• Journal of Oral Medicine and Pain
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• v.25 no.4
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• pp.415-425
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• 2000

In order to obtain the basic data concerning the optimal lasing conditions in using Nd:YAG laser as an adjunctive modality of periodontal therapy of root planing without irreversible structural deterioration of cervical cementum, the author selected 36 human teeth having no cervical abrasion and caries (; 12 anteriors, 12 premolars. 12 molars) extracted due to periodontal diseases, and divided them into 4 groups as Group I, II, III and IV (; each group of 3 anteriors, 3 premolars, 3 molars), and prepared a cementum specimen with thickness of $1.0mm{\pm}0.2mm$ sectioned longitudinally at the middle of mesio-distal thickness (; Group I) or horizontally at 1mm-2mm below the cemento-enamel junction (; Group II, III, IV) from each tooth of each group by low speed diamond wheel saw, and treated them with 0.5 M ethylene diamine tetraacetic acid (; EDTA, pH=7.4) for 2 minutes for elimination of remnants during tooth-sectioning. And the author applied the laser energy from a fiberoptic delivered, free running, pulsed Nd:YAG laser (; wavelength 1064nm. pulse duration $120{\mu}sec$, fiber diameter $320{{\mu}m}$) to cementum surfaces in triplicates of one experiment under the following lasing conditions: 1. stationary mode of fiber in contact to cementum surfaces without air-spray (; Group I )/with air-spray (; Group II), 2. unidirectional moving mode of fiber in contact to cementum surfaces under speed of 3mm-4mm/sec without air-spray (; Group III)/with air-spray (; Group IV), 3. energy per pulse (mJ/pulse) [; energy density ($J/cm^{2}$)] in order of 1.0W/10Hz (100J/pulse); $124J/cm^{2}$, 0.5W/10Hz (50mJ/pulse); $62J/cm^{2}$, 0.4W/10Hz (40mJ/pulse); $50J/cm^{2}$, 0.3W/10Hz (30mJ/pulse); $37J/cm^{2}$, 4. exposure time of 1 second. And the author applied the platinum coating on surfaces of cementum specimens, and evaluated the characteristics of ultrastructural change on surfaces of cementum using the scanning electron microscopy. In general the ultrastructural loss of cervical cementum irradiated under the same lasing condition of laser energy density occurred least in specimens of Group IV. And especially, the ultrastructural loss of cervical cementum irradiated under the laser energy density of $37J/cm^{2}$ almost did not occur in specimens of Group IV. Therefore, it is considered that the pulsed Nd:YAG laser should be applied with the lasing conditions of unidirectional moving mode of fiber in contact to cementum surfaces under speed of 3mm-4mm/sec with air-spray and of laser energy density within $37J/cm^{2}$ as an adjunctive modality of periodontal therapy of root planing without irreversible structural deterioration of cervical cementum.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.1
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• pp.144-151
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• 2005

Erosion is believed to be the predominant cause of teeth wear in children and young adults, although there will at ways be a contribution from attrition and abrasion. The pH of cola is known to be low and have, therefore, been implicated in the increasing incidence of erosion. The aim of present study was to evaluate the effect of cola on the progression of erosive demineralization in human enamel using demineralization model in vitro. Six groups of human enamel slap were immersed(5 min each bath) in fresh cola, with immersions taking place with or without agitation, and under 3 regimes of frequency intake(low intake, 1 immersion/day; medium, 5/day; high, 10/day). Quantitative assessments of surface erosion were done over an 8-day interval using surface microhardness testing. 1. The average pH of cola was 2.5, which was acidic enough to cause tooth erosion. 2. All the enamel specimen exposed to cola showed erosion like lesions and surface hardness decreased in proportion to the length of immersion (p<0.05). 3. The surface hardness of enamel decreased in proportion to the frequency of immersion (p<0.05). 4. Increased degassing from the drink by gitation accelerated the enamel softening compared with those without agitation.

• Journal of dental hygiene science
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• v.2 no.2
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• pp.63-67
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• 2002

The purpose of this study was to develop more effective dental health education program and to reduce the occurrence of dental diseases among industrial men-workers in Korea. The questionaire and dental examination were given to 782 industrial men-workers who visited Asan Medical Center for the purpose of health examinations in 2000. The obtained results were as follows; 1. According to the results of logistic regression analysis, both ages (especially under 30's: P=0.027) and monthly incomes (especially under 1,000,000 won: P=0.000) show negative relationships with the occurrence of dental caries. 2. As the results of logistic regression analysis, ages shows positive relationship and monthly incomes shows negative relationship (only under 1,000,000 won: P=0.059) with the occurrence of missing teeth. 3. According to the results of logistic regression analysis of periodontal disease, the model shows no significance (P=0.117). 4. As the results of logistic regression analysis, both monthly incomes and ages show positive relationships with the occurrence of abrasion.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.3
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• pp.168-175
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• 2020

Purpose: The purpose is to test and evaluate the physical properties of commonly used temporary restoration materials and newly emerged materials. Materials and Methods: Four groups of polymer materials were evaluated: Polymethyl methacrylate (PMMA) 2 groups, Polyetheretherketone (PEEK), Polycarbonate. Four physical properties were tested: surface hardness, bending strength, abrasion resistance during wear, wear behavior. The 3-axis bending strength and Vickers hardness test were measured using a universal testing machines respectively. The microstructure was observed with a scanning electron microscope and weight comparison was evaluated after 100,000 chewing tests using a chewing simulator. Kruskal wallis test was performed to evaluate statistical significance. Results: The four groups showed the highest flexural strength and Vickers hardness of PEEK, followed by PC, PMMA-H, PMMA-T. Microstructure observation also showed the least surface roughness in the PEEK group, followed by PC, PMMA-H, PMMA-T. Conclusion: PC is considered to have sufficient mechanical properties that can be applied to the manufacture of temporary teeth. However, further studies, such as biocompatibility, are considered to be necessary for practical clinical applications.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.3
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• pp.234-244
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• 2023

Tooth wear refers to the loss of dental hard tissue caused by various physiological and pathological causes, and excessive pathological wear can cause complications such as pathological changes in dimensions, occlusal disharmony, loss of function, and aesthetic problems. The cause of tooth wear can be caused by attrition, abrasion, corrosion and abfraction, and it is known to act in a multifactorial etiology in interocclusal activity. In patients with excessive pathological wear, it is important to determine whether or not the vertical dimension of occlusion is reduced, and complete oral rehabilitation should be achieved with the adaptation of the neuromuscular and temporomandibular joint through accurate diagnosis and analysis. The patient in this case was a 63-year-old male patient, who presented discomfort to cold beverage due to severe tooth wear. After analysis of the patient's vertical dimension of occlusion, a full mouth rehabilitation was performed with increasing vertical dimension of occlusion. The goal of treatment was to improve the occlusal plane with the equal-intensity contact of all teeth, harmonious anterior guidance and immediate disclusion of all posterior contacts. After rehabilitation, the patient was satisfied with function and esthetic appearance.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.555-563
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• 2004

The pH of beverages is known to be low and have, therefore, been implicated in the increasing incidence of erosion. Erosion is believed to be the predominant cause of teeth wear in children and young adults, although there will always be a contribution from attrition and abrasion. The aim of the present study was to evaluate the effect of yogurt on the progression of erosive demineralization in human enamel using demineralization model in vitro. In 4 yogurts, available on the market, pH, buffering capacity and the concentrations of calcium, phosphate and fluoride were determined. The buffering effect was determined by titration with NaOH. 50 milliliters of each drink was then titrated with 1M sodium hydroxide, added in 0.5 milliliters increments, until the pH reached about 7. Human deciduous enamel(n=40) samples were divided into four groups and exposed to 80ml of the yogurt for 30,60, 90 and 120min. Enamel surface microhardness(VHN) was examined before and after each exposure. 1. The average PH of fermented milk was 3.77 and this pH value was acidic enough to cause tooth erosion. 2. All of the fermented milks were found to be erosive(p<0.05) 3. The teeth exposed to the fermented milk all showed erosion like lesions and microhardness measurements showed that enamel surface hardness decreased proportionately with increased time of immersion in all tooth specimen groups. 4. After immersion for 30 and 60 minutes, reduction rate of microhardness values was not significantly different between the groups(p>0.05). However, after 90 and 120 minutes, reduction rate of each group was significantly different(p<0.05).

• The korean journal of orthodontics
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• v.36 no.2 s.115
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• pp.114-124
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• 2006

The purpose of this study was to evaluate the tooth color changes of resin bonding sites and their adjacent sites on orthodontic bracket bonding. Sixty extracted sound premolars were used and the tooth color was recorded according to the CIE $L^*a^*b^*$ color system using a spectrophotometer. The tooth colors of the twenty premolars were measured and compared before bracket bonding and after removal. On a further twenty premolars, the tooth color was measured before and after only primer application. In the change of $L^*$ values, according to the bracket bonding and primer application, the lightness was decreased, and in the change of $a^*\;and\;b^*$ values, the color was changed into a more yellowish color The color differences $({\Delta}E^*)$ were calculated from the $L^*a^*b^*$ values and compared with the standard value of clinical detection $({\Delta}E^*=3.7)$. The color differences between before the bracket bonding and after removal noted exceeded the standard value and those of between before and after the primer application were not larger than the standard value. Toothbrushing was performed after application of the primer to evaluate the color changes according to the primer abrasion. As a control, toothbrushing was performed on the last twenty premolars. The color differences noted were larger than the standard value after toothbrushing. Also, to evaluate the color changes of the tooth which is exposed to sun irradiation after bracket removal, additional photoaging was performed and the color was measured for all teeth. The additional color differences after photoaging were smaller than the standard value. The above results suggest that the tooth color changes after fixed orthodontic treatment.