Tobias K. Boehm (October 8, 2024)
Recently an individual was referred to me from a community dentist to treat the existing “bone loss”. This is unusual because normally the concern is deep pockets, bleeding gums, pain or other signs of active disease. In this case, there was none other than the individual noticing a small degree of looseness for the affected teeth.
So what is bone loss?
Bone Loss (Dr. Boehm)
Typically, bone loss is seen by dentists on typical radiographs (typically called “x-rays” by non-dentists, but x-rays is the type of radiation that penetrates bone) as shown above. Good quality radiographs show the teeth and surrounding bone and distinguish between the lighter-colored enamel, uniformly gray dentin and the sponge-like bone. The enamel is the hard, white part of teeth seen in the mouth, and it tapers down to a point on the side of the tooth called the cemento-enamel junction (CEJ). In the absence of gum disease or other abnormal conditions, bone follows the CEJ closely. Typically, in absence of gum disease, the distance between CEJ and bone is less than 2 mm on radiographs (1). This distance is occupied by the gum tissue attaching to the tooth which on average is about 2 mm thick (2).
While so-called bitewing radiographs are best suited for measuring bone levels, this effect can be seen on most dental radiographs and dentists identify bone loss by looking for the relationship of CEJ to bone. Normally, the bone should follow the CEJ closely. As seen above, in this case, the bone does not parallel the CEJ of the teeth and is further away than 2 mm from the CEJ. Therefore, there is bone loss in this case.
When judging severity of bone loss, dentists will often estimate where the bone used to be (as shown above as dotted line, 2 mm below* the CEJ), and see where the bone level is now in relation to the length of the tooth roots. 0% bone loss means that the bone level is where it should be, 2 mm below the CEJ. 100% bone loss means that the bone level is at the tip of the tooth root. The percentage of bone loss reflects the severity of gum disease and increasing chances of tooth loss.
Typically, bone loss can only be determined with radiographs or through surgical reflection of gum tissue overlying bone. This is one reason dentists need to take radiographs during a dental exam as this is the only non-surgical way of checking for bone loss. Dentists may suspect bone loss if there are signs of gum disease such as gum recession and tooth loosening, but dentists need to confirm presence of bone loss by taking radiographs.
What causes bone loss
The bone loss seen above is typically caused by a severe form of gum disease called periodontitis. In periodontitis, microbes trigger gum inflammation in individuals and local sites prone to inflammation, and the inflammation eventually triggers changes in bone turnover, leading to loss of jaw bone nearest to the point where gums and teeth meet. This process is usually slow, takes place over many years and causes little to no pain. The rate of bone loss tends to become faster with increasing amounts of bone loss, and teeth tend to feel loose once about half or more of the tooth-supporting bone is gone.
Depending on the tooth location within the jaw bone and local factors, bone loss can either reduce bone uniformly from the crown down to the root tip, or cause locally more severe bone loss. In the first case, this might be called generalized or horizontal bone loss if the bone level stays parallel to the CEJ, but at a greater distance. In the second case, this might be called bone defects or vertical bone loss.
Other forms of bone loss can be caused by other tooth conditions. Root canal infections usually cause round areas of bone loss at the tip of the tooth root. Severe bite problems can cause funnel-shaped or V-shaped bone loss around teeth. Rare cancers and cysts can cause random growing areas of bone loss.
What can be done about bone loss
Unfortunately, little can be done about bone loss caused by periodontal disease. While it is possible to regrow bone in localized bone defects, it is difficult and unpredictable to reverse generalized bone loss. The main goal of gum disease treatment is to prevent further bone loss by arresting active gum disease and preventing new gum disease through good oral hygiene, frequent tooth cleanings and other preventive measures.
* The technical term is “apical”, or towards the tooth root, but to keep the description easily understood by non-dentists, I use the word “below” instead.
About the author:
Tobias K. Boehm, DDS, PhD, MBA, PC, DABP, DICOI, FGDIA is the founder of The Dental Institute, executive director at The Defeating Epilepsy Foundation and a professor at Western University of Health Sciences where he teaches and practices a periodontal specialist.
References:
(1) Hausmann E, Allen K, Clerehugh V. What alveolar crest level on a bite-wing radiograph represents bone loss? J Periodontol. 1991 Sep;62(9):570-2. doi: 10.1902/jop.1991.62.9.570. PMID: 1941497.
(2) Gargiulo, A.W., Wentz, F.M. and Orban, B. (1961), Dimensions and Relations of the Dentogingival Junction in Humans. The Journal of Periodontology, 32: 261-267. https://doi.org/10.1902/jop.1961.32.3.261