| 1. BackgroundWith the development of the various branches of the oral and human health conscious, a lot of residual root and crown are preserved. The significance of this method is:in the chewing function, people can support and adjust the bite force with the periodontal membrane and sensory system. To maintain the stability of the dentition, to keep the height of the alveolar and to slow down its absorption. The root canal treatment of residual root and crown save the root, but dose not protect them. It is believed that it is the loss of tooth structure due to caries, trauma or endodontic therapy that makes endodontically treated teeth more susceptible to fracture. So, crown restoration of an endodontically treated tooth often requires additional support from the root canal by means of a root canal preparation and the fabrication of a post and core restoration.Post can be divided into the metal post and non-metallic post, according to the material. Several disadvantages are associated with conventional cast post-and-cores, such as loss of post retention, root fractures, and risk of corrosion. Stress concentration in the post and higher dentin strain have been verified in teeth restored with cast post-and-core, and other metallic post, increasing the risk of tooth fracture. The conductivity of metal material can lead to RF field deformation, and disturb diagnosis of the magnetic resonance. The disadvantages of the metal post limits its clinical application.FRC posts contain60%continuous reinforcing fibers embedded in a polymer matrix, which keeps the fibers together. Matrix polymers are commonly epoxy polymers with high a degree of conversion and a highly cross-linked structure. The modulus of elasticity of the fiber post(15-18Gpa) is similar to that of the dentin. Wu bulin consider that the stress distribution of restorations is closely related to the modulus of elasticity of the fiber post. If the modulus of elasticity of the fiber post is similar to that of the dentin, it can reduce the incidence of root fracture. In the in vitro studies, fiber posts showed higher fatigue resistance than that of stainless post and titanium post.There are carbon/graphite fiber post, glass fiber post and silica fiber post, according to continuous reinforcing fibers embedded in a polymer matrix. The carbon fiber post contains polymer matrix and carbon fiber, which has good mechanical properties, such as low elastic, high fatigue resistance and good biocompatibility. However, they are black in color and thus lack cosmetic qualities and not suitable for all-ceramic crowns. Therefore researchers use glass fiber instead of the carbon fiber. The fiber post retains the good mechanical properties of the carbon fiber post, and improves its color. The glass fibers have a lower elastic modulus than carbon fibers. Glass fiber posts can be made of different types of glasses. Electrical glass (E-glass) is the most commonly used glass type in which the amorphous phase is a mixture of SiO2, CaO, B2O3, Al2O3and some other oxides of alkali metals. The later quartz fiber post is pure silica in crystallized form. It is an inert material with a low coefficient of thermal expansion and have better rigidity than other glass fibers. The quartz fiber post has a good light conductivity. Light get through the quartz fiber post, leading the bonging agent curing. Domestic and foreign studies compare the fracture resistance and fracture patterns of endodontically treated teeth restored with a carbon fiber post, quartz fiber post and cast post, and find the fracture resistance of quartz fiber post is higher than that of carbon fiber post and cast post. Meanwhile, they also confirmed that the fracture patterns of quartz fiber post is a favoring retreatment of fractured specimens.The introduction of carbon or glass fiber post systems provided an alternative to cast or prefabricated metallic posts for the restoration of endodontically treated teeth. These post systems present similar mechanical properties to those of dentin, resulting in similar stress patterns as those of intact teeth.The main role of the post is to provide retention for the core and restoration, not improve the fracture resistance of tooth. During the preparation of teeth to receive post-and-core restoration, larger amount of root dentin is removed, increasing the risk of tooth fracture. It is very important of post and core restoration to improve its retention and fracture resistance. This is still a huge challenge for clinicians to get a good long-term repair effect. Some studies have confirmed that preserving intact coronal and radicular tooth structure and maintaining cervical tissue to create a ferrule effect are considered to be crucial to optimize the biomechanical behavior of the restored tooth. Reasonable design of the ferrule can reduce the incidence of toot fracture. A ferrule effect is defined as, the parallel walls of the dentin extending coronal to the shoulder of the preparation. The ferrule effect has been suggested as a possible method to improve fracture resistance and decrease the incidence of dowel decementation. The results of the finite element analysis and the mechanical test showed that an increased amount of coronal dentin significantly increases the fracture resistance of endodontically treated teeth.2. Objective To determine, whether ferrule significantly affect the survival of pupless teeth restores with the Macro-Lock quartz fiber posts.3. Materials and methods3.1MaterialsMacro-Lock quartz fiber posts include, Sealbond Etching, Sealbond Ultima, CoreCem post and core integration resin cements,3M Elipar Freelight curing light, Absorbent paper points, Gingival retraction cord, Ceivitron, AH Plus, Vita shade, Gutta percha, Glass ionomer cement binder, Alginate impression material3.2Study SubjectsA total of70subjects were included in the trials,32men and38women with an average of42years, who visited department of stomatology in Zhujiang Hospotal between February2011and March2013and needed restoration of endodontically treated teeth. The teeth were restored using the Macro-Lock fiber post:27incisors,8canines,21premolars and14molars. Before the trials, doctors should fully informed patients with various treatment options, according to the medical institution regulations.The selected teeth needed to be in occlusal function with a natural tooth, and in interproximal contact with at least one adjacent natural tooth. Teeth were not used as abutments for fixed or removable partial dentures. If the teeth had already been endodontically treated, the inclusion criteria (symptom-free root canal filling and a minimum apical seal of4mm, without any periapical lesion on the radiograph had to be met. Patients denied dry mouth syndrome, diabetes, allergy, infectious. Patients can master the correct way of brushing your teeth and be willing to accept periodic assessment.3.3Method Two experimental groups were defined as follows, based on the amount of dentin left at the coronal level up to the shoulder of the preparation, before the abutment was built-up:Group A, ferrule present (a dentin collar of at least2rom height and minimal1mm thickness, as measured with a periodontal probe, was preserved circumferentially),42teeth (60%); Group B, ferrule absent(less than2rom of dentin was present circumferentially),28teeth (40%). The following data were collected at every6months since a week after treatment.The walls of the root canals were enlarged with low-speed burs provided by the manufacturer. According to the occlusion to cut out the fiber post. Sealbond Ultima was the bonding agent and CoreCem was the cement. Core build-up was then performed using CoreCem cement. Then, the abutment was prepared with diamonds burs and a chamfer finish. It was covered with a metal-ceramic or all-ceramic crown.3.4Statistical methodStatistical analysis was performed with SPSS13.0software. The level of significance was set at P<0.05, a=0.05.Additionally, Pearson’s chi-square test was applied to compare frequencies of failure with two groups and to investigate the structure of sex and tooth type. The Kaplan-Meier plots were constructed.4. ResultsData were not affected by any loss to follow-up. Of the70teeth,66survived, and4failed. The overall survival rate of crowned endodontically treated teeth was94.29%. Group A did not have any fail cases. In group B, of a total of28treated teeth,4failed, the success rate was85.71%. Chi-square test showed statistically significant differences between two groups.5. Conclusions 1.When used the Macro-Lock quartz fiber posts in group B(less than2.0mm of dentin was present and mimimal1.0mm thinkness), we can get a good short-term effect.2. The Macro-Lock quartz fiber posts have high mechanical strength and bond strength, good biocompatibility and aesthetic effect. The Macro-Lock quartz fiber post is a translucent fiber post. Light can get through the quartz fiber post, leading the bonging agent curing. If the restoration failed, the fiber post can easily removed. |
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