FUTURE OFDENTISTRY
Tooth agenesis (missing teeth) and supernumerary
teeth (more than the normal number of teeth) are
common problems. Tooth agenesis occurs in about
20% of the population, and third molars are by far the
most commonly affected teeth. Missing maxillary lat-
eral incisors and mandibular premolars occur at the
next highest frequency (Graber, 1978). Most super-
numerary teeth are present in the anterior maxillary
region (Garvey et al, 1999). Some cases of tooth-
number abnormalities occur sporadically (without
any family history). However, aside from the com-
mon variation of third molars, the pattern often is
transmitted through multiple generations of families,
indicating that the cause is due to a single gene of
major effect. Mutations in key regulatory genes of the
homeobox family such as MSX1 and PAX9 have
recently been identified as the cause of different forms
of hereditary tooth agenesis (Vastardis, 2000; and
Stockton et al, 2000).
Treatment
It is likely that there are disparities in access to
treatment for malocclusion and tooth agenesis. Just
over 30% of White teenagers receive orthodontic
treatment in the United States, nearly three times as
many as in the Hispanic population and four times
as many as in the African American population
(Proffit et al, 1998).
Traditional orthodontic approaches to the cor-
rection of malocclusions are effective, but new
approaches to therapy will continue to appear. For
example, a removable appliance-based, computer-
assisted treatment modality has been introduced for
minor tooth movement in adults. The profession
should continue to evaluate the efficacy of new treat-
ment modalities to increase access to ortho-dontic
care. Appropriate peer review of studies and claims is
required to assure evidence-based treatment.
ORAL AND PHARYNGEAL CANCERS
In 2000, more than 30,000 Americans developed
oral and pharyngeal cancers. Almost 8,000 Americans
died from this disease (Greenlee et al, 2000). Tongue
cancer incidence and mortality are reported to be
increasing significantly, especially among young White
males (Moore et al, 2000; and Myers et al, 2000).
This could be due to increased use of smokeless tobac-
co, but there have not been increases in rates of
cheek, gum and other mouth cancers, which are close-
ly linked to smokeless tobacco use. Increases in tongue
cancer have also been observed in the United King-
dom where oral snuff and chewing tobacco are infre-
quently used (Blot et al, 1996). Oral cancer in young
adults appears to be associated with the traditional
risk factors of tobacco smoking, drinking alcohol and
low consumption of fruit and vegetables, rather than
due to any unique or new etiological agent
(Mackenzie et al, 2000).Oral Cancer EtiologyOral cancer presents a highly complex challenge
in terms of understanding its etiology, diagnosis and
treatment (Blot et al, 1996; Silverman, 1998; and
Winn et al, 1998). A large number of factors influ-
ence risk of developing oral and pharyngeal cancers:u Heavy cigarette smoking and alcohol consump-
tion are strongly associated with increased risk
of oral and pharyngeal cancers (Blot et al, 1996;
and La Vecchia et al, 1997). Persons who con-
sume large quantities of both tobacco and alcohol
have an estimated 80-fold higher risk of oral
and pharyngeal cancers than do people that never
used these substances. Cessation of tobacco and
alcohol use is associated with a significant reduction
of risk after about 5 to 10 years. Dental professionals
can be effective in helping people to quit using tobac-
co by using interventions in dental office settings
(Severson et al, 1998; and Crews et al, 1999).u Diets high in fresh fruitsand possibly some veg-
etables have been associated with a 50% reduc-
tion in risk for oral and pharyngeal cancers, even
after adjusting for the effects of tobacco and alco-
hol (Blot et al, 1996; and La Vecchia et al, 1997).u Human Papilloma Virus (HPV) infection has
been suggested to increase risk of developing oral
cancers. This has led to hope of possible reduction
in cancer incidence through use of HPV vaccines
now undergoing clinical trials for genital-tract can-
cers. However, current data suggest that only a rel-
atively small portion of head and neck cancers have
major HPV etiological involvement, though addi-
tional data are needed to confirm this conclusion
(Schwartz et al, 1997; and Franceschi et al, 2000).u Oral lesionsthat may be considered "premalig-
nant" are found in about 2% of the population andDental and Craniofacial Research