Taking a single stage dual phase addition silicon impression – the gold standard for restorative dentists – Dr Minesh PatelFeatured Products Promotional Features
Posted by: The Probe 4th February 2019
Minesh Patel graduated with honours from Barts and the London School of Dentistry in 2009. He then went on to graduate with a Master’s degree in Aesthetic Dentistry at King’s College London in 2013 while simultaneously completing a one-year surgical and prosthetic implantology programme based in Cambridge. He currently works in a fully private practice in Thames Ditton, Surrey and spends time teaching on various postgraduate programmes at King’s College London as well as lecturing around the country on clinical dental photography.
The female patient was referred to me following two recent root canal treatments on her UL5 and LR4. The teeth were previously heavily restored, with evidence of cracked tooth syndrome and non-vital pulps, hence full cusp coverage was now indicated. Following a period of observation to ensure success of the root canal treatments, both teeth were planned to receive full coverage zirconia crowns with selective buccal layering.
On the day of treatment, both teeth were prepared for full contour zirconia restorations (see Fig 1). A double cord technique was employed prior to impression taking. This technique involves placing a 0000retraction cord prior to tooth preparation. After gross tooth reduction, a second 000cord was lightly tucked into the sulcus before marginal finalisation using a modified Arkansas Stone (see Fig 2). Finally, the restorations were polished and finished using a Sof-Lex disc and a silicone polisher to prime the tooth preparations for final impressions.
When taking crown and bridge impressions, it is important to use either a thick stock plastic tray, such as the COLTENEPRESIDENT®impression trays (see Fig 3), or a metallic non-perforated rimrock tray (see Fig 4). Both options provide the necessary rigidity to prevent silicone-based impression materials distorting on impression removal and transportation.
Making the impression
For this case,AFFINIS®BLACK EDITION and silver coloured AFFINIS®PRECIOUS light body wash, both from COLTENE, were employed to take a single stage dual phase addition silicon impression (see Fig 5). This is considered the gold standard amongst restorative dentists and prosthodontists. The technique involves heavy body tray material of thick viscosity (AFFINIS®BLACK EDITION) that is dispensed into the impression tray via an auto mix dispensing gun or pentamix machine; my dental assistant prepared this. During tray loading, the tooth preparation was thoroughly dried and the 000cord gently removed using tweezers. This was followed by the immediate syringing of the ultra-low viscosity light body wash material (AFFINIS®PRECIOUSlight body) into the sulcus, then over the entire tooth preparation and adjacent teeth. The full arch impression tray was then inserted in a rotational motion while supporting the lips with my index fingers.
Delivery and fit
The material has a quick setting time of three minutes from dispensing, and following the complete set the impression was withdrawn and margins inspected. As you can see, the wash has excellent thixotropic properties and reproduced the preparation and gingival margins very well (see Fig 5). The strong contrast between the black tray material and silver wash makes it very easy and efficient to ensure sufficient wash coverage over the preparation as well as check for any errors.
Following delivery of the crowns the die stones and ceramic work were reviewed to be satisfactory (see Fig 6). Both restorations were tried in and an excellent marginal and occlusal fit indicated accurate impressions as well as good laboratory protocols.
The preparations were cleaned with an ultrasonic scaler and a diamond impregnated polishing brush. This was followed by preparation conditioning and thorough rinsing and drying. The zirconia restorations were luted using a resin-reinforced glass ionomer cement. The excess was removed during the gel set phase and the contacts cleared with floss. The occlusion was then verified using articulating paper to ensure the restorations conformed to the pre-existing occlusion. Shimstock foil was used to check tight holds on the adjacent teeth, as noted pre-operatively, and the restorations were confirmed to be clear in excursive movements.
Post-treatment and final appraisal
The patient was recalled three weeks later following crown cementation. Post- operative photos demonstrated beautiful ceramic work courtesy of Chris Howe Ceramics – the fantastic results can be compared with pre-operative photos of the two crowns (see Figs 7 and 8).An excellent soft tissue response was evident, indicating a smooth transition from finishing line to ceramic emergence profile. This can be attributed to accurate die stone fabrication thanks to a good impression technique using COLTENE AFFINIS®BLACK EDITION and AFFINIS®PRECIOUSlightbody,which I consider to be high-quality impression materials.
To find out more visit www.coltene.com, email email@example.com
or call 01444 235486
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