• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.546-559
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• 1997

The purposes of this study were to evaluate the efficiency of cavity preparation and to determine the incidence of tooth crack when root-end retrograde cavity preparation was done with ultrasonics. 91 distobuccal root-ends of extracted human maxillary first molars were cut by 3 mm perpendicularly to the long axis of tooth using a slow speed diamond saw, retrocavities were prepared using a slow-speed no. 2 round bur as controls, and stainless steel ultrasonic tips of power settings of 1 through 10 as experimentals. Time consumed and the number of strokes used for the cavity preparation were measured and evaluated, and the incidence of tooth cracks was observed under a stereomicroscope. The results were as follows : For the retrograde cavity preparation, time and number of strokes used were decreased as the ultrasonic power setting increased (p<0.001). High power setting of ultrasonics induced significantly more tooth cracks than did the slow-speed bur or low- and medium power setting of ultrasonics (p<0.05). Teeth with previous crack induced significantly more tooth cracks than those without previous one when high power setting of ultrasonics were used for the retrograde cavity preparation (p<0.001). Teeth with initial apical canal size of no. 10 induced significantly more crack than did those with size of no. 15 when low power setting of ultrasonics were used for the retrograde cavity preparation (p<0.05).

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.1
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• pp.144-150
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• 2008

Multimodal cancer therapy including surgery, chemotherapy, and radiotherapy could not only improve the prognosis of malignancy but also reduce the dosage and toxicity of cancer drug for treatment of malignant tumor. The effects of radiotherapy are generally localized, additive, and accumulative, and depend on dosage, site and cell sensitivity. However, in growing individuals, the dental and skeletal sequelae to radiotherapy result in dental or facial abnormalities that are irreversible : arrested root development, disturbances in enamel formation, microdontia, anodontia, altered tooth eruption and mandibular or maxillary hypoplasia. Especially, the teeth which are developing is affected according to the stage. We report three cases of developmental disturbance of permanent teeth after radiotherapy. These children had received radiotherapy for malignant tumor at the age of 3 to 4 years, in which root hypoplasia, short tapered root and early apex closure were observed. For the management of radiation caries and radiotherapy-related teeth, periodic recall check and oral hygiene instruction are required.

• Journal of the korean academy of Pediatric Dentistry
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• v.38 no.3
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• pp.290-295
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• 2011

During tooth formation, tooth development can be affected by physical action or metabolic changes around dental follicle. Especially trauma to primary dentition is the most representative physical factor that can cause development disorders of succedaneous tooth. Enamel hypoplasia and crown discoloration of succedaneous tooth are common complications of trauma. And impaction, ectopic eruption, arrest of root formation and root dilaceration of succedaneous tooth are rare. In this case, a 6-year and 5-month-old female patient visited for dental evaluation after trauma. She was diagnosed with alveolar bone fracture near upper front teeth, extrusion of the upper right and left primary central incisors, intrusion of the upper right primary lateral incisor, and palatal luxation of the upper left primary lateral incisor. Upper right and left primary central incisors with severe mobility were extracted, with gingival suture on the day of the visit. During 24 months check up, root dilacerations were found near the cemento enamel junction in the upper lateral incisors and arrests of root formation were found on the coronal 1/3 of the root in the upper central incisors. Although alveolar bone fracture is rare type of trauma in children, a thorough examination of alveolar bone is essential for prognosis and following treatment in patients with trauma.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.1
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• pp.108-112
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• 2000

Hypophosphatemic rickets is lack of reponse to physiologic doses of vitamin D, different from the vitamin D-dependent rickets. It is inherited in an X-linked dominant fashion. The prime features of this disorder are lowered serum phosphate levels, elevated serum alkaline phosphatase and normal serum calcium levels. The dental manifestation often include apical radiolucencies, abscess and fistulas of clinically sound teeth. Dental radiographs show ricketic bone trabeculations, abscent or abnormal lamina dura and abnormal cementum. This case which was diagnosed to hypophosphatemic rickets, showed multiple spontaneous periapical abscess and gingival fistula enlarged pulp chambers, extension of the pulp horns into the cusp tips and delayed eruption.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.2
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• pp.335-340
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• 2007

Primary teeth and the permanent successor must be understood as interdependent units, where each one of them interacts with and depends upon the other. The spread of pulpal inflammation in primary teeth to the periradicular tissues can lead to early eruption, enamel hypoplasia or hypocalcification, developmental arrest of permanent successor. Also the periapical inflammation cause permanent tooth displacement in various direction. We describe here two clinical cases of displaced permanent successor caused by periapical lesion of mandibular primary molar in children.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.54-67
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• 1998

The purposes of this study were to evaluate the efficiency of dentin cutting and root-end cavity preparation, and to determine the incidence of tooth crack when root-end retrograde cavity preparation was done with. ultrasonic diamond instruments. To evaluate the efficiency of dentin cutting, ultrasonic diamond and stainless steel instruments were applied to 20 exposed bovine dentin surfaces perpendicularly or parallely at the low, and medium power settings for 1 minute ($Miniendo^{TM}$, EIE, CA, U.S.A.). The resultant cavity depth was measured. To evaluate the efficiency of cavity preparation and to investigate the incidence of tooth crack, 165 mesiobuccal, distobuccal and palatal root-ends of extracted human maxillary first molars were resected by 3 mm perpendicularly to the long axis of tooth using a slow speed diamond saw after root canal preparation and filling. Retrocavities were prepared using a ultrasonic diamond instrument or a stainless steel one of the low- or medium power settings of 2 or 6. Time consumed and the number of strokes used for the cavity preparation were measured and the incidence of tooth cracks was evaluated under a stereomicroscope. The results were as follows: Both at the low and medium power settings, and both with perpendicularly- and parallely applied tips to dentin, diamond instruments showed higher dentin cutting efficiency than stainless steel ones did (p<0.01). When tips were applied to dentin perpendicularly, both diamond instrument and stainless steel one showed higher cutting efficiency with medium power setting than with low power one (p<0.01). Both at the low- and medium power settings, both diamond instrument and stainless steel one showed higher cutting efficiency when tips were applied perpendicularly to dentin surface than applied parallely (p<0.01). At the medium power setting, the number of stroke and time consumed were less with diamond instrument than with stainless steel one (p<0.05) for the retrograde cavity preparation. At the low power setting, diamond instrument induced less tooth cracks than stainless steel one did (p<0.01).

• Restorative Dentistry and Endodontics
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• v.36 no.4
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• pp.290-299
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• 2011

Objectives: The usage of fluoride varnish for a moderate to low caries-risk group has not been well validated. This study aimed to evaluate the preventive and therapeutic efficacies of fluoride varnish on the initiated root caries. Materials and Methods: Ten premolars were sectioned into quarters, further divided into two windows, one of which was painted with Fluor Protector (1,000 ppm fluoride, Ivoclar Vivadent). An initial lesion with a well-preserved surface layer was produced by pH cycling. Scanned line analysis using energy dispersive spectrometry determined the weight percentages of Ca and P in the demineralized layer. Scanning Electron microscopy and confocal laser scanning microscopy (CLSM) evaluated the varnish-applied root surfaces. Results: The mean lesion depth (SD) was 12.3 (2.6) ${\mu}m$ (single cycling) and 19.6 (3.8) ${\mu}m$ (double cycling). Double cycling extended the lesion depth, but induced no more mineral loss than single cycling (p < 0.05). The mean weight percentages of Ca and P between groups with and without varnish were not significantly different (p < 0.05). A CLSM showed varnish remained within 15 ${\mu}m$ of the surface layer. Conclusions: When a mild acid challenge initiated root tissue demineralization, the application of low-concentration fluoride varnish did not influence the lesion depth or the mineral composition of the subsurface lesion.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.2
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• pp.255-260
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• 2001

Trauma to the primary incisors may cause developmental or eruptional disturbance of the permanent successors. Two cases illustrate developmental disturbances of arrested root formation, dilaceration, and eruptional disturbances of impaction, ectopic eruption of permanent successors caused by traumatic injury to deciduous incisors. The patient of the first case suffered trauma at the age of 4 years 7 months, causing alveolar bone fracture including the maxillary right primary central and lateral incisors that were immedi-ately extracted. The second patient had trauma episodes at the age of 3 years. Avulsion of the maxillary primary right central and lateral incisors were occurred due to trauma. After such trauma, regular follow-up including radiographs is necessary to detect early any possible interference with normal eruption of permanent successors.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.2
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• pp.224-228
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• 2005

The effect of primary tooth infection on permanent teeth was reported by many previous study. It is seen histologic change in the enamel forming organ and in the surrounding sac, thus produce the defect as either hypoplasia or hypocalcification and alter the eruption of the permanent teeth. The periapical inflammation cause permanent tooth displacement in various direction and can be classified into the three categories : rotation, deflection inversion. This study reported case which displacement of succedaneous teeth may be caused by periapical infection of primary dentition and concluded that treatment procedure of infected primary tooth is selected and performed by importance to retain the tooth for space maintain, possibility to successfully restored, evidence of abnormal development of the succedaneous tooth.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.4
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• pp.607-612
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• 2009

The malignant tumor in childhood is one of the main causes of children s death due to disease. The traditional treatment for the malignancy is known for the radiation therapy and the chemical therapy or both. However, the treatments tend to induce intraoral complications. Different from adults, almost all children on cancer therapy are expected to have dental complications, because their permanent teeth are on the developmental stage. The degree of dental complication depends on the patient's age, type of chemical and other factors-radiation dose and frequency. In this report, 3 children who had experienced the anti-cancer therapy on their age between 1 and 4 years were selected and dental complications were examined. The children have chance for the various oral complications including the developmental problems such as agenesis, microdontia and hypoplasia of the teeth. Therefore, it's important to understand the side-effects of anticancer therapy during the permanent teeth had been developmental stage in young patients. Also, oral health care specialists, including pediatric and hospital dentist can support the oncology team by providing basic oral care, implementing oral care protocols, delivering emergency dental treatment undergoing anticancer treatment.