The Clinical Research Of Micro-invasive Therapy On The Treatment Of Enamel Surface After Demineralization

Background:Enamel demineralization is a common complication and the major risk factor of teeth in orthodontic treatment, which was reported to occur in approximately73%-95%of patients undergoing treatment. White spot lesions the early signs of enamel caries appear on the enamel adjacent to the brackets only one month after the brackets fixed. With the development of enamel demineralization, more enamel crystal dissolve creating pores between the enamel rods. The resultant alteration of the refractive index in the affected area is then a consequence of both surface roughness and loss of surface shine and alterations in internal reflection, all resulting in greater visual enamel opacity, as porous enamel scatters more light than sound enamel. In severe cases, the lesions can not be remineralized, so the restorative treatment may be required. Because of the high prevalence and the aesthetically unacceptable result, many studies about the enamel demineralization have been done.Enamel demineralization develops as a result of the irregular surface of brackets, limit self-cleaning mechanism, such as the movement of the oral musculature and saliva. This change in the local environment appears to favor colonization of aciduric bacteria such as Streptococcus mutans and lactobacilli encouraging a lower plaque pH in the presence of carbohydrates and accelerates the rate of plaque accumulation and plaque maturation. All of these break the enamel surface demineralization and remineralization balance. Patient’s conditions, fixed orthodontic appliances, tooth position and many other factors may affect this process. Many clinical procedures are used for the prevention of enamel demineralization, such as fluoride administration (fluoridated toothpaste, mouthrinse, gel and varnish),Casein phosphopeptide-amorphous calcium phosphate administration, Argon-laser enamel surface attenuation, well design of the brackets,oral hygiene instruction and so on. But all these procedures have application limitations, clinical effects are limited, for example, fluoride is usually limited to the small area of enamel surface and the concentration is difficult to remain stable for a long time. It is not convenient for the patients to rub the enamel surface with fluoride. With the development of oral materials, minimally invasive, painless methods are expected to solve the problem of enamel demineralization. Having done a large number of in vitro experiments, professor Paris have found that a treatment with15%HCL acid for90s can effectively remove the surface smear layer of the enamel demineralization area. This may have positive influence on the penetration of the resin infiltration with high mobility. This is the so called micro-invasive treatment. Based on the concept a new resin infiltration with low viscosity, good wetting permeability has been created. This resin can penetrate into the deep area of the demineralization layer and form a resin-hydroxyapatite complex barrier. This barrier can prevent the development of enamel demineralization. Because of the similar refractive index as normal enamel surface, the resin can highly improve the anesthetic appearance of the tooth with white spot lesions.As the new resin infiltration has not been widely used in clinical and the lack of clinical evidence for the treatment of white spot lesions, independent researchers should provide scientific analysis to confirm its efficacy, all these can make a reference to its clinical application. In this study, we choose the patients with white spot lesions after removal of brackets and isolated teeth for the experimental subjects, by the use of scanning electron microscope and Olympus Crystaleye colorimeter, we analyzed the resin penetration capacity and the color, shape, quality changes of the enamel demineralization surface.The part I:Study on the repeatability and accuracy of a new dental spectrophotometer shade-matching device Olympus CrystaleyeObjectiveTo evaluate the repeatability and accuracy of the spectrophotometer shade-matching device Olympus Crystaleye.MethodA1,1M1shade guide, one isolated left central incisor were fixed in the blinded-box, and One volunteer left central incisor was chosen for this trial also. The Olympus Crystaleye Spectrophotometer colorimeter was used to measure them for twenty times. The color parameters (CIE1976L*a*b*) of incisal、body and cervical of each sample were recorded. The next day, the same test was repeated, and the results of the same object was compared with the average L*a*b*value before, each△E was calculated. Then the120different areas color records of A1,1M1shade guide were tested forty times and compared to the standard value. The matching rates of correct shade were calculated, and the two rats were compared with chi-square test. ResultIn the four groups, the△Eranged between0.02-1.47, all<1.7. The matching rate of correct shade in A1was95.85%, whereas97.5%was obtained in1M1. There was no significant difference between two groups.The part II:the effect of penetration resin on the color, shape, quality changes of isolated teeth enamel surface after demineralizationObjectiveObserve the penetration resin on the color, shape, quality changes of isolated teeth enamel surface after demineralization, and provide a theoretical basis for its clinical application.Method1. A total of40premolars in maxillary extracted for orthodontic reasons were collected in Guangdong Provincial Stomatology Hospital, The samples were randomly divided into two groups(A,B) with20teeth in each group.2. Olympus Crystaleye spectrophotometer Colorimeter was used to measure the L*a*b*value of each tooth’s buccal body for20times, then the average L*a*b*values of each tooth were calculated.3Buccal surface of each tooth was etched by32%phosphoric acid gel for60seconds, then Olympus Crystaleye spectrophotometer Colorimeter was used to get the average L*a*b*values of each tooth in A and B groups. The penetration of resin was used on the each tooth’s buccal surface of group A. Artificial saliva was used on the each tooth’s buccal surface of group B. Dry the buccal surface of each tooth, then the average L*a*b*values of each tooth’s bucall body surface were measured by Olympus Crystaleye spectrophotometer Colorimeter. The scanning electron microscope was used to get the surface and longitudinal morphology of the tooth.Result1Compared to the tooth etched before the△E values of A and B group were14.61±7.50and15.61±3.86, no significant difference between the two groups.2The△E value of A group after using penetration resin was14.67±6.38. In group B after the treatment with artificial saliva, the△E value was0.24±0.29. There were significant differences between the two groups.The part Ⅲ:The effects of penetration resin on the treatment of enamel after demineralization.Objective:To evaluate the clinical effects of penetration resin on the treatment of enamel after demineralization.Methods:The penetration resin was used on forty front teeth which had white spot lesions after fixed orthodontic therapy. The Olympus Crystaleye Spectrophotometer colorimeter was used to measure the colors of the teeth for twenty times before and after using the penetration resin. The color parameters (CIE1976L*a*b*) of each tooth were recorded. The measurement data of L*a*b*before and after using penetration resin were analyzed by paired t test, then each△E was calculated.Result:The values of L*a*declined, b*value improved after using the penetration resin (P<0.01, paired t test), and the values of△E ranged from (4.67-18.6),all>1.7.Conclusion The Olympus Crystaleye Spectrophotometer colorimeter with high repeatability and accuracy can provide accurate data for the part Ⅱ and part Ⅲ experiments. Penetration resin can form a barrier on the surface of enamel after demineralization and the anesthetic appearance can be improved.