Submitted by Dr Seamus Sharkey.

JIDA_Apr-May2015_X_JIDA

FIGURE 1: Old metal ceramic crown on UR1.

FIGURE 2: Veneer preparation on UR3 and UR2,4 – Emax crowns

FIGURE 2: Veneer preparation on UR3 and UR2,4 – Emax crowns

 

 

 

 

 

 

Permanent cementation and bonding of indirect restorations:

  1. List four main functions of modern cements.
  2. When selecting a dental cement, a number of considerations need to be taken into account such as:
    –    the resoration itself;
    –    the cement; and,
    –    the clinical scenario.
    List two factors for each of the above categories that need to be considered.
  3. Two main categories exist for modern cements – water-based and polymerising. Give two examples of each.
  4. Although a myriad of factors can affect the choice of dental cement, what type of cements are, in general, suitable for the following restorations:
    A    metal ceramic or full coverage metal restorations (Figure 1);
    B    partial coverage restorations – onlays, inlays;
    C    ceramic veneers (Figure 2);
    D    all-ceramic crowns (Figure 2); and,
    E    resin-bonded/Maryland bridges.

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Answers

 

JIDA_Apr-May2015_X_JIDA

FIGURE 3: Metal ceramic crown UR1 and UL2 – implant crown.

JIDA_Apr-May2015_X_JIDA

FIGURE 4: Ceramic veneer on UR3 and UR2,4 – Emax crowns.

 

 

 

 

 

 

1.    Modern cements:
–    seal the restoration tooth interface;
–    provide a predictable level of retention;
–    compliment the optical properties of the restoration; and,
–    reinforce or strengthen the restoration.

2.     Restoration – material properties, marginal fit, type of restoration and surface-conditioning method.
Cement – viscosity, biocompatibility, adhesive potential, solubility, water uptake, colour stability, wear resistance,     working and setting characteristics, sealing ability, and radio-opacity.
Clinical – occlusion, preparation design, moisture control, type of build-up material, type of supporting tooth structure, surface roughness, margin location, tooth location, and amount of tooth destruction.

3.     Water-based – glass ionomer cements (Ketac Cem), zinc phosphate (Flecks) cements, polycarboxylate (Durelon).
Polymerising – resin-modified glass ionomers (Rely X, Fuji plus; an intermediate with elements of water-based and elements of polymerising), BisGMA resin cements (NX3, Variolink, Rely X Unicem) and phosphate resins (Panavia).

4.     A. Metal ceramic or full coverage metal restorations (Figure 3):
Providing basic retention and resistance form are satisfactory, then any water-based or polymerising cement will work. For teeth with inadequate preparation height or resistance form, adhesive cements are recommended.
B. Partial coverage restorations – onlays, inlays:
For metal-based restorations the same principles apply as full coverage. For ceramic inlays/onlays, adhesive-based cements show double the success rates of water-based (Van Dijken et al., 1998, and Gemalmaz et al., 2001).
C. Ceramic veneers (Figure 4):
Adhesive resins only, with particular attention to the correct surface treatment of both the tooth and restoration.
D. All-ceramic crowns (Figure 4):
Dependant on the type of crown used.
Particle-filled glass ceramics (Empress, E-max) can be etched and show greater strength and increased success rates with adhesive cements bonded (Malament and Socransky, 2001). Polycrystalline ceramics (zirconia based – Procera, Lava and Alumina based) can’t be etched or sandblasted effectively, and clinical studies show that there is no significant difference between water-based and polymerising cements (Galindo et al., 2006). However, water-based cements may be best avoided since water promotes crack propagation.
E. Resin-bonded/Maryland bridges:
Adhesive resins only, with particular attention to the correct surface treatment of both the tooth and restoration.