Laser in dentistry Key points

Question 1

Basic components of lasers:

Answer 1

Several components are necessary to constitute a dental laser unit:

1. The optical cavity (or resonator) that includes the active medium
2. The active medium which characterizes different wavelengths of specific lasers
3. The pumping source (or energy source) to supply the energy necessary for the stimulation
4. A controller that is a software that controls the modality and parameter of laser emission and a cooler , necessary for cooling the laser system
5. The delivery system that transports the laser energy to a terminalhandpiece and tips and finally to the tissue

Question 2

Active medium used in dentistry

(know the active medium)

Answer 2

Question 3

Delivery system:

Answer 3

Once generated, laser light is delivered to the target.

Various delivery systems, depending on the wavelength carried, are:

1. Optic fiber,
2. Hollow fiber,
3. Articulated arm.

Question 4

What about dentistry?

Application in dentistry

Answer 4

1. Hard tissue (bone vs teeth).
2. Soft tissue (skin vs gingiva and other oral cavity soft tissues).

Question 5

Laser has been used in a range of dental applications.

Answer 5

In Restorative Dentistry, various types of lasers have been developed for:

1. Diagnostic purposes (e.g. caries detection).
2. Operative applications (e.g. cavity preparation, restorations, and teeth whitening).
3. Other dental applications.

Question 6

Please note, concerning application of laser in preventive dentistry:

Answer 6

Laser technology may be used as a complementary technique as well as an alternative to traditional tools, result in addition of several therapeutic advantages in restorative dentistry!

Question 7

Among them, we can consider the following advantages:

Answer 7

1. It has high affinity for carious tissues and so is selective and minimally invasive.
2. It creates macrocraters that improve the surface for bonding retention.
3. It can be used on both hard and soft tissues, including the pulp.
4. It has strong decontaminating effect.
5. It is safe due to the absence of the use of rotating instruments in the mouth.
6. It provides comfort because it works without contact and vibration on the surface.
7. It is less painful, and in many cases, the use of local anaesthetics can be avoided.
8. It has a favourable psychological impact on phobic and paediatric patients.

Question 8

Operative and Clinical advantages

Answer 8

Question 9

Possible outcomes of laser on tissue:

Answer 9

Laser may result production of several phenomenon:

1. Transmission
2. Reflection
3. Absorption
4. Scatter

Question 10

The target tissue:

Answer 10

• Substances present in most tissues of the human body, such as water, hydroxyapatite, collagen protein substances, melanin, and hemoglobin, are widely represented in the hard and soft oral tissues.
• In restorative dentistry, the main target tissues are the dental hard tissue (enamel, dentin, and decayed tissue), composed of different percentages of hydroxyapatite, water, and collagen matrix.
• From the point of view of optical physics, these components are defined as “chromophores” and have selective affinity for the wavelengths 2,780 nm and 2,940 nm of the medium-infrared spectrum

Question 11

Classification of dental laser wavelengths on the electromagnetic spectrum:

Answer 11

Laser can be distinguished according to their clinical use in dentistry in soft-tissue lasers and hard-tissue lasers, also called all-tissue lasers.

Another classification considers the position of laser wavelength** on the **electromagnetic spectrum of light.

Question 12

Classification of laser according to clinical use in dentistry

Answer 12

Question 13

Lasers for dental applications:

Answer 13

Question 14

How enamel of dentin ablation occur?

Answer 14

ERBIUM FAMILY LASER

Question 15

ERBIUM LASER
Mechanism of interaction of Erbium family lasers on hard tissue:

Answer 15

The interaction of the erbium laser with the hard tissue is the result of a complex mechanism, which involves primarily the photothermal effect and, secondarily, the photomechanical and photoacoustic effects that occur rapidly (within mS).

Question 16

Photomechanical and Photoacoustic Effects:

Answer 16

• The phenomenon that follows the primary thermal effect and the explosion of the water molecules inside the dental tissues is a secondary photomechanical effect, with a rapid shock wave that causes an expansion of the volume of the disrupted tissue..
• Which results in the destruction of the surrounding mineral matrix that explodes and is removed from the irradiated surface…
• Thus, removing the tooth structure.

*Photothermal:The first effect that determines the ablative action of the erbium family laser is a direct thermal effect on the water molecules within the dentin and enamel

Question 17

Laser parameters:

Answer 17

The laser–tissue interaction depends on the wavelength and the target tissue.
The consequent effects on tissue are closely influenced by the parameters used.

The parameters of laser used that influence the effects on the tissue are:

1. The energy emitted and its density ( fluence )
2. The frequency of pulses in the time unit.
3. The average power emitted and its density ( power density )
4. The pulse duration and peak power.

Question 18

1) Energy and Threshold of Ablation:

Answer 18

• Energy is the ability of the system to perform a task.
• The energy density (fluence) is the amount of energy emitted per unit of irradiated surface in a unit of time (expressed in J/cm 2 ).

Question 19

Density in relation to fiber tip

Answer 19

• Clinically, to consider the energy density in relation to the diameter of the fiber tip to use.
• At the same amount of energy emitted, the smallest fibers emit energy at a higher density; to have the same energy density, a larger-diameter tip requires a greater amount of energy, while less energy is needed for a smaller tip.
• Other parameters that affect the fluence are focusing or defocusing the laser beam, which, respectively, increases or decreases the density of the energy.
• As the distance between the laser tip and the target tissue increases, the fluence decreases.

Question 20

threshold of ablation

Answer 20

The minimum energy required to generate a clinical effect, ablation or vaporization, is called the “threshold of ablation”.

• The energy that does not reach the ablation threshold is called “sub-ablative”.
• So, a good knowledge of the energy values to use is necessary for a selective ablation of the enamel, dentin, and decayed tissue.
• The more energy applied, the greater the effect produced on the tissue.

Question 21

Clinical applications

Answer 21

Question 22

One of the clinical applications:

Answer 22

DIAGNOdent and DIAGNOdent-pen

Question 23

Laser Fluorescence (LF): The DIAGNOdent

Answer 23

Laser fluorescence (LF) is the most widespread laser diagnostic technology; it is a non-ablative laser device that emits a visible, red light at 655 nm.

1. First, laser identifies the fluorescence value of healthy enamel.
2. Detection of pit and fissure caries by DIAGOdent
3. Registration of numerical rate of the detection (initial healthy enamel on the left, actual value after detection).

Question 24

Cavity preparation (carious tissue ablation):

Answer 24

The Er: YAG laser was tested for preparing dental hard tissues for the first time in 1988. It was successfully used to prepare holes in the enamel and dentine with low ‘fluences’ (energy (mJ)/unit area (cm2)).

• Even without water-cooling, the prepared cavities showed no cracks and low or no charring, while the increase in the mean temperature of the pulp cavity was about 4.3 C).
• In 1989, it was demonstrated that the Er: YAG laser produced cavities in the enamel and dentine without any major adverse side effects.

Er: YAG is the first option for ablation
Why? Because it will deliver a lot of energy (photoacoustic, photothermal etc

Question 25

-Restoration removal:

Answer 25

The Er: YAG laser is capable of removing cement, composite resin and the glass ionomer. Only? ..

• The efficiency of the ablation is comparable to that of enamel and dentine. Lasers should not be used to ablate the amalgam restorations, however, because of the potential release of mercury vapour.
• The Er: YAG laser is incapable of removing gold crowns, cast restorations and ceramic materials because of the low absorption of these materials and the reflection of the laser light. These limitations highlight the need for adequate operator training in the use of lasers.