Preface
xiii
subject, what form the disease
takes and how it progresses, are all dependent of
a wide variety
of factors. Therefore, the objective of this chapter is to outline the risk factors described for
the most prevalent chronic periodontal diseases (plaque induced gingivitis and chronic
periodontitis) and to explain some basic concepts related to the current understanding of the
role of these risk factors based on in vitro, animal and human studies. The review will focus
on the factors that may be associated with a direct increase in the likelihood of occurrence of
disease or an increase in its severity. The following factors will be discussed: 1) host
characteristics, such as age, gender and race; 2) social and behavioral factors (socioeconomic
status, cigarette smoking and emotional stress); 3) systemic factors, e.g. diabetes mellitus and
osteoporosis; 4) genetic factors; 5) tooth-level factors (root grooves, tooth position, caries,
occlusal discrepancies, iatrogenic restorations, root abnormalities and periodontal
parameters); and 6) the microbial composition of dental biofilm. Finally, this chapter will also
present literature-based evidence on predictive factors associated with patients and tooth
susceptibility for recurrence of periodontitis after the end of the active periodontal therapy
and will examine the use of some prognostic models which may be useful for clinicians in the
identification high-risk groups of patients.
Chapter XV - The oral cavity is a warm, moist environment, in which a number of
microorganisms colonize and live in harmony as a community, a so-called biofilm. In this
environment, antimicrobial peptides may play a critical role in maintaining normal oral health
and controlling innate and acquired immune systems in response to continuous microbial
challenges in periodontal disease. Two major families of antimicrobial peptides, found in the
oral cavity, are defensin and cathelicidin. Members of the defensin family are cysteine-rich
peptides, synthesized by plants, insects, and mammals. These peptides vary in length and in
the number of disulfide bonds, and have a beta-sheet structure. In the oral cavity, four alpha-
defensins are synthesized and stored in neutrophil granules, which are converted into active
peptides by proteolytic processing, while three human beta-defensins (hBDs), hBD-1, hBD-2,
and hBD-3, are predominantly produced by oral epithelial cells. The only member of the
cathelicidin family found in humans is LL-37, an alpha-helical peptide that contains 37 amino
acids and begins with two leucines at its NH3-terminus. LL-37 is derived from enzymatic
cleavage of a precursor peptide, namely, human cationic antimicrobial peptide-18. Clinically,
differential expression of antimicrobial peptides has been reported in specific types of
periodontal disease, and their presence has been shown in saliva and gingival crevicular fluid.
Current evidence suggests that alpha-defensins, beta-defensins, and LL-37 have distinct, but
overlapping, roles in antimicrobial and pro-inflammatory activities. Several studies have
shown antimicrobial activities of hBD-2, hBD-3, and LL-37 against several periodontal
pathogens, suggesting their potential role as antimicrobial agents for periodontal disease. The
clinical significance of antimicrobial peptides in periodontal disease has recently been
demonstrated in morbus Kostmann syndrome, a severe congenital neutropenia, in which
chronic periodontal infection in young patients, resulting from a deficiency of neutrophil-
derived antimicrobial peptides, causes early tooth loss. Although researchers initially focused
their attention on antimicrobial activities, it is now becoming evident that defensins and LL-
37 are multifunctional molecules that mediate various host immune responses, and may thus
represent essential molecules of innate immunity in periodontal disease. In this chapter, basic
knowledge and the clinical importance of antimicrobial peptides in periodontal
disease will be
discussed in detail.