The Link Between Tooth Decay And Dry Mouth

Overview 

Did you know a 2018 clinical examination of 56% of 14,270 patients showed 90.2% of people have at least one dental filling, and nearly half (46.5%) have at least one crowned tooth? Are you aware 21-27% of the general public reported having a dry mouth?^1,5

Dry mouth (also known as xerostomia) is a condition where insufficient saliva production by salivary glands in the mouth occurs. Saliva helps keep the mouth cavity moistened.² 

Some common symptoms and signs of dry mouth include: 

• Difficulty in speech and swallowing
• Burning or a dry, rough textured tongue
• Thirst
• Impairment in tasting food 
• Bad breath (halitosis)
• Dry and cracked lips
• Mouth lesions
• Dental diseases such as cavities, tartar buildup and gum disease result in tooth decay² 

Tooth decay (dental caries) occurs when bacteria in the mouth damage the tooth’s outer surface, creating holes (cavities), which result in tooth sensitivity, discolouration of teeth, tooth pain, and tooth loss.³ 

Saliva plays an important role in providing minerals to teeth to keep them strong and has antibacterial properties. Therefore dry mouth will increase the chance of tooth decay.⁹

The purpose of this article is to understand the link between xerostomia and tooth decay. This will help patients to manage their dry mouth by adopting oral health and lifestyle modifications.²

Causes and determinants of dry mouth

Medication and therapies 

Dry mouth occurs as a side effect of certain medication/s and/or therapy. These include:

• Antihistamines used to treat allergies, insect bites and cold 
• Antihypertensives for hypertension 
• Antidepressants for depression 
• Anticholinergics used to treat reflexive muscle motion 
• Antipsychotics for mental health conditions 
• Sedatives for inducing sleep 
• Muscle relaxants to slow muscle contraction 
• Diuretics for high blood pressure 
• Anticonvulsants which treat epileptic seizures and neuropathic pain 
• Cancer radiation therapy by damaging salivary glands and mouth tissue²

Diseases 

Dry mouth may occur as a symptom of:

• Diabetes and chronic kidney disease 
• Hepatitis C virus 
• Sjögren’s syndrome 
• Anxiety by increasing breathing rate²

Lifestyle factors 

Lifestyle factors can cause dry mouth. These factors include:

• Smoking cigarettes⁴
• Breathing by mouth due to nasal congestion, snoring or sleeping with an open mouth ²
• Drinking less water causes insufficient hydration of the mouth cavity to fuel the production of saliva²
• Heavy alcohol or caffeine consumption²

Age

A study investigated dry mouth and its relation with age, medication and sex. The study included 1,103 patients of which 654 were people assigned female at birth (AFAB). Among these patients, 427 (or 39%) were above the age of 60, and 26% were taking medication.⁷ Overall12.7% of the patients had dry mouth of which 10.3% were males and 14.4% were AFAB.⁷ It was concluded that age, medication and being a person AFAB were significant determinants for dry mouth.⁷ Being on medication was a significant risk factor for xerostomia and had a predicted risk status greater than age or sex.^6,7

Functions of saliva

Saliva, which is made up of 99% water and 1% electrolytes, has many properties by which it maintains oral health.⁹ These include:

• Oral pH neutralisation. Saliva contains bicarbonate which maintains the normal neutral pH (6.7-7.4)⁸ by neutralising acidic pH levels promoted by consuming carbohydrates/acidic food/drink which leads to bacterial growth and tooth decay^8,11 
• Antibacterial activity. Saliva prevents bacterial growth (which causes plaque and tartar formation). Calcium and phosphate minerals in saliva settle onto plaque in and between bacteria which results in a yellow-like colour of teeth^{12 10}
• Remineralisation of teeth. Saliva contains calcium, fluoride and phosphate which protect the outer mineralised tooth surface to maintain enamel integrity⁹
• Saliva promotes peri-oral tissue repair⁹
• Saliva protects softer oral mucosal tissue by moistening and preventing dehydration and allows speech¹⁰
• Saliva aids in rinsing, chewing, swallowing, dissolving and breaking down food and drink
• Saliva contains proteins such as statherin which allows the concentration of calcium and phosphate minerals to be regulated in saliva to maintain enamel strength and promote remineralisation¹³
• Mucins cluster bacteria to ease their swallowing and thus removal from the oral cavity and promote movement to a singular bacteria state which is easier to kill than bacteria in colonies clustered together^13,14

Clinical evidence and studies 

Studies linking dry mouth to higher risks of tooth decay 

Research has linked dry mouth to increasing chances of tooth decay through many studies. A study found that 70% of participants with dry mouth had at least one dental cavity compared to only 56% of those participants who reported no dry mouth.¹⁵ Another finding showed that at least one root surface cavity was present in those with dry mouth (54%) compared to those without a dry mouth (38%), which shows the correlation between xerostomia and dental caries.¹⁵ 

Another study examined how a group of adults aged 32 who had/did not have dry mouth were affected by oral health issues.¹⁸ Two main factors,  dry mouth and oral health-related quality of life, were measured using the Oral Health Impact Profile questionnaire and proved that those with xerostomia had a higher number of decayed surfaces (4.0) and higher number of teeth missing due to cavities (1.0) compared to those with no dry mouth.¹⁸

Prevention and management of dry mouth

Oral hygiene routine for xerostomia

Oral hygiene practices to prevent dry mouth include:

• Use of topical fluoride products; mouth wash, toothpaste, fluoride varnishes²
• Routine dental examinations every 4-6 months²
• Using a humidifier at night whilst sleeping²
• Flossing and brushing teeth twice a day to keep bacterial growth away²
• Using an alcohol-free mouthwash

Artificial saliva treatments 

Saliva stimulants work for patients with working or partially working salivary glands compared to salivary substitutes indicated for patients with non-functioning salivary glands, such as in Sjogren's syndrome, hepatitis C virus, or radiation therapy.² 

Saliva substitutes typically contain carboxymethylcellulose, mucopolysaccharide, and glycerate polymer base/mucins.² These ingredients have viscoelastic, lubricant and moisturising properties for xerostomia patients.

• Additionally, saliva stimulants include pilocarpine, malic acid, and citric acid²

Lifestyle modifications to increase saliva production 

• Reduce consumption of high sugar, salt and carbohydrate products and opt for salt/sugar-free, no added sugar or diet options 
• Discuss with doctors if you could be prescribed sugar-free medication
• Chew xylitol-containing gum or suck on sugar-free sweets/ice
• Drinking 14 units of alcohol per week
• Drink 6-8 glasses of fluid a day
• Rinse the mouth with water after consuming acidic food/beverages²
• Quit smoking
• Rehabilitation, counselling, joining peer support groups for drug addiction

Future studies  

Alternative therapies for xerostomia

Acupuncture

Acupuncture involves placing needles on certain areas of the body to stimulate specific parts of the brain to relieve health-related issues.¹⁶ A study administered acupuncture for dry mouth to 339 head and neck cancer patients three days per week during radiotherapy treatment.¹⁶ After a year of radiation therapy, results showed the incidence of clinically significant dry mouth was 35% in the true acupuncture group compared to the standard care control which received radiation but no acupuncture (55%) and sham acupuncture groups (48%). Acupuncture has reduced side effects and costs less compared to saliva substitutes and medication.¹⁶

Electrostimulation 

A study selected 22 healthy participants with an unstimulated average salivary flow of 0.02418 millilitres per minute.¹⁷ Electrical stimulation was provided externally and transcutaneously to this group and 15 participants responded with a higher average stimulated salivary flow from the parotid salivary gland.¹⁷ However, to stimulate saliva production with electrostimulation a partially/fully functioning salivary gland would be required.² Further research is required on alternative therapies to establish their efficacy in the treatment of dry mouth.

FAQs 

Is dry mouth a symptom of tooth decay?

Dry mouth is not a symptom of tooth decay but causes progression to tooth decay.

Does brushing your teeth prevent dry mouth?  

Brushing your teeth does not prevent xerostomia but prevents bacterial growth, plaque formation and therefore tooth decay which is caused by xerostomia. 

When should I see a dentist about dry mouth?  

You should see a dentist if xerostomia causes issues with taste, eating, drinking and speech and you have a red, swollen, painful, bleeding mouth and gums.

Summary

Xerostomia and dental caries are linked as saliva performs the function of rinsing, hydrating and preventing bacterial growth in the mouth which prevents plaque and tooth decay formation. Diagnosis of dry mouth and tooth decay occurs by doctor and dental examination. Treatment involves regular dental exams and oral, dietary and lifestyle routine changes.