Fiber laser applications in dentistry

Abstract

The employment of laser in dentistry may be summarized in three main targets: - hard dental tissues (teeth, bone): the clinic utilization includes mainly the conservative dentistry and the bone surgery and it may be performed only by the Erbium family lasers (Er:YAG and Er,Cr:YSGG). - soft dental tissues (vascularized and keratinized gum): its applications consist of the oral surgery interventions and normally Nd:YAG, CO2 and diodes are the first choice lasers. - ceramics surfaces (etchable and non etchable porcelain): its employing is related to the characterization of the internal surfaces of ceramic prosthetics to enhance the adhesion to the teeth and the CO2, Nd:YAP and Nd:YAG laser are utilized. By these considerations, it arises that the possibility to have wavelengths able to be effective in all the three targets described might be a great success and the aim of this study is to evaluate the effectiveness of the use of fiber lasers for dental applications, particularly on soft tissues, hard tissues and ceramic surfaces. The device used for the tests is a 1070 nm pulsed fiber laser (AREX 20, Datalogic, Italy) available in the Photonic Devices Lab at the Engineering and Architecture Department. This source has a maximum average output power of 20 W and a fixed pulse time duration of 100 ns, while the repetition rate ranges from 20 kHz to 100 kHz. The first step of this work is to analyse the behaviour of fiber laser on oral soft tissues beyond ex vivo tests performed on samples obtained by bovine tongues. Thermal elevation during irradiation was recorded by a Fiber Bragg Grating (FBG) temperature sensor connected to an interrogator while tissue modifications evaluation with a qualitative microscopic observation and a score assigned by a blind pathologist to the incisions made by different parameters. The second series of tests is focused on di-silicate ceramic samples and, beyond thermal recording performed by FBG interrogator, the morphological analysis of the surface is observed by SEM as well as elemental composition by EDS to investigate the possible structure modifications induced by laser irradiation. A third session of experiments is conducted on dentinal sections of extracted human teeth to verify the possibility of fiber laser ablation on hard dental tissues; even if the results are not encouraging, it is appreciated the capability to perform a “dentinal welding”, also using Hydroxyapatite as filler. One more topic treated in this thesis is the prototyping of a new laser device to intraorally use for the so-called “at home therapy” based on “random laser” technology and, in the last chapter, a description of all the steps for arriving to project this appliance are described.