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MedicalResearch.com Editor’s Note: Dr. Christopher Perry, Senior author of the paper, presents his thoughts on this topic below:

MedicalResearch.com Interview with:
Christopher F. L. Perry, MBBS
Princess Alexandra Hospital, Brisbane, Queensland, Australia

Medical Research: What is the background for this study? What are the main findings?

Dr. Christopher Perry: This study was prompted me, the senior author, noting a lot of patients, especially female patients, presenting with cancer next to rough dental surfaces without a history of ever smoking. I am married to a dentist and have a fair bit of knowledge of dental issues. I started asking these patients whether their teeth had rubbed for very long and usually got a positive response in the non-smoking oral cavity patients. I then noticed that older non-smoking people tend to get cancers under dentures especially if those dentures hadn’t been re-lined or replaced lately. It appeared that chronic irritation could indeed be a carcinogen and more significant than generally realised despite being one of the five traditional “Ss” of head and neck carcinogenesis .

A decade ago I was talking to a pathologist who had written a recent paper then on cancer of the skin of the face occurring where glasses rub on the bridge on the nose and above and in front of the ears over the zygomatic arches. The second author of that study was Dr David Weedon who is the editor of one of the standard textbooks of skin pathology.

My interest was then peaked with a 37 year old accountant who was referred to me by a 45 year old emergency physician close to the Christmas holidays about nine years ago. This emergency physician rang me up as I was covering another head and neck surgeon who had previously looked after him, when he himself had a mouth cancer. When he suggested to me this 37 year old accountant who was a non-smoker and had a cancer on his tongue, I said “ask him whether he had a tooth that rubbed on that site”. He went back and spoke to the accountant and the accountant said yes, he had a sharp dental cusp. The 45 year old doctor then said to me that he previously had an oral cavity cancer which is why he recognised this cancer on the tongue of this 37 year old accountant. The 45 year old physician said that he always had a rubbing tooth at the site where he later developed a cancer. That spurred me to start looking at this seriously and talking to my colleagues at the Head and Neck Clinic at the Princess Alexandra Hospital.

I have taken photographs of a lot of mouth cancers close to rough teeth. On a number of these patients there are sharp medial cusps on molar teeth, usually the sixth molar tooth which is the main tooth medialized as the seventh or eighth teeth come down in later childhood. In other patients the teeth have been turned inwards so that the crown of the tooth actually rubs on the side of the tongue. Other patients have large medial amalgam fillings and amalgam fillings are extremely rough.

I have had a number of people who have presented to me with pre-malignant changes on their tongue and by simply referring them to a dentist and having appropriate dental care these pre-malignant significant dysplastic lesions have disappeared over the space of two or three weeks. One patient had a large amalgam filling and another two or three had sharp cusps. Another patient had ground down posterior teeth medially which were quite sharp on the tongue much like the shape of an axe head.

I have had a number of patients with cancer of the buccal mucosa where teeth have turned out. I have photographs of a couple of those dental shapes and the cancer of the buccal mucosa. I have also got a medical receptionist from the Princess Alexandra Hospital who was a lifelong non-smoker and had a story of continually biting her cheeks as a nervous habit much of her adult life and she developed a cancer on the buccal surface right in the position of where chronic tooth trauma to the buccal surface occurred when she was nervous.

Medical Research: What are the main findings in our study?

Dr. Christopher Perry: The main findings of our study are that in Queensland in the ten year period 2001-2011 non-smoking women developed oropharyngeal cancer in only twelve cases yet fifty three women developed cancer in the mouth, two thirds of them on the edge of the tongue where teeth rub. When patients had cancer on the floor of the mouth and the alveolar arch and they were non-smokers, they were older than the patients who had rough teeth still present, suggesting they had dentures rubbing on the alveolar arch and the floor of mouth.

There is much written about HPV associated oropharyngeal cancers in the non-smoking population. So far HPV cancers affecting men in Queensland are normally occurring in ex-smokers or current smokers although there are a reasonable number of cancers occurring in lifelong non-smoking men. There are almost none occurring in lifetime non-smoking women. Obviously HPV induced cancer is not quite such a simple venereal disease as is sometimes suggested. This is backed up the fact that HPV associated oropharyngeal cancer is relatively uncommon in the Afro-American population. It seems to be a Caucasian male problem. However cancer of the mouth in lifelong non-smoking females is a significant issue. Our state of Queensland, which drains the medical population of 5.5M people, has about thirty oral cavity cancers occurring per year in non-smokers with almost two thirds occurring in women. Usually head and neck mucosal cancers are two to four times more common in men. Non-smoking mouth cancers are the only head and neck cancers occurring more commonly in women.

Medical Research: What should clinicians and patients take away from your report?

Dr. Christopher Perry: Dentists and head and neck surgeons should be aware that chronic irritation can cause cancer in the mouth. Asbestos is a known carcinogen and it is widely regarded that its carcinogenesis is due to chronic irritation and trauma from sharp particles on the pleural surfaces of the lung which constantly move – much like the tongue does. When patients have pre-malignant conditions of their mouth they need their teeth attended to. That maybe having to lateralise the tooth by changing the whole tooth crown, smoothing a sharp single cusp or changing a rough medial amalgam filling to a smooth surfaced crown or ceramic inlay. Dentists may need to change the position of the crown of the tooth by lateralising the crown. Porcelain is smoother than gold and would be a better treatment option. It may mean simply rounding off the tooth cusp. If that rounding of the cusp is not adequate, that patient may need to spend the appropriate money to get a crown to lateralise the tooth. Extraction of the offending tooth is also an option but you cannot leave an empty tooth space otherwise the tongue may be traumatized by running past the gap, hitting the tooth in front and the tooth behind. An implant, bridge or partial denture needs to replace it. Pre-malignant changes may only reverse in some patients who need to undergo moderately expensive dental care but that is of course a lot better than developing a full oral cavity cancer which has a significant mortality rate and also significantly costs the community.

Hopefully dentists will be able to encourage people to get their sharp teeth fixed up. Hopefully dentists, ENT surgeons and general practitioners can recognise that a sore edge of tongue is nearly always associated with a rough tooth and that needs to be taken seriously and corrected appropriately. I hope clinicians take away from the study that women can get oral cavity cancer in relatively large numbers, that head and neck cancer is not purely a disease of smokers or people with a past history of too many oro-genital sexual contacts. Certainly for women it appears that chronic dental trauma is a much more important carcinogen than HPV and its suggested association with a multi-partner oro-genital sexual history.

What recommendations do you have for future research as a result of this study?

Dr. Christopher Perry: We have the dental records of all eighty seven people with non-smoking associated mouth cancers. We will see what we can obtain from that. We are currently doing a prospective study on non-smoking oral cavity cancers to see whether we can find a HPV genetic material within the cancers themselves. We are looking at both P16 positive and P16 negative tumours. Obviously people could say that these tumours are occurring in sites of trauma and HPV is known to implant in sites of trauma. We are taking this HPV co-carcinogenesis seriously but I believe our studies will show that HPV has nothing to do with these non-smoking mouth cancers even those which are P16 positive.

Non- smoking women are 4 times more likely to get a cancer of their mouth from rubbing teeth that an oropharyngeal cancer of tonsil or tongue base from oro-genital sex.

Citaton:

Perry BJ, Zammit AP, Lewandowski AW, et al. Sites of Origin of Oral Cavity Cancer in Nonsmokers vs Smokers: Possible Evidence of Dental Trauma Carcinogenesis and Its Importance Compared With Human Papillomavirus. JAMA Otolaryngol Head Neck Surg. Published online November 06, 2014. doi:10.1001/jamaoto.2014.2620.