What material is the best choice for a short span fixed partial denture?
From Dr. Berge Wazirian, Prosthodontist, Clinique de Prosthodontie & McGill University
With the advancement of dental technology, dentists today are confronted with many different options when it comes to choosing a material for fixed partial dentures (FPDs). The wide array of materials range from multilayered systems to monolithic systems.
Monolithic methods include:
1. Full contour metal restorations
2. Full contour zirconia restorations
3. Full contour lithium disilicate restorations (i.e. E.max)
4. Full contour Lucite reinforced restorations (i.e. Empress)
Multilayered methods include:
1. Ceramo-metal restorations
2. Ceramo-zirconia restorations
3. Layered lithium disilicate restorations (i.e. E.max)
4. Alumina based restorations (i.e. In Ceram, Procera)
The most commonly seen systems in the market today are ceramo-metal, ceramo-zirconia, full contour or layered lithium disilicate and more recently full contour zirconia restorations. Unfortunately, no system is best for every application, which underlines the importance of clinical judgment in material choice.
The gold standard material for FPDs is ceramo-metal with long-term survival rates ranging from 94.6% at year 5 to 70.8% at year 20 (Backer et al).
The number of published studies for ceramo-zirconia materials is limited because of the relatively short time zirconia has been introduced to dentistry. These studies have a follow up times ranging from 2 to 5 years and low sample sizes. A recent systematic review by Raigrodski et al. showed that ceramo-zirconia restorations have a survival rate ranging from 73.9% to 100% up to 5 years.
The most common technical complication with zirconia FPDs is chipping of the veneering ceramic. Recent studies show that this may be due to a difference in coefficient of thermal expansion (CTE) between the layering ceramic and the zirconia core or the too rapid cooling of the restoration when removing it from the porcelain furnace. More development of veneering ceramic with a CTE similar to zirconia and understanding proper cooling rate is needed. Anatomically designed framework also lowers the proportion of chipping.
Lithium disilicate FPDs have even fewer studies, so conclusions on their longevity are more difficult. Makarouna et al. found survival probabilities of 63% for 6 years with 3 out of 15 FPDs presenting with framework fracture in the connector area. On the other hand, Wolfart et al. showed a survival rate of 93% up to 8 years. In the latter study, the lithium disilicate was used as a monolithic material (no layering ceramic) and all FPDs had a minimal occlusal ceramic thickness of the abutments of 1.5 mm and for the proximal connector the minimal dimensions were 4 mm in height and 4 mm in width (16 mm2) for posterior teeth and 4 mm in height and 3 mm in width (12 mm2) for anterior teeth.
Considering the information presented above, my selection for the correct material would be based in part on the following factors:
• Location of missing tooth: occlusal forces are higher in the posterior area, especially in the second molar area.
• Interocclusal space: All ceramic materials require larger connector size to avoid catastrophic failures therefore they necessitate larger interocclusal space.
• Parafunctional habits: Patients presenting with obvious signs of bruxism and/or clenching should not receive all ceramic restorations.
• Esthetic demands: All ceramic materials offer more esthetic restorations.
• Allergies: Patients who present with certain allergies to metal might benefit from all ceramic materials.
In conclusion, it is imperative to decide which material to use based on clinical factors related to each patient. This decision needs to be made during the planning phase because each material behave differently and might require specific preparation design that will enhance and ensure a predictable long term survival.
1. Wolfart, S. (2009). Clinical outcome of three-unit lithium-disilicate glass–ceramic fixed dental prostheses: Up to 8 years results. Dental materials, 25, e63-e71.
2. Backer, H. D. (2008). Long-term Results of Short-Span Versus Long-Span Fixed Dental Prostheses: An Up to 20-Year Retrospective Study. The International Journal of Prosthodontics, 21 (1), 75-85.
3. Heintze, S. D. (2010). Survival of Zirconia- and Metal-Supported Fixed Dental Prostheses: A Systematic Review . The International Journal of Prosthodontics, 23 (6), 493-502.
4. Makarouna, M. (2011). Six-Year Clinical Performance of Lithium Disilicate Fixed Partial Dentures . The International Journal of Prosthodontics, 24, 204-206.
5. Raigrodski, A. J. (2012). Survival and complications of zirconia- based fixed dental prostheses: A systematic review. The Journal of Prosthetic Dentistry , 107 (3), 170-177.