| Objective:The aim of this study was to establish the experimental model of periapical periodontitis in dog’s deciduous teeth, observe eruption and development situation of corresponding permanent teeth, and to understand the effects of periapical periodontitis in dog’s deciduous teeth on corresponding permanent teeth. Methodology and Methods6 local hybrid dogs(age at about 40 days, weighs about 1kg, no gender limitation) were selected as experimental animals. Under local anesthesia, pulp opening and pulpectomy were performed on tooth I, tooth II, tooth III, tooth IV in area A, and tooth IV in area C. After that, all the pulp chambers were stuffed with saturated endotoxin cotton balls, and the holes of opened pulp chambers were temporarily sealed with zinc oxide cements. Tooth I, tooth II, tooth III, tooth IV in area B and tooth IV in area D were selected as control groups. The changes of the teeth and their corresponding apical mucosal color, shape and texture in dog’s mouth were observed on the 14 th day, 21 th day and 28 th day after operations. X-ray photographs were also taken to observe that whether the bone in apical zone had shadows and the changes of shadow scopes in X-ray photographs. The loss situation of deciduous teeth, eruptional situation of corresponding permanent teeth were observed. After all the deciduous teeth replaced by permanent teeth, the changes of color, shape and texture of corresponding permanent teeth were recorded. Micro-structural changes on the surface of pathological teeth were observed under SEM(scanning electron microscope). Combined with energy spectrum, statistical analysis was performed to analyze the calcium amount, phosphorus amount and the proportion of them in teeth. Result:1. The experimental model of periapical periodontitis in dog’s deciduous teeth was successfully established.2. General observation(by naked eye): 2 weeks after operation, the color of the teeth and mucosa in their corresponding root zone in experimental group was normal as before, as well as that of sealing materials. 3 weeks after operation, the sinus was observed on apical labial mucosa of deciduous incisors. The bone in apical zone had shadows in X-ray photographs. 4 weeks after operation, X-ray photographs showed that deciduous teeth had absorbed root tips with shortened length, and low-density transmission areas under root tips were observed. There was no abnormal change in root tips in control group; and no root tip absorption happened.3. Teeth eruptional situation: Early eruption happened in permanent teeth, with a rate of 60%.4. Reverse displacement happened in 3 permanent teeth during eruption, with a rate of 10%.5. Enamel dysplasia happened in 10 cases, with a rate of 33.3%. Among them, there were 4 cases with white spot lesions and 6 cases with hypoplastic enamel.6. Electron microscopic observations on white spot lesions area showed that enamel rods became thinner and had sharp tips. Enamel rods’ spaces became wider. Most of inter-rod substances were lost. Enamel with defect showed cellular-shape damage under electron microscope. There were unequal-sized defect on the surface with the exposed enamel below them.7. Energy spectrum analysis showed that calcium and phosphorus amount were relatively lower than that of control group. Calcium-phosphorus ratio showed no difference between experimental group and control group. Conclusion:1. LPS effect can rapidly induce pulp and periapical tissue to get inflammations, which can also rapidly establish experimental models of periapical periodontitis.2. Apicitis in deciduous teeth can result in abnormal eruption, hypoplasia, and even displacement of corresponding permanent teeth during teeth eruption. |
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