DOI: 10.1007/s00339-004-2661-7 Appl. Phys. A 79, 887–889 (2004) Materials Science & Processing Applied Physics A t. dost ´ alov ´ a 1, ✉ h. jel´ inkov ´ a 2 j. ˇ sulc 2 m. n ˇ emec 2 p. koranda 2 m. barto ˇ nov ´ a 1 p. radina 1 m. miyagi 3 y.-w. shi 3 y. matsuura 3 Surface modification of tooth root canal after application of an X-ray opaque waveguide 1 Charles University, 1st Medical Faculty, Department of Stomatology, GFH, Kateˇ rinsk´ a 32, 12000 Prague 2, Czech Republic 2 Czech Technical University, FNSPE, Bˇ rehov´ a 7, 115 19 Prague 1, Czech Republic 3 Tohoku University, Graduate School of Engineering, Department of Electrical Communications, Sendai 980–8579, Japan Received: 4 September 2003/Accepted: 4 February 2004 Published online: 26 July 2004 • © Springer-Verlag 2004 ABSTRACT The interest in endodontic use of dental laser sys- tems has been increasing. With the development of thin and flexible delivery systems for various wavelengths, laser appli- cations in endodontics may become even more desirable. The aim of this study is to check the X-ray opacity of a hollow wave- guide and to observe the results after laser root canal treatment. The root canal systems of 10 molars were treated endodonti- cally by laser. For the laser radiation source, an Er:YAG laser system generating a wavelength of 2940 nm and an Alexandrite laser system generating a wavelength of 375 nm were used. The hollow waveguide used was checked under X-ray. A root canal surface treated by laser radiation was analyzed by a scanning electron microscope (SEM). The special hollow glass wave- guide used was visible in the root canal system under X-ray imaging. Surface modification of the root canal after laser treatment was not found. After conventional treatment the root canal was enlarged. The surface was covered with a smear layer. After ap- plication of both laser systems, the smear layer was removed. The resulting canal surface was found to be clean and smooth. Under SEM observation open dentinal tubules were visible. No cracks were present, nor were surface modifications observed. PACS 42.62.-b; 42.62.Be; 42.81.Qb 1 Introduction The interest in endodontic utilization of dental laser systems has been increasing. Developing laser technol- ogy and a better understanding of laser effects have widened the spectrum of possible endodontic applications [1]. Various laser systems including excimer, argon, CO 2 , diode, Nd:YAG, and Er:YAG lasers are used in pulp diagnosis, treatment of hy- persensitivity, pulp capping, sterilization of root canals, root canal shaping, and obturation or apicoectomy. With the de- velopment of thin and flexible delivery systems for many different wavelengths, laser applications in endodontics will become even more desirable. So far, three different delivery systems exist. They are an articulated arm, optical fiber, and hollow waveguide. It is known that the mobility of the artic- ulated arm is limited and the optical fiber lifetime is still an ✉ Fax: +420-221/912-252, E-mail: t.dostalova@quick.cz open question, especially when high-power pulses have to be delivered [1]. A more complicated situation emerges when the intervention is to be applied inside a human body. In this case, only the fiber or waveguide could be applied for radia- tion delivery. Up to now, neither fiber nor the hollow waveguide are X-ray opaque and, therefore, contrary to classical metal in- struments, they are not visible in an X-ray image. The aim of our study is to check the X-ray opacity of the hollow waveguide and to observe the results after laser root canal treatment. 2 Experimental arrangement 2.1 Tooth material The root canal systems of 10 molars were treated endodontically. This means that access cavities were prepared and the tooth canal systems were shaped using a step-back technique with K-type endodontic files (Maillefer, Swiss). This shape was prepared by using conventional files from 10 to 55 applied from the body to the apex. A gates burr was placed loosely in the middle third of the canal system and al- lowed to contact the canal walls to smooth and slightly flare the preparations. A 5.25% solution of sodium hypochloride (10 ml) (Clordent, C.S.C. Czech Rep) was used to irrigate all the root canal systems between the uses of each endodontic instrument. 2.2 Laser equipment and experiment preparation As the laser radiation source, a laboratory built Er:YAG laser system [3] generating a wavelength of 2940 nm (frequency 1.5 Hz, spot size 320 μ m, number of pulses 55, energy 100 mJ) and an Alexandrite laser system [4] generat- ing a second harmonic radiation with a wavelength of 375 nm (frequency 1 Hz, spot size 320 μ m, number of pulses 200, en- ergy 1 mJ) were used. The waveguide system [5] consists of a supporting fused silica glass capillary tube with a silver layer deposited on the inside wall coated by a COP-E48R film of thickness around 0.1 μ m. The outer surface was specially modified (stainless- steel layer) to obtain opacity for X-ray radiation. The in- ner diameter of the waveguide was 320 μ m, outer diameter 630 μ m, and its length 100 mm (Fig. 1). After delivery of a se- quence of pulses, the input waveguide end was investigated.