Sir, I would like to respond to the letter from G. A. Greenwood Oblique radiographs (BDJ 2009; 206: 221) with the solution used within the dental services of Southampton City PCT when a similar problem was encountered just over a year ago, on converting some clinics to digital radiography.

Southampton City PCT has had a long tradition of using the oblique lateral (bimolar) radiograph for assessing patients, especially small children prior to extractions under general anaesthesia. Conventional tomographic and intraoral techniques are certainly not appropriate for some patients with either severe physical, medical, morphological or learning disabilities of any age.

The oblique lateral radiograph will provide two thirds of the information that is obtained on a standard OPT for the dose equivalent of a pair of bitewing or molar periapical views (depending on sensitivity of receptor) and can be easily taken under sedation or anaesthetic.

The problem was overcome by using an OPT cassette containing a digital plate produced by Kodak Practiceworks. The plate is then easily read by their CR7400 reader which is about the size of a bread bin. The image may be viewed immediately on a computer screen, stored in the digital record for that patient and/or printed in various formats. This system allows great flexibility as it also reads small intraoral plates which are similar in size and thickness to conventional film. At installation the plates will be calibrated to the reader and X-ray source.

The OPT cassette is longer and slightly narrower than the bimolar half-plate but is very user friendly as you can position it easily. Right and left views can be taken on the same plate and there is no need to shield half the plate from radiation scatter to prevent 'fogging'.

The X-ray source is a standard 70Kv intraoral machine. The machine was supplied with a rectangular collimator that is exchanged for a round one for oblique lateral views only. Neither I, nor any other members of staff have managed this view satisfactorily with rectangular collimation.

This new approach to an old technique will therefore require the following equipment: OPT cassette containing a digital plate (re-usable), digital reader linked to a computer, screen and printer if required. This may take up room in an operating theatre or could be sited in an adjacent room.

Regarding printers, the dental service has had better results using a good quality inkjet printer onto matt photographic paper than with a laser printer. You can also print onto acetate if you prefer. Medical grade printers are available but were prohibitively expensive for our service. Radiographs are stored and viewed in the electronic record for the patient and only printed and forwarded if the patient is referred to another service or clinic that cannot access the record.

I hope this may be of some help.