Nekton

A Mouthful of Medicine.

The mouth is an important part of our anatomy when we dive for it is the beginning of our airway and holds the regulator, our air supply. Any problems in the mouth can have disastrous consequences, even life-threatening although the commonest problem, tooth squeeze, is usually only an inconvenience.

I personally learnt about tooth squeeze when I was flying to the UK. As we landed in Singapore, I started to feel a toothache in one of my back molar teeth. By the time I was in the transit lounge it had become quite intolerable and I needed some painkillers. Once we were en route to London and cruising at 35,000 feet the pain subsided, only to return after our final descent to Heathrow. Again the pain was severe and the next day, when I was able to find a dentist with an appointment, an X-ray showed a fine crack in the large filling in the tooth which connected to a tiny caries beneath the filling. The filling was duly replaced and my return trip to Australia was pain-free.

This was an easy lesson. With diving, it can be far more dramatic for the pressure changes we experience are far more rapid than a plane's cabin depressurisation.

Last month my buddy, Ben, was ascending with me from a deep dive in the Yasawa Islands in Fiji. As he ascended to 10 metres he suddenly grasped the right hand side of his face and started to squirm. I had no idea what had happened but swam dutifully to his side to offer assistance. He just held on to me as we ascended and surfaced slowly, though without our usual safety stop. When safely back on board the boat, he described the sudden agonising pain that seemed to hit him on the face as he ascended. He did not realise what had caused it until he took the regulator out of his mouth and felt a large hole in one of his lower molars. The filling in the tooth had actually exploded in his mouth from the high pressure that had built up during the deep dive but could not be quickly released.

Tooth squeeze or "dental barotrauma" occurs when an air-containing cavity, either behind a filling or caused by caries within the tooth, is at a different pressure from the air in the mouth. The pressure difference may cause toothache by distortion of local pain endings. Alternatively it can create an implosion or explosion of any tooth enamel or filling overlying the cavity.

Ben was quick to make an appointment for a full dental check when he was back home, and I suggest that anyone who is diving should have regular dental check-ups too.

Dental extractions usually heal quickly but diving too early can have odd consequences. One very keen diver dived the day after he had his front tooth out. He had taken several pain killers to numb the gum but late into his dive he felt his face begin to swell. When he left the water the lower part of the left side of his face was swollen and crackled when touch. Somehow the compressed air in the mouth had entered into the gum through the raw and open tooth socket and tracked through the tissues of his face. As he ascended, the air in the tissues expanded to form bigger bubbles that could not escape the way it entered. Although he looked hideous, the swelling slowly subsided as the air was absorbed and he was left looking quite normal but wiser.

Diving can also be hazardous to crowns. The retention of crowns can be reduced by up to 66% by repeated diving. The main factor that influences the crown is the type of resin cement used to glue it on. The best type was resin cement which was superior to zinc phosphate and glass ionomer cements. So if you are having any crown work done be sure to check with your dentist what the cement they are using.

I have seen three patients who suffered trauma in the mouth from an ill-fitting regulator that knocked the crown clean off (whether it was already loose from an inferior cement I do not know). The main danger is that the dislodged crown could be inhaled and cause a respiratory blockage. Luckily this did not happen. But it did happen to an unfortunate diver who had a partial dental plate in his mouth. Somehow the plate became loose and was inhaled to become jammed in the very back of his throat causing instant distress and gagging. The diver panicked and shot to the surface where he was able to cough it free. Luckily he was in only five meters of water so was no in danger of decompression illness, but he was fortunate that he did not suffered a burst lung and air embolism from his rapid ascent. Another unfortunate diver had a partial dental plate loose in is mouth and managed to swallow it rather that inhale it. Obviously he would have felt its bite at a later date!

The lesson is to ensure that all dental plates are well-fitting and that partial plates are clasped and cannot become loose in the mouth.

The modern fashion of tongue bolts has raised many questions about their safety during diving so I have asked many divers who have dived with them in place and they have never encountered any problem. All I can suggest is that the bolt is checked to be tightly fixed so there is no likelihood of it becoming freed during the dive.

Recently, I have used a moulded, customised regulator mouthpiece on my own regulator and found it to be far more comfortable than the standard fitted one. The moulded mouthpiece includes the back molars in the bite whilst the standard one only involves the front teeth. In the past, they had to be made professionally so were timely and costly to fit. Now they can be bought off the shelf and easily moulded to your teeth by immersing them in hot water and biting down on them. After the first moulding they hold their shape and will let your mouth hold and stabilise the regulator mouthpiece with no strain on your jaw. I recommend them to all divers but especially to anyone who grinds their teeth or has any jaw dysfunction.

So appreciate your mouth when you next dive, treat it to a customised mouthpiece, secure all appliances, and be sure to have a regular dental check so you do not have a sudden explosive surprise.

(This article first appeared in the October-December 2004 issue of 'Alert Diver Magazine' and is reproduced with kind permission of DAN SEAP.)