تقييم كفاءة تصليب جهاز من الجيل الثاني من الاجهزة ذات الصمامات ثنائية الاقطاب عند التصليب الضوئي لنوعين من مواد الترميم الراتنجية

Background & Objective: This study aimed to investigate curing efficiency of a second generation - light emitting diode(LED) curing unit to polymerise two kinds of resin ,one depends upon camphorquinone as a single photo initiator while the other uses co-initiator besides camphorquinone . Materials & methods:20 specimens 3 mm thick were prepared from 2 composites10 specimens of (Z250,shade A2,3M/ESPE)and 10 of( TPH3 ,shade A2,Dentsply ). Specimens were subjected to light polymerisation for 20 seconds using second generation - LED unit (Elipar Free Light 2,3M/ESPE) . Specimens were stored in dark for 24 hours .A hardness tester Galileo Durometria(LTF SPA-AntegnateItaly) was used to obtain 3 measurements of Vickers hardness number (VHN) for each surface (upper and lower) of each specimen .Hardness ratio(HR) was calculated as the VHN of the lower surface divided by the VHN of upper surface .Data were analyzed with T-student analysis (P≤0.05). Results: Significant differences were found between two composites when comparing VHN of upper and lower surface(p<0.05) ,Z250 was harder(106.2kg/mm2 upper,84 lower)than TPH3(62.8 upper,34.3 lower) .hardness ratio of Z250(79%) was equal to 80%(P=O.705) while HR of TPH3(54.6%) was Significantly less than 80%(P=0.000) . Conclusion :Second generation - light emitting diode curing unit used in this study is efficient in curing composites that depend upon camphorquinone ,but it can’t efficiently cure composites that use coinitiator besides camphorquinone