INTRODUCTION:

Calcification which is uncontrolled due to failure of enzyme pyrophosphatase, reduction in capillary permeability and blood supply causes calcifications. Root canal in teeth in which calcific deposits blocking access to the canal (s), treatment efforts are often hindered. An effort to locate the residual canal might remove large amounts of dentin and there is a risk of root fracture and perforation. American Association of Endodontists defined Calcific Metamorphosis as “A pulpal response to trauma characterised by rapid deposition of hard tissue within the canal space.” This is also known as obliteration of pulp canal, Dystrophic Calcification, Diffuse Calcification and Calcific Degeneration.

Dental trauma to the permanent dentition can lead to clinical complications and its management may considerably challenge a practitioner.

One such complication is Calcific Metamorphosis (CM) which can complicate entry in to the root canal system in the future due to difficulty in accessing the canal

It is the Calcific deposits of the pulp chamber that causes the darker hue, translucency loss and the yellowish appearance of the tooth’s crown.

It is characterised by hard tissue deposition within the root canal space and a yellow discolouration of the clinical crown. The exact mechanism of canal obliteration is unknown but is believed to be related to damage to the neurovascular supply of the pulp during trauma.

These events and their clinical management can present important challenges to the odontologist; since the sequel can arise several years after the injury, proper medical and dental history, as well as a detailed history of the dental trauma, a thorough clinical examination will assist the dental provider in formulating a proper diagnosis and subsequently, adequate treatment.

The condition may be recognised clinically as early as 3 months after the injury but in most cases is not detected for approximately 1 year.

Other causes of CM can be dentinal dysplasia and dentinogenesis imperfecta, mainly type 2 and teeth which have been rigidly splinted. Calcific Metamorphosis is defined by the American Association of Endodontists as “A pulpal response to trauma characterised by rapid deposition of hard tissue within the canal space”.

This is more often observed in patients who have suffered concussion or subluxation injuries.

They can be associated with minor symptoms and, therefore, go unnoticed both by the patient and/or by the clinician.

It is generally accepted that the frequency of pulp canal obliteration is dependent on the extent of the luxation injury and the stage of root formation.

Radiographically, CM can be classified¹ as either: 1. Partial Obliteration–the pulp chamber is not visible and the canal is markedly narrowed but visible². Total Obliteration–the pulp chamber and canal is hardly or not visible Literature suggests that a narrow canal is always present irrespective of its identification on the radiograph.

According to Kronfeld and Boyle,³ there are two distinct types of calcification that occur in the pulp: Those more frequent in the radicular pulp are generally termed diffuse or linear calcifications, whereas those more commonly found in the coronal region are known as pulp stones (denticles). Denticles can be classified according to their structure into true or false. True denticles have dentinal tubules like dentin, odontoblastic processes, and few odontoblasts, whereas false denticles are concentric layers of calcified tissue with a central cellular area, which might be necrotic and acts as nidus of denticle formation. The difference between the two is morphological not chemical. According to their location, they can be classified into embedded, interstitial, adherent, and free denticles. The degree of pulp obliteration can further be classified as total obliteration, in which the pulp chamber and root canal are hardly or completely not discernible, and partial obliteration, in which the pulp chamber is not discernible and root canal is markedly narrowed but clearly visible⁴. However, total pulp obliteration is rare and usually a thin fine residual filament of pulp tissue or tract of organic material is present. It has been found that partial obliteration has no detrimental effect on the pulp. This can be better illustrated by the fact that, partial obliteration involves primarily the pulp chamber and has a more limited effect in the root canal and apical region. This might allow the circulatory system of these teeth to react adequately to maintain sufficient blood perfusion^5,6. There is yet another classification of pulp obliteration-localised and generalised⁷. In the localised form, the etiologic agent most often is trauma and this condition has been described relatively frequently after crown and root fractures, tooth luxation, jaw fractures, tooth replantation, and endodontic procedures The prevalence of pulp canal obliteration subsequent to traumatic injuries varies widely from 3.8% to 24%^8,9. The generalised form is probably part of the aging process and is usually seen in older individuals. The pulp chamber may be completely obliterated or hairline thin in most teeth and it is often accompanied by attrition. Treating a calcified canal can be of a challenge due to the narrowing of the pulp chamber and pulp canal. The narrowing of the pulp chamber will lead to the difficulty in locating the access of the canal and also cause a great difficulty during cleaning and shaping. Due to the calcification, it can also lead to breakage of the instrument while cleaning and shaping. Enlargement of the canal orifice is important to access the canal easily. Thorough cleaning and shaping is required to make sure that the obturating material can be placed into the canal. If the calcified tooth is asymptomatic then it is of not much concern whereas in a tooth with periapical pathosis endodontic treatment must be performed. There are various ways in which the pulp can show calcification like pulp stones or calcified metamorphosis. These conditions will also lead to discolouration of the coronal part of the teeth. Calcification is usually associated with trauma to the tooth which will stop the blood supply and decrease the vascularity over time leading to calcification. Due to the calcification of the canal, it might often lead to a failure of the root canal treatment because of the difficulty in locating the canal and gaining access to it. Calcification can be due to physical factors as mentioned before as trauma or can also be due to hereditary diseases like dentin dysplasia or dentinogenesis imperfect.

Calcifications Of Pulp:

Traditionally, calcified bodies in the dental pulp have been classified on the basis of their structural characteristics. The classification by Kronfield is most commonly used¹⁰.

1. "true" denticles (composed of tubular (ortho) dentin),

2. "false" denticles (composed of concentric layersof calcified material not resembling dentin),

3. “diffuse calcifications” (small calcified deposits scattered throughout the pulp tissue).

Firstly, one may easily, but incorrectly, assume that the histological properties of these calcified bodies are related to their mode of development (i.e. true denticles develop as the result of epithelio-mesenchymal interactions, while false denticles form on a calcified nidus). Asshown below, such a strict relationship does not exist.

Secondly, most pulpal calcifications are concoction of different tissues: orthodentin, regular, and irregular calcified material, so that a strict classification becomes nearly impossible^11-13.

1. Orthodentin, tubular dentin, may be detected both in denticles and in pulp stones.

a. Denticles, formed as the result of epithelio-mesenchymal interactions, are composed of tubular dentin in the earliest stage of their development^14,15. Odontoblasts line the periphery of the denticles, but as the diameters of these calcified bodies increase, most or all of the odontoblasts become reduced in height and apparently perish.

Calcified metamorphosis is commonly seen in patients who have had injuries like concussion and subluxation¹⁶. These obliterations were found to be either fibrotic or bone like in primary teeth or bone like¹⁷.

Histology of osteodentine in primary teeth showed cellular inclusions. Increase in the collagen content and decrease in the number of cells were characteristics of tissue change in the maxillary permanent incisors¹⁸. Adjacent to mineralised areas in the pulp, osteoid tissues were also found. The deposition rate is uncontrolled with as high as 3.5 micrometer per day¹⁹. However, pulp stones are not similar to calcified metamorphosis. There are two types of pulp stones which include true and false. Dentine lined by odontoblasts are seen in true pulp stones. Degenerated pulp cells will lead to mineralisation forming false pulp stones²⁰. In case of calcified metamorphosis, there is initiation of odontoblastic activity²¹.

The injury in the neurovascular supply to pulp could lead to calcified metamorphosis²². According to an other theory, the calcification can happen due to the focal point created as the blood clot for calcification because of the bleeding in the canal incases when the pulp is vital after a trauma²³.

Radiograph:

Obliteration of the pulpal space is seen in the radiograph with no presence of pulp chamber. The lamina dura remains intact if there is no evidence of apical involvement of bone.

The chamber can be partially obliterated which means the pulp chamber is not visible and narrowing of canal whereas in total obliteration the pulp chamber is completely not visible and the canal also hardly visible but sometimes may not be visible also.

It is usually asymptomatic with yellow discolouration of the coronal part of the tooth clinically. Due to an increase in the dentine thickness the crown takes up a yellow colour. However, all the teeth do not have a similar discolouration with its most common site being the anteriors. It is commonly seen after three months of injury and sometimes will not be detected until one year. Pulp vitality test may show false negative response.

Management:

The obliterated pulp canal is debatable on showing no symptoms or pathosis of the periapical region. Continuous observation and follow up gives a better intervention before deciding the conclusion. The incidences according to literature on calcified tooth which develops pulpal pathology is at the range of 1-16%. However only external bleaching can be used as a treatment when the patient complains of only discolouration whereas in case of irregular dentin formation, the tooth discolouration will have to first undergo endodontic treatment followed by non-vital bleaching.

Root canal treatment requires a proper knowledge on the root canal anatomy and the variations that can be seen in it. The access cavity preparation is quiet helpful if prepared before the placement of rubber dam to evaluate the working length in the long axis of the tooth and to evaluate the root relationship. The rubber dam is placed immediately after the root canal is located and the treatment is continued.

Negotiation:

The use of Instruments:

A variety of "pathfinding" instruments have been introduced. DG-16 explorer is a very useful instrument in the location of canal orifice. Instruments with reduced flute can also be used, such as a Canal Pathfinder (JS Dental, Ridgefield. Conn) or instruments with greater shaft strength such as the Pathfinder CS (Kerr Manufacturing Co.), which are more likely to penetrate highly calcified canals. C+Files (Denstply, Tulsa, OK, USA) are also ideal for initial instrumentation of calcified root canals. They have a cutting tip that engages the dentin. The long neck (LN-bur) round bur (Caulk/Denstply, Tulsa, OK, USA), extended-shank round burs, such as the Mueller bur (Brasseler, Savannah, GA, USA), can also be used for locating the orifices of calcified canals. Apart from these, there is also the Munce Discovery bur (CJM Engineering, Santa Barbara, CA), which is similar to the Mueller but has a stiffer shaft and is available in smaller head sizes. The extra-long shank of these burs moves the head of the handpiece away from the tooth, improving the clinician's visibility during this delicate procedure. EndoGuide^® Burs (SS white, NJ, USA) increase visibility and control during endodontic exploration while locating canals and navigating deeply calcified canals. A technique using K files with modified tips has also been developed for the penetration of constricted canals. The tip of a#10 K file was sliced diagonally to make it thinner. Because this modified K file has an especially fine tip and an appropriate stiffness, it followed constricted or sharply curved canals well and had a high penetration potential. Use of nickel titanium files is contraindicated because of lack of torsional strength²¹.

Endodontic surgery:

Root-end resection and filling should be considered when a canal cannot be located. Clearly, such endodontic microsurgery is an option in the treatment of calcified canals as it offers a direct approach to the root apex. Canal identification can be problematic in the calcified canal after root resection. The guiding influence of a canal space will be non-existent in the calcified and previously unprepared canal system. It is likely that this will be a further complicating factor in carrying out surgery on a calcified canal system where there has been no attempt at orthograde root filling. The surgical treatment approach should be considered only in cases where nonsurgical treatment or retreatment has resulted in a persistence of periapical disease and/or symptoms²⁴.

Agents-Is There Any Role?

Chelator preparations have been advocated frequently as adjuncts for root canal preparation, especially in narrow and calcified root canals. Apical dentin is more frequently sclerosed, and is more mineralised. Several authors recommend liquid EDTA solution be introduced into the pulp chamber (pipette, cotton pellet) to identify the entrance to calcified canals 36²⁵.

Biomechanical Preparation:

Coronal flaring in a crown-down fashion is preferred. Incremental instrumentation is achieved by creating new increments between the established widths by cutting off a portion of the file tip, thus making it slightly wider in diameter. For example, if a 1 mm segment is clipped from a size 10 file, the instrument becomes a size 12, by trimming sizes 15, 20 and 25, instruments of sizes 17, 22 and 27 respectively can be created. In extremely sclerotic canals, only 0.5 mm segments are trimmed, increasing the instrument width by 0.01mm and making a size 10 into a size 11, etc. because cutting the shaft imparts a flat tip, a metal nail file is used to smooth the end and reestablish a bevel after the removal of any segment²⁶.

CONCLUSION:

Though negotiating and managing calcified canals can be challenging, they can be managed if a proper protocol is followed. Operator's skill, patience, and a proper armamentarium are the requisites to overcome the difficulties posed by these unforgiving canals for their successful treatment. The calcification of root canals are a challenge for the dentist and causes a lot of difficulty due to its calcification. The locating of the canal becomes difficult due to calcification and hence instrumentation also. These difficulties can however be managed by using various instruments to negotiate the canal.

REFERENCES:

1. Oginni AO, Adekoya-Sofowora CA. Pulpal sequelae after trauma to anterior teeth among adult Nigerian dental patients. BMC Oral Health. 2007;7:11.

2. Robertson A, Lundgren T, Andreasen JO, Dietz W, Hoyer I, Noren JG. Pulp calcifications in traumatized primary incisors. A morphological and inductive analysis study. Eur J Oral Sci. 1997;105:196–206.

3. Lundberg M, Cvek M. A light microscopy study of pulps from traumatized permanent incisors with reduced pulpal lumen. Acta Odontol Scand. 1980; 38:89–94.

4. de Cunha FM, de Souza IM, Monnerat J. Pulp canal obliteration subsequent to trauma: perforation management with MTA followed by canal localization and obturation. Braz J Dent Traumatol. 2009;1 (2):64–68.

5. Amir FA, Gutman JL, Witherspoon DE. Calcific metamorphosis: a challenge in endodontic diagnosis and treatment. Quintessence Int. 2001;32 (6):447–55.

6. Goga R, Chandler NP, Oginni AO. Pulp stones: a review. Int Endod J. 2008;41:457–468.

7. Fonseca GM, Fonseca MM. Calcific metamorphosis with pathological root resorption in permanent teeth: morphohistometric evaluation of two cases. 2015;33 (2):712–718.

8. Robertson A. A retrospective evaluation of patients with uncomplicated crown fractures and luxation injuries. Endod and Dent Traumatol. 1998; 14:245–56.

9. Cohen S, Hargreaves KM. Pathways of the Pulp. 10th Ed. St. Louis, Mo: Elsevier Mosby; 2011.

10. Stalhane I, Hedegard B. Traumatized permanent teeth in children aged 7–15 years. Part II. Swed Dent J. 1975;68:157–169.

11. Jacobsen I, Kerekes K. Long-term prognosis of traumatized permanent anterior teeth showing calcifying processes in the pulp cavity. Scand J Dent Res. 1977; 85:588–598.

12. Andreasen F, Zhijie Y, Thomsen B, Andersen P. Occurrence of pulp canal obliteration after luxation injuries in the permanent dentition. Endod Dent Traumatol. 1987;3:103–

13. Amir FA, Gutmann JL, E Witherspoon DE. Calcific metamorphosis: a challenge in endodontic diagnosis and treatment. Quintessence international. 2001 Jun 1;32 (6).

14. Goga R, Chandler NP, Oginni AO. Pulp stones: a review. International Endodontic Journal. 2008 Jun 1;41 (6):457-68.

15. Fonseca GM, Fonseca MM. Calcific metamorphosis with pathological root resorption in permanent teeth: morphohistometric evaluation of two cases. 2015;33 (2):712–718.

16. Robertson A. A retrospective evaluation of patients with uncomplicated crown fractures and luxation injuries. Endod and Dent Traumatol. 1998; 14:245–56.

17. Ajmera K, Mulay S. Multimodality esthetic management–a case report. Int J Sci Res. 2013; 4 (1):1176–

18. Andreasen F, Zhijie Y, Thomsen B, Andersen P. Occurrence of pulp canal obliteration after luxation injuries in the permanent dentition. Endod Dent Traumatol. 1987;3:103–115.

19. Vertucci FJ. Root canal morphology and its relationship to endodontic procedures. Endodontic Topics. 2005;10:3–29.

20. Siddiqui SH. Management of Pulp Canal Obliteration using the Modified-Tip Instrument Technique: A case report. Int J Health Sci. 2014;8 (4):427–428.

21. Kobayashi C. Penetration of constricted canals with modified K files. J Endod. 1997;23( 6):391–393.

22. Fischer C. Hard tissue formation of the pulp in relation to treatment of traumatic injuries. Int Dent J. 1974;24:387–396.

23. Krasner P, Rankow HJ. Anatomy of the pulp chamber floor. J Endod. 2004; 30:5–16.

24. Carrotte P. Surgical endodontics. Br Dent J 2005;198:71-9

25. Vassiliadis LP, Sklavounos SA, Stavrianos CK. Depth of penetration and appearance of Grossman sealer in the dentinal tubules: An in vivo study. J Endod 1994;20:373-6.

26. Weine F. Endodontic therapy. 5 ^th ed. St. Louis: Mosby; 1982. p. 390-402.

Received on 04.04.2018 Modified on 10.06.2018

Research J. Pharm. and Tech 2018; 11(8): 3727-3730.

DOI: 10.5958/0974-360X.2018.00683.2