fimA
genotypes were determined
to be untypeable in
P. gingivalis
-positive subjects. It remains to be elucidated whether the
Periodontal Diseases in Children and Adolescents …
57
untypeable specimens contained only a single or multiple unknown
fimA
genotypes.
However, it is possible that this/these genotypes possibly belong to low virulence groups,
such as I, III and V. Taken together, these results suggest that the distribution of type II and
IV
fimA
genotypes is extremely low in children although only a limited number of children do
harbor
P. gingivalis
with low virulence for periodontitis. Furthermore, some adolescents were
found to possess the type IV
fimA
genotype, which are possibly related to the onset of
marginal periodontitis.
Figure 25. Detection of
P. gingivalis
and determination of
fimA
genotypes in children and adolescents.
Open and closed circles indicate the low and high virulence types, respectively.
7) Down’s Syndrome Subjects
Down‘s syndrome (DS) is known to be a genetic disease resulting from trisomy of the
21st chromosome, occurring in 1 out of 600-1000 births [86, 87]. It is widely known that
subjects with DS often develop extensive gingivitis at early stages and exhibit extensive rapid
and generalized periodontal breakdown in early adulthood, which is estimated to result from
impaired immune responses, fragile periodontal tissue and early senescence [18, 88]. Subjects
with DS are commonly encountered in daily dental practice; however, there is little
information on periodontal bacterial species using molecular biological techniques in these
subjects. Thus, we decided to analyze the bacterial species in DS subjects.
The distribution of periodontal species in 60 children with Down‘s syndrome (2 to 13
years old, 5 in each age bracket) was compared with those of 60 age-matched systemically
healthy controls [89]. There were no obvious signs of marginal periodontitis in the DS group
and no significant clinical difference from the control group. PCR detection of the 10
periodontitis-related species in subgingival plaque specimens showed that most of the
pathogens were detected with greater frequency in the DS children than in the controls
Kazuhiko Nakano, Atsuo Amano and Takashi Ooshima
58
(Figure 26).
T. denticola
,
T. forsythia
,
P. nigrescens
, and
C. rectus
were significantly
prevalent throughout all age brackets of the DS children. The occurrence of
P. gingivalis
was
also significant in the DS subjects over 5 years old. These results demonstrated that important
pathogens for several types of adult periodontitis, such as
P. gingivalis
,
T. forsythia
and
T.
denticola
[52], are frequently found in DS groups. Although these species are considered to
be transient in systemically healthy children, early colonization could occur in the DS group.
In addition, the severity of gingivitis was associated with increased varieties of the resident
pathogens as well as the distribution of
P. gingivalis.
Analyses of subgingival plaque
specimens from DS patients also showed that early-onset periodontitis in DS is mainly due to
the increased susceptibilityof the hostto the causative microbial agents including
P. gingivalis
with type II
fimA
genes. Furthermore, it was demonstrated that gingival fibroblasts from
subjects with DS were impaired significantly by
P. gingivalis
type II FimA as compared to
those from systemically healthy subjects [90]. This impairment is likely due to invasion of
P.
gingivalis
readily leading to impaired cellular motility, which is estimated to prevent wound
healing and the regeneration of periodontal tissues.
Figure 26. Periodontal bacterial species are detected in significantly higher numbers in children with
Down‘s syndrome as compared to those with systemically healthy children. Bold letters indicate the
common species in the children more than 5 years old. Underlines indicate the common species
identified in all age groups.
8) Children with Developmental Disabilities
Maintenanceof good oral hygiene is generally considered to be difficult in subjects with
developmental disabilities.This leads to speculation that the distribution of periodontal
speciesis different in these subjects as compared to systemically healthy individuals.
However, there are few reports describing these species in children with developmental
disabilities. Therefore, we determined the distribution of the periodontal bacterial species in
subjects attending daycare centers due to the developmental disabilities [91]. A total of 187
children (136 boys, 51 girls) aged 1-6 years attending daycare centers, were analyzed. They
were diagnosed withmental retardation (MR), cerebral palsy (CP), autism (AU), or pervasive
developmental disorders. Dental plaque specimens were collected from the buccal side of the
maxillary left second primary molar. PCR analyses demonstrated that
C. sputigena
was the
Periodontal Diseases in Children and Adolescents …
59
most frequently detected species (28.3%), followed by
A. actinomycetemcomitans
(20.9%)
and
C. rectus
(18.2%).
E. corrodens
,
C. ochracea
, and
P. nigrescens
were detected in
approximately 10% of the specimens, whereas
T. denticola
,
T. forsythia
, and
P. intermedia
were rarely found, and
P. gingivalis
was not detected in any of the subjects. The mean value
for the total number of the 10 tested bacterial species in all subjects was 1.16 species, which
was positively correlated with age. In addition, the total numbers of detected species were
positively correlated with the age of the subjects (Figure 27), with a maximum of 8 species
identified in one subject.
Figure 27. Total number of 10 periodontal bacterial species in each age group of children with
developmental disabilities. There were statistical significant differences among them (*P<0.05,
**P<0.01).
There were 10 subjects with positive reactions for
T. denticola
and/or
T. forsythia
, in
whom the total number of bacterial species was significantly higher as compared to the other
subjects. Furthermore, subjects possessing
C. rectus
showed significantly greater values for
periodontal pocket depth, gingival index, and total number of species, indicating that
C.
rectus
is one of the possible indicators for risk of periodontitis. On the other hand, the clinical
parameters evaluating periodontitis were shown to be worse in the group of subjects
complicated with concomitant MR, CP, and AU. The total number of the species detected in
this group of subjects was significantly higher than those of the other groups complicated
with a single or two concomitant diseases of MR, CP, and AU (Figure 28). It is reasonable to
understand that individuals with multiple developmental disabilities have great difficulties
with maintaining oral health and undergoing dental treatments as compared to subjects with a
single disability. In addition, the present results showed that one-fourth of the subjects with
disabilities were shown to possess at least one of the periodontitis-associated species (
T.
denticola
,
T. forsythia
, and
C. rectus
)and should also be regarded as possible subjects at risk
for the onset of periodontitis. These subjects are currently receiving special periodical
Kazuhiko Nakano, Atsuo Amano and Takashi Ooshima
60
professional oral health care. Periodical PCR detection of the species could be beneficial for
evaluating their current oral status and to estimate their future risk for the onset of
periodontitis.
Figure 28. Total number of 10 periodontal bacterial species in groups classified on the basis of the
number of the complicated disabilities. There were statistical significant differences among them
(***P<0.001).
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