ROEN0310

14 I I clinical report _ crown preparation In a stepwise fashion for an individ- ualcrownpreparation,theprimarycon- cernisachievementofproperanaesthe- sia such that the patient is comfortable in all capacities. Once this is done, the rubberdamisplaced.Iuseasplit-orslit- dam technique. The key to success with this rubber dam technique and crown preparation is the distance at which the holes are placed apart from each other. Generally speaking, holes are punched too close together for this tech- nique.Itisbesttopunchtheholesatadistancefrom each other on the dam that essentially matches the true anatomical distance between the teeth to be isolated. _Next step: Occlusal reduction Oncethetoothhasbeenisolatedandthepatient is confirmed to be comfortable, the next step is the occlusalreduction.Thismakesthetoothshorterand allows better access and visualisation for the axial reduction. If there is an existing restoration in the form of an alloy or composite filling, it is removed and the tooth is reduced to the level of the depth of this restoration. Existing restorations usually pro- vide a good guide to achieving nice occlusal clear- ance without having to verify prior to the next step. Hopefully, I have not diminished the importance of this step, as I know this can make or literally break a final restoration. Completing the occlusal reduction first allows me to warm up and work out any kinks in terms of patientissues,patientpositioning,handpiecewater flow or bur choice etc., before moving to the more complicated axial reduction. On the upper arch, the full-crown preparation is done with a mirror and indirect vision. The OM places us in an ergonomic position for doing this and the rubber dam creates a nice situation for a high volume suction to create an air flow that will keep our mirrors clean(er) of the water spray from the handpiece. On the lower arch,Iconductthree-quartersoftheprocedurewith directvisionandthenfinishcertaincornersthrough indirect vision. Indirect vision on the lower arch is not a common technique but with understanding and desire, it is an easy technique to master. Theaxialsurfacereducedfirstdependsonwhich tooth is being treated. For example, I am right- handed,soonanupperrightfirstmolarIreducethe palatal side first and then move to the interproxi- mals. On that same molar, I break contact on the mesial first, moving from the palatal side, breaking the contact towards the buccal side. This is the easier of the two surfaces to break. First, it is further forward in the mouth and there- fore easier to reach; and, second, it is a shorter con- tact as it is against a premolar. Following the mesial contact break, I continue around the tooth through themesio-buccallineangleontothebuccalsurface. Ithenbreakthedistalcontact,alsomovingfromthe palatal side to buccal direction. The most challeng- ing area to prepare on an upper right first molar is thedisto-buccal(DB)lineangle.Therefore,Iprepare the tooth as far as I can through the distal contact and around the DB line angle. I then complete the buccal reduction and connect the buccal finish line at the DB line angle. Mirror position is critical in achieving a solid finish line on the entire tooth including the DB line roots3_2010 Fig. 9a Fig. 9c Fig. 9b

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