Aesthetic solution for large maxillary anterior diastema and frenum attachment.

Resin-bonded porcelain veneer restorations can be used to correct unaesthetic diastemata caused by tooth position or discrepancies in the tooth size/arch development. The size of the diastema, size and proportion of the clinical crowns, tooth preparation, and dental occlusion require special attention; an excessive frenum attachment requires additional care and coordination of the treatment. This article describes the placement of six resin-bonded porcelain veneer restorations in a patient with a large diastema between the maxillary central incisors and associated frenum and soft tissue involvement. The learning objective of this article is to demonstrate the importance of pretreatment planning and problem solving in achieving predictable final restorations.

Follicular dendritic cells and B cell chemotaxis.

B cells isolated from germinal centers (GC) of immune mice 2-5 days after antigen (Ag) challenge migrate in response to chemotactic signals, whereas GC B cells isolated at other times and resting B cells do not. Since B cells are in direct contact with follicular dendritic cells (FDC) in GC we reasoned that FDC might play a role in enabling B cells to become chemotactically active. Resting B cells were co-cultured with FDC either with or without anti-mu-dextran (anti-mu-dex) as an Ag surrogate and/or recombinant interleukin (rIL)-4 as a T cell surrogate. After 3 days, the B cells were isolated and their migration to chemotactic factors contained in zymosan-activated serum assessed in microchemotaxis chambers. B cells incubated alone or with anti-mu-dex or rIL-4 showed minimal migration, which could be increased if both anti-mu-dex or rIL-4 were present. However, maximal migration was obtained when B cells were cultured with FDC, and this was not increased by addition of anti-mu-dex and/or rIL-4, indicating that the FDC signal was a primary signal and did not require pre-activation of the B cells. Checkerboard analysis using variation in concentration and location of the chemoattractant in chemotaxis chambers indicated that both chemotaxis and chemokinesis occurred. B cell migration began within 6 h of culture, peaked by 48 h and decreased thereafter. Removal of FDC or interference with FDC-B cell contact ablated or significantly decreased induction of B cell migration. Furthermore, induction did not require functional T cells. These data indicate that FDC can induce resting B cells to become responsive to chemotactic signals.

Chemotaxis of germinal center B cells in response to C5a.

An infiltrate of B cells and plasma cells is characteristic of certain chronic inflammatory lesions. However, mechanisms involved in the local accumulation of these cells have not been established. Efforts to demonstrate that B cells from normal animals can migrate in response to inflammation-induced chemoattractants have been inconclusive. The objective of this study was to determine if murine germinal center (GC) B cells could respond chemotactically to a C5a gradient. On successive days after secondary immunization, draining lymph nodes were harvested and the activated GC B cells isolated. These GC B cells were placed in modified Boyden chambers, incubated for 3 h and the distance the leading front of cells migrated through the filters was determined. The results show that GC B cells migrated to factors in zymosan- and lipopolysaccharide-activated serum. The migratory response demonstrated distinct kinetics. Cells isolated between 2 to 4 days after secondary immunization migrated, whereas cells isolated at day 0 and beyond day 6 did not. Checkerboard analysis revealed that the migratory response was attributable to both chemokinesis and chemotaxis. Anti-C5 inhibited the migration of day-3 GC B cells implicating C5 in the migration mechanism. Studies using recombinant C5a established that this C5 fragment was chemotactically active. In conclusion, GC B cells generally were not chemotactically active. However, at a particular stage of maturation B cells in the GC become responsive to C5a as a chemotactic agent. Thus, B cells from normal animals may respond chemotactically, and C5a may play a role in recruitment of recently activated B cells into inflammatory sites.

Effect of anti-oxidants on growth and lactic acid production by Streptococcus mutans.

The effects of three anti-oxidants--tertiary butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT)--on both growth and lactic acid production by eight cariogenic strains of Streptococcus mutans were investigated. Synergistic inhibitory effects of potassium sorbate on lactic acid production were also determined. All three anti-oxidants are phenolic derivatives and are commonly used in food systems due to their excellent "carry-through" properties during processing. Growth inhibition was determined by turbidity measurements at 600 nm. Lactic acid was assayed by gas chromatography, and bacterial DNA was assayed by the diphenylamine reaction. There were reduced growth levels of S. mutans due to the anti-oxidants and potassium sorbate for at least 12 hr, with TBHQ and BHA still inhibiting growth at 24 hr. Nearly all concentrations of anti-oxidants and potassium sorbate reduced lactic acid production by S. mutans, but only TBHQ significantly inhibited lactic acid production when the amount of acid per microgram DNA was calculated. A synergistic reduction of lactic acid production by S. mutans does occur in most combinations of potassium sorbate with anti-oxidants.