Biomedical subjects

P Brudvik

Publications and source records attributed to P Brudvik.

10 recordsLinked to original sources

PubMed2001

Orthodontic tooth movement and de novo synthesis of proinflammatory cytokines.

Interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) are proinflammatory cytokines that are thought to play a role in bone remodeling, bone resorption, and new bone deposition. In the present work, in situ hybridization was performed to measure the messenger RNA expression of IL-1beta, IL-6, and TNF-alpha at 3, 7, and 10 days after the application of orthodontic force on the maxillary first molars of 12 rats. The contralateral side and 3 untreated rats served as controls. Measurements of the messenger RNA expression were selected as the means to investigate the role of orthodontic force in de novo synthesis of proinflammatory cytokines. After the application of force, the induction of IL-1beta and IL-6 was observed to reach a maximum on day 3 and to decline thereafter. No messenger RNA induction of either cytokine was measured in the control teeth. The messenger RNA expression of TNF-alpha was not detected at any time point of this study in the experimental or contralateral sides or in the control animals. Our data support the hypothesis that these proinflammatory cytokines may play important roles in bone resorption after the application of orthodontic force.

Animals↗

PubMed2000

Orthodontic movement induces high numbers of cells expressing IFN-gamma at mRNA and protein levels.

Cytokines are important signaling proteins that are liberated during immune challenges and exhibit many modulatory activities. However, their role in periodontal modeling during orthodontic tooth movement is not fully understood. The aim of this study was to analyze effects of mechanical force during orthodontic tooth movement, in the pressure zone, on the induction of interferon-gamma (IFN-gamma) as a proinflammatory cytokine of Th1 type and interleukin-4 (IL-4)/IL-10 as anti-inflammatory cytokines of Th2 type. In 12 Wistar rats 40-45 days old, the maxillary first molar was moved mesially by means of a closed coil spring for 3, 7, and 10 days. The contralateral side served as a control. IFN-gamma, IL-4, and IL-10 mRNA were determined by in situ, hybridization, and protein levels of IFN-gamma was measured by immunohistochemistry. Induction of IFN-gamma at both mRNA and protein levels was significantly higher on the experimental side than on the contralateral control side on day 3. The signal gradually became stronger on day 7 and remained high on day 10. Cytokines of the Th2 type (IL-4 and IL-10) were not detected at all examined time points in both pressure and contralateral control sides. Considering the potential immunoregulatory roles played by IFN-gamma, our data suggest that IFN-gamma may be involved in periodontium remodeling during orthodontic tooth movement.

Animals↗

PubMed1999

Chemokines are upregulated during orthodontic tooth movement.

In the early stage of orthodontic tooth movement, an acute inflammatory response characterized by the migration of leukocytes occurs. This response suggests the presence of specific chemotactic signals that may play a role in the mechanism of bone remodeling, in particular in resorption. The aim of the present study was to explore the induction of potential chemokines at the resorption side during orthodontic tooth movement. Monocyte chemoattractant protein-1 (MCP-1), regulated on activation normal T cell expressed and secreted (RANTES), and macrophage inflammatory protein-2 (MIP-2) were examined by in situ hybridization using radioactive synthetic oligoneucleotide probes. Mesial movement of the upper first molars was performed with a fixed appliance for 3, 7, and 10 days. The results demonstrated that MCP-1, RANTES, and MIP-2 were highly expressed during orthodontic movement. On day 3, MCP-1 showed maximum induction in the pressure zone, followed in intensity by RANTES and MIP-2, although not in the contralateral control side. The induction of these chemokines had declined on day 7 and reached low levels on day 10. Our data suggest that chemokines are induced early in the application of force, and such induction may contribute to the early inflammatory response that may be responsible in part for the ensuing bone remodeling.

Animals↗

PubMed1995

Transition and determinants of orthodontic root resorption-repair sequence.

When severe root resorption is observed during orthodontic treatment the clinician needs to know how the active process can be stopped. It is generally assumed that if active force is discontinued, the root resorption will end. The determinants of the resorption/repair sequence are, however, not well understood. The aim of the present study was to register and analyse determinants that may influence the extent of resorbed root surface, as well as the transition of a process of active root resorption into a process of tissue deposition/repair in the resorption lacunae. Using an experimental model that would simulate the first force-activation cycle, the upper first molars of rats were moved mesially by a fixed orthodontic appliance for periods between 2 and 21 days. The results revealed that (1) the extent of root resorption after 21 days corresponded with the maximal extent of the hyalinized zone; (2) a process of repair started from the periphery in the resorbed lacunae where the periodontal ligament (PDL) had been re-established, while ongoing active resorption was observed beneath the existing hyalinized tissue; and (3) root resorption continued in the area where hyalinized tissue persisted even after active force had terminated. It is hypothesized that determinants of continued resorption/repair generally seem to be associated with the persistence and removal of the necrotic tissue.

Animals↗

PubMed1995

The repair of orthodontic root resorption: an ultrastructural study.

It has previously been shown by light (LM) and scanning electron microscopy (SEM), that after force is terminated, repair of the orthodontic root resorption lacunae occur by deposition of new cementum. The ultrastructural details of the process are not well established. Since it has been hypothesized that a new barrier to protect the root surface is formed during the reparative phase, new information on this aspect of orthodontic root resorption may be valuable. The aim of the present investigation was, by using transmission electron microscopy (TEM), to study in more detail the repair of orthodontic root resorption lacunae and the re-establishment of the adjacent periodontal membrane (PM). Three experimental tooth movement groups of rats (age 40-45 days) were used. The maxillary first molar was moved mesially by a closed coil spring for 10, 14, and 21 days. The results indicate that transition of active root resorption into a process of repair which occurs even in the presence of a light force, is associated with invasion of fibroblast-like cells from the circumference into the active root resorption site. After 10 days, formation of new tooth supporting structures was seen in the periphery of the resorption lacunae, while active resorption by multinucleated odontoclast-like cells (OD) took place in the central parts. In the later phases, after termination of force, the repair process is similar to the early cementogenesis occurring during tooth development. New mineralized cementum was observed on the resorbed root surface by 21 days. After deposition of the new cementum, the structures of a new periodontal ligament (PDL) were comparable with the control specimens.

Animals↗

PubMed1994

Root resorption beneath the main hyalinized zone.

A previous investigation on the initial phase of root resorption associated with orthodontic overcompression of local areas of the periodontal ligament (PDL), indicated that a differentiation should be made between two stages: (1) the very first resorption occurring in the periphery of the main necrotic zone; and (2) the root resorption occurring on that part of the root surface situated beneath the main bulk of necrotic tissue (Brudvik and Rygh, 1993a). The aim of the present investigation was to study the latter stage. Attention was focused on: (1) the possible association between the presence of necrotic tissue and root resorption; and (2) the cells that invaded and removed the necrotic tissue, as well as the cells that started to remove/resorb the cementum. Mesial movement of the upper first molars (rats) and lower first molars (mice) was performed by a fixed orthodontic appliance. The results indicate an association between the root resorption, and the presence and active removal of the hyalinized tissue. Root resorption beneath the main hyalinized zone occurred in areas where invading cells were observed close to the root surface. The majority of the cells involved in removal of the necrotic tissue and resorption of the root surface were multi-nucleated and TRAP-positive. It is hypothesized that multi-nucleated TRAP-positive cells when reaching the subjacent contaminated and damaged root surface after having removed necrotic PM tissue, continued to remove the cementum surface.

Acid Phosphatase↗

PubMed1994

Multi-nucleated cells remove the main hyalinized tissue and start resorption of adjacent root surfaces.

Recent studies revealed that the initial root resorption occurred in the peripheries of the necrotic periodontal ligament (PDL) and was performed by mono-nucleated non-clast macrophage- and fibroblast-like cells (Brudvik and Rygh, 1993a, b). The aim of the present transmission electron microscopic (TEM) investigation was to study in more detail the cells involved in removal of the main hyalinized tissue and those involved in root resorption, occurring on the root surface situated beneath the main hyalinized tissue. Twelve male Wistar rats were used. The maxillary first molar was moved mesially by a fixed orthodontic appliance for 7 and 10 days. The results indicate that multi-nucleated giant cells (MNGC) without a ruffled border surface, as well as mono-nucleated macrophage-like cells were responsible for removal of the necrotic tissue and also for resorption of the surface parts of the root cementum. Although the present MNGC showed many morphological traits similar to the observed odontoclasts and osteoclasts, except for their lack of ruffled borders, it is assumed that they are derived from the mono-nucleated phagocytic system. Multi-nucleated clast-like cells with ruffled border were never observed near the remnants of the necrotic tissue. Such cells were found only in the resorption lacunae on root and bone surfaces.

Acid Phosphatase↗

PubMed1993

The initial phase of orthodontic root resorption incident to local compression of the periodontal ligament.

The present light microscopic investigation was undertaken in order to study the initial phase of orthodontic root resorption in areas of pressure and, more specifically, to focus on the first cells that penetrate the root surface. Twenty-one upper first molars (rats) and 31 lower first molars (mice) were moved mesially by a fixed orthodontic appliance. The experimental periods were 1, 2, 3, 4, and 5 days in rats, and 1, 2, 3, 4, 5, 6, 7, and 8 days in mice. Tartrate-resistant acid phosphatase (TRAP) and Haematoxylin Eosin (H&E) stains were used. Root resorption related to a hyalinized zone showed a consistent pattern: Root resorption started in the circumference of the necrotic hyalinized tissue. In the central parts of the hyalinized zone frontal root resorption occurred 3-4 days later than in the periphery. Indications that the mechanisms for circumferential and central resorption differed was the reason for presenting only the periphery stage in this paper. The initial penetration of cells into precementum/cementum occurred at the peripheries or at a short distance from the peripheries of the hyalinized zone. These cells were TRAP-negative, indicating that they were not clasts or clast precursors. Before this happened TRAP-negative macrophage-like cells were observed at the borderline between the hyalinized tissue and vital periodontal membrane (PM). TRAP-positive cells were first observed in the bone marrow spaces. During the later stages mono- and multi-nucleated TRAP-positive cells were participating in active removal of the hyalinized tissue toward the root surface, and in resorption of cementum and dentine.

Alveolar Process↗

PubMed1993

Non-clast cells start orthodontic root resorption in the periphery of hyalinized zones.

Previous research has indicated that orthodontically-induced root resorption is regularly associated with local trauma, most often with over-compression of the periodontal ligament (PDL). Recent research has revealed that the initial root resorption occurs in the periphery of the necrotic PDL, where mononucleated cells not stained by tartrate resistant acid phosphatase (TRAP), are the first cells to penetrate the root surface. The aim of the present transmission electron microscopic (TEM) investigation was to study in more detail the root surface during the initial penetration of cells into precementum and mineralized cementum. In 21 Wistar rats (age 40-45 days) the maxillary first molar was moved mesially by a closed coil spring for 6 and 12 hours, 1, 2, 3, 4, and 5 days. The results clearly indicate a role for mononucleated non-clast cells in the initial local removal of precementum and mineralized acellular cementum in the periphery not only near, but also at some distance from the compressed PDL. 1. Macrophage-like cells phagocytosed necrotic tissue in the middle of the PDL after 6 hours and near the root surface close to the hyalinized zone after 24 hours. 2. Fibroblast-like cells seemed to break down by phagocytic and collagenolytic activity the precementum near the hyalinized zone after 24 hours. 3. The surface layers of mineralized cementum were removed by mononucleated cells which occurred on the mineralized cementum after 3 days. 4. Multinucleated cells without ruffled border occurred in the PDL at some distance from the root surface after 24 hours. Multinucleated cells with a ruffled border towards the mineralized root surface were rare during the 5 days' period.

Animals↗

PubMed1991

Root resorption after local injection of prostaglandin E2 during experimental tooth movement.

The purpose of this study was to investigate the occurrence of orthodontic root resorption in connection with local injection of prostaglandin E2 (PGE2). The material consisted of 25 male Wistar rats. The control group comprised six animals where no force was applied. In five animals 0.1 ml of 0.1 micrograms/microliter PGE2 was injected in the gingival area of the upper right first molar. In one animal no PGE2 was injected. The animals were killed after 3 days. The experimental tooth movement groups consisted of 19 animals. Duration of experiments was 3 days, 7 days, and 10 days. The maxillary first molars on both sides were each moved mesially by means of a coil spring. On the right side 0.1 ml of PGE2 0.1 micrograms/microliters was injected in the gingiva on the buccal side of the upper first molar on days 0, 3, 5, and 7. On the left side no injection of PGE2 was performed. In three animals in the 7-day group the vehicle (Waymouth medium) was injected. There was no significant difference in root resorption between the experimentally moved teeth with and without local injection of PGE2, but a trend towards more root resorption was registered on the teeth where such injections had been performed.

Animals↗