Prep to Cem: Control at every step

17 December 2021
5 min read
Published:

Akit Patel discusses which indirect restorative materials are best for particular indications.

The complete procedure for the securing of an indirect restoration to tooth structure can sometimes be long and complex. Before we even embark on our restorative journey, several considerations must be made. Which indirect restorative material is best for that particular indication and does the tooth in question have the appropriate support for the prosthesis? If not, do we need to consider a post and core or just a better preparation to support the final restoration. Does the support for the restoration have specific impression material considerations? What material should we consider for the temporary? Is aesthetics important, or is form and function more critical? And finally, how will we secure it to the prep?

Construction and design of any prep is another complex area and will not be covered here, but protecting our newly constructed support for our indirect restoration is critical. Temporary material selection needs to be based on the clinical situation. Gun based materials are highly versatile and great for temporizing most indications, however 3M Protemp Crowns can offer a quick, provisional solution to the single unit prep. Indicated for molars, premolars and canines, 3M Protemp Crowns can be moulded easily to fit most single unit preparations and do not require a matrix or impression, unlike most gun-based products. The occlusion can then easily be established by the patient biting down on the malleable material.

Gun based temporaries have been around for many years and differ widely when it comes to strength and aesthetics. High strength is critical for posterior temporaries and if the temporary restoration needs to be in place for longer than a few days. Aesthetics are key if the restoration will be in a patient’s aesthetic zone, but also good long-term aesthetics require a material not to stain over time. Good gingiva adaptation is also critical to giving good aesthetics during the temporisation phase.

3M Protemp 4 is the only 100 per cent nano filled temporisation material currently on the market. The nanofiller not only provides high strength and excellent aesthetics, but also allows good adaptation to the soft tissues. Indicated for 12 months, this gives plenty of time for perio or other treatments to aid the development of healthy soft tissue, which will aid the overall final aesthetic appearance of the final restoration.

Temporary materials provide the appropriate prep protection, functionality for the wearer and adequate aesthetics whilst the final restoration is being customised. Prior to temporisation, final impressions will have been taken to enable the laboratory to produce the appropriate indirect restoration. This typically takes a couple of weeks, so it is important that the chosen temporisation material is indicated to last for at least this length of time.

Impressioning is key to getting an accurate fitting restoration and a good fit will add to the overall aesthetics of the final prosthesis. For accurate impressions we typically have two material types to choose from; A- Silicone (often referred to as VPS materials) or polyether. Whichever you choose, the key is to ensure that the material used is hydrophilic. By their difference in chemistry, polyether impression materials are one of the only naturally hydrophilic impression materials on the market.

A-Silicones are made to be hydrophilic by the addition of surfactants, but these often take a while to rise to the surface of the material, meaning that on contact in the oral cavity, many A-Silicones often remain hydrophobic for a number of seconds before the surfactants reach the surface.

Now, the oral cavity is not dry. Dentine is not dry. Most dental procedures involve water and may have resulted in some bleeding or the production of other fluids. So, it is critically important that the impression material of choice can cope with some degree of moisture and adapt nicely to the prep in question.

3M Imprint 4 VPS Impression material is one of the most hydrophilic A-Silicone materials on the market due to its novel chemistry. Imprint 4 is also the only A-Silicone currently to offer active self-warming, a process whereby the material warms during its working time to approximately 37°C resulting in a snap-set setting profile right at the end of the working time. Much of the setting reaction then happens very rapidly, leaving little time for any unintentional movement to cause errors in the final impression. With three tray materials and five washes to choose from, Imprint 4 is a very versatile, simple, and hydrophilic impression material to use for all indications.

Despite the exceptional properties that are exhibited by Imprint 4, many would consider polyether impression materials to be the gold standard when it comes to moisture tolerant impression materials. With over fifty years of clinical evidence to support it, the 3M Impregum Penta family is still incredibly unique and offers the clinician peace of mind when moisture control is difficult. Impregum is often considered a hard setting, bad smelling material that takes an age to set, which is probably true with some of the older generation materials. Now, with over twelve materials in the portfolio, 3M Impregum Penta can be used exactly how you want to use it. Available in monophase or putty / wash with a variety of setting times, the more modern polyether materials are mint flavoured and can be dispensed from an automatic mixing machine such as the 3M Pentamix 3 automatic mixing machine.

Finally, we come to cementing the final restoration onto our prep. Luting cements have come a long way and most materials available today are delivered either in a capsule, which needs to be activated and mixed, or an automix syringe, which allows a two component paste system to be extruded through a mixing tip to initiate the dual cure phase of the setting process. Cement mixing via an automix syringe has always been a challenge for product development teams. The combination of mixing tip length, design of the internal tip spiral, the chemistry of the material and the timings of the dual cure activators are all key in making sure a dental cement works correctly and has the specified working and setting time to allow accurate seating of indirect restorations. The limitation is that the remaining volume of cement in the tip after dispensing is waste and must be disposed.

For the last few years, 3M has gone back to the drawing board and created a brand-new innovative tip that uses less plastic and reduces cement waste by up to 80 per cent* when compared to current automix delivery systems, without compromising performance and cement properties. The new design allows for reduction in waste, less material needed per application, and a much smaller syringe system compared with other automix cements on the market. The smaller, more ergonomic syringe results in up to 50 per cent less plastic waste* compared to other automix syrgines, but also reduces storage space.

Welcome 3M RelyX Universal Resin Cement. The latest addition to the RelyX family of dental cements.

On its own, RelyX Universal can be used as a self-adhesive resin cement. Used in combination with the new 3M Scotchbond Universal Plus Adhesive (currently the world’s first radiopaque universal adhesive), it is a fully aligned system that consists of only two components for the cementation of all indications. Some of the highlights of the new system are:

  • Simplifies the resin cement workflow and training of operating personnel by reducing work steps and possible errors
  • The cement initiates and cures the adhesive without an additional light-cure step
  • The already high bond strength of the cement in self-adhesive mode can be further enhanced with the adhesive*
  • The system shows higher bond strength values to zirconia than competitors, as found in a Dental Advisor study (Dental Advisor Biomaterials Report, no 133, July 10, 2020)
  • Both products show virtually no post-operative sensitivity*
  • The system enables a therapy completely based on BPA derivative-free formulations*

A recent study from the Dental Advisor found that, “The new 3M mixing tips were about five times more efficient in terms of cement waste than the Mixpac helical taper mixing tips included with four common cements, and over six times more efficient than the longer helical mixing tip included with Maxcem EliteTM Chroma. The new 3M syringe packaging had half as much plastic waste per application as other automix cement systems. Overall, the new 3M system utilized around 67 per cent of the packaged cement towards filling crowns, whilst the next closest system used less than 32 per cent. The 3M RelyXTM Universal system can give up to 15 full applications for an average use of 90μL, and up to 20 applications for cases requiring 60 μL aliquots”[1]

*3M internal data. Claims available on 3M.co.uk/dental

[1] M. Cowen, J.M. Powers, Dental Advisor Biomaterials Research Report, Number 134, 23rd June 2020.