8.1 Laser and Hypersensitivity

Dental hypersensitivity (DH) , defined as “a short sharp pain arising from physical or chemical stimuli which cannot be ascribed to dental pathologies” in 2003 by the Canadian Advisory Board, is a highly relevant and widespread problem among dental patients. Such pain, often described as short and sharp, can be ascribed to thermal stimuli, mechanical contacts, osmotic variations (e.g., drying of the surface of exposed dentine), or chemical stimulations (e.g., sugary or acid foods). According to the hydrodynamic theory already expounded at the beginning of the last century by Brannstrom, these stimuli would create a movement of the intratubular fluid that would stretch the nerve fibers within the processes of the odontoblasts contained in them.

Exposed dentine is often due to periodontal disease and is particularly related to gum recession in thin gingival biotypes, while it becomes a matter of resective periodontal surgery in patients undergoing such procedures for the maintenance of the health of the periodontium. It is estimated that between 60% and 98% of patients are affected by periodontal disease with a loss of teeth, and undergoing resective therapies present varying degrees of dentine hypersensitivity.

Other situations that can be correlated to DH are the loss of dental tissue in the cervical region due to abrasions caused by mechanical traumas (e.g., incorrect brushing) or abfractions often found in patients affected by chewing parafunctions. Less common are pathologies linked to odontogenesis (e.g., amelogenesis imperfecta) or erosions due to chemical traumas (e.g., patients with eating disorders such as anorexia and/or bulimia).

For these reasons, nowadays, numerous systems are used with a view to obliterating the dentine tubules themselves so as to eliminate the movement of fluid and the consequent algic symptoms demonstrated by the affected teeth.

Following one of the various treatment protocols mentioned in previous studies, it is first of all important to identify and, where possible, to eliminate the root cause of DH. In the second place, chemical products such as KNO₃ and KCl are used in order to relieve the pain. If these preventive and curative measures should not produce satisfactory results, it is necessary to proceed with the obliteration of the dentine tubules.

There are numerous techniques proposed for this procedure including the following:

The light of the laser by transmitting energy under the form of photons (photonic energy) makes it possible, according to the characteristics of the laser itself, to have a direct effect on the exposed dentine or to activate an appropriately treated desensitizing chemical product.

8.1.1 Nd:YAG Laser: LITS Technique

The Nd:YAG laser is considered a high-energy laser in that the modality of the ray properly called a pulsate or super pulsate allows the built-up energy to be emitted in very high quantities (peak power of very high pulsations) in an extremely short time (short pulse duration). This binomial of energy and exposure time allows the wavelength to alter irreversibly the irradiated dentine surface without however transmitting the heat produced to the deep tissue and in particular to the pulp tissue which is extremely sensitive to rise in temperature.

This process, defined as the photothermal effect, consists in the absorption of the energy of a photon on the part of a target molecule which creates an increase in the molecular vibrations and is translated into the production of heat and a rise in temperature. The Nd:YAG laser, thanks to its type of pulsate emission, produces this effect, and thanks to the brief duration of the pulsation, the rise in temperature is not translated into the scattering of heat toward the pulp. This rise in temperature allows a permanent alteration of the architectonic structure of the irradiated dentine tissue, thus giving rise to dentine melting that obliterates the tubules very effectively. This process can be carried out clinically only in the presence of a suitable chromophore placed on the surface to be treated, in this specific instance on the graphite opportunely applied. The procedure we propose is the following (Fig. 8.1):