I can hardly open my mouth since my visit to the dentist

Q The right side of my jaw occasionally hurts after eating food that needs a lot of chewing, but it hasn’t bothered me that much. But after having a lot of dental work a couple of weeks ago I can hardly open my mouth at all. I’m otherwise well, so it’s not lockjaw, but what can I do about it?

A This sounds like trismus, where the muscles controlling the movements of the jaw become abnormally contracted, which limits the amount you can open your mouth. Though the most well-known cause is tetanus infection (often called lockjaw), thanks to vaccination this is incredibly rare now.

These days, trismus is much more likely to occur after dental work, particularly after wisdom tooth extraction, which can lead to swelling and inflammation in the jaw’s tissues.

Similarly, having work done on several teeth, which may involve injections, can pierce the jaw muscles leaving them bruised and unable to function normally.

Having any abnormality of the jaw joint, such as mild arthritis, can put you more at risk of developing trismus.

It is best treated by trying to exercise the jaw muscles, several times during the day, by putting a finger and thumb on your top and bottom teeth and gently stretching your mouth open.

Applying heat to the side of your face with a warm damp flannel can help too, together with taking anti-inflammatory tablets, such as ibuprofen, if you can swallow them.

Most cases of trismus do resolve in a few weeks, but if the problem persists, then go back to speak to your dentist.

Q I’ve been feeling really tired for ages and my skin has become very dry. Tests at my surgery have shown I have a low T4 level, so I have an underactive thyroid. I’ve been given thyroxine tablets and my doctor says my hormone levels are now in the normal range and that my dose of thyroxine is correct, but shouldn’t I have my T3 level measured as well?

A The main hormone produced by the thyroid gland is thyroxine, which contains four atoms of iodine and is commonly known as T4.

This is converted in the body into triiodothyronine, which contains three atoms of iodine and is known as T3.

It is the T3 that is biologically active and plays a large role in regulating the body’s metabolism.

Small amounts of T3 are also produced by the thyroid gland. The amounts of T4 and T3 produced are regulated by the thyroid stimulating hormone (TSH) produced by the pituitary gland, which is in the base of the brain.

Levels of TSH increase when T4 and T3 levels fall, increasing their production, and when the levels rise above normal, TSH production falls.

The standard blood tests used to check thyroid function are T4 and TSH.

A high TSH level with a low level of T4 indicates an underactive thyroid gland, while a low level of TSH and a high level of T4 suggests an overactive gland.

An underactive thyroid gland is most commonly caused by the body’s own immune system attacking the thyroid cells. Though the trigger for this is not known, it is more common in people with other autoimmune conditions and can run in families.

When the gland is overactive, excess amounts of T3 may be produced and this can lead to a situation where TSH levels are low, but T4 levels are normal.

Therefore measuring both T3 and T4 can be helpful in the diagnosis and treatment of hyperthyroidism.

But when T3 levels are low, either because the gland is producing too little T4 or T3, this is always reflected in the TSH level, which is raised.

Treatment for an underactive thyroid is with thyroxine tablets and the dose can be monitored by assessing the TSH level, which should be in the normal range. Hopefully your energy levels should improve soon, but if not, check with your doctor that there is not another cause for your tiredness.

Q About a fortnight ago I developed a niggle in the left side of my lower back, and after a few days, I began to experience severe pain in my left hip, thigh and knee. The pain was so bad that I was unable to walk and I ended up in hospital for two days.

A series of X-rays, scans and eventually an MRI scan did not show the cause of the problem and I was released with heavy duty painkillers and told to rest and hopefully the situation would improve.

I’ve previously had a hip replacement and been diagnosed with two bulging discs in my back, so I’m surprised the scans were not helpful. I am still in considerable pain and unable to walk without a frame. What should my next course of action be? A Your symptoms do suggest that the cause of the problem is likely to be pressure on the sciatic nerve as it leaves your spine, which can lead to pain not just in your lower back, but also radiating down across your buttock to the outer thigh and knee.

Your medical history of a hip replacement and two bulging discs suggests to me that you are likely to have osteoarthritis, or “wear and tear”, in your lower spine, which is possibly the underlying cause of the problem you have now.

It would be very unusual for an MRI to be normal in someone who has had disc problems in the past and I do think you should query the result you were given while you were an inpatient.

I don’t know where you live, but in many parts of the country GPs can see local hospital results via a linked computer system. If your GP does not have immediate access to the result, they can write to the hospital for a copy and discuss the results with you.

Hopefully this will give more information about the cause of your pain, which in turn will enable them to advise on how it can be managed.

■ If you have a health question for Dr Leonard, email her in confidence at yourhealth@express.co.uk. Dr Leonard regrets she cannot enter into personal correspondence or reply to everyone.