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TheraCem - The Next Generation Cement

TheraCem

Joseph S. Kim, DDS

Indirect restorative materials have evolved rapidly over the past few years, providing clinicians with a variety of options to better serve their patients. However, more choices in the substrate material often result in more steps in the cementation protocol, usually with specific and additional procedures that address the peculiarities of the chosen material. In addition, a cement chosen to increase the retention of the indirect restoration comes with the cost of increased technique sensitivity and chair time to deliver the restoration.

Dental cement technology represents one of the major advancements in restorative dentistry. For over a century, older cements such as zinc phosphate and zinc oxide eugenol allowed for predictable retention of indirect restorations for and various formulations are still used today.  However, these materials may require protective measures in deeper preparations to avoid pulpal irritation, and are susceptible to dissolution in water.  Glass ionomer cements were invented in 1968, and similar to earlier silicate based products, they have the major benefit of releasing fluoride.1 However, while this cement is easy to use, it is also water soluble, and even modern resin modified varieties ideally require at least 15 minutes of protection from moisture contamination after placement.2

With advances and simplification of bonding protocols, resin cements have become more popular due to the high retention bond strengths which are achieved through micromechanical and chemical adhesion. Bonding is required for certain substrates often due to fragility or minimal surface area available for adhesion to the tooth; this includes composite and ceramic inlays and onlays, and for full coverage restorations that may exhibit compromised angulation of the preparation or minimal height. Unlike most other cements, resin cements are insoluble to water and oral fluids.

Traditionally, resin cements required preparing tooth by etching, priming, curing, soft tissue management to stop any bleeding, and isolating the tooth from moisture. These steps were time consuming and often the tooth was not optimally prepared due to technique sensitivity, such as excessive etching and desiccation of the dentin. Also, subgingival margins were often difficult to manage after exposure to the etchant and again after application of the adhesive.

Self-adhesive resin cements offer a simple solution to the traditional compromise between retentive bond strength and technique sensitivity. By combining the benefits of bonding with a cementation protocol that is easier than for traditional cements, self-adhesive resin cements provide outstanding retention with maximum simplicity. The self-adhesive feature means there is no need to apply etchant, primers, or adhesives to the prepared dental surfaces. This translates to greater predictability in preparations with subgingival margins, where etchants or bonding agents may cause bleeding.

BISCO’s latest resin cement advances this concept with universal adhesion to all popular substrate materials. TheraCem is a dual-cured, calcium and fluoride-releasing, self-adhesive resin cement indicated for luting crowns, bridges, inlays, onlays, and all types of posts.  Delivering a strong bond to Zirconia and most substrates, along with easy clean-up and high radiopacity, TheraCem offers clinicians reliable and durable cementation of most indirect restorations. Due to innovative chemistry, TheraCem achieves a high degree of conversion, which improves physical properties for added bond strength, without the need for refrigeration when it is not being used. For clinicians, this means that peace of mind can be nearby and ready to use in every operatory.

In the first case, a tooth with a subgingival margin preparation has been cleaned with an ultrasonic scaler and was gently dried in preparation for cementation. Note how the margin goes deeper subgingivally on the distolingual. (Figure 1) With TheraCem, a clean, prepped dentin or enamel surface is all that is needed to achieve excellent bond strengths, with the added benefit of sustained calcium and fluoride release. While TheraCem forms a strong bond to most substrates, including zirconia, in order to achieve optimal bond strength, a zirconia primer is still used prior to try-in, to prevent salivary contamination of the zirconia surface. (Figure 2)

Fig_1

Figure 1
Cleaned and prepared tooth

Fig_2

Figure 2
Z-Prime™ Plus single component priming agent

TheraCem exhibits minimal resistance to seating, but is not runny. (Figure 3) Clean-up is easy with hand instruments and floss. (Figure 4) For deeper subgingival margins, TheraCem is kind to the gingiva, although the margins should be thoroughly inspected to ensure complete removal of excess cement. (Figure 5)

Fig_3

Figure 3
TheraCem in use

Fig_4

Figure 4
TheraCem being cleaned up

Fig_5

Figure 5
Inspected margins

In the second case, a full arch of full contour, anterior, zirconia restorations are primed with zirconia primer and ready to be tried in. (Figure 6) Due to her short clinical crowns, TheraCem was chosen to provide maximum retention of the zirconia restorations. In her case, attrition due to bruxism had reduced the height of her teeth, and almost no vertical reduction was performed from first premolar to first premolar. (Figure 7) After try-in, the prostheses were rinsed and dried, and the front four crowns were delivered with TheraCem. (Figure 8) After preliminary clean-up of the cement, the upper left teeth were rinsed and gently dried. (Figure 9) The upper left restorations were then delivered with TheraCem.  (Figure 10) This was followed up with another preliminary clean-up of the cement. (Figure 11) A retracted view shows the final restorations after a thorough clean-up. (Figure 12)

Fig_6

Figure 6
Resotrations ready for try-in

Fig_7

Figure 7
Patient's teeth before restoration

Fig_8

Figure 8
Delivery of front crowns

Fig_9

Figure 9
Rinsed and dried upper left teeth

Fig_10

Figure 10
Delivery of upper left restorations

Fig_11

Figure 11
Preliminary cement clean up

Fig_12

Figure 12
Final restorations after clean up

In both of these cases, where subgingival margins were present around each preparation, TheraCem was simple to use, easy to clean-up, and did not require etching and priming each tooth prior to cementation. This resulted in a measurable decrease in chair time and frustration for both clinician and patient, especially in the second case, which was delivered in under 30 minutes after administration of local anesthesia.

1. Schulein TM. Significant Events in the History of Operative Dentistry.  Journal of the History of Dentistry. 2005;53(2):63-72.

2. Weiner R. Liners, bases, and cements: Material selection and clinical applications. Dentistry Today. 2005;24(6):66-72.

 

Winter 2017 BisDent Globe, Volume XXIII, Issue I

 

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