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The study of fractural behavior of repaired composite
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Sang-Soon Park, Wook Nam, Ah-Hyang Eom, Duck-Su Kim, Gi-Woon Choi, Kyoung-Kyu Choi
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J Korean Acad Conserv Dent 2010;35(6):461-472. Published online November 30, 2010
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DOI: https://doi.org/10.5395/JKACD.2010.35.6.461
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 Abstract
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Objectives
This study evaluated microtensile bond strength (µTBS) and short-rod fracture toughness to explain fractural behavior of repaired composite restorations according to different surface treatments.
Materials and Methods
Thirty composite blocks for µTBS test and sixty short-rod specimens for fracture toughness test were fabricated and were allocated to 3 groups according to the combination of surface treatment (none-treated, sand blasting, bur roughening). Each group was repaired immediately and 2 weeks later. Twenty-four hours later from repair, µTBS and fracture toughness test were conducted. Mean values analyzed with two-way ANOVA / Tukey's B test (α = 0.05) and correlation analysis was done between µTBS and fracture toughness. FE-SEM was employed on fractured surface to examine the crack propagation.
Results
The fresh composite resin showed higher µTBS than the aged composite resin (p < 0.001). Mechanically treated groups showed higher bond strength than non-mechanically treated groups except none-treated fresh group in µTBS (p < 0.05). The fracture toughness value of mechanically treated surface was higher than that of non-mechanically treated surface (p < 0.05). There was no correlation between fracture toughness and microtensile bond strength values. Specimens having high KIC showed toughening mechanism including crack deviation, microcracks and crack bridging in FE-SEM.
Conclusions
Surface treatment by mechanical interlock is more important for effective composite repair, and the fracture toughness test could be used as an appropriate tool to examine the fractural behavior of the repaired composite with microtensile bond strength.
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The effect of calcium hydroxide on post-treatment pain
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Wook Nam, Sang-Hyuk Park, Gi-Woon Choi
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J Korean Acad Conserv Dent 2006;31(2):86-95. Published online March 31, 2006
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DOI: https://doi.org/10.5395/JKACD.2006.31.2.086
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Abstract
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The purpose of this clinical study is to assess whether calcium hydroxide as an intracanal medication affects post-treatment pain in teeth especially odontogenic pain which comes from inflammation of the pulp and periradicular tissues when compared with no intracanal medication.
From 213 patients who has been treated 237 root canals due to significant pain (moderate-to-severe), we recorded their age, sex, treated tooth, degree of pain, pre-operative states of the tooth. We classified patients into 2 test group; Group 1 (not gain intracanal Ca(OH)2), Group 2 (gain intracanal Ca(OH)2). Through the survey from the patients, we let them write down the occurrence and degree of post-treatment pain in 4hours, 2days, 7days after treatment as none, mild, moderate or severe. The followings were evaluated; the overall incidence of flare-ups, the overall incidence of post-treatment pain in each group at each time period, the incidence of post-treatment pain in each group at each time period as related to pre-operative states of the teeth. These were compared statistically with Chi-square analysis (p < 0.05).
Under the condition of this investigation, no difference was observed in the incidence of post-treatment pain between the two groups. Therefore, Ca(OH)2 as intracanal medication had no effect on preventing or decreasing the post-treatment pain.
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