Inflammatory
lesions of dental pulp infection origin are the most common periradicular
lesions of the jaws. Endodontic lesions may be classified into periapical
granulomas, chronic apical abscesses and periapical cysts. These three
endodontic lesions are usually unilocular, periapical radiolucencies of varying
in sizes and marginal definition.
The
differential diagnosis for large endodontic lesions will include odontogenic
keratocysts, ameloblastomas, lateral periodontal cysts, nasopalatine duct cysts
and periapical fibrous scars.
Periapical
inflammation is a direct effect of bacteria infection of the root canal system
(Kakeshashi et al, 1965; Moller et al, 1981). The inflammation is a result of
interaction between bacteria in untreated infected root canal systems and the
host’s defense or immune system. Inadequate infection control of the primary
infection is the main reason for the failed RCT, leading to persisting
periapical inflammation.
Studies
have shown that non-surgical root canal treatment failed because bacteria can
survive and maintain an infectious disease in periapical lesions, although the size
of the lesions were not mentioned (Tronstad et al, 1987; Tronstad et al, 1990;
Sunde at al, 2002). The microbiota of persistent apical periodontitis lesions
is composed of various types of microorganisms with biofilm-forming capacity. The
majority of the bacterial strains of extraradicular infection were facultative anaerobes (51.6%) and obligate anaerobic
bacteria (38.7%). Bacteria were also found in abscesses and cysts of
extracted teeth with lesions attached to the apices (Ricucci et al, 2006). Actinomycotic infections were found to be more common in
periapical infections than previously believed and apical surgery including
curettage of the infected area with resection of the involved roots is the
treatment of choice.
From a
histological point of view, large periapical lesions may either be
granulomatous or cystic. Both periapical granulomata and cysts have the same
clinical and radiographic appearance. It is difficult to differentiate between
the two lesions based on radiographic density of the periapical lesion. A very
well defined lining on the radiograph only indicates a long-standing lesion
that is slowly increasing in size, whereas a diffuse border indicates a rapidly
expanding lesion. The size of the radiolucency is also irrelevant to the
histological state of the tissue as both small and large lesions can be
granulomata, abscesses or cysts.
The
progression of apical periodontitis to periapical cyst may be seen as an end
stage of an ongoing host defense response to root canal infection. A periapical
cyst is believed to be a direct sequel of a periapical granuloma. The
transition from granuloma to cyst is based on gradual increasing proportions of
epithelium and development of a defined lumen. Although there are several theories
proposed, little is known of the pathogenesis of cysts. The prevalence of periapical
cysts among apical periodontitis lesions ranges from 8.7% to 37.7%, using
different criteria in histological studies. Granulation tissue with epithelial
proliferation without cavitation is an insufficient diagnosis of a cyst, and is
classified as granuloma. Based on strict histological criteria used by Nair et
al (1996), cystic formation are often in the minority and may constitute 15% of
lesions studied, 9% true cysts and 6% periapical pocket cysts. As the pocket
cyst is directly connected to the root canal system, healing is likely to occur
after removal of intracanal bacteria during RCT. A true cyst is self-sustaining
because the lumen of a true cyst is completely enclosed by the epithelium and
there is no communication with the root canal system. Since the cyst is
independent on presence of absence of irritant in the root canal, it is not
likely to resolve by RCT and thus surgical intervention is necessary.
Retreatment was carried out prior to surgery. Biomechanical instrumentation reduces
microorganisms and their toxins in the root canal system. Together with a good
quality root canal filling and a retrofill with a tight seal, the egress of
microorganisms and their toxins from the canals into the periapical tissues will
be kept to a minimum. This promotes healing and ultimately, reduce the incidence
of healed lesions relapsing.
To ensure
a good outcome of an apical surgery, the main treatment concepts are outlined
below:
1. Magnification and illumination using the
dental operating microscope
The outcome of endodontic surgery was compared between the use of dental
operating microscope and loupes or no magnification, in a meta-analysis of 101
articles from the endodontic literature (Setzer et al, 2012). The probability
for success for endodontic microsurgery proved to be significantly greater than
the probability for success for conventional root end surgery, providing best
available evidence on the influence of high-power magnification rendered by the
dental operating microscope or the endoscope.
2. Achieving profound hemostasis
Hemostasis is essential for better visualization during apical surgery
to create a dry surgical site to facilitate the insertion of root end fillings
and reduce post-operative bleeding. Vasoconstrictors in local anesthetics
reduce the blood flow at the surgical site. The use of 1:50000, or at least
1:80000 epinephrine (as in Articaine) is recommended. Cotton pellet with
epinephrine and ferric sulphate can effectively control bleeding.
3. Always resect the root and retrofill
Resection of 3mm of the root tip
reduces more than 90% of the apical ramifications and lateral canals, without
compromising on the strength and stability of the tooth. Root end fillings
placed after root resection shows greater healing success compared to those
with only root resection. The root end cavity preparation should be at least
3mm into the root dentin. The ultrasonic angled retrotips provide easier access
to the root end.
4. Choice of retrofilling material
This ideal root end filling material should be biocompatible,
regenerates periapical tissues and has excellent sealing ability. Amalgam as the
traditional retrofill material is unacceptable nowadays because its sealing
ability is questionable, it corrodes and tattoos the gingiva or mucosa. Mineral
trioxide aggregate (MTA) and zinc oxide eugenol containing materials, such as IRM,
are the more commonly used materials. MTA is extensively researched in
endodontics and it is shown to be biocompatible and bioactive when set and
produces a high pH before setting, which results in regeneration of periapical
tissues including cementum and periodontal ligaments. However, this material
requires mixing and not easy to manipulate. The endodontic pre-mixed
bioceramics (Totalfill BC RRM-Putty) contains calcium silicates, zirconium
oxide, calcium phosphate, tantalum oxide and fillers; has excellent mechanical
and biological properties; and easy to handle.
The resected
tooth was checked for clinical signs of persisting infection in every six
monthly review session. Radiographic signs of density change within the lesion,
trabecular reformation and lamina dura formation are evidence of periapical healing.
Scar tissue is a reparative response, producing fibrous connective tissue instead
of bone. Scars occurred more frequently when both the buccal and lingual
cortical plates are lost. Formation of the scar tissue should not be interpreted
radiographically as an endondontic treatment failure or misdiagnosed as an
infected lesion. A long-term review up to four years is essential to confirm
successful outcome of the apical surgery of these teeth.
