Special Report: Erosion
By Rick Asa
Featured in AGD Impact, April 2007
Pg. 54

Posted on Friday, April 06, 2007

While those who have studied dental erosion for many years continue to deliberate on terminology and the exact causes/origins of the condition, clinicians who see patients every day are considering their options.

The common threads in acid erosion and dental caries are acid and loss of tooth structure. Organic bacterial acids lead to caries. Extrinsic acids in foods and beverages we eat and drink and/or intrinsic acids from our stomachs can lead to erosion. In both cases, early detection and preventive measures can keep an incipient problem from becoming irreversible. And, in both cases, saliva and food consumption patterns play a critical role.

Although erosion may seem like a new dental problem, it’s been around for a while. The first formal textual reference may have been in The Natural History of the Human Teeth by John Hunter (1803), “surgeon extraordinary to the King and fellow of the royal society.” Hunter referred to what is now commonly called erosion as “decay of the teeth by denudation,” which he was careful to differentiate from what we now know as bacterially-induced caries. His observation of subjects’ teeth was that “the whole wasted surface has exactly the appearance as if the tooth has been filed with a rounded file, and afterwards had been finely polished.”

     “Those whom I have known have not been able to attribute this disease to any cause,” he wrote. “None of them had ever done anything in particular to the teeth, nor was there in appearance anything in particular in the constitution which would give rise to such a disease.” 

More than 200 years later, many questions still arise when erosion comes up for discussion. One reason that erosion is now on the clinical radar is a change in culture and diet. In lieu of milk and water there are, presumably, many modern sources of extrinsic acid in a seemingly limitless array of carbonated soft drinks, “sports” beverages, and other dietary ingredients.

Clinicians today also increasingly recognize that conditions, such as bulimia and gastroesophageal reflux disorder (GERD), are major sources of gastric acid-caused erosion.

Of course, there’s another reason and you see it every day: More people have more teeth than ever before. Caries prevalence has been reduced significantly in industrialized countries, largely through the widespread use of fluoride, which gives erosion—and its cousins, dental attrition and abrasion—more time to reshape natural enamel and dentin.

     As the debate on the etiology continues, experts already agree that the most important preventive tool is education, which brings awareness to clinical practice and patients. Is there more dental erosion today? Relatively scant population-based evidence says yes. But national dental surveys are few and far between and usually don’t include measures of tooth wear, so the true prevalence and severity of dental erosion is difficult to pin down. There is some population-based evidence that the presence of erosion is “growing steadily,” according to Thomas Jaeggi, DDS, and Adrian Lussi, DDS, MS, of the Department of Preventive, Restorative and Pediatric Dentistry, School of Dental Medicine, University of Bern.

Writing on prevalence in a comprehensive new monograph, Dental Erosion: From Diagnosis to Therapy (Karger), the researchers conducted an exhaustive review of erosion studies, but noted that different “scoring systems, samples and examiners” made it difficult to compare outcomes. Some data stands out:

•  Preschool children ages 2 to 5 showed erosion on deciduous teeth in 6 to 50 percent of the subjects.

•  Young schoolchildren ages 5 to 9 had erosive lesions on permanent teeth in 14 percent of the cases.

•  Among adolescents ages 9 to 17,
11 to 100 percent examined showed signs of erosion.

•  Adults ages 18 to 88 demonstrated a prevalence ranging from 4 to 82 percent, depending on the study.

•  Males had “somewhat” more wear than females.

•  Erosion distribution showed a “predominance” of occlusal surfaces, mandibular first molars in particular, followed by facial surfaces (anterior maxillary teeth).

•  Erosion was frequently found on maxillary incisors and canines.

The authors note that even when reviewing many studies with disparate methods, they can identify a trend toward a “more pronounced rate of erosion in younger groups,” making it important to identify “at-risk” patients early in order to prevent irreversible damage later on.

In any case, now is the time to respond. “It’s an insidious process, but it’s not a question of panicking,” says Domenick T. Zero, DDS, chairman of the Department of Community and Preventive Dentistry, Indiana University School of Dentistry. A veteran dental erosion researcher, Dr. Zero says, “Erosion has a complex etiology and there are many reasons why some people have it and others don’t. Clinicians need to first look for it and, second, they need to assess the patient to identify the cause or causes, which can be different in every person. They also need to determine how to help the patient change behaviors and maximize protection.”

As the literature on erosion generally notes, erosion is multifactorial and intertwined with tooth wear from abrasion and attrition, which makes it difficult to offer up broad, general suggestions. “Tooth wear is the result of three processes: abrasion (wear produced by interaction between teeth and other materials), attrition (wear through tooth-to-tooth contact) and erosion (dissolution of hard tissue by acidic substances,” writes Martin Addy, BDS, PhD, professor of restorative dentistry at the University of Bristol Dental Hospital and School. “Both clinical and experimental observations show that individual wear mechanisms rarely act alone, but interact with each other,” he says in the monograph. “This interaction seems to be the major factor in occlusal and cervical wear.”

Therefore, knowledgeable clinicians who want to counsel their patients should proceed on an individual basis after carefully examining the teeth and extensively interviewing each patient regarding dietary and oral hygiene habits. Since vinegar on a salad, a glass of orange juice, or even wine, for example, all have some potential to dissolve tooth structure, it stands to reason that salivary flow patterns, chemistry, and volume vary among individuals, particularly among those who have a problem with erosion and those who don’t.

The salivary pellicle that is instantly adsorbed onto a clean enamel surface is very acid resistant. Among individuals who do not show erosion, or wear of the teeth, the quality and quantity of the saliva is probably a counterbalance. Other factors, such as bruxism, occlusal forces, appliances, and oral habits (e.g., excessive and/or overly aggressive toothbrushing), also influence the progression of dental erosion, but a good place to start your clinical evaluation may be with salivary testing.

A preventive solution for some patients could be as simple as stimulating salivary flow on a daily basis, since stimu-lated saliva has more buffering capacity.

Clinically speaking, what is it?

“Erosive tissue loss is part of the physiological wear of teeth,” writes Carolina Ganss, Dr. med. dent., of the Department of Conservative and Preventive Dentistry, Justus Liebig University, Giessen, Germany. “[It is] initial loss of tooth shine or luster, followed by flattening of convex structures, and, with continuing acid exposure, concavities on smooth surfaces, or grooving and cupping occur on incisal/occlusal surfaces,” she says in the new monograph.

“Dental erosion must be distinguished from other forms of wear, but can also contribute to general tissue loss by surface softening, thus enhancing physical wear processes. The determination of dental erosion as a condition or pathology is relatively easy in the case of pain or endodontic complications, but is ambiguous in terms of function or aesthetics.”

David Bartlett, BDS, PhD, a member of an expert panel on erosion at the FDI Annual Congress in 2005, agrees that all patients should be considered at-risk for developing tooth wear and “examination should routinely involve looking for clinical signs.”

Writing in the International Dental Journal (IDJ), Dr. Bartlett says the clinical appearance of various “sub-types” of tooth wear can vary. In its pure form, for example, attrition is identified by flattened occlusal surfaces that look as if “someone has filed the teeth with sandpaper,” with the degree of wear in both arches usually equal and teeth fitting close together.

When erosion and attrition are combined, the appearance tends toward cupping or “undermining” of the occlusal surfaces. Since dentin is less mineralized than enamel, it wears “preferentially,” resulting in occlusal cupping or depressions.

When erosion is dominant, he says, the buccal and lingual surfaces of the upper incisors appear smooth and shiny with a general loss of structure. On the palatal surfaces of the upper incisors, exposed dentin is smooth, often with a “halo of enamel surrounding the lesion.” That pattern, he adds, is often associated with gastric causes or oral retention of acidic drinks, such as soda pop, fruit juices, or wine.

Abrasion on its own is unusual, Bartlett says. When that does occur, it could be caused by biting or chewing on objects like tobacco pipes, nails, or pens.

“By far, the most common presentation of tooth wear is the result of a combined lesion involving erosion and abrasion,” he says. “Acids weaken the outer 3 to 5 microns of mineralized enamel and increase the susceptibility of the enamel and dentin to abrasion from toothbrushing, with or without toothpaste.”

William Mitchell, DDS, a clinician who is retired from the U.S. Army Dental Corps, says extreme wear on the lingual side of the maxillary anterior teeth is a sign that reflux or bulimia is causing enamel erosion. Sometimes he sees a filling that looks as though it has formed its own plateau within the tooth, a sign that erosion is dissolving enamel and dentin while leaving the restorative material behind.

Diagnosis

Clinician Samantha Shipley, DDS, says that knowing your patient base and the local population can offer clues as to whether erosion is of clinical significance where you practice. A former dentist in the U.S. Army Dental Corps, Dr. Shipley has moved from place to place and has noticed cultural differences that impact the teeth. While attending dental school in San Antonio, she saw a lot of significant erosion because the local population favors lemon-sucking and other eating habits that bring the teeth into extended contact with dietary acids. She also has seen it in active duty soldiers, some of whom acknowledge drinking up to 12 cans of a high-acid carbonated beverage on a single duty shift to remain alert.

 While many indices for the diagnosis of tooth wear have been proposed, all are “more or less” modifications or combinations of those published by Eccles and Smith and Knight. Drs. Ganss and Lussi note that all erosion indices include “diagnostic criteria to differentiate erosions from other forms of tooth wear, and criteria for the quantification of hard tissue loss.” They also point out that the indices are less than ideal; studies show that making a differentiation between abrasion and erosion on occlusal surfaces, for example, can be “difficult.”

For the future, they write, four major points on the diagnosis of tooth wear are important:

•  There is a need for standardization of terminology and indices.

•  Items of currently used indices should be reconsidered with respect to the validity of diagnostic criteria and grading.

•  Considerations about the differentiation between pathological and physiological erosive tooth wear, which may be a matter of age and progression rate (among other things), are necessary.

•  The development of practicable and, preferably, chairside diagnostic tools for progression rate is needed.

Prevention

“Every time we consume acid there is some minor loss of mineral from the tooth,” says Dr. Zero. “The question is whether it’s irreversible. It’s highly individual.”

“The intrinsic and extrinsic aetiology factors responsible for dental erosion are well understood, as are the chemical events leading to the initial mineral dissolution, softening and eventual loss of the dental surface,” he writes in the IDJ. “Of greatest importance are the pH, titratable acidity, phosphate and calcium concentration [and] fluoride content of the erosive challenge, which determines the degree of saturation with respect to the tooth mineral, and thus the driving force for its dissolution.

“Of the biological modifying factors affecting the erosion process, the protective properties of saliva and its contribution to pellicle formation are considered of greatest importance. Unstimulated salivary flow rate and buffering capacity have been directly associated with dental erosion.” There is considerable overlap, he adds, “between the etiology of dental erosion and that of dentinal hypersensitivity.”

Behaviorally speaking, there are many case reports of abusive or unusual behavior by individuals who frequently consume acidic fruit juices or other acidic beverages daily. Bizarre eating, drinking, and swallowing habits increase the direct contact time with the teeth and are clear factors in the risk for dental erosion. Consumption of acidic beverages at bedtime has been implicated in increased risk.

Behavior can be strongly influenced by socioeconomic status. In one study, researchers found that 4-year-old children from a low socioeconomic group had significantly less erosion than children from higher socioeconomic groups. The researchers surmised that the observed differences may have been due to variations in dietary patterns and oral hygiene practices. In contrast, a similar study reported that the prevalence of tooth mineral loss in 14-year-olds was slightly positively associated with the level of social deprivation in the area where the children lived. Obviously, direct comparison of such studies is problematic, but they do suggest that behavior stemming from socioeconomic status can influence the risk for dental erosion.  

This knowledge tells clinicians that patient education about the causes and prevention of acid erosion is essential to halting its progression. That includes advice on reducing or eliminating consumption of acidic soft drinks and juices, the use of modified beverages with “reduced potential” to cause erosion (now available in the United Kingdom), and frequent application of high concentration topical fluoride to prevent further demineralization and reduce the loss of enamel or dentin from abrasion. The efficacy of the latter approach still needs to be confirmed in clinical studies, Dr. Zero says. The most common preventive recommendations, he writes in the IDJ, are:

•  Referring or advising patients to seek medical attention when intrinsic factors, such as bulimia or GERD, are involved.

•  Reducing or eliminating frequent exposure to acidic beverages.

•  Avoiding habits, such as sipping, swishing, or holding drinks in the mouth, and drinking with a straw, to ensure that the flow is not aimed directly at individual tooth surfaces.

•  Avoiding brushing immediately before an erosive challenge (vomiting, consumption of dietary acids), because the acquired pellicle provides protection against erosion and toothbrushing removes it.

•  Avoiding brushing immediately after an erosive challenge because enamel remains softened and susceptible to mechanical tooth wear for at least one hour.

•  Using a soft toothbrush and low abrasion toothpaste to minimize additional wear.

•  Avoiding toothpastes with a low pH.

•  Using a remineralizing/neutralizing fluoride rinse, sodium bicarbonate (baking soda solution), milk or food (such as cheese or sugar-free yogurt) after an erosive exposure.

•  Stimulating saliva flow with sugar-free chewing gum or a lozenge designed for that purpose.

•  Considering the use of modified acid beverages with reduced erosive potential.         

Clinical management and new products

Fluoride—whether it is applied chairside or by using products at home—is the key active ingredient for managing erosion. All fluoridated toothpaste helps to manage erosion; however, some formulations provide added benefits. In advanced cases of eroded enamel, cosmetic or restorative therapy often is required. Therefore, treatment plans generally focus on the prevention of acid erosion.

Now that tooth wear—and erosion specifically—is considered a significant clinical issue, clinicians and their patients can expect new product development in that field to accelerate. A special issue of the Journal of Clinical Dentistry (JCD), for instance, devoted five articles to acid erosion and the development of toothpaste featuring improved fluoride availability and uptake that helps re-harden softened tooth enamel, low abrasivity that limits further tooth wear, a pH neutral formulation, and 5% potassium nitrate to manage tooth sensitivity. Since evidence indicates that dentin hypersensitivity can result from tooth wear (e.g., erosion), such a product also may provide welcome relief to patients with dentinal pain.

Researchers also are working on the development of the aforementioned modified beverages that are lower in acid than those now commonly consumed. Such products are already available in the United Kingdom.

“Evidence suggests that topical fluoride is effective in limiting the progression of erosion, and that fluoridated toothpastes have a role to play in reducing demineralization and promoting remineralization of tooth enamel,” writes Jack Toumba, BSc, MSc, PhD, Leeds Dental Institute, University of Leeds, in the JCD. “The ability of such toothpastes to combat erosion is likely to be determined not solely by their nominal fluoride concentration, but also by a combination of high free-fluoride availability and efficient delivery of fluoride to the tooth surface, which in turn may be influenced by the selection of formulation ingredients.”

“There is evidence to suggest that fluoride may be effective in increasing resistance to dental erosion by dietary acids,” he adds.

The effectiveness of a newly-developed, anti-hypersensitivity toothpaste in promoting enamel fluoride uptake and protecting surface-softened enamel against further erosive challenges was examined. The new dentifrice contains sodium fluoride and potassium nitrate. Surface micro-hardness analysis showed that the new toothpaste was significantly more effective than two other fluoride-containing pastes at protecting enamel from additional softening following an initial acid challenge. The level of protection correlated with the fluoride contents of the enamel specimens following treatment. The new toothpaste also provided better fluoride uptake when compared to a wide selection of commercially-available pastes. This toothpaste formulation maximizes fluoride delivery and uptake thus enhancing the level of protection against acid.

Dr. Zero writes in the JCD that the test dentifrice was able to act “either by enhancing the remineralization or reducing the demineralization provided by subsequent erosive attacks,” adding that “long-term confirmation of the results concerning their clinical relevance is necessary.” More research, he says, is needed to investigate the combined long-term effects on surface wear from using a “low abrasive, highly bioavailable fluoride dentifrice.”

Because successful restoration of erosive cervical or occlusal lesions may be “challenging,” particularly when dentin is exposed or there is loss of “vertical occlusal height,” Dr. Toumba writes in the JCD that prevention and/or early management of dental erosion is an “important priority in modern dentistry.”

Dr. Shipley says that while she has diagnosed and treated a lot of tooth wear, and general dentists are on the frontline of erosion prevention and
treatment, a referral to a prostho-dontist on difficult restorative cases is “a good way to go. They’re very knowledgeable about the subject and have good ideas on how to treat it. At times, when I don’t know where to go with treatment, I’ll send a patient for a consultation and second opinion.”

Rick Asa is a freelance writer based in Westmont, Ill. Send comments on this article to impact@agd.org.

Good information

General dentists have an increasing array of resources on dental erosion and other forms of tooth wear to reference. Those who want to take a plunge into the deep end of the pool from the get-go can purchase a new monograph, Dental Erosion: From Diagnosis to Therapy (Karger), online for $72. This compact, hardcover compendium features erosion researchers on the leading edge and covers every nook and cranny on the subject.

In the foreword, Birgit Angmar-Mansson notes that until now “no attempt has been made to collect and organize the available information in a single book. This volume of Monographs in Oral Science is the first book dealing solely with erosive tooth wear.

“The thirteen chapters present a broad spectrum of views on dental erosion, from the molecular level to behavioral aspects and trends in society. The multifactorial etiological pattern of erosive tooth wear is emphasized and is a strand in connecting the different chapters,” which are accompanied by comprehensive references to the original articles on which the chapters are based and intraoral photos that illustrate the text and help to orient the reader.

For quick access and ordering information go to http://content.karger.com/ProdukteDB/produkte.asp?Aktion=showproducts&searchWhat=books&ProduktNr=231844.

Another useful source of up-to-date information on dental erosion (and one that your patients will more readily understand) is a Web site set up by GlaxoSmithKline. There you can view streaming video of some of the top erosion researchers in the world, find graphics and charts that make the process of erosion easier to understand, and even download a booklet that you can easily print out, leave in your waiting room, and hand out to patients who want to know more.

The expert testimony on the Web site is based on full presentations made at a dental erosion symposium that was part of the FDI Annual Meeting in Montreal (2005). There are lots of hyperlinks to investigate. The site is user and viewer-friendly and navigation is simple.

Once at the site, don’t forget to check out information on the CD-ROM educational program that is available for free. This package also stems from the 2005 symposium and features expert commentary, scientific presentations, professional resources, and self-tests. Learning objectives include an understanding of the “various aetiologies of the different components of tooth wear and how they may contribute to dentin hypersensitivity” and an exploration of “diagnostic, preventive and management strategies that can easily be put into practice, increasing the dental practitioner’s confidence and competence” in the management of tooth wear and dentin hypersensitivity.

You’ll need a PC with Windows 98/NT/2000/XP and a sound card with speakers. If you have a Mac®, you’re out of luck; it won’t work.

From that site, you also can access full papers on dental erosion and tooth wear in general from a special supplement of the International Dental Journal, which also stems from the erosion symposium. Go to http://www.aciderosion.co.uk.

Finally, with all of your free time, you might want to reference a series of articles on erosion in a 2006 special issue entitled “Tooth Surface Loss” in the Journal of Clinical Dentistry (V17, No. 4). In addition to information on tooth wear etiology, the articles offer the results of tests on a new toothpaste designed to help manage erosion via improved fluoride availability and uptake, very low abrasion, and a neutral pH formulation. Although there are some qualifiers added by researchers throughout, such as the need for more clinical study to confirm results, the papers offer an interesting glimpse into the new world of dentifrice formulation and the next generation of over-the-counter products that your patients will see on shelves very soon.

Tooth wear definitions 

Classic dental texts organize the subject of tooth wear into three categories:

•  Erosion—Tooth erosion is wear of teeth from a chemical/dissolving process. Dietary acids are undoubtedly the principal cause of extrinsic tooth erosion, with the most frequently consumed and potentially damaging acids coming from fruit acids and phosphoric acid in fruit juices and soft drinks. The list of foods that can play a role in tooth erosion is a long one and includes soft drinks, fruit juices, pickles, fresh fruit, and even yogurt. Children often display erosion from repeated consumption of carbonated beverages, fruit syrups, and vitamin C supplements. Odd habits, like lemon-sucking and swishing soda in the mouth, extend the amount of time that enamel and dentin are exposed to the acids and can increase the structural damage.

•  Abrasion—the wearing away or pathological wear of teeth from a mechanical/rubbing process. Tooth grinding (bruxism) and toothpaste abuse are considered the two main causes of dental abrasion. Toothbrushing technique, frequency of brushing, time spent on brushing, and the force applied during brushing all can play a role in abrasion, as can the materials used (i.e., the shape of the toothbrush bristles and the abrasiveness, pH, and amount of toothpaste).

•  Attrition—the normal physiological wear of teeth from chewing and tooth-to-tooth contact, without any foreign substances intervening (i.e., two-body wear). Such contact occurs while grinding the teeth, during swallowing,  and speech, and when lifting heavy objects. The individual degree of attrition is generally associated with age.

 Other extrinsic factors include environmental exposure  (e.g., from acidic gases encountered by employees in businesses like battery making and phosphate mining) and drug use. Methamphetamine, cocaine, and “ecstasy” all have been reported to promote tooth wear and erosion either from the drug use itself or from habits associated with it, such as dry mouth and clenching and grinding during drug binges. Illicit drug users also tend to neglect their oral hygiene.

Many prescription and over-the-counter drugs also can lead to erosion by causing dry mouth (xerostomia). Studies indicate that more then 400 commonly-used therapeutic drugs can lead to dry mouth. Without adequate salivary flow—particularly stimulated salivary flow with its increased buffers and preventive agents—the teeth are at increased risk for caries, erosion, and periodontal disease.

Intrinsic erosive factors include gastroesophageal reflux disease (GERD), in which acidic stomach contents are regurgitated into the mouth, and bulimia nervosa, which involves regular binge eating and purging to maintain weight. It’s been reported that among patients with bulimia, 90 percent have dental erosion, while 15 percent of the adolescent population engages in binge eating and purging.