Clinical Relevance New dual-cure bulk-fill composites show promise for uniform degree of conversion and microhardness throughout the entire depth of direct restorations. SUMMARY Objective: The aim of this study was to evaluate the degree of conversion (DC) through micro-Raman spectroscopy and surface microhardness in Vickers hardness (VHN) of three new dual-cure bulk-fill resin-based composites (RBCs) compared with light-cure bulk-fill and incremental RBCs at two clinically relevant depths and for two light irradiation times. Methods: Three commercially available restorative dual-cure bulk-fill RBCs (BulkEZ, HyperFIL, and Injectafil) were evaluated and compared with three light-cure RBCs (Filtek Bulk Fill Flowable, Filtek One Bulk Fill, and incremental Filtek Z250) as controls. Specimens were prepared in two different depths (0.5 mm and 5 mm) and were light irradiated for 20 seconds or 40 seconds. Self-cure was also evaluated for the three dual-cure bulk-fill RBCs. Micro-Raman spectroscopic measurements and VHN tests (n=5) were made after 24 hours of dry storage in the dark at room temperature for all test conditions. Data were analyzed using one-way and two-way analyses of variance (α=0.05). Results: All tested RBCs showed significantly higher DC and VHN values at 0.5-mm depth than at 5-mm depth, with the exception of BulkEZ, which showed similar DC and VHN values at two depths. The three dual-cure bulk-fill RBCs showed significantly higher DC than the three light-cure RBCs under the same curing condition. The three dual-cure RBCs showed much smaller differences in VHN values between the two depths than the three light-cure RBCs. Twenty seconds and 40 seconds of light irradiation did not generate significant difference in DC and VHN values for the three dual-cure bulk-fill RBCs at either depth or for the three light-cure RBCs at the 0.5-mm depth; however, 40 seconds of light irradiation generated significantly higher DC and VHN values for One Bulk Fill and Z250 at the 5-mm depth compared with 20 seconds of light irradiation.

SUMMARY Purpose: To investigate the effect of neodymium-doped yttrium aluminum garnet (Nd:YAG) laser irradiation pretreatment on the long-term bond strength of an etch-and-rinse adhesive to dentin. Methods: Fifty molars were sectioned parallel to the occlusal plane and randomly divided into two groups (n=25 per group): control group (no treatment) and laser group (dentin surfaces were treated with Nd:YAG laser at a setting of 100 mJ/10 Hz). Afterward, resin was bonded to the dentin surface using a two-step etch-and-rinse adhesive (Adper SingleBond 2), and then 150 beams of each group were produced. Each group was divided into three subgroups (n=50 each group): 24 hours of water storage, thermocycling, and NaOCl storage. The microtensile bond strength (MTBS), failure modes, nanoleakage expression, and Masson's trichrome staining were evaluated. An additional 20 molars were sectioned to obtain 2-mm-thick flat dentin slices. These slices were randomly divided into control and laser-treated groups as mentioned previously. Then slices of each group were examined by scanning electron microscopy, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), and the Knoop hardness test. Results: The results of ATR-FTIR and Masson's trichrome verified that laser irradiation partly removed collagen fibers from the dentin surface; however, no significant difference was found in the Knoop hardness ( p >0.05). The XRD result showed similar crystalline structure regardless of laser pretreatment. There is no significant difference in short-term MTBS between control and laser-treated groups ( p >0.05); however, long-term MTBS differed between the groups ( p >0.05). Furthermore, the laser-treated group showed less silver deposition than the control group after aging ( p <0.05). Conclusion: Pretreatment by Nd:YAG laser irradiation appeared to have a positive effect on the adhesive-dentin bonding in vitro test, and the bonding effectiveness could be preserved after aging.

SUMMARY Objective: This study aimed to explore the chemical changes and discoloration of endodontically treated teeth using spectroradiometric and chemical analyses. Methods and Materials: Ten freshly extracted sound third molars and 10 discolored molars obtained after root canal treatment (RCT) were included in this study. Dentin blocks (3 × 3 × 1 mm) were prepared and treated with an intracoronal bleaching agent. Spectroradiometric evaluations, X-ray photoelectron spectroscopy (XPS), and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analyses were performed before and after bleaching. The spectroradiometric parameters and XPS and ATR-FTIR spectra of the dentin slabs were analyzed using independent-sample t -tests or one-way analysis of variance. Results: Differences in color coordinates and translucency parameters were observed between the two groups before bleaching. Demineralization effects were also detected in the discolored dentin. No binding energy shifts or new spectral bands were found in the XPS and ATR-FTIR spectra, except in the narrow-scanned XPS spectra of C 1s . Significant changes in color coordinates were also found in both groups after bleaching, and the translucency parameter was remarkably altered in discolored dentin. The organic and inorganic components of dentin also decreased in both groups. However, binding energy shifts (ie, C 1s , Ca 2p , and P 2p ) were detected only in discolored dentin. Conclusion: Significant alterations in the organic and inorganic components of dentin contributed to the discoloration of endodontically treated teeth. Moreover, intracoronal bleaching could effectively whiten both discolored and vital dentin. The chemical compositions of mineral and organic components within discolored dentin are more sensitive to the acid bleaching agent than normal teeth.

SUMMARY This study aims to evaluate the effects of pulsed Nd:YAG laser on the tensile bond strength (TBS) of resin to human enamel and caries resistance of human enamel. A total of 201 human premolars were used in this in vitro study. A flat enamel surface greater than 4 × 4 mm in area was prepared on each specimen using a low-speed cutting machine under a water coolant. Twenty-one specimens were divided into seven groups for morphology observations with no treatment, 35% phosphoric acid etching (30 seconds), and laser irradiation (30 seconds) of pulsed Nd:YAG laser with five different laser-parameter combinations. Another 100 specimens were used for TBS testing. They were embedded in self-cured acrylic resin and randomly divided into 10 groups. After enamel surface pretreatments according to the group design, resin was applied. The TBS values were tested using a universal testing machine. The other 80 specimens were randomly divided into eight groups for acid resistance evaluation. Scanning electron microscope (SEM) results showed that the enamel surfaces treated with 1.5 W/20 Hz and 2.0 W/20 Hz showed more etching-like appearance than those with other laser-parameter combinations. The laser-parameter combinations of 1.5 W/15 Hz and 1.5 W/20 Hz were found to be efficient for the TBS test. The mean TBS value of 14.45 ± 1.67 MPa in the laser irradiated group was significantly higher than that in the untreated group (3.48 ± 0.35 MPa) but lower than that in the 35% phosphoric acid group (21.50 ± 3.02 MPa). The highest mean TBS value of 26.64 ± 5.22 MPa was identified in the combination group (laser irradiation and then acid etching). Acid resistance evaluation showed that the pulsed Nd:YAG laser was efficient in preventing enamel demineralization. The SEM results of the fractured enamel surfaces, resin/enamel interfaces, and demineralization depths were consistent with those of the TBS test and the acid resistance evaluation. Pulsed Nd:YAG laser as an enamel surface pretreatment method presents a potential clinical application, especially for the caries-susceptible population or individuals with recently bleached teeth.

SUMMARY Dental fluorosis is a developmental disturbance of enamel caused by excessive fluoride on ameloblasts during enamel formation. Patients often present to the dentist with a main goal of improving their esthetic appearance. This case report describes a minimally invasive technique for treating a severe case of enamel fluorosis with brown surface aspect and small defects. A selective mega-abrasion and microabrasion were used to recreate macro- and micro- surface morphology, followed by power bleaching, home bleaching, and resin infiltration to improve the esthetic appearance.

SUMMARY The purpose of this study was to determine if the actual concentration of bleaching agents available in four different countries were the same as the label indicated and within the recommendations of the International Standard on Tooth Whitening. The method recommended for assaying peroxide by the United States Pharmacopeia was used to determine concentrations. All products in the United States and China were within the standard when products were tested immediately upon delivery at testing sites. One product in Saudi Arabia and three products in Brazil had greater than 30% concentration loss. Three of 24 products in the United States did not meet the International Standard when they were tested at month of expiration.

SUMMARY This study evaluated the effects of two in-office bleaching agents (Beyond and Opalescence Boost) with different pH on the structure and mechanical properties of human enamel in vitro and in situ . One hundred and eight enamel slabs were obtained from freshly extracted premolars. The specimens were randomly distributed into nine groups (n=12), and the human saliva (HS) in the volunteers' oral cavities was used to simulate the in situ condition: Beyond + HS, Opalescence Boost (O-Boost) + HS, Control + HS, Beyond + artificial saliva (AS), O-Boost + AS, Control + AS, Beyond + distilled water (DW), O-Boost + DW, and Control + DW. The bleaching treatments were performed on the first and eighth day, and the total bleaching time was 90 minutes. Baseline and final surface roughness (RMS), surface morphology, microhardness, and fracture toughness (FT) were measured before the treatment and on the fifteenth day, respectively. Compared with control groups, surface alterations on enamel were found in the Beyond + AS and Beyond + DW groups under atomic force microscopy evaluation. Two-way analysis of variance and Tukey test revealed that the RMS showed significant intergroup differences for both storage condition and bleaching agent, whereas microhardness and FT revealed no significant alteration. The results indicated that in-office bleaching agents with low pH values could induce enamel morphology alterations under in vitro conditions. The presence of natural HS could eliminate the demineralization effect caused by low pH.

SUMMARY This study investigated the influence of pH values of bleaching agents on the properties of the enamel surface. Sixty freshly extracted premolars were embedded in epoxy resin and mesiodistally sectioned through the buccal aspect into two parts. The sectioned slabs were distributed among six groups (n=10) and treated using different solutions. Group HCl was treated with HCl solution (pH=3.0) and served as a positive control. Group DW, stored in distilled water (pH=7.0), served as a negative control. Four treatment groups were treated using 30% hydrogen peroxide solutions with different pH values: group HP3 (pH=3.0), group HP5 (pH=5.0), group HP7 (pH=7.0), and group HP8 (pH=8.0). The buccal slabs were subjected to spectrophotometric evaluations. Scanning electron microscopy investigation and Micro-Raman spectroscopy were used to evaluate enamel surface morphological and chemical composition alterations. pH value has a significant influence on the color changes after bleaching ( p <0.001). Tukey's multiple comparisons revealed that the order of color changes was HP8, HP7>HP5, HP3>HCl>DW. No obvious morphological alterations were detected on the enamel surface in groups DW, HP7, and HP8. The enamel surface of groups HCl and HP3 showed significant alterations with an erosion appearance. No obvious chemical composition changes were detected with respect to Micro-Raman analysis. Within the limitations of this study, it was concluded that no obvious morphological or chemical composition alterations of enamel surface were detected in the neutral or alkaline bleaching solutions. Bleaching solutions with lower pH values could result in more significant erosion of enamel, which represented a slight whitening effect.

Clinical Relevance Macro-Lock post combined with auxiliary fiber posts could increase the fracture resistance of endodontically treated roots with over-flared canals. However, an effect of the auxiliary fibers on retention strength was not observed. SUMMARY This study investigated the fracture resistance and retention of endodontically treated roots with over-flared canals restored with different post systems, including one cast metal post and four fiber posts with/without auxiliary fiber posts. One hundred endodontically treated incisor roots were experimentally flared using a tapered diamond bur. The roots were restored using one of the five post systems: Ni-Cr cast metal post (CM), D.T. Light glass fiber post (DT), Macro-Lock glass fiber post (ML), ML+2 Fibercone auxiliary fiber posts (2FC), and ML+5 Fibercone auxiliary fiber posts (5FC). After fabrication of the crowns, half of the specimens (n=50) were subjected to a fracture failure test—loading with an incremental static force at an angle of 45 degrees to the long axis of the root. The other 50 samples underwent a pull-out test. Fracture failure strength and pull-out strength were measured and analyzed using one-way analysis of variance (ANOVA) followed by Tukey's post hoc test (α=0.05). After the tests were completed, all specimens displayed oblique root fractures or cracks, initiating from the palatal cervical margin and propagating in a labial-apical direction. The order of the fracture failure strength was as follows: 5FC=CM=2FC>ML>DT. Cast metal posts demonstrated the highest pull-out strength ( p <0.05). No significant differences in pull-out strength were found in the ML, 2FC, and 5FC groups. Within the limitations of this study, it was concluded that the application of an auxiliary fiber post could significantly increase the fracture resistance of over-flared roots; however, no beneficial effects in enhancing retention were observed.

Clinical Relevance The effectiveness of self-etch adhesive systems is dependent on both the physical properties of the adhesive and the integrity of the adhesive-dentin interface. Most importantly, the integrity of the adhesive-dentin interface is affected by the tubule orientation of the intaglio dentin structure. The initial bond strength and potential durability of the self-etch adhesive interfaces to dentin are significantly affected by both the adhesive pH and occlusally-oriented tubule direction. The clinical relevance to the dentist is that the results reported for bond strengths by both manufacturers and independent researchers should be interpreted and compared based on the orientation of the dentin used for the measurements, particularly for those adhesives that are very acidic (pH lower than 2). Abstract OBJECTIVE: To determine the effect of varying the adhesive pH on the bond strength of an experimental self-etch adhesive system (BISCO, Inc) to dentin with the bonding surface perpendicular (occlusal direction) or parallel (axial direction) to dentin tubules. METHODS: An experimental self-etch adhesive was modified by adding base to increase the pH from 1.1 to 2.7. Shear bond strength (SBS) was measured using an Ultradent jig method with Aelite All-Purpose Body light-cured composite (BISCO, Inc). Human dentin was prepared by exposing the axial and occlusal surface. The self-etch adhesive was applied according to the manufacturer's instructions and cured for 10 seconds@ 500mW using a VIP (BISCO, Inc) halogen curing light. Scanning electron microscope (SEM) examination was used to view both the occlusal- and axial-oriented dentin surfaces that were etched using pH (1.2~3.0) adjusted phosphoric acid solutions. All bond strength data analysis was performed using ANOVA, followed by a Student-Newman-Keuls multiple range test. RESULTS: When the dentin-bonding surface was parallel to the tubule orientation (axial), the bond strength was independent of the pH of the self-etch adhesive ( p >0.05). When the bonded surface was perpendicular to the tubule orientation (occlusal), the bond strength numbers were decreased as the pH decreased; the decrease became statistically significant when the pH was lower than 1.8. With a pH higher than 2.3, the bond strength had no difference ( p >0.05) between the occlusal and axial positions. When the pH was lower than 1.8, SEM pictures confirmed that the smear layers and smear plugs were completely solubilized by the phosphoric acid solution. Higher pH values (2.0–2.8) showed smear layers partially solubilized and pH values of 3.0 fully retained the smear layer.

Clinical Relevance Carbamide peroxide treatment increased the microleakage of Class V conventional glass-ionomer cement and resin modified glass-ionomer cement restorations. The resin coating is an effective method to avoid bleaching-induced microleakage without affecting the bleaching outcome. SUMMARY This in vitro study evaluated the effects of a resin coating on the microleakage of Class V restorations due to bleaching. One-hundred and sixty Class V cavities were randomly restored with one of four different restorative materials (n=40): a compomer (Dyract AP), a conventional glass-ionomer cement (Ketac Molar Easymix), a resin modified glass-ionomer cement (Fuji II LC) and a resin composite (Filtek Z350). For each kind of material, 40 restorations were divided into four subgroups: bleached with resin coating (group BC), bleached without resin coating (group B), immersed in artificial saliva with resin coating (group SC), immersed in artificial saliva without resin coating (group S). In groups B and BC, the specimens were bleached with 10% carbamide peroxide gel for eight hours daily, while groups SC and S were stored in artificial saliva instead. After 28-day treatment, all the samples were subjected to a dye penetration test using the multiple-sectioning technique. In addition, one more test was performed to investigate the color difference between the coated and uncoated tooth surface after bleaching. There was a statistically significant increase in cervical microleakage in the group B specimens of Fuji II LC and Ketac Molar Easymix compared to their respective control specimen (group S). These effects on microleakage were not found in the bleached specimens with resin coating (group BC). There was also no visually-detectable color difference between the coated and uncoated tooth surface. In conclusion, resin coating is an effective method for avoiding the bleaching-induced microleakage of glass-ionomer cement.

Clinical Relevance The bonding strength of resin composite to bleached enamel can be enhanced by increasing the light exposure time of light-emitting diode units if bonding is delayed for 24 hours. SUMMARY This study evaluated the effect of prolonged light-curing time using a light-emitting diode unit (LED) on the shear bond strength of a resin composite to enamel immediately after bleaching. The enamel surfaces of human molars were divided into four groups: one control and three bleaching groups. One bleaching group (CP) was exposed to a 10% carbamide peroxide bleaching agent and bonded after 24 hours. The other two bleaching groups (HP) were bleached with a 38% hydrogen peroxide bleaching agent, then bonded either within one hour (HPA) or after 24 hours (HPB). All groups were subdivided into two subgroups and cured for two different times (20 or 40 seconds) with an LED unit. Shear bond strength (SBS) was tested with a universal-testing machine and the data were analyzed by ANOVA and post-hoc tests. Scanning electron micrographs of representative specimens were taken. A significant difference was seen between the control and HPA groups for both curing times ( p =0.000). However, neither the CP nor HPB groups showed any significant differences compared with the control groups ( p >0.05). Two-way ANOVA showed that a significant effect of the curing time factor was recorded for all groups ( p =0.000). Prolonged curing time, using an LED unit with a light intensity of 500mW/cm 2 , increased resin-enamel bonding strengths for the control and bleached groups when bonding was performed after 24 hours of immersion in deionized water. However, the SBS was still compromised when bonding was performed immediately to enamel bleached with 38% HP.

Clinical Relevance When compared with a two-step self-etching adhesive, the microtensile bond strength of a one-step self-etch adhesive bonding to both normal and sclerotic dentin was more affected by thermocycling. SUMMARY This study evaluated the effects of thermocycling on the microtensile bond strength (μTBS) of oneand two-step self-etch adhesives (SEAs) to sclerotic dentin. Two adhesives, Clearfil S 3 Bond (S3), a one-step self-etch adhesive (1-SEA), and Clearfil SE Bond (SE), a two-step self-etch adhesive (2- SEA), were applied on cervical lesions in human premolars with sclerotic or normal dentin. After adhesive application, the lesions were restored and built up using a resin composite (Clearfil AP-X). After 24 hours in water storage, the restored teeth were sectioned into 0.7 × 0.7 mm composite-dentin beams. The beams were then aged with 0, 5,000 or 10,000 thermocycles. The use of two adhesives, two substrate types and three thermocycling regimens yielded 12 experimental groups of 14–19 beams each. The beams were subsequently subjected to μTBS testing at a crosshead speed of 1 mm/minute and statistical analyses were computed with three-way ANOVA and Tukey's post hoc test at p <0.05. Three-way ANOVA showed statistically significant effects on bonding effectiveness by lesion type, adhesive system, thermocycling or combinations of the adhesive system and thermocycling ( p <0.05). With sclerotic dentin, although S3 and SE provided comparable μTBS after 24 hours of water storage, S3 showed significantly lower μTBS than SE after thermocycling ( p <0.05). Regardless of lesion type, the μTBS for S3 decreased significantly after 5,000 or 10,000 thermocycles, while the μTBS for SE showed a significant decrease only after 10,000 thermocycles. Regardless of the extent of thermocycling, the μTBS values for either SE or S3 bonded to sclerotic dentin were significantly lower than to normal dentin ( p <0.05). The results suggested that thermocycling had a significant negative effect on the bond strength of the two SEAs tested. In contrast to 2-SEA, 1-SEA might not be a good choice for sclerotic dentin when seeking durability of the resin-dentin bond.

Clinical Relevance The flexural strength of dental materials can be affected by carbamide peroxide. The environmental temperature can be thought to be a factor influencing the bleaching effects on dental materials. SUMMARY The current study investigated the influence of carbamide peroxide on the flexural strength of tooth-colored restorative materials at two environmental temperatures. Seven restorative materials were used, including four resin composites (Filtek Z350, Filtek Z250, Synergy Flow and Filtek P60), a polyacid-modified composite (Dyract AP), a conventional glass-ionomer cement (Ketac Molar Easymix) and a ceramic (Vitablocs Mark II). For each type of material, 80 bar-shaped specimens were fabricated and divided into four groups (n=20): bleaching group at 25°C, control group at 25°C, bleaching group at 37°C and control group at 37°C. The specimens in the bleaching groups were treated with 10% carbamide peroxide gel for eight hours/day, while the control specimens in their respective groups were stored in deionized water. After 14-day treatment, the flexural strength of the specimens was determined using a universal testing machine. All the results were analyzed with ANOVA and the Tukey's post-hoc test. The data were also submitted to Weibull distribution. The flexural strength and its Weibull distribution of polyacid-modified composite and glass-ionomer cement were more seriously affected by bleaching agents than the resin composite and ceramic, especially at the higher environmental temperature.

Clinical Relevance The staining susceptibility of esthetic restorative materials is significantly affected by the use of 15% carbamide peroxide. The effects of bleaching on the surface morphology and color of restorative materials are material dependent. SUMMARY This study investigated the effects of an at-home bleaching gel containing 15% carbamide peroxide on the susceptibility of tooth-colored restorative materials to different staining solutions. The tooth-colored restoratives used in this study were a nano resin composite (Filtek Z350), a packable resin composite (Filtek P60), a poly-acid-modified composite (Dyract AP) and a glass-ionomer cement (Ketac Molar Easymix). Each material was equally divided into two groups (n=34): the bleaching group and the control group. This study included two treatment segments. In the first part (days 1–14), the specimens of the bleaching group were bleached with 15% carbamide peroxide gels for eight hours daily, while the specimens in the control group were stored in deionized water. Subsequently, four specimens from each group were randomly selected for observation under an environmental scanning electron microscope. In the second part (days 15–42), the samples were not bleached. Instead, they were stored in five different kinds of solutions. Color measurements for each sample were taken at six different time periods using a spectrophotometer. The data was then analyzed using SPSS statistical software. After two-weeks of bleaching, all the specimens showed statistically significant color changes compared with the control specimens. Furthermore, the bleaching agents seriously affected the surface morphology of Dyract AP and Ketac Molar Easymix. Following exposure to the staining solutions, it was found that the bleached restorative materials exhibited greater staining susceptibility than the control materials. Filtek Z350 and P60 exhibited the best color stability, while Dyract AP exhibited the least color stability.

Clinical Relevance When using a tray delivery technique, tetracycline-stained teeth can be effectively lightened with the extended use of tooth whiteners. Cervical staining is the most difficult area to lighten. SUMMARY Bleaching tetracycline-stained teeth is the most challenging form of tooth lightening. This article reports on 44 subjects who bleached their tetracycline-stained teeth for 6 months using trays with reservoirs overnight in a half-mouth designed study and 2 of 3 different concentrations of carbamide peroxide (10%, 15% or 20%). The subjects were followed for 5 years. The area evaluated was the middle third of the teeth. More than 55% of tooth lightening occurred within 1 month; after 5 years, more than 65% of the maximum tooth whitening remained for all 3 gel concentrations. Tooth whitening can be accomplished with any of the 3 concentrations used.

SUMMARY This study examined the effect of early water exposure on the shear strength of a spectrum of glass ionomer restoratives. The materials evaluated included conventional auto-cured (Fuji II [FT], GC), resin-modified light-cured (Fuji II LC [FL]) and, recently introduced, high strength auto-cured (Fuji IX GP Fast [FN], GC; Ketac Molar Quick [KQ], 3M-ESPE; Ketac Molar [KM], 3M-ESPE) cements. Sixteen specimens (8.7-mm in diameter and 1-mm thick) of each material were prepared in metal washers and randomly divided into 2 groups. The specimens were allowed to set for 6 minutes between polyester strips, to ensure completion of the initial set. The strips were subsequently removed, and the surfaces of Group 1 specimens were coated on both sides with resin (Fuji Coat LC, GC) and light cured for 10 seconds. Group 2 specimens were left uncoated. All specimens were then conditioned in distilled water at 37°C for 4 weeks. After conditioning, the specimens were restrained with a torque of 2.5 Nm and subjected to shear punch testing using a 2-mm diameter punch at a crosshead speed of 0.5-mm/minute. The mean shear strengths of the materials were computed and subjected to Independent Samples t -test and ANOVA/Scheffe's tests at significance level 0.05. Mean strength ranged from 78.34 to 99.36 MPa and 79.88 to 95.78 MPa for Groups 1 and 2, respectively. No significant difference in shear strength was observed between the 2 groups. For both groups, KM and KQ were significantly stronger than FT. Contrary to current teaching, early exposure to water did not weaken glass ionomer restoratives. A marginal increase in strength was actually observed for some materials. Clinical Relevance Modern day glass ionomer restoratives are not significantly weakened by early water exposure, after initial set.