Study on the hottest medical orthodontic adhesive

2022-09-23
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Research on medical orthodontic adhesives

preface

I. research background

since Newman first used epoxy resin bonding technology for bonding orthodontic accessories in 1965 [1], it has been rapidly popularized and widely introduced into orthodontic fixed orthodontic treatment technology because of its convenience and efficiency. Orthodontic adhesives have also developed rapidly. At present, orthodontic adhesives with various components and curing methods are available for clinicians to choose. However, in the process of fixed orthodontic treatment, due to the long correction cycle and the influence of brackets, steel wires, ligation wires and other orthodontic accessories, it is difficult to clean the teeth, especially the tooth surface around the brackets. Therefore, in patients receiving orthodontic treatment, there is a common manifestation of enamel demineralization caused by poor oral hygiene - Enamel leukoplakia. In severe cases, it can also develop into early production procedures. At present, enamel caries is intermittent. Therefore, how to prevent enamel demineralization during orthodontic treatment has always been one of the hot issues that contemporary orthodontic clinicians pay great attention to and are working on. With the development of research on caries prevention of fluoride, its caries prevention mechanism is basically clarified, and the effect of caries prevention has also been recognized. Therefore, in the past two decades, foreign orthodontists have tried various methods to apply fluoride ions to orthodontic correction, such as the use of fluorinated foam, local application of fluoride, the application of fluoride protective paint and so on, in order to prevent enamel demineralization. Although these methods have been proved to reduce enamel demineralization in the process of orthodontic treatment to varying degrees, there are also adverse factors such as increasing chair side operation time and poor patient compliance, so they have not been widely promoted and applied. Since the area with serious enamel demineralization is mainly around the bonded bracket, it is closely related to the bonding scope and technology. It is undoubtedly a simple and effective method to add fluoride that can slow release fluoride ions for a long time to the adhesive to prevent enamel demineralization around the bracket bonding area. In 1983, Rawls and Zimmerman successfully developed a dental restoration composite resin with relatively stable fluoride ion slow-release performance for the first time [2], and proved that it can prevent enamel demineralization around the restoration [3]. Subsequently, sansing, Rawls, Shaye and others [4] compared the bonding strength of this composite resin with that of general orthodontic adhesives, and the results were not significantly different. Since then, the development of fluoride releasing adhesive (FRA) has become a common concern of Orthodontists and dental material manufacturers. In 1989, Underwood, Rawls and others [5] published a paper for the first time to evaluate the actual effect of FRA in reducing enamel demineralization in orthodontic clinical application. The results showed that FRA can effectively reduce enamel demineralization around brackets. So far, several FRAs with registered trademarks have been developed abroad, such as vp862, Rely-A-Bond, sequence, light bond, fluoever oba, etc., and they have been tried in orthodontic clinic. At present, the research on fra abroad is still mainly focused on the bonding strength of FRA, the performance of FRA in releasing fluoride ions and the effect of preventing enamel demineralization. With the deepening of these studies and clinical trials, it is believed that FRA has high bonding strength, moderate and stable fluoride ion release, which can prevent and reduce enamel demineralization to a certain extent. Moreover, because FRA is easy to use, does not need to occupy additional operation time beside the chair, and does not need the cooperation of patients, it is becoming more and more popular as an effective anti caries orthodontic adhesive by orthodontists and patients

in recent 20 years, fixed appliance technology has become the mainstream technology of orthodontic treatment in China. Although domestic ordinary orthodontic bonding materials with stable performance have been used in orthodontic clinic in China, there are no reports on the research and development of FRA, and the imported materials are expensive, which is difficult for Chinese patients to bear. Therefore, after nearly three years of cooperative research with the school of chemistry of Sichuan University, on the basis of systematically consulting domestic and foreign literature, we have carried out hundreds of polymer synthesis and inspection experiments in the past two years, and finally jointly developed a FRA, tentatively named fluo hx. At present, we have preliminarily explored the laboratory synthesis path of organic fluorine source components with independent intellectual property rights in fluo HX, preliminarily completed the screening of fluo HX formula and established a set of simple and effective test methods, which has laid a solid foundation for further in-depth research and marketization of this project in the future

II. Composition and formula of fluo HX at this stage

fluo HX adhesive is composed of etching agent, enamel coating agent and fluorine slow-release adhesive. The etchant is prepared with 37% phosphoric acid; Enamel coating agent is adhesively coupled by modified methacrylate and 4-methacryloyloxyethyl trimethyl benzoate (4-META). This cyclic turning zigzag rod is actually a fundamental warming or a short-term repair of steel. It is still to be verified by the market. Active diluents and initiators are prepared into liquid agents of components a and B; The fluorine slow-release adhesive is composed of PMMA resin, MMA resin, 4-methacryloyloxyethyl trimellitic acid (4-META) adhesive coupling agent, silylated silica, polymer ion association fluorine-containing complex (organic fluorine source), active diluent, accelerator and initiator to form a and B powder liquid dosage forms

III. future research direction

1. Dosage form: the information returned from clinical feedback shows that the non harmonic single paste orthodontic adhesive with convenient operation and strong adhesion will become the first choice of orthodontists. Therefore, the fluo HX we developed must also comply with this trend, and change the dosage form to non harmonic single paste type, which will be the focus of our next work

2. Fluorine source: we will further extend the investigation on the time of fluorine ion release from fluo HX, and further improve the organic fluorine source on the existing basis

3. Physical and chemical properties and biological adaptability: when all aspects of work have been basically completed, we will test the physical and chemical properties and biological adaptability of fluo HX according to the requirements of the national industry standard YY of dental enamel bonding resin. After reaching the standard, we will conduct clinical in vivo experiments on the bonding performance and enamel demineralization prevention performance of fluo HX

4. Product development: after all the performances are qualified, we will apply for a patent for the key component of fluo HX - organic fluorine source, and look for cooperative enterprises to officially introduce fluo HX to the market in the form of technology shares

references

abe TM, vanardall rl Orthodontics-Current Principles and uis: Mosby, 1994

wls HR, Zimmerman BF. Fluoride-exchanging resins for caries protection. Caries Res, 1983,17:

nton JB, Zimmerman BF, Rawls HR, Turpin-Mair JS. Enamel fluoride uptake from an experimental anion exchanging resin [Abstract 919]. J Dent Res, 1983,62:271

nsing WJ, Rawls HR, Shaye R. evaluation of a caries-protective resin for orthodontic direct bonding [unpublished]. New Orleans: Louisiana State University School of Dentistry, 1983

derwood ML, Rawls HR. Clinical evaluation of fluoride-exchanging resin as an Orthodontic adhesive. Am j Orthod dentofac Orthop, 1989,96:93

Part I comparative study on the bonding properties of fluo HX and general orthodontic adhesives

preface

as an orthodontic adhesive, the most basic requirement of resin type fluoride ion slow-release orthodontic adhesive is that the bonding strength should meet the clinical needs. The research on bonding performance mainly focuses on testing the tensile bond strength (TBS) and shear bond strength (SBS) of materials. In this study, the resin type fluoride ion slow-release orthodontic adhesive fluo HX developed by us and the two orthodontic adhesives commonly used in clinic in our department were used. Under the in vitro experimental conditions simulating clinical application, the bonding tensile strength and bonding shear strength of the three adhesives between bovine enamel and metal brackets were compared to understand: ① whether there is significant difference in bonding strength between fluo HX and orthodontic adhesives commonly used in clinic, Whether the bonding strength can meet the clinical needs; ② With the slow release of fluorine ions in fluo HX, will the bonding strength of fluo HX be affected

I. materials and methods

1.1 materials

1.1.1 the three orthodontic adhesives used in the experiment are shown in Table 1

Table 1 three orthodontic adhesives used in the experiment

adhesive curing methods development unit fluo HX, School of Stomatology, Sichuan University, School of chemistry, chemical curing TF, Beijing Tianjin and Tianjin Institute of synthetic materials, chemical curing 1.1.2 isolated bovine teeth select caries free isolated bovine upper and central incisors, and polish the lip surface with sandpaper to prepare a smooth enamel bonding surface, After cleaning and drying with distilled water, etch the tooth surface with 37% phosphoric acid for 1min, and then clean and dry with distilled water for standby

1.1.3 clean and dry standard edgewise arch upper central incisor brackets (Hangzhou Xinya company) are selected. The friction coefficient of plastic film on the bottom of the brackets is a main target groove retention type. Bolt the stainless steel wire in advance for stress test

1.1.4 main experimental instrument lj500 tensile testing machine (produced by Wuzhong micro testing machine factory)

1.2 method

1.2.1 the experiment was divided into groups. 50 specimens were randomly bonded with each adhesive. After bonding, they were divided into 5 groups, with 10 specimens in each group. They were placed in 37 ℃, 100% RH environment for 5min, 37 ℃ water for 1h, 24h, January and March. TBS and SBS were taken out and tested for 5 specimens each

1.2.2 the test of bonding tensile strength is carried out in the environment of temperature 22 ± 2 ℃, relative humidity 55 ± 5% RH. The bonding is completed according to the instructions of each adhesive, and the groups are divided according to the experimental conditions. Finally, under normal temperature environmental conditions [1], use lj500 tensile testing machine to continuously apply tensile force to the bonding specimen at a tensile speed of 10mm/min, and record the maximum tensile force when the specimen is damaged. Calculate the bonding tensile strength according to the bottom area of the bracket and the breaking force, in MPa

1.2.3 the material selection, bonding, grouping and environmental conditions for the test of bonding shear strength are the same as those in 1.2.2. During the test, the shear force is continuously applied to the bonded specimen at the tensile speed of 10mm/min. Calculate the adhesive shear strength according to the bottom area of the bracket and the destructive shear force, in MPa

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