Type VII collagen is found as anchoring fibrils, located in intimate contact with epithelial basal laminas (Fig. 12). In addition to the fibrillar forms of collagen mentioned above, type IV collagen, an amorphous form of collagen, is found in the basal laminas of the epithelial lining and blood vessel walls, primarily in the lamina densa.
The other fiber types found in the periodontium are elastic fibers and oxytalan fibers. Elastic fibers are rather
scarce in the lamina propria. They are a more common constituent of the lining
submucosa. They consist of 2 major components, microfibrils made of fibrillin
and the amorphous component elastin. The latter provides the fiber with
its elastic properties.
Fig. 29: Section of perivascular connective tissue. The
intercellular spaces contain both elastic (EF) and collagen fibers (CF).
Fig. 30: Higher magnification of the elastic fibers shown in Fig. 29. 
Note
that elastic fibers consist of 2 distinct structural entities, a microfibrillar component
(MF) composed of the protein fibrillin, and an amorphous component (AE) that is
composed of elastin, the protein that gives the fibers their elastic properties. As
elastic fibers mature, the ratio of elastin to fibrillin increases. In the gingiva, most
elastic fibers are immature and poorly developed.
Oxytalan fibers are a fiber type related to
elastic fibers. They appear to consist of the microfibrillar component only, thereby
resembling very immature elastic fibers.
Fig.31: Section through gingival connective tissue in which oxytalan fibers (OF)
can be found mixed in among collagen fibers (CF). Oxytalan fibers are composed of
microfibrils similar to those found in elastic fibers, but without the amorphous elastin
bodies.
