• Journal of the korean academy of Pediatric Dentistry
• /
• v.40 no.2
• /
• pp.127-132
• /
• 2013

Traumatic injuries to immature permanent teeth are common and the results can be destructive. Although Hertwig's epithelial root sheath is usually sensitive to trauma, it may resist damage from trauma thereby retaining its vitality and continuing to calcify a root under favorable conditions. This case report describes two cases of trauma to immature permanent incisors. The first case presents an avulsed maxillary central incisor which has been replanted. The other case shows completely avulsed mandibular central incisors which have not been replanted. However, both cases subsequently show continued growing roots separated from the main roots. This report highlights the ability of the immature pulp tissue to continue to form dentin and the robustness of Hertwig's epithelial root sheath to initiate root development despite a traumatic injury.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.30 no.4
• /
• pp.715-721
• /
• 2003

Dental injuries with crown fracture occur frequently, especially in young patient Reattachment of the crown fragment has been shown to yield good esthetic results in that original tooth anatomy is restored with a material that abrades at a rate indntical to that of the adjacent tooth substance and at the same time permits continual monitoring of pulpal status through the fragment. Case 1 was complicated crown fracture with pin-point bleed ing, that was treated by direct pulp capping with calcium hydroxide and fragment reattachment. Case 2 was in trusive luxation with complicated crown fracture and was treated by pulp treatment and fragment reattachment. Case 3 was uncomplicated crown fracture, and fracture line involved slightly biologic width and treated by reattachment of the crown fragment.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.36 no.2
• /
• pp.305-309
• /
• 2009

Dens evaginatus is a dental anomaly most commonly seen in premolar teeth in which a tubercle or protuberance projects from either the center of the occlusal surface or the buccal triangular ridge. These tubercles are easily fractured from mastication as the tooth erupts and frequently leads to pulp necrosis as a common complication. To prevent these sequelae, prophylactic treatment soon after the tooth starts erupting is essential. These preventive treatments include, selective grinding and protection of the tubercle by pit and fissure sealant. When the tooth does shows signs of pulp necrosis and apical periodontitis, endodontic procedures are needed. Apexification and apexogenesis are usually the treatment of choice for the affected teeth which have immature apices. Apexogenesis is a vital pulp therapy procedure performed to encourage continued physiological development and formation of the root end. It involves removal of the inflamed pulp and the placement of calcium hydroxide on the remaining healthy pulp tissue. This case report describes an atypical apexogenesis of a mandibular premolar which showed to be a dens evaginatus. The tooth which was treated with calcium hydroxide shows good results and is planned for permanent root canal filling.

• Restorative Dentistry and Endodontics
• /
• v.36 no.5
• /
• pp.425-430
• /
• 2011

Objectives: This in vitro study investigated whether short-term application of calcium hydroxide in the root canal system for 1 and 4 wk affects the fracture strength of human permanent teeth. Materials and Methods: Thirty two mature human single rooted mandibular premolars in similar size and dentin thickness without decay or restorations were hand and rotary instrumented and 16 teeth vertically packed with calcium hydroxide paste and sealed coronally with caviton to imitate the endodontic procedure and the other 16 teeth was left empty as a control group. The apicies of all the samples were sealed with resin, submerged in normal saline and put in a storage box at $37^{\circ}C$ to mimic the oral environment. After 1 and 4 wk, 8 samples out of 16 samples from each group were removed from the storage box and fracture strength test was performed. The maximum load required to fracture the samples was recorded and data were analysed statistically by the two way ANOVA test at 5% significance level. Results: The mean fracture strengths of two groups after 1 wk and 4 wk were similar. The intracanal placement of calcium hydroxide weakened the fracture strength of teeth by 8.2% after 4 wk: an average of 39.23 MPa for no treatment group and 36.01 MPa for CH group. However there was no statistically significant difference between experimental groups and between time intervals. Conclusions: These results suggest that short term calcium hydroxide application is available during endodontic treatment.

• Restorative Dentistry and Endodontics
• /
• v.31 no.2
• /
• pp.96-102
• /
• 2006

There are various factors affecting the fracture of NiTi rotary files. This study was performed to evaluate the effect of cross sectional area, pecking motion and pecking distance on the cyclic fatigue fracture of different NiTi files. Five different NiTi $files-Profile^{(R)}$ (Maillefer, Ballaigue, Switzerland), $ProTaper^{TM}$(Maillefer, Ballaigue, Switzerland), $K3^{(R)}$ (SybronEndo. Orange, CA) , Hero $642^{(R)}$ (Micro-mega, Besancon, France), Hero $Shaper^{(R)}$ (Micro-mega, Besancon, France)-were used. Each file was embedded in temporary resin, sectioned horizontally and observed with scanning electron microscope. The ratio of cross-sectional area to the circumscribed circle was calculated. Special device was fabricated to simulate the cyclic fatigue fracture of NiTi file in the curved canal,. On this device, NiTi files were rotated (300rpm) with different pecking distances (3 mm or 6 mm) and with different motions (static motion or dynamic pecking motion) . Time until fracture occurs was measured. The results demonstrated that cross-sectional area didn't have any effect on the time of file fracture. Among the files, $Profile^{(R)}$ took the longest time to be fractured. Between the pecking motions, dynamic motion took the longer time to be fractured than static motion. There was no significant difference between the pecking distances with dynamic motion, however with static motion, the longer time was taken at 3mm distance. In this study, we could suggest that dynamic pecking motion would lengthen the time for NiTi file to be fractured from cyclic fatigue.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.36 no.1
• /
• pp.126-132
• /
• 2009

Injuries of permanent teeth by trauma occur frequently in childhood and adolescence. Crown fractures are as frequent as 25-76% and especially maxillary incisors are prone to fractures. There have been numerous efforts to achieve both aesthetically and functionally satisfying restoration. When a mature tooth is fractured, porcelain crown or laminate veneer could be a choice of prosthodontic treatment. However, in a case of immature permanent incisor fracture, prosthodontic treatment is more complicated due to the immaturity of the tooth. Moreover, if endodontic treatment is accompanied with the prosthodontic treatment, the treatment period is prolonged. In the past, restoration using an orthodontic band, a ready-made crown, or glass ionomer cement did not exhibit esthetically satisfying result. As restorational materials have been improved, now more esthetic restoration is possible by reattaching fractured fragments or light-curing composite resin restoration. We reports cases of patients with fractured maxillary incisors and their successful treatment results through reattachment of fractured fragments and composite resin restoration.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.45 no.4
• /
• pp.455-463
• /
• 2018

The purpose of this study was to evaluate the effect of the intracanal medicaments on the push-out bond strength of the calcium silicate-based materials. Forty extracted single-root human mandibular premolars were sectioned below cementoenamel junction. Standardized root canal dimension was obtained with a parallel post drill. The specimens were randomly divided into a control group (no medicament), and experimental groups received medicaments with either CH (calcium hydroxide), DAP (double antibiotic paste; a mixture of ciprofloxacin and metronidazole), or TAP (triple antibiotic paste; a mixture of minocycline, ciprofloxacin and metronidazole). Following removal of medicaments with irrigation, roots were cut into sections with 1-mm-thickness. Thereafter, calcium silicate-based materials are applied to the specimens : (i) ProRoot MTA$^{(R)}$ and (ii) Biodentine$^{(R)}$. A push-out bond strength was measured and each specimen was examined to evaluate failure mode. Intracanal medication using CH significantly increased the bond strength to the root dentin. But there are no significant differences on the bond strength of ProRoot MTA$^{(R)}$ or Biodentine$^{(R)}$ among TAP, DAP and control groups. The dislodgement resistance of Biodentine$^{(R)}$ from root dentin was significantly higher than that of ProRoot MTA$^{(R)}$ regardless of the type of intracanal medicaments.

• The Journal of Korean Academy of Prosthodontics
• /
• v.57 no.2
• /
• pp.127-133
• /
• 2019

Purpose: The purpose of present study was to investigate fracture strength and mode of failure of endodontically treated teeth restored with metal cast post-core system, prefabricated fiber post system, and newly introduced polyetherketoneketone (PEKK) post-core system. Materials and methods: A total of 21 mandibular premolar were randomly grouped into 3 groups of 7 each according to the post material. Group A was for metal cast post core; Group B for prefabricated glass fiber post and resin core; and Group C for milled PEKK post cores. All specimens were restored with metal crown. The fracture strength of each specimen was measured by applying a static load of 135-degree to the tooth at 2 mm/min crosshead speed using a universal testing machine. After the fracture strength measurement, the mode of failure was observed. The results were analyzed using Kruscal-Wallis test and post hoc Mann-Whitney U test at confidence interval ${\alpha}=.05$. Results: Fracture resistance of PEKK post core was lower than those of cast metal post and fiber reinforced post with composite resin core. In the aspect of fracture mode most of the root fracture occurred in the metal post core, whereas the post detachment occurred mainly in the fiber reinforced post. In the case of PEKK post core, teeth and post were fractured together. Conclusion: It is necessary to select appropriate materials of post for extensively damaged teeth restoration and clinical application of the PEKK post seems to require more research on improvement of strength.

• The korean journal of orthodontics
• /
• v.41 no.1
• /
• pp.6-15
• /
• 2011

Objective: The aim of this study was to evaluate the biomechanical aspects of peri-implant bone upon root contact of orthodontic microimplant. Methods: Axisymmetric finite element modeling scheme was used to analyze the compressive strength of the orthodontic microimplant (Absoanchor SH1312-7, Dentos Inc., Daegu, Korea) placed into inter-radicular bone covered by 1 mm thick cortical bone, with its apical tip contacting adjacent root surface. A stepwise analysis technique was adopted to simulate the response of peri-implant bone. Areas of the bone that were subject to higher stresses than the maximum compressive strength (in case of cancellous bone) or threshold stress of 54.8MPa, which was assumed to impair the physiological remodeling of cortical bone, were removed from the FE mesh in a stepwise manner. For comparison, a control model was analyzed which simulated normal orthodontic force of 5 N at the head of the microimplant. Results: Stresses in cancellous bone were high enough to cause mechanical failure across its entire thickness. Stresses in cortical bone were more likely to cause resorptive bone remodeling than mechanical failure. The overloaded zone, initially located at the lower part of cortical plate, proliferated upward in a positive feedback mode, unaffected by stress redistribution, until the whole thickness was engaged. Conclusions: Stresses induced around a microimplant by root contact may lead to a irreversible loss of microimplant stability.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.39 no.2
• /
• pp.174-180
• /
• 2012

In case of an immature tooth with necrotic pulp, regeneration of pulp tissue into a canal would be the ideal outcome. It may be capable of promoting the continuation of normal root development. Platelet-rich fibrin has been suggested as a potentially ideal scaffold for regenerative endodontic treatment. Immature permanent teeth of young children were diagnosed with pulp necrosis and apical abscess as the result of clinical and radiographic examination. After removal of necrotic pulp, canal was irrigated with 5.25% NaOCl and dried with paper point. A triple antibiotic mixture was placed in canal space in 3 weeks. After removal of the antibiotic mixture, the platelet-rich fibrin was injected into the canal space with MTA placed directly over the platelet-rich fibrin clot. The coronal region was restored by composite resin. On the basis of short-term results of the present 3 cases, regeneration of vital tissues appears to be possible in a tooth with necrotic pulp and a periapical lesion. Also, platelet-rich fibrin proves to be potentially an ideal scaffold for this procedure. Therefore, long-term clinical observation and examination about this treatment using platelet-rich fibrin in immature permanent teeth of young children are considered to be necessary.