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Prosthodontics Restorative Dentistry

What material is the best choice for a short span fixed partial denture?

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From Dr. Berge Wazirian, Prosthodontist, Clinique de Prosthodontie & McGill University

Ceramo zirconia FPDs

Ceramo zirconia FPDs

Ceramo-metal FPD

Ceramo-metal FPD

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.

Bibliography
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.

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6 Comments

  1. Dr John F. Miner January 21, 2013

    Thank you for this abbreviated but comprehensive review. I must admit that I lean towards the Gold Standard mentioned in your article. It is possible to obtain excellent esthetic results and to show no metal but still have all of the benefits of this modality in the posterior region of the mouth. The choice of ceramicist is essential to success with this modality but would be even more essential with the other modalities mentioned not to mention the all important interplay of the intraoral factors and clinician expertise; among others. JFM

    Reply
    1. Interesting point John, I wonder whether or not a study exists comparing the failure rates of the same modality between different ceramicists. It stands to reason that it matters (for instance, one of the biggest factors in dry socket rates with wisdom teeth is practitioner experience), so the same should affect crown longevity. Especially for those where fracture is the most common cause of failure rather than recurrent decay.

  2. Waji Khan January 23, 2013

    Thank you for your insightful review. I have only had two crowns fracture on me in my 12 years of clinical practice and one was a Procera crown which I cemented at around 9am on Sept 11, 2001 with a Prosthodontist colleague of mine and the other was a lithium disilicate crown which only lasted two years. Since this time I have heavily depended upon the gold standard PFM as a result of my experience and the reccomendations of my prosthodontic mentor. I think that there is a good place for the non-metal restorations, however more time and research is required to ensure that they are as strong, have clinical longevity and propose the same dynamic reciprocity that an insert material like gold has; I ,and my hygienists, also have found tissue responses around all ceramic restorations to be less than ideal.

    Reply
  3. Vipul G Shukla January 23, 2013

    In my close to 16 years of practice, I have done fixed units from all gold to full zirconia, but I feel for a short span bridge less than 3-units, milled zirconia layered with custom porcelain on top for aesthetics and better shades is a good choice. Personally, I am a great fan of 3M’s Lava zirconia crown and bridge, because of strength’s close to 1200 Mpa.
    I have done up to 5-unit bridges in one piece, and even 3-units replacing lower 6s, and designed and executed correctly, a layered zirconia bridge can perform same as a traditional PFM in strength, and way better than a PFM with respect to tissue response adjacent to margins.
    There is a reason it is called ‘white steel’.

    Reply
  4. Terry Lim-Prosthodontist January 25, 2013

    A nice review. I would add that Zirconia, although promising, does have a number of drawbacks. Regardless of whether the structural integrity is compromised on a a veneer chip, the fact of the matter is, the ceramic has failed, and the patient tends to be disappointed in the complication. Personally, I rarely do all ceramic FPD’s, and is not my first choice for posterior applications for the following reasons:

    1. Unpredictable for failure, as gold standard is PFM FPD
    2. connector is smaller on PFM, and therefore less bulky
    3. Reduction of the abutments is less on PFM, so the trauma to the tooth is less, and fracture chance is less
    4. Esthetically, PFM can be just as nice, but it is an issue for grey show through at the gingival, a downside especially if you have recession.
    5. You can use a metal occlusal surface for part of all of the occlusal contacting surface, which is kinder to opposing dentition and has no fracture chances for porcelain.
    6. Technical fitting of the metal vs. Zirconia and Empress/Lava seems to be technician dependent, although milling accuracies are outstanding these days. The quality and smoothness of the finishing line, and the accuracy of tissue retraction and margin capture on either a scan or on a traditional silicone impression is the biggest factor for marginal accuracy (with equally good technicians)

    Reply
  5. Esthetics has the highest degree of drive for my practice. No question that PFM’s are the standard.
    However, evvn when done with all of the right conditions – all porcelain (in zirconia) will not disappoint in the short and longer term. PFM restorations will disappoint ultimately (even if the patient does not complain) as soft tissue changes and light tranmission through the restoration are a continual issue.
    On a PFM bridge the problem might be with one retainer. Then what?
    I still do a lot of PFM’s and find them less work. But not in the esthetic zone.
    As far as failures go, it does not seem to be any more of an issue than a PFM. And that is infrequent as well.

    Reply

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