Dental ceramics are the go-to indirect materials for restoring esthetics and function to a debilitated dentition. There are numerous materials to choose from. And the list continues to expand. Lithium disilicate and zirconia lead the way as primary materials of choice for most practitioners. Strength, appearance and durability are key reasons for material selection.
At insertion, most ceramic restorations require some degree of adjustment to provide functional stability and proper contour. Although these adjustments are necessary, if not done properly, they may contribute some internal flaws and potential ceramic fracture. Leaving a rough ceramic surface may affect wear of the opposing tooth or restoration Polishing techniques and tools are instrumental in smoothing adjusted ceramic and aids and avoiding a catastrophic ceramic crown, veneer or onlay fracture.
Diamonds of various grits are commonly used to begin the porcelain adjustment process. If diamonds are used, the adjustments should be performed extra-orally and with low speed using a fine grit diamond. The speed of bur rotation should not exceed 20,000 rpm. Ideally, 15,000 rpm or less is recommended. 5 Ncm of force is all that needs to be applied to the ceramic during the adjustment. It is impossible to manage and control bur rotational speed with air driven turbines. An electric motor allows for control and reduced speed. I would refer you to the Spear Digest article comparing electric and air turbine handpieces.
Fine grit diamonds leave a rough surface that requires polishing. There are numerous polishing kits on the dental market that utilize a series of points, discs, wheels and pastes that aid in reducing surface roughness and create smooth ceramic surfaces. It is well-documented in the literature that polished ceramic produces less wear on opposing teeth than glazed ceramic. It is imperative that surface scratches be removed following occlusal adjustment.
Brasseler is a well-known supplier in the dental industry for rotary instrumentation. They have a wide selection of products for both tooth reduction and polishing. Their Dialite polishing systems are well-documented. These systems provide a sequenced series of points and discs to attain high polish of anatomical surfaces following occlusal and functional ceramic adjustment. The company has organized the polishing systems according to material. There are specific Dialite polishing systems for Zirconia and Lithium Disilicate. These polishers work extremely well for maintaining anatomy and surface contour.
The new ceramic restorations, such as zirconia and lithium disilicate, have provided dentists with the opportunity to practice more conservative dentistry. Because we are able to bond these restorations predictably, we can now be more conservative in our preparation design. Full crown preparations are no longer necessary, in many cases, to restore tooth cracks and replace larger old restorations with indirect restorative techniques. Partial coverage ceramic onlays are the restorations of choice for these situations. In the Restorative Design Workshop, Bob Winter and I spend an entire day designing and preparing partial-coverage ceramic restorations. This treatment is a tremendous service for the patients, as it conserves tooth structure and provides a predictable restorative solution. Of course, occlusal adjustment is still necessary in many cases. The surfaces are adjusted and polished prior to the bonding of the restoration.
Margins of ceramic partial-coverage restorations are all supra-gingival. Polishing the margins of the bonded ceramic restoration is an important part of managing smoothness and restoring a natural contour and feel of the new restoration. Although the marginal gap of the restoration is minimal, it is important to smooth and polish the transition. I have found that the Brasseler Featherlite polishing wheels are perfectly suited for that procedure. These rubber wheels are diamond-impregnated with varying grits to smooth and polish to a high luster finish. The design of the “feathers” provides a predictable way to smooth the ceramo-enamel junction to be undetectable to an explorer. When used at low speed (4,000 to 8,000 rpm), these wheels are very efficient. I find no need to follow up these wheels with a polishing paste.
There are many techniques, products and materials for finishing and polishing ceramic restorations. All can work, if utilized properly, to create a smooth finish. As Bob Winter routinely says, “it’s good to have options.” I have found these Featherlite wheels are very a good option for managing marginal smoothness in finishing my ceramic partial coverage restorations.
Tools of the Trade: Electric Handpieces For Optimal Precision. Jeff Bonk. 2017. http://www.speareducation.com/spear-review/2017/09/tools-of-the-trade-electric-handpieces-for-optimal-precision
Ceramic Restorations: Predictable Adjusting and Polishing. Bob Winter. 2014. http://www.speareducation.com/spear-review/2014/10/ceramic-restorations-predictable-adjusting-polishing
Online Education - Adjusting and Polishing Porcelain Restorations
Online Education - Adjusting and polishing EMax restorations: https://online.speareducation.com/course/adjusting-and-polishing-emax-restorations
Steiner, Rene, et al. "Adjusting dental ceramics: An in vitro evaluation of the ability of various ceramic polishing kits to mimic glazed dental ceramic surface." The Journal of prosthetic dentistry 113.6 (2015): 616-622.
Lawson, N. C., Janyavula, S., Syklawer, S., McLaren, E. A., & Burgess, J. O. (2014). Wear of enamel opposing zirconia and lithium disilicate after adjustment, polishing and glazing. Journal of dentistry, 42(12), 1586-1591.
Nair, K. Chandrasekharan, and Bheemalingeswara Rao. "Polishing of newer ceramics." President’s Message 7.3 (2017): 82.
Amaya-Pajares, S. P., Ritter, A. V., Vera Resendiz, C., Henson, B. R., Culp, L., & Donovan, T. E. (2016). Effect of finishing and polishing on the surface roughness of four ceramic materials after occlusal adjustment. Journal of Esthetic and Restorative Dentistry, 28(6), 382-396.