The purpose of the present study was to compare the cytotoxicity of mineral trioxide aggregate (MTA) to other commonly used retrofilling materials, Super-EBA and amalgam. This was accomplished using a cell viability assay for mitochondrial dehydrogenase activity in human periodontal ligament fibroblasts after 24-hr exposure to extracts of varying concentrations of the test materials, in both freshly mixed and 24-hr set states. Methyl methacrylate 2% (vol/vol) served as the positive control, and complete culture medium served as the negative control. Differences in mean cell viability values were assessed by ANOVA (p < 0.05). In the freshly mixed state, the sequence of toxicity was amalgam > Super-EBA > MTA. In the 24-hr set state the sequence of toxicity at a low extract concentration was Super-EBA > MTA, amalgam, and Super-EBA > amalgam > MTA at a higher extract concentration. This study supports the use of MTA in the root-end environment.

Normal function of gingival fibroblasts is essential for maintenance of the gingival extracellular matrix (ECM), but under inflammatory conditions in gingival tissue which may occur with tobacco use, they can also act in its destruction. The purpose of this study was to determine the effects of nicotine, a major component of tobacco, on gingival fibroblast proliferation, the production of fibronectin (FN), and the production and breakdown of type I collagen to elucidate its role in periodontal destruction associated with its use. A human gingival fibroblast strain derived from a healthy individual with non‐inflamed gingiva was used in this study. Nicotine at concentrations > 0.075% caused cell death, and at 0.075% and 0.05% it caused transient vacuolization of the fibroblasts. At concentrations of 0.001% to 0.075%, nicotine significantly inhibited proliferation (P ≤ 0.03), measured by the incorporation of [3H]‐thymidine into DNA. The production of FN and type I collagen was significantly inhibited by nicotine at ≥ 0.05% (P ≤ 0.001), measured using specific ELISAs. On the other hand, nicotine at ≥ 0.025% significantly increased collagenase activity (P ≤ 0.008), using [3H]‐gly and [14C]‐pro‐labeled type I collagen gels as substrate. The results show that, in vitro, nicotine inhibits the growth of gingival fibroblasts and their production of FN and collagen, while also promoting collagen breakdown. This suggests that nicotine itself may augment the destruction of the gingival ECM occurring during periodontal inflammation associated with smokeless tobacco use. J Periodontol 1995;66:1056–1064.

To investigate the mechanism of cyclosporine (CS)-induced fibrotic gingival enlargement, the effect of CS on the collagenolytic activities of 14 different human gingival fibroblast strains derived from healthy individuals with non-inflammed gingiva was examined in vitro. There was marked heterogeneity among individuals in basal levels of collagenase activity, and there was also variation among the subpopulations derived from one strain. Fibroblasts from different individuals also varied markedly in their collagenolytic response to CS (0.1 to 0.75 micrograms/ml). In most strains, CS decreased collagenase activity, but in some, the drug caused no change or significantly increased activities. In most of the subpopulations CS significantly decreased collagenolytic activity. Two of the fibroblasts strains and the subpopulations described above were examined for the production of immunoreactive collagenase and tissue inhibitor of metalloproteinase (TIMP). The two strains made similar amounts of collagenase, but differed markedly in TIMP levels; CS affected their collagenase production differently but had similar effects on TIMP. Among the subpopulations there was variation in the production of collagenase, although none made detectable levels of TIMP; they also varied in the production of both proteins in response to CS. In two of the subpopulations and in both strains at some concentrations, the effect of CS on the relative levels of collagenase and TIMP could account for the decreased collagenase activity; i.e., the level of collagenase was unchanged or decreased, and TIMP production was unchanged or increased. This study demonstrates the variation among individuals as well as intrastrain heterogeneity of human gingival fibroblasts with regard to collagenase activity and the production of collagenase and TIMP. The heterogeneity of the collagenolytic response of different gingival fibroblast strains and their subpopulations to CS treatment may partly explain the susceptibility of only some individuals to CS-induced gingival enlargement.

HEREDITARY GINGIVAL FIBROMATOSIS (HGF) is a fibrotic enlargement of the gingiva. HGF gingiva contains large amounts of interstitial collagen and other extracellular matrix (ECM) molecules. Increased proliferation and elevated production of the ECM molecules type I collagen and fibronectin (FN) could contribute to the clinical increased bulk of HGF gingiva. Fibroblast strains from HGF gingiva and normal human gingival fibroblast strains (GN) were used in this in vitro study. Fibroblast proliferation was determined by ELISA which measured the incorporation of 5-bromo-2'-deoxyuridine into DNA. The results showed that HGF fibroblast strains proliferated more rapidly than GN fibroblasts (68% to 488% increase, depending on the strains) (P < or = 0.01), the only exception being one HGF strain versus one normal strain. All HGF strains produced greater amounts of FN (measured by ELISA) than all of the normal fibroblast strains (23% to 49% increase, depending on the strain) (P < or = 0.04). Similarly, all HGF strains made significantly greater (P < or = 0.3) amounts of type I collagen (also measured by ELISA) than all of the normal strains (55% to 235% increase, depending on the strain). The results show that, in vitro, HGF fibroblasts display several phenotypic characteristics of activated fibroblasts: increased proliferative rates as well as increased production of FN and type I collagen, consistent with in vitro studies of fibroblasts derived from other types of fibrotic tissue. These results suggest that the increased proliferation of HGF fibroblasts and their increased production of extracellular matrix molecules such as collagen and FN may contribute to the clinical gingival enlargement characteristics of HGF.