The Study Of Er: YAG Laser In The Treatment Of Pit And Fissure Caries Restored By Constic Flowable Resins

Objective: Pit and fissure caries is deep and narrow. In order to clean clearly the tiny broken tissue of caries, traditional handpiece methods cannot avoid the abrasion of healthy tissue. In comparison, Er: YAG leaser plays an important role in minimally invasive therapy because of its apparent advantages. As the laser point is narrow and it works precisely, safely and fast to pinpoint position, which protects healthy dental tissues effectively. Moreover, changing from preparation mode to etching mode can be easily achieved through adjusting the parameter.The experiment involved in this study compares the different preparations with traditional handpiece method and Er: YAG laser, and analyses the microleakage and gaps between fillings and teeth after filled by Constic. The purpose is to assess whether the Er: YAG laser irradiation can improve the effect of clinical application with the treatment with Constic in vitro study.Methods:Experiment: The 120 in total extracted healthy premolars and molars were collected from The Department of Oral & Maxillofacial Surgery, Dental Hospital of Hebei Medical University, cleaned and preserved in the normal saline at 4?. The teeth were randomly divided into six groups A.B.C.D.E.F, with 20 teeth per group. All were filled by Constic. Group A: Constic flowable resin filled after prepared by conventional mechanical; Group B: Constic flowable resin filled after prepared by Er: YAG laser; Group C: Constic flowable resin filled after prepared by Er: YAG laser and etched by Er: YAG laser; Group D: prepared by Er: YAG laser, then etched by Er: YAG laser and used by Prime&Bond NT Adhensive System; Group E: Constic flowable resin filled after prepared by Er: YAG laser, then acid etched by phosphoric acid and used by Prime&Bond NT Adhensive System; Group F: Constic flowable resin filled after being prepared by Er: YAG laser and used by Prime&Bond NT Adhensive System.1 Group A: Use high speed silicon carbide burs and slow speed half ball type drill to fissure, the cavity along the teeth to the depth about 1.5 to 2mm. The rest of the teeth were used by Er: YAG laser. According to the method above, all are filled by Constic.2 All filled teeth were immersed in artificial saliva at constant temperature of 37? for 30 day.3 Put the tooth into cold water(0-5?) for 30 seconds then warm water(55-60?) for 30 seconds alternately for a cycle, and repeat this cycle for 500 times.4 Select 10 teeth from each group randomly for microleakage test and measure the gaps between fillings and teeth tissue at the edge 0.2mm from cavity margin by SEM of the teeth remained.5 Analyze the data statistically according to the graded microleakage on each tooth and the gaps by SEM.Results: 1 Gaps between constic resin and tooth tissue observation: the result of group A(approximate 12.55±2.15 ?m) was obviously less than the previrous experimental result(approximate 37.00±10.52 ?m)[1]; 2 The grades of 6 groups gained from stereomicroscope are significantly different by Wilcoxon Mann-Whitney test. Group A was the highest, which showed statistical difference to other groups(P<0.05). Group C, D, E were better than Group B and F, which has statistical difference(P<0.05). There was no statistic difference among group C, D, and E, and same to group B and F(P>0.05); 3 Through SEM observation, the gap of A group was bigger than other groups, had statistic difference(P<0.05). The gap of Group C, D, and E after etching and the gap of group B and F without etching show statistic difference(P<0.05). There was no statistic difference among group C, D and E, so it was to group B and F(P>0.05).Conclusions:1 Observed from the stereomicroscope, the groups prepared by Er: YAG laser were less microleakage than those highest ones prepared by traditional handpiece. The etched groups were the lowest ones.2 Through SEM observation, the gap between fillings and teeth in the handpiece preparation group was the largest, followed by those treated with direct resin filling and those with binder after cavity preparation with Er: YAG laser, and the smallest ones treated with etching.3 Er: YAG can do cavity preparation and etching safely and efficiently, not only can the method avoid etching stimulation, but also it can obtain ideal clinical effect, excellent interfacial cohesion and reduce the microleakge.