The Effect of Delayed Scanning of Photostimulable Phosphor Plates on Inter-proximal Caries Detection

Objectives: The aim of this study was to determine the effect of different scan delays and different kVps on the diagnostic accuracy of inter-proximal caries detection in photostimulable phosphor plates (PSPs).

Materials and Methods: 45 non-cavitated extracted human posterior teeth were radiographed using the DIGORA® PSPs (Soredex Corporation, Helsinki, Finland). The plates were exposed at 60 kVp and 70 kVp were scanned immediately, 10 min, 30 min, 1h, 6 h, 24 h and 48 h after exposure. In between the exposure and the scan period, the plates were stored in light-tight boxes. The true presence of caries was determined by sectioning the teeth mesiodistally. The accuracy was expressed as the area under ROC curve (AZ). The AZs were compared using SPSS version17 software and repeated measurement test. Kappa was used to measure inter and intra observer agreement.

Results: There was no significant difference between caries detection AZs of the images that were scanned immediately and within 30 min after exposure at 60 kVp and 70 kVp (P >0.05). The immediately scanned AZ at 60 kVp was significantly higher than the AZs with 6 h, 24 h and 48 h scan delays (P <0.05). the immediately scanned AZ at 70Kvp was significantly higher than the AZs of 1 h, 6 h, 24 h and 48 h (P <0.05).

Conclusions: PSP scanning should not be delayed higher than 30 min in order to have an accurate proximal caries detection. Longer delays may cause loss of quality of images.