ROEN0310

10 I I clinical report _ crown preparation _Successful crown preparations start at the di- agnosis.Earlydetectionoftheneedforafull-coverage restorative can minimise many difficulties associated withthepreparationofatoothforacrown,obtaining anaccurateimpression,andtheachievementofapre- cisefitting,long-lasting,aestheticrestoration.Proper diagnosis is the all-important first step. _The importance of vision The second most important component is vision. The dental operating microscope (OM) has proven to be valuable in endodontics but it is just as valuable— ormorevaluable—forrestorativeefforts.Highmagni- fication above 4x is necessary to impose/create good finish lines that are easy to impress and temporise. Magnification of 2 to 24x is available with the OM. Management of gingival health and biological width is important to the overall final look of the crown and the cleanability for the patient. A poor finish line and a poorly positioned finish line not only result in poor impressionsandfinalrestorationfit,butalsomakefor poor-fitting provisionals. Ifthefinishlinecannotbefound,onecannotprop- erlytrimandfittheprovisionalrestorationandremove anytemporarycementproperly.Whenpatientsreturn, gingivaltissuescanbeirritated,makingtheplacement of the final restoration challenging. If by chance one doesachieveagoodfit,then,whenthesofttissueheals, thejunctionofthefinalrestorationandthetoothmay bevisible,ruiningtheoverallaesthetics. Figs. 1–10_Before and after photo- graphs of crown preparations. roots3_2010 Crown preparation techniques utilising the operating microscope Author_ Dr Craig Barrington, USA Fig. 1a Fig. 2a Fig. 2b Fig. 1b