Influence of Er, Cr: YSGG and Diode Lasers on The Surface Roughness of Enamel at Fissure area: An in vitro Study.

Aims : To assess and report the surface roughness incidence in fissure system of the dental enamel in human next Er, Cr: YSGG laser and Diode laser applications in order to examine anti-cariogenic impact and to compare the obtained results between the two laser types. Materials and Methods: Forty extracted impacted lower third molars teeth used in the experiment that should have an obvious occlusal fissure. Intact lower third molar were collected, which were free from caries .Teeth roots cut from crowns and crowns were divided bucco - lingually to two parts equally which were applied in 4 category included control group without any treatment, acid group only immersed in demineralizing solution, Diode laser group in which samples subjected to Diode laser (at wavelength 980nm, power 5 watt, mode P3, the time was 30 second) then immersed in demineralizing solution PH 4.4 for 96 hr., and Er, Cr: YSGG laser group in which samples subjected to Er, Cr: YSGG laser (wave length 2780nm, pulse energy20 Hz with pulse mode (H-mode), time 10 second) then immersed in demineralizing solution pH 4.4 for 96 hr. Results: both types of lasers resulted in a less surface roughness of enamel at fissure area as compared to the acid group, and Diode laser had better effect than Er, Cr: YSGG


INTRODUCTION
Dental caries is a multifactorial, food modulated, biofilm-mediated, noncommunicable, dynamic disease lead to clear mineral loss of dental hard tissues. (1)ries appears on the teeth just where plague is present, it is a demineralization activated by bacteria forming acids, and the amount of mineral loss is straight modified by both the activity and presence of the dental plaque. (2)Anatomical depth and morphological form for fissures and pits raise the incidence of dental caries.All experimental observation established that an increase in exposed of fissures and pits to caries occurrence than smooth surfaces since fissure anatomy and morphology helps dental biofilm growth and stagnation of food debris.
On the other hand it is more difficult to clean deep fissures and pits by the bristles of tooth brush and consequently increase retention of dental plaque and retention of diet fragment will be a very good shelter or habitat for dental caries bacteria. (3)eventative interventions against dental decay are powerfully suggested by the World Health Organization (WHO). (4)The use of sealant on enamel fissures and pits of molars is the most commonly application of traditional prophylactic interventions (TPIs) against dental decay (5) and high fluoride varnish or gel of topical management. (6)  Diode Laser Application: Teeth samples in group 3 were exposed to diode laser at wavelength 980nm and the power was 5 watts, (10)  Moreover, in this system the whole roughness is quantified by a metric average value which permits a statistical evaluation. (15).The test was done at the Technical institute/ University of Mosul.

Teeth
A partition of typical distance was gotten from the average line on the roughness diagram.In the Y direction, the distance between the uppermost peak (Rp) and lowermost valley (Rv) of the tested line was quantified which is (Ry).The quantity was calculated in micrometer (μm). ( 16

RESULTS
According to the obtained measurements of this study, Table (    Tagomori et al., (1995) (20) observed that the enamel surfaces irradiated reliably display surface roughness higher than untreated ones.
According to Sawan et al., (2015) (21)  to ejection of micro-fragments. (22)previous study done by Sun et   al., (2015). (23)found that specimen treated with the lesser variety of power (0-4 W) of Er,Cr:YSGG laser, presented with raised enamel surface roughness.In other study, Issar et al., (2016) (24) concluded that the irradiated of enamel surfaces with Er,Cr:YSGG laser showed elimination of smear layer and micro-irregularities.
No studies were found on enamel roughness after diode laser radiation although Ruchele et al., (2017) (25) in their study showed that diode laser impacts in enamel and the morphology of the enamel was alter and, so, its roughness but used the pigmented 5% sodium fluoride varnish which generating photo-thermal effect because this varnish operated as a photoabsorber for the diode laser photons,.Based on current study enamel surface roughness after Er,Cr:YSGG laser irradiation more than after diode laser radiation.

CONCLUSION
The Sample Collection and Criteria: Forty extracted impacted lower third molars teeth from individuals at age range between 20-25 years used in the experiment that should have an obvious occlusal fissure.Intact lower third molar were collected, which were free from caries, no enamel hypoplasia or developmental anomalies no cracks, wears or fractures.The Experimental Design of the Study: The total number of teeth sample in current study was (80) teeth samples.The samples were randomly distributed into 4 tested groups exposed to various type of treatment.Group 1: the included samples were not received any type of treatment, Group 2: the included samples were submerged in a demineralization solution, Group 3: the included samples were received Diode laser prior to immersion in the demineralization solution, finally Group 4: the samples were received Er,Cr:YSGG laser irradiation before immersion in the demineralization solution.Sample preparation: All soft tissues were removed by scaling and teeth were polished with super-fine fluoride free pumice using rubber cup.Teeth were stored in thymol solution (0.1%, pH 7.0) to avoid bacterial growth and were kept in a refrigerator at 4 °C till use. (9)Utilizing diamond low speed disc for cutting roots from crowns and then the crowns were divided bucco-lingually in to two equal parts which were applied in 4 tested groups.
and water in the tooth boils leading to highpressure steam, and the smooth tooth surface change by the explosive vaporization of water into usually flaky with irregularly serrated and micro-fissured structure, and one which is usually free from melting and carbonization.In the other study, morphological alterations like as enamel prisms cone-like shape and a raise surface roughness were also detected next laser apply.(18)Ganss et al., (2005)(19)  used a profilometric method to investigate the result of acid on the dental tissue.The amount of the roughness, height, and lowness of the surface of teeth was measured with a diamond probe.
stated the laser-ablated surfaces show the formation of craters, and have appropriate enamel roughness.The Er,Cr:YSGG laser cutting mechanism is called "thermos-mechanical process" in which emitted laser pulsedwave is directly absorbed by the water in the hydroxyapatite of enamel and dentine and produced the vaporization of the heated water and other hydrated organic components.Vaporization effects in increased internal pressure within the target tissues that in conclusion caused instantaneous micro-explosions that destroy the inorganic components before the melting point of tooth tissue and leads

Table ( 1
): Descriptive statistics of surface roughness measurements among tested groups.
Duncan's Multiple Range test shows that the mean surface roughness for Control group, Acid group, Er,Cr:YSGG laser group and Diode laser group are significantly different from each other at p ≤ 0.01.Acid group had mean surface roughness significantly higher (1.1200) than other groups, Er,Cr:YSGG laser group had mean roughness of enamel surface (0.8650), Diode laser group had mean surface roughness (0.6815) while control group had lesser mean on surface roughness (0.5090) as shown in figure (1).The analysis of variance of t-test used for Er,Cr:YSGG laser group and diode laser group.Er,Cr:YSGG group show more enamel surface roughness in fissures than diode laser group at (p ≤ 0.01) as shown in table (3).So, Diode laser application resulted in better improvement in surface roughness than Er,Cr:YSGG laser.Figure (1): Duncan's Multiple Range test of surface roughness measurements for control group, acid group, diode laser group and Er,Cr:YSGG laser group.

Table ( 3
): The t-test analysis for determining the significant difference in surface roughness between Er,Cr :YSGG laser group and diode laser group.