Human dental pulp cell culture and cell transplantation with an alginate scaffold.

Many studies on tissue stem cells have been conducted in the field of regenerative medicine, and some studies have indicated that cultured dental pulp mesenchymal cells secrete dentin matrix. In the present study we used alginate as a scaffold to transplant subcultured human dental pulp cells subcutaneously into the backs of nude mice. We found that when beta-glycerophosphate was added to the culture medium, dentin sialophosphoprotein mRNA coding dentin sialoprotein (DSP) was expressed. An increase in alkaline phosphatase, which is an early marker for odontoblast differentiation, was also demonstrated. At 6 weeks after implantation the subcutaneous formation of radio-opaque calcified bodies was observed in situ. Immunohistochemical and fine structure studies identified expression of type I collagen, type III collagen, and DSP in the mineralizing transplants. Isolated odontoblast-like cells initiated dentin-like hard tissue formation and scattered autolyzing apoptotic cells were also observed in the transplants. The study showed that subcultured dental pulp cells actively differentiate into odontoblast-like cells and induce calcification in an alginate scaffold.

Morphological classification of mandibular dental arch forms by correlation and principal component analyses.

To evaluate the morphology of dental arches, 53 (male: 29, female: 24) paired casts having normal dentitions and occlusion were selected from 396 (age: 18 to 26 years old; male: 257, female: 139) sets of dental study models. The mandibular dentitions were preliminarily classified as square, round-square, round and round V-shaped arches based on the conventional morphological descriptions. Midpoints of the incisor edge (I1R, I1L, I2R, & I2L), summits of the cuspids (CR & CL), buccal cusps of the premolars (P1R, P1L, P2R, & P2L), mesial buccal cusps of the first and second molars (M1R, M1L, M2R, & M2L), and the midpoint (A) of line I1R-I1L were designated as reference points. From A, let a vertical line intersected line M2R-M2L at reference point B. The line A-B intersected CR-CL at reference point E. We evaluated 1) the protrusion of the cuspids by 1. angle I2R-CR-P1R (angle R) + angle I2L-CL-P1L (angle L); 2) the curvature of the anterior teeth by 2. (A-B)/(CR-CL), 3. (180 degrees-angle(CR-A-CL), and 4. (A-E)/(CR-CL); 3) the length to width ratio of the dental arch by 5. (A-B)/(M2R-M2L); 4) the degree of roundness of the mandibular arch by estimation of 6. (rtheta5 - rtheta4)R + (rtheta5 - rtheta4)L; and 5) an item 7. for the differentiation of type I and type II round-square arches by relating the bilateral contour and position of break line P1-P2-M1-M2 (i) to line P1-M2 (ii). The data of items 1., 2., 3., 4., 5., and 6. were further standardized and summarized into three essential principal components: 1) the curvature of the anterior teeth, 2) the curvilinear contour of the dental arch, and 3) the length-to-width ratio of the dental arch. The results indicated that: 1) 36 cases (67.9%) of the mandibular dentitions were round-square arches which showed no prominent principal component. 11 cases (20.8%) were square arches and 6 cases (11.3%) were round V-shaped arches; no round arches was found in mandibular dentitions. 2) Statistical analysis indicated significant differences of items 3., 4. and 6. in various mandibular arches (Student's t-test). 3) By examination of the three principal components, significant differences of item 5. between the round V-shaped arches and square and round-square mandibular arches were evident (Student's t-test). The present study elucidated that morphology of the mandibular arch was determined by a parameters representing the curvature of anterior teeth (composed of items 2., 3. and 4., and another parameter (item 6.) representing roundness of the mandibular arch.