The purpose of this study was to evaluate the fracture strength of class II restore premolars with amalgam, posterior composite, amalgam -Ketac silver, resin -Ketac silver restorations at marginal ridge.
Fifty extacted maxillary and mandibular premolar teeth that were caries free, fracture free, and restoration free were selected and randomly divided into five groups : Group 1 : 10 intact teeth, Group 2 : 10 teeth with class II cavities and
restored
with amalgam, Group 3 : 10 teeth with class II cavities and restored with poterior resin, Group 4 : 10 teeth with class II cavities and restored with amalgam-ketac silver, Group 5 : 10 teeth with class II cavities and restored with resin - Ketac
silver.
All teeth were mounted I base of dental stone within metal rings of 2cm diameter, exposing only the crown portion. Class II mesio-occlusal or disto-occlusal cavities were prepared into specimens of Group 2 through 5 by using a No. 710 fissure
bur.
The
occlusal portion was prepared to a faciolingual width of 1.5mm and a pulpal depth of 1.5mm. The proximal protion was prepared to a faciolingual width of 4mm, a occlusogingival height of 4mm, and a gingival floor of 1.5mm.
The teeth in Group 2 and 3 were resotored with silver amalgam and posterior resin respectively. In Group 4 and 5, proximal portions were first filled with Ketac silver 1.5mm gingivally and remaining cavities were restored with amalgam and
posterior
resin respectively.
All specimens were stored in 100% relative humidity at 37℃for 48 hours before testing. All teeth were subjected to a compressive load in a Universal Instron Testing Machine at marginal ridges. The loads required to fracture the restorations were
recorded in killograms and the data obtained were subjected to statisticall analysis.
@ES The results were all follows :
@EN 1. The fracture strength of Group 1 which were unprepared were 100±10.1 kg and the higher values than Group 2, 3, 4, 5 which were prepared and resotred.
2. In restored groups, Group 2 had the higher fracture strength (81.8±12.4 kg) than other groups and Group 4 had the lowest fracture strength(66.8±9.2 kg).
3. There were significant differences between fracture strength of between Group 1 and Group 3, 4, 5(P<0.05), but not significant difference between fracture strength of Group 2, 3, 4, 5(P>0.05).
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