According to the Principle of Convenience form, there should be a clearance of 0.3 to accommodate the matrix band, access for proper finishing and polishing of the restoration and adequate access for home care. Checking the clearance is easy, just run the tip of the explorer (gingival to occlusal direction, vice versa) at the buccal, lingual and gingival aspects of the proximal box. So you should be able to trace all of these walls, taking a look that they should be completely not in contact with the adjacent tooth.
- Checking for clearance
- Checking for Clearance
- Dealing with Closed Contacts
Contact Areas of Typodont
Especially in Kilgore typodont, contact area are often too occlusally located that sometimes you don’t need to actually create a box just to clear the contacts. Or in some cases the contact itself is purely non existent. It depends on the variety or some manufacturing problems that we do not know of. But whichever the set-up of the contact area may be, we still should create a good proximal box. The ideal height of an axial wall of the proximal box should be at least 1mm.
In cases where there is a tight contact and you have already exceeded the minimum 1mm, you have to be deep as you need to be until you break the contact. A “Closed contact” is a very grave mistake. This is not clinically acceptable. You really have to clear the contacts, no exceptions.
ERRORS
Did not visualize the contact areas properly and failed to plan the exit points of the buccal and lingual walls of the proximal box.
Stopped extending the buccal and lingual walls and the gingival floor of the proximal box because was afraid that the dimensions of the box is too large already.
TROUBLESHOOTING
“Closed contact” is a very grave mistake. This is not clinically acceptable. You really have to clear the contact, no exceptions. Even if you see that your proximal box is too big already (or exceeding out the ideal dimensions) but haven’t opened the contact yet, you must clear the contact. Use your bur to extend all of these walls. If you see a thin (evident but not enough) clearance then In this case, you may use hand instruments to extend the B-L walls and lower the gingival floor little by little until you achieved a 0.3 clearance.
Do not attempt to use a hand instrument to clear the clearance when it is still in full contact with the adjacent tooth because you will end up having “scooped” out walls.
When checking for clearances, do not just casually run your explorer or move the explorer back and forth between the teeth and conclude that the contact must be closed. However, they forget to see that they should check 3 areas of the proximal box: buccal, lingual and gingival rather than checking them as one single entity. Often times when they’ve seen that there is a closed contact, they extend the prep buccally and lingually, though in fact the real problem is that the gingival floor has a closed contact.
So the lesson of this problem is to first figure out which of these three areas have a closed contact. Check each of these areas and only then you can determine where you must extend to clear the contacts.
TIPS
When you are working with an occlusally located contact or perhaps a loose contact, do not make the depth of the occlusal prep too deep than the ideal. In this way, you can create a proximal box that is not too wide and with enough axial wall height.
Measure always. Utilize the length of your bur for measuring and planning accurate dimensions.
Check the buccal, lingual and gingival areas of the proximal box for clearance. Whichever of these areas has a closed contact, do make your extensions on that area only. Do not touch the area that has a good clearance already.
LINK: how to check clearance