This study investigated the clinical effectiveness and safety of sealed bleaching compared to conventional in-office bleaching using a randomized clinical trial of split arch design. Ten participants received a chairside bleaching treatment on the upper anterior teeth, and each side was randomly designated as sealed or control side. A mixture of Brite powder (PacDent, Walnut, USA), 3% hydrogen peroxide and carbamide peroxide (KoolWhite, PacDent, Walnut, USA) were used as bleaching agent. The control side was unwrapped and the experimental side was covered with a linear low density polyethylene (LLDPE) wrap for sealed bleaching. The bleaching gel was light activated for 1 hour. The tooth shades were evaluated before treatment, after treatment, and at one week check up by means of a visual shade (VS) assessment using a value oriented shade guide and a computer assisted shade assessment using a spectrophotometer (SP). The data were analyzed by paired t-test.

In the control and sealed groups, the visual shade scores after bleaching treatment and at check up showed statistically significant difference from the preoperative shade scores (p < .05). The shade scores of the sealed group were significantly lighter than the control immediately after bleaching and at the check-up appointment (p < 0.05). Compared to prebleaching status, the ΔE values at post-bleaching condition were 4.35 ± 1.38 and 5.08 ± 1.34 for the control and sealed groups, respectively. The ΔE values at check up were 3.73 ± 1.95 and 4.38 ± 2.08 for the control and sealed groups. ΔE values were greater for the sealed group both after bleaching (p < .05) and at check up (p < .05).

In conclusion, both ΔE and shade score changes were greater for the sealed bleaching group than the conventional bleaching group, effectively demonstrating the improvement of effectiveness through sealing.

"Residual stress" can be developed during polymerization of the dental composite and it can be remained after this process was completed. The total amount of the force which applied to the composite restoration can be calculated by the sum of external and internal force. For the complete understanding of the restoration failure behavior, these two factors should be considered. In this experiment, I compared the residual stress of the recently developed nanofilled dental composite by ring slitting methods.

The composites used in this study can be categorized in two groups, one is microhybrid type-Z250, as control group, and nanofilled type-Grandio, Filtek Supreme, Ceram-X, as experimental ones. Composite ring was made and marked two reference points on the surface. Then measure the change of the distance between these two points before and after ring slitting. From the distance change, average circumferential residual stress (σθ) was calculated. In 10 minutes and 1 hour measurement groups, Filtek Supreme showed higher residual stress than Z250 and Ceram-X. In 24 hour group, Filtek showed higher stress than the other groups.

Following the result of this experiment, nanofilled composite showed similar or higher residual stress than Z250, and when comparing the Z250 and Filtek Supreme, which have quite similar matrix components, Filtek Supreme groups showed higher residual stress.

The aim of this study was to compare the compositions and cytotoxicity of white ProRoot MTA (white mineral trioxide aggregate) and 3 kinds of Portland cements. The elements, simple oxides and phase compositions of white MTA (WMTA), gray Portland cement (GPC), white Portland cement (WPC) and fast setting cement (FSC) were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray fluorescence spectrometry (XRF) and X-ray diffractometry (XRD). Agar diffusion test was carried out to evaluate the cytotoxicity of WMTA and 3 kinds of Portland cements.

The results showed that WMTA and WPC contained far less magnesium (Mg), iron (Fe), manganese (Mn), and zinc (Zn) than GPC and FSC. FSC contained far more aluminum oxide (Al₂O₃) than WMTA, GPC, and WPC. WMTA, GPC, WPC and FSC were composed of main phases, such as tricalcicium silicate (3CaO·SiO₂), dicalcium silicate (2CaO·SiO₂), tricalcium aluminate (3CaO·Al₂O₃), and tetracalcium aluminoferrite (4CaO·Al₂O₃·Fe₂O₃). The significance of the differences in cellular response between WMTA, GPC, WPC and FSC was statistically analyzed by Kruskal-Wallis Exact test with Bonferroni's correction. The result showed no statistically significant difference (p > 0.05).

WMTA, GPC, WPC and FSC showed similar compositions. However there were notable differences in the content of minor elements, such as aluminum (Al), magnesium, iron, manganese, and zinc. These differences might influence the physical properties of cements.

The objective of this study was to compare dentin shear bond strength (DSBS) of dentin bonding agents (DBAs) cured with a plasma arc (PAC) light curing unit (LCU) and those cured with a light emitting diode (LED) LCU. Optical properties were also analyzed for Elipar freelight 2 (3M ESPE); LED LCU, Apollo 95E (DMT Systems); PAC LCU and VIP Junior (Bisco); Halogen LCU. The DBAs used for DSBS test were Scotchbond Multipurpose (3M ESPE), Singlebond 2 (3M ESPE) and Clearfil SE Bond (Kuraray). After DSBS testing, fractured specimens were analyzed for failure modes with SEM.

The total irradiance and irradiance between 450 nm and 490 nm of the LCUs were different. LED LCU showed narrow spectral distribution around its peak at 462 nm whereas PAC and Halogen LCU showed a broad spectrum. There were no significant differences in mean shear bond strength among different LCUs (P > 0.05) but were significant differences among different DBAs (P < 0.001)

The purpose of this study was to evaluate the difference in the surface roughness after polishing and to evaluate the difference in color stability after immersion in a dye solution among four types of composite resin materials. Four light-polymerized composite resins (Shade A2) with different sized filler content (a nanofilled, a hybrid, a microfilled, a flowble) were used. Average surface roughness (Ra) was measured with a surface roughness tester (Surftest Formtracer) before and after polishing with aluminum oxide abrasive discs (Super-Snap). Color of specimens before and after staining with 2% methylene blue solution were measured using spectrophotometer (CM-3700d) with SCI geometries. The results of Ra and ΔE were analyzed by one-way analysis of variance (ANOVA), a Scheffe multiple comparison test and Student t-test (p = 0.05). After polishing, Ra values were decreased regardless of type of composite resins. In surface roughness after polishing and color stability after staining, nanofilled composite resin was not different with other composite resins except flowable resins.

The purpose of this study was to evaluate the bond strength of a new Single step system with different curing mode composites, and to evaluate the effect of the intermediate resins which have different hydrophilicity on bonding ability by means of the micro shear bond testing and TEM examination for the adhesive interface. The adhesive used in this study was an experimental single step system (Bisco Inc., Schaumburg, IL). Experimental groups were produced by using six kinds of intermediate resin having different hydrophilicity that was hydrophilic, hydrophobic and most hydrophobic resin and as filled or not after applying adhesive. Each experimental group was further divided into two subgroups whether the adhesive was light cured or not. Dual cured composite (Bis Core, Bisco Ltd., Schaumburg, IL) was placed on the adhesive layer as light cure or self cure mode. The results of bond strength were statistically analyzed using one way ANOVA and multiple comparisons are made using Tukey's test at α < 0.05 level.

The results of this study were as follows;

1. The application of intermediate resin did not increase the bond strength for light cured composite.

2. The bond strength of an experimental adhesive with self cured composite was significantly increased by the application of intermediate resin layer.

3. The bond strength of adhesive was irrespective of the cure or not of itself before intermediate resin layer applied.

4. As applied hydrophilic resin layer was, the initial bond strength was higher than both hydrophobic and most hydrophobic one used but there was no significance.

Using a single step adhesive with dual/self cured composite, the incompatibility between both of them should be solved by the application of intermediate hydrophobic resin to reduce the adhesive permeability. However, Single step adhesive can be used in the light cured composite restoration without any decrease of the initial bond strength.

The purposes of this study were to examine the variability of adhesive thickness on the different site of the cavity wall when used total-etch system without filler and simplified self-etch system with filler and to evaluate the relationship between variable adhesive thickness and microtensile bond strength to the cavity wall.

A class I cavity in six human molars was prepared to expose all dentinal walls. Three teeth were bonded with a filled adhesive, Clearfil™ SE bond and the other three teeth were bonded with unfilled adhesives, Scotchbond™ Multi Purpose. Morphology and thickness of adhesive layer were examined using fluorescence microscope. Bonding agent thickness was measured at three points along the axial cavity wall, edge of cavity margin (rim), halfway down each cavity wall (hlf), internal angle of the cavity (ang). After reproducing the adhesive thickness at rim, hlf and ang, micro-tensile bond strength were evaluated.

For both bonding agents, adhesive thickness of ang was significantly thicker than that of rim and hlf (P < 0.05). As reproduced the adhesive thickness, microtensile bond strength was increased as adhesive thickness was increased in two bonding agents.

Adhesive thickness of internal angle of the cavity was significantly thicker than that of the cavity margin and the halfway cavity wall for both bonding agents. Microtensile bond strength of the thick adhesive layer at the internal angle of the cavity was higher than that of the thin adhesive layer at the cavity margin and the halfway cavity in the two bonding systems.

The purpose of this study was to compare the shaping ability of the two different Ni-Ti file systems and the two different engine systems in simulated canals.

A total of four groups of each 10 were tested. Each group was instrumented with HeroShaper®and Endo-Mate2® (Group HE), HeroShaper® and Tecnika® (Group HT), ProFile® and Endo-Mate2® (Group PE), and ProFile® and Tecnika® (Group PT).

Canal preparation time was recorded. The images of pre- and post-instrumented root canals were scanned and superimposed. The amounts of increased width and centering ratio were measured and calculated at apical 1, 3 and 5 mm levels.

These data were statistically analyzed with one-way ANOVA and Duncan's multiple range test

The results of this study were as follows;

1. Canal preparation time of HT group was the shortest (p < 0.05).

2. The amount of increased canal width in HE group was significantly larger than PT group at apical 1 mm level (p < 0.05). At apical 3 mm level, PT group was significantly smaller than other groups (p < 0.05). At apical 5 mm level, PE group was significantly larger than PT group (p < 0.05).

3. The amount of centering ratio in HE group was significantly larger than other groups (p < 0.05). At apical 5 mm level, HT group was significantly larger than PE group and PT group (p < 0.05).

Under the condition of this study, torque-controlled endodontic motor is safer than no torque controlled motor, especially when the active file is used.

The aim of this in vitro study was to evaluate the suitability of using chitosan, poly (lactide-co-glycolide) (PLGA), and polymethyl methacrylate (PMMA) to control the release of chlorhexidine digluconate (CHX) from a prototype of controlled release drug device (CRD) for root canal disinfection. Four different prototypes with different formulations were prepared. Group A (n = 12); The device (absorbent paper point) was loaded with CHX as control. Group B (n = 12); same as group A, but the device was coated with chitosan. In Groups C and D, the device was treated in the same way as group A and then coated three times with 5% PMMA (Group C, n = 12), or coated three times with 3% PLGA (Group D, n = 12). The devices were randomly allocated to experimental groups of 12 each.

All CRD prototypes were soaked in 3 mL distilled water. The concentrations of CHX were determined using a UV spectrophotometer. The surface characteristics of each prototype were observed using a scanning electron microscope.

The result showed that release rate of CHX was the greatest in the non-coated group, followed by the chitosan-coated group, the PLGA-coated group, and the PMMA-coated group (P < 0.05). Pores were observed on the surface of the prototypes that were coated with PLGA and PMMA. When the pore size was smaller, the release rate was lower. This data indicate that polymer coating can control the release rate of CHX from the CRD prototypes.

This study investigated that the effect of rewetting agent on dentinal microtensile bond strength (µTBS). Human molars were sectioned to expose the superficial dentin surfaces.

Samples were divided into two groups according to type of adhesives-Single Bond (S) and One-Step (O)], and again subdivided into five groups by different dentin surface treatment-dry for 15s (D), blot dry (BD) or dry for 15s, and rewet with different rewetting agents [distilled water (DW), Gluma Desensitizer (GD) and Aqua-Prep (AP)] for 30s. After application of adhesive, composite resin was built up on the bonding surface. Each tooth was sectioned to obtain stick with 1 mm² cross sectional area and the µTBS was determined by EZ test.

In the S group, the mean µTBS of GD, AP and BD group was significantly higher than that of DW and D group (p < 0.05). In the O group, the mean µTBS of AP, GD, BD and DW group was significantly higher than that of D group (p < 0.05).

The data suggested that Gluma Desensitizer and Aqua-Prep could be successfully used as rewetting agents, and Distilled water could be acceptable in aceton based adhesive system only.

This study compared the dentin shear bond strengths of currently used dentin bonding agents that were irradiated with an LED (Elipar FreeLight, 3M-ESPE) and a halogen light (VIP, BISCO). The optical characteristics of two light curing units were evaluated. Extracted human third molars were prepared to expose the occlusal dentin and the bonding procedures were performed under the irradiation with each light curing unit. The dentin bonding agents used in this study were Scotchbond Multipurpose (3M ESPE), Single Bond (3M ESPE), One-Step (Bisco), Clearfil SE bond (Kuraray), and Adper Prompt (3M ESPE). The shear test was performed by employing the design of a chisel-on-iris supported with a Teflon wall. The fractured dentin surface was observed with SEM to determine the failure mode.

The spectral appearance of the LED light curing unit was different from that of the halogen light curing unit in terms of maximum peak and distribution. The LED LCU (maximum peak in 465 ㎚) shows a narrower spectral distribution than the halogen LCU (maximum peak in 487 ㎚). With the exception of the Clearfil SE bond (P < 0.05), each 4 dentin bonding agents showed no significant difference between the halogen light-cured group and the LED light-cured group in the mean shear bond strength (P > 0.05).

The results can be explained by the strong correlation between the absorption spectrum of cam-phoroquinone and the narrow emission spectrum of LED.

This study evaluated the effectiveness of the light emitting diode(LED) units for composite curing. To compare its effectiveness with conventional quartz tungsten halogen (QTH) light curing unit, the microhardness of 2mm composite, Z250, which had been light cured by the LEDs (Ultralume LED2, FreeLight, Developing product D1) or QTH (XL 3000) were compared on the upper and lower surface. One way ANOVA with Tukey and Paired t-test was used at 95% levels of confidence. In addition, the amount of linear polymerization shrinkage was compared between composites which were light cured by QTH or LEDs using a custom-made linometer in 10s and 60s of light curing, and the amount of linear polymerization shrinkage was compared by one way ANOVA with Tukey.

The amount of polymerization shrinkage at 10s was

XL3000 > Ultralume 2, 40, 60> FreeLight, D1 (P<0.05)

The amount of polymerization shrinkage at 60s was

XL3000 > Ultralume 2, 60> Ultralume 2,40> FreeLight, D1 (P<0.05)

The microhardness on the upper and lower surface was as follows;

It was concluded that the LEDs produced lower polymerization shrinkage in 10s and 60s compared with QTH unit. In addition, the microhardness of samples which had been cured with LEDs was lower on the lower surfaces than the upper surfaces whereas there was no difference in QTH cured samples.

The purpose of this study is to evaluate the polymerization ability of three different light sources by microhardness test. Stainless steel molds of 1, 2, 3, 4 and 5 mm in thickness of 7 mm in diameter were prepared. The hybrid composite Z100 was packed into the hole of the mold and curing light was activated for designated time. Three different light sources, conventional halogen, light emitting diode, and plasma arc, were used for curing of composite. Two different curing times applied; one is to follow the manufacturer's recommendation and the other is to extend the curing time of LED and plasma arc for balancing the light energy with halogen. Immediately after curing, the Vickers hardness was measured at the bottom of specimen.

The results were as follows.

The composite cured with LED showed equal to higher microhardnesss than halogen.

In conclusion, this study suggested that plasma arc needs properly extended curing time.

Purpose of this research is estimating polymerization depth of different source of light. XL 3000 for halogen light, Apollo 95E for plasma arc light and Easy cure for LED light source were used in this study. Different shade (B1 & A3) resin composites (Esthet-X, Dentsply, U.S.A.) were used to measure depth of cure. 1, 2, and 3 mm thick samples were light cured for three seconds, six seconds or 10 seconds with Apollo 95E and they were light cured with XL-3000 and Easy cure for 10 seconds, 20 seconds, or 40 seconds. Vicker's hardness test carried out after store samples for 24 hours in distilled water.

Results were as following.

Curing time increases from all source of lights, curing depth increased(p<0.05).