Doctors have discovered 526 miniature teeth in the mouth of a seven-year-old boy in India.

Key points: The miniature teeth inside were found inside a large sac weighing 200 grams removed from the boy's lower jaw

The miniature teeth inside were found inside a large sac weighing 200 grams removed from the boy's lower jaw Doctors said the cause of the condition was unclear, but it could be genetic or from radiation

Doctors said the cause of the condition was unclear, but it could be genetic or from radiation The boy first complained of the swelling four years ago but wouldn't let doctors investigate

Chennai's Saveetha Dental College and Hospital says the boy was brought to the institution complaining of swelling in his jaw.

During surgery, a large sac within his lower jaw containing "multiple hard structures" was removed from his mouth.

The sac, weighing 200 grams, was radiographed, revealing 526 "tooth-like structures" varying in size from 1 millimetre to 15mm.

The hospital said it took five hours to remove all the teeth from the sac, with each structure resembling teeth, with crown covered by enamel and root.

It took up to five hours for doctors to remove the 526 teeth from the sac. ( Saveetha Dental College and Hospital )

Describing the teeth as being "reminiscent of pearls in an oyster", the hospital said in a statement that the rare lesion was known as "compound odontome".

"This is the first ever case to be documented world wide, where so many minute teeth were found in a single individual," the statement read.

"The surgeons' discretion in removing the lesion in total without exploring it on the operating table [akin to opening a bag of worms] avoided a major mishap and saved the patient from being under general anaesthesia for a longer duration and the attendant complications."

According to CNN the surgery took place last month, but doctors needed time to examine the teeth before they could report the findings.

The boy with doctors from Saveetha Dental College and Hospital in Chennai. ( Saveetha Dental College and Hospital )

The boy was released three days after surgery and is expected to make a full recovery, the head of Oral and Maxillofacial Pathology at Saveetha Dental College and Hospital, Dr Prathiba Ramani, told CNN.

Dr Ramani said what caused the condition was unclear, but it could be genetic or the result of environmental factors such as radiation.

The hospital said the boy first complained of the swelling at three years old, but refused to co-operate with investigative procedures by doctors at a nearby hospital.

Doctors told CNN the boy now has a healthy 21 teeth remaining in his mouth.