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Introduction

Dental caries is the most prevalent non-communicable disease in the world. Its distribution among children, however, is skewed. Caries prevalence is relatively low in high-income, and relatively high in low- and middle-income countries. Children from high-income countries have benefited from the available established caries preventive measures; such as the use of fluoride-containing products and awareness among their parents and caretakers of the importance of keeping tooth surfaces free from plaque. In addition, children who have developed tooth cavities can utilize the well-organized oral healthcare services operating in many high-income countries. Children, adolescents and adults in these countries can comfortably rely, for oral care, on the available healthcare systems, often financed by government and/or private insurance schemes.

The oral healthcare situation for people in low- and middle-income countries is completely different. Not only is the prevalence of dental caries higher and its severity greater; the oral healthcare system is usually insufficiently equipped to provide the needed care. This means that many in these countries suffer in many ways: most carious cavities are not treated restoratively. People with open cavities usually present themselves at a health center or dental clinic when pain is unbearable. Extracting the badly decayed tooth is then the treatment of choice but the prevalent unavailability of restorative care can have serious consequences, especially for children. A study from the Philippines revealed that almost all carious cavities in 6- and 12-year-olds remained untreated and that 40% of these cavities were accompanied by infection of the pulp, abscesses, fistulas and/or infected root remnants . These conditions may pose a serious threat to children’s general health, because of the risk of developing systemic sepsis, osteomyelitis and infection of the neck and the floor of the mouth. Furthermore, toothache may alter children’s eating and sleeping habits which can affect their growth negatively . Untreated carious cavities in children have also been associated with protein-energy malnutrition and stunted growth , and children suffering from early childhood caries have been associated with lower body weight and reduced body length .

Untreated carious cavities do not only have an impact on the physical condition of children; but their cognitive development may also become impaired. In a survey of native-American schoolchildren, one third admitted to missing school because of dental pain , and 70% of children in the Western Cape, South Africa, had missed school due to toothache . The seriousness of the absence, or low coverage, of oral (restorative) care in many low- and middle-income countries is demonstrated in the case of the Philippines. The country’s Department of Education reported toothache as the principal reason for absenteeism from schools . The effect of chronic dental pain in children is not a supposition: affected children are unable to focus and unable to complete school assignments, which affects their school performance negatively .

So, why do people in low- and middle-income countries not receive sufficiently organized restorative oral care?

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Restorative oral care

In high-income countries, restorative oral care relies on electrically driven equipment and a well-functioning piped water system. The care is provided in a dental clinic building by dental professionals who are generally well paid. Of late, globalization has encouraged dental professionals to travel, mainly for holidays, to low- and middle-income countries. However, a growing number undertake the travel to provide oral care to those in need. The latter group will have encountered an oral healthcare system that is completely different from those that they are used to. Dental clinics with equipment that is non-functional because of a lack of spare parts, unavailability or irregularly of electricity supply and piped water and a shortage of materials and instruments are more the rule than the exception in many low- and middle-income countries. Provision of oral care in these countries is, therefore, poorly developed and covers a small part of the population; mainly those residing in cities. Most of these dental clinics have been equipped as copies of those in high-income nations. This is a perfect example of a transfer of systems without adaptation: as if cultural differences do not exist and as if countries are organized and run in one identical way.

But what kind of restorative oral care could make the difference?

2

Restorative oral care

In high-income countries, restorative oral care relies on electrically driven equipment and a well-functioning piped water system. The care is provided in a dental clinic building by dental professionals who are generally well paid. Of late, globalization has encouraged dental professionals to travel, mainly for holidays, to low- and middle-income countries. However, a growing number undertake the travel to provide oral care to those in need. The latter group will have encountered an oral healthcare system that is completely different from those that they are used to. Dental clinics with equipment that is non-functional because of a lack of spare parts, unavailability or irregularly of electricity supply and piped water and a shortage of materials and instruments are more the rule than the exception in many low- and middle-income countries. Provision of oral care in these countries is, therefore, poorly developed and covers a small part of the population; mainly those residing in cities. Most of these dental clinics have been equipped as copies of those in high-income nations. This is a perfect example of a transfer of systems without adaptation: as if cultural differences do not exist and as if countries are organized and run in one identical way.

But what kind of restorative oral care could make the difference?

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Atraumatic Restorative Treatment (ART)

Over the last two decades a preventive and restorative caries management concept has been developed: Atraumatic Restorative Treatment (ART). ART does not require electricity or piped water systems. It uses hand instruments for opening and cleaning tooth cavities and mainly uses a glass-ionomer to fill the cleaned cavities and to seal caries-prone tooth surfaces . Autocure glass-ionomers are essential in this context as their powder-liquid hand-mixed form is appropriate everywhere in the world. Other restorative materials require, in one way or another, the use of electricity-driven equipment. The combined use of hand instruments and glass-ionomers, therefore, make it possible to improve the oral health well-being of population groups in many countries.

The poorly equipped state of dental clinics in many low- and middle-income countries restricts oral healthcare provision in the areas that they serve. Restriction is demonstrated by dentists’ only extracting teeth, day in and day out. For example, the restoration/extraction ratio in South Africa’s public oral healthcare system is 0.11 , which is similar to that of Tanzania (0.04) , indicating that dental personnel rarely restore teeth, usually extracting them instead. The introduction of ART into the oral healthcare systems of these countries would facilitate a reduction in tooth extractions and an increase in the proportion of teeth that are instead restored and sealed. It would also increase the quality of life of many and the job satisfaction of dentists. It is obvious that the introduction of ART, using glass-ionomers, is alone insufficient to improve the oral health of people in low- and middle-income countries in a sustainable manner. Therefore, the WHO Collaborating Centre of Oral Health Care Planning and Future Scenarios in Nijmegen, the Netherlands, has developed a package of pain relief and preventive, promotional and restorative evidence-based treatments for use in low- and middle-income countries in 2002: the Basic Package of Oral Care (BPOC) , which includes ART. Nevertheless, how good is ART?

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Results of investigations on ART

Many researchers from many countries have investigated different aspects of ART. Salient findings from these studies can be summarized as follows:

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  Survival rates of single-surface ART restorations using high-viscosity glass-ionomers in primary and permanent posterior teeth are high and meet the specifications of the American Dental Association (ADA) .

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  Survival rates of multiple-surface ART restorations using high-viscosity glass-ionomers in primary posterior teeth do not meet the ADA specifications .

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  Survival rates of single-surface ART restorations in permanent posterior teeth, using high-viscosity glass-ionomers, do not differ significantly from comparable traditional restorations using amalgam .

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  Survival rates of single-and multiple-surface ART restorations, using high-viscosity glass-ionomers, in primary posterior teeth do not differ significantly from comparable traditional restorations using composite and compomer .

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  The caries preventive effect of ART sealants using high-viscosity glass-ionomer is very high and was significantly higher than that of sealants produced using composite resin .

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  Pain felt during treatment was lower in child populations treated restoratively with ART using high-viscosity glass-ionomers, than when traditional restorative procedures were used . Even ART without local anesthesia was better accepted than traditional treatment with local anesthesia .

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  Dental anxiety in adults treated using ART in public health clinics was lower than when adults were treated using traditional restorative procedures . This difference between the two types of treatment was not observed in children treated in a modern dental clinic .

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  Initial wear rates of ART restorations using high-viscosity glass-ionomers are low .

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  ART restorations using high-viscosity glass-ionomers were more cost-effective after 2 years than comparable amalgam restorations .

These outcomes show that the ART approach using high-viscosity glass-ionomers produces quality sealants, and restorations in single-surface cavities in primary and permanent posterior teeth.

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ART and glass-ionomers

The first material used in conjunction with the ART approach was a carboxylate cement. This material was soon replaced by a medium-viscosity glass-ionomer in the late eighties. At that time, medium-viscosity glass-ionomers were mainly used for filling cavities in non-stress-bearing situations such as in buccal surfaces, where they survived for long . Given the circumstances in which cavitated teeth were routinely extracted to alleviate pain, filling a hand instruments-cleaned cavity in a stress-bearing surface (occlusal) with a medium-viscosity glass-ionomer was considered acceptable. It was soon realized that restorations using this type of glass-ionomer performed better than expected . This observation prompted manufacturers to improve the physical characteristics of autocure glass-ionomers, resulting in the marketing of high-viscosity glass-ionomers. The meta-analysis on the effectiveness of ART restorations has shown that single-surface ART restorations using high-viscosity glass-ionomer survived significantly longer than comparable restorations using medium-viscosity glass-ionomers . This implies that medium-viscosity glass-ionomers should not be used with ART in practice.

Not only has the survival of ART sealants and ART restorations using glass-ionomers been investigated: various properties of high-viscosity glass-ionomers have also been researched for use in combination with ART. The press-finger technique, of pressing the glass-ionomer with an index finger in pits and fissures, appears to be functioning well. The fissure penetration depth of high-viscosity glass-ionomer sealants, placed using the press-finger technique, did not differ significantly from that of composite resin sealants . There was also no difference in fissure penetration depth between high-viscosity glass-ionomer sealants placed using the press-finger technique and a ball-burnisher . Some studies have reported lower bond strength between tooth tissues and high-viscosity glass-ionomers than was achieved for resin-modified glass-ionomer used in ART restorations . However, no significant difference in quality of bonding was observed at the interface between high-viscosity glass-ionomers and enamel and dentin prepared using ART and conventional rotary instruments . Furthermore, microscopic observations showed that voids and bubbles are present in high-viscosity glass-ionomer ART restorations and that the influence of the press-finger technique appears to have little or no effect in spreading the high-viscosity glass-ionomer into the tooth cavity . The outer surface of ART glass-ionomer restorations has also been investigated. The level of surface roughness of two high-viscosity glass-ionomers was lower than the critical surface roughness of 0.2 μm. The antibacterial activity of high-viscosity glass-ionomers used with ART has recently been investigated. Both freshly mixed and 1-week-old high-viscosity glass-ionomers showed antibacterial properties against various microorganisms.

Although glass-ionomers have a number of beneficial properties, these may not always be sufficient for their use in certain restorative situations. Nevertheless, glass-ionomers have earned their place in restorative dentistry in low-, and middle-, and high-income countries, and certainly in combination with the ART approach. However, in order to produce reliable and long-lasting ART restorations, the dental practitioner needs to have acquired skills and comprehension and to exercise diligence . Therefore, following an ART training course is essential.