Chong-Chul Kim

Effect of curing method and curing time on the microhardness and wear of pit and fissure sealants

OBJECTIVE To evaluate the effects of a light source, polymerization time and storage time on the microhardness and wear of pit and fissure sealants. METHODS Five commercial pit and fissure sealants (Fissurit F [FF], Teethmate F1 [TF], Apollo Seal [AS], Concise [CC], and Ultraseal XT Plus [US]) were used. Specimens were cured with a conventional visible light curing unit (Curing Light XL 3000) for 10, 20, 30, 40s or with a plasma arc light curing unit (Apollo 95E) for 3, 6, 9, 12s. The specimens were kept dry in light-shielded bottles at 37 degrees C for 1 week, then half of them were thermocycled. The rest of them were stored in distilled water in light-shielded bottles for another 30 days, which were kept in an incubator at 37 degrees C, followed by thermocycling. Microhardness and wear of the specimens were measured. RESULTS Similar degree of microhardness was achieved with the shorter curing time with the plasma arc light curing unit as with the conventional visible light-curing unit. With conventional visible light curing, the microhardness of the top surface was higher than that of the bottom surface (P<0.05). With plasma arc light curing, the microhardness of the top surface was higher than that of the bottom surface for AS and CC, but for FF, TF and US, the microhardness of the top surface was lower than that of the bottom surface, except in the 3-s curing of US. For FF, AS, CC and US, wear in the 6s curing with plasma arc light was similar to or less than that of the 30s curing with conventional visible light, but for TF, wear of the 9s curing with plasma arc light was similar to that of the 20s curing with conventional visible light. After storage in distilled water for 30 days followed by thermocycling, there was a tendency towards a decrease in microhardness and an increase in wear. There was a significant negative correlation between microhardness and wear (P<0.01). SIGNIFICANCE The tested curing methods differed significantly in their curing capacity. This study suggested that a plasma arc light curing unit needs shorter curing time than a visible light curing unit to achieve similar mechanical properties of the pit and fissure sealants tested.

IMPACTION OF PRIMARY TEETH ASSOCIATED WITH ODONTOMA: CASE REPORTS

Odontomas generally appear as small, solitary, or multiple radio-opaque lesions found on routine radiographic examinations. It is a comparatively common odontogenic tumor, and may lead to interfere with the eruption of its associated tooth. In general, odontomas occur more often in permanent dentition and are very rarely associated with primary teeth. This report deals with five rare cases of primary teeth impaction associated with odontomas, with spontaneous eruption occurring in all five cases after simple surgical removal of the odontoma. Impacted primary teeth may be associated with defects in development and eruption of their permanent successors, and thus long-term observation is necessary until the permanent successors erupt.

A STUDY OF NEW-PATIENT DISTRIBUTION AND THE MOTIVES FOR VISITING IN THE DEPARTMENT OF PEDIATRIC DENTISTRY AT SEOUL NATIONAL UNIVERSITY DENTAL HOSPITAL

The number of patients requesting services of pediatric dental clinics has been steadily increasing in South Korea. The pediatric dental clinics are comprised of hospital-based clinics and local clinics. The purpose of this study was to analyze new-patient distribution and to survey the motives for visiting the department of pediatric dentistry at Seoul National University Dental Hospital(SNUDH), utilizing questionnaires for parents from May to July 2010. The results are as follows: 1. Age distribution showed that 0-3 year-olds formed the largest group of 29.3%. The average age of patients was 6.2 years old. 2. In the surveys for the parents, the major reason for visiting SNUDH was the referral from other clinics(30.6%). 3. The 75% of patients previously visited other clinics before visiting SNUDH. 1) The greater number of patients(52%) visited general practitioners clinic than pediatric specialists(48%). 2) More than 90% of the patients visited SNUDH after visiting other clinics for reassuring diagnosis and referrals. 3) The crucial deterring factor of being treated at SNUDH was difficult accessibility.

The influence of Lactobacillus rhamnosus GG on the binding ability of Streptococcus mutans

Probiotics has currently attracted for means of preventive treatment measurement instead of using non-specific and broad spectrum antimicrobials. In previous studies, two main probiotics species, Lactobacillus and Bifidobateria, showed the reduction of DMFS and S. mutans counts. However, the timing of introducing probiotic species to oral cavity is not clear. The aim of this study is to evaluate the changes of binding ability of S. mutans in various concentrations and inoculation time of L. rhamnosus GG. Adding the following concentration of L. rhamnosus GG, CFU, CFU and CFU, to S. mutans medium demonstrates significant reduction of S. mutans counts. Additionally, more reduction was observed when L. rhamnosus were inoculated prior to S. mutans or simultaneously inoculated compared to when S. mutans were inoculated prior to L. rhamnosus after 3 hours of incubation. Based on this research, the timing of introducing probiotics should be considered when probiotics are utilized as a preventive treatment measurement.

TREATMENT OF TOOTH DISCOLORATION ASSOCIATED WITH TRIPLE ANTIBIOTIC THERAPY: CASE REPORTS

The concept of revascularization of necrotic pulps regained interest and became an alternative conservative treatment option for young permanent teeth with immature roots. Revascularization of immature teeth with apical periodontitis depends mainly on disinfection of the canal. Since the infection of the root canal system is considered to be polymicrobial, a combination of drugs would be needed to treat the diverse flora. A triple antibiotic mixture of metronidazole, ciprofloxacin, and minocycline was used as an intracanal medicament. However, discoloration was developed after applying the triple antibiotic mixture. It is believed that the marked discoloration is related to the use of minocycline. The aim of this article was to present cases of coronal discoloration after triple antibiotic therapy in immature tooth and was treated with bleaching technique to control coronal discoloration. In conclusion, revascularization by using triple antibiotics promotes a paradigm shift in treating endodontically involved permanent teeth. However, we should understand that triple antibiotics containing minocycline induces tooth discoloration. Further research to prevent coronal discoloration should be investigated and suggested for the safe use of triple antibiotics.

The Simple Regression Model of Gonial Angles : Comparison between Panoramic Radiographs and Lateral Cephalograms

The aim of this study was to enhancing the panoramic radiograph’s clinical use for assessing mandibular measurements and formulating a function of those measurements from panoramic radiographs and lateral cephalograms in children. The panoramic radiographs and lateral cephalograms of 99 former orthodontic patients with skeletal class III malocclusion were selected. In each radiograph, gonial angles, ramus heights, and distance between lower incisors and symphysis were measured. The values of the studied parameters were compared by paired t-test, Pearson’s correlation test and regression analysis. The mean value of the gonial angle in panoramic radiographs was 125.49°, and the value in lateral cephalograms was 127.50°. The Pearson’s correlation coefficient (ρ) between mean values of gonial angle in each radiograph was 0.945 (p < 0.001). The relationship between the gonial angle measurements obtained from each radiographs was represented as ‘Gonial angle (Lateral cephalograms) = 0.920 X Average gonial angle (Panoramic radiographs) + 12.072’ in the linear function. The coefficients of ramus heights, and distance between lower incisors and symphysis portrayed weaker correlations than gonial angles. A panoramic radiograph could be used to determine the gonial angle as accurately as a lateral cephalogram, and each gonial angle showed a strong positive relation. A panoramic radiograph is a useful tool for examining vertical growth pattern of patients, as well as a lateral cephalogram.

MESIODENS EXTRACTION OF A PATIENT WITH ROBINOW SYNDROME UNDER GENERAL ANESTHESIA

Robinow syndrome is skeletal dysplasia with both autosomal dominant and recessive inheritance patterns. It is characterized by short-limbed dwarfism, abnormalities in the head and face, as well as vertebral segmentation. A 2-year-7-month old boy with Robinow syndrome had visited Seoul National University Dental Hospital, for the evaluation of tooth palatal eruption on maxilla. He had micrognathia, delayed tooth eruption, cleft lip with bifid uvula. He also had an erupted mesiodens on the palatal side of maxillary primary incisors, which was tuberculated and 8mm in major diameter. The patient was scheduled for mesiodens extraction under general anesthesia. He was a young child with delayed development, so general anesthesia was inevitable. General anesthesia was induced and maintained with inhalation agent, Sevoflurane. There were no postoperative complications related to anesthesia and dental treatment. Robinow syndrome patients have craniofacial dysmorphism and eruption disorders. Therefore, he requires regular check-ups as well as dental managements. [J Korean Dis Oral Health Vol.12, No.1: 1-5, June 2016]

DENTAL CARIES TREATMENT IN FEEDING PROBLEM PATIENT WITH CONGENITAL ESOPHAGEAL ATRESIA : A CASE REPORT

Esophageal atresia is the abnormal development of the esophagus that connects the mouth to the stomach. This birth defect results in the incomplete connection of the esophagus to the stomach causing an inability to swallow properly and breathing difficulties. Surgery is the only treatment for esophageal atresia. Patients undergone an esophageal reconstruction usually suffer from gastroesophageal reflex. A 5-year old boy with congenital esophageal atresia and Sciwitar syndrome visited Seoul National University Dental Hospital because generalized excessive loss of tooth structure. The patient had history of multiple operations for reconstruct esophagus. He had little food intake experience thought oral and had difficulty to swallowing. The patient was generalized severe erosive and decayed state. For patient, the dental procedure under general anesthesia was scheduled due to the multiple caries with erosion and poor cooperation. Under general anesthesia, pulpectomy and restoration as well as extraction was performed. Gastroesophageal reflex is potentially serious condition, with various extraesophageal adverse effects such as dental erosion. To prevent progression of dental caries, dietary counselling and oral hygiene instruction should be reinforced. Also, restorations to erosive teeth will maintain esthetics and function and preserve pulp vitality. [J Korean Dis Oral Health Vol.12, No.1: 6-10, June 2016]

Analysis of Photoplethysmographic Waveform for Assessment of Pulpal Blood Flow in Children

The purpose of this study was to analyze photoplethysmographic waveforms from pulse oximeter using raw data of red and infrared light and investigate the reference values of parameters (Height, Width50, Maximum slope, Minimum slope, Area) for evaluating pulpal blood flow in maxillary central incisors with normal pulp vitality in children. The study was performed in 30 pediatric patients, aged 7-16 years old, using pulse oximeter (MEKICS Co., Ltd, Korea) combined with a custom-made sensor. The raw data was obtained and recorded by custom-made software and analyzed by LabChart (v.7.3, ADInstruments, Germany) offline. In this study, we analyzed photoplethysmographic waveforms from pulse oximeter applied to maxillary central incisor for assessment of pulpal blood flow and suggested several reference values of young permanent maxillary central incisor with normal pulp. On average, the waveform of red light was higher, stiffer and wider than that of infrared light. Future studies about reference values for other normal teeth and the teeth with impaired pulp vitality are needed.

Effects of Polishing Methods on the Surface Characteristics of Composite Resins

The aim of this study was to evaluate the surface characteristics of composite resins polished with two different polishing methods. 30 disk-shaped specimens were prepared with microhybrid (Filtek Z250) and nanofilled (Filtek Z350) resins respectively, and classified into three groups: not polished as controls, polished by an abrasive disk (Soflex), and polished by a polishing brush (Occlubrush). Surface roughness was increased after polishing. In terms of micro-roughness, there were no significant differences between the two polishing methods. But macro-roughness values were markedly increased in the Occlubrush group (p < 0.05). In the Sof-lex group, the matrix and fillers were polished together, resulting into a smoother and homogeneous surface. However, in the Occlubrush group, the matrix layer was torn off, with more heterogeneous surfaces and large scratches. In regards to micro-hardness, no significant differences were observed between the two polishing systems (p > 0.05). And the hardness value increased about 25% after polishing. In conclusion, the method of polishing should be chosen deliberately in view of the hardness characteristics of composite resins. Sof-lex is recommended to improve the surface characteristics of polished resins.