Periapical lesions, when they grow big and stubborn

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.

Root canal treatment (RCT) or retreatment is the first line of treatment for large endodontic lesions. If these lesions do not resolve after RCT, then apical surgery would be indicated. Other indications of apical surgery include failed retreatment cases due to calcified canals, procedural errors, eg. separated instruments or any obstructions that prevent thorough biomechanical preparation of the root canal system, apical transportation, foreign body or excessive root filling material in the periapical lesion and/or the presence of post restorations. 

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.

Hola Espana!

This is my first ESE (European Society of Endodontology) Biennial Congress at Barcelona. It was attended by more than 3000 endodontists/dentists/postgraduate students from all round the world. Dental conferences like this one is perfect to catch up with old friends. Old ties renewed and some familiar faces reappeared. Barcelona is really a beautiful city with great beaches, delicious seafood tapas and friendly Spanish speaking people, and that made my 14-hour long flight from Kuala Lumpur worth enduring...

Peri-radicular healing

As a dental healthcare provider, I get self-satisfaction not only when my patients are happy with me, but when I see good results from my own work, especially when it comes to challenging root canal treatment. The radiograph showed periapical healing after one year, a favorable outcome of the root canal treatment for tooth 36 with chronic apical abscess. The evidence of bone filling the peri-radicular lesion never failed to put a smile on my face :)

The second case shows tooth 35 after apexification with MTA and periapical healing after nine months.

Digital radiography: Before & After

C-shaped canal in tooth 36 with large peri-radicular lesion, buccal swelling and deep lingual pocket. Three months review pa showed resolution of the lesion.

Retreatment on tooth 46 with underprepared canals and short root fillings.

Root canal treatment on tooth 26.

These images were taken using the Carestream RVG6100. Digital radiography provides much more clarity, with instant access to the images.

Happy Birthday Pa!

My dad will be turning 78 next week. I had to do a root canal on his tooth 26, a few months ago. It was a tough job because the canals were fine, calcified and long. He trusted me to deliver a high quality work on his tooth, like any parent who believes in his/her child. I didn't disappoint him. Although I could only complete the treatment in three appointments, I am quite satisfied with the results and I managed to find and treat the MB2 as well.

In the memoirs of my distant uncle, My Days in The Sun, by Mark Soo http://arecabooks.com/product/my-days-in-the-sun/  he described how my ancestors from China, came to Kampar, Perak to start up Chinese medicine halls there. It was an interesting read and I guess I may have inherited the genetic traits in choosing a career path in medicine. My dad grew up in Kampar. Unfortunately, the chinese medicine business deteriorated during the Second World War. He didn't have the luxury of a tertiary education because my grandfather passed away when he was seventeen. Being the eldest in the family, he had to take over the role of my grandfather and to start working in a bank in Ipoh at that age. My dad worked hard all his life to provide for the whole family. I respect him for that and I am very thankful for all that he has done for me.

Happy birthday Pa! Wishing you many more years of happiness!

Curved canals revisited

Occasionally, I will encounter extremely curved canals in my practice. These canals were treated with a lot of patience, perplexity and gentleness. Procedural errors like canal blockage and instrument separation are more likely to occur in these difficult canals. More flexible nickel-titanium files are recommended for shaping curved canals compared to stainless steel files which are more stiff, hence may lead to canal ledging and transportation. However, nickel titanium files are more prone to separation in very curved canals even in the hands of very experienced and skillful operator because of straining of the metal at the curvature. In other words, nickel-titanium files are useful in shaping curved canal but these are also easy to break.

Warm vertical condensation

The warm vertical condensation technique is my obturation technique of choice now because it is a more superior technique than the more commonly used lateral condensation technique. The warm gutta percha fills the root canal system three dimensionally, including the lateral and accessory canals. The inter-canal communications and lateral fins and slits are inaccessible to root canal instrumentation. After chemical debridement, warm gutta percha techniques predictably seal these areas and entomb residual bacteria. However the warm technique is more technique sensitive and the lateral condensation has got better apical control.

I used the lateral condensation technique for years because I was taught to do that during my undergraduate training. Subsequently I learned to master the warm vertical technique at Penn. We are still teaching our dental undergraduate students the lateral condensation and the single cone techniques, simply because the two techniques are easier to carry out but I think the warm vertical condensation is by far the best obturation technique.