Source: China Medical Forum today oral Speaker: Chen Zhi
Composite resin direct repair is the most commonly used technique in clinical work. Composite resin direct repair technology is divided into the following five steps: moisture separation, cavity preparation, acid etching and bonding, filling, shaping and polishing.
These five steps seem to be simple, but there are strict requirements for the standardized operation of dentists. If there is any omission in the previous steps, it will have a great impact on the success rate of high-quality repair in the later stage. Therefore, we should take "standardized operation" as the premise of the whole operation process in our daily clinical work, advocate and carry forward the spirit of craftsman, and strive to make every step the best.
Moisture isolation
Advantages of rubber barrier
After routine examination, treatment plan and doctor-patient communication, the clinical operation of direct repair can be started. Moisture isolation is the first step of the whole operation. The use of rubber barrier can effectively help us isolate the operation area and improve the visual field, reduce the frequency of mouthwash, improve the work efficiency of doctors, protect patients from inhaling or swallowing foreign matters, protect doctors themselves, avoid cross infection, and prevent the influence of saliva and moist gas on bonding.
The apparatus for using the rubber barrier includes the rubber cloth, the punch, the bracket, the rubber barrier clip, the rubber barrier clip opening pliers, as well as the floss and the fixed rubber strip (as shown in Figure 1).
Figure 1 equipment required for rubber barrier
Use steps of rubber barrier
Fig. 2 areas to be isolated for restoration of premolars and molars
Cavity preparation
Selection of hole type
Different from amalgam filling, composite resin direct restoration does not rely on the mechanical retention of the cavity, but on the bonding of dentin adhesive with enamel and dentin. Therefore, the principles of cavity preparation, cavity design, instruments and caries removal methods of composite resin restoration are different from those of traditional amalgam filling technology.
The principle of cavity preparation of composite resin repair technology is minimally invasive, to retain healthy tooth tissue as much as possible, and to protect pulp tissue. Hole preparation no longer pursues the traditional hole type standard advocated by G.V. black. In the hole design, the improved hole design is adopted to maintain the original hole as much as possible, without preventive expansion and mechanical retention. For the adjacent cavities, it is not necessary to expand to the occlusal surface to prepare the standard class II cavities, and the cavity shape is generally prepared as "C" shape.
For an affected tooth, the proximal and distal interproximal cavities should be prepared separately, without the need to prepare the proximal and distal interproximal cavities. For the proximal and distal caries of two adjacent teeth, the cavity with larger caries (involving the marginal ridge) can be prepared as the adjacent occlusal cavity first, and then the cavity with smaller caries (not involving the marginal ridge) can be prepared as the single-sided cavity; when filling, first fill the single-sided cavity, and then fill the other adjacent occlusal cavity (see Figure 3 for specific cases).
Fig. 3 Schematic diagram of caries in the distal and proximal adjacent surfaces of the first and second molars
Selection of spare hole needle
The mini invasive trocar needle (as shown in Fig. 4) is selected for cavity preparation. It has two advantages: first, its cutting head is small, which can maximize the protection of tooth tissue; second, its shaft handle is thin, and the field of vision during operation is clearer.
Figure 4 Schematic diagram of minimally invasive needle
According to the international consensus of caries experts (see Chinese Journal of Stomatology, No. 12, 2016), the principle of selective caries removal should be followed: in the cavity edge and side wall, the caries tissue must be removed, while in the pulp wall and axial wall (close to the pulp tissue), after all the softened dentin needs to be removed, the toughened dentin can be retained as appropriate, and even the leather dentin can be retained in deep caries to avoid accidental pulp leakage. The recommended standard to judge dentin caries is exploration. The use of color or staining as caries removal standard will lead to over preparation (see Figure 5 for the schematic diagram of caries removal standard).
Figure 5 Schematic diagram of decaying standard
There is no consensus among experts on the method of caries removal. It has been found that the effect of chemical mechanical caries removal is the best between the effectiveness of caries removal and minimally invasive. The laser-assisted mechanical caries removal (such as face, LIF) and chemical staining assisted mechanical caries removal have problems such as excessive cutting or insufficient preparation.
Etching and bonding
With the rapid development of modern dental bonding technology, it is relatively mature. The result of the system is good, but there are many operation steps and high technical sensitivity. The operation steps of self etching bonding system are few and simple. Because of the difference of structure and chemical composition between enamel and dentin, the enamel has high mineralization degree and is relatively hard. If only self acid adhesive is used, the etching depth of enamel is not enough, and the bonding strength is not as strong as that of acid etching washing system.
Based on the evidence-based medicine, it is suggested to use selective etching technology, that is, the combination of etching agent and self acid adhesive. In the operation, first use phosphoric acid to selectively etch the enamel on the edge of the cavity for 15s, wash and dry it, then use self acid adhesive to coat the enamel and dentin for 20s, gently blow for 5S to make the solvent volatilize, and finally finish the bonding by lighting for 10s.
filling
Classification of composite resin filling technology
The resin material used in this technology is paste mixed filler resin. The resin is the most widely used repair material in clinic. Due to the inherent characteristics of composite resin, polymerization shrinkage occurs during polymerization. Layered oblique filling technology can reduce polymerization shrinkage. This technology requires that the first layer should be filled horizontally with a thickness of only 1mm, and then each layer should be filled obliquely with a thickness of no more than 2mm. This technique is suitable for the repair of the adjacent wall of class I and class II holes.
Injection filling technology the material used in this technology is the second generation flow resin which can be used for filling. The resin has certain fluidity and can be directly injected into the cavity by injection. When filling, the thickness of each layer of resin shall also not exceed 2mm. After filling, the probe can be used to shape and remove the redundant resin, and then the light curing is used to complete the filling. This kind of resin is suitable for pit and fissure caries of class I cavity.
In recent years, a new type of bulkfill resin (bulkfill resin) has appeared in bulk filling technology. The material has been improved in many ways, and the curing depth can reach 4-5mm, so it can be filled 4mm at a time clinically. The big filling resin has a great advantage for the deep cavity filling. Bulkfill resin is also divided into high viscosity and low viscosity. The high viscosity type can be directly filled. After filling, the low viscosity type needs to be covered with at least 2mm of mixed filler resin (as shown in Fig. 6).
Figure 6 three filling technologies of composite resin
In clinic, dentists need to be familiar with the properties of different materials, so that they can choose the most suitable materials and filling technology in different situations.
Selection and application of forming sheet
For all dentists, it is the most difficult to fill the adjacent cavity (class II cavity) of the posterior teeth, and the key to restore the adjacent contact is easy to be ignored by doctors. Failure to restore the adjacent surface contact according to the specification may lead to over filling, formation of suspension of filling body, food impaction and bacterial retention, resulting in secondary caries, loss of filling body and even pulpitis, which directly reduces the success rate of the whole resin filling.
In the repair of class II hole, resin special forming sheet must be used to restore and shape the adjacent surface. There are three types of forming sheet commonly used in composite resin restoration: ① transparent plastic forming sheet, which is suitable for adjacent restoration of anterior teeth; ② segmented metal forming sheet, which is suitable for adjacent restoration of posterior teeth; ③ circle forming sheet, which is suitable for multiple tooth surface restoration.
The segmented sheet metal forming system includes sheet metal forming, special tweezers, fixing ring and opening pliers. The first generation of metal forming sheets are shaped like "bean petals", and the fixing ring is a single arm. In the second generation, small holes are added to the forming sheet to facilitate tweezers to clamp, and the fixing ring is double arms, which is more suitable for the tooth abduction space, so that the forming sheet can closely fit the tooth structure, and facilitate wedge insertion and removal (as shown in Figure 7).
Figure 7 use of adjacent forming sheet
In the repair of class II hole, the adjacent wall should be restored first. Pay attention to use the filling device to compress the filling in the direction of adjacent teeth as much as possible, which is helpful for the restoration of adjacent contact points. After the adjacent surface wall recovered to the height of the marginal ridge, the occlusal surface was filled again, and the cusps were restored one by one by using the cusp stacking method, and at the same time, the fossa was formed to restore the ideal occlusal surface shape.
Shaping and polishing
As the last step of the whole composite resin filling technology, reshaping and polishing are also the most easily ignored steps in clinical practice. Effective polishing can give full play to the aesthetic characteristics of composite resin, reduce the accumulation of plaque, reduce the incidence of secondary caries, and ensure the success rate of composite resin repair. Especially for the adjacent surface polishing is indispensable.
The diamond shaping drill is used for shaping. There are various polishing tools, such as polishing cup, polishing wheel, polishing brush, polishing strip and so on. Generally, there are two specifications, coarse and fine. The polishing strip is specially used for adjacent surface polishing (as shown in Figure 8).
Figure 8 adjacent polished instrument
Shaping and polishing procedure: first, carry out preliminary shaping after filling to remove redundant filling materials. Remove the rubber barrier, and then refine and adjust the occlusion. After checking and confirming that there is no occlusal high point, polish it. The principle of polishing is from coarse to fine. Before class II hole polishing, first check whether there is overhang on the adjacent surface with dental floss, and then polish the adjacent surface with polishing gauze from coarse to fine.
If the adjacent polishing strip cannot enter smoothly, wedge can be used to separate the two teeth slightly before polishing (operation method is shown in Fig. 9). Polishing cup or wheel is used for smooth surface polishing, and polishing tip or wheel is used for occlusal surface polishing.
Figure 9 use method of polishing sand bar
Composite resin repair technology is the most basic and routine clinical operation technology in stomatology. The whole process seems simple and not difficult, but it is not easy to do well. We advocate to strictly follow the operation specifications, carry forward the spirit of craftsman, step by step, and strive to be the best even for simple operation.
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