How many roots and root canals does a tooth have?

Number of roots and root canals in teeth.

How many roots and root canals do teeth have?

Why are these numbers important to know?

When endodontic therapy is performed, the number of roots and root canals being treated is an important factor because so many issues associated with this procedure are influenced by the total number of both.

For example, the level of difficulty of the procedure, how long or how many visits it will take What’s common? and even how much your treatment will cost Endodontic fees by tooth type. are all influenced greatly by the number of roots and canals.

Variation is commonplace and must be expected.

What’s usually found?

Our chart below lists what your dentist generally expects to find when treating different kinds of teeth (molars, premolars [bicuspids], canines [cuspids], and incisors). But discovering variation is a key theme when it comes to these numbers.

How many roots and canals your dentist actually finds, and therefore must ultimately treat when performing your endodontic therapy, can vary, even substantially, from what is considered “normal.”

▲ Section references – Torabinejad

So, how many roots and root canals does my tooth have?

As our chart below shows, these numbers vary according to the type of tooth being considered. And even then, some tooth types have common variations. But when this question is asked in its most basic, commonplace form, here are some answers.

Number of roots –

• How many roots does an incisor have (upper or lower)? – One.
• How many roots does a canine have (upper or lower)? – One.
• How many roots does an upper premolar have? – One or two.
• How many roots does a lower premolar have? – One.
• How many roots does an upper molar have? – Three.
• How many roots does a lower molar have? – Two.

Number of root canals –

• How many root canals does an incisor have (upper or lower)? – One.
• How many root canals does a canine have (upper or lower)? – One.
• How many root canals does an upper premolar have? – Two.
• How many root canals does a lower premolar have? – One.
• How many root canals does an upper molar have? – Three or more.
• How many root canals does a lower molar have? – Three or more.

Here’s the same information in tabular form.

Table – Usual root and root canal expectations for Molars, Premolars, Canines, and Incisors.

▲ Section references – Ingle

Your dentist must assume that every tooth displays variation in the number of canals, and possibly roots too.

As stated above, while the numbers shown in our chart are the common and usual ones for each kind of tooth, the bottom line is that when performing any one tooth’s endodontic work the dentist must look for what’s expected, and then anticipate that they’ll find more. This definitely goes for the total number of root canals in each root and possibly even the total number of roots the tooth has too.

This is vital because a tooth’s root canal therapy won’t be successful unless the dentist treats the tooth’s entire root canal system. Any portion that’s overlooked Missed canals., and therefore is not treated, can be expected to result in treatment failure.

Forms of anatomical variation your dentist is likely to discover.

• Additional tooth roots – While it’s always possible that your tooth has a greater number of roots than most other teeth of its type, as compared to variations in the number of root canals, this type of deviation is less common.

  A primary exception to this rule would be upper premolars (bicuspids) where statistically speaking the presence of either just one or two roots runs practically neck and neck. (Al-Ghananeem, Chaparro)

• Fused tooth roots – More common than finding extra roots is the issue of multi-rooted teeth (premolars, molars) having fused roots.

  This issue on its own doesn’t necessarily increase the difficulty of a root canal case. But it’s not uncommon that teeth with fused roots display wider variation in their number of root canals and the complexity of their configuration, which would tend to do so. (Ahmad)

• Additional root canals – Discovering a tooth that has a greater number of canals than what’s listed in our table above isn’t uncommon at all.

  Certain types of teeth (lower incisors, upper premolars, molars) and even specific tooth roots (mesiobuccal roots of upper first molars, distal roots of lower 1st molars) are well known for having the potential to have additional canals.

▲ Section references – Al-Ghananeem, Chaparro, Ahmad

How does a dentist identify and locate all of a tooth’s roots and root canals?

If variation in the number of roots and canals is so common, and so important for the dentist performing the tooth’s endodontic treatment to know about, how do they discover them all?

The three primary methods dentists use are:

• Taking radiographs (x-rays).
• Visual inspection.
• Tactile discovery.

a) Taking x-rays.

Long before your dentist ever begins performing your tooth’s actual root canal work, they’ll have taken dental x-rays. And these pictures can give them a substantial amount of information about how many roots and root canals your tooth has.

1) Two-dimensional pictures.

The most common type of dental x-ray general dentists take is like the one shown in our graphic. It’s a flat (two-dimensional) picture of your three-dimensional tooth.

What your dentist can learn from this type of film.

An x-ray like the one shown below can reveal a lot of information. Here are some of the details a dentist would notice: (The tooth in our picture is a lower first molar.)

• Running down the length of root “B” you can see the clear outline of two root canals.

  Actually, that’s to be expected. This root (the mesial root) of a lower 1st molar usually does have two canals.

• In contrast to root “B,” when you look at root “A” you just see one canal. And actually, for this root (the distal root) that’s the most common form.
• We’ll also point out that from this picture it’s clear that this tooth has two distinct roots (as opposed to them being fused together), which once again is the most common form for this type of tooth.

So, just from the simple act of taking a radiograph, and long before they have taken any instruments to your tooth at all, it’s possible for your dentist to have quite a bit of information about it. Both in terms of how many roots and canals your tooth has. And with this particular tooth in our example, so far everything seems usual about it.

What your dentist can’t always tell from a two-dimensional x-ray.

As informative as taking conventional dental x-rays can be, there can be times when what they show can be difficult to interpret. To give you some insight into what your dentist must deal with, here are some unclear points about the same radiograph shown above.

Do root “B”‘s canals merge?

It’s most likely that due to the angle at which this film was taken, one canal simply overlaps the other (the two are superimposed) thus giving the appearance of just one.

Why dentists take multiple x-rays.

Actually, your dentist has a technique they can use that can help to clarify things. That’s simply taking an additional x-ray(s) from a slightly different angle (like plus or minus 20 degrees) and comparing them.

When that’s done, what actually exists is more likely to be revealed. And for this reason, it’s commonplace and should be expected that your dentist will take multiple (two or more) pre-operative x-rays of your tooth.

Does root “A” have one or two canals?

This same type of inconclusiveness exists with root “A”. It looks like it just has a single canal but it’s not uncommon for a first molar’s distal root to have two. (About one-third of cases have two. Ingle – linked above.)

Once again, the angle at which this picture was taken may have resulted in superimposing the two canals. And also just like above, taking additional radiographs from different angles may help to clarify what actually exists.

2) Three-dimensional radiographs.

Over the past decade, the use of Cone Beam Computed Tomography (CBCT) 3D imaging. has become more and more common in dentistry. And the view that it gives can answer many uncertainties about a tooth’s roots and canals, including the types of difficulties discussed above.

Due to the expense of these units, however, most general practitioners don’t have CBCT capability. Its use with root canal work is typically limited to the offices of root canal specialists Endodontists.

b) Searching for root canals via visual inspection.

Once your dentist has begun the process of performing your tooth’s endodontic therapy, visual inspection is a vitally important way by which they determine how many root canals it has.

The pulpal floor of a lower first molar.

• What you see is the floor of the tooth’s pulp chamber (its “pulpal floor”).
• The openings you see (the two faint lines inside the tooth) are literally the openings (orifices) of each of the tooth’s root canals where they connect with the tooth’s pulp chamber.

• Just like described above, the mesial root (which lies underneath the portion of the tooth at the top of our picture) appears to have two separate canals. (You can see the two small round openings at each end of the faint dark line).
• And just like above but in contrast to the mesial root, the distal root (which lies underneath the portion of the tooth at the bottom of our picture) seems to have just one broad slit-like canal.

  The dentist will need to investigate further to confirm that this is in fact just a single canal.

An endodontist using an operating microscope.

Inspection via microscope.

An example from research.

Initially, 73% of teeth were identified as having a second canal in this root. However, with the aid of a microscope, it was determined that a second canal was actually present in 93% of cases.

▲ Section references – Stropko, Hoen

c) Tactile discovery of root canals during your procedure.

Working a root canal file inside a tooth.

And the paths these files tend to follow as they are worked up and down inside the tooth’s root canal system give the dentist a good idea of its overall anatomy.

Configurations your dentist may discover.

It’s possible for a dentist to determine a number of features about a tooth’s canal system as they work.

• The canal may be branched. – A single canal sometimes divides into two separate ones.

  With our distal root example above, that was the concern. And as the dentist performs the tooth’s work, they would need to investigate whether what looks like the opening to a single canal is in fact that. Or if instead, it branches into two separate ones lower on down in the root.

• Two canals may coalesce into one. – We mentioned the possibility of this configuration in our mesial root example above. It’s possible that two obviously separate canals at the tooth’s pulpal floor combine to form a single one lower on down in the root.

  Now with the kind of tooth in our example above that’s unlikely. But the dentist must confirm this fact as they perform their work.

• The issue of how many roots a tooth has does vary for some kinds of teeth. But with others, variation is so rare that it’s practically a nonissue.
• In comparison, how many root canals a tooth has tends to vary much more frequently. This variation will be more common with specific kinds of teeth and specific tooth roots on certain types of teeth.
• And because discovering and treating all canals is so vitally important for the success of a tooth’s endodontic work, dentists place great emphasis on searching for and identifying them using the methods described on this page.