Table 2.

Material and technical factors influencing the selection of an indirect restoration

Material	Advantages	Disadvantages	Survival rates	Considerations	Preparation techniques
Metal-ceramic	Acceptable aesthetics High strength and toughness Good support for veneering porcelain Low cost Well-established technique	Not usually as aesthetic as all-ceramic options (lack translucency) Metal can show through cervically, or if the porcelain chips Exposed opaceous porcelain can wear opposing teeth	79% - 20 yrs62	Most common posterior crown material due to strength, aesthetics and cost Suitable for most patients, including those with bruxism May use polished metal surfaces on high-wear areas	Traditional preparation Requires adequate reduction for both metal and porcelain layers in areas of aesthetic need
Zirconia monolithic or layered/veneered	Good aesthetics (esp. layered/veneered options) Strongest and most fracture-resistant ceramic (flexural strength ~1,200 MPa) Low plaque accumulation Biocompatible and tissue-friendly (polished, unglazed)	Layered/veneered zirconia prone to chipping and micro-cracks (esp. with reduced core support or in bridges) Can be more difficult to adjust and polish	97.3% - 5 yrs (zirconia-based)68 97.4% - 5 yrs (metal-based with over-pressed veneers)68	Monolithic zirconia preferred for ETPT due to reduced risk of chipping More studies needed with larger sample sizes and longer follow-up periods to provide definitive longevity	Traditional preparation (may be able to use more minimal techniques eg vertiprep60 or ‘biologically oriented preparation technique'61 - but only very limited evidence available for the efficacy of these)
Glass ceramics: lithium disilicate (eg IPS E.max) leucite-reinforced (eg IPS Empress)	Excellent aesthetics - translucency mimics natural teeth Can be used both anteriorly and posteriorly Conservative preparations possible	Lower fracture resistance than zirconia, esp. posteriorly May not be suitable for patients with bruxism or parafunctional habits	97.1% - 11 yrs (IPS Empress II and IPS E.max Press)70	Suitable for ETPT in specific cases with high aesthetic need Survival rates may vary between materials Careful case selection is important	Traditional preparation Adequate reduction needed to accommodate chosen material with adequate strength
Gold	Long survival times Excellent wear resistance Conservative preparations - strong in thin sections Biocompatible and tolerated by gingival tissues Does not wear opposing teeth Easily adjusted and polished	Compromised aesthetics Increasingly a loss of technician expertise High cost	Very high survival rates at 30 years55 70% - 20 yrs (gold crowns)74	Excellent option for non-aesthetic zones, esp. in parafunction May be a good choice for patients with limited interocclusal space	Traditional preparation Specific finishing margin requirements for optimal gold adaptation