Case of the Week: How Do You Avoid Undercuts? Tell Us!

[@rh_BOSS]

Stop and think about your preparation design before touching teeth with a bur. If you're preparing teeth for a bridge then choose the direction of insertion beforehand and mark it with axial depth cuts on all the abutment teeth before proceeding with preparation. Place depth cuts on all surfaces and mark the deepest parts with a pencil. Reduce the tooth untill you eliminate all the pencil marks. Once you're done with preparation position a dental mirror so you can see the tooth apically and look at it with one eye closed from a distance of roughly 30cm. If you can see all the margins then you've prepared the tooth without undercuts with roughly 6-8 degree taper. In a case of a bridge check all abutment teeth without changing mirror angulation and eye position.

[@supertemertem1304]

We need a video

[@anithakonreddy4698]

Thanks doctor

[@parikshitgupt3055]

After preparing finish line use safe end bur parallel to long axis or desired path... and use the finish line as a guide around the circumference of your preparation... that will remove the undercut without altering ur finish line...

[@parikshitgupt3055]

Also establish the two planes... cervical and occlusal..

[@sanjayve101]

Instead of using depth cut bur on axial we can use slightly greater diameter round bur on axial surface to create horizontal grooves just like finish line preparation using reverse prep....marking this with pencils and merging tem as usual with safe end tapered fissure bur ensures there is slightly more reduction on axial plane so that there wont be an undercut....

[@pepelepew2142]

looks like the upper is a 3 unit bridge and they grounded it left it off occlusion touching only with the last molar

[@tessysam7202]

Use depth cuts in two planes- axial & occlusal. Use a tapered diamond bur & hold bur parallel to the long axis of the tooth

[@808krisnip]

If a 2 plane reduction is established with depth cuts axially that may limit the amount of undercuts present.

[@abhachhabra2762]

Why we are not reducing the lingual of #20 to remove the undercut. Why only #21( first premolar)?

[@thangnguyen-dq6fd]

I dont think glidewell provide reduction coping or reduction guide.

[@sumarianson]

To avoid undercuts, I just refuse to get in the ring.

[@Xbox12469]

Or if they force you in, just taper out at first opportunity.

[@aamin6933]

Or block the undercuts

[@selfsameday7448]

Simply wrong a starter with heavy gum abrasions with the preps and should not have shoulder margins attempted! It should have been a modified chamfer instead , (or even a knife edge for lower incisors finishing margins ) to avoid cutting into destines of the # 34 & #35. Why compromise the finished crown with block-out techniques in the laboratory? Regarding the paralleling planes, the prepping guide grooves could have been a good guide before starting the depth cuts of which shows no such attempts ,unfortunately for the whole village involved. The dentist should have noticed his troubles when preparing the temps and stop pretending it is going to be okay , unless he/ she/ they glue their two-fingers together for the rest of their life. It costs the laboratory a lot of resources to maintain financially possible to entertain this client. Everybody lost ! Particularly the patient and patient's lost wages of that appointment and subsequently unnecessary time off.