| compared with normal vital pulp teeth,Root canal treated teeth has significantly different physical and mechanical properties, the elastic modulus, tensile strength and shear strength are lower than the live pulp teeth. Therefore, root canal treated teeth with vital pulp teeth more easily occurred fracture. Once the occurrence of root fracture, the result is often destructive.Many scholars have emphasized the protection of the tooth after root canal treatment.Objective:For different defect area of molar root system canal treated by direct composite resin filling and resin onlay indirect restorations, by in vitro damage experiment, the determination of root canal treated teeth in 4 types of repair after tearing force value and tooth fracture mode. Effect evaluation of different repair methods for different defect area of endodontically treated tooth fracture resistance, provide some experimental basis for clinical.Methods:select 42 healthy premolars from the Affiliated Stomatological Hospital of Zhejiang University oral surgery for orthodontic treatment,6 isolated teeth were randomly selected as control group, without root canal treatment. The remaining 36 isolated teethuse conventional root canal therapy, then randomly divided into 3 groups,Group A.Only open medullary cavity, no other obvious tooth defect.Group B:There are 1 tooth CEJ coronal remnants of healthy tooth tissue is less than 2mm, MO or OD hole, tooth cheek tongue in cheek tongue size control triangular ridge 1/2.Group C:There are 2 tooth CEJ coronal remnants of healthy tooth tissue is less than 2mm, MOD hole, tooth cheek tongue in cheek tongue size control triangular ridge 1/2.The 24 teeth in each group have respectively in different ways for root canal treatment to repair teeth:Direct composite resin restorations, inlay.Using self curing plastic embedding, the samples are placed on the electronic universal testing machine, the loading direction and teeth body axis at an angle of 135 degrees, the power load in occlusal middle buccal lingual triangular ridge interchange, with the speed of 1mm/min continuous afterburner, until the teeth break, break records crack when loading force values, and to observe the form of tooth fracture.Resultâ‘ The anti fracture ability of resin inlay indirect bonding repair group was higher than that of resin direct bonding repair group.â‘¡Resin block body indirect bonding repair tooth crack model, there was no significant difference (P> 0.05); resin bonding restoration of tooth fracture crack pattern no statistical difference (P> 0.05); inlay body indirect bonding repair group tooth fracture mode and resin bonding restoration groups there was significant difference (P< 0.05).ConclusionIn vitro tests have proved that the defect of the tooth body can decrease the strength of the tooth, especially the integrity of the marginal ridge has a great influence on the strength of the tooth. This experiment adopted from precursor molar as the research object, in the same tooth defect degree of different repair methods and different tooth defect degree under the same way to repair of tooth flexural capacity of a comprehensive comparison is made.The maximum bite force of the first molar was 241.1-284.2N. During chewing, such as the masticatory muscle contraction force exceeds the tolerance threshold of periodontal, due to the pain reflex inhibition provided jaw muscles to reduce the contractile force, so everyday chewing food required bite force of about half of the teeth together. The resin of direct restorations and indirect bonding resin inlay restoration for tooth fracture resistance can meet the normal masticatory function.The root canal treated with resin bonded directly to the root canal can be treated as a restorative tooth and can be repaired for two times. And nickel resin block body indirect bonding in most cases will result in the repair of tooth fracture, even vertical root fracture, fracture do not secondary repair. |
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