PERCEPTION OF Er-YAG LASER DENTAL CARIES TREATMENT IN ADOLESCENTS-A CLINICAL EVALUATION

The aim of this study was to evaluate adolescents’ acceptance and pain perception of Er-YAG laser preparation in comparison to conventional mechanical preparation. Material and methods: Forty four adolescents between the age of 16 and 18 years with bilateral matched pairs of carious permanent molars participated in this study. In each patient one of the 2 cavities was prepared conventionally, the other with the Er-YAG laser. All cavities were restored with light-cured composite resin following the application of acid etch and a bonding agent. The patients were instructed to rate pain (sensitivity) during treatment according to visual analogue scale and to decide which method they would prefer for their future caries treatment. Results: The patients rated lower pain perception during laser treatment. It was found that 86.36 % of the adolescents indicated that they would prefer the Er:YAG laser preparation for further caries treatment. Conclusion: The application of the Er-YAG laser for carious tissue removal, compared to conventional mechanical preparation, is perceived as more comfortable and the adolescents prefer it for a future treatment.


INTRODUCTION:
Fear of pain is the main reason for many people not seeking dental care [1].Conventional mechanical cutting and drilling systems for removal of decayed tooth tissue are efficient but uncomfortable because of the vibration and loud noises that make the patients anxious.
The potential of Er-YAG laser for the ablation of hard dental structures was demonstrated in 1989 [2].Since its first introduction for dental use in 1992, Er-YAG lasers have been increasingly used in dental practice and are becoming quite a comfortable method for patients undergoing dental caries treatment [3].
Er-YAG laser radiation matches the absorption peak of water and its minimal penetration depth into enamel and dentine (5 µm -7 µm) leads to concentration of energy only to a superficial layer (4 µm -5 µm) of the exposed structures, as a large amount of this laser energy is consumed for the process of ablation, and only a minimum part re-mains for the controlled heating of tissues [4, 5, 6, 7].Thus, Er-YAG laser hard dental structures interaction can result in an efficient ablation of enamel and dentin with minimal changes on adjacent structures and without adverse effects on dental pulp [4,7].A maximum temperature in the pulp chamber during Er-YAG laser irradiation of enamel and dentin with suitable water-cooling does not exceed 3° -4° C, therefore dental manipulations can be described as safe and secure [4,8].
The Er-YAG laser application gives the opportunity of observing the rules for dental caries treatment with minimal intervention [9].Non contact method for carious hard dental structure removal induces less vibration and assures a painless and more comfortable treatment.
All properties mentioned above, make the Er-YAG laser system completely suitable for pediatric dentistry [7,10].

AIM
The aim of this study was to evaluate adolescents' acceptance and pain perception of Er-YAG laser preparation in comparison to conventional mechanical preparation.

Selection of patients
Forty four adolescents (18 male and 26 female) between the age of 16 and 18 years with a total of 88 carious lesions participated in this study.
Informed written consent was obtained for the procedure of laser and conventional treatment from each patient's parents, as required by the institution's ethics board.All the procedures were conducted in accordance with the guidelines established by the Bulgarian Ministry of Health's Code of Bioethics for Dentists and the Helsinki Declaration.
The benefits and possible side effects, such as popping sounds and the smell associated with ablation, had been fully explained.
The children presented bilateral matched pairs of carious Class I and / or Class II permanent molars.The cavities were matched according to cavity type (occlusal or proximal) and cavity depth (less than or more than half way through dentine).
All teeth were clinically free of any pathological condition different from dental caries.

Clinical design
A split mouth design of cavity preparation with an Erbium-YAG laser was used, compared to conventional dental handpieces.Cavity preparation was performed by one and the same dentist on two first or second permanent molars in each patient.One of the 2 cavities was prepared conventionally, the other with the Er-YAG laser.
For laser preparation, an Er-YAG laser (Lite Touch™, Syneron, Israel), that is a solid-state crystal laser with the host crystal-yttrium aluminium garnet doped with erbium ions that replace the yttrium ions, was used.Parameters applied were as follows: energy ranging from 100 mJ to 400 mJ, pulse repetition rate: 20 Hz, sapphire tip diameter: 1.3 mm, 1.0 mm, pulse duration: 50 ìsec, theoretical fluence: 15.05-22.61J/cm² for the dentin, 30.15-22.61J/cm² for the enamel and 12.74 J/cm² for preparing bevels on cavitiy margins, non-contact mode distance: 0.5 to 1.0 mm, air-water-spray cooling: 39 ml/min.
Cavities prepared by mechanical means involved the use of burs in high-speed and low-speed water-cooled handpieces.
The cavities were completed at two separate appointments, on different days.
No local anaesthetic was used either before or during the treatment.
The preparation was carried out under visual control according to Bjîrndal with intermittent testing of the remaining hard structure hardness by means of a dental probe [11].
All cavities were restored with light-cured composite resin (Kalore GC) following acid etching and application of bonding agent (3M ESPE Scotchbond Multipurpose).

Evaluation of pain
Immediately after laser and mechanical treatment, each patient was instructed to rate pain (sensitivity) during treatment according to visual analogue scale (VAS) from 0 to 100 points (Figure 1).
At the end of second visit (after second lesion's treatment) the patients were asked to decide which method they would prefer for their future caries treatment.
Data analysis Data were collected and evaluated using statistical software SPSS (Statistical Package version 19.0).The pain perception of patients (fig.2) during laser treatment is between no pain and mild pain.Thirty five (79.55%) of all 44 children reported no pain at all in contrast to 8 (18.18%) of children that did not feel any sensitivity during the conventional treatment (T=8.22;p<0.05).About half of the children 19 (43.18%) felt moderate pain and 4 (9.09%) reported severe pain during the conventional caries treatment although none of the children asked for local anesthesia during preparation.

Fig. 3. Distribution of children according their preferences for a future treatment method-in %
For most children 38 (86.36 %) the preferred method for a further caries treatment was the laser technology.Four (9.09 %) of them reported no difference between the two methods and 2 (4.55 %) reported the conventional tools as the preferred method for a further caries treatment (fig.3).

DISCUSSION
Pain assessment by the children using the VAS scale indicated that the laser application resulted in absence of pain or less sensitivity than the mechanical treatment.In adolescents, 79.55 % reported no pain and 11.36 % felt only a slight discomfort.
The results in this study are similar to those from other studies [12,13,14].According to Liu 82,5% of the children with carious lesions treated with Er-YAG laser, do not feel pain during treatment [13].Boj evaluated the intensity of the pain by the Wong-Baker scale during Er, Cr-YSGG laser caries treatment of 33 children aged 8-16, and found that more than 33% of children did not report pain at all and 33% felt only a slight discomfort [12].Genovese reported that during a Er, Cr-YSGG laser caries treatment in 6-12 years old children 42% of children did not indicate the presence of pain at all and 46% indicated only a slight discomfort during treatment [14].
The main factor that provokes pain and discomfort to the patient during conventional dental caries treatment is the contact between the treated surface and the used bur, leading to vibration [15].During the Er-YAG laser dental caries treatment children do not feel vibration due to the 1.Smith TA, Thompson JA, Lee WE.Assessing patient pain during dental laser treatment.J Am Dent Assoc. 1993  non-contact method used in laser cavity preparation.It has been found that high-speed drills induce 100 times higher vibration speed compared to the irradiation with Er-YAG laser.According to Takamori, this much higher frequency has its spectrum near the peak sensitivity of hearing, as a potential factor causing discomfort and pain [15].
The results of the present study clearly demonstrate that 86.36 % of children at the age of 16 -18 years assume laser preparation as more comfortable compared to the mechanical caries removal and suggest laser technology as the preferred method for future dental caries treatment.
Our results are similar to those of another study, in which 82% of the patients indicated that they would prefer the laser preparation for further caries treatment [16].Fornaini demonstrated that 89% of adult patients preferred the Er-YAG laser treatment as a means for future restorative treatment [17].
It is assumed that the noise of a conventional turbine is an important factor that causes dental phobia in clinical treatment [18].
In the present study, the most commonly reported reason for discomfort during the laser treatment is the sound of popcorn, still unfamiliar to children.

CONCLUSION
The application of the Er-YAG laser for carious tissue removal, compared to conventional mechanical preparation, is perceived as more comfortable and the adolescents prefer it for a future treatment.

Fig. 2 .
Fig. 2. Distribution of children according to the pain perception during caries treatment -in %

Table 1 .
Distribution of carious lesions according to the treatment method