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Message: [QUOTE="Dodo97, post: 125896, member: 7992"] When doing preparation on typodont teeth for a ceramic crown, inlay, abutment preparation etc., how does on get the walls of the preparation to be parallell or convergent with the long axis of the tooth? It seems like I always have a problem with finding the long axis, whether it is in the mandible (where the curve of wilson is confusing me), or in the maxilla where my preparation walls (mesio-distal) tend to be leaning to towards one quadrant. I typically place my bur perpendicular at the midpoint of the occlusal surface and define this as my long axis of the tooth If we for instance consider the incisors; I always end up with either by buccal or lingual walls being convergent and the other being either straight (prone to undercuts), or divergent (this depends on the quadrant since I'm right-handed) I think this mistake is due to me not angling the bur towards the long axis of the tooth. When I am working I feel like my bur is relatively straight, but I always end up with one of my walls being not to convergent. My second question is regarding the inter-proximal reduction of tooth structure; how does one clear tooth structure inter proximally without touching the adjacent teeth and at the same time leave sound tooth structure behind during a preparation? I always end up with walls high in convergence angle (i.e. not convergent) and also a rough finish line. I will be happy if anyone has tips on angling the bur/holding the dental handpiece towards the long axis of the tooth; finding the correct path of insertion when doing a prep for a crown/abutment/bridge (Note that I'm assuming that the ideal path of insertion for a crown is almost parallel with the long axis of the teeth due to the forces applied to tooth structure - tell me if i'm wrong) [/QUOTE]

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