Root Canal Treatment

Normal tooth cut in half

A Root Canal Treatment (RCT, Root canal therapy, Endodontic treatment) is a dental treatment for saving the tooth from being extracted. The tooth is decayed deep into a pulp chamber causing the nerve to expose to an oral cavity and infection process begins inside the root canals and drains at the root apex.

Root canal treatment helps remove infected or diseased pulp (blood vessels, nerves, and connective tissue) from the pulp chamber and the root canals inside a tooth. Failure to treat an infected or diseased pulp has several potential consequences such as acute and chronic dental infection that ultimately lead to the loss of the tooth.  After root canal treatment, the tooth becomes weaker, and a dental crown (cap) is required to protect the crown portion of the tooth from breaking.

Some dentists may determine to do root canal treatment when the decay is very deep and close to the pulp even if the tooth is vital and no indication of infection. This decision is made based on the risk of exposing the dental pulp that the dentist may encounter while excavating of the decay.  As a patient, you may want to know if there is any other way to avoid taking the risk of exposing the pulp and having the root canal treatment in a vital tooth. 

According to the California Dental Association Journal published in January 2016, the use of Silver Diamine Fluoride (SDF) has been found to arrest and prevent dental caries.  Therfore; if the dentist apply SDF at the deepest part of the decay without removing all the decay, the silver kills the bacteria and stop the decay, while fluoride hardens what is left through remineralization.  SDF has been approved by the U.S. Food and Drug Administration in 2014. Consult with your dentist if this application can be applied to you.

Root canal treatment includes:

• Remove decayed materials and re-shaped each canal
• Fill the canals with root canal fillers (gutta-percha) and root canal cement. 

Terminology

Enamel - the white outermost of tooth structure
Dentin -  The second layer next to enamel, consist of small tubules
Pulp chamber - The inside of the tooth crown where blood vessels and nerves innervated, it provides nourishment and sensory to the tooth
Ligament - the tissue that support tooth structure to a bone
Root apex - The end of the root where nerve and blood supply entrance

When decay penetrates a pulp chamber, the infection spreads inside the tooth (pulp chamber and root canals), and form an abscess at the root tip.  Without root canal treatment; the abscess enlarges, more bone is destroyed at the root tip area, accompanied by severe pain, and swelling of the gums adjacent to the abscess.  A root canal treatment will bring relief to the infected tooth.

"Endodontist" is a specialist who performed a root canal treatment. Root canal treated tooth is brittle.  To protect the tooth from future fracturing, the dentist places a crown on the tooth. In children, before age 18, a temporary crown such as stainless steel crown is recommended.  Additional pins and post may be needed to strengthen the restoration.

Locate an Endodontist:
U.S from American Association of Endodontists,  
The United Kingdom go to British Endodontic Society 

Side effect of root canal therapy

1. Paresthesia related to root canal treatment (burning, aching, tingling, numbness and itching on the face) caused by nerve injury. The most common nerve affected by root canal treatment is the inferior alveolar nerve.  The inferior alveolar nerve runs inside mandibular canal in the lower jaw, close to the root tips of lower teeth; allowing the mechanical or pathological origin to affect the nerve.

Causes of paresthesia related to root canal therapy

• One or more of root canal procedure extends beyond root apex (apical foramen, root tip) and irritate the nerve. For example; excessive preparation of the root beyond the apex, extreme pressure during irrigation, and  extrusion of root canal filling (gutta-percha) and root canal sealer
• Accumulated purulent exudation around a root tip, creating pressure to the nerve
• Injection to the nerve during local anesthesia, causing injury to the nerve
• Injection of a contaminated anesthetic agent such as alcohol.

Note: other factors that may cause paresthesia are:

• Systemic factors: Leukemia, Multiple Sclerosis, Lymphoma, and viral infection.
• Local factors in dentistry (not related to root canal treatment) such as fractured jaw bone, cyst, benign or malignant tumor, impacted tooth, local infection from implants, anesthetic injection, orthodontic surgery

An accurate patient history, oral exam, radiography (periapical, panoramic, computed tomography scan), and the variety of tests are required to determine the cause and evolution of paresthesia.  Paresthesia may last for months or years.

Treatment of paresthesia 

1. Infection-related, paresthesia subsides after removal of the cause through root canal treatment
2. Injured by needle, paresthesia resolves itself after approximately eight weeks
3. Surgery improves long-term paresthesia

Prolong contact to an overfilled root canal filling and sealer, nerve fiber laceration from the needle, and prolonged pressure on the nerve may cause long-term or sometimes permanent paresthesia due to nerve fiber degeneration.

2. Pain due to recurring infection and swelling; resolves by re-do root canal treatment or sometimes extraction.

3. Tooth discoloration; resolves by placing a crown or internal bleaching (usually done on a single tooth)

Before and after tooth bleaching

4. Tooth and root fracture

5. Affect tooth growth in children

Why some patients experience pain or discomfort after root canal treatment?

During a root canal treatment, the dentist removes the nerve and blood supply from the pulp chamber inside the tooth; therefore the tooth itself doesn't have any sensation. But the sensation comes from the outside of the root, some of the tissues and nerves at the root tip may have been inflamed or infected during the procedure. This inflammation can make the tooth become discomfort or even painful after the root canal treatment.


Some other causes of pain are:

• Irritation caused by overflow of root canal filler to outside of the root canal
• Incomplete of root canal treatment
• Cracked tooth due to large opening inside the canal weakens the structure of the tooth
• The filling over the post is too high

Root Canal Treatment Procedure (see illustration below):

1. Instrumentation stage; the dentist uses different file sizes to remove all decayed materials, nerves, and other infected materials from the tooth and the root canals and re-shape the canals to specification


2. Irrigation; the dentist uses 0.5-6% hypochlorite (NaOCl) as an endodontic irrigation to clean and remove debris from the canals.  Hypochlorite helps killing bacteria and dissolve necrotic organic tissue inside the root.


3. Drying; the dentist dries the root canal with paper points.


4. Filling; the dentist fills the canal with gutta-percha and root canal sealer and fills the pulp chamber with temporary filling


5. The dentist waits until there is no infection before placing post-core and crown over the treated root canal tooth to strengthen the tooth.

Without root canal treatment; certain bacteria harbor in the infected root tips can travel to other parts of the body including the heart valve. The infection at the root tip builds up pressure that can push the tooth out of its socket causing bite disharmony, toothache.

Without root canal treatment, the remaining abscess inside a jaw bone may constantly feed live and dead bacteria and its toxin into the bloodstream. Taking herbs, vitamins, or even antibiotics prescription may temporarily solve the problem. The correct treatment is to perform root canal therapy or a dental extraction to remove the bacteria-harboring place.

The illustration of root canal treatment

1. Position rubber dam over the tooth and stabilize with rubber dam clamps to prevent contamination from saliva and keep the area clean during the treatment.

2. Remove blood vessels, infected tissue and decayed material inside crown.

4. Clean and shape the root canal walls with different size of files

5. Dry the canals with paper points.

6. Fill the canals with gutta-percha: a root canal filler. The gutta-percha seals the canals, prevents bacteria and fluid to enter the root canals.

7. Clean the excess gutta-percha inside pulp chamber(crown), prepare the root for the dental post to strengthen the tooth structure if needed.

8. Place the filling material over the post to re-build the crown, re-shape the filling, remove excess material, and check for a high spot.

9. Take X-ray to confirm the root canals were treated properly.

Place the permanent crown on the root canal treated tooth within one year or sooner to prevent the tooth from breaking.

Apicoectomy

In some chronic infection teeth; abscess forms at the root tip that cannot be removed or drain through the crown of the tooth or an infection develops or persists after root canal treatment. The dentist will do a surgical procedure called apicoectomy.  The procedure includes; making a small incision at the gums adjacent to the root tip, remove infected tissue and the tip of the root.  The area is cleaned and sealed with a root- end filling.

Root Amputation

In a multi-rooted tooth, even after a root canal therapy, one or more of the roots become infected or have severe bone loss around the root.  The dentist may surgically remove the infected root (amputate), leaving the serviceable root intact.