This is the second installment of a short series that shares clinical insights into successfully restoring dental implants using cement-retained prostheses. Appearing in August, Part 1 (available here) explained factors that influence the success of these types of restorations and addressed considerations for the cement margin site. This article will cover the importance of proper cement selection and impact of a material’s radiodensity.
HABIT 3: CEMENT SELECTION
While dental cements are available in a variety of formulas, almost all have been developed for natural teeth. The chemical formulation often fulfills the dentition’s needs; for example, the addition of fluoride affects the microbial flora and alters remineralization to reduce caries risk and lesion development. Similarly, glass ionomer adheres to dentin, and hydroxyethyl methacrylate (HEMA) is used as a dentin bonding agent when combined with acrylic polymers. However, implants are not susceptible to caries and have no enamel to remineralize or dentin for bonding.
Additionally, some of the constituents of cement can negatively affect implants. For instance, fluoride ion — found in glass ionomer and added to other dental cements, such as polycarboxylates — is associated with titanium corrosion,1 a leading cause of implant failure. What’s more, the effects of fluoride against Streptococcus mutans and Lactobacilli cariogenic pathogens may be irrelevant, as these bacteria are not associated with peri-implant disease. Another consideration is that HEMA can cause allergic responses, especially when it contacts the mucosa (which is the peri-implant sulcus).2
Ironically, some cements specifically designed for implant restorations have been shown to cause early peri-implantitis, possibly due to their ability to support growth from known pathogens, such as Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis or Fusobacterium nucleatum.3,4
Cements containing zinc have some benefit when cementing implant restorations. Both zinc oxide eugenol and zinc phosphate have an anti-inflammatory effect, inhibit peri-implant pathogens, are easy to remove from titanium surfaces, and do not promote corrosion (provided fluoride is not an additive).3 More importantly, they rank among the most radiodense cements, which allows radiographic detection of subgingival excess cement.5 One problem with zinc cements is they may not provide adequate retention for some restorations, so abutment modifications may be required. This is easily accomplished through air abrasion, acid etching or abutment adjustments, such as internal venting.6
A key point to realize is the ideal implant cement does not yet exist. Every cement has positive and negative attributes. What is vitally important is control of the cementation process (i.e., amount, application, and seating process), abutment design, cement margin location, and material used.
EVERY CEMENT HAS POSITIVE AND NEGATIVE ATTRIBUTES
HABIT 4: ROLE OF RADIODENSITY
Unless a surgical approach is utilized, visual access to subgingival areas is usually limited, which makes the ability to radiographically detect excess cement a highly desirable property.
The standard measure of radiodensity compares X-rays of a 1-mm-thick cement disc with a medical-grade aluminum wedge. In this system, 100% radiopacity indicates a 1-mm-thick layer of cement yields a similar radiographic image as 1-mm-thick aluminum, while 200% radiopacity equates to 1 mm cement thickness appearing similar to a 2-mm-thick aluminum sample.5
In general, the author recommends cements used for implant restorations have a minimum radiodensity of 300%. For comparison purposes, zinc cements offer radiopacity of 600% to 700%, whereas some of the acrylic cements provide as little as 100% to 200%.5,7
Radiodensity is important because excess cement can lead to peri-implant disease and implant failure, so a thorough radiographic evaluation is imperative. When restoring natural teeth, any excess cement usually flows from local sites, whereas specific patterns have been identified with subgingival cement extrusion from restored implants. Here, excess flow adopts a circumferential radiological pattern — like a halo — surrounding the abutment. Radiologists call this the “eggshell effect,” and it requires access 360 degrees around the implant restoration for cement removal.7 Thus, every attempt should be made to limit excess cement when restoring implants.
Future installments will cover additional considerations for the successful restoration of dental implants using cemented appliances.
- Agha A, Parker S, Parkinson EK, Patel M. Characteristics of experimental resin-modified glass-ionomer cements, containing alternate monomers to HEMA. Dent Mater. 2021;37:1542–1552.
- Avinash KVN, Reddy V, Shetty J, Nitin HC. Evaluation of the effect of fluoride-containing luting cements on titanium and its effect on the shear bond strength. Contemp Clin Dent. 2019;10:47–51.
- Korsch M, Walther W, Bartols A. Cement-associated peri-implant mucositis. A 1-year follow-up after excess cement removal on the peri-implant tissue of dental implants. Clin Implant Dent Relat Res. 2017;19:523–529.
- Raval NC, Wadhwani CP, Jain S, Darveau RP. The interaction of implant luting cements and oral bacteria linked to peri-implant disease: An in vitro analysis of planktonic and biofilm growth — a preliminary study. Clin Implant Dent Relat Res. 2015;17:1029–1035.
- Ramer N, Wadhwani C, Kim A, Hershman D. Histologic findings within peri-implant soft tissue in failed implants secondary to excess cement: report of two cases and review of literature. N Y State Dent J. 2014;80:43–46.
- Wadhwani C, Hess T, Faber T, Piñeyro A, Chen CS. A descriptive study of the radiographic density of implant restorative cements. J Prosthet Dent. 2010;103:295–302.
- Wadhwani C, Rapoport D, La Rosa S, Hess T, Kretschmar S. Radiographic detection and characteristic patterns of residual excess cement associated with cement-retained implant restorations: a clinical report. J Prosthet Dent. 2012;107:151–157.
From Decisions in Dentistry. September 2022;8(9)20.