The Truth About Cracked Teeth and Crowns
Cracked teeth are so common as to be practically ubiquitous. A tooth crack is not a disease but is instead a risk factor for further problems. Fractures tend to grow and change over time; therefore it is very important for dentists to screen for cracks and catch them early. (1) Most cracked teeth exhibit no symptoms. Symptoms when they occur include an uncomfortable sensation or pain from a tooth that occurs while chewing hard foods and which ceases when the pressure is withdrawn. (2) Worsening pain can be a sign that the tooth is infected.
Cracked teeth are generally diagnosed by visual observation, ideally using a microscope. (3) Indeed, many are difficult to spot without the aid of a microscope, so I am happy to report that I am one of a few practitioners who use a microscope, therefore, I am able to spot cracks much easier than most. Read my post on the benefits of using microscopes in dentistry here.
They have been classified into 5 distinct groups, generally from least to most severe: craze lines; fractured cusp; cracked tooth; split tooth; vertical root fractures. (4) Craze lines are visible fractures that only involve enamel. However, it is not always possible to determine that a visible fracture is limited to enamel. (5) Fractured cusps and cracked teeth can be treated provided there is adequate remaining tooth structure to “fix”. Sometimes, however, a tooth can break too far under the gums to be saved. Split teeth (furcation fractures) and vertical root fractures most often cannot be treated, and the tooth must almost always be removed and replaced.
Factors that cause tooth fractures and cracks vary, but are affected by the shape of the teeth, the position of the teeth, the diet, habits like grinding and gum chewing, age, history of previous fractures and cracks, and the presence of fillings. Anytime a tooth is treated with a filling, the possibility of fracture increases because of reduced supporting tooth structure and the wedging effect of fillings. The larger the filling is, the greater the chance of the tooth fracturing. (6) However there is one study that showed the prevalence of cracked tooth was highest in non-filled teeth, in upper back teeth, and in those over 40 years of age. (7) Clinical observation suggests that fractured cusps and fractured teeth occur more frequently among people who clench and grind their teeth, gum chewers, and ice chewers. (8) It appears that the shape and position of a cusp (the pointy parts of teeth) can contribute to fracture potential in that nonfunctional cusps appear to fracture with a higher frequency. Nonfunctional cusps are not required to do as much work have been shown to differ from functional (working) cusps in form, which may lead to the higher fracture potential. (9) Finally, the resistance to a crack spreading decreases with both age due to dehydration of tooth structures. (10)
A cracked tooth can act as a pathway for bacteria that may induce inflammation or disease. The prognosis of cracked tooth that is not treated will progressively deteriorate and may evolve into a split tooth or result in severe periodontal defects. Eventually the tooth may be lost. Therefore, early diagnosis and treatment are essential in saving these teeth. The margins of fillings on cracked teeth should be screened for decay, and the fillings should be removed to permit removal of the decay, direct visualization of the crack by microscope, and assessment of the tooth's structural integrity. (11) A less experienced dentist may be tempted to drill out a crack line until the dentist has reached healthy tooth structure, and then place a filling, however, this will not prevent the original causes of the crack from causing further crack propagation. (12)
A 2007 study showed If a crack associated with transient pain is identified and a crown is placed, from a restorative standpoint, the treatment was successful for all teeth because symptoms resolved and 100% of the teeth were retained. (13) A crown, which is a very durable porcelain that permanently covers the tooth, prevents flexure of weakened tooth structures above the gum and the wedging effect of a filling. It displaces the force on the tooth from multiple possible areas to only the horizontal cross section of the tooth. (14) To illustrate, picture an old-fashioned wooden barrel. If over-filled, the staves would want to spread outward and the barrel would split. The rings around the barrel help to displace the forces and hold the wooden staves together, thus preserving the integrity of the barrel.
A woman was in my office today a piece fractured off of her lower back tooth with a large filling in it that I had diagnosed at her last visit and recommended a crown. She had already split an unfilled tooth several years ago that needed an extraction. She has a history of clenching and grinding her teeth. The shape and overlap of her teeth make her more prone to cracks and breakage. She also had a newly fractured tooth on her lower right. All of this was an indication that a crown would have the best prognosis by far. She did not want to commit to the crown and only wanted a filling. Since she was in no pain, did not have decay, and was not packing food in the area of the break, there was no concern there. The problem was the crack which in her situation was likely to lead to worsening problems. I informed her that a filling would not strengthen the tooth, and possibly weaken it. We decided that she would derive zero benefit from a filling and therefore did nothing. I wish her luck, with her history, bite, grinding habits etc, she will need it.
The following table summarizes the treatment options for the various types of fractures and their related symptoms.
Chart Courtesy of: Mamoun JS, Napoletano D. Cracked tooth diagnosis and treatment: An alternative paradigm. Eur J Dent. 2015;9(2):293–303. doi:10.4103/1305-7456.156840
As you can see, it is quite complicated and not meant to be used for self-diagnosis. If you suspect you have a fracture, make an appointment with your dentist. If you think you don’t have a fracture, make an appointment with your dentist if it has been over 6 months since your last exam!