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I 15 clinical report _ crown preparation I roots3_2010 angle. These steps, for me, remain true for most upper right teeth, with difficulties being increased as we move more posteriorly and considering pa- tient limitations in anatomy, patient attitude, tooth anatomy and existing restorations or decay. _Axial reduction The steps for axial reduction on the upper right arch mirror themselves on the upper left arch. On the upper left arch, I initially reduce the buccal and break contact from the buccal to palatal direction. The difficult area to prepare in an upper left tooth is the disto-palatal/lingual line angle. The difficulty varies according to the tooth being treated and/or the patient’s tooth limitations. The lower arch is different to the upper arch in that direct vision can be utilised for most of the preparation. The buccal reduction is initially done on both lower arches and interproximal contact is brokeninabuccaltolingualdirection,startingwith themesialcontact.Oncebothmesialanddistalcon- tacts have been broken, the lingual reduction has been accomplished. For a lower tooth, the disto- lingual line angle tends to be the most difficult area to visualise, so this is the part that is refined using indirect vision. _Tissue management and cord placement Once all occlusal and axial reduction has been accomplished, the next step is tissue management and cord placement. I start with the radiosurgical unit with a #118 tip to create a conservative trough aroundthetooth,mostlyremovingtissuethickness and/orreducinganyvolumeofinflamedtissue.This is a very conservative step under the OM.TheOMallowspreciseandaccurate tissue removal, and increases tactile sense and the steadiness of our hands. A size 00 cord is placed in a haemo- static agent to soak at the start of the procedure. Literature supports that a cord soaked for 15 to 20 minutes in a haemostatic agent works better than any other alternative cord/haemostatic agent combination or method.1 Personal clinical experience and observations find this to be true. With the radiosurgical gingival troughinplace,thecordplacementisasimple,pres- sureless and quick, followed by copious air/water syringe rinsing. In the time that it takes to place the cordandrinsemosthaemorrhagewillbecontrolled, if any. Nowthesharpnessandpositionofthefinishline can be re-evaluated and refined. An ultrasonic unit is used, with the irrigation on, to clean the crown preparation of calculus and/or other debris. Occa- sionally, a BUC-1 endodontic tip (Ultradent), which is about the same size and shape as a 1DT diamond bur, can be used in the ultrasonic unit to refine the crown preparation finish lines. This is done with the irrigation feature turned off on the ultrasonic unit. To sharpen, slightly refine, or minimally move a fin- ish line, I occasionally run the handpiece at a very low speed without water. _Rinsing and drying Once all refinements have been accomplished, the preparation is rinsed and dried and for the first time,theentirepreparationisevaluatedinoneview. Fig. 10a Fig. 10c Fig. 10b