Robert A. Lowe, DDS, discusses a new class of materials that are impacting the way dentistry is practiced.
Q: What is bioactivity as it relates to today’s dental materials?
A: For years, bioactivity in dentistry has only been associated with fluoride release and the conversion of hydroxyapatite to its stronger form, fluorapatite. This conversion has helped to strengthen tooth enamel and make it more resistant to acid attack. Fluoridated water and fluoride treatments for young patients have all been helpful in the fight against tooth decay for many decades.
The definition of bioactivity is expanding in our profession via the many new smart dental materials that are emerging into the market. The ability of a bioactive material to contribute calcium and phosphate ions to help rebuild demineralized dentin is the new paradigm. These smart bioactive materials also react to pH changes in the oral environment to elicit changes in the material and the tooth as well. Hence, biomineralization refers to the exchange of calcium and phosphate ions with the tooth substance forming new apatite or, in many cases, repairing existing demineralized apatite. By definition, bioactivity also includes the precipitation of apatite crystals on the surface of the material in the presence of moisture (saliva). It’s not just about fluoride!
Q: What does it mean to have a bioactive luting cement for crown and bridge?
A: We consider a clinically closed crown margin to be 30 to 50 μm where one cannot feel/hear a perceptible click when using a sharp dental explorer. Is that margin really closed? Since bacteria are only about one μm in diameter, a 30- to 50-μm margin would be open enough to allow the ingress of bacteria unless the luting agent permanently occluded that gap. What if there are undetectable gaps in the restorative-tooth interface where there is no luting agent present, perhaps due to a bubble, or tissue tag? Obviously, the chance is very likely for recurrent decay to damage the restoration in that area, particularly if located in the gingival crevice and not visible on a radiograph. There are now bioactive luting agents that are not only insoluble and occlude the marginal gap between the restoration and tooth, but also, when saliva is present, cause apatite crystals to precipitate on the surface of the luting agent to further protect and seal the marginal area. Traditional resin cements do not provide this level of biological protection. Examples of luting agents that are currently on the market which have been shown to have this type of bioactivity are ACTIVA BioACTIVE-CEMENT (Pulpdent), Ceramir Crown and Bridge (Doxa), and BioCem Universal BioActive (NuSmile).
Q: How do bioactive liners affect the way we treat caries?
A: Traditional cavity liners recently used include calcium hydroxide and glass ionomer (GI) cements. Use of calcium hydroxide is contraindicated under composite resins because it interferes with material setting. Many of the light-cured GI liners are resin-reinforced that, depending on resin content, can limit any benefit from the release of fluoride. Bioactive liners that can help replenish the calcium and phosphate ions lost due to acid attack will change the way we treat caries. It is well known that there are 2 types of dentin: infected—demineralized and full of bacteria and affected—demineralized, but bacteria free. Mount et al has well-documented in the literature that affected dentin can be remineralized and turned back into healthy dentin. Affected dentin may be sticky to the tactile touch, but should it be removed? Use of round polymer burs (Smart Bur II [SS White Burs]) that are fabricated at the specific Knoop hardness of healthy dentin can be used to ensure that only infected dentin is removed during the caries excavation process. Placement of a bioactive liner can then help remineralize and rebuild the remaining affected dentin, returning to healthy dentin. Examples of bioactive cavity liners on the market include ACTIVA BioACTIVE-BASE/LINER (Pulpdent) and TheraCal LC (BISCO Dental Products), and both have been shown to exhibit bioactive properties based on the mentioned definition of bioactivity. The calcium silicate chemistry of TheraCal LC enables this material to be used on pulp exposures. Biodentine (Septodont) is a tricalcium silicate material, which can be used as a bioactive build-up material where large areas of tooth structure are missing, and when a pulp exposure or root perforation may exist. While some of these more heroic cases may eventually still require endodontic therapy, there will be many cases that respond favorably thus avoiding an additional procedure and preserving the vitality of the tooth.
Q: What are the advantages of using bioactive as opposed to conventional restorative materials?
A: The advantages are clear after reading the above discussion regarding bioactivity and the effects of rebuilding damaged tooth structure. Having restorative materials that can protect, repair, and help seal the marginal gap will aid in the preservation of the natural tooth and extend the life of the restoration. ACTIVA BioACTIVE-RESTORATIVE (Pulpdent) is one such material, particularly useful for patients with high caries indices. Acidic oral environments can create extensive damage to teeth, particularly if a patient doesn’t know which end of the toothbrush has the bristles! Pediatric patients and primary teeth have their own sets of issues. Finishing a procedure quickly in a less than moisture-free environment makes using traditional composites and adhesives very difficult on pediatric patients.
There is a composite material (Beautifil II and Beautifil Flow Plus [Shofu Dental]) with a Giomer glass filler. While Giomers do not release calcium and phosphate ions, they do release many other basic ions that can help buffer the effects of the acid environment in the oral cavity helping to inhibit plaque accumulation on restorations and at the margins.
Q: What does the future hold for bioactive dental materials?
A: New innovations continue to help to reinforce existing technologies and to introduce new paradigms for treating dental disease and restoring broken dentitions. Restorations and adjunctive materials will no longer just occupy the space between themselves and the surrounding tooth, but will help repair and sustain healthy tooth structure allowing our patients to have a better chance to enjoy a healthy dentition throughout their lifetime!
Dr. Lowe is practicing dentist with Fellowships in the AGD, the International Academy of Dento-Facial Aesthetics, the American Society for Dental Aesthetics, among others. He can be reached via email at boblowedds@aol.com.
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