Technique tips: posterior temporary crowns: a freehand technique

I recently saw a patient who had four amalgam restorations. All had interproximal overhangs. Figure 1 presents the DPT radiograph, while Figures 2, 3 and 4 present close-ups of the four restorations, or is it five, as some seem to be joined. Although none had finger or thumb prints on the occlusal surfaces, I reckoned that they had each been placed using the ‘thumb technique’, a technique about which the excellent readers of Dental Update will be unaware. In this, the restorative material is pushed into a Class II cavity from the occlusal surface using a thumb or finger. Perhaps the clinician had missed dental school or had been asleep on the day that matrix band techniques were being taught!

Readers will, however, be aware of the dangers to the periodontal tissues which accrue from amalgam (or other materials') ledges. Most of the research on this was carried out some time ago, but it is worth highlighting the work of Jeffcoat and Howell¹who compared, in a split mouth design study, 100 restorations with ledges and 100 contralateral teeth with no ledges. The results indicated that bone loss was greater on teeth with overhangs; the more severe the disease the greater the role of the overhang and small overhangs not resulting in bone loss. Other papers^2,3 reported similar findings, even if Chan and Chung⁴ rather glorified the problem of overhangs by calling them amalgam hypertrophy! Calculus present on root surfaces could be considered to have a similar effect.

There is another side to this story. The late great Bernie Kieser (once a member of the Editorial Board of Dental Update) and his co-workers carried out a large amount of research on this. He was sometimes misquoted as believing that overhangs and calculus were not a problem: what his work indicated was that these were not a challenge to periodontal health, provided that the patient could keep such areas free from plaque. He, with his co-workers, therefore instigated changes in the conceptual management of root surface contamination, summarized in an excellent and detailed review by Chapple.⁵ In this regard, Keiser and co-workers demonstrated that endotoxin could be removed from the root surface without the need for aggressive over-instrumentation of the cementum, advocating cementum preservation, even if some calculus remained, leading to the concept of root surface debridement,⁶ which is now an established technique.

Finally, I should add that, in the patient whose restorations are illustrated above, the amalgam in UL8 had survived for 22 years and the radiograph indicates circa 20% interproximal loss of bone! Perhaps, therefore, the thumb technique wasn't so bad? I should, however, draw readers' attention to the fact that I am finishing writing this Comment on 1st April (April Fools' Day)!