Is there a connection between bariatric surgery and oral health?

Here you will find information about possible mechanisms that can affect oral health after bariatric surgery and how to prevent damage to your teeth.
Information booklet

Your starting point

Many of our patients undoubtedly have issues with their teeth already from the outset as ample research shows a link between higher BMI and impaired oral health.

If bariatric surgery affects conditions in the mouth, this can exacerbate oral diseases and dental damage that are already present. In some cases, patients themselves are unaware of oral health conditions, either because conditions do not cause symptoms or because they have not had a dental check-up for some time.

Obesity and cavities (caries)

From the age of six, cavities are more common in people who are obese. This is also seen in permanent teeth.

Cavities occur when bacterial deposits (sometimes referred to as biofilm or plaque) remain on the tooth surface for too long. The bacteria in the coating produce acid when they break down carbohydrates in food. If the plaque is left for a long time, it will dissolve the tooth enamel and cause cavities. These bacteria are present in our mouths at all times.

Saliva is an important part of our natural defence against cavities. Saliva cleans the teeth and helps to remove bacterial deposits. It also adds minerals that strengthen tooth enamel.

If plaque remains for a long time, the caries attack will continue into the tooth. If left untreated, the part of the tooth that contains nerves and blood vessels (pulp) will also be attacked. If this happens, it will be necessary to perform a root canal. This involves drilling away the caries, cleaning out the nerves and blood vessels before filling the root and tooth with filling material. In the worst case scenario, the tooth must be extracted.

If you change your eating and drinking habits and maintain good oral hygiene, a caries attack can be stopped. What was an incipient hole in the enamel can then, at best, remain unchanged for the rest of your life.

Obesity and acid damage (erosions)

Acid damage or erosion is the loss of tooth substance caused by prolonged low pH in the mouth. When the tooth enamel is exposed to acid, minerals are precipitated out of the enamel. This makes the enamel softer and more susceptible to both wear and decay. A drop in pH occurs naturally after consuming food and drink. Under healthy conditions, saliva - and time - will help to neutralise the pH of the mouth again. Adequate breaks between meals are therefore essential to prevent acid damage.

Tooth enamel

This puts you at risk of acid damage

There are several reasons why people with obesity may be more susceptible to acid damage.

Regurgitation and acid reflux

Heartburn and acid reflux is something everyone can experience from time to time, but it can also be a symptom of gastroesophageal reflux disease. Normally, the large muscle called the diaphragm and a sphincter at the top of the stomach will protect against leakage of stomach contents up into the oesophagus. In obesity, mechanical pressure on the stomach can cause stomach contents to be pushed up anyway. If stomach contents reach the oral cavity, the strong acid from the stomach can damage the tooth enamel. Stomach acid has a very low pH and is challenging for saliva to neutralise.

Eating disorders

In bulimia, some people will induce vomiting to get rid of calories after eating episodes. Vomiting is also accompanied by stomach acid, which damages tooth enamel. Such damage can increase further for patients who brush their teeth shortly after vomiting, as tooth enamel is particularly vulnerable until the pH in the mouth is neutralised.

Intake of acidic beverages‍

Many drinks are either naturally acidic (fruit juice) or have added acids that give a low pH. The way you drink is also of great importance for the extent to which this affects the pH of the mouth. Sipping acidic drinks throughout the day is much worse than, for example, drinking a glass with your meal.

The focus on avoiding calories may have led many people to drinking sugar-free soft drinks or flavoured water with a clear conscience. Such drinks may contain various acids (citric acid, phosphoric acid) for flavour, but the addition of sweeteners masks the acidic taste. These acids result in a very low pH in the mouth; carbonic acid, which is CO2 dissolved in water, is a very weak acid that does not affect pH to any great extent.

Carbonic acid is less of a problem for the teeth than the acids that are added for flavour. Both energy drinks and sugar-free juices can also have a low pH.

Soft drinksCoca Cola2,5
Pepsi Max, Cola Zero, Sprite Zero, Urge2,9
Water drinksTap water7,7
Farris Blå naturell5,2
Bon Aqua Lemon (carbonated)5,8
Bon Aqua Silver Lemon (non-carbonated)3,3
Olden Dråpe villbringebær (non-carbonated)3,1
Juice drinksSunniva orange juice3,8
Sunniva apple juice3,6
Ref: Birkeland et al. Surhet og bufferevne hos ulike drikkevarer på det norske markedet (2011)

Obesity and gum inflammation (periodontitis)

The gums are important for healthy tooth roots and good tooth attachment. Normally, the gums close tightly around the tooth. If plaque and bacteria are allowed to accumulate on the tooth over time, the gums can become inflamed. In the long term, a pocket can form between the tooth and gum. Inflamed gums tend to bleed easily, for example when brushing your teeth.

If plaque is not removed, the pockets around the teeth will deepen. The pockets are a habitat for various bacteria and are difficult to clean on your own. Bacteria that grow at the roots of the teeth produce secretes that intensify the inflammation of the gums. This can develop into a chronic inflammatory disease, periodontitis. The increasing pocket depth along the tooth root also weakens the tooth's attachment. Untreated periodontitis will lead to loose teeth and, in the worst case, tooth loss.

There is a link between obesity and periodontitis; the risk increases with higher BMI. The two conditions share the common feature that they contribute to the secretion of inflammatory substances that predispose to cardiovascular disease, among other things. Those who also have diabetes or smoke tobacco have an additional risk of periodontitis.

Physiological mechanisms

Bariatric surgery causes a number of systemic effects in the body. A systemic effect refers to how the surgery affects several organ systems and not just the fat deposits. Such systemic effects can be positive, such as improvements in high blood pressure and type 2 diabetes. Other systemic effects are negative, such as osteoporosis and increased risk of alcohol abuse.

At present, we do not know for certain whether it is the physiological effects of bariatric surgery that affect oral health or whether changes in oral health are primarily caused by patients' changed eating and drinking patterns. Based on what we believe we know, which is partly based upon the existing research and clinical observations, we would nevertheless like to point to possible mechanisms.

Vomiting and regurgitation

For many people, vomiting is a temporary phenomenon after sleeve gastrectomy. The new, tube-shaped stomach is narrow and may be swollen in the period after the procedure. Vomiting usually resolves as you become more familiar with what food you can tolerate, what the consistency should be, how well it should be chewed and what the correct quantities are.

However, for some patients, vomiting or regurgitation will be a persistent problem. If this happens, you should contact the clinic that operated on you and request an appointment with a nutritionist. The gastric acid in the vomit can cause a pH drop in the oral cavity and predispose to acid damage (erosions).

Reflux and heartburn

Heartburn is a symptom of gastro-oesophageal reflux disease, which is a known complication of sleeve gastrectomy. The stomach acid will cause a pH drop in the oral cavity and predispose to acid damage (erosion). There can be a smooth transition between what is reflux and what is regurgitation of food. Not everyone with reflux necessarily experiences the same symptoms (heartburn), but a dentist will be able to quickly recognise if you have developed acid damage.

Reflux is not only harmful to your teeth, but also unfavourable to your oesophagal health and should be treated. In some cases where medical treatment is unsuccessful, sleeve patients undergo reoperation.

Dry mouth

Saliva plays an important role in oral health! The saliva is a natural cleansing agent for the teeth and helps to loosen food debris. Immediately after brushing your teeth, saliva forms a protective protein film over your teeth. Saliva is also crucial for the pH balance in the oral cavity and also provides calcium and phosphate, which strengthens tooth enamel. In this way, saliva reduces the risk of both cavities and acid damage.

Adults produce 0.5-2 litres of saliva per day. A number of factors affect how much saliva is produced. For example, we produce less saliva when we sleep and more when we eat; several medications impair saliva production; and it also decreases with age. Some patients complain of experiencing dry mouth after bariatric surgery.

Dry mouth can be of such a severity that it qualifies for the diagnosis of hyposalivation. Hyposalivation is based on salivary secretion below certain threshold values as well as a subjective experience of dry mouth.

Symptoms of dry mouth

Increased need to drink
at night
Difficulty chewing or
Reduced or altered sense
of taste
Recurrent fungal
infections in the mouth
Dry, sore and chapped lips
Increased incidence of
tooth decay and acid

Absorption of nutrients

Bariatric surgery affects the absorption of a number of nutrients, including iron, folate, calcium and vitamin D. Little is known about whether this affects the oral cavity. However, we do know that reduced absorption of calcium and vitamin D together with hormonal changes after surgery pose a risk of developing osteoporosis. Osteoporosis and periodontitis (with loss of tooth attachment) are diseases that are associated with each other.

Microorganisms in the mouth

The combination of moisture, temperature and a steady supply of nutrients makes the mouth a fantastic environment for microorganisms. The microorganisms organise themselves into biofilms or plaques, structures surrounded by protective mucus that provide a stable growth environment. These biofilms attach to the visible part of the tooth, but can also attach below the gums if pockets have developed between the tooth roots and gums. We know that bariatric surgery affects the composition of bacteria in the oral cavity, but we know little about whether this affects oral health.


Obesity and gingivitis have certain things in common. Both conditions lead to increased secretion of inflammatory agents that predispose to cardiovascular disease, among other things. We also believe that the inflammation in the fatty tissues exacerbates the inflammation in the gums. In this sense, it is possible to imagine an improvement in gum inflammation after bariatric surgery.

The studies on this are somewhat limited. They actually show a worsening of the inflammation of the gums in the short term, but perhaps an improvement in the longer term. The fact that it worsens in the short term may have to do with a certain 'inertia in the system' - after all, it takes some time before there is a significant reduction in adipose tissue. At the same time, the mouth is prone to other changes shortly after surgery, such as temporary problems with vomiting and a transition to soft foods that contribute to more plaque formation.

It is important to keep your teeth clean. Use dental floss, interdental brushes and toothbrushes adapted to your needs.

Eating and drinking

Bariatric surgery creates major physiological changes in the stomach and intestines that force you to change your eating and drinking patterns. The surgery affects what you can eat, the way you eat, as well as how often you have to eat.

The operation also has consequences for what and how you drink. These changes can have an impact on oral health. However, we believe that oral health problems can be prevented if you are aware of these connections and take preventive measures.

New eating habits

The new diet presents several challenges to oral health.

Soft food

In the first period after surgery, you will be advised to eat soft foods and to take a long time at mealtimes. Soft food sticks more easily to the teeth and provides a basis for plaque.

Frequent meals

One of the biggest challenges for oral health is probably the need for small and frequent meals after bariatric surgery. After a meal, the pH in the oral cavity drops so low that the tooth enamel becomes vulnerable. During such periods, tooth enamel will soften as calcium and phosphate precipitate (the red zone in the figure below).

See figure 1

Provided that you have normal saliva production and allow a sufficiently long time between meals, the saliva will both neutralise the pH and add minerals that restore the tooth enamel. Increasing the frequency of meals or snacking (see next figure) can prolong acid exposure in the oral cavity, i.e. the time spent in the red zone. This makes tooth enamel more vulnerable.

See figure 2

Food choice obviously plays a role, as not all food is acidic to begin with. Many types of fruit - which are nutritionally important for health - have a very low pH, for example citrus fruits, grapes, apples and kiwi. However, all types of carbohydrates in the diet will nourish the bacteria in the mouth. These bacteria themselves produce acid that corrodes tooth enamel.

Unsustainable drinking habits

New drinking habits can certainly be a challenge for oral health. People are often advised not to drink at the same time as a meal, but rather to drink half an hour before and after eating. This is because the limited stomach volume means that you have to prioritise getting enough nutrition. Drinking at the same time as eating can also affect digestion and dumping tendency. For many people, it can also be challenging to get enough fluids, which means that they drink small volumes for much of the day. Dry mouth can also be a factor that makes you want to have drinks available throughout the day, and in some cases also during the night.

With a drinking pattern characterised by frequent, small intakes throughout much of the day, it is extremely important not to be adding acid or carbohydrates to the mouth at the same time. We know that many patients crave for sugar-free cola products. Cola contains added phosphoric acid, which has a very low pH. If cola is the go-to drink, it will in practice mean that your teeth are in an acid bath for much of the day. Both energy drinks and sugar-free juices can also have a low pH.

Others like to drink flavoured bottled water. Such products often have citric acid added, which also produces a harmful low pH in the mouth. The citric acid adds flavour, but does not feel very acidic as the water may be flavoured with sweeteners that mask it.

A tip if you have to drink soda is to drink it in one go. You should also take a couple of mouthfuls of water afterwards to wash away some of the acid residue. If you already have acid damage, you should drink with a straw.

Carbonic acid, which is CO2 dissolved in water, is a very weak acid that does not affect pH to any great extent. Carbonic acid is less of a problem for your teeth than the acids that are added for flavour. See here for an overview of the pH of different drinks.

Soft drinksCoca Cola2,5
Pepsi Max, Cola Zero, Sprite Zero, Urge2,9
Water drinksTap water7,7
Farris Blå naturell5,2
Bon Aqua Lemon (carbonated)5,8
Bon Aqua Silver Lemon (non-carbonated)3,3
Olden Dråpe villbringebær (non-carbonated)3,1
Juice drinksSunniva orange juice3,8
Sunniva apple juice3,6
Ref: Birkeland et al. Surhet og bufferevne hos ulike drikkevarer på det norske markedet (2011)

Psychological aspects

There are also factors related to our mental health that can have an impact on oral health after obesity.

Dental anxiety

For most people, going to the dentist involves a certain discomfort. It can be related to being vulnerable lying on their back while someone is way within normal intimacy boundaries, and it can also be related to the knowledge that it costs considerable money. Dental anxiety is something completely different and is actually a medical diagnosis,  odontophobia. This is a pervasive and excessive fear of the dental treatment situation which may have grave consequences.

As a result, people with dental anxiety generally avoid dental treatment and often only visit a dentist in acute cases. By that time, the need for dental treatment has often become much more extensive than if you visited a dentist at the first symptom or had regular check-ups.

The causes of dental anxiety vary, but many have had negative experiences with a dentist at a young age (school dentist) or experienced abuse in close relationships. The consequences of dental anxiety can affect life in many areas. Many experience strong shame as they 'know' that they really should have visited a dentist. Many withdraw from social situations if teeth in the front of the mouth are missing or visibly damaged. And some people self-medicate to cope with constant toothache. The concern that one's own anxiety may also affect their children's relationship with the dentist is a further worry.

We have reason to believe that dental anxiety is relatively common among patients with obesity. This is a poor starting point for bariatric surgery, as the surgery probably increases the risk of oral diseases and thus the need for dental treatment. Patients with dental anxiety are also likely to have poorer dental health before surgery. Thus, those with dental anxiety probably represent an extra vulnerable subset of patients.

However, there may be help available. The Norwegian public dental health service has programmes specifically for patients with dental treatment anxiety. Dentists, GPs and psychologists can refer you to such programmes, but you can also contact them yourself. See for more information and contact details. There are also many dentists in private practice who have expertise in dental anxiety, and who will facilitate safe and good treatment if you communicate that you have a complicated relationship with such health care.

Tannskrekk is a free app that can be downloaded to a mobile phone. It is an aid for those who are reluctant to seek dental treatment and helps to identify ways to adapt the visit to the dentist to make it more manageable.

Feeling shame

Many people with obesity have experienced a lot of shame associated with being large and falling outside of society's norms. The fact that their own attempts to loose weight have not resulted in permanent weight loss can lead to a feeling of powerlessness. Society's more or less explicit expectations that body weight can be managed by willpower fuels this powerlessness. For some people, the shame is so great that they choose not to share with others that they are undergoing bariatric surgery.

Such feelings can also occur in relation to dental status. We are exposed daily to influencers with bleached and partly fictitious teeth, and this has become an important market for segments of the dental health service. As a result, we see less and less of what are natural teeth, both in terms of colour and shape. If we have also had dental problems - and if these become more extensive after bariatric surgery - we can also experience shame associated with our teeth. This shame can create a further barrier to seeing a dentist.

System level

There are factors that affect oral health after bariatric surgery that neither are related to the patients' vulnerability, the physiological changes of the procedure nor the dietary changes forced by the surgery.

Organisation of dental services

The Norwegian healthcare system is a universal, publicly funded programme - with some exceptions. One of the exceptions is dental health services for adults. There is reason to investigate whether this affects patients in bariatric surgery treatment programmes.

Ideally, an obesity outpatient clinic is a interdisciplinary unit. However, odontology is not represented in these clinics. This can be justified by the fact that oral health is not mentioned in the international guidelines for bariatric surgery. At the same time, the limited perspective on oral health in somatic hospitals means that few, if any, systematically ask patients about their teeth. For hospitalised patients with complex health challenges and where oral health is part of the complexity, a closer integration of dentistry will contribute to achieving the holistic care we otherwise strive for in hospital treatment.

An equally big problem is that the cost of dental treatment must be covered by the individual. Considering that many people who have struggled with obesity throughout their lives also have a reduced ability to work and poor finances, there is an increased chance that preventive check-ups and treatment are not prioritised at an early stage. In the long term, the outcome is more extensive dental damage. The choice in the end may be between high costs or loss of chewing function.

One measure that is intended to remedy this in Norway is HELFO's provisions on conditions that entitle the patient to subsidised dental treatment. The question is whether the benefit provisions are sufficiently effective for common oral problems following bariatric surgery. To answer this, more comprehensive studies are needed that follow the health of bariatric surgeons from before the procedure and several years afterwards.

The research front

So far, there is relatively little research on oral health after bariatric surgery, and some of the existing studies have clear limitations.

One common shortcoming is that several studies have a short time horizon in terms of the effects they observe. For example, several studies of caries development after bariatric surgery have only six months of patient follow-up. If the risk of tooth decay increases after surgery, it is unlikely to happen in just a few months. As such, such studies that do not demonstrate a clear correlation may contribute to false reassurance.

The Norwegian Ministry of Health and Care Services has repeatedly emphasised oral health as a field in which more research is needed, particularly in connection with other diseases. This is particularly relevant in connection with bariatric surgery, given that the operations represent a significant increase in the risk of oral disease.

What happens to oral health after bariatric surgery? And just as importantly: What is oral health like in the first place, before undergoing surgery?

By Magnus Strømmen, Researcher/project manager
TkMidt og St. Olavs hospital

This is an under-researched field. We are therefore preparing a large observational study, BAR-ORAL, to investigate whether there is a relationship between the surgical treatment and oral health. The knowledge is relevant to:

Assess whether a dentist or dental hygienist should be part of the multidisciplinary patient follow-up
Provide patients with a sufficient knowledge base to make decisions about surgery
Provide a basis for preventing unfavourable late effects
Assess the appropriateness of current reimbursement schemes in Norway for dental treatment

Information brochure

For patients
PDF version of brochure on oral health specially developed for patients undergoing bariatric surgery.
Download PDF


For pasienter
PDF-versjon av brosjyre om munnhelse spesielt utviklet for pasienter som skal gjennomgå fedmekirurgi.
last ned PDF
For helsepersonell
Trykkeklar versjon av brosjyren som kan sendes til eget trykkeri. Du kan laste den ned nedenfor.
last ned PDF

Further information

We still know little about the relationship between oral health and diseases treated in specialised care. A contributing factor is the organisation of dental care on the sidelines of the rest of the health care system, dominated by private providers and free pricing. While personal finances do not represent a threshold for Norwegians’ treatment in specialised care (which is public health care), many people look at their pay packet before booking a check-up or treatment at the dentist. Another obstacle to knowledge is that the activities of the dental health service in Norway are not reported to central health registers. This makes it difficult to see any links between oral health and other diseases or treatments.

Knowledge of such relationships is particularly relevant for diseases or treatments that have systemic effects. Systemic here means that the disease/treatment is not limited to a single organ, but affects different organ systems in the body. Obesity is such a systemic disease that affects almost the entire body. The same applies to the surgical treatment of obesity, which produces both physiological effects and forces new behaviours that potentially affect oral health.

Assessment and follow-up after bariatric surgery should be multidisciplinary. This is organised differently in different hospitals, but oral medicine is not part of this multidisciplinary approach. As clinicians, we may not have heard patients complain about their oral health, but that may also be because we don't ask. We mainly find things we are looking for.

Below we have provided some arguments why we should focus more on oral health. Considering that patients between themselves on social forums share experiences of significantly worsened, this suggests that research is needed.

Obesity - a particularly vulnerable patient group?
Some diseases are closely linked to lifestyle habits and socio-economic differences in society. This is true for both oral diseases and obesity. A privately organised dental service can contribute to undertreatment and lost prevention for groups with particular challenges and poor means.

We know that the prevalence of dental caries (cavities) increases with higher BMI and that there is a high prevalence of gingivitis in the heaviest people. Gingivitis can develop into periodontitis and cause loss of tooth attachment as well as increase the risk of disease in other organs such as heart disease. Furthermore, other diseases, such as diabetes and depression, are linked to obesity and may themselves also predispose to poor oral health. In other cases, it is the treatment of the obesity-related diseases that indirectly affects oral health, such as the use of medicines reducing the saliva production.

The picture is further complicated by the fact that teeth may have been damaged by previous diet or eating disorders. We also know that dental anxiety is more prevalent among those with obesity which may contribute to delaying appointments for check-ups or treatment.

Is bariatric surgery associated with oral disease?
There is currently little research on oral health in bariatric surgery patients. However, there are short-term studies showing an increased incidence of acid damage, caries and gingival inflammation as early as 6 months after surgery. There is also seen reduced salivary secretion in bariatric surgery patients. However, the existing research has several limitations: The studies are few, based on few participants, have a short follow-up period, and researchers have made little distinction between different bariatric surgery procedures.

Also, with bariatric surgery comes altered eating patterns. Many people have to increase meal frequency to frequent small meals. Drinks are consumed between meals both for the sake of the limited stomach volume and to avoid dumping. This prolongs acid exposure to tooth enamel and can cause acid damage/erosion, weaker teeth and increased caries. Replacing water with acidic drinks contributes to unnecessary acid exposure. Some patients also struggle with vomiting, which also causes acid attacks on the teeth.

Other factors of potential importance for oral health after bariatric surgery are inflammation, the qualitative composition of saliva and the changes in microorganisms in the oral cavity. Little is yet known about their importance.

The project aims to increase knowledge about oral health in people seeking obesity treatment in specialised care. To achieve this, the BAR-ORAL project will monitor patients undergoing different obesity treatments with repeated oral health examinations over a ten year period. The assessment is comprehensive and includes examination of teeth, gums, mucous membranes and saliva.

To better understand the interaction between oral health, obesity and other diseases/treatments, the project will collect biological material for a biobank. Observations will also be linked with the participants’ data from central health registries in Norway.

The project is still under development and is therefore not open for inclusion. The website will be updated when the project starts. The study will recruit participants among patients undergoing obesity treatment at public hospitals in Central Norway.