Abfraction causes or NCCL causes
The cause of an abfraction, more properly known as non-carious cervical lesion (NCCL), is debatable. Abfraction by definition is related to occlusal stress. Although many use the terms interchangeably, I will use NCCL to describe the lesions except where occlusal stress is believed or reported to be the cause. NCCLs are probably multi-factorial. They are very common and yet we are not really sure why they occur, although we have plenty of good theories.
The abfraction definition found online, Abfraction is a theoretical concept explaining a loss of tooth structure not caused by tooth decay (non-carious cervical lesions), is arguably not accurate as it is classifying all NCCLs as abfraction lesions.
Major competing theories to NCCL and abfraction causes
- Toothbrush and toothpaste abrasion
- Chemical erosion (both internal and external)
- Tooth flexure due to occlusal stress = abfraction
What do we know about abfractions?
- There is an increase in prevalence with age. Aubry, Wood 2008 J Dent
- They occur more commonly in females. Aubry
- They appear to be a modern condition. Aubry, Kaidonis, Aaron
- They are more common on premolars. Aubry
- More common with acidic diets Ritter
- They are more pronounced on incisors, canines, and premolars Kitchin JDR 1941
They are more prevalent in the maxilla Kitchin
Why do we not find NCCLs on pre-modern human teeth?
A French study looked at 259 pre-modern skeletons and didn’t find one abfraction. Aubry 2003 American Journal of Physical Anthropology Another study states, “non-carious cervical lesions to date have not been observed within hunter-gatherer populations and therefore should be viewed as ‘modern-day’ pathology”. Kaidonis 2008 Clinical Oral Investigations
Urzúa 2015 Int. J. Odontostomat puts forth an interesting theory from viewing that 67 adults lacked any abfraction lesions in per-Colombus Chilean skulls. I cover this more under occlusion.
Ritter claims they are not only a pre modern condition but found only one skeleton with abfractions in what I consider someone that could not have been using modern cleaning techniques. Ritter 2009 J Esthetic Rest Dent I don’t think late 19th century skeletons from Mexico should be considered because it is very possible that they had access and used toothbrushes with some sort of cleaning paste. By the late 19th century they were in use from N. America down to Brazil.
“The 200,000-plus artifacts uncovered at the Leopoldina site so far include stoneware and glass bottles, some still filled with liquid; household ceramics; pipes; coins; remains of a leather shoe; and 15 bone and ivory toothbrushes, one inscribed in French with the words “His Majesty, the Emperor of Brazil.” It is believed to have belonged to Dom Pedro II — the country’s last monarch, ousted in a coup in 1889 — or another member of the royal family.”
I have posted what the lesion from the 650-950 A.D. looks like. Personally, I disagree that this is an abfraction lesion or even a NCCL. What are your thoughts?
Why do we not find NCCLs in any other species teeth?
If NCCL was do only or even primarily from occlusion, one would think that they would exist in other animals as well. However, no such lesions have ever been found in any animal to my knowledge. There is a study that claimed to have found abfractions in mammoth teeth but viewing the photo, I’m not sure how that is considered an abfraction lesion similar to a human NCCL. Krzemińska 2008
Another study often sited Burke 2000 claims that feline odontoclastic resorptive lesions are similar. If you click the previous link that takes you to a google image search you will see many examples of feline odontoclastic resorptive lesions. To my eyes those look NOTHING like NCCL. Not even close! They look a lot like external resorption. The cause of feline odontoclastic resorptive lesions in wikipedia seem similar to external resorption. The fact the occlusion camp sites this article as evidence makes me doubt their credibility.
It would be interesting to see what the abfractions that Messer claims to have found actually look like. The abfractions are only on the mesial and distal, which immediately makes me believe they are likely something else. This appears to just be a table presentation and not published research. Messer 2002 Cervical Dentin Loss in Bovine Incisors – an Abfraction Lesion?
Evidence supporting toothbrush toothpaste abrasion for NCCL
We can form lesions that visually appear identical to clinical NCCLs from simulated tooth brushing with toothpaste. Furthermore, lesions that appear the same as cupping and pitting are also created by toothpaste and toothbrush. Dzakovich JPD 2008 and 2013 The higher the toothpaste RDA value, the more abrasion the toothpaste causes.
We see these cupping and pitting lesions in pre-modern humans and we believe the cause is abrasion. Things in the diet, in particular sand, is the abrasive substance in the case below. Kaidonis
Some argue that they have seen lesions that toothbrush and toothpaste would be difficult or impossible to create. Many say that lesions under gum tissue are impossible, but actually Dzakovich shows it is possible to create these under simulated gum tissue. Furthermore, gum tissue could grow over the lesion after it’s formation. However, there are lesions (more often on the lingual) that do truly seem impossible. These lesions lend themselves to the high probability of other theories having some impact.
Evidence supporting erosion for NCCL
Humans diets have drastically changed with modernization. We went from a non-acidic, course, fibrous diet to an acidic and soft diet. The diet changes have resulted in a drastic increase of erosion that was either non-existent or masked by massive abrasion in pre-modern humans. Kaidonis
Evidence supporting occlusal stress for NCCL
The fact that pre-modern humans didn’t have abfractions does not totally discount occlusal stress as Aaron GM (2004) argues. There may be some releasing of stress that was provided by pre-modern human diet that resulted in the abrasion we so commonly see on their skeletal remains. Perhaps the occlusal surface wearing away bore the brunt of occlusal stress in some manner. Perhaps the skeletal remains are all of individuals that were too young, since we know abfractions have a strong correlation with age. Many of the studies supporting occlusal stress are FEA (functional element analysis)
A strong correlation between occlusal overload and abfractions was found in a group of 111 volunteers. Brandini 2012 JPD Nov WEar facets and NCCLs were foudn to be related in 70 patients. Pegoraro JADA 2005 Yet, on 299 casts, Estafan JPD 2005 found nearly the opposite – there was no association between tooth wear and non-carious cervical lesions.
It has been postulated that the severe tooth wear in pre-historical crowns and the loss of crown height reduces cervical stress and development of NCCLs in archaeological populations. Urzúa This theory is supported in some manner by Benazzi 2013. Also Kieser 2001 Stress concentration at the CEJ related well to the location of NCCLs. The crown-root morphology may have an influence on the initial location of non-carious cervical lesions. Palamara 2006 J Dent
Yet we see NCCLs in modern individuals with heavy wear. So how wear can act to protect the pre-modern humans but doesn’t protect modern humans seems strange.
Multi-factorial support for NCCL formation
Seems the most likely to me. Grippo 2012, Wood, and Litonjua JADA 2003 all found multi-factorial causes to be most likely. For the most part they reject the broad use of the term abfraction for NCCL as many are unlikely to be due to stress/occlusal related issues.
Modern humans that have never brushed their teeth do have NCCLs
A population of African rural leprosy patients that have never brushed or used the more more common stick in their area known as a miswak have NCCLs. Unlike the above photo of a Mexican male the photos of the teeth of these individuals have very evident NCCLs. This study lends support to the multifactorial theory of a cause as the individuals have acidic diets and grind their teeth. Faye 2006 Quintessence Int
Jiang 2008 found frequency of toothbrushing, bruxism, age, location, income all had an impact on the number of NCCL.
Should we treat the NCCL?
Wood’s literature review concludes that the value of restoring these lesions is unclear. Furthermore, he states that evidence for occlusal adjustment to increase the retention of restorations we place to restore lesions or to halt lesion progression does not exist.
Others Levitch J Dent 1994
Ultimately, we do not know why NCCLs form. So like is seen in so many research articles and is seen in the lit review done by Senna 2012 “additional studies are warranted.”