• The Journal of Korean Academy of Prosthodontics
• /
• v.29 no.2
• /
• pp.129-145
• /
• 1991

The purpose of this study was to analyze the stresses and displacements of various esthetic restorations and abutment teeth. The finite element models of central incisor were divided into four groups according to the types of restoration. Three load cases were applied; 1) 45 degrees on the incisal edge, 2) horizontal force on the labial surface, and 3) 26 degrees diagonally on the lingual surface. Material property, geometry, and load conditions of each model were inputed to the two dimensional finite element program and stresses and displacements were analyzed. Results were as follows; 1. In the cases of porcelain fused gold ann and porcelain laminate venner, stresses were equally distributed in supporting abutment tooth. 2. The metal coping of porcelain fused gold u and collarless porcelain fused gold crown functioned as a good stress distributor. 3. When the horizontal load applied, the highest tensile and compressive stresses were seen in the cervical margin of restoration and the dentin of the abutment tooth. 4. The highest displacement of restoration was seen when load was applied at an mee of 26 degrees diagonally in lingual surface of tooth in centric occlusion. 5. The influence of loading direction on the stresses and displacements in the restoration was greater than that of various design. 6. The possibility of fracture was highest in porcelain jacket crown.

• The Journal of Korean Academy of Prosthodontics
• /
• v.25 no.1
• /
• pp.161-179
• /
• 1987

To study the mechanical behaviors of the margins of porcelain-fused-to-metal crown on the posterior teeth, 5 types of margins on the lower first molar were chosen, and then the finite element models were constructed. 50kg forces were applied to the porcelain on the axial wall supported by the metal vertically. The displacements and stresses of the porcelain-fused-to-metal crown were analyzed to investigate the influence of the type of margins. The results were as follows; 1. High tensile stresses were exhibited on the porcelain of the portion of the coronal line angle insufficient metallic support. 2. In case metal coping had a good supporting form to vertical force, uniform compressive stresses were exhibited on their supporting form. 3. Tensile stresses in the inframetallic margin on the series of the shoulder with a bevel margins were decreased in the bevel portion. 4. Principal stresses on the metal of the chamfer marginal portion were decreased comparing with the series of the shoulder margins. 5. The noticeable compressive stress gradients were exhibited between axial cement layer and metal on the series of the shoulder margins. 6. The principal stresses on the marginal cement layer were higher than that of the occlusal surface and axial wall.

• Journal of Technologic Dentistry
• /
• v.21 no.1
• /
• pp.115-121
• /
• 1999

This investing was carried out to evaluate the alteration of stress distribution on teeth and esthetic crowns. Analyzing the stress distribution by the two-dimensional finite element methods, a model of lower 1st molar according to the porcelain fused metal crown an the porcelain fused glass ceramic core crown and the all glass ceramic crown. 1. The pattern of stress distribution showed no apparent differences. 2. The greatest von Mises values were concentrated around the central fossa of all esthetic crowns. The greatest Maximum principle value were concentrated around the interface between the base of esthetic crown and the abutment tooth. It was found that the apatite glass ceramic could be applicable for use in dental crown prosthesis.

• The Journal of Korean Academy of Prosthodontics
• /
• v.57 no.4
• /
• pp.439-447
• /
• 2019

The distance between the natural teeth and the implants is an important factor in preserving the periodontal tissues and esthetics. And abnormal positional displacement and tilting of the teeth during restorative procedure may require intentional root canal treatment and may affect masticatory function. This report is to present a successful full mouth rehabilitation of a patient with uneven dentition and collapsed occlusion using orthodontic and implant treatment. The patient had no symptoms or discomfort of temporomandibular joint disorder such as pain or sound. The orthodontic treatment was continued until implant provisional prosthesis delivery. And the vertical height of occlusion was elevated 2mm on anterior basis for anterior teeth protection and esthetics. After the orthodontic treatment, the implant abutments and natural teeth were finally restored with porcelain-fused-to-metal crowns and bridges. Satisfactory function and esthetic outcomes are observed after 6months of follow up.

• Imaging Science in Dentistry
• /
• v.43 no.2
• /
• pp.123-128
• /
• 2013

Double tooth is a dental anomaly consequent to fusion of two or more teeth or gemination of a single tooth. This report describes a unique case of double tooth in relation to a mandibular lateral incisor exhibiting the presence of four root canals. The role of conventional radiography and advanced three-dimensional imaging techniques in the better assessment of complex root canal systems and their aid in endodontic management has also been highlighted.

• Journal of the Korean Academy of Esthetic Dentistry
• /
• v.10 no.2
• /
• pp.15-20
• /
• 2001

The spaced dentition is a common clinical finding. The careful analysis of clinically spaced dentition is a necessity for effective treatment planning. Spaced dentition often exists in the presence of intact teeth. Therefore, special care should be taken in order to obtain the most successful esthetic effect and to prevent overtreatment as well. The aesthetic restorative dental treatment using the porcelain laminate veneers is getting more popular than the complex orthodontic treatment, and prosthetic solutions that require sacrifice of sound tooth structure. The physical strength of porcelain laminate veneers is not as good as porcelain fused metal crowns, and more researches are needed in the field of bonding between composite cement and porcelain laminate veneer. However, the esthetic results from this unprepared porcelain laminate veneers were satisfactory with Authentic (Ceramay, Germany) pressable ceramic technique and resin cement (Rely X Veneer, 3M). This article deals with 2 cases of unprepared porcelain laminate veneers on anterior teeth.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.36 no.1
• /
• pp.119-125
• /
• 2009

Fusion and gemination are irregularities in tooth development. It is often difficult to differentiate between gemination and fusion and it is common to refer to these anomalies as 'double teeth'. The deciduous teeth are most commonly involved, but in 0.1% of cases permanent teeth are affected, in which case aesthetic, funtional and periodontal problems can result. Double teeth present great difficulties in management and required a multidisciplinary approach. The central groove on the labial and palatal surfaces of a double tooth is extremely prone to caries, therefore early 'fissure sealing' is essential. In permanent dentition, surgical separation of fused teeth may be possible with subsequent orthodontic alignment and restorative treatment as needed to reshape the crown. Reshaping or reduction of a double tooth with a single canal may be attempted by modifying the appearance of the labial groove and the use of composite tints but is often impossible and extraction may be the only alternative. Orthodontic treatment and prosthetic replacement is then required. Implants may be an option for adolescents. The present study describes three clinical cases of double teeth in the position of the maxillary permanent incisors. The first case demonstrates an example of multidisciplinary care including surgical intraoral hemisection, root canal therapy, restorative and orthodontic treatment. The second and third cases describe the external and internal morphology of the two fused teeth by means of three dimensional dental computer tomography.

• 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.

• Journal of Technologic Dentistry
• /
• v.26 no.1
• /
• pp.115-128
• /
• 2004

In this study, optical and mechanical properties were investigated with 4 kinds of commercial dental enamels. As a result of EDS analysis $SiO_2,\;Na_{2}O,\;Al_{2}O_3\;and\;K_{2}O$ were the main components of commercial dental enamels. In case of H specimen, content of $SiO_2\;and\;K_2O$ were more than that of another specimens. Starting powder and fired specimens were glass ceramics which were consist of amorphous phase and leucite (crystalline) phase. Crystallization did not occurred during firing process, since the XRD peak intensity was similar between starting powder and fired specimens. As a result of differential thermal analysis, $T_g$ and crystalline temperature was varied with composition in the range of $548\sim576^{\circ}C$ and $735\sim780^{\circ}C$ respectively. 0.5mm thickness dental enamel specimens showed sufficient translucent properties. However, transmittance and reflectance were lower than 5% result from scattering due to the refractive index difference between glass and crystalline phase. 3 point bending strength was in the range of 73.9$\sim$101.8MPa which was similar or slightly higher than enamel of natural teeth and Vickers hardness was higher than enamel of natural teeth more than 100.

• Imaging Science in Dentistry
• /
• v.45 no.3
• /
• pp.187-192
• /
• 2015

Cleidocranial dysplasia (CCD) is a rare congenital disorder, typically characterized by persistently open skull sutures, aplastic or hypoplastic clavicles, and supernumerary teeth. Mutations in the gene encoding the runt-related transcription factor 2 (RUNX2) protein are responsible for approximately two thirds of CCD patients. We report a 20-year-old CCD patient presenting not only with typical skeletal changes, but also complex dental anomalies. A previously undiagnosed odontoma, 14 supernumerary teeth, a cystic lesion, and previously unreported fused primary teeth were discovered on cone-beam computed tomography (CBCT) scans. Mutation analysis identified the causal c.578G>A (p.R193Q) mutation in the RUNX2 gene. At 20 years of age, the patient had already missed the optimal period for dental intervention. This report describes the complex dental anomalies in a belatedly diagnosed CCD patient, and emphasizes the significance of CBCT assessment for the detection of dental anomalies and the importance of early treatment to achieve good outcomes.