One of your patients, Diane Green, attends your surgery one morning. She has been booked in as an emergency patient because she has recently broken a tooth that is very sensitive not only to bite on but also to temperature. She has been a patient of yours for many years and, although she has had no clinical treatment completed recently, she does have a heavily restored dentition.

When you examined her you found that the palatal cusp of the upper right first molar had fractured sublingually and was being retained in place only by the gingival tissues. The tooth itself was not tender to percussion but it was very sensitive to move the mobile fractured palatal cusp. In addition, the tooth exhibited hypersensitivity when you blew cold air on it.

She sat in the chair but requested to be treated upright because she had recently been involved in a road traffic accident and her back, shoulders and neck were very stiff. She thinks it was in this accident that she broke the tooth.

As the appointment was only relatively short your initial clinical treatment plan was to give her a palatal injection of local anaesthetic, remove the mobile fractured cusp and place a temporary dressing over the exposed dentine. You did discuss with her that a full coverage crown would probably be necessary, but that the treatment that you were about to undertake would give her relief from her symptoms both of discomfort when she bit down on the tooth and of thermal sensitivity. She was quite happy with this treatment plan but, when you asked her to open as wide as she could, so you were able to administer a palatal injection, she said that her jaw was very stiff and would open only about one and a half fingers’ width. On questioning her she said that there was pain in her jaw joint on the left side but also that she felt that her jaw ‘would not go’ as there was a physical obstruction to her opening wide. She did volunteer that her jaw had been like this since the time of the accident. She also said that she had had to go on to soft diet because chewing was painful, not just as a result of the fractured upper molar tooth. She said that it was also difficult to yawn.

When you asked her about the accident, she told you that she was the driver of her own car and she was wearing a seatbelt. She was not aware of striking her head anywhere on the inside of the car but she was hit in a rear-end shunt when she stopped at a roundabout to let traffic pass. She said the impact was severe enough to render her car (the target vehicle) and the other car (the bullet vehicle) impossible to drive. She was aware of her head being ‘whipped back’ to hit the headrest, propelled forward against the seatbelt restraint and then her head forcibly snapping back again to strike the head restraint. She remembers her mouth closing with a sudden severe force and she feels that this is what was responsible for the fractured molar. The accident happened about a week before you saw her. Initially she had gone to her GP because her neck and shoulders were very ‘tense’ and he prescribed a non-steroidal anti-inflammatory agent (ibuprofen). It was 2–3 days later, when her neck symptoms began to plateau and improve slightly, that she became aware of the problems with her jaw.

Examination

Once you had resolved her immediate dental problem, which was difficult for you both because of poor access, you examined the rest of the articulatory system and found that there was a very occasional click from her left TMJ. She was able to open slightly wider after the click but mostly she was only able to open to about 17 mm. When she opened and experienced locking, she showed an obvious lasting deviation to the left side. When her jaw locked she did not click. The click was audible only with the use of a stethoscope. There was tenderness of her jaw muscles (masseter, lateral pterygoid and temporalis). There was only mild tenderness on lateral palpation of the TMJs but there was acute tenderness on intra-auricular palpation of the left TMJ via the external auditory meatus. You confined yourself to examination of her jaw muscles because you felt that examination of the muscles of the cervical spine and the shoulder girdle was outwith your area of expertise.

You tried to examine her occlusion, but, due to her inability to comfortably move her mandible, you felt that the results of a comprehensive occlusal examination would be unreliable. From previous examinations there were no obvious factors of note that you felt could be contributing to her symptoms. She had no signs of bruxism in that there was no ridging of the buccal mucosa/>