ABSTRACT
Objective To study the effects of different root control attachment on root control and periodontal ligament （PDL） stress during canine distal translation in plastic aligner-based orthodontic treatment. Methods Through three-dimensional (3D) finite element technology, 11 models composed of 4 attachments and 3 kinds of loading were established. Namely, attachment A: no attachments; attachment B: traditional vertical rectangular attachment; attachment C: 1/4 spherical double optimized attachment; attachment D: double optimized door arch attachment; load a: 0.15 mm distal translation of the canine; b: load a+ application of 30 N·mm counterclockwise torque to stress surface of the attachment; load c: load a+ application of 30 N·mm counterclockwise torque to the entire crown. The root control effect of distal translation of the right maxillary canine was simulated with plastic aligner under different loads. Results Displacement modes of all models were distally tipped translation. The double optimized door arch attachment showed the optimal root control effect during canine distal translation. The root control effect for two groups of double optimized attachment was better than that of traditional rectangular attachment. The effect of adding attachments on root control of the canine was better than that of applying only counterclockwise couple. The PDL stress mainly appeared in distal alveolar ridge and root apex without attachment, while the PDL stress mainly appeared in distal alveolar ridge with attachment. Conclusions The most suitable measure to improve the effect of root control during canine distal translation is to use the double optimized door arch attachment in clinic.
ABSTRACT
Complex human tissues harbor stem cells and precursor cells, which are responsible for tissue development or repair. Recently, dental tissues such as dental pulp, periodontal ligament (PDL), dental follicle have been identified as easily accessible sources of undifferentiated cells. These tissues contain mesenchymal stem cells that can be differentiate into bone, cartilage, fat or muscle by exposing them to specific growth conditions. In this study, the authors procured the stem cell from pulp, PDL, and dental follicle and differentiate them into osteoblast and examine the bone induction capacity. Dental pulp stem cell (DPSC), periodontal ligament stem cell (PDLSC), and dental follicle precursor cell (DFPC) were obtained from human 3rd molar and cultured. Each cell was analyzed for presence of stem cell by fluorescence activated cell sorter (FACs) against CD44, CD105 and CD34, CD45. Each stem cell was cultured, expanded and grown in an osteogenic culture medium to allow formation of a layer of extracellular bone matrix. Osteogenic pathway was checked by alizarin red staining, alkaline phosphatase (ALP) activity test and RT-PCR for ALP and osteocalcin (OCN) gene expression. According to results from FACs, mesenchymal stem cell existed in pulp, PDL, and dental follicle. As culturing with bone differentiation medium, stem cells were differentiated to osteoblast like cell. Compare with stem cell from pulp, PDL and dental follicle-originated stem cell has more osteogenic effect and it was assumed that the character of donor cell was able to affect on differential potency of stem cell. From this article, we are able to verify the pulp, PDL, and dental follicle from extracted tooth, and these can be a source of osteoblast and stem cell for tissue engineering.