| Objective: To measure the morphologic parameters of pulp chamber in mandibular first molar in Chinese Han population using cone beam computed tomography (CBCT), to clarify the relationship between dental pulp chamber structure and surface anatomy and to study the relevance of pulp chamber diameter and dentin thickness with age, in order to further understand the anatomic characteristics of mandibular first molar pulp chamber in Chinese Han population, enrich tooth anatomy data, and provide a reference basis for clinical accuracy of oral diseases treatmentMethods:1. A total of 420 CBCT images in a Chinese Han population were chosen and divided into 6 age groups based on 10-year interval as follows: 15-24, 25-34, 35-44, 45-54, 55-64 and 65-74 years, which included 210 males and 210 females.2. These 420 patients’ data were measured by Galileo software of CBCT. Two researchers measured the selected samples respectively after the training. The following data of mandibular first permanent molar pulp in different direction were obtained: the distance between the lowest position of pulp chamber top and cemenal-enamel junction(CEJ), the distance between the pulp chamber floor and CEJ, the height and diameter of pulp chamber and dentine thickness of pulp chamber on long axis, M-D plan and B-L plan. The ratio of diameter of pulp chamber to dentine thickness was calculated in different direction.3. Statistical analysis was carried out with SPSS 21.0(α = 0.05). The differences were detected between different age groups and gender, and its correlation with age was analyzed after consistency inspection.Results:1. Consistency checking: Measurement of mandibular first molar pulp chamber data using CBCT was feasible. The measured data obtained by two researchers had good consistency.2. Positional relationship between the roof of mandibular first permanent molar pulp chamber and CEJ: In Chinese Han population, 92.9% of the roof of mandibular first molar pulp chamber were located below CEJ on B-L dimension; 96.9% were on M-D dimension, which was located within 1 mm below CEJ3. Age-related changes of the roof and the floor of mandibular first permanent molar pulp chamber: With aging, the lowest point of the roof of mandibular first permanent molar pulp chamber had a tendency to move toward the interconnects of CEJ. The floor of pulp chamber was located within 1-3 mm below the CEJ, the vertical distance between the floor of pulp chamber and CEJ was negatively related with age (P<0.05). The change of the floor with age was greater than the roof of pulp chamber(P<0.05).4. The landmark measurement parameters of pulp chamber: On long axis,the height of pulp chamber was 0.83±0.53 mm (the maximum was 3.33 mm and the minimum was 0 mm); The pulp chamber diameter on B-L plan was 2.83±0.55 mm (the maximum was 4.55 mm and the minimum was 1.45 mm); That is 3.32±0.61 mm on M-D dimension(the maximum was 4.88 mm and the minimum was 1.83 mm). The pulp chamber diameters was greater than the roof of pulp chamber(P<0.05).5. Dentin thickness average of crown: Dentin thickness of the roof of pulp chamber was 3.56±0.49 mm and it was 2.53±0.52 mm of the floor; 3.05±0.35 mm of buccal side,2.64±0.45 mm of lingua side; 2.73±0.38 mm of mesial side and 2.54±0.40 mm of distal side. Dentin thickness difference on different parts was statistically significant(P<0.05).Dentin thickness was positively correlated with age (P<0.05), excepting for buccal dentin thickness that had no obvious correlation with age(P>0.05).6. The relationship between pulp chamber parameters and crown dentin thickness: The ratio of diameter of pulp chamber and dentine thickness was 0.14±0.11 on long axis,0.51±0.13 on B-L direction and 0.65±0.18 on M -D direction. They were negatively related with age (P<0.05).7. Gender differences and the comparison between age groups: The measurement indexes had no statistical difference between the sexes(P>0.05); The comparison between various age groups were statistically significant(P<0.05)in addition to female buccal dentin thickness (P>0.05).Conclusion:1. Measurement of mandibular first molar pulp chamber data using CBCT is feasible.2. In Chinese Han population, the roof of mandibular first molar pulp chamber is located within 1 mm below CEJ . The floor of pulp chamber is located within 1-3 mm below the CEJ. They have obviously related to age. But there is no gender difference in the distance.The change of the floor with age is greater than that of roof of pulp chamber.3. The pulp chamber diameters are negatively related with age in different direction(P<0.05); dentin thickness is positively correlated with age (P<0.05); There is no obvious difference between the sexes (P>0.05). The height of pulp chamber, dentin thickness of the floor of pulp chamber, lingua side and distal side have the most obvious changes with age.4. The ratio of diameter of pulp chamber and dentine thickness are negatively related with age (P<0.05). The ratio of mesio-distally direction is maximal. |
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