The Use of the Er:YAG Laser 2940 nm in complex caries removal

Treatment plan for this patient presented proximal cavity preparation with laser. Laser assisted approach will be performed to minimalize the loss of hard tissues and negative perceptions of dental treatment. It is considered appropriate to ablate the healthy enamel to make access to the carious lession and to remove infected dentine.

Treatment plan outline:
General: The aim of this treatment is to replace aesthetic composite restoration after removal of all carious tissues. Enamel will be etched using 37% phosphoric acid, bonded and restored using light cured nanocomposite material (Gaenial, GC, Japan). The margins of the cavity in enamel would be finished with a red round bur prior the etching, to create a smooth margin and therefore better marginal adhesion and aesthetics.
Specific: In order to reach minimal sensitivity and minimally invasive approach, laser assisted treatment will be used. Dental tissue preparation will be performed using Er:YAG laser of 2940 nm .

Indications:
Treatment: The conventional “drill & fill” approach is being to be eliminated by increasing use of laser in the field of hard dental tissue ablation. Laser hard tissue management is a good choice as it provides comfort because it works without contact and vibration on the surfaces. This makes the treatment more pleasant for patient. In consequence it is less painful, and in many cases, use of local anaesthetics can be avoided. It has a favourable psychological impact on phobic and pediatric patients, so it is accepted better from the patient site. Laser technology may be used as alternative to traditional tools adding therapeutic advantages in restorative dentistry. Delivered energy has high affinity for carious tissues so it is selective. It can be used on all hard dental tissues, has strong decontaminating effect and minimize the creation of debris during the dental ablation. In case of present carious tissues, the ablation is selective due to the content of the water, which is the main chromophore. The laser irradiation provides significant reduction of pathogen presented in remaining tissues. Clinical advantages includes clean surface, without smear layer what is ideal for adhesion. Smaller rise in temperature in pulp and periodontal surface during irradiation makes this treatment modality safer towards to pulp tissues. Surface absorption of Er:YAG provide the control of penetration depth during the hard tissues preparation.
Laser: The interaction of the erbium family lasers with the hard dental tissues causes primarily photothermal effect and secondarily, the photomechanical and photoacoustic effect that occurs rapidly. First effect during ablative action of the erbium family laser is direct thermal effect on the water molecules within the dentin and enamel. The rapid temperature increase up to boiling point of water causes an increase of pressure and when it exceeds the structural tension of surrounding tissues, microexplosion within the tissue can occur. The richer the tissue is in water, the more quickly it reacts with laser energy.(1)
Wavelength: The predominant chromophores for the chosen wavelength in this case is the water. The use of a Free Running Pulse (FRP) erbium family laser is indicated as it can achieve ablation of hard tissue. In this case 2940 nm Er:YAG will be used with a Micro Short Pulse MSP (width 100 microseconds).

Contraindications:
General contraindication for the intervention present mental disorders and disability to cooperate during the intervention.

Treatment:
For the specified treatment there are no definite contraindications. The laser use has to be considered in case of amalgam restoration present in the preparation field or its proximity. In this case the proper isolation must be assured, or amalgam must be removed using rotary instruments. The presence of other metal restorations or prosthetic work can limit the use of laser. Cavity with underrunning carious tissues where extension of affected dentine is bigger than healthy enamel must be open more during the laser preparation. Laser beam can ablate tissues which are in the direct beam area only. It is almost impossible to remove underlying infected hard tissues when access cavity is not opened proportionally to the extension of the infection.
Laser: Surgery using MIR ( mid infra red) laser energy carries minimal risk of collateral damage on soft tissue and overheating of the pulp because “what you see is what you get”.
Wavelength: The choice of the wavelength is dependent on the tissue characteristic and the needed effect. The wavelength with deeper penetration could cause deeper damage. To avoid overheating of the tissues, it is necessary to use air/ water cooling during the intervention. There is no contraindication for the use of Er: YAG laser to carry this set of procedures. The laser of choice is erbium family lasers: 2780nm for ErCr: YSGG, 2940 nm Er:YAG or CO₂ laser 9300 nm.

Precautions:
Laser approach: The laser user should keep in mind the benefits and potential complications using the laser. Safety rules concern eye protection to avoid possible eye damage of patient or dental team members.Patient comfort during the laser intervention is higher, due to the non-contact approach. There is still a minimal distance (1-2mm) kept between the tissue and laser tip hand piece when using a cylindrique tip (8mm ,Æ1.3mm). Wavelength of 2940 nm with penetration of 3-5 micrometres can rise up the temperature of the affected tissues high above the level of carbonization. To avoid the tissue damage and reduce the collateral heath transfer, it is necessary to use the air/water cooling hand in hand with minimum power parameters and time intervals to allow the thermal relaxation of the tissues.

Treatment alternatives:
Alternative method for hard dental tissue preparation is use of bur in angle handpiece. Conventional cavity preparation with rotary instruments could be take in consideration. Infected soft dentine can be removed using the hand excavator. The traditional approach is not in favour of the patients.

Informed Consent:
The treatment plan was fully explained to the patient and all associated risks were outlined. She was also made aware of alternative treatments. A written consent form was signed by the patient and was added to the patient’s documentation.

Treatment objectives:
The objective of this treatment would be to effective hard tissue ablation 15 with 2940 nm erbium laser. After the laser approach, the new aesthetic composite restorations will be placed.

Laser Operating Parameters:
Laser:
× Erbium laser: LightWalker AT, Fotona, Slovenia
× Wavelength: 2940 nm
× Aiming beam is semiconductor diode laser with wavelength 532 nm
× Emission mode: Free Running Pulse
× Maximum power output: 20.0 watts
× Delivery system: sapphire tip (spot size Æ1300 µm) ( Figure 3) articulated arm
Preliminary to patient treatment:
× Secure the operating room, define controlled area and proper laser warning signs
× Set up laser and test of the proper laser operation
× Test-fire laser and water/air flow
× Review the patient file and radiograph
× Patient seated: review treatment plan and informed consent
× Place the rubber dam isolation
× Safety: Patient first follow by the dental team members place the eye protecting goggles

Treatment delivery sequences
Treatment Sequence for enamel and dentin ablation For laser ablation of enamel and carious dentine of the left upper second premolar Er: YAG 2940nm laser was selected. No anesthesia was administrated. The shallow depth of beam penetration of chosen wavelength allows the operator good control of depth of preparation. For both hard tissues water and air cooling was applied. For this procedure, handpiece with the sapphire tip was chosen. To ablate the enamel 250 mJ per pulse with 100microsecond pulse width was used. Lower setting for carious dentine were chosen, 155mJ per pulse, 300 microsecond pulse width. After the cavity cleaning and contamination control, the coronal enamel margin was finished with the red diamond bur to adjust the chamfer ( 20 000 rpm 5:1). The surface was etched (37% phosphoric acid), bonded with the 5th generation bond and restored with the composite material (Gaenial, GC, Japan). (Figure 4-7).

Complications:
Pre-operation significant hypersensitivity could influence the treatment. The age of the patient, morphology of dentinal tubules and pulp cavity be reason of higher sensitivity. Laser induced analgesia or chemical anesthesia could be applied. In this case, it was not present. Another complication during the ablation is possible bleeding from the interdental papilla when not using the isolation. This can be managed using NIR wavelengths or chemical haemostatics. Laser beam reflection can cause the ablation of the other structures. All needs to be isolated well. In this case, no complications were encountered.

Prognosis:
Laser-assisted hard tissues procedures, using correct settings and parameters, approach and technique have a very good prognosis. It is comfortable treatment modality for patient.

Follow-up care:
No long term complications were observed.