Monocem: A Great Concept in Self-Etching Luting Agents
Karl F.Leinfelder, DDS, MS
Regardless of their composition, indirect restorations historically have been cemented with zinc phosphate and polycarboxylate luting agents. The development of resin luting agents and glass ionomer cements, particularly in conjunction with the advent of hybridization concepts, has dramatically changed this type of approach. In contrast to traditional systems, it is now possible to not only bond to the surface of the tooth but also to the internal aspect of the restoration. Furthermore, the incorporation of these new concepts offers the promise of increased clinical longevity because of a decreased potential for microbial invasion and an increased resistance to secondary caries, as well as improved retention.
While the enhanced clinical performance of the earlier resin cements was most welcome, the efforts necessary to use these novel materials were extensive, time consuming, and subject to error because of technique sensitivity. Specifically, both the preparation and the restoration had to be individually addressed. Some of the more traditional cementing techniques include acid-etching, rinsing, and drying of the prepared tooth, applying the dentin bonding agent, and then light-curing the restoration. Additionally, the internal aspects of the restoration require sandblasting and then surfacing with the appropriate sequencing of adhesive agent.
MonoCem™ (Shofu Dental Corporation, San Marcos, CA) was developed to simplify adhesive resin cementation and deliver the positive goals associated with excellent bonding without the numerous steps commonly necessary to do so. The simple procedure for luting and bonding the restoration are:
- Rinse and leave the prepared tooth moist. The fabricated restoration itself should be left dry.
- Inject the self-etching cement directly onto the internal surface of the restoration.
- Insert the restoration onto the preparation; light-cure and/or self-cure.
In addition to the uniquely straightforward and simple directions for bonding the restoration, MonoCem is characterized by a number of excellent properties. It is a resin-based material with a filler content of 60%, providing it with excellent compressive (4,400 psi/310 MPa) and tensile strength. Despite the unusually high filler loading, the film thickness ranges between 11 µm to 12 µm, depending on the particular shade. The combination of the fine film thickness and dentin bonding ability results in the potential for generating margins which are virtually undetectable.
Other features of MonoCem are its ease of mixing, dispensing, and application. Consisting of a base and a catalyst, the material is packaged within a double-barreled syringe. Using minimal force, the material is ejected through an auto-mixing tip. Because of the miniature size of the mixing device, the amount of material wasted in the mixing tip is less than 0.2 mL per mix. Because no special treatment of the restoration or the preparation is required, the luting agent can be injected directly onto the internal surface of the restoration or prosthesis that is being cemented. Because no dentin adhesives, etches, conditioners, or restoration surface treatments are required, the potential for a more predictable seating of the indirect restoration is likely. Finally, substantially reducing the number of steps that are typically required for cementation lowers the level of technique sensitivity and increases the potential for clinical success.
Another feature of this self-etching cement is its fluoride content and releasing ability. The fluoride ion release has been determined to be 7.9 ppm but is not associated with glass ionomer chemistry. Rather, the fluoride ion is actually part of the resin matrix, eliminating the potential for material degradation. Effective fluoride ion release plays a significant role in killing microbes responsible for cariogenesis long after the restoration has been inserted. Furthermore, the fluoride-containing resin matrix (using Embrace technology) undergoes total (100%) polymerization.
Eliminating the need for separately hybridizing the dentin surface to achieve high bond strengths also is an important feature. The incompatibility of dentin bonding agents and self-cure resins has been reported extensively in the literature but surprisingly has never prompted a clinical concern. Such incompatibility can cause interface failure and can obviously lead to nanoleakage, postoperative sensitivity, and debonding.
MonoCem is recommended for luting nearly all types of restorations; it is contraindicated for veneers. The recommended indications include precious and base-metal alloys, porcelain-fused-to-metal and metal-free crowns, bridges, inlays and onlays (both ceramic and laboratory-processed composite resins). Interestingly, this self-etching resin cement can be used with porcelain restorations without the need for silanation. It is also effective in bonding to both alumina- and zirconia-based ceramic systems. Furthermore, it successfully bonds chemically and mechanically to all types of core materials as well as to posts, including fiberglass and all types of alloys. Finally, the retention characteristics of this self-etching luting cement to most restorative systems are high.
Because the curing mechanism is based on chemical and light activation, there are many advantages. While the bulk of the cementing agent sets by chemical activation, the clinician can cure the margins in seconds. This means that cement exposed to moisture in the oral cavity can be cured on demand, preventing salivary contamination of the setting cement. Once the crown has been seated, exposing extruding cement to light activation for 2 to 3 seconds causes the material to attain a gel-like, nonsticky state. It is then possible to easily remove the extruded material with a scaler or explorer. The common problem of removing hardened cement well beyond the margins and interproximally is thus made considerably easier.
The development of MonoCem self-adhesive resin cement is a major advancement in resin-based luting agents. This recent addition to the clinician’s armamentarium has extended the indications for resin cements and also dramatically simplified the process of cementation. Based on its properties and applications, it is probable that clinical longevity of all indirect restorations used in conjunction with this highly advanced material can be extended appreciably when indirect restorations are used in conjunction with this material.
MonoCem Self-Etching Resin Cement is available in a number of formats. There are 2 shades: translucent and bleach. The kit also contains automixing tips and effective finishing points. In addition to 7-gram syringes, Shofu plans to introduce 3.5-gram syringes in the near future.
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Properties of MonoCem™ Self-Etching Resin Cement
|Figure 1 The MonoCem™ self-etching luting agent.||Figure 2 Finalized full-crown preparations on teeth Nos. 8 and 9.|
|Figure 3 Injection of luting agent into one of the ceramic crowns.||Figure 4 Seating and cementation of the full-crown ceramic restorations.|