How do you treat a portion of all porcelain crown that breaks off in esthetic zone?
This question was submitted by a general dentist: Portion of all porcelain crown breaks off in esthetic zone. Do you etch porcelain first with hydrofluoric acid and then enamel/dentin with phosphoric acid, then silane primer on porcelain, then bond on tooth, then restorative material? Is it a big concern, if a little of the hydrofluoric acid gets on tooth structure – could happen easily, especially with a smaller tooth like a lower incisor.
Dr. Omar El-Mowafy, Professor and Head of Restorative Dentistry in the Faculty of Dentistry at the University of Toronto provided this quick initial response
I am of the opinion that intra-oral use of hydrofluoric acid should be completely avoided as the risks involved in using it outweigh the benefits.
Alternatively, the fractured area of the porcelain crown can be conditioned with 50 um aluminum oxide powder in a microetcher followed by silane application. Bonding to dentin can be achieved following conventional methods. If the crown was located in a highly-esthetic area then perhaps consideration should be given to replacing it with a new one. Repairing porcelain with composite will be highly unlikely to result in optimum esthetics.
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I have had a nunber of cases of fractured PFM’s over the years,where the patients have wanted to try to repair,even after being told that “there (was) no guarantee”.
I have used the kit from Bisco,called All-Bond 2 with some success.The kit does suggest using a microetcher to roughen the metal and the pocelain,and to treat the pocelain with HF acid(for 3-4 miutes!!).I see no issue wth the use of the acid as long as isolation from the tissues and the rest of the oral cavity is obtained by use of the rubber dam.To me,there is no compromise.By placing even the smallest drilled holes in the metal susructure,and in the pocelain(if adequate thickness allows it..otherwise you risk fracturing off more porcelain) preferably at right angles to each other for maximal mechanical retention built into the chemically bonded repair,I have had some goo results.
The 2 main shortcomings is
1.if the repair is involving occlusion,there is less long term stability.
2.No matter how well you try to mask the metal with opaquing resins,and blend the resin shade with the pocelain shade,due to the transluscent effects of the materials being diferent,the final esthetic result is less than desirable.
I have had about 3 or 4 cases occurring in aesthetic areas over the last 45 years of practice, and with the use of kits plus advice from knowledgeable individuals I have had none lasting beyond 5 years.
Complete replacement is your best option.