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November 21, 2008

PART 10 of 10

The last article of this series focuses on something entirely new. Before I start, though, I want to take a minute to thank everyone for following this information on minimal intervention so closely. I would especially like to thank those who took the time to write me. No one is on this road alone, and unless we share and work together, we're sunk.

This series is a work in progress, as mentioned in a previous issue. It's important to keep new material and ideas in a central location in the office.

Something that has been omitted from the dental hygiene perspective is a look at crown-and-bridge cements. Although a dental hygienist usually thinks of cement only when a blob is forgotten, its composition can contribute to a number of dental hygiene issues, such as sensitivity, soft tissue irritation and/or swelling, and bleeding. Every clinical dental hygienist out of school for more than a few weeks has seen cases where any of these cases presented as a consequence of a new crown. Sometimes it's not the crown; it's the cement.

The dentist must take several factors into consideration. The patient's age, the tooth's location, the prognosis for the restoration, and the diagnosis of the condition that prompted the restoration are all factors in creating the best treatment plan.

Obviously, the diagnosis is first. Why does the tooth need a crown? A tooth broken from a car or bicycle accident creates one set of treatment options, somewhat different from a tooth that is broken due to a restoration with a wide isthmus. A crown for someone with Sjögren's will have a different diagnosis than someone with a cosmetic outlook.

An evaluation of the patient's saliva is important before providing this kind of treatment. Low pH or poor buffering will shorten the prognosis of the restoration. That issue should be addressed concurrently. A glass ionomer cement may be best in these circumstances. What that means to an oral health-care provider is that the biomimetic nature of glass ionomer is the most like a tooth and it does not contain or emit bisphenol-A, which was recently in the news.

From the hygienist's perspective, the glass ionomer's biomimetic nature will be the kindest to the soft tissue it comes in contact with. The fluoride release also makes it harder for recurrent decay to take place. Because fluoride is not a structural component of the material, and because it recharges with fluoride from the environment, it's a great cement for patients with a high risk for caries.

Beware the advertisement for fluoride in non-glass ionomer cements. Sure, it sounds good. Manufacturers strive to insert fluoride into various products in response to a profession still clinging to fluoride as the primary way to treat caries. Charts that describe different attributes of competing products will list fluoride as a column heading. The truth is that fluoride release is what we're looking for, not merely containing fluoride.

Fluoride doesn't contribute to the strength of dental materials. It doesn't have bactericidal properties, or tooth-strengthening properties in this application. Remember back to our dental materials classes? We can recall that very little fluoride is released from resin materials.

Indirect restorations, such as inlays and onlays, that are cemented properly have a very thin line of cement open for dental hygiene procedures. Often, the line is only 40 micrometers, which doesn't sound like a lot. A hair is about 75 micrometers. A streptococcus is 0.007 micrometers in size, and a particle of pumice from prophy paste can dig a hole big enough for a biofilm to set up housekeeping in a second.

This can be especially true if the cement is a glass ionomer. What it gains in caries management it loses in the ability to withstand the forces of dental hygiene scalers and spinning pumice. So caution is the word of the day when practicing around this cement.

Sensitivity is an issue that crops up every so often when a tooth is treated with any type of restorative material. Imagine the trauma to the tooth that occurs when it is prepared for an indirect restoration. There are ways to make sure the tooth is not going to suffer from thermal sensitivity. Over-etching, over-drying the tooth before adding the cement, or using too much cement are all ways to create thermal sensitivity.

Every now and again a crown is cemented as part of a dental hygiene appointment and the hygienist is in charge of removing the excess. It's always a good idea to ask about the setting time. Some set quickly and others need a little more time. There's a lot of distress when removing the excess too early and knocking the crown off. Or worse, waiting too long and being unable to remove the clump effectively.

The range in working time is between 1.5 to 2.5 minutes by manufacturer; the setting time is quite another story. That can be up to 10 minutes, usually about four. Using a hand instrument to remove the flash or excess is usually all that's needed. A doubled-up length of floss with a knot in it finishes it off. Snap the floss through the contact and pull it through so the knot catches and smoothes the surface off.

Temporary cements are a whole separate category and have components to help tissue respond well so the cementation goes well. Two (GC America's Temp Advantage and Premier Dental's NexTemp) contain fluoride, chlorhexidine, and potassium nitrate for a healthy tissue and decreased sensitivity. Eugenol is well known as a tooth soother and temptation may be high to use a temporary cement containing it. Chemistry raises its head once again: Eugenol is incompatible with some permanent cements.

Start keeping track of the tissue condition in response to the materials used. You'll learn a lot, and together with the dentist you will find ways to use minimal intervention dental hygiene for healthier tissue.

About the Author

Shirley Gutkowski, RDH, BSDH, FACE is codirector of CareerFusion and a practicing dental hygienist. She is coauthor of the best selling book, "The Purple Guide: Developing Your Clinical Dental Hygiene Career" with Amy Nieves, RDH. She can be contacted at crosslinkpresent@aol.com.

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