MI foundations and evolution

The foundations of minimum intervention (MI) dentistry (MID) were laid in the late 1980s and early 1990s in the UK and Australia. In 1992, Dawson and Makinson published the first manuscripts related to MID that can be found on PubMed.1,2 They discussed a movement emerging in the UK, 'provocative' at this time and denouncing, based on clinical investigations, the inadequacy between patient needs and care provision in restorative dentistry. Indeed, in the UK, an extensive re-education programme had been initiated by the British Department of Health and Social Security in conjunction with the British Dental Association, based on those clinical investigations and the report of the Committee of Enquiry into Unnecessary Dental Treatment. The dental profession was also reminded of Smales' definition of dental health (written communication, 1988): 'Dental health can be considered in terms of a dentition that is functionally adequate, aesthetically pleasing, and free from discomfort and disease'. It was concluded that, within this definition, sound dental tissues constitute the basis of both functional and aesthetic dental systems.2 In the light of present knowledge in cariology (from histology/microbiology/pathophysiology to decision-making and clinical procedures), this has led to the development of the ICCMS concept (International Caries Classification and Management System) based on the statement 'The ICCM is a health outcomes focused system that aims to maintain health and preserve tooth structure'.3,4,5

Elderton denounced the traditional restorative care concept as being ineffective for managing caries.6,7,8,9 In 1996, his standpoint was that 'treatment should come to mean what it says, namely the curing of diseases – and much of this can only be accomplished by non-invasive means', and that 'restorative procedures should be seen simply as prosthetic, making up for lost tissues'.9

Aubrey Sheiham published the proceedings of a 1999 meeting devoted to MID (International Conference on Minimal Intervention Approach for Dental Treatment) in Kuwait.10 Three fundamental reflections included:

  1. 1

    'An interventionist orientation to dental diseases leads to a spiral of damage'

  2. 2

    'As dentists think they are looking after a machine, which is constantly breaking down, they do not allow it to repair or heal because they do not consider the natural history of disease'

  3. 3

    'Limiting intervention to the absolute minimum and giving prevention the opportunity to work should be the basis for quality dental care'.

In 2000, Tyas et al. proposed the four guiding principles of MI: 1) the remineralisation of early lesions; 2) the reduction in cariogenic bacteria (in order to eliminate the risk of further demineralisation and cavitation); 3) the minimal surgical intervention of cavitated lesions, the repair rather than the replacement of defective restorations; and finally 4) the disease control.11 In 2002, the Fédération Dentaire Internationale (FDI) also joined the MI movement with the diffusion of policy statements related to caries management.12 A decade later, Frencken et al. published a report of the FDI task group and drove home the message that the dental profession should move away from the surgical care approach and fully embrace the MID approach.13 They put the emphasis on the fact that the chance for MID to be successful is thought to be increased if dental caries is not considered an infectious disease but instead a behavioural disease with a bacterial component.13

All the points cited above revolve around one axis – appropriate caries management has to be planned at the patient susceptibility level and not at the lesion level as it is in traditional operative restorative dentistry.14 Demarco et al.15 investigating the clinical efficacy of posterior composite resin restorations, demonstrated that one of the main reasons for failure in the long term are secondary carious lesions (contemporary terminology: CARS – caries associated with restorations and sealants) highlighting that patient factors such as caries activity should be monitored and managed. Targeted patient education and engagement towards achieving and maintaining a better oral health (oral hygiene and diet counselling), modification of oral flora (from infant early colonisation to elderly), primary prevention (fluoridated agents and dental sealants), favouring the oral conditions allowing the remineralisation of early carious lesions (from adequate saliva buffering capacity to fluoridated agent regimen) and tooth preserving restorative managements are the backbone of patient-focused, case-by-case customised, personalised care plans.16,17,18 A recently developed comprehensive and integrated package related to caries management, from detection and classification to detailed clinical procedure recommendations, is the ICCMS.5 Based on contemporary scientific evidence, it proposes a comprehensive assessment and personalised caries care plan based around four different steps: history (patient-level caries risk/susceptibility assessment [CRA]), classification (caries staging and activity assessment), decision-making (synthesis and diagnosis) and management (personalised-caries prevention, control and tooth preserving operative care).

Patient-level caries risk/susceptibility assessment is the corner stone of an MI care plan, the only rational and ethical way to manage caries, both the process and lesions, in the light of current scientific knowledge. Indeed CRA allows determining the appropriate interventions – the non-invasive as well as the invasive (restorative) – and the recall intervals. Risk assessment can be carried out at the population/patient level whereas the oral healthcare team will implement protocols to help ascertain the individual patient's susceptibility to disease.

Caries risk assessment models

Caries risk factors and indicators have been incorporated into various risk/susceptibility assessment protocols/models assisting the oral healthcare practitioner/team in a logical systematic approach to synthesising information about a disease that has a multifactorial aetiology.

Some CRA protocols/models are specific to infants and children under 6 years old (Table 1):

  • Caries management by risk assessment (CAMBRA) system – age <619

  • System of the American Dental Association (ADA) – age 0-620

  • Dundee Caries Risk Assessment Model (DCRAM) (data collection at 1 for caries prediction at 4)21

  • Caries-risk Assessment Tool (CAT) of the American Academy of Paediatric Dentistry (AAPD) – age 0-3 for physicians and other non-dental health care providers; age 05 for dental providers22

  • MySmileBuddy (MSB) (for early childhood caries).23,24

Table 1 The different CRA protocols specific to children <6 years old and their variables

Some protocols are for children aged 6 and over, adolescents and adults:

  • Cariogram25

  • CAMBRA26,27

  • Caries Risk Pyramid (CRP)28

  • System of the American Dental Association (ADA)20,29,30

  • Caries-risk Assessment Tool (CAT) of the American Academy of Paediatric Dentistry (AAPD).22

They all combine similar variables that can be grouped in various ways as shown in Tables 1 and 2. It can be noticed that the terminology slightly differs from one system to another. Indeed, the presence of previous restorations may be considered as a disease indicator (CAMBRA) or as a clinical condition/finding (ADA; AAPD CAT) (Table 2); in the same manner, frequent in-between meal snacks may be listed as part of the biological factors (CAMBRA; CRP; AAPD CAT) or as part of the contributing conditions (ADA) (Table 2). Socioeconomic status is a common factor taken into account in children aged under 6 (CAMBRA, ADA, DCRAM, AAPD CAT), nevertheless in adults, it is only considered in the AAPD CAT. It is interesting that Cariogram does not address this factor directly; indeed Bratthall et al.25 explained that social factors do not directly act on the tooth surface but that they can often explain reasons for factors such as neglected oral hygiene and increased sucrose consumption, factors that are already included in the Cariogram, the same reason that socioeconomic status was eliminated from the 6 year through adult CAMBRA CRA form.

Table 2 The different CRA protocols for children ≥6 years old, adolescents and adults and their variables

The somewhat apparently arbitrary risk categorisation varies markedly among the protocols: risk levels (from 2 to 4 categories – low, moderate, high and extreme for CAMBRA, ADA and AAPD CAT), presence of risk (yes/no for DCRAM), pH (acidic in favour to demineralisation and alkaline in favour to remineralisation for the CRP) and percentage of chance to avoid further carious lesions (Cariogram) (Table 3). At a practice level, it is suggested that all members of each oral healthcare team are calibrated among each other (using test clinical scenarios and group discussion/consensus), so that risk levels obtained are meaningful across the team and to the patient and any future changes can be monitored and documented over time.

Table 3 The different risk level categorisation used in the CRA protocols for children, adolescents and adults

The Cariogram is the only one to propose a computer programme in which the factors/variables are entered after being given a score according to a predetermined scale.25 According to its built-in formula, the programme presents a pie diagram in which a green sector shows an estimation of the 'chance of avoiding caries'; this chance, and conversely the risk of caries, are expressions for the same process but illustrated inversely. The other cited protocols are structured forms that may help in the systematic assessment of multiple caries risk factors in practice and aid in objective record-keeping over time.31 Most recently CAMBRA has become available as an algorithm driven App for mobile devices called 'MyCAMBRA' (https://www.mycambra.com/).

Value of risk assessment

Twetman reviewed the evidence behind CRA in children and concluded that CRA should be carried out at the child's first dental visit and reassessments should be carried out throughout childhood and that multivariate models offer improved accuracy over those using single predictors.32 Tellez et al.33 published a critical review toward the evidence for the prediction of caries using Cariogram, AAPD CAT, CAMBRA and ADA systems. Based on 14 prospective cohort studies and randomised controlled trials, they concluded that the evidence on the validity for those CRA protocols is limited. It is unknown if the identification of high-risk individuals can lead to more effective long-term patient management that prevents lesion initiation and arrests or reverses the lesion progression. There is an urgent need to develop valid and reliable methods for CRA that are based on best evidence for prediction and disease management rather than opinions of experts. Tellez et al. (2015) reported that when using the CAMBRA protocol, the incidence risk ratio was not significantly higher for the moderate caries risk group compared with the low caries risk group.34 Thus, they suggested that low-risk and moderate-risk categories may not be sufficiently and distinctively different in predicting increasing risk of future caries and that a calibrated re-evaluation of the number of risk categories (four at the moment, namely low, moderate, high and extreme) is recommended.

When faced with issues highlighting the difficulties in identifying with any certainty at-risk patients and considering the evidence of the effectiveness of preventive measures for individuals at high risk is not always strong, Fontana et al. considered that caries susceptibility assessment still has the potential to enhance patient care by allowing the oral healthcare practitioner/team and the patient to understand the specific reasons for their caries activity and to tailor the care plan and recall interval accordingly.35,36Moreover, studies have shown that the most important factor in predicting future risk is recent caries experience and current disease activity.35,36 However, a careful analysis of all risk and protective factors will allow the oral healthcare team and patient to understand the specific reasons for the caries disease progress and thus will allow them to tailor the care plan and recall interval specifically to the patient's needs.35

Indeed, more important than overall risk level determination is the specific identification of individual pathological and protective, 'susceptibility' factors in order to plan customised preventive strategies adapted to individual needs and ability of compliance; a customised preventive care plan aims to cou terbalance individual pathological factors by strengthening individual protective factors.37 Structured protocols and forms may help in the systematic assessment of such multiple caries susceptibility factors in practice and aid in appropriate care planning and in objective record-keeping over time.31,38 Afuakwah and Welbury also showed that improving documentation positively influences the patients' adherence to their individualised protocol for preventive care.39

Recently, clinical outcomes studies have been published on the use of CAMBRA in the university teaching clinic setting. Doméjean et al. presented data on 2,571 patients over a period of six years who returned for follow up.40 The proportion of patients who went on to have new cavities in each of the risk categories was 24, 39, 69 and 88% for low, moderate, high and extreme risk respectively, demon strating validation of the risk/susceptibility assessment procedure. A subsequent outcomes assessment in the same clinic in 2,724 patients produced similar validation.41 Further, that study reported a 20% reduction in caries for those high-risk patients who used a combined chlorhexidine/fluoride therapy versus those who did not accept the therapy. In a subset of the same population who were on public assistance and used the products there was a 38% reduction in caries versus those who did not.


The gap between fundamental science and clinical practice

Several questionnaire studies assessing the use of risk/susceptibility assessment in everyday clinical practice highlighted that CRA has been poorly implemented into practice.42,43,44,45 One undertaken among a randomised sample of French general dental practitioners (GDPs) showed that, in 2015, approximately 38% of the respondents claimed not to use any form of CRA routinely.44 Those results compare regrettably to the 31% obtained among a network gathering of American and Scandinavian practitioners.42 The situation in Japan seems to be even worse with 74% of Japanese dentists claiming not to use CRA.45

The use of CRA in everyday clinical practice seems to be influenced by the oral healthcare practitioners' demographic characteristics. The French survey showed that CRA was used more by GDPs who had recently participated in a CPD course, those who read scientific articles on the topic and females.44 Despite structured protocols/forms to help systematic CRA in practice, and to aid in appropriate care planning, among those French GDPs who claimed that they assessed the caries risk of their patients, less than 5% used such forms.44 This compares unfavourably to the 17% reported by Riley et al. in the USA and Scandinavia for adult patients, but is below the 31% recorded among Japanese GDPs.42,45

In the discipline of caries management and MID, the gap between science and practice is not limited to risk/susceptibility assessment, but includes an early restorative threshold for lesions that could have benefited from non-invasive preventive therapies, lack of therapeutic sealant placement in non-cavitated lesions and iatrogenic dentine excavation in deep carious lesions.46 The lack of implementation of CRA into routine practise may be multifactorial. It can be hypothesised that the lack of clear-cut validation of any CRA protocol/system may disincentivise their routine use. Despite the evidence being weak, it can be argued that the lack of financial recognition/incentive may discourage oral healthcare professionals to change their clinical behaviour with respect to MID concepts in general.47


CRA is an essential component of the individualised MI oral healthcare care plan. The development and the validation of risk/susceptibility assessment models/protocols are needed to help oral healthcare practitioners to customise their care plans according to the individualised needs of their patients, case by case. Moreover, proper documentation may help enhance the patients' compliance with the protocol for preventive care plans. The specifications of the 'ideal' caries risk/susceptibility assessment protocol are:

  • The capacity of predicting the occurrence of new carious lesions and the progression of existing ones, in various clinical settings and populations (different ages: children, adolescents, adults, elderly; different health conditions; different caries prevalence regions/countries)

  • The capacity to educate and engage the patient and thus motivate them to take responsibility of and value their long term oral healthcare and enhance his/her adherence to preventive care plans (the time devoted to CRA at chair-side is a time for communication, explanation and engagement about deleterious behaviours in terms of dental caries)

  • To be an affordable/inexpensive, quick, user-friendly, and easy to understand tool.

There is a need for prospective clinical studies demonstrating that such assessments improve care planning outcomes in terms of a reduction of the occurrence of new carious lesions and the progression of existing ones with associated healthcare economics in different clinical practice settings and in different populations/countries. However, such randomised controlled trials (the highest form of evidence-base) will always be complex, if not impossible, to be carried out due to the large numbers of variables to control and the time taken to observe changes in risk/susceptibility in populations and individuals. Outcome assessments will likely be the strongest evidence available upon which to build and strengthen clinical practice. The limited results already available support CRA concept dissemination and CRA implementation into clinical routine practice to target the individualised needs of each patient in terms of care planning and provision (from prevention to restorations). Further studies are likely to provide even stronger support for this major change in clinical practice for the improved oral health of our patients.