In vitro wear behavior between enamel cusp and three aesthetic restorative materials: Zirconia, porcelain, and composite resin

PURPOSE: The aim of this study was to identify the effects of three aesthetic restorative materials on the wear between tooth and restoration by a pin-on-disk manner. MATERIALS AND METHODS: Six aesthetic restorative materials were used to prepare disk specimens for wear test, which were Lava Zirconia as zirconia group, Vintage MP and Cerabien ZR as veneering porcelain group, Gradia Direct microhybrid composite containing prepolymerized fillers, Filtek Z250 microhybrid composite containing zirconia glass and colloidal silica particles, and Filtek Z350 nanocomposite as composite resin group. Vertical loss of the worn cusp, change of the surface roughness of the restoration materials, and the surface topography were investigated after wear test under 9.8-N contact load. RESULTS: The porcelain groups (Vintage MP and Cerabien ZR) caused the largest vertical loss of teeth when compared with those of the composite resin and zirconia groups, and Filtek Z250 microhybrid composite results in the second-largest vertical loss of teeth. The surface of Filtek Z350 nanocomposite was deeply worn out, but visible wear on the surface of the zirconia and Gradia Direct microhybrid composite was not observed. When the zirconia surface was roughened by sand-blasting, vertical loss of teeth considerably increased when compared with that in the case of fine polished zirconia. CONCLUSION: It was identified that microhybrid composite resin containing a prepolymerized filler and zirconia with reduced surface roughness by polishing were the most desirable restorative materials among the tested materials to prevent the two-body wear between aesthetic restorative material and tooth.

A study on the change of root surface irradiated by Er:YAG laser / 대한치주과학회지

This study was performed to evaluate the usability of Er:YAG laser for periodontal therapy. Forty dental root slabs (5x5x2mm3) were prepared from human periodontally diseased extracted teeth and grouped into 4 groups: 1) control (root planing only), 2) root planing and irradiated with laser at 30mJ, 3) root planing and irradiated with laser at 60mJ, and 4) root planing and irradiated with laser at 100mJ. The root slabs were embedded in resin block before laser treatment. Er:YAG laser was irradiated under water irrigation with the tip held perpendicular to the root surface in contact mode. After Er:YAG laser irradiation or planing on the root surface, morphological changes have been observed under SEM, and the micro-hardness and Ca/P ratio were compared. 1. In the control group, the root surface showed and the presence of smear layer, the directional change caused by root planing instrumentation and no exposure of dentinal tubule was observed. Laser irradiated group showed surface changes with rough dentin surface of niche and depression and dentinal tubule exposure by the elimination of smear layer. 2. The micro-hardness of root surface in the laser irradiated group, was higher than the control group. The higher energy output was applied, the higher micro-hardness on root surface was resulted. 3. The higher energy output was applied, the higher Ca/P ratio was observed. The higher Ca/P ratio in 60mJ group and 100mJ group was statistically significant, compared to the control group and the 30mJ group. These results suggest that Er:YAG laser irradiation on the periodontally diseased root surface could remove smear layer and increase the micro-hardness on root surface and Ca/P ratio which contribute to enhance the acid resistance of periodontally treated root surface.

Effects of Er:YAG Laser Irradiation on Removal of Subgingival Calculus / 대한치주과학회지

The purpose of this in vitro study was to evaluate the efficiency of Er:YAG laser on calculus removal and the morphologic changes and hardness of the irradiated surface at different power settings. This experiment used human teeth which were extracted due to periodontal disease and had a band of calculus. Forty root slabs (5x5x2mm3) were made and divided into control group and irradiated groups. Experimental groups were as follows; Control group (root planing), Group 1 (irradiated with laser at 30mJ), Group 2 (irradiated with laser at 60mJ), Group 3 (irradiated with laser at 100mJ). Twelve root slab embedded in resin block were used in each group. Er:YAG laser was applied under water irrigation with the tip held perpendicular to the root surface in contact mode. The treatment time was measured until the calculus was removed completely under naked eyes. The efficiency of calculus removal was evaluated by the time for removal. Morphological changes of laser irradiated site were observed under SEM and the surface hardness was measured using a Vickers Hardness tester. The results were as follows; 1. The efficiency of laser scaling was increased with increasing the energy level of irradiation(p<0.05). 2. The morphological changes such as carbonization, crater and scale-like defects in the irradiated root surface were frequently observed with increasing the energy level. 3. The surface hardness increased at 60mJ and 100mJ irradiated groups than that of control group(p<0.05). From the results evaluting on the efficiency, morphological change and surface hardness, appropriate lower energy level was suggested for the clinical application of the Er:YAG laser in scaling.

A Clinical Statistics on the Offending Allergens of Allergic Rhinitis / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The kinds of offending allergens in our environment have changed in accordance with the changes wrought in the living environment. Thus, the study of offending allergens in allergic rhinitis is important. This study attempted to find out annual and seasonal distribution of offending allergens in patients of allergic rhinitis and to investigate the common offending allergens. MATERIALS AND METHODS: A series of allergic skin tests were performed for 3,159 allergic rhinitis patients from Jan. 1981 to Jun. 1990 at the allergic clinic, St.Benedict Hospital, Pusan, Korea, and the results were reviewed. The allergic study included 1) an allergic skin test, 2) a nasal smear for eosinophil. RESULTS: The following summary shows the results of this study: 1) The ratio between male and female of allergic rhinitis patients was 1.15:1 with the peak age being the teens and the twenties (60.6%). 2) The peak season of allergic rhinitis was winter (29.6%), followed by autumn, spring and summer. 3) The common offending allergens were dust and mites (35.9%), pollens (31.2%), epithelials (24.8%). 4) The most common offending allergen was D. farinae (52.5%), followed by D. pteronyssinus, cat fur, Alder pollens and Hazel pollens. 5) 29.6% of patients reacted positive to the skin tests for perennial types of allergens only and 5.2% of patients demonstrated pure pollinosis. CONCLUSION: The most common offending allergen was found to be the dust mite, and the most common pollen was from Alder trees. Perennial types of allergic rhinitis exceeded seasonal types in their occurence.

Roentgenographic Study of the Upper Airway in Patients with Obstructive Sleep Apnea Syndrome / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Using sophisticated imaging techniques, such as x-ray cephalometry, computed tomography, and magnetic resonance imaging, we found obstructive sleep apnea patients to have smaller upper airways than nonapneic individuals. The purpose of this study was to examine whether a simple test, such as routine roentgenographic views of the upper airway, is useful in identifying anatomic narrowing of the airway in patients with sleep apnea. MATERIALS AND METHODS: We carried out a prospective study of a group of 30 patients (28 male and 2 female subjects) referred for evaluation of heavy snoring and possible obstructive sleep apnea. All patients had full nocturnal polysomnography and the lateral views of their airways were used to measure the pharyngeal diameters at three sites along the airway. All measurements were performed with the patients positioned both upright and supine. RESULTS: We observed that obstructive sleep apnea patients maintained significantly lower the retropalatal distance in the supine position than in the upright position. CONCLUSION: We concluded that routine roentgenographic measurements of upper airway diameters are useful screening methods for patients suspected of having sleep apnea.

A Clinical Analysis of Peritonsillitis / 대한이비인후과학회지

BACKGROUND: Peritonsillitis is a clinical condition of gross tonsillar infection in a septic patient with localized swelling in the peritonsillar region, and which encompasses both peritonsillar abscess and cellulitis. It is not rarely experienced in spite of decreasing incidence since the advent of antibiotic therapy. OBJECTIVES: Our objective was a clinical observation of many factors in relation to peritonsillitis. MATERIALS AND METHODS: A clinical observation was performed on 40 cases with peritonsillitis, who visited St. Benedict hospital during 3 years from February 1994 to March 1997. A needle aspiration was attempted at the point of maximum bulging using a 10cc syringe with an 18-gauge needle. RESULTS: Among 40 cases, 23 cases yielded pus. From those 23 cases, we could isolate 22 strains in 20 cases. Incision and drainage was performed only in cases of aspiration of pus(23 cases). There was no significant difference in duration of hospitalization between I & D group(7.17 days) and non-I & D group(6.71 days)(p>0.05). CONCLUSION: We conclude that I & D can't reduce the duration of hospitalization even though I & D is helpful for the relief of symptoms, and the adequate use of antibiotics is important for the treatment of peritonsillitis.