Who Takes Care of Your Work?

Dental hygienists' primary job is to preserve tooth structure, and dental technicians' job is to replace it. However, what about preserving that replacement material? Dental hygienists typically do not receive substantial education in school or CE courses on indirect restorative materials and how they differ from natural dentition. Dental technicians, meanwhile, rely on their knowledge of form and function as well as materials and technique to produce a durable product. However, certain dental hygiene protocols and precautions—both in the chair and at home—can help to maximize the longevity of dental restorations.

"Knowing more about the materials and strategies currently being used restoratively would allow the hygiene community to tailor our clinical patient care to best serve those patients," Vyprynyuk says. "Knowing the logistics of what the restoration is made of, how durable it is, how strong it is, how easily it will pick up stain, and what toothpaste is best to use can make a significant difference. Even the construction of the restoration is noteworthy—a single unit is relatively straightforward, but with multiple units, such as a long-span bridge, different methods may be preferable for maintaining hygiene around them. The laboratory can create a wonderful restoration, but if the dental hygienist and the patient do not know how to best maintain it, the outcome may not be ideal."

The instrumentation and techniques utilized by dental hygienists in the dental chair can impact the success of a restoration in some cases; in others, they may be inconsequential. For example, one study indicated that the surface roughness of zirconia, alumina, and lithium disilicate is increased more after treatment with steel curettes than with titanium curettes.¹ "I watched my own hygienist use the same scalers and procedures for crowns and regular teeth in my mouth; she may not have been aware that some scalers can create scratches on the restorations," Budny says. "Scratches cause bacteria, biofilm buildup, and eventually plaque that can destroy the tissue and surrounding structures." Another study found that ultrasonic scaling significantly changes the surface integrities of lithium disilicate and zirconia, and that surface polishing with a multi-step intraoral kit after repeated scaling is effective for zirconia but not lithium disilicate.² "It looks like someone drew on the restorations with a carpenter's pencil," says prosthodontist M. Reed Cone, DMD, MS, CDT, FACP, owner of Nuance Dental Specialists, in Portland, Maine.

Conversely, while a common belief has been that titanium implant abutment surfaces should not be instrumented with metal instruments due to scratching of the surface, research has indicated that titanium abutments undergo less scratch damage during scaling with a metal curette than cementum does.³ Another study measured microleakage around zirconia crown margins cemented with self-adhesive resin and resin modified glass ionomer cement after piezoelectric ultrasonic scaling, and found that it did not increase for either one.⁴ "There are certain protocols that we follow, but those change frequently," Vyprynyuk says. "We were not allowed to use stainless steel probes to measure the depth of the pockets around implants, but now we are told that it is safe."

Literature has suggested caution or complete avoidance of air polishing with NaHCO₃ on composites and porcelain veneers.⁵ Pinhas Adar, CDT, MDT, says he recommends that for all restorations. "Air prophy jet treatment on a dental restoration will break the final finish, and it will start staining faster," Adar says.

Vyprynyuk notes that the pink disclosing solutions that hygienists use to identify plaque may stain some restorative materials. Furthermore, she says the absence of plaque on a restoration may need to be considered contextually with certain materials. "We know that many restorations do not pick up plaque and bacteria in the same way that natural teeth do," she says, "so we need to be mindful that if we do not see a lot of plaque around the restoration, that is not necessarily an indication that the patient's oral hygiene is great." Budny notes that not only do popular materials such as zirconia and lithium disilicate continue to evolve, but entirely new materials such as 3D printing resins for permanent crowns are hitting the market constantly. "Materials are evolving so quickly that staying on top of them is difficult," she says.

Even if the patient practices exceptional home care, the wrong toothpaste could impact their restorations. One study indicated that charcoal toothpaste affects color and gloss stability when applied to ceramic stain and glaze on feldspathic porcelain, lithium disilicate, and zirconia; the same study also found that glass-phase ceramics retained stains longer than zirconia ceramics.⁶

Joshua Polansky, MDC, owner of Niche Dental Studio in Voorhees Township, New Jersey, says he asks dentists to recommend toothpastes with low to medium relative dentin abrasion (RDA) values when he provides restorations. "A toothpaste with a high RDA can remove stain and glaze over the years," Polansky says.

Cone suggests recommending 10% carbamide peroxide bleach for any patient with restorations. While bleach is more commonly known for its whitening capabilities, its hygienic impact is proven as well.⁷ "It is the most underutilized product in dental hygiene," Cone says. "It is so safe and effective. It keeps the mouth free of bacteria during the contact time and cleans the tissue. It gets underneath any bridgework. Because it is so low-grade, it can be worn for up to 10 hours, at which point it simply becomes ineffective; the patient cannot do damage by wearing it for too long."

Communication between laboratory and dental hygienist on every case is unrealistic. "If I see 15 patients every day, I cannot call the laboratory every time one of them gets a new restoration," Vyprynyuk says. "However, if there are new products or materials being used, a lunch-and-learn could help. The laboratory can explain how to communicate to patients regarding these products, how to avoid scraping them, what type of non-abrasive polishing paste may be necessary, etc. Some general communication periodically would go a long way toward achieving our shared goal of working for the good of the patient population."

Budny adds that laboratories could provide training sessions on best practices for scanning, shade taking, photography, and other relevant tasks that are often delegated to the hygienist. She also suggests sending an information sheet with each restoration, specific to the material(s) used. "This would be a value-added service as well as a great advertisement for the laboratory," she says.

Communication and education can go both ways, of course. Budny suggests that technicians would benefit from learning more about oral diseases and the oral environment as a whole. "What kinds of diseases, conditions, and actions can impact restorations?" she says.

Cone says hygienists should not hesitate to note to the dentist when a restoration or prosthetic should be modified in order to allow for better hygiene. "With any fixed restoration," he says, "I want the patient to demonstrate before leaving the office that they can floss properly. If they cannot, I relay to the laboratory, for example, that an embrasure needs to be opened 1 mm to 2 mm to allow for flossing. I may even include photographs or draw on a PMMA prototype with a marker." Cone also cautions against accepting a bridge with a ridge-lap pontic. "A ridge lap almost guarantees that food will get trapped under that pontic," he says. "To remedy this, we can request either an ovate pontic site or a modified ridge lap that looks like a full tooth on the facial side but is more open on the lingual. Laboratory technicians have never had to carve out calculus and plaque from around restorations, so communicating with them to avoid these problems is important."

Meanwhile, the patient's role in the communication chain becomes important if they visit a new practice. "The goal is always to make our restorations lifelike, but that can lead to a new hygienist not recognizing them," Cone says. "I always advise my patients that if they visit another dental practice while spending the winter in Florida, for example, they need to tell the hygienist about their implants and restorations so the appropriate instrumentation can be used."

As much as their job descriptions may seem to be almost antithetical, dental hygienists and dental technicians can mutually benefit from open lines of communication, even if infrequent. "There are parallels between dental hygiene and dental technology because the overarching goal of both is to improve the patient's oral health," Budny says. "While much of what we do does not overlap, dental hygienists do establish oral hygiene habits preventing the formation of biofilm and disease in surrounding teeth, restorations, and implants—something that may be unfamiliar to many technicians but that affects their work. Our mission is to produce dental restorations that will replace broken or missing structures in the oral environment, and to make them last. That last part is somewhat missing, because we provide these beautiful restorations, but we are not involved in what happens to them after placement."