Residents’ journal review

Analyzing gene expression of periodontal cells tissue model after compression

Li Y, Li M, Tan M, Huang S, Zhao L, Tang T, et al. Analysis of time-course gene expression profiles of a periodontal ligament tissue model under compression. Arch Oral Biol 2012 October 29 [Epub ahead of print]

Periodontal (PDL) cells play an essential role in mechano-induced bone remodeling related to orthodontic tooth movement. However, the specific biochemical response of these cells to mechanical stimuli is not fully understood. In this investigation, a PDL tissue model was established through 3-dimensional culturing of human PDL cells in a collagen scaffold, which has been shown to simulate the behavior of the human PDL. The goal was to investigate and analyze the time-course gene expression profiles of this newly established PDL tissue model under static compression to provide new insight into the biomechanical behavior of the PDL. The PDL cells were cultured from the root surface of extracted premolars. The cells were cultured on sheets of poly lactic-co-glycolic acid. Four days after implantation, the cells were subjected to static compression with a modified weight method, in which a cover glass was placed over the tissue model, and then a glass bottle was placed on it, with the addition of lead granules for weight. One hundred grams was applied to 4-cm 2 poly lactic-co-glycolic acid sheets to produce a total compressive force of 25 g per square centimeter. Loading was done in 3 groups: 6, 24, and 72 hours. After compression, total RNA was derived from the culture, and microarray analysis was performed to determine the expression of various genes, followed by real-time reverse transcription polymerase chain reaction. Then proliferation of 3-dimensional cultured cells was investigated. Among the genes identified were osteoclastogenesis inducers ( CCL20 , COX-1 , COX-2 , RANKL , and others), osteoclastogenesis inhibitors ( IL-1Ra , NOG , OPG , and others), and other regulators of bone remodeling. Also notable was, that after prolonged compression, cell proliferation was significantly inhibited. These findings will help to expand our understanding of the role of the PDL under static compression in orthodontic tooth movement.

Reviewed by Nadim Guirguis

Alveolar cleft closure with distraction osteogenesis by using tooth-microimplant anchorage

Huang DY, Zhang JB, Li X, Chen SL. Treatment of alveolar cleft with distraction osteogenesis using anchorage with a tooth-microimplant joint in a dog model. Br J Oral Maxillofac Surg 2012;50:e104-8

Two methods of distraction osteogenesis have been used to treat alveolar clefts: fixed screws in the alveolar bone and dento-osseous transport. This study tested the efficacy of closing a cleft in 12 mongrel dogs by using conventional tooth-borne transport and a combined method of tooth-borne transport with a microimplant. Osteogenesis with tooth-borne anchorage in 6 dogs and distraction osteogenesis with a tooth-microimplant joint in the other 6 dogs were prepared. The maxillary teeth on 1 side in both groups were removed to create a cleft; 2 weeks later, an osteotomy was created. The microimplant-tooth group had a microimplant placed on the buccal side of the transport disk. An increased load of 0.8 mm per day with an arch expansion screw was used until the cleft closed completely. The tooth group showed bony resorption around the roots, and greater inclination of the teeth and the transport fragment, as shown by incomplete closure of the cranial portion of the cleft in 5 dogs. For the microimplant group, there was less bone resorption around the roots, less inclination of the teeth and the transport disk, and complete closure of all clefts. Two possible reasons believed for the success in the microimplant group were that the microimplant (1) alleviated the orthodontic forces on the teeth and (2) created nearly parallel traction on the transport disk, reducing the torque on the natural teeth. Surgical placement of microimplants is simple, their small size can be easily placed away from roots of teeth, and loading can be immediate. The method of a tooth-microimplant joint is a safe and effective treatment for closing a cleft.

Reviewed by Kenny Liu

Alveolar cleft closure with distraction osteogenesis by using tooth-microimplant anchorage

Huang DY, Zhang JB, Li X, Chen SL. Treatment of alveolar cleft with distraction osteogenesis using anchorage with a tooth-microimplant joint in a dog model. Br J Oral Maxillofac Surg 2012;50:e104-8

Two methods of distraction osteogenesis have been used to treat alveolar clefts: fixed screws in the alveolar bone and dento-osseous transport. This study tested the efficacy of closing a cleft in 12 mongrel dogs by using conventional tooth-borne transport and a combined method of tooth-borne transport with a microimplant. Osteogenesis with tooth-borne anchorage in 6 dogs and distraction osteogenesis with a tooth-microimplant joint in the other 6 dogs were prepared. The maxillary teeth on 1 side in both groups were removed to create a cleft; 2 weeks later, an osteotomy was created. The microimplant-tooth group had a microimplant placed on the buccal side of the transport disk. An increased load of 0.8 mm per day with an arch expansion screw was used until the cleft closed completely. The tooth group showed bony resorption around the roots, and greater inclination of the teeth and the transport fragment, as shown by incomplete closure of the cranial portion of the cleft in 5 dogs. For the microimplant group, there was less bone resorption around the roots, less inclination of the teeth and the transport disk, and complete closure of all clefts. Two possible reasons believed for the success in the microimplant group were that the microimplant (1) alleviated the orthodontic forces on the teeth and (2) created nearly parallel traction on the transport disk, reducing the torque on the natural teeth. Surgical placement of microimplants is simple, their small size can be easily placed away from roots of teeth, and loading can be immediate. The method of a tooth-microimplant joint is a safe and effective treatment for closing a cleft.

Reviewed by Kenny Liu

Three-dimensional computerized evaluation of collagen-based membranes for guided bone regeneration

Coelho PG, Giro G, Kim W, Granato R, Marin C, Bonfante EA, et al. Evaluation of collagen-based membranes for guided bone regeneration, by three-dimensional computerized microtomography. Oral Surg Oral Med Oral Pathol Oral Radiol 2012;114:437-43

The predictable and full regeneration of bone-tissue defects in the maxillofacial system has been a challenge to the dental profession since its early days. In terms of periodontal defects, the use of physical barriers called guided tissue regeneration has been 1 treatment method. By using physical barriers (membranes), migration of epithelial cells into the defect is prevented, and cells from the periodontal ligament and the alveolar bone can regenerate the deficient area. This study used 3-dimensional microscopic computerized tomography to evaluate the effectiveness of collagen-based membranes for guided bone regeneration. The results were compared with a control group. Eight female beagle dogs were studied. Three wall defects were created between the mesial and distal premolar roots of the second and third premolars. A collagen-based membrane was placed in 1 defect, and the other was left untreated. The defects were evaluated 2 and 16 weeks after the procedure with microscopic computerized tomography. The results showed significantly more fully regenerated sites at 16 weeks compared with 2 weeks. The distribution of treatment outcomes showed that, at 16 weeks, membrane-covered defects showed bone height and width gains. The study also showed that the membrane group had significantly more fully regenerated defects compared with the control defects. Quantifiable assessment of the reestablishment of defect dimensions is not possible through 2-dimensional histologic sections, and 3-dimensional computerized evaluations were used. The authors concluded that 3 wall defects can substantially benefit from the use of collagen-based membranes. By using microscopic computerized tomography, regeneration of bone width and height was demonstrated.

Reviewed by Jeong Rae Cho

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Apr 8, 2017 | Posted by in Orthodontics | Comments Off on Residents’ journal review
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