Material Considerations When Restoring Dental Implant Cases

By crevis / Stock.Adobe.com

When restoring a patient's teeth with implants, many considerations go into the decision, from esthetics to the implant location to the patient's health history and habits. You might even need to match previous implant work in the surrounding dentition. Here's what we found when we took a closer look at material considerations when restoring implant cases.

The first decision you encounter in the implant case is not material-based, however. Clark Damon, DDS, a private-practice dentist in the Amarillo and Dallas metro areas and a lecturer for Nobel BioCare and Neodent® for Straumann, says the first decision dentists should make placing implants is whether they are going to have a cement-retained restoration or a screw-retained restoration. Dr. Damon uses screw-retained 97 percent of the time because research shows a higher failure rate for cement-retained than screw-retained. 

"We know that at the junction around the soft tissue, implant, and abutment, cement can get down in the sulcus and get too far down, so the practitioner can't remove it," Dr. Damon says. "So that's the first step."

DDS Lab published a free eBook in 2017 that explains a few considerations when choosing between cement- or screw-retained implants: retrievability, peri-implant tissue maintenance, ease-of-use, and whether it is suitable for angled implants.¹

1. Retrievability. Screw-retained is the most predictable for crown replacements. Removing cement-retained crowns, particularly in multi-unit cases, are far more difficult to remove.
2. Peri-Implant Tissue Maintenance. If cement goes too far subgingival for a dentist to remove, it can cause complications in the surrounding tissue. Screw-retained does not have this problem.
3. Ease-of-use. Cement-retained implants are less technical to place than screw-retained implants. In multi-unit cases, screw-retained often have extra steps when compared to cement-retained versions.
4. Suitable for angled implants. If the angle of the implant is off, it can be easier to use cement-retained crowns over the more expensive, angled, screw-retained abutment needed with screw-retained implants.

Once you have chosen the implant retention style, Dr. Damon says practitioners should choose what implant design they will use. Will it be an abutment and then a crown, or will the crown and abutment be all in one piece? Here is the first material consideration, Dr. Damon says, depending on which direction you go. Zirconia abutments are somewhat out of favor except in a few situations.

"Zirconia abutments can be utilized in the anterior region only, in my opinion. They're prone to fracture, so zirconia is a weak material when it's small or thin and engaging with the internal aspects of an implant," Dr. Damon explains.

DDS Labs supports Dr. Damon's opinion that zirconia abutments are best in the anterior. However, they recommend them also recommend using zirconia when the patient's gingival tissue is thin. When a patient doesn't have a lot of gum tissue to hide it, titanium can show through, giving the implant a grayish hue. DDS Labs also asserts that the zirconia is less prone to plaque accumulation than titanium. Moreover, it also suggests that the tissue surrounding zirconia may heal faster than it would around titanium.²

John Carson, DDS, writes on the Spear Education website that when choosing between zirconia and other types of materials for the abutment, you should ask the following two questions:

1. Can I achieve the esthetic result I need to using something other than zirconia? If yes, then he says you should use another material to get the benefits of more substantial material.
2. Can I minimize the amount of force exerted on the abutment? If you can, then use zirconia, he says, but make sure you minimize those forces as much as possible.

If you determine that you need a zirconia abutment, he writes, then you need to decide whether or not you want a hybrid-style or fully-monolithic zirconia abutment. Carson prefers the hybrid-style abutment, especially when combined with the fabrication of a tall titanium base. The retention gives the zirconia structure and decreases in fracture risk.³

To read his entire opinion on zirconia abutments and the case details that helped form it, visit here.

Dr. Damon does many full-arch and multi-unit cases in his practice. In full arch cases, Dr. Damon says they should be screw-retained 100 percent of the time because it allows you to unscrew the prosthesis if a problem is encountered and also for hygiene purposes—if you are using an acrylic–titanium prosthesis. Dr. Damon says his practice has fewer implant failures when they place the implant and abutment simultaneously. Moreover, at the try-in, the long junctional epithelial attachment to the abutment and implant is stable. Also, because there are multiple steps in finalizing full arch cases, screw-retained implants allow you to screw the temporary and subsequent versions more easily. 

Once you have established your type of implant and the design, it's time to choose the crown material. Usually, this decision requires consideration of strength and durability depending on where the implant is in the patient's mouth and the material's cost. Materials available include porcelain, ceramic, zirconia, metal, composite resin, or a combination of materials, like a porcelain fused to metal crown, among others. Each material has its pros and cons, and some are better for different areas of the mouth and patient preference. For example, an all-resin crown is more likely to be temporary than a permanent crown because they tend to wear down over time. A porcelain-fused-to-metal or zirconia crown is considered a permanent restoration.⁴

Dr. Damon says he uses all zirconia in his full-arch cases. There are other options, most notably the traditional titanium bar with an acrylic wrap-around prosthesis with individual denture teeth. However, while the conventional materials are the most affordable, Dr. Damon says they are also prone to breakage. Moreover, even though you can fix the breaks, it doesn't build the patient's confidence in their investment.

"In full arch cases, when patients pay big money, that is not a practice builder," Dr. Damon says of the breaks.

Dr. Damon likes zirconia for his restorations. Moreover, improvements to the materials mean that it looks good and wears strong.

"There is a lot more translucent and more realistic-looking zirconia to where you don't have to use two different materials," Dr. Damon says, referring to the practice of putting zirconia in the posterior and switching to Emax in the anterior.

Moreover, Dr. Damon likes to do his all-on-four fixed restoration cases with full-thickness zirconia without cutbacks except in the pink porcelain area. For the gingival porcelain, Dr. Damon’s practice uses GC America’s GC Initial porcelain, and, for the teeth, they use a product called MiYo stain from Jensen Dental.

"The MiYo stain and glaze technique adds a lot of depth to the restoration without having to do a cutback," Dr. Damon explains, adding that cutbacks on the teeth increase the chance of chipping.

Dr. Damon and the team have been doing Full Thickness-zirconia without a facial cutback on the teeth, for nearly five years. He would advise another practitioner and their lab to ensure that the zirconia they use is intended for a full arch restoration. The flexural strength should be over 1100 MPas.

"Anything less than that will be prone to fracture and breakage," Dr. Damon says.

Dr. Damon says that when choosing materials for implant restorations, dental professionals should choose a material that will build their practice, one that will be predictable and save the practice money. Selecting a material that you can't repair quickly, for example, can be a significant problem later. For example, studies show that with the acrylic titanium prostheses, 20 percent have a break. The hassles surrounding repairs can burden a practice, Dr. Damon says.

"If you have ten patients in your practice with all-on-four with acrylic titanium prosthesis, two of them are going to break off a tooth. That's going to be two days of headaches for the typical general practioner. It going to wreck your schedule, and now you've got to coordinate with the lab guy to come out," Dr. Damon explains. "It's going to be two days of wrecked production for the average GP."

"So choose a material that is going to improve the patient experience, be more predictable and less problematic," Dr. Damon continues. "And I would say that is full-thickness zirconia."

References

1. The Ultimate Guide To Dental Implants. DDS Lab, Inc.; 2017:7-12. https://go.ddslab.com/the-ultimate-guide-to-dental-implants?hsCtaTracking=b4fde3a0-12e1-4264-b719-3b69c2f25f1d%7C05673b60-580d-4d9e-bc35-ca2907ca3e9e. Accessed February 5, 2021.

2. Sahwil H. ADVANTAGES OF ZIRCONIA IMPLANT ABUTMENTS. Blog.ddslab.com. https://blog.ddslab.com/advantages-of-zirconia-implant-abutments. Published 2017. Accessed February 11, 2021.

3. Carson J. Zirconia Abutments and When to Use Them - Spear Education. Speareducation.com. https://www.speareducation.com/spear-review/2020/03/when-to-use-zirconia-abutments. Published 2020. Accessed February 11, 2021.

4. Larson J. Dental Crown Types, Procedure, When It's Done, Cost, and Aftercare. Healthline. https://www.healthline.com/find-care/articles/dentists/dental-crown#types. Published 2019. Accessed February 11, 2021.