• The korean journal of orthodontics
• /
• v.26 no.6
• /
• pp.657-666
• /
• 1996

Orthopantomogram is commonly used to evaluate root parallelism. "Good parallelism" between roots is widely accepted as one of the guidelines of a successful orthodontic treatment. In case there was a large angle between crown axis and root axis, and if we valued only the position of crown in establishing occlusal relationship without considering of the situation of root, the problem of root arrangement between adjacent teeth would be occurred. The estimate of root parallelism in mesiodistal direction before and after orthodontic treatment must be emphasized. The intent of this study was to determine the clinical importance and correlation of the angle between crown axis and root axis. Orthopantomograms of 105 orthodontic patients being treated in Yonsei university were used in this study. Twenty-eight teeth in both maxilla and mandible were selected and analyzed quantitively to evaluate the angle between crown axis and root axis, and obtain the correlationship among the individual teeth. The results are as follows: 1. Among the teeth presenting normal distribution, the maxillary right canine showed the largest mean value( $5.73{\pm}4.42^{\circ}$), which was composed of the crown-root angles, and the mandibular left lateral incisor showed the smallest mean value( $0.60{\pm}3.76^{\circ}$). 2. The crown-root angles of the maxillary incisors and the first molars, and the mandibular central incisors and the first molars didn't show normal distribution and the ranges of these angles were dispersed. 3. Significant differences were present between the crown axis and the root axis except for lower first premolars. (p<0.05) 4. No significant difference was present for the crown-root angle between right and left side, (p<0.05) 5. No significant difference was present for the crown-root angle between male and female except for lower left first premolar. (p<0.05) 6. In the upper right quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor, lateral incisor and canine. In the upper left quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor. In the lower right quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor, first molar and second molar. In the lower left quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor, lateral incisor and canine, first molar and second molar. (p<0.05)

• Journal of the korean academy of Pediatric Dentistry
• /
• v.36 no.2
• /
• pp.270-274
• /
• 2009

Dentigerous cysts generally encompass the crown of an unerupted tooth. These cysts are usually solitary. They are the second most common odontogenic type of cysts following radicular cysts, and are frequently associated with impacted mandibular third molars or maxillary canines. Most multiple cysts found in the jaw are odontogenic keratocysts associated with the nevoid basal cell carcinoma syndrome, mucopolysaccharidoses and cleidocranial dysplasia. Although a single dentigerous cyst is well documented in the medical literature, including the prevalence, treatment and prognosis, multiple dentigerous cysts without any systemic symptoms is unusual. Furthermore, cases involving both the maxilla and mandible are especially rare. We present the case of an 11-year-old boy with nonsyndromic multiple dentigerous cysts associated with a mandibular second premolar and a maxillary canine. The treatment was conservative and included marsupialization and eruption guidance. Further follow up is planned to rule out additional problems and the possible identification of a syndrome.

• Restorative Dentistry and Endodontics
• /
• v.33 no.6
• /
• pp.570-579
• /
• 2008

The purpose of this study was to investigate the distribution of tensile stress of canal obturated maxillary second premolar with access cavity and notch-shaped class V cavity restored with composite resin using a 3D finite element analysis. The tested groups were classified as 8 situations by only access cavity or access cavity with notch-shaped class V cavity (S or N), loading condition (L1 or L2), and with or without glass ionomer cement base (R1 or R2). A static load of 500 N was applied at buccal and palatal cusps. Notch-shaped cavity and access cavity were filled microhybrid composite resin (Z100) with or without GIC base (Fuji II LC). The tensile stresses presented in the buccal cervical area, palatal cervical area and occlusal surface were analyzed using ANSYS. Tensile stress distributions were similar regardless of base. When the load was applied on the buccal cusp, excessive high tensile stress was concentrated around the loading point and along the central groove of occlusal surface. The tensile stress values of the tooth with class Ⅴ cavity were slightly higher than that of the tooth without class V cavity. When the load was applied the palatal cusp, excessive high tensile stress was concentrated around the loading point and along the central groove of occlusal surface. The tensile stress values of the tooth without class V cavity were slightly higher than that of the tooth with class V cavity.

• The korean journal of orthodontics
• /
• v.28 no.3 s.68
• /
• pp.379-389
• /
• 1998

The purpose of the present study was to evaluate the change of tooth mobility following orthodontic tooth movement. Six orthodontic patients which had been treated with edgewise appliance were used. Tooth mobility was measured with Periostest at the time of the removal of orthodontic appliance and 1, 2, 3, 4, 6, 8, 10, 12, 16, 20, 24 weeks after appliance removal. Following results were obtained: 1. Tooth mobility upon the removal of orthodontic appliance showed individual variation while incisor showed greater mobility than the other teeth. 2. Tooth mobility showed continued decrease pattern until 24 weeks after appliance removal. 3. While maxillary incisors showed continued decrease pattern during the study period, the other teeth showed steep decline pattern during the first 12 weeks and gentle slope during the second 12 weeks. 4. The tooth mobility of the maxillary second premolar showed the most typical change in terms of the consistency of the decline. 5. There were no significant differences of tooth mobility between heavy- and light-contacted anterior teeth during experimental period. The results of the present study suggested that periodontal reorganization is not completed even in 24 weeks following orthodontic tooth movement.

• The korean journal of orthodontics
• /
• v.41 no.4
• /
• pp.237-254
• /
• 2011

Objective: The purpose of this study was to compare the displacement patterns shown by finite element analysis when the maxillary anterior segment was retracted from different orthodontic miniscrew positions and different lengths of lever arms in lingual continuous and segmented arch techniques. Methods: A three dimensional model was produced, the translation of teeth in both models was measured and individual displacement was calculated. Results: When traction was carried out from miniscrews in the palatal slope, lingual tipping of crowns and extrusion of the maxillary anterior segment were found in both continuous and segmented arches as the lever arms were made shorter. With miniscrews in the midpalatal suture area, the displacement patterns were similar to the palatal slope, but bodily movement of the upper incisors was observed in both continuous and segmented arches with the lever arm at 20 mm. When lever arms were longer, there was less extrusion of the incisors and more buccal displacement of the canines. Such displacement was shown less in the continuous arch than the segmented arch. The second premolar showed crown mesial tipping and intrusion, and the molars showed distal tipping in the continuous arch. The posterior segment was displaced three dimensionally in the segmented arch, but the amount of displacement was less than the continuous arch. Conclusions: It is recommended that lever arms of 20 mm in length be used for bodily movement of the anterior segment. Use of continuous or segmented arches affect the displacement patterns and induce differences in the amount of displacement.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.29 no.4
• /
• pp.574-578
• /
• 2002

Mesiodens is developmental tooth anomaly which is commonly found in clinical pediatric dentistry. however, it may cause many partial problem in tooth alignment when congenitally missing teeth was accompanied by mesiodens. The terms, concomitant hypodontia and hyperdontia' and oligo-pleiodontia' have been used to describe the condition in witch developmental absence of teeth and supernumerary teeth are present in the same individual. Only a few case reports of this rare condition which is opposite developmental phenomena exist in the literature. The purpose of this study is survey of congenitally missing teeth in mesiodens case and to compare previous literature of congenitally missing teeth in normal. The subjects were 310 children(247 male and 63 female) at the age from 5 to 12 years visiting the Department of Pediatric Dentistry, Pusan National University Hospital with mesiodens for last 3 years. With their pantomograms we studied congenitally missing teeth except permanent 3rd molar. 1. The preference of congenitally missing teeth in mesiodens cases was revealed to be 17.1%(53 out of 310 in total), and there was a higher prevalence in females(22.2%) than in males(15.8%). 2. The most frequently missing teeth were maxillary lateral incisors(22.7%) and mandibular second premolars(22.7%), followed by maxillary second premolar(17.3%), and mandibular lateral incisors(16.0%). There was no significant differences between maxilla(49.3%) and mandible(50.7%). 3. In number of congenitally missing teeth per person, 69.9% had one missing tooth, 22.7% had two missing teeth and 9.4% had three missing teeth.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.35 no.2
• /
• pp.195-204
• /
• 2008

Orthodontic brackets often need to be bonded to porcelain such as porcelain fused to metal crowns and porcelain jacket crowns. The purpose of this study was to evaluate the clinical usability of direct bonding system on porcelain teeth by measuring shear bond strength according to various conditions and observing adhesive failure patterns. The specimens, 20 maxillary premolars and 80 porcelain teeth that were produced by duplication of the labial surface of a maxillary first premolar were used and randomly divided into four groups of twenty teeth each. The 5 different preparation procedures tested: (1) application of 37% phosphoric acid on natural teeth, (2) sandblasting on porcelain surfaces, (3) sandblasting and application of 9.6% hydrofluoric acid on porcelain surfaces, (4) sandblasting and application of silane on porcelain surface, (5) sandblasting and application of 9.6% hydrofluoric acid and silane on porcelain surfaces. The metal brackets were bonded with Transbond $XT^{(R)}$ bonding material. The shear bond strength was tested by the micro universal testing machine(Kyung-Sung, Korea) and the amount of residual adhesive on the tooth surface after debonding was examined by stereoscope and assessed with an adhesive remnant index. The results of this study suggest that the direct bonding system on porcelain teeth with sandblasting, HF and porcelain primer is clinically useful.

• The Journal of Advanced Prosthodontics
• /
• v.6 no.3
• /
• pp.200-206
• /
• 2014

PURPOSE. This in vitro study investigated the fracture resistance of endodontically treated premolars restored using silorane-or methacrylate-based composite along with or without fiber or nano-ionomer base. MATERIALS AND METHODS. Ninety-six intact maxillary premolars were randomly divided into eight groups (n = 12). G1 (negative control) was the intact teeth. In Groups 2-8, root canal treatment with mesio-occlusodistal preparation was performed. G2 (positive control) was kept unrestored. The other groups were restored using composite resin as follows: G3, methacrylate-based composite (Z250); G4, methacrylate composite (Z250) with polyethylene fiber; G5 and G6, silorane-based composite (Filtek P90) without and with the fiber, respectively; G7 and G8, methacrylate-and silorane-based composite with nano-ionomer base, respectively. After aging period and thermocycling for 1000 cycles, fracture strength was tested and fracture patterns were inspected. The results were analyzed using ANOVA and Tukey HSD tests (${\alpha}$=0.05). RESULTS. Mean fracture resistance for the eight groups (in Newton) were G1: $1200{\pm}169^a$, G2: $360{\pm}93^b$, G3: $632{\pm}196^c$, G4: $692{\pm}195^c$, G5: $917{\pm}159^d$, G6: $1013{\pm}125^{ad}$, G7: $959{\pm}148^d$, G8: $947{\pm}105^d$ (different superscript letters revealed significant difference among groups). Most of the fractures in all the groups were restorable, except Group 3. CONCLUSION. Silorane-based composite revealed significantly higher strength of the restored premolars compared to that of methacrylate one. Fiber insertion demonstrated no additional effect on the strength of both composite restorations; however, it increased the prevalence of restorable fracture of methacrylate-based composite restored teeth. Using nano-ionomer base under methacrylate-based composite had a positive effect on fracture resistance and pattern. Only fiber-reinforced silorane composite restoration resulted in a strength similar to that of the intact teeth.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.30 no.4
• /
• pp.265-277
• /
• 2014

Purpose: The purpose of this study was to investigate the differences of displacement pattern depending on type of sliding jig and application method during maxillary molar distalization with temporary anchorage devices (TADs). Materials and Methods: Maxilla with normal tooth size and arch shape was selected to create a 3-dimensional finite element model, which included the bracket, orthodontic main archwire, removable sliding jig (R-jig). The orthodontic mini-implant anchorage was set 8 mm superiorly from main archwire, buccally between the second premolar and first molar. The base experimental design was Condition 1, which was composed $0.019{\times}0.025$ inch stainless steel (SS) of wire size of R-jig, 200 gm force, un-tied state. And the other designs varied to wire size of R-jig, magnitude of force. The results are as follows. Results: As the wire size of R-jig was increased, the deformation of R-jig was decreased. However, the displacement of second molar wasn't different each other. As the force to second molar was increased, the more displacement of second molar was observed, and the more distal tipping movement, vetical displacement was observed. Conclusion: R-jig can get distal teeth movement in orthodontic treatment without side effects.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.28 no.1
• /
• pp.27-36
• /
• 1998

The purpose of this study was to obtain information on the clinical and radiographic features of the fibro-osseous lesions in the jaws. For this study, the author examined and analysed the clinical records and radiographs of 71 cases of 68 patients in fibrous dysplasia, 35 cases of ossifying fibroma and 30 cases of 16 patients of periapical cemental dysplasia diagnosed by clinical and radiographic or histopathological examinations. The obtained results were as followings: L Fibrous dysplasia occurred most frequently in the 2nd decade (30.0％), ossifying fibroma in the 3rd-4th decades, periapical cemental dysplasia in the 4th decade, and all of three lesions showed slight predilection in females. In most cases, chief complaints were painless facial swelling in fibrous dysplasia and ossifying fibroma, and periapical cemental dysplasia was found accidentally in radiographs. 2. Fibrous dysplasia was occurred more frequently in maxilla, ossifying fibroma in mandible and both lesions in premolar-molar area. Periapical cemental dysplasia was occurred most frequently in the mandibular anterior area. The size of fibrous dysplasia was larger than that of ossifying fibroma, and the shape of ossifying fibroma was more round and elliptical than fibrous dysplasia whose was fusiform. 3. Fibrous dysplasia was shown homogeneous radiopaque shadow of 57.6％ and ossifying fibroma & periapical cemental dysplasia were shown mixed appearance of radiolucency and radiopacity shadows at 74.2％, 60.0％, respectively. 4. Fibrous dysplasia was entirely shown poorly defined at 87.7％, but ossifying fibroma & periapical cemental dysplasia were shown well outlined at 60.0％, 70.0％, respectively. 5. Cortical thinning and expansion were observed in fibrous dysplasia and ossifying fibroma, and severe in ossifying fibroma than fibrous dysplasia, and those signs were not seen in periapical cemental dysplasia. Loss of lamina dura was dominant in fibrous dysplasia and root resorption was dominant in ossifying fibroma. Displacement of mandibular canal and the degree of the increase of vertical dimension were alike in both lesions. Displacement of maxillary sinus or nasal cavity, thinning & expansion of the maxillary sinus were dominant in fibrous dysplasia. 6. Polyostotic fibrous dysplasia was occurred at 5.9％, Multiple periapical cemental dysplasia at 43.7％. Occurrence rate in the edentulous area of fibrous dysplasia and ossifying fibroma were 7.0％, 8.6％, respectively.