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Ion bonding glass2/3/2024 ![]() Therefore, the cleanup of RMGI cements is easier as the cement does not adhesively bond to the tooth structure below the crown margins or on the adjacent teeth. RMGI does not bond to tooth structure as strongly as resin cements. 9 If the trend is similar for RMGI cement, it will imply that many clinicians undertake the task of cleaning fully or tack-cured RMGI cement (some brands of RMGI cement are capable of tack curing). RMGI cements are easier to use than resin cements as they are often easier to clean and do not require the additional steps needed for bonding ceramic crowns.Īn ADA Clinical Evaluator Panel survey of resin cements reported that 21% of dentists clean some uncured cement, 85% of dentists clean some tack-cured cement, and 28% of dentists clean some fully cured cement. The next section of this article will discuss considerations for RMGI cementation, followed by a discussion of the steps for bonding ceramic crowns with resin cement (Table 1).ĬONSIDERATIONS FOR CONVENTIONAL CEMENTATION WITH RMGI OR GLASS IONOMER CEMENT Therefore, conventional cementation is still very popular. They will also require a more complicated clinical procedure. 4ĭespite the advantages of resin cements, a limitation is that they must be used in cases in which isolation from saliva and blood is possible. Translucent zirconia (4 mol% or 5 mol% yttria-containing) is weaker than traditional zirconia (3 mol% yttria-containing), which means it will require slightly more restoration thickness.Ī recent study suggested a restoration thickness of 1.2 mm for 4 mol% or 5 mol% yttria-containing zirconia, whereas 3 mol% yttria-containing zirconia has been recommended 8 to be used between 0.6 mm and 1 mm.īonding both translucent and traditional zirconia will improve its strength however, it is less critical to bond any type of zirconia than it is to bond to lithium disilicate. Recommendations for zirconia are dependent on its composition (3 mol%, 4 mol%, or 5 mol% yttria-containing). ![]() For materials such as feldspathic porcelain veneers, the ceramic must be bonded to tooth structure in order to survive in the mouth.įor lithium disilicate, manufacturers recommend a minimal restoration thickness of 1 mm if the crown is bonded and 1.5 mm if the crown is cemented with a glass ionomer or an RMGI cement. The need for strength reinforcement through bonding is dependent on both the strength of the ceramic material and the thickness at which it is used. In theory, a bonded crown will transfer occlusal forces to the substructure, whereas a conventionally cemented crown will not. ![]() (a) Axial wall height should be 3 mm for premolars and (b) 4 mm for molars.Ĭeramic crowns are also bonded in order to improve their strength. A taper of 12° is recommended for conventional cementation 7 (Figure 1).įigure 1. 6 Preparation taper also affects resistance form. 5 If crowns are shorter, resistance form can also be improved by adding proximal grooves however, decreasing the taper of the cervical portion of the crown preparation is more effective at improving resistance form. Axial wall height, as determined by prosthodontic literature, should be 3 mm for premolars and 4 mm for molars. Retention is assessed by axial wall height and taper. The choice of which cement to use for a ceramic restoration can be simplified into an assessment of the need for additional retention of the preparation or additional reinforcement needed for the restoration. 2 Although resin cements provide more retention 3 and greater strength reinforcement of ceramic crowns 4 than RMGI cement, RMGI cements are easier to use, more moisture tolerant, and protective of crown margins. In this study, 70% of lithium disilicate, 30% of zirconia, and 14% of PFM crowns were bonded with resin cement, and the remainder were conventionally cemented. For the purpose of this article, conventional cementation involves the use of a glass ionomer or resin-modified glass ionomer (RMGI) cement, whereas bonding implies the use of a resin cement and ceramic primer.Īccording to the National Dental Practice-Based Research Network study of nearly 4,000 single-unit crowns, 38% of the crowns were bonded with resin cement, whereas 52% of the crowns were cemented with RMGI cement, and 9% were cemented with conventional glass ionomer cement. 1 Perhaps one of the more confusing aspects of using ceramic crowns is the decision of whether or not to bond the restoration, followed by the clinical steps involved to either conventionally cement or bond the ceramic restoration. Ceramics have become the material of choice for indirect restorations, with one of the nation’s largest laboratories reporting that 90% of their indirect restorations were fabricated from ceramic.
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