An Animal Experimental Study On The Damage Of Deciduous Teeth Intrusion To The Development Of Permanent Teeth

ObjectiveThe aim of this study was to establish the experimental models of different-week-old dogs’ deciduous teeth contusions, and to observe the effects of deciduous teeth contusions on the growth and development of the corresponding permanent teeth when the corresponding permanent teeth erupted completely. Method1. 8 normal hybrid dogs with the same age was selected. The 8 dogs were divided into four groups(n = 2) among which there was a control group that receive no treatment. According to dogs’ ages, the experimental groups were divided into three groups: 6 weeks, 8 weeks and 10 weeks of age groups. The right second deciduous incisors, the right third deciduous incisors, the right deciduous canines were selected as experimental teeth. Every deciduous tooth was wedged into alveolar at the height of gingival margin at different times, which was defined as the contusional standard. X-ray examinations were performed on intruded deciduous teeth to observe the positional relationships between the deciduous teeth and the permanent dental germs.2. When the corresponding permanent teeth completely erupted, X-ray examination was performed to observe the developmental situations of permanent teeth and statistical analysis was also conducted.3. The scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS) were performed on corresponding permanent teeth to observe the defects of enamel surface. After that, mineral deficiencies on dental surface were analyzed.4. Result1. Observations and statistic analysis were performed when the permanent teeth completely erupted:(1) 6 weeks group: There were 6 teeth with enamel defects, 2 teeth with enamel defects as well as dental crowns deformities,1 tooth with hypomineralized enamel.(2) 8 weeks group: There were 2 teeth with enamel defects, 6 teeth with hypomineralized enamel, 1 tooth with deciduous tooth retention.(3) 10 weeks group: There were 1 tooth with enamel defects as well as curved root, 3 teeth with hypomineralized enamel.(4) control group: There was no positive findings on corresponding permanent teeth.2. X-ray examinations of the erupted permanent teeth: There were 8 teeth with evident enamel defects, 2 teeth with crown malformations, 1 tooth with root malformations, 1 teeth with deciduous tooth retention. But enamel hypocalcifications were not apparent on images.3. The scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS) of the abnormal permanent teeth:(1) Observations on deficient enamel under 5000 times electron microscopy(sem): The enamel defect parts had vague surfaces, small amounts of apatite crystals but no enamel structure; Observations on deficient enamel under EDS: The enamel defect parts had low content of calcium, phosphorus, sodium, sulfur.(2) Observations on hypomineralized enamel under 5000 times electron microscopy(sem): The enamel with bad mineralization had clear enamel outlines, conspicuously hypomineralized enamel with clubbed and cellular structures; Observations on enamel with hypomineralized enamel under EDS: The enamel with bad mineralization had low content of calcium, sodium and sulfur. ConclusionThis study established the experimental models of different-week-old dogs’ deciduous teeth contusions. X-ray examinations, scanning electron microscope(SEM) and energy spectrum analysis were performed on corresponding permanent teeth when they completely erupted. The results of this study suggested that the deciduous teeth contusion affected the growth and development of inherited teeth, and the effects were distinct at different times:(1) The main influences on dogs with an age of 6 weeks were enamel defect and crown malformation;(2) The main influences on dogs with an age of 8 weeks were enamel defect and enamel hypocalcification;(3) The main influences on dogs with an age of 10 weeks were enamel hypocalcification and root malformation.