Er-YAG LASER AND DENTAL CARIES TREATMENT OF PERMANENT TEETH IN CHILDHOOD

The aim of this study was elaboration, approbation in a clinical situation and monitoring of the optimized protocol for application of Er:YAG laser “Lite Touch” in dental caries treatment of permanent teeth in children. Materials and methods: Fifty children between the age of 6 and 16 years with at least one bilateral matched pair of one type cavitated carious lesions in permanent teeth were included in the 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. Postoperative hypersensitivity, secondary caries and marginal morphology of restoration were evaluated. Results: No postoperative sensitivity and secondary caries in all children at the 2-year follow-up examination were observed. It was found that 94.83 % of restorations in Er:YAG laser treated carious lesions were clinically acceptable and no one of the restorations was lost. Conclusion: There is no difference with regard to the clinical success between laser and conventional treatment. The protocol with Er:YAG laser “Lite Touch” parameters used can be recommended in the dental practice for caries treatment of permanent teeth in childhood.


INTRODUCTION:
Er:YAG laser is one of the most suitable laser systems that could be used in dental caries treatment in childhood.Its higher safety compared to conventional techniques because it does not use rotating instruments in a small mouth which can move unpredictably [1], its minimally invasive nature because of the affinity of the laser beam for carious structures and decontamination of ablated dentin [2,3], the possibility for achieving an effective ablation without thermal negative effects on underlying structures and tissues [4,5], the increased children cooperativeness during the caries treatment process because of the non contact method used that induces less vibration and provides a painless and more comfortable treatment [6, 7, 8] are only a small part of the Er:YAG laser advantages described in the literature.
The laser ability to remove hard dental structures depends on different factors such as water and fluoride content of the target tissue, and laser parameters including en-ergy, pulses per second, water spray, the tip material, shape and diameter [9,10].
Different studies reported very good clinical results after using of Er:YAG laser in the caries treatment in adults [11,12].However, there is a lack of clinical studies in the literature with regard to the Er:YAG laser application in dental caries treatment in childhood.
The aim of the recent study was elaboration, approbation in a clinical situation and monitoring of the optimized protocol for application of Er:YAG laser "Lite Touch" in dental caries treatment of permanent teeth in children.

Tasks:
1. Proposal for a protocol with recommended Er:YAG laser parameters for cavity preparation and removal of carious hard dental structures in permanent teeth in children; 2. Assessment of the clinical success of Er:YAG laser caries treatment after applying of the same protocol in dental clinical practice.

MATERIALS AND METHODS:
Fifty children (21 male and 29 female) between the age of 6 and 16 years with a total of 116 cavitated carious dentinal lesions participated in this study.Of these, 24 children were aged from 6 up to 11 and had 48 cavitated carious dentinal lesions on first permanent molars and 26 children were aged from 12 up to 16 and had 68 carious dentinal lesions on first incisors, canines, first and second permanent molars.
Inclusion criteria: -good general health; -at least one bilateral matched pair of one type cavitated carious lesions with regard to: -the tooth -incisors, canines, premolars or molars; -location of the lesion -cervical, occlusal or proximal; -cavity depth -less or more than second half of dentine.
Exclusion criteria: -symptoms (evidence) of complicated caries (pulpitis or apical periodontitis); -poor oral hygiene.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.
Ten permanent incisors, 6 upper permanent canines, http://dx.doi.org/10.5272/jimab.2015211.699 44 lower first permanent molars, 30 upper first permanent molars and 26 lower second permanent molars cavities were prepared.Sixteen of the lesions were in the cervical area of teeth, 38 were proximal lesions and 60 occlusal lesions.Thus, all three possible types of carious lesions were prepared using the laser.Ninety four of the lesions were at the dentin-enamel junction and the remaining 22 in the second half of the dentin.A split-mouth design was used.One of the cavities was prepared conventionally, the other with an Er:YAG laser in each patient.
For laser preparation, an Er:YAG laser (Lite Touch™, Syneron, Israel) with a wavelength of 2940 nm and pulse duration: 50 ìsec.tat is a solid-state crystal laser with the host crystal-Yttrium Aluminum Garnet doped with Erbium ions that replace the Yttrium ions was used.
Hard dental structures' ablation is getting performed with a sapphire tip, working distance of 0.5-1.0mm and airwater cooling of 39 ml/min.The clinical protocol with recommended Er:YAG laser Lite Touch parameters was drawn on the base of our previous Scanning Electron Microscope (SEM) and Raman and Infrared reflection microspectroscopic study on permanent human enamel and dentin [13,14].Parameters of the laser used in carious lesions treatment of permanent teeth are presented on table 1: Table 1.Protocol with Er:YAG laser (Lite Touch) parameters for cavitated dentinal carious lesions treatment in permanent teeth The exposing of carious lesions with occlusal location (small pit and fissure carious lesions) starts with a sapphire tip tilted toward fissure at angle of 25 ° to the axial axis of the tooth.Once the ablation occurs, the tip is pointed toward the carious fissure perpendicularly (angle of 90 -100 ° to the occlusal surface).At wide fissure carious lesions the exposing is conducted with an angle of 90 -100 ° toward the fissure.The interproximal location requires the sapphire tip to be pointed at angle of 90 ° to the occlusal surface of the enamel that has to be removed.Er:YAG laser exposing of carious lesions with cervical location is getting conduct with a working angle of 110 -120 ° to the cervical enamel surface.
In mechanically prepared cavities, high-speed and low-speed water-cooled handpieces with burs were used.
The excavation in both groups was carried out un-der visual control with intermittent testing of hardness of the remaining hard structure by means of a dental probe [15] observing the principle of dental caries treatment with minimal intervention-removing of the infected layer leaving the affected one only on the pulpal wall of the cavity prepared.All cavities were restored with a nanohybrid composite (Calore GC) and adhesive system 3M ESPE Scotchbond Multi-purpose (SBMP) in accordance with manufacture recommendations.In the deepest carious lesions, calcium hydroxide liner was used prior to placing one of the filling materials.
The two cavities (one prepared conventionally, the other with an Er:YAG laser) were completed at two separate appointments, on different days.
No local anesthetic was used either before or during the treatment.Two step approach for assigning scores for each parameter was used: the first step was to assess the restoration and to determine the level of clinical acceptability for each parameter in each of the categories (the result becomes unacceptable whenever re-treatment is necessary or highly advisable with exception of secondary caries and marginal adaptation where even a minimally-invasive approach need requires score unacceptable); as a second step a further distinction was made between an excellent, good and clinically satisfactory result [17,18].

Parameters
Postoperative hypersensitivity was recorded at the time of restoration placement, at baseline and at all recalls visits, and included type of pain, discomfort and duration on dry ice stimulus at clinical assessment.Intensity was assessed with a Wong-Baker scale [19].Clinical evaluation of secondary caries and marginal adaptation was done with a loop (magnification 4 X), after tooth brushing with a paste.
Evaluation was done by two independent investiga-tors not involved in the treatment procedures using a mirror, explorer and air stream.The statistical analysis was performed using the Spcomparison.

RESULTS: Postoperative sensitivity
No postoperative sensitivity in all children at the 2year follow-up examination was observed.All treated carious lesions were evaluated as clinically ideal (code 1).

Secondary caries
No secondary caries was observed during the 2-year period of examination neither in the group treated with Er:YAG laser nor in conventional treatment group.

Marginal adaptation
The results of the marginal adaptation's assessment are presented on the table 3.
During the two-year study period 55 (94.83 %) of total 58 restorations in Er:YAG laser treated carious lesions and 56 (96.55 %) of conventionally treated lesions were clinically acceptable (code 1 + code 2).No statistically significant difference between the two groups was found (T=0.46;p>0.05).One of the restorations (1.72%) in Er:YAG laser treated carious lesions assessed as clinically unacceptable at 18-th month and 2 (3.45%) at 24-th month because of several small marginal fractures (code 3) were registered with no statistically significant differences between the groups.
No one of the restorations was lost in the 2-year period of evaluation.

DISCUSSION:
The recent study showed very good results with regard to the clinical success rate of Er:YAG laser dental caries treatment in permanent teeth in children after applying of the recommended by us protocol for using of the Er:YAG laser in dental clinical practice.These results can be explained with the adequate choice of Er:YAG laser parameters -laser energy, pulse repetition rate, energy fluence, working distance, working angle and air-water cooling, as well as the suitable clinical protocol applying.
In the process of Er:YAG laser assisted dental caries treatment "fine tuning" of the laser is one of the most important factors for a success treatment with no complications [20].No post operative sensitivity and secondary car-ies were observed in our study during the period of 2 years after applying of the protocol with recommended by us Er:YAG laser Lite Touch parameters.Postoperative hypersensitivity evaluated can be related to thermal pulp changes [21].It is well known that the temperature rise in the pulp chamber during cavity preparation with appropriate Er:YAG laser parameters is significantly lower than that with conventional mechanical methods [5].
The correct choice of laser parameters is a prerequisite for a safe and effective ablation of hard dental structures and enamel and dentin surfaces that provide a good adhesion of composite materials [9,22].Marginal morphology of restorations in Er:YAG laser Lite Touch treated carious lesions evaluated in the recent study showed excellent results compared to conventionally treated lesions.No one of restorations was lost and no one the evaluated clinical cases needed re-treatment.The only one of the restorations in Er:YAG laser treated carious lesions that showed several small marginal fractures at 18-th month and the two 2 of the restorations at 24-th month with the same defects were corrected by polishing of the edges and addition of composite material after acid etching and bonding.
Criterion "marginal morphology of restorations" is related to the adaptation of composite materials to the cavity edges and walls [23].In Er:YAG laser prepared cavities both the quality of ablated enamel and dentin surfaces and the type of adhesive system play crucial role in the marginal adaptation of restorations and are a prerequisite for a

Groups
Experimental Control   [20,24].It has been demonstrated in the literature that enamel and dentin surfaces prepared by laser should be followed by acid etching with 35-37% orthophosphoric acid [24].It allows regularization of ablated enamel prisms and less microleakage at the interface enamel composite as well as formation of hybrid layer and resin tag hybridisation into the opened dentinal tubules resulting in a better retention of the adhesive composites.Using of a working angle conformed to the orientation of the enamel prisms and dentinal tubules provides the opportunity of observing the rules for hard dental structure's treatment with minimal intervention [2,25].In the recent study, observing the rules for micro-invasive cavity preparation, carious dentin excavation in the area of DEJ and cavity walls expanded to sound dentin, in contrast to cavity bottom where dentin excavation was limited to vaporizing of the infected layer leaving the affected dentin on the pulp wall of the cavity prepared.Calcium hydroxide liners should be applied to stimulate a possible remineralisation of the affected dentin.
Er:YAG laser beveling of the enamel edges with parameters 100 mJ/20 Hz and working angle of 45° provides a regularization of the enamel prisms before acid etching and good adhesion of the restorative material and a microleakage-free interface [20,26].
Secondary caries appearance depends on many factors such as oral hygiene, caries activity, the potential of adhesion system to provide a good sealing between enamel margins and filling material [27].With regard to the Er:YAG laser application in dental caries treatment the potential of erbium-lasers for increasing of the enamel and dentin acid resistance has been demonstrated in the literature [28].The good results in our study are likely to be due to the described above effects.
It seems that the Er:YAG laser is a promising technology and it can be successfully used in dental caries treatment of permanent teeth.The manual ability of the operator to act on the structures with precision has been demonstrated to be of great importance [1,25].
In the near future this new technology could replace the conventional techniques used in pediatric cariology.

CONCLUSION:
The results of our study showed that the clinical success of the Er:YAG laser treatment did not differ from the conventional treatment.The protocol with Er:YAG laser Lite Touch parameters used can be recommended in the dental practice for caries treatment of permanent teeth in childhood.

Table 2 .
The evaluation of clinical effect of Er:YAG laser application in dental caries treatment of permanent teeth was conducted at baseline, 6, 12, 18 and 24 months using FDI Recommendations for Conducting Controlled Clinical Studies of Dental Restorative Materials, updated in 2008 (table2).The application of these criteria provides the opportunity of the clinical evaluation of restorations not only involving the restorative material per se but also different operative techniques[16].Evaluation criteria and clinical rates

Table 3 .
Clinical assessment of marginal adaptation good final restoration