in the occlusal surface of extracted human third-molars, with margins located in superficial dentin. Five adhesive systems were evaluated in this study; one two-step total-etch adhesive system (Adper Single Bond 2/ASB2), one two-step self-etch adhesive system (Clearfil SE Bond/SEB) and two one-step adhesives (G-Bond Plus/GBP, Clearfil S3 Bond Plus/TSP), restored a with composite resin (Clearfil Majesty Posterior) or a low-shrinkage composite with its proper adhesive (Filtek P90/P90, Silorane Adhesive System). After 24 h storage or 10,000 thermocycles in water, the specimens were immersed in ammoniacal silver nitrate solution to evaluate their marginal sealing ability. Cross-sectional 2D images of each material were o...
Objectives: The underlying dentin of attrited teeth is known as transparent (or sclerotic) dentin... more Objectives: The underlying dentin of attrited teeth is known as transparent (or sclerotic) dentin, where dentin tubules are occluded by mineral casts and the appearance of dentin is different from the sound dentin. This study aimed to evaluate the mechanical properties of the transparent dentin of attrited teeth using nanoindentation, and to evaluate the morphology by light microscopy. Methods: Naturally attrited extracted human teeth with occlusal transparent dentin were compared to sound dentin in this study. The teeth were imbedded in epoxy resin and a 2 mm-thick slice was obtained from each tooth. Fine polishing of the specimen was done under running water. Then, the specimens were imaged under light microscopy to see the depth of transparent dentin. After that, mechanical properties were obtained using nanoindentation system (ENT 1100a, Elionix). The indentations were set in the intertubular dentin from the surface up to 400 µm under 10 mN load. Transverse microradigraphy (TMR)...
Objective: Optical coherence tomography (OCT) can potentially monitor enamel subsurface lesions c... more Objective: Optical coherence tomography (OCT) can potentially monitor enamel subsurface lesions clinically. This study aimed to validate swept-source OCT findings with cross-sectional nanoindentation hardness and transverse microradiography (TMR). Method: Subsurface demineralized lesions were created in resin-embedded bovine enamel blocks by a two-layer method for 14 days at pH 4.6, and subjected to a remineralizing solution containing (100 mM KCl, 3.6 mM KH2PO4, 1.5 mM CaCl2, 20 mM HEPES) in the final concentration adjusted at pH 6.5 and stored up to 14 days. B-scans images were obtained at 1310nm center wavelength on three regions; sound, demineralized and remineralized (after 4, 7 and 14 days). The specimens were then cut through the regions and processed for cross-sectional nanoindentation and TMR. Result: Generally, reflectivity of enamel superficial zone increased with demineralization and decreased upon remineralization. The lesion extent was readily determined from the bound...
Objectives: Several resinous materials and filling techniques had been introduced to simplify the... more Objectives: Several resinous materials and filling techniques had been introduced to simplify the restorative procedure, improve the adaption as well as to overcome the drastic effect of polymerization shrinkage. Thus, the aim of this study is to assess the effect of lining with flowable composite on marginal adaptation in class-II restoration using swept-source optical coherence tomography (SS-OCT), and confirm the findings with confocal laser microscope (CLSM). Materials and Methods: Proximal box-shaped class-II cavities were prepared on twelve human third molar teeth. The specimens were divided into two groups and restored according to the manufacturer instruction using two types of one-step self-etch adhesives and two types of composite systems; Adper Easy Bond/Filtek Supreme Ultra flowable composite with Filtek Supreme Ultra universal composite (AF; 3M ESPE, USA) and Clearfil Tri-S Bond Plus/Majesty LV flowable composite with Majesty Posterior conventional hybrid composite rest...
Objective: The aim of this study was to investigate the durability of enamel coating materials an... more Objective: The aim of this study was to investigate the durability of enamel coating materials and their protective effects against subsurface demineralization using Optical Coherence Tomography (OCT). Method: Epoxy resin-embedded bovine tooth blocks were assigned to four different groups (n = 8), in which enamel surface was partly covered by a resin-based coating material: (1) Shield Force Plus (Tokuyama Dental), (2): Clearfil SE Protect (Kuraray Noritake Dental), (3): PRG Barrier Coat (Shofu), (4): Vanish XT (3M/ESPE). Swept Source OCT at 1319nm-wavelength (Prototype2, Panasonic Health Care) was used to obtain cross-sectional images of the coated enamel before and after 1000 thermal cycles (5-55C), to confirm the durability of each coating after aging. Then the specimens were subjected to OCT imaging after acid challenge for 1, 7 and 14 days in a demineralization solution (pH 4.5) at 37C, with the uncoated enamel surface serving as control. Result: Coating layer film thickness dif...
Objectives: Introduction of focused ion beam (FIB) for transmission electron microscopy (TEM) pre... more Objectives: Introduction of focused ion beam (FIB) for transmission electron microscopy (TEM) preparation may contribute to the understanding of biomaterial-tooth interaction at the nanoscale under clinically relevant cavity setups. The aims of this study were to evaluate the interface of two different self-etching adhesives in a class-I cavity using FIB-TEM technique. Methods: Cylindrical dentin cavities (3 x 1.5 mm) were prepared using diamond bur on the occlusal surfaces of extracted human premolar teeth and restored with one of two adhesive/composite systems; Filtek Silorane adhesive/composite system (SB; 3M ESPE, USA) and Clearfil Protect Bond adhesive (PB; Kuraray Medical, Japan)/Estelite Sigma Quick composite (Tokuyama Dental, Japan). To investigate the ultramorphology of resin-dentin interfacial area; non-demineralized and non-stained ultra-thin sections were obtained using the FIB technique and examined under TEM. Results: The obtained sections by FIB-TEM for SB group allow...
Objective: The aim of this study was to determine the effects of cryogenic cooling on the morphol... more Objective: The aim of this study was to determine the effects of cryogenic cooling on the morphological features of the dentin interfaces with dental restorative materials in samples prepared by Focused Ion Beam (FIB) for transmission electron microscope (TEM) examination. Methods: After preparation of cylindrical-shaped cavities in human extracted premolar teeth, the specimens were restored with dental adhesive/composite and grouped in to; (PB) a combination of Clearfil Protect Bond (Kuraray Noritake, Japan)/Estelite Sigma Quick composite (Tokuyama Dental, Japan), and (SB) Filtek Silorane adhesive/composite restorative system (3M ESPE, USA). Then, the specimens were subjected to interfacial cross-sectioning followed by observation and area selection using confocal laser microscopy. Later, ultrathin sections were prepared using FIB with cryogenic cooling and (PB-C) and (SB-C), or without it (PB-NC) and (SB-NC). The sections were subjected to TEM observation and under different magni...
Dental materials : official publication of the Academy of Dental Materials, 2015
The introduction of focused ion beam (FIB) milling has facilitated preparation of hard tissue sam... more The introduction of focused ion beam (FIB) milling has facilitated preparation of hard tissue samples for transmission electron microscope (TEM). However, this technique generates high temperature that may alter or damage morphological features in biological tissue. Therefore, the aim of this study was to determine the effects of cryogenic cooling on the morphological features of dentin interfaces with dental restorative materials in samples prepared by FIB for TEM examination. After preparation of a cylindrical-shaped cavities in extracted, non-carious premolar teeth, the specimens were restored with dental adhesive/composite and categorized into two restorative materials groups; (PB) a combination of Clearfil Protect Bond (Kuraray Noritake Dental, Japan)/Estelite Sigma Quick composite (Tokuyama Dental, Japan), and (SB) Filtek Silorane restorative system (3M ESPE, USA). The specimens were subjected to interfacial cross-sectioning, followed by observation and area selection using co...
Objectives: The aim of this study was to use swept-source optical coherence tomography (SS-OCT) f... more Objectives: The aim of this study was to use swept-source optical coherence tomography (SS-OCT) for real-time tomographic assessment of tooth/restoration complex during placement of resin composite. Methods: An SS-OCT system with a laser center wavelength of 1310nm was used to record tomographic images and videos during bulk placement and light-polymerization of four combinations of composite/adhesive materials; two low-shrinkage composites (Filtek Silorane/Adhesive and Kalore/SE Bond), and one conventional hybrid composite with either a two-step self etch or an all-in-one adhesive system (APX/SE Bond and APX/S3 Bond). The composites were bulk filled into 1.7-mm-deep standard class I dentin cavities. The movies were used to monitor the placement and polymerization procedures up to 2min after photo-activation. Single fine shots were analyzed to quantify the interfacial gap resulting from polymerization shrinkage, dimensional contraction, and structural voids in a central cross sectio...
This study assessed dentin-resin interface integration in Class I cavities restored with simplifi... more This study assessed dentin-resin interface integration in Class I cavities restored with simplified adhesives by using a focused ion-beam milling (FIB) and transmission electron microscope (TEM). Class I cavities (1.5-mm depth with dentin thickness of ∼0.5 mm, 4-mm length, and 2-mm width) were prepared on freshly extracted, sound human molars. Two all-in-one adhesive systems (Scotchbond/Single Bond Universal [SUD] and Xeno-V(+) [X5D]) were used and compared with a two-step etch-and-rinse system (Prime&Bond NT [NTD]). The adhesives were applied according to the manufacturers' guidelines. A universal resin composite (Filtek Z350 XT Universal) was used to restore the cavities in one bulk filling and was irradiated at 550 mW/cm(2) for 40 seconds by a quartz-tungsten-halogen light (Optilux 501). After exposure to liquid nitrogen coolant, the specimens were milled to nanoscale thickness by FIB to view and then assess the area of dentin-resin interface by TEM. Unlike the unfilled X5D, ...
ABSTRACT Objectives: Dental hard tissues and biomaterials can be non-destructively assessed using... more ABSTRACT Objectives: Dental hard tissues and biomaterials can be non-destructively assessed using optical coherence tomography (OCT), an emerging diagnostic tool. Swept Source (SS)-OCT has an improved imaging resolution and speed. Depth resolved data obtained in B-scans can be used to assess the quality and depth-resolved information on the tissues. The measurements are affected by the optical properties of the tissue, such as refractive index (RI). The aim of this study was to examine the effects of demineralization on the refractive index of enamel and dentin using SS-OCT. Methods: In the first experiment, slices cut from human sound molars approximately 300 microns in thickness, were imaged at the baseline and after demineralization in solutions at pH value of 4.5 for 1, 3, 7 and 15 days by SS-OCT (Santec, Japan). RI of each tissue was calculated as the optical path length divided by the real thickness. The extent of demineralization at each time was confirmed by nanoindentation hardness(ENT-1100a, Elionix, Japan). In the second experiment, we attempted to calculate the refractive index of enamel from the slope of a linear correlation between OCT depth of 15-day demineralized lesions on 2mm-thick enamel disks, and real depths of the lesions as confirmed by nanoindentation. Results: Refractive indexes calculated at the base-line for enamel and dentin were 1.62 and 1.56, respectively. These values gradually decreased in time and at 15 days, significant reduction was observed for both tissues. (p<0.05). Interestingly, RI values determined for enamel 15-day demineralization from the two experiments were consistent. Conclusions: For an accurate assessment of demineralized and carious lesions depth using OCT, an appropriate refractive index will be required. The loss of refractive index depends on the extent of demineralization, and conversely, may serve as a demineralization indicator. Supported by the Global Center of Excellence at Tokyo Medical and Dental University.
ABSTRACT Objectives: Composite restorations suffer from polymerization shrinkage upon curing, whi... more ABSTRACT Objectives: Composite restorations suffer from polymerization shrinkage upon curing, which leads to gap formation at the tooth-restoration interface. These gaps might weaken the restoration integrity and vary in size. The aim of this study is to assess the tooth-restoration interface using swept source optical coherence tomography (SS-OCT) and to compare the findings with confocal laser scanning microscope (CLSM). Methods: Round class-I cavities 3mm in diameter and 1.5mm in depth were prepared on 16 human premolars. After application of Clearfil Tri-S bond, four types of composite restoration were tested; Flow FX, Majesty Posterior, Clearfil AP-X and Majesty LV (all by Kuraray Medical, Tokyo, Japan). Three B-scan cross-sectional images where obtained by SS-OCT (Santec, Tokyo, Japan) for each specimen, at which the specimens were later cut and observed under CLSM (Lasertec Co., Yokohama, Japan). An image analysis software was used to detect significant peaks in the signal intensity at the resin-dentin interface of the cavity floor. The presence and dimensions of gaps at the interface were also confirmed by CLSM. Results: B-scan images showed increased reflectivity along the interface at some areas, which corresponded well to the interfacial gaps detected by CLSM. Also, defects such as voids or trapped air were clearly observed. The actual gap size detected under CLSM ranged from 1 to 10 micrometers, which under SS-OCT were detected and masked, following threshold parameters determined for each composite with different optical properties (figure). Conclusion: SS-OCT imaging technology can be used to detect and quantify gaps as small as 1 micrometers sizes at the bottom of composite restorations, due to refractive contrast between resin, air and dental structure. Acknowledgment: This research is supported by research grant for longevity sciences (21A-8) from Ministry of Health, labour and Welfare, and Global Center of Excellence Program at Tokyo Medical and Dental University.
This study investigated class-I cavity floor adaptation by swept-source optical coherence tomogra... more This study investigated class-I cavity floor adaptation by swept-source optical coherence tomography (OCT) in combination with microtensile bond strength (MTBS) using different filling methods. Two adhesive systems; Tokuyama Bond Force and Tri-S Bond Plus were used in conjunction with a universal composite (Estelite Sigma Quick) placed either incrementally (oblique) or in bulk with or without a flowable composite lining (Palfique Estelite LV). Ten serial B-scan images were obtained throughout each cavity by OCT (center wavelength: 1319nm). In order to evaluate adaptation defined as the cavity floor percentage showing no gap, a significant increase in the signal intensity was considered as gap at the bonded interface of the cavity floor. The same specimens were then cut into beams to measure MTBS at the cavity floor. Two-way ANOVA demonstrated that the interaction of adhesive systems and filling techniques was significantly affecting both adaptation and MTBS (p<0.05). There was a significant correlation between MTBS and adaptation at cavity floor (p<0.05). Cavity floor adaptation and MTBS were improved when incremental filling technique was applied, while the outcome of lining technique was variable. Quantitative assessment by OCT can non-destructively provide information on the performance and effectiveness of dental composites and restoration techniques. There was a moderate correlation between floor adaptation and bond strength in class-I cavities. Incremental application of composite restoration showed the best performance in terms of bond strength and internal adaptation. Incremental application of composite restoration was the most advantageous placement technique in terms of bond strength and internal adaptation. The lack of placement pressure with flowable composites may affect their adaptation to all-in-one adhesives; therefore, the outcome of cavity lining by flowable composite was variable.
ABSTRACT This study evaluated the enamel–resin interface of three adhesive resins (ARs) by a tran... more ABSTRACT This study evaluated the enamel–resin interface of three adhesive resins (ARs) by a transmission electron microscope (TEM) after milling with focused ion beam (FIB). Simple Class-I cavities (0.5 mm within enamel depth, 4 mm length, and 2 mm width) were prepared on human caries-free molars. The enamel of two groups was conditioned by one-step self-etch bonding system (Scotchbond™/Single Bond Universal [SBU], and Xeno V®+ [XV+]), while the enamel of the third group was etched by phosphoric acid, and then treated by two-step self-priming etch-rinse system (Prime&Bond® NT [PBNT]). The application of the adhesive systems was carried out according to their respective manufacturer’s instructions. The cavities were restored by a nanofill resin composite (Filtek™ Z350 XT Universal; 3 M ESPE) in one bulk-fill, and cured for 40 s at 550 mW/cm2 by a halogen light (Optilux 501, Demetron/Kerr, Danbury, USA). The specimens were milled by FIB into 100 nm thickness slices, and then observed under TEM. The transmission electron micrographs showed an adequate adhesion of both two-step etch-rinse (PBNT) and one-step self-etch (SBU) to enamel surface. The deeply etched enamel prisms were impregnated by the etch-rinse PBNT adhesive. A relatively inadequate adhesion associated with some areas of bond degradation underneath the hybrid layer and within the adhesive was noted for the XV+ AR. Apart from the mild acidic adhesives of one-step self-etch and two-step etch-rinse investigated, the highly hydrophilic and acidic water-based one-step self-etch adhesive (XV+) proved to be less effective enamel bond by ultra-structural characterization technique using FIB-TEM.
Objective: To investigate the potential of resin coating materials in protection of enamel agains... more Objective: To investigate the potential of resin coating materials in protection of enamel against demineralization using nanoindentation. Methods: Forty-five blocks were prepared from buccal enamel of bovine incisors (6×3×3 mm) and embedded in epoxy resin. Five specimens were used as control and the rest were partially coated using a resin-based coating material in four groups (n = 10/group) as follow: (1) Shield Force Plus (SFP, Tokuyama Dental), (2): Clearfil SE Protect (SEP, Kuraray Noritake Dental), (3): PRG Barrier Coat (PBC, Shofu), (4): Vanish XT (VXT, 3M/ESPE). The specimens were subjected to water storage (37° C, 24 h) and thermal stress challenge (5000 cycles, 5 and 55 °C), and then exposed to demineralization for one week in an acidic solution (pH 4.5) at 37°C. The specimens were embedded, cut perpendicular to the coated surface and fine polished for nanoindentation. Hardness of enamel beneath the coat and adjacent area was measured using a Berkovich tip under 2 mN load ...
Objectives: To evaluate the marginal adaptation of different restorative materials in class-I cav... more Objectives: To evaluate the marginal adaptation of different restorative materials in class-I cavity using optical coherence tomography (OCT) and their microtensile bond-strength (MTBS). Methods: Round-shaped class-I cavities (3 mm diameter x 1.5 mm depth) were prepared in the occlusal surface of extracted human third-molars, with margins located in superficial dentin. Five adhesive systems were evaluated in this study; one two-step total-etch adhesive system (Adper Single Bond 2/ASB2), one two-step self-etch adhesive system (Clearfil SE Bond/SEB) and two one-step adhesives (G-Bond Plus/GBP, Clearfil S3 Bond Plus/TSP), restored a with composite resin (Clearfil Majesty Posterior) or a low-shrinkage composite with its proper adhesive (Filtek P90/P90, Silorane Adhesive System). After 24 h storage or 10,000 thermocycles in water, the specimens were immersed in ammoniacal silver nitrate solution to evaluate their marginal sealing ability. Cross-sectional 2D images of each material were o...
Objectives: The underlying dentin of attrited teeth is known as transparent (or sclerotic) dentin... more Objectives: The underlying dentin of attrited teeth is known as transparent (or sclerotic) dentin, where dentin tubules are occluded by mineral casts and the appearance of dentin is different from the sound dentin. This study aimed to evaluate the mechanical properties of the transparent dentin of attrited teeth using nanoindentation, and to evaluate the morphology by light microscopy. Methods: Naturally attrited extracted human teeth with occlusal transparent dentin were compared to sound dentin in this study. The teeth were imbedded in epoxy resin and a 2 mm-thick slice was obtained from each tooth. Fine polishing of the specimen was done under running water. Then, the specimens were imaged under light microscopy to see the depth of transparent dentin. After that, mechanical properties were obtained using nanoindentation system (ENT 1100a, Elionix). The indentations were set in the intertubular dentin from the surface up to 400 µm under 10 mN load. Transverse microradigraphy (TMR)...
Objective: Optical coherence tomography (OCT) can potentially monitor enamel subsurface lesions c... more Objective: Optical coherence tomography (OCT) can potentially monitor enamel subsurface lesions clinically. This study aimed to validate swept-source OCT findings with cross-sectional nanoindentation hardness and transverse microradiography (TMR). Method: Subsurface demineralized lesions were created in resin-embedded bovine enamel blocks by a two-layer method for 14 days at pH 4.6, and subjected to a remineralizing solution containing (100 mM KCl, 3.6 mM KH2PO4, 1.5 mM CaCl2, 20 mM HEPES) in the final concentration adjusted at pH 6.5 and stored up to 14 days. B-scans images were obtained at 1310nm center wavelength on three regions; sound, demineralized and remineralized (after 4, 7 and 14 days). The specimens were then cut through the regions and processed for cross-sectional nanoindentation and TMR. Result: Generally, reflectivity of enamel superficial zone increased with demineralization and decreased upon remineralization. The lesion extent was readily determined from the bound...
Objectives: Several resinous materials and filling techniques had been introduced to simplify the... more Objectives: Several resinous materials and filling techniques had been introduced to simplify the restorative procedure, improve the adaption as well as to overcome the drastic effect of polymerization shrinkage. Thus, the aim of this study is to assess the effect of lining with flowable composite on marginal adaptation in class-II restoration using swept-source optical coherence tomography (SS-OCT), and confirm the findings with confocal laser microscope (CLSM). Materials and Methods: Proximal box-shaped class-II cavities were prepared on twelve human third molar teeth. The specimens were divided into two groups and restored according to the manufacturer instruction using two types of one-step self-etch adhesives and two types of composite systems; Adper Easy Bond/Filtek Supreme Ultra flowable composite with Filtek Supreme Ultra universal composite (AF; 3M ESPE, USA) and Clearfil Tri-S Bond Plus/Majesty LV flowable composite with Majesty Posterior conventional hybrid composite rest...
Objective: The aim of this study was to investigate the durability of enamel coating materials an... more Objective: The aim of this study was to investigate the durability of enamel coating materials and their protective effects against subsurface demineralization using Optical Coherence Tomography (OCT). Method: Epoxy resin-embedded bovine tooth blocks were assigned to four different groups (n = 8), in which enamel surface was partly covered by a resin-based coating material: (1) Shield Force Plus (Tokuyama Dental), (2): Clearfil SE Protect (Kuraray Noritake Dental), (3): PRG Barrier Coat (Shofu), (4): Vanish XT (3M/ESPE). Swept Source OCT at 1319nm-wavelength (Prototype2, Panasonic Health Care) was used to obtain cross-sectional images of the coated enamel before and after 1000 thermal cycles (5-55C), to confirm the durability of each coating after aging. Then the specimens were subjected to OCT imaging after acid challenge for 1, 7 and 14 days in a demineralization solution (pH 4.5) at 37C, with the uncoated enamel surface serving as control. Result: Coating layer film thickness dif...
Objectives: Introduction of focused ion beam (FIB) for transmission electron microscopy (TEM) pre... more Objectives: Introduction of focused ion beam (FIB) for transmission electron microscopy (TEM) preparation may contribute to the understanding of biomaterial-tooth interaction at the nanoscale under clinically relevant cavity setups. The aims of this study were to evaluate the interface of two different self-etching adhesives in a class-I cavity using FIB-TEM technique. Methods: Cylindrical dentin cavities (3 x 1.5 mm) were prepared using diamond bur on the occlusal surfaces of extracted human premolar teeth and restored with one of two adhesive/composite systems; Filtek Silorane adhesive/composite system (SB; 3M ESPE, USA) and Clearfil Protect Bond adhesive (PB; Kuraray Medical, Japan)/Estelite Sigma Quick composite (Tokuyama Dental, Japan). To investigate the ultramorphology of resin-dentin interfacial area; non-demineralized and non-stained ultra-thin sections were obtained using the FIB technique and examined under TEM. Results: The obtained sections by FIB-TEM for SB group allow...
Objective: The aim of this study was to determine the effects of cryogenic cooling on the morphol... more Objective: The aim of this study was to determine the effects of cryogenic cooling on the morphological features of the dentin interfaces with dental restorative materials in samples prepared by Focused Ion Beam (FIB) for transmission electron microscope (TEM) examination. Methods: After preparation of cylindrical-shaped cavities in human extracted premolar teeth, the specimens were restored with dental adhesive/composite and grouped in to; (PB) a combination of Clearfil Protect Bond (Kuraray Noritake, Japan)/Estelite Sigma Quick composite (Tokuyama Dental, Japan), and (SB) Filtek Silorane adhesive/composite restorative system (3M ESPE, USA). Then, the specimens were subjected to interfacial cross-sectioning followed by observation and area selection using confocal laser microscopy. Later, ultrathin sections were prepared using FIB with cryogenic cooling and (PB-C) and (SB-C), or without it (PB-NC) and (SB-NC). The sections were subjected to TEM observation and under different magni...
Dental materials : official publication of the Academy of Dental Materials, 2015
The introduction of focused ion beam (FIB) milling has facilitated preparation of hard tissue sam... more The introduction of focused ion beam (FIB) milling has facilitated preparation of hard tissue samples for transmission electron microscope (TEM). However, this technique generates high temperature that may alter or damage morphological features in biological tissue. Therefore, the aim of this study was to determine the effects of cryogenic cooling on the morphological features of dentin interfaces with dental restorative materials in samples prepared by FIB for TEM examination. After preparation of a cylindrical-shaped cavities in extracted, non-carious premolar teeth, the specimens were restored with dental adhesive/composite and categorized into two restorative materials groups; (PB) a combination of Clearfil Protect Bond (Kuraray Noritake Dental, Japan)/Estelite Sigma Quick composite (Tokuyama Dental, Japan), and (SB) Filtek Silorane restorative system (3M ESPE, USA). The specimens were subjected to interfacial cross-sectioning, followed by observation and area selection using co...
Objectives: The aim of this study was to use swept-source optical coherence tomography (SS-OCT) f... more Objectives: The aim of this study was to use swept-source optical coherence tomography (SS-OCT) for real-time tomographic assessment of tooth/restoration complex during placement of resin composite. Methods: An SS-OCT system with a laser center wavelength of 1310nm was used to record tomographic images and videos during bulk placement and light-polymerization of four combinations of composite/adhesive materials; two low-shrinkage composites (Filtek Silorane/Adhesive and Kalore/SE Bond), and one conventional hybrid composite with either a two-step self etch or an all-in-one adhesive system (APX/SE Bond and APX/S3 Bond). The composites were bulk filled into 1.7-mm-deep standard class I dentin cavities. The movies were used to monitor the placement and polymerization procedures up to 2min after photo-activation. Single fine shots were analyzed to quantify the interfacial gap resulting from polymerization shrinkage, dimensional contraction, and structural voids in a central cross sectio...
This study assessed dentin-resin interface integration in Class I cavities restored with simplifi... more This study assessed dentin-resin interface integration in Class I cavities restored with simplified adhesives by using a focused ion-beam milling (FIB) and transmission electron microscope (TEM). Class I cavities (1.5-mm depth with dentin thickness of ∼0.5 mm, 4-mm length, and 2-mm width) were prepared on freshly extracted, sound human molars. Two all-in-one adhesive systems (Scotchbond/Single Bond Universal [SUD] and Xeno-V(+) [X5D]) were used and compared with a two-step etch-and-rinse system (Prime&Bond NT [NTD]). The adhesives were applied according to the manufacturers' guidelines. A universal resin composite (Filtek Z350 XT Universal) was used to restore the cavities in one bulk filling and was irradiated at 550 mW/cm(2) for 40 seconds by a quartz-tungsten-halogen light (Optilux 501). After exposure to liquid nitrogen coolant, the specimens were milled to nanoscale thickness by FIB to view and then assess the area of dentin-resin interface by TEM. Unlike the unfilled X5D, ...
ABSTRACT Objectives: Dental hard tissues and biomaterials can be non-destructively assessed using... more ABSTRACT Objectives: Dental hard tissues and biomaterials can be non-destructively assessed using optical coherence tomography (OCT), an emerging diagnostic tool. Swept Source (SS)-OCT has an improved imaging resolution and speed. Depth resolved data obtained in B-scans can be used to assess the quality and depth-resolved information on the tissues. The measurements are affected by the optical properties of the tissue, such as refractive index (RI). The aim of this study was to examine the effects of demineralization on the refractive index of enamel and dentin using SS-OCT. Methods: In the first experiment, slices cut from human sound molars approximately 300 microns in thickness, were imaged at the baseline and after demineralization in solutions at pH value of 4.5 for 1, 3, 7 and 15 days by SS-OCT (Santec, Japan). RI of each tissue was calculated as the optical path length divided by the real thickness. The extent of demineralization at each time was confirmed by nanoindentation hardness(ENT-1100a, Elionix, Japan). In the second experiment, we attempted to calculate the refractive index of enamel from the slope of a linear correlation between OCT depth of 15-day demineralized lesions on 2mm-thick enamel disks, and real depths of the lesions as confirmed by nanoindentation. Results: Refractive indexes calculated at the base-line for enamel and dentin were 1.62 and 1.56, respectively. These values gradually decreased in time and at 15 days, significant reduction was observed for both tissues. (p<0.05). Interestingly, RI values determined for enamel 15-day demineralization from the two experiments were consistent. Conclusions: For an accurate assessment of demineralized and carious lesions depth using OCT, an appropriate refractive index will be required. The loss of refractive index depends on the extent of demineralization, and conversely, may serve as a demineralization indicator. Supported by the Global Center of Excellence at Tokyo Medical and Dental University.
ABSTRACT Objectives: Composite restorations suffer from polymerization shrinkage upon curing, whi... more ABSTRACT Objectives: Composite restorations suffer from polymerization shrinkage upon curing, which leads to gap formation at the tooth-restoration interface. These gaps might weaken the restoration integrity and vary in size. The aim of this study is to assess the tooth-restoration interface using swept source optical coherence tomography (SS-OCT) and to compare the findings with confocal laser scanning microscope (CLSM). Methods: Round class-I cavities 3mm in diameter and 1.5mm in depth were prepared on 16 human premolars. After application of Clearfil Tri-S bond, four types of composite restoration were tested; Flow FX, Majesty Posterior, Clearfil AP-X and Majesty LV (all by Kuraray Medical, Tokyo, Japan). Three B-scan cross-sectional images where obtained by SS-OCT (Santec, Tokyo, Japan) for each specimen, at which the specimens were later cut and observed under CLSM (Lasertec Co., Yokohama, Japan). An image analysis software was used to detect significant peaks in the signal intensity at the resin-dentin interface of the cavity floor. The presence and dimensions of gaps at the interface were also confirmed by CLSM. Results: B-scan images showed increased reflectivity along the interface at some areas, which corresponded well to the interfacial gaps detected by CLSM. Also, defects such as voids or trapped air were clearly observed. The actual gap size detected under CLSM ranged from 1 to 10 micrometers, which under SS-OCT were detected and masked, following threshold parameters determined for each composite with different optical properties (figure). Conclusion: SS-OCT imaging technology can be used to detect and quantify gaps as small as 1 micrometers sizes at the bottom of composite restorations, due to refractive contrast between resin, air and dental structure. Acknowledgment: This research is supported by research grant for longevity sciences (21A-8) from Ministry of Health, labour and Welfare, and Global Center of Excellence Program at Tokyo Medical and Dental University.
This study investigated class-I cavity floor adaptation by swept-source optical coherence tomogra... more This study investigated class-I cavity floor adaptation by swept-source optical coherence tomography (OCT) in combination with microtensile bond strength (MTBS) using different filling methods. Two adhesive systems; Tokuyama Bond Force and Tri-S Bond Plus were used in conjunction with a universal composite (Estelite Sigma Quick) placed either incrementally (oblique) or in bulk with or without a flowable composite lining (Palfique Estelite LV). Ten serial B-scan images were obtained throughout each cavity by OCT (center wavelength: 1319nm). In order to evaluate adaptation defined as the cavity floor percentage showing no gap, a significant increase in the signal intensity was considered as gap at the bonded interface of the cavity floor. The same specimens were then cut into beams to measure MTBS at the cavity floor. Two-way ANOVA demonstrated that the interaction of adhesive systems and filling techniques was significantly affecting both adaptation and MTBS (p<0.05). There was a significant correlation between MTBS and adaptation at cavity floor (p<0.05). Cavity floor adaptation and MTBS were improved when incremental filling technique was applied, while the outcome of lining technique was variable. Quantitative assessment by OCT can non-destructively provide information on the performance and effectiveness of dental composites and restoration techniques. There was a moderate correlation between floor adaptation and bond strength in class-I cavities. Incremental application of composite restoration showed the best performance in terms of bond strength and internal adaptation. Incremental application of composite restoration was the most advantageous placement technique in terms of bond strength and internal adaptation. The lack of placement pressure with flowable composites may affect their adaptation to all-in-one adhesives; therefore, the outcome of cavity lining by flowable composite was variable.
ABSTRACT This study evaluated the enamel–resin interface of three adhesive resins (ARs) by a tran... more ABSTRACT This study evaluated the enamel–resin interface of three adhesive resins (ARs) by a transmission electron microscope (TEM) after milling with focused ion beam (FIB). Simple Class-I cavities (0.5 mm within enamel depth, 4 mm length, and 2 mm width) were prepared on human caries-free molars. The enamel of two groups was conditioned by one-step self-etch bonding system (Scotchbond™/Single Bond Universal [SBU], and Xeno V®+ [XV+]), while the enamel of the third group was etched by phosphoric acid, and then treated by two-step self-priming etch-rinse system (Prime&Bond® NT [PBNT]). The application of the adhesive systems was carried out according to their respective manufacturer’s instructions. The cavities were restored by a nanofill resin composite (Filtek™ Z350 XT Universal; 3 M ESPE) in one bulk-fill, and cured for 40 s at 550 mW/cm2 by a halogen light (Optilux 501, Demetron/Kerr, Danbury, USA). The specimens were milled by FIB into 100 nm thickness slices, and then observed under TEM. The transmission electron micrographs showed an adequate adhesion of both two-step etch-rinse (PBNT) and one-step self-etch (SBU) to enamel surface. The deeply etched enamel prisms were impregnated by the etch-rinse PBNT adhesive. A relatively inadequate adhesion associated with some areas of bond degradation underneath the hybrid layer and within the adhesive was noted for the XV+ AR. Apart from the mild acidic adhesives of one-step self-etch and two-step etch-rinse investigated, the highly hydrophilic and acidic water-based one-step self-etch adhesive (XV+) proved to be less effective enamel bond by ultra-structural characterization technique using FIB-TEM.
Uploads