Circuit 4, station 4

The Longevity of Restorations
Dental restorative materials are essential for restoring teeth to their original function and aesthetic appearance. When selecting a material for restoration, the longevity of the material is one of the most important factors to consider. We will examine the determinants of restoration longevity and explore the various types of restorative materials used in direct and indirect restorations.
Factors Affecting Restoration Longevity
Restoration longevity is influenced by various factors, including:
• caries index
• restoration size
• tooth position
• clinician variables
• patient parameters
A high caries index is associated with low restoration longevity, while larger restorations have a greater failure rate due to their greater surface area. Tooth position is also a factor, molars have lower restoration survival rates than anterior teeth due to their larger size and greater occlusal forces. Experience also matters, with more experienced clinicians having higher restoration survival rates.
Aside from these factors, patient parameters may also play a role. Older patients tend to have their restorations replaced more frequently. However, caries incidence is higher in the elderly due to changes in their stomatognathic system, impaired motor function, and reduced salivary flow rates, among other factors.
How Long Should Restorations Be Expected to Last?
Direct Restorations
• Amalgam: Amalgam is one of the most commonly used restorative materials in posterior teeth. However, due to the higher aesthetic demands of patients and their concerns over mercury toxicity, its use is declining. The median survival time of amalgam has been estimated to be 22.5 years, with annual failure rates of 3%.
• Composite resin: Composite resin is another commonly used direct restorative material. Early composite resin materials showed 50% failure rates after 10 years, but newer products have drastically improved. Hybrid composites performed the best, with annual failure rates of 1.5-2% due to restoration fracture. Polymerisation shrinkage and stress can initiate failure at the composite-tooth interface.
• Glass ionomer cement (GICs): GICs are an excellent choice for managing dentinal caries, but they lack the physical properties needed for posterior restorations. GICs have a 93-98% survival rate in primary teeth, while in permanent teeth, their median survival is 30-42 months. However, when used alone as a restorative material, the annual failure rate is estimated to be 7%.
Indirect Restorations
• Gold crowns and inlays: Gold crowns and inlays are considered the “gold standard” against which all other restorations are measured. They have a survival rate ranging from 96% over ten years, 87% over 20 years, to 74% over 30 years, with a mean failure rate of 1.4% in the permanent posterior dentition.
• Porcelain fused to metal (PFM) crowns: PFM crowns have a 97% 10-year survival rate, with the majority of failures occurring in the anterior region.
• All-Ceramic Crowns: There are different types of all-ceramic crowns, including heat-pressed reinforced ceramics, slip-cast glass-infiltrated ceramics, and metal oxide ceramics. Heat-pressed reinforced ceramics, such as IPS Empress I, are durable and strong, with a 99% survival rate after 3.5 years, making them suitable for anterior restorations. Slip-cast glass-infiltrated ceramics are good for posterior restorations as they are strong and have a 92-100% survival rate over five years. Metal oxide ceramics are tough and resistant to fractures, but their aesthetics are compromised due to their inherent opacity.
• Ceramic Inlays and Onlays: IPS-Empress inlays and onlays have a 96% survival rate after 4.5 years and a 91% survival rate after seven years. CAD/CAM technology has improved the precision of these restorations, resulting in high clinical success rates.
• Fixed Partial Dentures (FPDs/Bridges): Fixed partial dentures, also known as bridges, can be divided into porcelain-fused-to-metal (PFM) and all-ceramic types. PFM bridges have a 92% survival rate over ten years and a 75% survival rate over 15 years, while all-ceramic FPDs have an 89% survival rate over five years.
• Resin-bonded fixed partial dentures or Maryland bridges: The longevity rates for these types of restorations vary widely, with some studies showing 88% five-year survival rates, they can be a viable option for certain patients. Keep in mind, they are mostly lost due to de-bonding.
Another restoration option to consider is the use of the sandwich technique when restoring endodontically treated teeth. This involves using a glass ionomer base covered with overlying composite resin to minimise coronal leakage.
Conclusion
When selecting a restorative material, the longevity of the material is a critical factor to consider. Various factors affect the longevity of restorations, including caries index, restoration size, tooth position, clinician variables, and patient parameters. So, it’s important to communicate effectively with patients so that they can make informed decisions about their treatment.