Surveys have shown that many people do not clean their dentures effectively and suggest that the dental team may fail to educate patients in basic denture hygiene procedures. Poor denture hygiene can result in denture staining and malodour and is a risk factor for oral and systemic diseases. Methods available to clean dentures are described. Their modes of action, effectiveness and potential adverse effects are discussed. A combination of cleaning methods is probably more effective than any one method. Recommendations for effective denture cleaning that can be given to patients by the dental team are provided.
CPD/Clinical Relevance: The dental team needs to explain effective approaches to denture hygiene to patients. Written information should also be provided to reinforce the message.
Article
Elizabeth King
Accumulations of plaque and debris on dentures can lead to denture staining, micro-organism overgrowth, unpleasant odour and calculus formation. Poor denture hygiene is a risk factor for oral diseases, including caries, periodontal disease and denture-related stomatitis (Figure 1). Antifungal treatment reduces oral Candida albicans colonization associated with denture-related stomatitis. However, unless dentures are decontaminated and their cleanliness maintained, stomatitis will recur when antifungal therapy is discontinued.1 Micro-organisms from the oral cavity can also colonize distant tissues by entering the systemic circulation or through aspiration. Oral bacteria have been implicated in several systemic diseases, including bacterial endocarditis, infections of the respiratory tract and heart disease.2 Overnight denture-wearing is associated with an approximately 2- to 3-fold greater risk of the incidence of pneumonia in older patients.3
Figure 1. Denture stomatitis causing inflammation of the palatal mucosa underneath the denture-bearing area.
Effective denture cleaning is therefore important and there is a wide variety of materials and methods available to clean dentures4 (Figure 2). Misuse of cleaning materials, however, may have an adverse effect on denture materials. Furthermore, case reports have described allergic reactions to cleanser products. Serious harm has also been sustained by patients who have misunderstood, failed to read or ignored cleaning instructions and have ingested or aspirated denture cleansing agents.5
Figure 2. A range of over-the-counter denture cleaning products including a denture bath, denture brush, denture paste (Dentu-Creme), effervescent peroxides (Polygrip, Smile and Steradent), alkaline hypochlorite (Dentural) and chlorhexidine (Corsodyl).
It is important that dentists and dental care professionals have a good understanding of denture hygiene, and that appropriate denture hygiene advice is given to patients. Surveys indicate that this is not always the case.6–8 Both patients and dental care professionals may be confused by the wide variety of solutions, pastes and powders available for cleaning dentures with a variety of claims for their relative efficacies.
This article describes the different ways in which dentures may be cleaned. It highlights potential adverse effects of denture cleansers. It also provides recommendations for denture cleaning that members of the dental team may give to their patients.
Ideal properties of a denture cleanser
Denture cleansers must remove plaque and stain effectively and kill any remaining microbes on the denture surface without damaging the material and affecting adversely the properties of the denture materials.
The ideal properties of a denture cleanser are given in Table 1.
The ideal properties of a denture cleanser include:
Removal of organic and inorganic denture deposits;
Bactericidal, fungicidal and viricidal action;
Biocompatibility (non-toxic and non-irritant) with oral tissues;
Compatibility with all the materials used in denture construction and maintenance, eg polymethylmethacrylate, cobalt chromium, stainless steel, temporary soft materials and permanent resilient soft lining materials;
Ease of application and removal without residue;
A long shelf life;
Be relatively inexpensive.
It should be noted that currently no commercially available denture cleanser encompasses all properties listed.
Denture cleansing
The ways that dentures can be cleaned can be described as mechanical, chemical or microwave.
Mechanical action
Denture brushes
There are many denture brushes on the market, most of which have a double bristle head. They are generally softer and less abrasive than toothbrushes. A larger brush on one side of the head is designed to clean flat denture surfaces and the smaller side is designed to clean between denture teeth and smaller components. Alternatives to a denture brush include using a normal toothbrush or a nail brush. Dentures may be brushed with plain water, salt water, soap or denture pastes.
Denture pastes
Examples of denture pastes include: Dentu-Creme (GSK, Brentford, Middlesex, UK) and Totalcare Denture Toothpaste (Superdrug, Croydon, Surrey, UK). Brushing dentures with toothpaste over time can cause damage to acrylic resin and soft linings.9 To overcome this problem there are denture pastes available which have less abrasive formulations. Denture paste manufacturers recommend brushing with denture pastes for around 3 minutes daily and then rinsing the denture with water. Alternatives to denture paste include brushing with non-abrasive soaps, such as hand soap or washing-up liquid, followed by thorough rinsing.
Ultrasound
Ultrasonic denture cleaning baths are available for patients to purchase (eg iSonic F3900, iSonic Inc, Chicago, IL, USA). These baths use ultrasonic waves to create microscopic cavities (bubbles) in liquid which implode and dislodge contaminants and food particles from areas of dentures that are otherwise difficult to clean. Denture cleanser solutions can be used in ultrasonic baths to enhance the efficiency of denture cleansing.10
Chemical action
Peroxide denture cleansers
Examples of effervescent peroxides include Steradent (Reckitt Benckiser Healthcare Limited, Slough, Berkshire, UK), Polident (GSK, Brentford, Middlesex, UK), Efferdent (Prestige Brands, Yatton, Somerset, UK) and Boots Smile Denture Cleansing Tablets (Boots, Nottingham, Nottinghamshire, UK). Peroxide denture cleansers usually come in tablet form, however, they are also available as a powder or as a liquid solution. The active chemicals include oxidizing agents. These work by producing free oxygen radicals which are highly reactive. The cleansers contain alkalis and acids. In addition, they contain chemicals for colour, flavour and odour. The acids, such as citric acid, react with oxidizing agents creating a more vigorous reaction and therefore creating an abundance of free oxygen radicals. Free radicals oxidize molecules in the cell walls and membranes of bacteria and fungi. This disrupts the cell wall membrane, killing the organism. Free radicals also remove stains and odours by breaking down proteins and molecules. Alkalis, such as sodium bicarbonate, produce carbon dioxide bubbles when mixed with acid and this effervescent cleaning dislodges debris and has an antibacterial effect. Peroxide denture cleansers also contain chemicals for colour, flavour and odour.
Alkaline hypochlorites
Examples of alkaline hypochlorites include: Dentural (Martindale Pharmaceuticals, Brentwood, Essex, UK) and Milton (Ceuta Healthcare, Bournemouth, Dorset, UK). Hypochlorite solutions kill micro-organisms by disrupting their outer wall or membrane proteins causing cell death. Hypochlorite also dissolves organic tissue and chlorine oxidizes pigments thus removing debris and stains.
Dentural is a hypochlorite-based denture cleanser and does not need to be diluted before use. Milton is produced for general sterilization purposes. It contains 1% sodium hypochlorite and 16.5% sodium chloride. Milton needs to be diluted with water before use as a denture cleanser. For cleaning dentures, 5 ml in 800 ml solution is recommended (Owen A, Ceuta Healthcare, email to Abbie Owen [Abbie.Owen@ceutahealthcare.com] communication, 2018 Jun).
Acids
Examples of acids include Curaprox BDC Daily Gel and Curaprox BDC Weekly Concentrate (Curaprox, Huntingdon, Cambs, UK). The active ingredients include citric acid and sodium citrate. The concentrate also includes eucalyptus oil. The acidic components, citric acid and sodium citrate, break down plaque, calculus, stains and debris which makes their removal easier. Soaking dentures in citric acid-based cleansers reduces the number of viable C. albicans cells.11 In addition, eucalyptus oil contained in Curaprox Weekly Concentrate has antibacterial properties.
Disinfectants
Examples of disinfectants include Corsodyl (GSK, Brenford, Middlesex, UK). Disinfectants such as chlorhexidine have been recommended to be used in the management of denture-related stomatitis. Prolonged use of chlorhexidine, however, can lead to brown staining caused by dietary chromogens (tea, coffee, red wine, etc).12
Enzymes
Enzyme-containing denture cleansers have been shown to reduce yeast cells and plaque accumulation.13 They prevent plaque accumulation on the surfaces of dentures by breaking down proteins. Pure enzymatic cleaners are produced in tablet form for general disinfection purposes and are only available for professional use. Enzymes are included in some effervescent peroxide cleansers to provide combined action type formulations (eg Polygrip 3 Minute and Polident Overnight — GSK, Brentford, Middlesex, UK).
Other materials
A survey of dental health professionals8 showed that a variety of non-proprietary materials were recommended by dentists to clean dentures including, as mentioned above, soaps and household bleach, as well as salt, sodium bicarbonate and vinegar.
Microwave irradiation
The use of microwaves at 650 watts, as produced by commercial microwave ovens, has been shown to sterilize PMMA dentures immersed in sterilized water.14 There have been no long-term studies using this cleaning method. There is a risk of denture deformation and warping of the prosthesis and so the method cannot be recommended. Furthermore, it cannot be used for dentures with metal components.
Adverse effects of denture cleaners
It is important that dental professionals understand the potential adverse effects of the common denture cleaning methods and provide appropriate advice to their patients. Patients must be reminded to handle dentures carefully and to avoid dropping them onto hard surfaces and to avoid distorting flexible components.
Material compatibility
Several studies have investigated potential adverse effects of denture cleaning methods on the properties of denture materials.10,15,16 The findings can be summarized as follows:
Mechanical brushing can abrade and cause roughness of the surface of polymethylmethacrylate (PMMA). Roughness as a result of abrasion is increased with use of denture cleaning pastes and is greater with use of toothpastes.
Denture tablets, effervescent alkaline peroxide cleaners, acids and enzyme cleaners used according to manufacturers' instructions have no significant adverse effects on denture materials. Prolonged soaking in these solutions can result in colour changes in the acrylic resin denture base with little difference in effect between cleansers.17 Patients present occasionally with denture bases that have become white. These have been called bleached dentures. The cause for the ‘bleaching’ is believed to be repeated use of very hot water.18
Prolonged immersion in the peroxides can also cause surface roughness and reduced flexural strength of PMMA.
Hypochlorite solutions can corrode metallic components such as cobalt-chrome bases and clasps and solders (Figure 3).4 All other cleaners are compatible with metals. Prolonged immersion in sodium hypochlorite can cause greater surface roughness and reduced flexural strength of PMMA than the peroxide cleansers.
Chlorhexidine mouthwash can cause staining of PMMA.
Alcohol-based mouthwashes can cause surface crazing of the surface of PMMA.
Figure 3. Example of corrosion of the metal framework of a cobalt-chrome denture left in alkaline hypochlorite overnight.
Few studies have investigated methods for cleaning flexible polyamide dentures. It has been shown, however, that some cleaning materials can adversely affect the surface of the flexible dentures.19,20 The manufacturers of some flexible denture bases recommend specific denture cleanser formulations to reduce the risk of unwanted changes, eg Valclean (Valplast International Corp, Westbury, New York, USA) and Flexible Denture Cleanser (RDT Technology Sussex, England, UK) (Figure 4). These flexible denture cleansers may not be suitable for nickel-chromium alloys due to the risk of corrosion. Manufacturers' instructions should be followed.
Figure 4. Examples of flexible denture cleansers, including Val-clean and Flexible Denture Cleaner (FDC)
Brushing will damage short-term denture soft lining materials and should be avoided. Effervescent peroxides can cause bubbling and rapid deterioration of the surface, with discoloration, malodour and hardening.21–24
Long-term denture soft lining materials can be colonized by micro-organisms and can become stained and malodorous if they are not cleaned effectively. Incorrect cleaning methods, such as over-vigorous brushing and use of hot water, can cause surface abrasion and discoloration of the soft lining material.21
Patient harm
Persulfates, included as an ingredient in some denture cleaners, are known to produce allergic reactions. Symptoms can include irritation and blistering of the oral mucosa and breathing difficulties. The US Food and Drug Administration have asked manufacturers to consider using alternative materials.5
Case reports have also described patients having ingested or aspirated denture cleansing agents accidentally, resulting in serious injuries such as corrosive burns of the glottis, oesophagus, trachea, bronchi and stomach.5,25 It is therefore essential that patients, or their carers, understand that denture cleansers are not to be used as a mouthwash or ingested, and seek medical advice immediately if any denture cleansing agent is accidentally ingested or aspirated.
Which denture cleansers are most effective?
Most studies testing the effectiveness of denture cleaning methods have been in vitro laboratory studies. These have shown that different denture cleaning products have different levels of cleaning efficacy.11,26,27
A Cochrane Review of interventions for cleaning dentures found that it was not possible to conclude that any one denture-cleaning method is the most beneficial.28 It noted, however, that studies suggest that a combination of mechanical cleaning plus chemical cleansing appears to be most effective in the reduction of plaque and microbial counts.
Mechanical cleaning
Mechanical cleaning, such as rinsing dentures with water and brushing with a toothbrush or denture brush, removes gross debris and can remove some but not all the adherent biofilm. In vitro evidence has shown that brushing alone has no effect on Candida species colonization.29 Therefore, the use of an additional denture cleanser is necessary to provide further reduction in micro-organisms.30
Antimicrobial action
The non-proprietary denture cleaners, vinegar, soap and bicarbonate are ineffective at reducing micro-organism colonization.10 Toothpastes are bactericidal but do not eliminate Candida species.10,29 Soaking PMMA in hypochlorite for 10 minutes is the most effective method in removing denture plaque micro-organisms, including C. albicans.26,27,31 Hypochlorite is the only agent with the ability to eradicate MRSA micro-organisms.32 Effervescent peroxide tablets are effective at killing micro-organisms when a minimum soaking time of 5 minutes is used.10 A ten-minute immersion in 0.12% chlorhexidine is as effective as 10 minutes in hypochlorite for inhibiting bacterial growth.26
Stain removal
Most denture cleansers remove stains from PMMA in varying degrees.31,33 Although studies suggest differences between cleaners, there is limited evidence from in vivo studies and it is not possible to say that any cleaner is most effective at removing stains. Prolonged immersion of dentures in chlorhexidine can cause increased staining due to the uptake of dietary chromogens onto the PMMA surface.12
A recommended approach to denture hygiene
The inconsistency of oral health advice offered to patients with dentures has recently been reviewed by the Oral Health Foundation, who have published global guidelines to improve the oral and general health of denture wearers worldwide. The optimal denture cleaning guidelines defined by the Oral Health Foundation are outlined in Table 2.34
Daily cleaning of the dentures using mechanical action – brushing with a toothbrush or denture brush and an effective, non-abrasive denture cleanser (no dentifrice).
Daily soaking in a denture cleansing solution – this seems to deliver extra chemical breakdown of the remaining plaque and some level of disinfection of the denture. Denture cleansing solutions should only be used outside the mouth, and denture wearers should strictly follow the manufacturers' guidelines.
Denture wearers should not keep their dentures in the mouth overnight, unless there are specific reasons for keeping them in. This guideline is even more important for people at a higher risk of developing stomatitis and for frail or institutionalized older people. Soaking in a denture cleanser solution after mechanical cleaning seems to be beneficial for preventing denture stomatitis and the potential risk of pneumonia events in these groups of people.
All patients who wear removable dentures should be enrolled into a regular recall and maintenance programme with their dental professional.
A recommended approach to denture hygiene in a form that can be provided for patients is given in Table 3a and Table 3b. Table 3a provides information for acrylic resin and metal-based dentures. Patients with flexible dentures should follow the general advice but use a denture cleaner advised by the manufacturer of the denture base material. Table 3b provides advice for cleaning dentures with short-term and long-term soft linings.
How to clean your dentures
Why is it important to clean your dentures properly?
Like teeth, dentures can collect debris, plaque and calculus. Poor denture hygiene can lead to a build-up of stain, bacteria and fungus on the denture surface. This can cause bad breath and diseases of the teeth, gums and mucosa.
Incorrect denture cleaning can cause staining, discoloration and damage to the denture materials.
NEVER use boiling water as this will cause dentures to distort.
Denture cleaning products should only be used to clean dentures OUTSIDE of the mouth and are NOT to be rinsed or swallowed.
How should your dentures be cleaned?
Rinse your dentures with water after every meal to remove food debris.
Take your dentures out and clean them each night before retiring to bed. Handle dentures carefully, being careful not to drop them or bend any flexible clasps. Clean over a full sink or towel to prevent breakage should you accidentally drop your denture.
Remove soft debris, plaque and any denture fixative by brushing with a soft brush and denture paste or soap and cold water.
Having carefully brushed your dentures, soak them each evening in a denture cleansing solution according to manufacturers' instructions. Rinse your dentures thoroughly with water after using a cleansing agent.
Ask your dentist if you need further information about denture cleansing agents.
DO NOT use hypochlorite (chlorine containing) solutions for dentures with metal bases or claps as these can cause corrosion of the metal.
Following soaking in a cleaning agent, rinse and soak your dentures in cold water overnight.
How to clean dentures with soft linings
Soft linings are either SHORT-TERM (temporary) or LONG-TERM (permanent) materials. If you are unsure whether the soft lining on your denture is short-term or long-term, please ask your dentist.
Some denture cleaning methods can damage denture soft lining materials causing hardening, surface damage and discoloration.
Clean as described below, however, DO NOT soak your denture in alkaline hypochlorite (chlorine containing) solution if there is a metal strengthener in your denture as this may corrode the metal.
How should you care for dentures with SHORT-TERM soft linings?
Rinse your denture and soft lining with water after each meal.
Remove your denture each evening and soak for 10 minutes in an alkaline hypochlorite such as Dentural or dilute Milton solution.
Do NOT brush the soft lining material – this can roughen the surface.
Store your denture overnight in a container without cleanser or water.
How should you care for dentures with LONG-TERM soft linings?
Rinse your denture and soft lining with water after each meal.
Remove your denture each evening and brush denture and soft lining gently with a soft brush. Firm brushing can abrade and roughen the surface.
Remove your dentures each evening and soak for 10 minutes in an alkaline hypochlorite solution.
Store your denture overnight in a container without cleanser or water.
Conclusions
Surveys have shown that many people do not clean their dentures effectively and suggest that the dental team may fail to educate patients in basic denture hygiene procedures. There is a current lack of scientific knowledge of relative efficacy of different denture cleansing methods. A combination of mechanical and chemical cleansing methods is more effective than any one method. Commercial denture cleansers should always be used according to manufacturers' instructions.
