Cell proliferation and 3H-proline incorporation in periodontal ligament exposed to mechanical stress

Gingival Embrasure Fill In Fixed Implant-Supported Prosthetics: A Review

After provisional or definitive cementation of fixed implant-supported prostheses, spontaneous gingival proliferation may occur to fill the cervical embrasure areas of the prosthesis. Adequate oral hygiene, osseous spacing between the supporting implants and attached or immovable soft tissue may be the conditions that allow this phenomenon. This proliferation embrasure fill eliminates interproximal gingival voids, that is, black triangles, and makes the outcome more esthetically acceptable. Since interproximal prosthetic deign and implant positioning may be the primary factors for the fill, the gingival fill may be, in fact, an epulis.

Role of MAPK in mechanical force-induced up-regulation of type I collagen and osteopontin in human gingival fibroblasts

In addition to periodontal ligament, the gingival plays an important role in alveolar bone remodeling induced by physiological and mechanical stimuli. However, there are few reports showing the cellular responses of human gingival fibroblasts (HGF) to a mechanical force. This study examined the effects of centrifugal force on the proliferation of the bone tissue components, such as type I collagen (COL I), osteopontin (OPN), and osteonectin (ONN) in the HGF. The roles of extracellular signal-regulated kinase (ERK), c-Jun-N-terminal kinase (JNK), and p-38 kinase were also investigated. Centrifugal force induced cell cycle arrest in the G(1) phase without any cytotoxic effects and increased the levels of COL I and OPN expression in the cells but had no effect on ONN. The force-induced up-regulation of COL I was found to be mediated by both the ERK-c-Fos-COL I and JNK-c-Jun-COL I pathways, while that of OPN was mediated only by the ERK-mediated pathway. Our present findings suggest that centrifugal force up-regulates COL I and OPN expression in HGF, where both ERK and JNK play indispensable roles.

[The modification of the mechanically loaded periodontium during orthodontically induced tooth movement with nonsteroidal anti-inflammatory agents in an animal experiment]

In a total of 123 female adult Wistar rats the first upper molar was moved by orthodontics for more than 28 days. This orthodontically stimulated tooth movement was influenced by local application of Cu-salicylate, Cu-indomethacin or epsilon-Aminocapronacid. The application of Cu-salicylate and Cu-indomethacin caused reduced tooth movement, a decrease in osteoclasts in the pressure region of the periodontium, and an increase of hydroxyproline in the desmodont. Generally, the local application of Cu-nonsteroidal antiphlogistics seems to stabilize the experimentally induced tooth movement.

Distribution of 3H-proline within transseptal fibers of the rat following release of orthodontic forces

Maxillary right first molar teeth of rats were tipped mesially with an orthodontic appliance for 2 weeks (experimental group), 3H-proline was injected, and orthodontic forces were removed 6 hr later (time 0). The contralateral molar teeth of treated (internal control group) and age- and weight-matched untreated animals (external control group) were also studied. Diastemata were created between the molar teeth by the orthodontic appliance, and transseptal fibers between first and second (P less than 0.001) and second and third molars (P less than 0.005) were significantly lengthened as compared to external and internal controls at time 0. Diastemata between molar teeth were closed 5 days after removal of orthodontic force. Transseptal fibers adjacent to the source of the orthodontic force (mesial region) had the highest mean number of 3H-proline-labeled proteins at time 0 and at all times following removal of the force (P less than 0.001), and had the highest rate of labeled protein removal (P less than 0.001). Half-lives for removal of 3H-proline-labeled transseptal fiber proteins were significantly greater in mesial and distal regions and significantly less in middle regions of experimentals than in corresponding regions of external controls (P less than 0.001). These data suggest the following: 1) transseptal fibers adjust their length by rapid remodeling in regions experiencing a tensile force; 2) collagenous protein turnover within the middle third of the transseptal fibers is more rapid subsequent to release of orthodontic force than during normal physiologic drift, suggesting that this region adapts rapidly to changes in adjacent tooth position and that these fibers do not play a significant role in relapse of orthodontically relocated teeth; and 3) significant differences in turnover rates of 3H-proline-labeled transseptal ligament proteins of external and internal control quadrants suggest that tooth movement produces both local and systemic effects on collagenous protein metabolism.