ISSN (print) 1226-8496 ISSN (online) 2288-3819 http://dx.doi.org/10.5933/jkapd.2014.41.2.152 Evaluation of New LED Curing Light on Resin Composite Polymerization Jieun Kang, Saeromi Jun, Jongbin Kim, Jongsoo Kim, Seunghoon Yoo Department of Pediatric Dentistry, School of Dentistry, Dankook University Abstract The purpose of this study is to compare efficiency of broad spectrum LEDs (VALO, Ultradent, USA) with conventional LED curing lights (Elipar TM Freelight 2, 3M ESPE, USA) using a microhardness test. The light curing units used were VALO in three different modes and Elipar TM Freelight 2. The exposure time was used according to the manufacturer's instructions. After cured resin specimens were stored in physiological saline at 37 for 24 hours, microhardness was measured using Vickers microhardness tester. The microhardness of upper and lower sides of the specimens were analyzed separately by the ANOVA method (Analysis of Variance) with a significance level set at 5%. At upper side of resin specimens, an increased microhardness was observed in the broad spectrum LED curing light unit with a high power mode for 4 seconds and plasma emulation mode for 20 seconds (p < 0.05). However, at the lower side of resin specimens, there were no significant differences in microhardness between broad spectrum LED curing light unit and conventional LED curing light unit. Key words : Light emitting diodes, Broad spectrum, Microhardness, Curing unit Ⅰ. 서론광중합은치과진료시여러분야에서쓰이고있다. 현재까지개발되어임상에적용된가시광선광중합유형은석영텅스텐할로겐 (Quartz tungsten halogen) 램프, 발광다이오드 (Light emitting diodes, LED) 유니트, 플라즈마아크램프그리고아르곤이온레이저로나눌수있다 1,2). 2001년처음발광다이오드광중합기가치과계에도입되었다 3). 발광다이오드광중합기는가열되는필라멘트대신두개의각기다른도프반도체를이용한다 2,4). 푸른색의질화갈륨발광다이오드의스펙트럼은캠포로퀴논 (camphoroquinone) 의흡수스펙트럼범위에포함된다 1,4,5). 그러므로푸른빛을만들어내기위한필터가따로필요하지않으며전기를빛으로더효율적으로전환할수있다 4). 열발생이적으므로열을식히기 위한냉각팬이필요하지않아광중합기를더작게, 무선으로만들수있으며일정한광출력으로오랜시간작동할수있다 3,5). 발광다이오드광중합기의기술이발전되면서고성능의 2세대발광다이오드광중합기 ( 예, FreeLight 2 curing light, 3M ESPE, USA) 가소개되었다. 이광중합기는 1세대모델 ( 예, the original FreeLight, 3M ESPE, USA) 에비해성능이향상되었으며방사조도가높아졌다 6). 새롭게출시되고있는많은발광다이오드광중합기는 400 mw/cm 2 이상의출력을가지고있기때문에제조사의지시보다짧은중합시간으로도복합레진을중합할수있다 6). 그러나상대적으로이에대한연구가부족한실정이다. 복합레진의중합정도를평가하는방법으로직접적인평가방법과간접적인평가방법이있으며, 직접적인평가방법으로는 Fourier transformed infrared spectroscopy(ftir), Corresponding author : Seunghoon Yoo Department of Pediatric Dentistry, School of Dentistry, 119 Dandaero, Dongnam-gu, Cheonan, 330-714, Korea Tel: +82-41-550-0222 / Fax: +82-41-550-0118 / E-mail: yoo.seunghoon@gmail.com Received January 2, 2014 / Revised May 14, 2014 / Accepted May 14, 2014 152
Raman spectroscopy 등을이용하는방법이있다. 간접적인평가방법중가장많이쓰이는방법은경도시험이며, 치과영역에서는누프미세경도시험, 비커스미세경도시험등이자주사용된다 7). 비커스미세경도시험을이용하여복합레진의중합정도를평가하고이를통해광원의효율을평가할수있다 8). 이연구의목적은비커스미세경도시험을통해복합레진시편의상부와하부의미세경도를비교함으로써광범위스펙트럼발광다이오드 (VALO, Ultradent, USA) 광중합기와기존의발광다이오드광중합기 (Elipar TM Freelight 2, 3M ESPE, USA) 의효율을비교하고자함이다. Ⅱ. 연구재료및방법직경 5 mm, 두께 2 mm의금속원형주형에 A2 shade Filtek Z250 (3M ESPE, USA) 복합레진을위치시켰다. 투명한폴리에스테르스트립위에금속주형을놓고복합레진을위치시킨후그위에또다른투명폴리에스테르스트립을위치시켰다. 평평한중합표면을얻기위해얇고투명한커버글라스를그위에위치시켰으며손가락으로압력을가하여과잉레진을제거하였다. 그후에실험에사용된광중합기를이용하여중합을실시하였다 (Table 1). 37 의생리식염수에중합된레진시편을 24시간동안보관한후비커스경도시험기를이용하여하중 300 gm, 하중적용시간 (dwelling time) 10초로압흔을만든후 400배율로확대하여그크기를계측하였다. 10개의시편상부와하부에각각 3 회씩시험을시행하였다. 평균미세경도를비교하기위하여 ANOVA(Analysis of Variance) 분석을시행하였다. Ⅲ. 결과평균비커스경도와표준편차를 Table 2에나타내었다. 두개의발광다이오드광중합기모두중합후시편의하면의경도가상면의경도보다현저히낮은값을보였다. ANOVA 시험결과를 Table 2에나타내었다. 시편의상면의평균미세경도를비교한결과, 1군의평균미세경도에비해 3군과 4군의평균미세경도가유의하게증가했다 (p < 0.05). 2군의평균미세경도는 1군의평균미세경도와 유의성있는차이를보이지않았다. 시편의하면에서는광범위스펙트럼발광다이오드광중합기로실험한군의평균미세경도와기존의발광다이오드광중합기로실험한군의평균미세경도간에유의할만한차이를보이지않았다. 2군과 4군을비교하면같은광중합기의같은광도로중합시간만을다르게하여비교했을때상면과하면모두에서평균미세경도가증가했다. Ⅳ. 총괄및고찰성공적인수복을위해적절한복합레진의중합은필수적이다 9). 복합레진의중합정도는재료의기계적특성, 용해도, 체적안정성, 색변화, 생체적합성에영향을미친다 10,11). 복합레진의최심부층이적절하게중합되지않는다면, 하면의탄성계수가상면의탄성계수에비해낮아질것이다. 그결과구강내에서저작이반복되는동안재료의변형이일어날수있으며수복물의계면에틈이생기거나파절이일어날수있다 12). 이상적인광중합기는광범위한스펙트럼을가져야하며충분한광도를가지며빛이분산되지않고중합하고자하는곳에집중될수있어야한다. 또한여러종류의중합모드가있어서필요에따라적절한중합모드를선택할수있어야하고내구성이좋아야하며여러번의중합이필요할때중합을반복해도충분한지속시간을가져야한다. 중합의심도와미세경도시험은복합레진의중합정도를평가하기위해널리쓰이고있다. Uhl 13) 은중합의심도에가장큰영향을미치는요소는중합시간이며뒤이어레진의종류와광중합기가영향을미친다고하였다. 본연구에서도시간의증가가미세경도의증가와비례관계를보인결과와일치하였다. 따라서제조사의지시보다짧은광중합은바람직하지않으며수복재료의선택에도신중을기해야한다고하였다. Ceballos 등 14) 은중합의심도와미세경도는중합광에의해영향을받는것이아니라중합광과중합시간간의상호작용과중합광과중합심도사이의상호작용에영향을받는다고하였다. 복합레진의두께와중합시간은수복물의미세경도에영향을끼치는주요요소들이다 15). 중합정도가높을수록수복물의기계적성질, 생체적합성, 흡수성, 색안정성그리고마모저항성이높아진다 10,11,16). Table 1. Light curing units used according to the manufacturer's instruction Group LCU Intensity Curing time(sec) 1 Elipar TM freelight 2 1200 mw/cm 2 20 2 3200 mw/cm 2 3 3 VALO 1400 mw/cm 2 4 4 3200 mw/cm 2 20 Table 2. Mean values of microhardness Group Upper side Lower side Mean (Hv) SD Mean (Hv) SD 1 73.3 5.9 63.9 9.4 ** 2 74.0 ** 5.1 61.2 * 7.2 3 83.2 8.1 57.7 * 10.6 4 83.6 3.9 73 5.8 One-way ANOVA and Scheffe test * : Significantly different among groups (p < 0.05) 153
광원이나에너지가불충분하면복합레진의완전한중합을얻기가어려우며이에따라접착강도감소, 유지력감소, 기계적성질저하, 미세누출증가가뒤따르게되어결국이차우식이발생하는원인이될수있다. 이전의연구에따르면, 중합시간은중합결과에영향을끼치는가장중요한요인이었으나임상적으로특히, 소아치과영역에서는수복과정동안소아환자의협조를얻기가어렵기때문에중합시간을단축하는것은큰장점으로생각된다. Price 등 17) 은빛의파장에따라같은광도의광중합기라도유의하게다른경도값이관찰됨을보고하였다. 같은광도로같은시간동안광중합한복합레진시편을비교했을때중합효율은광개시제의빛의흡수율에의존하는것으로생각된다. 많은광중합형복합레진은광개시제로캠포로퀴논을함유하고있으며캠포로퀴논이자유라디칼을생성하여중합반응을일으킨다. 캠포로퀴논은 450~490 nm의파장의빛을흡수하여중합을개시하며 470 nm에서가장효과적이다 18). 어떤복합레진은캠포로퀴논이외에도다른광개시제를함께포함하고있는데이광개시제는더짧은파장의빛을흡수하여반응한다. 복합레진내에서짧은파장의빛은긴파장의빛보다훨씬흡수가많이되기때문에짧은파장의빛을이용해중합을하는광개시제의경우복합레진의안쪽으로갈수록중합의개시에필요한빛이부족하게되어충분한양의광자를흡수하지못하면중합반응을일으키지못하게된다 17,19). 대부분의새로개발된광중합기는 400 mw/cm 2 이상의광도를갖지만발생되는파장은복합레진의광개시제의흡수특성과맞지않을수있기때문에결과적으로불충분한중합이일어날수있다. 따라서광도뿐만아니라파장역시복합레진의중합에영향을주는요소로생각된다 7). VALO 제조사에따르면, 광범위스펙트럼광중합기는 395 nm에서 480 nm의범위의네개의발광다이오드를가지고있어모든복합레진의중합이가능하며, 중합심도는표준모드 (20초) 에서 8.44 mm, 고성능모드 (4초) 에서 8.26 mm, 플라즈마모드 (3초) 에서 7.40 mm라고하였다. 하지만심부안쪽까지도달하는빛의질과양에대해서는더고려되어야할사항으로생각된다. 제조사의지시에따르면, 빠른중합모드는교정용브라켓부착이나얕은표면을중합할때추천된다고하였으며, 깊은중합이필요할때는추가적인광조사가필요하다고하였다. 연구결과빠른중합모드는고성능의광조사에도불구하고심부레진의중합에불충분하다는것을알수있었다. 따라서연구에사용한광중합기를사용할때에는적응증의선택에신중을기해야하며사용의범위가제한되어있음을알아야한다. 추후짧은중합시간의효과와광중합기의고성능, 중합깊이와중합수축에관한보다깊이있는연구와더불어높은중합강도의열발생과그것의재료에대한영향, 환자에대한영향에관한연구가필요할것으로사료된다. Ⅴ. 결론기존의발광다이오드광중합기와비교하여 VALO 는광범위스펙트럼발광다이오드광중합기로복합레진시편을중합했을때표면에서는통계적으로유의하게평균미세경도가증가했지만중합시간을단축시켜중합했을때심부까지의불충분한중합으로인해미세경도에차이를보였다. 하지만, 기존광중합기보다광도가증가되었고, 다양한모드를지원하므로소아치과및교정영역에서유용한장비라고사료된다. References 1. Herva s-garcl a A, Martl nez-lozano MA, Fos-Galve P, et al. : Composite resins. A review of the materials and clinical indications. Med Oral Patol Oral Cir Bucal, 11:215-220, 2006. 2. Vandewalle KS, Roberts HW, Tiba A, Charlton DG : Thermal emission and curing efficiency of LED and halogen curing lights. Oper Dent, 30:257-264, 2005. 3. Uhl A, Michaelis C, Mills RW, Jandt KD : The influence of storage and indenter load on the Knoop hardness of dental composites polymerized with LED and halogen technologies. Dent Mater, 20:21-28, 2004. 4. Mills RW, Uhl A, Blackwell GB, Jandt KD : High power light emitting diode (LED) arrays versus halogen light polymerization of oral biomaterials: Barcol hardness, compressive strength and radiometric properties. Biomaterials, 23:2955-2963, 2002. 5. Stahl F, Ashworth SH, Jandt KD, Mills RW : Lightemitting diode (LED) polymerisation of dental composites: flexural properties and polymerisation potential. Biomaterials, 21:1379-1385, 2000. 6. Felix CA, Price RB, Andreou P : Effect of reduced exposure times on the microhardness of 10 resin composites cured by high-power LED and QTH curing lights. J Can Dent Assoc, 72:147, 2006. 7. Torno V, Soares P, Vieira S, et al. : Effects of irradiance, wavelength, and thermal emission of different light curing units on the Knoop and Vickers hardness of a composite resin. J Biomed Mater Res, 85:166-171, 2008. 8. Kurachi C, Tuboy AM, Magalhã es DV, Bagnato VS : Hardness evaluation of a dental composite polymerized with experimental LED-based devices. Dent Mater, 17:309-315, 2001. 9. Yoon TH, Lee YK, Lim BS, Kim CW : Degree of 154
polymerization of resin composites by different light sources. J Oral Rehabil, 29:1165-1173, 2002. 10. Hinoura K, Akiyama Y, Onose H, et al. : Influence of irradiation sequence on dentin bond of resin inlays. Oper Dent, 20:30-33, 1995. 11. Ferracane JL, Mitchem JC, Condon JR, Todd R : Wear and marginal breakdown of composites with various degrees of cure. J Dent Res, 76:1508-1516, 1997. 12. David JR, Gomes OM, Reis A, et al. : Effect of exposure time on curing efficiency of polymerizing units equipped with light-emitting diodes. J Oral Sci, 49:19-24, 2007. 13. Uhl A, Mills RW, Jandt KD : Photoinitiator dependent composite depth of cure and Knoop hardness with halogen and LED light curing units. Biomaterials, 24:1787-1795, 2003. 14. Ceballos L, Fuentes MV, Rodrl guez J, et al. : Curing effectiveness of resin composites at different exposure times using LED and halogen units. Med Oral Patol Oral Cir Bucal, 14:E51-56, 2009. 15. Rueggeberg FA, Caughman WF, Curtis JW Jr. : Effect of light intensity and exposure duration on cure of resin composite. Oper Dent, 19:26-32, 1994. 16. Rueggeberg FA, Craig RG. : Correlation of parameters used to estimate monomer conversion in a lightcured composite. J Dent Res, 67:932-937, 1988. 17. Price RB, Felix CA, Andreou P : Knoop hardness of ten resin composites irradiated with high-power LED and quartz-tungsten-halogen lights. Biomaterials, 26:2631-2641, 2005. 18. Nomoto R : Effect of light wavelength on polymerization of light-cured resins. Dent Mater J, 16:60-73, 1997. 19. Uhl A, Siqusch BW, Jandt KD : Second generation LEDs for the polymerization of oral biomaterials. Dent Mater, 20:80-87, 2004. 155
국문초록 발광다이오드광중합기의복합레진중합평가 강지은 전새로미 김종빈 김종수 유승훈 단국대학교치과대학소아치과학교실 최근도입된광범위스펙트럼의발광다이오드광중합기는 4개의램프로구성되어있으며다양한중합모드를가지고있다. 이연구는광범위스펙트럼발광다이오드 (VALO, Ultradent, USA) 광중합기와기존의발광다이오드광중합기 (Elipar TM Freelight 2, 3M ESPE, USA) 의효율을미세경도시험을통해비교하였다. 연구에사용한광중합기는 VALO 와 Elipar TM Freelight 2이며중합시간은제조사의지시에따랐다. 37 의생리식염수에중합된레진시편을 24시간동안보관한후미세경도시험을시행하였다. 시편상부와하부의복합레진미세경도는공분산분석을시행하였다. 광범위스펙트럼의발광다이오드광중합기를이용하여고성능모드에서 4초, 플라즈마모드에서 20초광중합을실시한복합레진시편의상부는기존의발광다이오드광중합기에비해미세경도가증가하였으나 (p < 0.05), 시편의하부에서는실험에사용된광중합기간에유의성있는차이를보이지않았다. 주요어 : 발광다이오드, 광범위스펙트럼, 미세경도, 광중합기 156