of Er:YAG Laser in Conservative Dentistry and Adhesion Process

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© Springer Nature Switzerland AG 2020

S. Stübinger et al. (eds.)Lasers in Oral and Maxillofacial Surgerydoi.org/10.1007/978-3-030-29604-9_7

7. Use of Er:YAG Laser in Conservative Dentistry and Adhesion Process

Gianfranco Semez1   and Carlo Francesco Sambri1
(1)

Semez srl, Trieste, Italy
 
 
Gianfranco Semez

Abstract

This chapter deals with the use of Er:YAG laser in conservative laser dentistry as well as its part in the interaction with the adhesion process. Er:YAG laser is helpful in conservative dentistry. Its property to be absorbed by water and apatite can help clinicians in selective and microinvasive decay removal from tooth structure. The importance of using repeatable clinical protocol, to obtain a very strong adhesion effect with materials, brings medium- and long-term results of efficacy in conservative rehabilitations. The precision of the laser beam and its selectivity give the possibility to create new shapes for conservative cavity preparation.

Keywords

Er:YAG laserConservative dentistryMicro leakageAdhesionThreshold ablation

7.1 Er:YAG Laser Interaction with Enamel and Dentine

Up until today, preservative dentistry has been defined as that branch of dental practice that concerns all clinical procedures carried out with a view to preserving natural teeth and ensuring their functioning within a framework of preserving both oral health and the overall health of the patient (definition: School of Dental Medicine at the University of Geneva). Within that framework, we can define what are the real aims of preservative dentistry thanks to the current expertise and technology in the field of the treatment of hard dental tissue that we have set out to achieve:

  1. 1.

    Prevention and the safeguarding of the integrity of the tooth: the techniques and procedures carried out on the patient with a view to reducing the amount of cariogenic bacteria in the mouth in order to reduce the incidence of disturbances to the enamel and dentine tissue.

     
  2. 2.

    Curative treatment and restoration: microinvasive techniques for the removal of infected tissue and the use of selective long-wave laser for tissues with a greater water density may be useful in minimizing the sacrifice of healthy tissue during the process of ablation in order to preserve the architectonic structure of the tooth.

     
  3. 3.

    Restoration of lost tissue: the adhesive techniques that have now become part of the normal routine in our work allow and, indeed, oblige us to exploit any portion of healthy tissue remaining in order to ensure the preservation and restoration of the tooth. The use of laser and ER:YAG in order to improve the process of adhesion and micro-infiltration at a marginal level both on the enamel and the dentine.

     
  4. 4.

    Maintenance of dental health: checking up on the maintenance of the suitable margins of the reconstructions, the physiological wear and tear that result from chewing, and the duration of the adhesive interface in subsequent years is a fundamental step in the mechanical maintenance of conservative restoration [1].

     
The definition of an adequate plan of conservative treatment entails certain fundamental steps, the first of which is the identification of the major problems involved in the conservation; subsequently, it is necessary to treat urgent problems as quickly as possible to obviate the progression of penetrating tooth decay, deep-rooted dentine traumas, etc.; the use of X-rays for an early diagnosis of interproximal tooth decay is still a fundamental step in any complete and precise intervention; a periodontal evaluation concludes the total diagnostic process following the restoration project (Fig. 7.1).

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Fig. 7.1

Spectrum of light

At this point, the optimal characteristics of a laser instrument should be:

  • Cutting precision,

  • Interactive selection with the tissue,

  • Mini-invasiveness,

  • Safety,

  • Patient comfort,

  • Compatibility with state-of-the art adhesive systems.

In order to make a cautious choice, we need to know the different wavelengths of the lasers so as to decide which is the most suitable for the abovementioned parameters.

In order to satisfy these requirements, we need to use a laser in which the predominant feature is the absorption of the rays on the tissue. In this respect, the wavelengths that best fit this requirement are ultraviolet wavelengths of between 190 and 300 nm, such as the excimer lasers used in ophthalmology because of their high rate of energy or infrared lasers such as CO2, Ho:YAG, Er:YAG, and Er-Cr:YSGG of between 2000 and 11,000 nm.

The penetration depth of these lasers is very slight, between 1 and 100 μm; the diffusion element is basically irrelevant, and there is no retro-diffusion.

In light of these considerations in the course of our work, we have chosen the Er:YAG 2940 nm laser for work on the hard tissue of the tooth.

To obtain a correct photo-ablative alignment, the choice of the parameters is absolutely fundamental. The relation between power density, exposure time, and length of pulsation makes a significant difference in the efficacy of our operation. As shown in Fig. 7.2, it is only a correct balancing of these parameters that will lead to obtaining a process of real photo-ablation, called by some authors “cold-ablation” (Fig. 7.2).

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Fig. 7.2

Laser–tissue interaction on power density and time of exposure

The removal of the decayed tissue is facilitated by the use of the Er:YAG laser because the central parts of the decayed area contain more water than the surrounding tissue. Given the physical properties of the erbium laser for the absorption of water, we can verify clinically a certain selectivity for the decayed tissue (Fig. 7.3).

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Fig. 7.3

Macro anatomy of decay lesion

Considering the various anatomical components that make up the tooth, the action of the laser will differ according to the work to be done on enamel or dentine tissue.

Enamel: a mineralized acellular secretion with a very high component of inorganic material (96%), a very low organic component (1%), and a low water content (3%) (Fig. 7.4).

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Fig. 7.4

Enamel structure anatomy

Dentine: a mineralized cellular tissue made up of three phases:

  • A mineral phase composed of around 50% apatite.

  • An organic phase of around 30% represented for 90% by type 1 collagen and 10% by non-collagen proteins as well as lipids.

  • A watery phase of 20%, 75% of which is present within the dentine tubes and 25% mineralized matrix that varies according to the anatomical area [2].

The dentine tubules, hollow structures that run through the dentine tissue in a centripetal direction toward the pulp chamber, represented by a number between 20 and 45,000/mm2, with a diameter comprising from 1 to 3 μm, contain the processes of odontoblasts, lamina sslimitans, collagen, fibers, dentine fluids, proteins, etc. There are also present numerous ramifications and anastomosis with a smaller diameter of between 50 nm and 1 μm.

The dentine is subdivided into three parts:

Intertubular dentine within the tubules: characterized by a large quantity of water, type 1 collagen fiber, non-collagen proteins, lipids, and odontoblastic processes (Fig. 7.5).

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Fig. 7.5

Intertubular dentine and its composition

Intratubular dentine: characterized by presence of type 1 collagen fiber, crystalline structure, non-collagen proteins, lipids, and water.

Peritubular dentine: hyper-mineralized dentine, around 40 times more mineralized than the preceding examples, characterized by a thickness that varies between 1 and 3 μm and a dense, homogenous structure characterized by hydroxyapatite crystals and no collagen (Fig. 7.6).

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Jul 23, 2021 | Posted by in Oral and Maxillofacial Surgery | Comments Off on of Er:YAG Laser in Conservative Dentistry and Adhesion Process
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