Periodontal disease and pulpal infection are caused by polymicrobial infections involving both aerobic and anaerobic bacteria. While some of the same bacteria can be found in both infected root canals and periodontal pockets, the root canal flora is typically less complex. Necrosis of the pulp can lead to bone resorption and lesions around the root or in the furcation. These lesions may remain small or expand and involve both pulpal and periodontal tissues, complicating diagnosis and treatment. Appropriate endodontic and periodontal therapies are both usually required to fully resolve the issues.

20. Periodontal disease is now thought by most researchers to be caused by a
mixed anaerobic infection, modulated by a complex interplay with local and
host factors.
Pulpal infection is a polymicrobial process & is of an anerobic nature. As the
infective process proceedes, the proportion of strict anaerobic-to-facultative
organisms & the total number of bacteria increases.
An exception to this rule seems to be the microaerophilic A.
actinomycetemcomitans, which has been associated with aggressive
periodontitis (Newman & Socransky 1977).

23.  Most of the species that have been found in infected root canals
can also be present in the periodontal pocket.
(Moore 1987, Sundqvist 1994)
 Porphyromonas endodontalis seems to be very rare in oral
infections other than those of endodontic origin.
(VanWinkelhoff et al. 1988)
 Overall, the root canal flora does not appear to be as complex as
the periodontal flora of adjacent pockets. However, it is inherent
problems in bacterial sampling of periodontal pockets that strains
from more shallow levels of the site are harvested along with the
strains at the front of the lesion.

32. Necrosis of the pulp, however, can result in bone resorption and the
production of radiolucency at the apex of the tooth, in the
furcation or at points along the root.
The lesion that results may be:
an acute apical lesion or abscess,
a more chronic peri-radicular lesion (cyst or
granuloma) or
a lesion associated with a lateral or accessory canal.
The lesion may remain small, or it can expand sufficiently to
destroy a substantial amount of the attachment of the tooth
and/or to communicate with a lesion of periodontitis.

35. Different authors have created varying nomenclatures for these
pathologies, based on either etiological or clinical criteria, or a
combination of these factors.
Simon et al. (1972) separated the lesions of both periodontal and
pulpal tissues into the following groups:
Primary endodontic lesions with secondary periodontal involvement,
Primary periodontal lesions with secondary endodontic involvement, and
True combined lesions.

41. Appropriate endodontic therapy is sufficient to result in
healing of the lesion.
Occasionally an abscess of pulpal origin, through an apical or
lateral canal, may establish drainage through the
periodontal ligament & erupt into the furcation or the
gingival sulcus.

43. (A)Preoperative radiograph showing large
periradicular radiolucency associated with the
distal root and furcal-lucency.
(B)Clinically, a deep narrow buccal periodontal
defect can be probed. Note gingival swelling.
(C)One year following root canal therapy,
resolution of the periradicular bony
radiolucency is evident.
(D)Clinically, the buccal defect healed and
probing is normal.

44. Chronic periodontitis progresses apically along the
root surface.
In most cases, pulp tests indicate a clinically normal
pulpal reaction.
The prognosis depends upon the stage of
periodontal disease and the efficacy of periodontal
treatment.

46. The progress of periodontitis is slow.
The involvement of apical periodontium by the pulpal lesion may
obscure the symptoms of the periodontium.
Because the apical lesion tends to be the most painful lesion,
endodontic therapy is normally initiated first.
Endodontic therapy results in the resolution of the endodontic
lesion , but has little or no effect on the periodontal pocket, an
appropriate periodontal therapy is required for a successful result.

47. Such lesions may present with the characteristic of both
diseases, which may complicate diagnosis & treatment
planning.
The extent to which the periodontal lesion contributes to the
loss of bone is a key consideration in diagnosis & treatment
planning

51. (A) Preoperative radiograph showing periradicular
radiolucencies. Pulp sensitivity tests were
negative.
(B) Immediate postoperative radiograph of
nonsurgical endodontic treatment.
(C) Six-month follow-up radiograph showing no
healing. Gutta-percha cone is inserted in the
buccal gingival sulcus.
(D) Clinical photograph showing treatment of the
root surfaces and removal of the periradicular
lesion.
(E) One-year follow-up radiograph demonstrating
healing.