A study on the shear bond strength between Co-Cr denture base and relining materials / 대한치과보철학회지

PURPOSE: This study evaluated the bonding strength of direct relining resin to Co-Cr denture base material according to surface treatment and immersion time. MATERIALS AND METHODS: In this study, Co-Cr alloy was used in hexagon shape. Each specimen was cut in flat surface, and sandblasted with 110 microm Al2O3 for 1 minute. 54 specimens were divided into 3 groups; group A-control group, group B-applied with surface primer A, group C-applied with surface primer B. Self curing direct resin was used for this study. Each group was subdivided into another 3 groups according to the immersion time. After the wetting storage, shear bond strength of the specimens were measured with universal testing machine. The data were analyzed using two-way analysis of variance and Tukey post hoc method. RESULTS: In experiment of sandblasting specimens, surface roughness of the alloy was the highest after 1 minute sandblasting. In experiment of testing shear bond strength, bonding strength was lowered on group B, C, A. There were significant differences between 3 groups. According to period, Bonding strength was the highest on 0 week storage group, and the weakest on 2 week storage group. But there were no significant differences between 3 periods. According to group and period, bonding strength of all group were lowered according to immersion time but there were no significant differences on group B and group C, but there was significant difference according to immersion time on group A. CONCLUSION: It is useful to sandblast and adopt metal primers when relining Co-Cr metal base dentures in chair-side.

Comparative study of fracture strength depending on the thickness of some all ceramic cores / 대한치과보철학회지

STATEMENT OF PROBLEM: The increased awareness of esthetics in dentistry has brought the esthetic consideration in prosthetic restorations. Dental ceramics offer better esthetics for use of prosthetic restorations. Unfortunately, dental ceramic materials are not always the most suitable candidate materials since their inherently brittle nature. In recent years, basic research in ceramic science has led to the recognition of several approaches to strengthen and to enhance esthetics of ceramics. Several all ceramic systems use ceramic core and porcelain build up structures. Ceramic cores influence to strength of all ceramic crowns. So the strength of ceramic cores is important to all ceramic crowns. PURPOSE: The purpose of this study is to estimate the flexural strength of ceramic cores in some all ceramic systems. Material and method : A biaxial flexure test was conducted on three groups(Cergo, Empress 2, In-Ceram). Each group consisted of 30 discs of nearly identical dimension with a 0.5mm, 1.0mm, 1.5mm thickness and 12mm in diameter. The fracture load was recorded by Instron. Analysis of variance(ANOVA) and Tukey's tests were performed using SAS statistical software. RESULTS: 1.5mm thickenss of specimens were significantly stronger than 0.5mm and 1.0mm thickness of specimens in Cergo and In-Ceram. But each sepecimen group of Empress 2 was no significantly strength by thickness. In order of In-Ceram, Empress 2 and Cergo has significantly stronger strength in the same thickness. CONCLUSION: In-Ceram is the strongest ceramic material in 3 materials. All the materials can be used according to the required characters.

One case of Medial Medullary Syndrome

Medial medullary syndrome is a clinical disorder charactenzed by ipsilateral paralysis of tongue and contralateral hemiparalysis and contralateral hemisensory disturbance of vibration or position but face sparing. The syndrome is ususlly due to lesion of medial medulla oblongata. Involved structures are pyramid, hypoglossal nucleus, medial lemniscus and/or medial longitudinal fasciculus. We present 1 case of medial medullary syndrome with MRI finding, which showed infarction of left medial medulla oblongata.