The aim of this study was to investigate average working lengths of Korean posterior teeth and evaluate validity of endodontic file length.
The endodontic working length of the posterior teeth of 670 Korean patients were measured than each mean value and standard deviation were investigated than the frequency deviation and standard deviation per each length were calculated.
Among the canals of premolar, 66.5% of canal length was marked under 20 mm by endodontic working length and 95.4% could be measured under 22 mm and Among the canals of molars, 95.5% of canal length was marked under 20 mm endodontic working length.
With the result of measurement of endodontic working length of premolars of Korean, it suggested that 23 mm endodontic file is more proper than the 21 mm and 25 mm file on the market.
The purpose of this study was to regenerate human dental pulp tissues similar to native pulp tissues. Using the mixture of type I collagen solution, primary cells collected from the different tissues (pulp, gingiva, and skin) and NIH 3T3 (1 × 105 cells/ml/well) were cultured at 12-well plate at 37℃ for 14 days. Standardized photographs were taken with digital camera during 14 days and the diameter of the contracted collagen gel matrix was measured and statistically analyzed with student t-test. As one of the pulp tissue engineering, normal human dental pulp tissue and collagen gel matrix cultured with dental pulp cells for 14 days were fixed and stained with Hematoxyline & Eosin.
According to this study, the results were as follows:
1. The contraction of collagen gel matrix cultured with pulp cells for 14 days was significantly higher than other fibroblasts (gingiva, skin) (p < 0.05).
2. The diameter of collagen gel matrix cultured with pulp cells was reduced to 70.4% after 7 days, and 57.1% after 14 days.
3. The collagen gel without any cells did not contract, whereas the collagen gel cultured with gingiva and skin showed mild contraction after 14 days (88.1% and 87.6% respectively).
4. The contraction of the collagen gel cultured with NIH 3T3 cells after 14 days was higher than those cultured with gingival and skin fibroblasts, but it was not statistically significant (72.1%, p > 0.05).
5. The collagen gel matrix cultured with pulp cells for 14 days showed similar shape with native pulp tissue without blood vessels.
This approach may provide a means of engineering a variety of other oral tissue as well and these cell behaviors may provide information needed to establish pulp tissue engineering protocols.