The best way to adjust proximal contacts of newly fabricated crowns has been a long–standing unresolved issue in dentistry. Excessively tight contacts cause incomplete seating of crowns and extrusion of adjacent teeth, which leads to patient discomfort, hypersensitivity, and recurrent dental caries at the crown margins. When seating crowns, Interproximal Relief (IR) should be restored as it exists in natural dentition.
Restoring natural proximal contacts is critical to the success of crowns. This directly affects a dentist’s ability to achieve complete marginal seating, maintain existing occlusion, and provide patient comfort. Inadequately restored proximal contacts may cause food impaction by open contact, or may cause incomplete margin seating of indirect restorations by overly tight contact. Dental school curriculums offer surprisingly little instruction on fixing and adjusting proximal contacts, and there is little written research on this subject.
In my experience, crowns sometimes must be refabricated due to improper proximal contacts of the final restoration after chairside adjustment. This occurs when the restoration’s too tight on one side and opens up on the opposite side.
After years of research and experiments, I have developed a clinically proven method for determining and adjusting proximal contact strength by using diamond dental strips.
With this method, ideal proximal contacts can be achieved accurately with minimal time and effort, while enhancing patient comfort and functionality immediately upon definitive cementation.
In the Literature
Small spaces occur between natural teeth and floss does not properly detect these spaces. Lindquist JT, M.Sc. thesis, Indiana University School of Dentistry, 1951.
In my experiments I also cannot properly detect these spaces with floss because floss is too thick.
Kim DS, at the presentation at Academy of Operative Dentistry meeting, 2013
An important factor in keeping food from packing between the teeth is the occlusal anatomy.
Goldman HM, Schluger S & Fox L (1956a) Periodontal Therapy, St. Louis CV Mosby Co, pp 477-479
The contact should not be so tight as to cause wedging of the teeth.
Howard WW, Moller RC. Atlas of Operative Dentistry, 1981 3rd edn, p.127, C. V. Mosby, St Louis.
A fixed partial denture be adjusted until 0.0005in. shim stock will pass through proximating contacts with very slight resistance.
Most unrestored proximal contacts will permit passage of shim stock in a like manner.
Campagni WV, The final touch in the delivery of a fixed prosthesis, Journal of the California Dental Association, 1984; 12, 21
Shim stock passed through 90% of the natural contacts.
Boice Pa, Niles SM, DuBois LM, Journal of Oral Rehabilitation. 1987, 14; 91-94
Interproximal Relief should be restored with passive contact or microscopic clearance when indirect restorations are placed.
Kim DS, Suh KW. J Prosthet Dent, April 2007, Vol 97 No 4, 244-245
Spaces ranging from 3 to 21 microns between adjacent teeth at rest are observed.
Kasahara K, Miura H, Kuritama M, Kato H, Hasegawa S. Int J Prosthodiontnics. 2000; 13:289
By aging most of the proximal contact surfaces are curved in the natural dentition.
Kim DS, Rothchild JA, Suh KW. General Dentistry, Aug. 2013, Vol 61 No 5, 60-63
As a result, I have designed a thin and flexible diamond strip like shim stock with ultra-fine diamond powder coated on to adjust proximal contact to microscopic clearance or passive contact.
Procedures
1) Evaluate and adjust the tight proximal contact using Black Diamond Strip:
A newly fabricated crown needs proximal contact adjustment in the patient's mouth. Between the mesial or the distal, most of new crowns have one side tighter than the other side, and the tight side should be adjusted. Repeat evaluation and adjustment until slight resistance is felt on the strip equally from the both sides. When there is slight resistance equally on both sides the proximal contact adjustment is done and the crown is ready for cementation.
2) When Black Diamond Strip wouldn't get in to the interproximal space because the crown is made too tight:
In patient's mouth, check the opening of the crown margin underneath towards the prepped abutment and closed side is the tighter side.
Place the crown on the stone working model, and adjust the tight proximal contact of the crown using Clear Stone Strip (0.10mm) or Cyan Stone Strip (0.12mm), and try back in the patient's mouth until the crown seats up to the prepped margin with resistance.
And then back to procedure 1).
3) Remove the cement using White Serrated Strip:
After removing all of the excess cement, use White Serrated Strip to cut and remove any cement pieces that are often trapped in the interproximal space.
4) Final Polish of the proximal contacts:
Polish the proximal contacts using Gray Final Polishing Strip and confirm Interproximal Relief.
5) Occlusal adjustment:
Because complete marginal seating is achieved, only minimal occlusal adjustment is necessary. Occlusal adjustment prior to cementation is not necessary and may result over-adjustment.
If you follow these procedures, every crown will be comfortable for your patients and you will have confidence in your crown seatings.
Thank you.
Daniel S Kim DDS
Q) Can ContacEZ strips over adjust and open the contact?
No. ContacEZ strips will never open the proximal contact. The reasons are:
1) In adjusting with the diamond strip, when the pressure between the two teeth approaches to the ideal passive contact, the friction is reduced and less abrasion occurs. Therefore, over-adjustment will not occurr.
2) Clinically, prior to cementation, crowns seat loosely on the abutment and any proximal adjustment with the diamond strip will move the crown away from the contact. Once the strip is removed, the crown will then move back into place. Then, when they are cemented into place, the crowns will have ideal passive contact.
3) Also there is a range of 0.10mm of tooth movement in natural dentition, which may contribute to the discrepancy by pushing away the crown when strip is inserted and coming back when the strip is removed.
Q) Why is final polishing after cementation?
1) Final polishing using rotary wheels before cementation may ruin the proper proximal contact that is achieved using Black Diamond Strip.
2) While doing final polishing Interproximal Relief is confirmed.
Q) Why does ContacEZ Diamond Strip flex?
1) The diamond strips should be flexible to follow along the curvatures of the proximal contact surface of the adjacent teeth, which will achieve the ideal proximal contact.
2) When a taut strip is used the contact surface can be flattened and contact can be opened which may cause food impaction.
3) The diamond strip should be thin like a shim stock with diamond powder coated on, and may distort easily if excessive force is applied.
Q) What will improper proximal contact adjustment cause?
1) Patient discomfort by excessive interproximal pressure
2) Incomplete marginal seating by heavy contact, which can cause recurrent decay.
3) Migration of teeth by heavy contact that may cause anterior crowding
4) Wedging reaction by heavy contact that may cause extrusion of the neighboring teeth, which may cause changes to the occlusion of the entire mouth.
5) Open contact may cause food impaction
Q) Why is occlusal adjustment done after cementation?
Traditionally occlusal adjustment is done mostly before cementation and confirmed again after cementation.
When occlusion is adjusted before cementation, it might be over adjusted because the crown is slightly floating on the abutment.
When the proximal contact is adjusted properly, and complete marginal seating is achieved, the occlusal adjustment after cementation will be minimal.
Finger pressure is recommended for crown cementation