Lysophosphatidic acid modulates the regenerative responses of human gingival fibroblasts and enhances the actions of platelet-derived growth factor.

BACKGROUND: Platelet-derived growth factor (PDGF) has been used to promote healing in many in vitro and in vivo models of periodontal regeneration. PDGF is known to interact extensively with another platelet mediator, lysophosphatidic acid (LPA), to enhance regenerative responses in non-oral systems. PDGF and LPA are both liberated by platelets in the blood clot, which is known to be critical in stabilizing early periodontal wound healing. The purpose of this study was to evaluate the basic interactions of LPA with primary human gingival fibroblasts (GF) alone and with PDGF-BB for promoting GF growth and migration, as well as their effects in an in vitro oral wound-healing model. METHODS: GF regenerative responses were measured using 1 and 10 microM LPA in the absence or presence of 1 or 10 ng/ml PDGF-BB. Cell growth was determined using [3H]thymidine incorporation and cell counting. Migration responses were measured using a microchemotaxis chamber. For the in vitro wound-healing experiments, GF were grown to confluence on glass slides, and a 3 mm wide wound was mechanically inflicted. Percent wound fill on days 4, 6, and 9 was analyzed using computer-assisted histomorphometry. RESULTS: GF exhibited proliferative and chemotactic responses to LPA. These responses were synergistic when LPA and PDGF-BB were present together. LPA on its own did not stimulate statistically significant wound fill, but when combined with PDGF-BB, wound fill was equivalent to the 10% serum positive control group by day 6 (5.5-fold of negative control, [P<0.001]) and again on day 9 (6-fold of negative control, [P<0.001]). CONCLUSIONS: These studies provide the first evidence that LPA stimulates human GF regenerative responses and that it interacts positively with PDGF-BB to regulate these actions. The results suggest that LPA needs to be further investigated in the oral system as a factor that should be considered for incorporation when designing new periodontal wound-healing therapies using PDGF.

Evaluation of a predoctoral implant curriculum: does such a program influence graduates' practice patterns?

PURPOSE: Didactic predoctoral dental implant education is part of the curriculum in most US dental schools. However, fewer than half offer laboratory instruction, and only a few allow dental students to place and restore dental implants. The additional time necessary for laboratory and clinical experience encroaches on an already crowded curriculum. Is the additional time necessary in the curriculum for laboratory and clinical experience by dental students reflected by the practice patterns of graduates who have completed such a program over the past 10 years? MATERIALS AND METHODS: A survey was designed to determine the implant practice patterns of graduates of the Creighton School of Dentistry, Omaha, Nebraska, for the 10-year period 1988 to 1997. These graduates had all participated in a formal undergraduate didactic and laboratory curriculum in implant dentistry. Approximately half also had the opportunity to place and/or restore dental implants while students. The survey was also sent to graduates (also 1988 to 1997) from a midwestern dental school without a formal laboratory or clinical component (used as a control group). The data were analyzed statistically. RESULTS: In comparison to the control group (56% versus 23%), more than twice as many Creighton graduates restore dental implants as a part of their general practice, surgically place more dental implants, refer more implant patients to surgical specialists, and seek more continuing education hours related to implant dentistry. These conclusions were all supported by statistical analysis of the data. DISCUSSION: Student clinical experience with implant dentistry appears to significantly increase the incorporation of implant dentistry into future dental practices. Even if clinical experience was not an option, a school curriculum which included both didactic and laboratory participation still significantly increased the number of graduates who included implant dentistry in their practices. CONCLUSION: The inclusion of laboratory and clinical experience in implant dentistry in the CUSD undergraduate curriculum resulted in significantly greater participation in implant dentistry at the general practice level.