NCCLs: How a Team of Researchers is Redefining How We Treat Them

Whether you’re a general dentist, dental hygienist, or a specialist, chances are you’ve seen one of these lesions. It’s also likely that if you researched causes and treatment options, you found a lot of contradicting literature. One team of researchers has made it their mission to cut through the fray and shed light on the etiology behind these lesions and offer practical, interdisciplinary treatment protocols for dental clinicians.

When Dr Paulo V. Soares encountered his first noncarious cervical lesion (NCCL) as a dental student in 1999, he was intrigued. This curiosity spurred him onto a path of research that has carried him through many unique disciplines, eventually leading him to found the NCCL Research Group at the Federal University of Uberlândia, Brazil.

“At the beginning of my career, I believed brushing and occlusal forces were the main causes of NCCLs,” Dr Soares recalls. “I did my master’s and PhD theses on biomechanical behaviors, and during that research I read many papers with different points of view about NCCLs. In 2008, I concluded my PhD where I observed high rates of failure for Class V restorations, and then I formed the NCCL Research Group.”

Today, the NCCL Research Group comprises 26 direct members and many more international collaborators from fields of study such as biomechanics, biochemistry, cellular biotechnology, psychology, nutrition, and gastric medicine, in addition to dental areas such as occlusion, endodontics, periodontics, prosthodontics, orthodontics, and operative dentistry. The group’s goal is to clarify the causes of NCCLs and cervical dentin hypersensitivity (CDH) and to explore treatment options that combat the causes of the lesions rather than mask the symptoms. Recently, the group’s research was gathered and developed into a book, Noncarious Cervical Lesions and Cervical Dentin Hypersensitivity: Etiology, Diagnosis, and Treatment edited by Drs Soares and John O. Grippo.

The reason the NCCL Research Group is so diverse is that the treatment of NCCLs and the control of CDH require a multidisciplinary view and approach. For decades, dental management and treatment of NCCLs focused on occlusal mechanisms and interventions such as restorative or periodontal procedures and ignored many of the underlying etiologic factors. When these factors are left unexamined and untreated, Class V restorations fail and the cycle repeats itself.

“NCCLs and CDH require a complete analysis of a patient as a member of your respective context/society,” Dr Soares explained. “We need to teach clinicians and future professionals that we can’t analyze just the teeth or mouth.”

Note the severe NCCLs resulting from dentin degradation in this 50-year-old woman with a highly acidic diet. (Courtesy of the NCCL Research Group, Uberlândia, Brazil.)

Aggressive NCCLs on the palatal surface of the maxillary anterior teeth in this 45-year-old man with diagnosed but untreated GERD. The teeth look as though they have been prepared for a full-coverage restoration with a chamfered margin. (Courtesy of the NCCL Research Group, Uberlândia, Brazil.)

When the NCCL Research Group included the expertise of a variety of non-dental professionals and researchers, they were able to combine individual findings and opinions into a much broader overview of etiologic factors than was previously recognized by the dental industry. These factors include parafunctional habits and their connection to psychologic stress, systemic diseases such as gastroesophageal reflux disease (GERD), dietary components, and occupational effects.

The NCCL Research Group’s findings prove that when clinicians have a narrow view of NCCLs and CDH, they set themselves up for a narrow rate of success. The high failure rates of Class V restorations are related to incomplete comprehension of the causes and progression of these conditions. Adhesive restorations treat the lesion or hypersensitivity, but they don’t stop progression or solve the problems. The etiologic factors behind the progression of NCCLs naturally promote early failure and debonding of Class V restorations; however, if clinicians take a more holistic approach to evaluating the patient-specific factors, treatment plans can be redesigned to treat the underlying causes through nonrestorative techniques before tackling the restorative and/or surgical options to restore tooth structure and alleviate symptoms.

What Causes NCCLs and CDH?

NCCLs are related to three distinct and fundamental etiologic mechanisms: stress, friction, and biocorrosion. The micromorphology of the tooth structure, particularly how enamel prisms and dentinal tubules are oriented in the cervical region as opposed to the incisal region, directly influences the area of origin and progression of NCCLs. The enamel is also thinner and more brittle at the cervical region, making it more vulnerable to stress fractures as well as biocorrosion in this area.

(left) Biocorrosive abfraction ridges within the wedge-shaped NCCL resulting from variation in the location of the tensile stress concentration over time combined with a biocorrodent, resulting in a lesion with irregular morphology attributed to a changing fulcrum toward the apex of the tooth. (right) Clinical aspects of biocorrosive abfraction ridges, or “progression lines,” within the wedgeshaped NCCL.

Maxillary right quadrant of a patient with GERD and bruxism. Biocorrosion of the teeth has been accelerated by attrition and abrasion.

Some of the most visually dramatic NCCLs are wedge-shaped abfractive lesions, which occur when the force of stress concentration exceeds the tensile strength of the dental tissue, leading to micro- and macrofractures at the cervical region. The most potentially damaging forces occur during intercuspation of the teeth during lateral excursion or anterior slide from centric relation to maximal intercuspal position, either during normal function or parafunction. The direction of eccentric occlusal loading will affect the stress concentration and strain pattern. With this in mind, in some cases one of the warning signs of future NCCL development can be wear facets on the occlusal surfaces. Patients with parafunctional habits should be considered at risk for NCCLs and CDH and should be evaluated closely for disease progression.

Biocorrosive abfraction is greater on the facial than on the lingual due to the lack of serous saliva on the facial.

Further compounding the progression of NCCLs is the lack of saliva on buccal surfaces. When present in required amounts, saliva can neutralize biocorrosive exposures and, to a certain extent, repair and remineralize damage to the tooth structure. Potential biocorrosive exposures include dietary sources (eg, citrus fruits, soda, white wine) and occupational or recreational exposures, such as chlorine exposure for professional and recreational swimmers. The combination of stress and biocorrosion can cause more damage than either acting alone.

During a biocorrosive challenge, a chemical reaction occurs between an acid and the components of dental structures. Hydrogen ions released by the acids combine with carbonate and phosphate ions within the mineral crystals of the tooth structure, resulting in chemical degradation and etching. Enamel is more vulnerable to acid action than dentin due to its larger crystal size and porosity. Continuous exposure to acids will remove the smear layer, exposing vulnerable dentinal tubules and leading to CDH. Even when the strength of the acid challenge is not great enough to result in direct removal of the enamel layer, it can result in a thin, softened layer that can be further degraded by mechanical wear and abrasion.

List of acidic foods and drinks from most acidic to least acidic.

What Do the NCCL Research Group Findings Mean for Treatment Protocols?

The multidisciplinary composition of the NCCL Research Group enabled them to identify the numerous interrelated causes of NCCLs and CDH that, like the hidden bulk of icebergs, have long confounded clinicians. The incidence rate of NCCLs and CDH increase annually, and with it the rate of published articles that disagree on causes and treatments. By taking an interdisciplinary, holistic view of the problem, the NCCL Research Group has finally found the guide to a 1,000-piece puzzle—but now clinicians have to put it together for their patients.

Note the initial areas of enamel demineralization in the maxillary teeth of this 30-year-old woman with GERD. (Courtesy of the NCCL Research Group, Uberlândia, Brazil.)

“New generations of clinicians will need to change the way they view and treat these diseases,” Dr Soares advises. “Don’t believe that a Class V lesion is one more type of cavity in your patient’s mouth. Know that it is an NCCL and understand that the main factors could be the patient’s lifestyle or habits. Believe that subgingival CDH with or without gingival recession can be the first step of a future NCCL or even an incipient microscopic NCCL. Restoring the missing structure or recommending a desensitizing toothpaste does not complete treatment for your patient.”

Paulo V. Soares, DDS, MS, PhD
Professor and Coordinator of the NCCL Research Group and Public Ambulatory Center
Federal University of Uberlândia
Uberlândia, Brazil

Noncarious Cervical Lesions and Cervical Dentin Hypersensitivity: Etiology, Diagnosis, and Treatment compiles the NCCL Research Group’s research and presents it in a way that is accessible to clinicians and enables them to view these two conditions holistically. Their findings make it imperative that clinicians understand the multifactorial mechanisms at work in order to lower the failure rate for Class V restorations and better manage this growing dental issue.

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