Effects of mechanical tension on matrix degradation by human periodontal ligament cells cultured in collagen gels.

BACKGROUND: Periodontal ligament (PDL) cells are thought to play a crucial role in the remodelling of periodontal tissues during orthodontic tooth movement. OBJECTIVE: The objective of this study was to analyse the effects of mechanical tension on matrix degradation by PDL cells cultured in collagen gels. METHODS: The gels were prepared free-floating or attached to the culture wells and cultured for up to 22 d. In free-floating gels very little mechanical tension is generated within the matrix, whereas in attached gels tension is highly increased. RESULTS: At d 8, free-floating gels had contracted to 2% of their original wet weight. Attached gels had contracted to only 40%, but by d 15 all gels had spontaneously detached from the wells and had contracted rapidly. The collagen content of free-floating gels had decreased to 30% of the initial value at d 22. Collagenase activity was detected in the culture media of the free-floating gels and the presence of matrix metalloproteinases (MMPs) 2 and 9 was shown by zymography. In addition, histological sections showed matrix degradation around the cells. This shows that ligament cells in free-floating gels are actively resorbing the collagen matrix. The collagen content of attached gels did not change during the first 8 d but, after detachment, it rapidly decreased to 2%. Therefore, mechanical tension seems to prevent degradation of the matrix. In contrast, relaxation of the tension enhances the resorptive activity. CONCLUSIONS: The sensitivity of PDL cells to mechanical tension may be essential for the remodelling of periodontal tissues and their adaptation to physiological and orthodontic forces

Interplay of mechanical loading and growth factors in the mandibular condyle.

Contains fulltext : 69653.pdf (publisher's version ) (Closed access)The mandibular condyle is an important growth site in the developing mandible. The growth of the condyle is known to be highly adaptable to functional factors. This property is exploited in orthodontics for the treatment of class II malocclusions and mandibular asymmetries. However, there is an ongoing debate on the efficacy of functional appliances. The comparison of experimental studies is complicated by the lack of detailed analyses of the load distribution within the condyle. In spite of this, there is a large body of evidence showing that mechanical manipulation of the condyle induces metabolic changes, and changes in the expression of growth factors and other signalling molecules. This review aims to give an overview of the role of growth factors in the condyle with special emphasis on their responsiveness to mechanical perturbation

Changes in the periodontal ligament after experimental tooth movement using high and low continuous forces in beagle dogs.

Contains fulltext : 58835.pdf (publisher's version ) (Open Access)The aim of this study was to evaluate histological changes in the periodontal structures of beagle dogs after using high and low continuous forces during experimental tooth movement. An orthodontic appliance was placed on the second premolar and the first molar by exerting a continuous and constant reciprocal force of 25 cN on one side and 300 cN on the other side of the mandible. Tooth movement was recorded weekly. Dogs were sacrificed after one, four, 20, 40, and 80 days for histological evaluation. Hematoxylin and eosin (HE) staining was used for tissue survey, staining for alkaline phosphatase as a marker was used for active osteoblasts, and tartrate-resistant acid phosphatase staining was used for osteoclasts. After 24 hours, the remodeling process had already started at the pressure and tension side, and in some samples hyalinization was found. In contrast to earlier studies, hyalinization was found throughout the entire experimental period, both in molars and in premolars. In the periodontal ligament of some teeth, small patches of hyalinization were found at the pressure side, mostly located buccally or lingually of the mesiodistal plane, whereas others showed large areas of necrotic tissue. It is concluded that hyalinization limits tooth movement, but there is no relationship with the force level

Transforming growth factor-beta3-loaded microtextured membranes for skin regeneration in dermal wounds.

Contains fulltext : 59208.pdf (publisher's version ) (Open Access)Adverse effects of wound healing, such as excessive scar tissue formation, wound contraction, or nonhealing wounds represent a major clinical issue in today's healthcare. Transforming growth factor (TGF)-beta3 has specifically been implicated in wound healing. Our hypothesis was that local administration of TGF-beta3 to excisional dermal wounds would diminish wound contraction and scar formation. Microtextured wound covers, containing different concentrations of TGF-beta3, were placed onto full-thickness excisional skin wounds in guinea pigs. Tattooed reference marks were used to quantify wound contraction. Sixty-four male guinea pigs in four study groups (5 ng TGF-beta3, 50 ng TGF-beta3, no growth factor, sham wound) were followed for up to 6 weeks. We analyzed 19 different parameters of wound healing. Results showed that, in some instances, the 50-ng TGF-beta3 group gave less contraction, whereas the 5-ng TGF-beta3 group gave more contraction. These differences confirm that TGF-beta3 has an optimum working concentration, and suggest this concentration to be closer to 50 ng than to 5 ng TGF-beta3. However, only very few significant differences occurred, and thus we conclude that the clinical relevance of our findings is negligible. Earlier studies, reporting clinically improved wound healing by TGF-beta3, could therefore not be confirmed by this study

Root resorption after orthodontic intrusion and extrusion:.

Contains fulltext : 48540.pdf (publisher's version ) (Open Access)The aim of this investigation was to compare root resorption in the same individual after application of continuous intrusive and extrusive forces. In nine patients (mean age 15.3 years), the maxillary first premolars were randomly intruded or extruded with a continuous force of 100 cN for eight weeks. Eleven maxillary first premolars from six randomly selected orthodontic patients served as controls. Root resorption was determined using scanning electron microscopy. Quantitative assessment of the percentage of resorbed area of the total root surface was performed on composite micrographs. The severity of root resorption was also assessed by visual scoring of the roots. Root resorption mainly occurred at the apical part of the roots in both experimental groups. A significant difference in root resorption was found between the intruded and the control teeth (P = .006) but not between the extruded and the control teeth. However, the mesial and distal root surfaces showed resorption on 5.78 +/- 3.86% of the root surface of the intruded teeth and 1.28 +/- 1.24% of the root surface of the extruded teeth, and this difference was significant (P = .004). In addition, a large individual variation was found. From this study, it can be concluded that intrusion of teeth causes about four times more root resorption than extrusion. Because the amount of root resorption due to intrusion or extrusion in the same patient is correlated, every clinician should be aware that the extrusion of teeth might also cause root resorption in susceptible patients

Interleukin-1 reversibly inhibits the synthesis of biglycan and decorin in intact articular cartilage in culture

Contains fulltext : 20443___.PDF (publisher's version ) (Open Access

Focal hyalinization during experimental tooth movement in beagle dogs.

Item does not contain fulltextThe aim was to study morphological differences between the periodontal structures of beagle dogs showing different rates of tooth movement under identical experimental conditions. An orthodontic appliance was placed on the mandibular second premolar and the first molar to exert a continuous and constant reciprocal force of 25 cN. Tooth movement was recorded weekly. The dogs were killed after 1, 4, 20, 40, and 80 days for histological evaluation. Haematoxylin and eosin staining was used for tissue survey, alkaline phosphatase staining was used as a marker for active osteoblasts, and tartrate resistant acid phosphatase staining was used for osteoclasts. After 24 hours, osteoclastic and osteoblastic activity had already increased at the pressure and tension sides, respectively, and, in some samples, hyalinization was found. In case of fast-moving teeth, areas of direct bone resorption at the pressure side and deposition of trabecular bone at the tension side were found throughout the experimental period. In the periodontal ligaments of teeth showing little movement, small patches of hyalinization were found at the pressure side, mostly located buccally or lingually of the mesiodistal plane. These phenomena were found in both molars and premolars and at all time points. It is concluded that small focal hyalinizations might be a factor that could explain individual differences in the rate of tooth movement

Retinoic acid signalling in the development of the epidermis, the limbs and the secondary palate

Retinoic acid (RA), the active derivative of vitamin A, is one of the major regulators of embryonic development, including the development of the epidermis, the limbs and the secondary palate. In the embryo, RA levels are tightly regulated by the activity of RA synthesizing and degrading enzymes. Aberrant RA levels due to genetic variations in RA metabolism pathways contribute to congenital malformations in these structures. In vitro and in vivo studies provide considerable evidence on the effects of RA and its possible role in the development of the epidermis, the limbs and the secondary palate. In conjunction with other regulatory factors, RA seems to stimulate the development of the epidermis by inducing proliferation and differentiation of ectodermal cells into epidermal cells. In the limbs, the exact timing of RA location and level is crucial to initiate limb bud formation and to allow chondrogenesis and subsequent osteogenesis. In the secondary palate, the correct RA concentration is a key factor for mesenchymal cell proliferation during palatal shelf outgrowth, elevation and adhesion, and finally to allow bone formation in the hard palate. These findings are highly relevant to understanding the mechanism of RA signalling in development and in the aetiology of specific congenital diseases

The influence of the sagittal split osteotomy on the condylar cartilage structure and the subchondral vascularization of the temporomandibular joint: a preliminary study in goats.

Contains fulltext : 48549.pdf (publisher's version ) (Closed access)OBJECTIVE: The concern that a sagittal split osteotomy of the mandibular ramus could compromise the subchondral vascularization and especially the venous outflow in the condylar area, which in turn could influence the structure of the condylar cartilage, prompted this preliminary study on goats. STUDY DESIGN: A sagittal split osteotomy was performed in the mandibular ramus at 1 side in each of 6 young adult goats. The contralateral side served as control. The animals were killed after different postoperative periods, ranging from 1 to 15 days. Histomorphometric analyses were performed after perfusion of the vascular system with India ink. CONCLUSION: Based on the observed cartilage thickening, the sagittal split osteotomy may influence the condylar cartilage in the first days postoperatively through a disturbance of the vascular supply