ROEN0110

20 I I clinical report _ apical microsurgery series _The amount or degree of the root-end bevel (REB)isofutmostimportanceandshouldbeprecisely plannedafterconsideringtheoverallcrown–rootratio, presence of posts or other obstacles, root anatomy, andperiodontalstatusofthetooth.Accordingtopre- vious research, 98% of canal system ramifications occur in the apical 3mm.1 If the bevel is long (tradi- tionally25°to45°),anexcessiveamountofrootstruc- ture would have to be removed to include the apical 3mm on the palatal or lingual part of the root’s apical canalsystem(especiallyinrootswithmultiplecanals). Ifthebeveliscloserto0°,thelingual3mmiseasier toremove;thus,morerootstructurecanbeconserved, improving the crown–root ratio. With a long bevel, there is also an increased risk of completely missing someimportantpalatalorlingualanatomy,especially iftheoperatorisinanymeasureattemptingtobecon- servative in order to preserve the crown–root ratio as far as possible (Fig. 1). The long bevel also creates a spatial problem that is generally impossible for the operatortoovercomewhiletryingtovisualisethetrue long axis of the canal system (Fig. 2); the longer the bevel,thegreaterthetendencyfortheoperatortoleave moreofthepalatalorlingualaspectoftherootintact. As it is difficult to visualise the long axis of the tooth, the resultant retro-preparation is not as likely to be within the long axis of the canal. This concept is extremely important and the primary reason for the occasional, unintentional perforation of the retro- preparationtothelingualorpalatal(Figs.3a&b).An- other important consideration—with a bevel as close to 0° as possible—is that the cavo-surface marginal dimensions of the root-end preparation (REP) will be considerably decreased. Therefore, the restoration willbeeasiertoplaceandhavelesschanceofleakage. The root anatomy is especially important when there are more than two canals in one root. This occurs most commonly in maxillary bicuspids and in the mesial roots of nearly all molars. It has been shownthatasmanyas93%ofthemesio-buccal(MB) rootsofthemaxillaryfirstmolarshaveasecondcanal (MB2).2 However, the operator has to be constantly aware that multiple canals can occur in any root, no matter which tooth is being operated on. If there is an isthmus present, it can usually be seen with the Operating Microscope (OM) if the root has been ade- quately bevelled and stained with methylene blue. The refinement of the bevel is best accomplished with a surgical length 1171 carbide tapered fissure bur(Brassler)ina45°handpiece(SybronEndo;Fig.4). No air exists from the working end of these hand- pieces, which nearly eliminates the possibility of an air emphysema or air embolism beneath the flap. A standardhigh-speedhandpieceshouldneverbeused for the above reason. On occasion, the refinement of the bevel can cause additional bleeding due to an enlargement of the crypt. The operator should ad- dress any crypt management problem due to a newly createdcryptbeforeproceedinganyfurther.Remem- ber that it is of utmost importance to complete one step before proceeding to the next step. roots1_2010 Apical microsurgery— Part IV: The REB and REP Author_ Dr John J. Stropko, USA Fig. 1 Fig. 1_Illustration of the effect that different bevel angles have on root length, including missing potential lingual anatomy.