Usporedba standardne i pulsno-laserske polimerizacije kompozitnih materijala

Abstract

An ever growing amount of photo-curable materials is being used in different fields of dentistry. Standard photopolymerization devices produce about 60% o f monomer conversion in composite resin fillings. In order to improve the quality of polymerization, a series of experiments was made using pulsed laser, because continuous coherent light leads to a higher polymerization shrinkage caused by a temperature rise in the material. Three different experiments were carried out with different shades of composite resins Helioprogress and Heliomolar (Vivadent, Liechtenstein). In the first experiment, the wavelength was changed from 465 to 495 nm in steps o f 5 nm with 30s exposition time. In the second one, the wavelength was constant (470 nm) and the illumination time was changeable (10, 20, 30 and 40s). The cured part of the sample, situated in a specially prepared aluminum mould, was measured with Vernier micrometer. The best results were achieved at 470 nm regardless of the amount of filler and pigment. The results were compared with a commercial device (Heliomat). It is expected that pulsed laser polymerization will improve the degree of monomer conversion, decrease a temperature rise in the composite and in that way avoid wall-to-wall contraction.Zbog širokog uporabnog spektra, jednokomponentni smolasti materijali postali su gotovo nezamjenjivi u raznim stomatološkim disciplinama. Standardni polimerizacijski uređaji osiguravaju svega 60%-tnu konverziju monomera, dok argonski laser uzrokuje veći stupanj polimerizacijskog skvrčavanja kao rezultat povišenja temperature na mjestu apsorpcije. Stoga su, prvi put, izvedeni pokusi polimerizacije kompozita pulsnim laserom (XeCl Lambda- Physik L P X 100). Korištene su različite boje kompozitnih materijala Helioprogress i Heliomolar (Vivadent, Liechtenstein). U prvom pokusu, eksperimentirano je sa sedam valnih duljina u rasponu od 465-495 nm pri ekspoziciji od 30s, dok je u drugom valna duljina bila nepromjenljiva (470nm) uz različito vrijeme osvjetljavanja od 10, 20, 30 i 40 s. Polimerizirani dio uzorka, smješten u posebno pripremljenom aluminijskom kalupu, mjeren je pomičnim mjerilom, nakon temeljitog odstranjenja mekog dijela kompozita. Zamjetna je najveća dubina polimerizacije u području oko 470 nm bez obzira na količinu punila i pigmenta. Dobiveni rezultati uspoređeni su s kontrolnim mjerenjima izvedenim halogenom žaruljom (Heliomat). Rad u pulsnom režimu pri određenoj valnoj duljini, mogao bi znatno poboljšati stupanj konverzije monomera, smanjiti temperaturni porast u materijalu i na taj načm reducirati polimerizacijsko skvrčavanje