2. Dose, diagnostic reference levels and equipment

Patient dose in dentistry

Intra-oral doses are low compared with medical CT, but they are not zero, and they add up across a lifetime. Children are more radiosensitive. That is why justification is tighter, not why “dental X-rays do not count”.

Diagnostic reference levels (DRLs)

DRLs are investigation levels for typical examinations, not legal dose limits for an individual patient. If your typical bitewing dose sits well above the DRL, investigate technique and equipment — do not ignore it because “we have always used this timer setting”.

Equipment duties (IRR17 and IR(ME)R overlap)

• Critical examination and acceptance testing before clinical use
• Routine performance tests at the intervals your RPA / employer specifies
• Take a machine out of use if tests fail or the warning signals do not work
• Use the correct rectangular collimator and check it is actually fitted

Digital systems still need optimisation: over-exposure can be hidden by software. Watch exposure indicators, not only how pretty the screen looks.