Commentary

The loss of tooth surface may be through abrasion, attrition and/ or acid erosion. The “and/ or” indicates the multifactorial nature of tooth wear, also termed noncarious tooth surface/ substance loss (TSL). This multifactorial process presents a major difficulty when attempting to evaluate a single factor. Typically, an epidemiological index is used to assess extent and severity of erosion but the index cannot discriminate whether minimal loss of enamel or dentinal exposure is because of erosion, abrasion or attrition. The validity of measurements made using so-called erosion indices is questionable. The UK National Child Dental Health Survey of 2003 recognised this and dropped the term “erosion”, used in the 1993 survey, in favour of TSL.

A small consensus group of interested parties devised, at a conference in 2007, a Basic Erosive Wear Examination index as a simple, reproducible scoring system and to assist in the decision-making process for the management of erosive tooth wear. Whether this index removes these difficulties remains to be seen, but the putative flaws of the indices may partly account for the generally weak associations between erosive factors and the outcome of erosion. The authors could not perform a meta-analysis because of the “marked variation in outcome measures” and stated that one study used the tooth wear index without discussion of its unsuitability for erosion measurement. Attempts to overcome index shortcomings have been to describe wear on labial or palatal surfaces as more likely to be from acid erosion, and to exclude incisal edge wear as this is likelier to be caused by attrition.

Of the 11 studies on adults included in the qualitative analysis, most had small sample sizes. Two study designs were assessed: prevalence of erosion in GERD cases, and prevalence of GERD in subjects with erosion. Diagnostic or “defining” criteria for GERD also varied, further adding to heterogeneity within the studies that were evaluated, a fact acknowledged by the authors.

The prevalence of erosion in adult subjects who had GERD ranged widely, from 5–48% in six studies (one study did not disclose the result): GERD ranged from 21–83% in the four studies assessing erosion cases. The results from the paediatric studies were even wider (13–87%) and depended, according to the authors, on the method used to diagnose GERD. Reliability and comparability seem to be significantly compromised in the studies, although the review authors tended to play this down.

The authors conclude that the systematic review showed a strong association between GERD and erosion but the correlation coefficients cited were weak to moderate. The influence of confounding factors in the studies was not addressed, even though the authors mention that dietary acids are associated with erosion. It may be that GERD sufferers avoid acidic foodstuffs and therefore dietary acid is not an issue, but some mention of this would have been appropriate. There was no discussion of confidence in the results from the 17 studies that met their selection criteria.

In summary, the review could have been more critical of the studies. The association between GERD and dental erosion is entirely plausible but the strength of association and the epidemiological evidence remains unclear.