• Journal of the korean academy of Pediatric Dentistry
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• v.41 no.2
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• pp.125-133
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• 2014

The purpose of this study was to investigate the effect of various surface treatment methods on the shear bond strength of orthodontic brackets in vitro. Ninety six specimens, 6 mm in diameter and 5 mm in height, were made with composite resin ($Filtek^{TM}$ Z350 XT, 3M ESPE, USA) and treated with an aging procedure. After aging, the specimens were randomly separated in six groups: (1) control with no surface treatment, (2) 37% phosphoric acid gel, (3) 4% hydrofluoric acid gel, (4) sodium bicarbonate particle abrasion, (5) diamond bur, and (6) 1 W carbon dioxide laser for 5s. The metal brackets were bonded to composite surfaces by means of an orthodontic adhesive (Transbond XT, 3M Unitek, USA). Shear bond strength values were evaluated with a universal testing machine (R&B Inc., Korea). Analysis of variance showed a significant difference between the groups. Group 5 had the highest mean shear bond strength (11.9 MPa), followed by group 6 (11.1 MPa). Among the experimental groups, group 2 resulted in the weakest mean shear bond strength (5.22 MPa). The results of this study suggest that the repair shear bond strength of the aged composite resin was acceptable by surface treatment with a carbon dioxide laser.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.4
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• pp.426-435
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• 2018

The aim of this study was to evaluate the proximal caries detecting ability and identify the optimal cut-off values of two types of laser fluorescence (LF) devices; classic type (DD) and pen type (DDpen). The number of proximal surfaces participated in this study were 164 surfaces in primary dentition and 438 surfaces in permanent dentition. Each tooth surface was sequentially assessed by two types of LF devices, and bitewing radiograph. The radiographs were classified into 3 groups in primary dentition ($pR_0$, $pR_1$, $pR_2$), and 4 groups in permanent dentition ($PR_0$, $PR_1$, $PR_2$, $PR_3$) according to the depth of caries, and used as gold standard. In primary dentition, the area under the curve (AUC) values of DD were 0.851 and 0.890, and those of DDpen were 0.883 and 0.917, respectively in enamel caries and dentin caries. In permanent dentition, the AUC values of DD were 0.762 and 0.886, and those of DDpen were 0.828 and 0.958, respectively in enamel caries and dentin caries. When detecting proximal caries in posterior teeth with LF devices, DDpen is more useful than DD in both primary and permanent dentition. However, in primary dentition, DD can also be useful to detect proximal caries.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.3
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• pp.640-658
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• 1996

The purpose of this study was to examine the mechanism of improving acid resistance of Nd-YAG laser irradiated tooth enamel and determine the most effective energy density for improving acid resistance. The bovine tooth enamel were lased with a pulsed Nd-YAG laser. The energy densities of exposed laser beam were varied from 10 to $70\;J/cm^2$. To investigate the degree of improving acid resistance by irradiation, all the samples were submerged to demineralize in 0.5 N $HClO_4$ solution for 1 minute. After 1 minute, 0.05 % $LaCl_3$ was added to the solution for interrupting the demineralization reaction. The amounts of dissolved calcium and phosphate in the solution were measured by using an atomic absorption spectrophotometer and the UV/VIS spectrophotometer, respectively. To examine the mechanism of improving acid resistance, X-ray diffraction analysis, infrared spectroscopy, and scanning electron microscopy were taken. The X-ray diffraction pattern of the samples were obtained in the $10^{\circ}{\sim}80^{\circ}2{\theta}$ range with $Cu-K{\alpha}$ radiation using M18HF(Mac Science Co.) with X-ray diffractometer operating at 40 KV and 300 mA. The infra-red spectra of the ground samples in 300 mg KBr pellets 10 mm diameter were obtained in the $4000cm^{-1}\;to\;400cm^{-1}$ range using JASCO 300E spectrophotometer. The scanning electron microscopy was carried out using JSM6400(JEOL Co.) with $500{\sim}2000$ times magnification. The results were as follow 1. The concentration of calcium dissolved from laser irradiated enamel with $50J/cm^2$ was significantly lesser than that of unlased control group (p<0.05) 2. From the result of the X-ray diffraction analysis, $\beta$-TCP, which increases acid solubility, was identified in lased enamel but the diffraction peaks of (002) and (004) became sharp with increasing energy density of laser irradiation. This means that the crystals in lased samples were grown through the c-axis and subsequently, the acid solubility of enamel decreased. 3. The a-axis parameter was slightly increased by laser irradiation, whereas the c-axis parameter was almost constant except for a little decrease at $50J/cm^2$. 4. In the infra-red spectra of lased enamels, phosphate bands ($600{\sim}500cm^{-1}$), B-carbonate bands (870, $1415{\sim}1455cm^{-1}$), and A-carbonate band ($1545cm^{-1}$) were observed. The amounts of phosphate bands and the B-carbonate bands were reduced, on the other hand, the amount of the A-carbonate band was increased by increase the energy density. 5. The SEM experiments reveal that the surface melting and recrystallization were appeared at $30J/cm^2$ and the cracks were observed at $70J/cm^2$. From above results, It may be suggested that the most effective energy density for improving acid resistance of tooth enamel with the irradiation of Nd-YAG laser was $50J/cm^2$. The mechanism of improving acid resistance were reduction of permeability due to surface melting and recrystallization of lased enamel and reduction of acid solubility of enamel due to decrease of carbonate content and growth of crystal.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.2
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• pp.262-268
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• 2006

The purpose of this in vitro study was to evaluate the remineralizing effects of Nd : YAG laser irradiation and fluorides application on primary tooth enamel eroded by acidic drink. The materials were 30 sound primary teeth with intact smooth enamel surfaces. They were demineralized with Coca-cola at $37^{\circ}C$ for 12 hours and then irradiated by Nd: YAG laser with 6W power, $50mJ/cm^2$ energy density. and 20Hz pulse repetition. After laser irradiation, teeth were treated by three kinds of fluorides : (1) 0.05% NaF solution, (2) 1.23% APF gel and (3) 0.1% fluoride varnish. Diagnodent scores and microhardness (VHN) were measured before and after the each treatment. The results were as follows: 1. Diagnodent scores decreased to 23.51% from the initial after demineralization, and then increased to 37.37% after laser irradiation, and to 51.34% after fluoride treatment. There were significant differences between the total scores of initial, demineralization, laser irradiation and fluoride treatment (P<0.05). There was no significant difference between scores after fluoride treatment according to fluoride types. 2. Microhardness(VHN) decreased to 33.58% from the initial after demineralization and then increased to 43.99% after laser irradiation, and to 51.38% after fluoride treatment. There were significant differences between the total scores of initial, demineralization, laser irradiation and fluoride treatment (P<0.05). There was no significant difference between scores after fluoride treatment according to fluoride types.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.5
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• pp.520-527
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• 2008

Purpose: This study was conducted to evaluate the shear bond strength of composite resin to dentin when etched with laser instead of phosphoric acid. Material and methods: Recently extracted forty molars, completely free of dental caries, were embedded into acrylic resin. After exposing dentin with diamond saw, teeth surface were polished with a series of SiC paper. The teeth were divided into four groups composed of 10 specimens each; 1) no surface treated group as a control 2) acid-etched with 35%-phosphoric acid 3) Er:YAG laser treated 4) Er,Cr:YSGG laser treated. A dentin bonding agent (Adapter Single Bond2, 3M/ESPE) was applied to the specimens and then transparent plastic tubes (3 mm of height and diameter) were placed on each dentin. The composite resin was inserted into the tubes and cured. All the specimens were stored in distilled water at $37^{\circ}C$ for 24 hours and the shear bond strength was measured using a universal testing machine (Z020, Zwick, Germany). The data of tensile bond strength were statistically analyzed by one-way ANOVA and Duncan's test at ${\alpha}$= 0.05. Results: The bond strengths of Er:YAG laser-treated group was $3.98{\pm}0.88$ MPa and Er,Cr:YSGG laser-treated group showed $3.70{\pm}1.55$ MPa. There were no significant differences between two laser groups. The control group showed the lowest bond strength, $1.52{\pm}0.42$ MPa and the highest shear bond strength was presented in acid-etched group, $7.10{\pm}1.86$ MPa (P < .05). Conclusion: Laser-etched group exhibited significantly higer bond strength than that of control group, while still weaker than that of the phosphoric acid-etched group.

• The korean journal of orthodontics
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• v.23 no.4 s.43
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• pp.619-631
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• 1993

Tooth movement by segment is one of the means which are frequently used in daily orthodontic practice. When we retract or intrude a tooth or teeth, we should recognize the center of resistance of the certain tooth or teeth. There have been many studies about the center of resistance of a single tooth, not so much was about the tooth-segment. At the present study the center of resistance of the maxillary anterior segment is experimentally investigated by using laser reflection technique and metal splints on the human dry skull. The variables of intrusive force magnitude are divided into two groups, 50g and 100g groups. The results were as follows ; 1. The center of resistance of the maxillary anterior segment composed of the central and lateral incisors was at the mesial portion of canine crown at the coronal level. 2. The center of resistance of the maxillary anterior segment composed of the central and lateral incisors and canines is between the canine and the 1st premolar crowns at the coronal level.

• The korean journal of orthodontics
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• v.16 no.2
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• pp.43-51
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• 1986

The highly accurate laser holographic interferemotry method was used to determine in what way low-magnitude forces during maxillary expansion are transmitted to the entire maxillary complex and its surrounding structures. The experiments were carried out on a dryed human skull which had a perfectly preserved, normally aligned maxillary dental arch and intact alveolar process. The skull was fixed within a constructed metal frame which ensured maximal stability of the object. The optical equipment and the object were mounted on antivibration table. Interferograms were taken on the lateral and frontal sides of the maxillary complex, using the 10mW He-Ne laser and the double-exposure method. Analysis of the fringe pattern on the recorded object surface was performed by graphically determining the deformation curves related to the bony surface in selected horizontal and vertical planes. On the basis of this study, the following conclusions can be drawn: 1. The density of the interference fringes was gradually increased with the degree of expansion force. 2. Mechanical reactions on the maxillary complex, circummaxillary sutures, and surrounding bones were clearly visible, even with the lowest loading degree. 3. The amount of bone displacement was greater in application of the force after $90^{\circ}$ turn than in initial application of the same force. 4. The direction of interference fringes on the bony surface was similar at all loading degrees.

• The Journal of Advanced Prosthodontics
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• v.8 no.3
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• pp.235-240
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• 2016

PURPOSE. In this study, the aim of this study was to evaluate the effect of implant surface treatment on cell differentiation of osteoblast cells. For this purpose, three surfaces were compared: (1) a modified SLA (MSLA: sand-blasted with large grit, acid-etched, and immersed in 0.9% NaCl), (2) a laser treatment (LT: laser treatment) titanium surface and (3) a laser and acid-treated (LAT: laser treatment, acid-etched) titanium surface. MATERIALS AND METHODS. The MSLA surfaces were considered as the control group, and LT and LAT surfaces as test groups. Alkaline phosphatase expression (ALP) was used to quantify osteoblastic differentiation of MC3T3-E1 cell. Surface roughness was evaluated by a contact profilometer (URFPAK-SV; Mitutoyo, Kawasaki, Japan) and characterized by two parameters: mean roughness (Ra) and maximum peak-to-valley height (Rt). RESULTS. Scanning electron microscope revealed that MSLA (control group) surface was not as rough as LT, LAT surface (test groups). Alkaline phosphatase expression, the measure of osteoblastic differentiation, and total ALP expression by surface-adherent cells were found to be highest at 21 days for all three surfaces tested (P<.05). Furthermore, ALP expression levels of MSLA and LAT surfaces were significantly higher than expression levels of LT surface-adherent cells at 7, 14, and 21 days, respectively (P<.05). However, ALP expression levels between MSLA and LAT surface were equal at 7, 14, and 21 days (P>.05). CONCLUSION. This study suggested that MSLA and LAT surfaces exhibited more favorable environment for osteoblast differentiation when compared with LT surface, the results that are important for implant surface modification studies.

• Journal of Periodontal and Implant Science
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• v.43 no.2
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• pp.101-105
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• 2013

Purpose: The present study aimed to measure root surface roughness in teeth with periodontitis by a profilometer following root planning with ultrasonic and hand instruments with and without erbium-doped yttrium aluminium garnet (Er:YAG) laser irradiation. Methods: Sixty single-rooted maxillary and mandibular teeth, extracted because of periodontal disease, were collected. The crowns and apices of the roots were cut off using a diamond bur and water coolant. The specimens were mounted in an acrylic resin block such that a plain root surface was accessible. After primary evaluation and setting a baseline, the samples were divided into 4 groups. In group 1, the samples were root planned using a manual curette. The group 2 samples were prepared with an ultrasonic scaler. In group 3, after scaling with hand instrumentation, the roots were treated with a Smart 1240D plus Er:YAG laser and in group 4, the roots were prepared with ultrasonic scaler and subsequently treated with an Er:YAG laser. Root surface roughness was then measured by a profilometer (MahrSurf M300+RD18C system) under controlled laboratory conditions at a temperature of $25^{\circ}C$ and 41% humidity. The data were analyzed statistically using analysis of variance and a t-test (P<0.05). Results: Significant differences were detected in terms of surface roughness and surface distortion before and after treatment. The average reduction of the surface roughness after treatment in groups 1, 2, 3, and 4 was 1.89, 1.88, 1.40, and 1.52, respectively. These findings revealed no significant differences among the four groups. Conclusions: An Er:YAG laser as an adjunct to traditional scaling and root planning reduces root surface roughness. However, the surface ultrastructure is more irregular than when using conventional methods.

• Journal of Yeungnam Medical Science
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• v.36 no.1
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• pp.43-49
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• 2019

Background: In the osseointegration of dental implants, the implant surface properties have been reported to be some of the most important critical factors. The effect of implant's surfaces created by resorbable blast media (RBM) followed by laser ablation on bone tissue reactions was examined using the removal torque test and histomorphometric analysis. Methods: Two types of dental implants, RBM-laser implants (experimental group) and RBM implants (control group) (CSM implant system, Daegu, Korea; L=6 mm, diameter=3.75 mm) were placed into the right and left distal femoral metaphysis of 17 adult rabbits. Six weeks after placement, removal torque was measured and histomorphometric analysis was performed. Results: The mean removal torque was $24.0{\pm}10.2Ncm$ and $46.6{\pm}16.4Ncm$ for the control and test specimens, respectively. The experimental RBM-laser implants had significantly higher removal torque values than the control RBM implants (p=0.013). The mean values of total and cortical bone to implant contact (BIC) were respectively $46.3{\pm}10.8%$ and $65.3{\pm}12.5%$ for the experimental group, and $41.9{\pm}18.5%$ and $57.6{\pm}10.6%$ for the control group. The experimental RBM-laser implants showed a higher degree of total and cortical BIC compared with RBM implants, but there was no statistical significance (p=0.482, 0.225). Conclusion: The removal torque and BIC of the test group were higher than those of the control group. In this study, the surface treatment created by RBM treatment followed by laser ablation appears to have a potential in improving bone tissue reactions of dental implants.