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    How to prevent subgingival margins by the use of a new resin temporary cement

    How a new cement from VOCO can avoid problems in partial coverage restorations.

     

    Making temporaries for preparations without mechanical retention

    Predictable provisional restorations for onlays and veneers are indispensable, although many find them difficult. Many choose to do leave-in or shrink wrap provisionals, because they lock into place. Leave-ins have the disadvantage of usually leaving too much flash in the gums.  This often causes inflammation and bleeding, upon provisional removal, which increases the difficulty of resin cementation. Additionally leave-in temporaries become a mostly doctor procedure, as all the cleanup of the excess provisional material has to be done with a handpiece or a 12 blade, both of which are doctor only procedures. In my practice, provisionals are mostly performed by my assistants. I prefer that they remove the provisionals, trim margins and adjust occlusion extra-orally, and then cement. This technique gives me cleaner margins, which means that at cementation, the gums will be less inflamed, there will be less bleeding, making cementation a snap. It also has the advantage of being mostly assistant work, thereby freeing me up to see other patients.

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    For an onlay temporary, take a preoperative impression of the tooth using some type of hydrophilic alginate substitute like Silginate (Kettenbach). For veneers make a silicone putty matrix of a suitable wax up. After tooth preparation, fill the silicone matrix with some type of Bis-Acryl temporary material, one of the best on the market is Structur 3 (VOCO).  It has excellent translucency, strength and with a top surface so smooth it makes polishing unnecessary. Removal of flash can be done in seconds using a Sof-lex Disk (3M ESPE).

    The problem has always been that most provisional cements are too weak to support flat preparations without mechanical retention. Enter Bifix Temp; this is resin cement, which shrinks like any composite while curing.  It is strong and stiff, so it locks on to any undercuts, interproximal spaces, etc. (Fig. 3).  If necessary I may spot etch and bond, Bifix Temp, being a resin, it will adhere to the bonded spot very well. I have been using resin temporary cements for many years, but I find Bifix Temp  superior because it is dual-cure making the procedure much faster. It also has great translucency allowing for excellent blending of the temporary restoration (Fig. 4), which is very important for veneer cases, and cleanup is easy. It is important to mention that Bifix Temp as a resin cement can bond to resin buildups, so a layer of Vaseline should be placed over the buildup before cementation to avoid complications.

    Using Bifix Temp, can take away one of the biggest excuses to cut full crowns, and hopefully will encourage more dentists to start using supra-gingival minimally invasive adhesively retained restorations like veneers and onlays more often.

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    References:

    Reitemeier B, Hänsel K, Walter MH, Kastner C, Toutenburg H. Effect of posterior crown margin placement on gingival health. J Prosthet Dent. 2002 Feb;87(2):167-72

    Lareto D. Effects of cervical margins on gingival. J Cal Dent Assc, 1969; 45; 19

    Thomas MS, Kundabala M. Pulp hyperthermia during tooth preparation:the effect of rotatory instruments, laser, ultrasonic devices and airborn particle abrasion. CDA Journal 2012;40(9):721-731

    4 Davis GR, Tayeb RA, Seymour KG, et al. Quantification of residual dentine thickness following crown preparation. Journal of Dentistry 2012; 40( 7): 571–576

    Jose-Luis Ruiz, DDS
    Dr. Ruiz is director of the Los Angeles Institute of Clinical Dentistry and former director of USC’s Esthetic Dentistry Continuum. He ...

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