The Detection of Carious Lesion Porphyrins Using Violet Laser Induced Fluorescence

U istraživanju se željelo odrediti spektralna područja za lasersku ekscitaciju otopina protoporfirina IX (PP-a), koproporfirina (CP-a) i uroporfirina (UP-a) s različitim pH-vrijednostima. Drugi je cilj bio usporediti spektre laserski inducirane fluorescencije (LIF-a) otopina PP-a, CP-a i UP-a različitih pH-vrijednosti s fluorescencijom prirodne karijesne lezije i rezultatima ostalih istraživanja. Materijali i postupci: Apsorpcijski spektri otopina PP-a, CP-a i UP-a s pH-vrijednostima u rasponu od 0,6 do 13 izmjereni su spektrofotometrom (model Varian). Laser od 405 nm (10mW) odabran je prema najvišoj apsorpciji porfirina za mjerenja spektra laserski inducirane fluorescencije (LIF-a) PP-a, CP-a i UP-a te prirodne karijesne lezije. Rezultati: Ovisno o pH-vrijednosti, LIF-ove otopine PP-a, CP-a i UP-a pokazuju pomak prema višim valnim duljinama. U kiseloj otopini PP-a uočeni su fluorescencijski vršci na 601 nm i 655 nm nakon ekscitacije lasera na valnoj duljini od 405 nm. Zaključak: In vitro mjerenja LIF-a porfirinskih otopina ljubičastim laserom pokazuju sličnosti s valnim duljinama prave karijesne lezije i vrhovima fluorescencijskih vrpci prirodnih zuba poznatih iz literature. Ipak, fluorescencija testiranih porfirina ne objašnjava potpuno fluorescencijske spektre zubnog karijesa te su potrebna daljnja istraživanja. Čini se da pH ima važan utjecaj na svjetlosnu apsorpciju i emisiju porfirina.Objectives: The aim of the study was to establish spectral regions for laser excitation of protoporphyrin IX (PP), coproporphyrin (CP) and uroporphyrin (UP) solutions under different pH conditions. The second aim was to compare laser induced fluorescence (LIF) spectra of PP, CP and UP solutions with various pH to the fluorescence of natural carious lesion and the results of other studies. Materials and methods: Absorption spectra of PP, CP and UP solutions with pH values in range from 0.6-13.0 were taken on a Varian model spectrophotometer. According to the peak absorption of the porphyrins used, laser at 405 nm (10 mW) was selected for LIF measurements of PP, CP and UP solutions, as well as the natural carious lesion. Results: Depending on the pH value, the LIF of the PP, CP and UP solutions exhibited the red shift toward higher wavelengths. Using excitation at 405 nm laser wavelength, fluorescence bands peaking at 601 nm and 655 nm of the acidic PP solution were observed. Conclusions: Violet LIF peaks of porphyrin solutions measured in vitro are similar to the wavelengths of a real carious lesion and fluorescence band peaks of natural teeth known from literature. However, the fluorescence of tested porphyrins does not completely explain the fluorescence spectra of dental caries and further studies are needed. pH seems to have an important influence on the light absorption and emission of porphyrins

Laser Induced Fluorescence of Carious Lesion Porphyrins

Svrha: U radu su predstavljeni preliminarni rezultati mjerenja laserski inducirane fluorescencije u nekoliko porfirinskih otopina. Koproporfirin i uroporfirin sastavni su dijelovi karijesnih lezija. Njihovo svojstvo fluorescencije pri obasjavanju svjetlom određene valne duljine može se uporabljati kao način detekcije karijesnih lezija. Materijali i postupci: U otopinama koproporfirina i dihidroklorida te uroporfirina i dihidroklorida s različitim pH-uvjetima izmjereni su apsorpcijski koeficijenti kako bi se identificirale spektralne regije za učinkovitu ekscitaciju laserima. Za indukciju fluorescencije odabrani su laseri s diskretnim valnim duljinama na 420 nm, 473 nm i 532 nm. Rezultati: Kod svih laserskih valnih duljina uočena je zanimljiva fluorescencijska emisija na 591 nm, 619 nm i 652 nm za koproporfirin i na 617 nm i 680 nm za uroporfirin. Zaključak: Kada se emisije svih porfirina međusobno kombiniraju, trebali bi odgovarati spektralnim strukturama koje se mogu naći u stvarnim karijesnim lezijama.Objectives: This paper reports the preliminary results of the measurements of laser induced fluorescence in several porphyrin solutions. Coproporphyrin and uroporphyrin are common constituents of carious lesions. Their property to exhibit fluorescence when irradiated with a light of certain wavelength could be used as a means to detect carious lesions. Materials and methods: Absorption coefficient measurements of coproporphyrin I dihydrochloride and uroporphyrin I dihydrochloride solutions were performed under different pH conditions in order to identify spectral regions for effective laser excitation. Lasers with discrete wavelengths at 420 nm, 473 nm and 532 nm were used for the induction of the fluorescence. Results: At all laser wavelengths interesting fluorescence bands peaking at 591 nm, 619 nm and 652 nm for coproporphyrin and at 617 nm and 680 nm for uroporphyrin were observed. Conclusions: When combined together all bands should correspond to the spectral band structures found in real carious lesions