Tooth Resorption (TR)

Tooth resorption (TR) is a condition in which the tooth structure undergoes replacement (resorption) by bony or inflammatory tissue. Odontoclasts are specialized cells responsible for the resorption of dentin and cementum. Normally, odontoclasts are associated with the physiological resorption of deciduous teeth (baby teeth). Deciduous teeth naturally undergo root resorption in an organized manner, allowing them to fall out, creating space for the permanent adult teeth, akin to the leaves falling from deciduous trees in the autumn, making way for new growth in the spring.

Adult teeth are designed to last a lifetime and should not typically experience TR. When adult teeth do undergo TR, it often occurs irregularly and unpredictably, affecting random areas of the tooth.

TR presents in two main patterns: inflammatory and replacement. Inflammatory TR is triggered by inflammation, and the resorbed portion of the tooth is replaced by granulation tissue. This process usually remains localized and affects single teeth affected by an inflammatory trigger. In replacement resorption, the resorbed tooth is replaced by bone or bone-like cementum. The exact cause of external replacement TR remains poorly understood and is often considered idiopathic, arising spontaneously or with an unknown cause.

In cats, both forms of TR are quite prevalent. It is important to know that when reading through the literature, the terminology “feline odontoclastic resorptive lesions (FORL),” "feline resorptive neck lesions," and "neck lesions" are now considered obsolete. In dogs, the occurrence of TR tends to rise with age and body weight. In dogs, older and larger breed dogs are more prone to developing TR lesions, particularly those involving external replacement resorption. Inflammatory TR in dogs is commonly associated with teeth affected by periodontal disease (dental disease around the tooth) and/or endodontic disease (dental disease within the tooth).

Generally, when TR is limited to the tooth root below the gum line, there is typically no inflammation or pain, and these teeth do not require extraction. However, when TR extends above the gum line, affecting the neck or crown (exterior surface) of the tooth, or becomes apparent externally when probing exposed root surfaces, these lesions can become inflamed and extremely painful due to exposed nerve endings within the tooth. In such cases, extraction is necessary to prevent and treat oral infection and pain. The decision to extract teeth should be based on the location and extent of TR. Many animals may have multiple affected teeth and may develop more over time. Currently, there is no way to predict which teeth will be affected by TR.

It's worth noting that TR differs from dental decay, such as a cavity, and it is a progressive condition. Consequently, a dental filling is not considered a viable treatment option in most cases, as it would dislodge as the condition advances.

Clinical signs of TR are often challenging to diagnose because our pets do not readily communicate oral pain. Instead, they may exhibit changes in eating and social behaviors. A thorough oral examination and dental imaging techniques such as dental radiographs and cone beam computed tomography (CBCT) are essential for evaluating which teeth are affected and whether treatment is required. Some clinical signs that may indicate clinically painful TR lesions include dental pain, gum swelling, pink or dark discoloration of the affected tooth, cavity-like holes in teeth, easily broken or brittle teeth without an obvious cause and tooth mobility.