PROFILE ENHANCEMENT AND CEPHALOMETRIC LANDMARK IDENTIFICATION

The reproducibility of two soft tissue landmarks (SN, V) and two anter ior bony landmarks (A, ANS) was determined by three observers for thre e cephalometric techniques. The three techniques were aimed at soft ti ssue profile enhancement either by standard exposure control (techniqu e 1), a hand-held metal shield covering the profile (technique 2), or a brass wedge in the collimator (technique 3). For each technique, the sample was restricted to 20 subjects with a skeletal convexity greate r than +4 mm. The four landmarks were identified three times with 7-da y intervals between readings. The figure-of-merit (or mean radius) met hod was used to assess the probability of ''hitting'' a target (landma rk) area. The mean radius from the sample mean point of impact (MPI) r anged from 0.585 mm to 1.758 mm. For a specific landmark, the differen ce was never greater than 0.5 mm when grouped by observer and techniqu e. No technique excelled in overall consistency for the identification of anterior bony and soft tissue landmarks. Techniques 1 and 3 produc ed the most consistent identification of points ANS and SN, but with n o significant difference between the two techniques. Interacting facto rs prevented any recommendation regarding a preferential technique for the identification of points A and V. There is statistically no reaso n to recommend the use of a handheld, metal profile shield for more co nsistent landmark identification.