Minimal intervention dentistry (MID): a review of the evidence

Dental decay is one of the most prevalent chronic diseases worldwide, causing localized demineralization and dissolution of calcified tooth structure (Lundeen et al., 2002) ; Development of the historical rules of dentistry by Dr.G.V Black “father of modern dentistry” in the late 1800’s focused on the “extension for prevention” concept, Where treatment of a dental decay on a tooth suggested inclusion of sound pits and fissures in the cavity design to remove possibility of further dental decay. This was previously the main concept followed by restorative dentistry, the G.V black principles in treating tooth decay was based on little knowledge of the disease and focused on treatment of the disease rather than its cause. (Jingarwar et al., 2014).

With advancements in caries detection methods, prevention modalities, Adhesive restorative materials and the understanding of the caries lesion progression on microscopic level , the philosophy of Minimal intervention dentistry(MID) has evolved (Murdoch- Kinch CA, 2004),

MID is then defined as a philosophy of clinical care concerned with the initiation, early detection of disease, and earliest possible cure of disease on microscopic levels, followed by “minimally invasive”, patient-friendly treatment to repair irreversible damage caused by such disease. (Mickenautsch, 2005).

Principles of MID ; 4 R’s

Recognition: Early detection of the disease & Caries Risk Assessment of the patient.

Reduction: Decreasing the susceptibility of the patient to the disease.

Regeneration: Also remineralization of calcified tooth structure.

Repair: Conservative treatment methods for surgical repair of the tooth structure.

(Walsh & Brostek, 2013)

Early diagnosis and caries detection are the cornerstone of minimal intervention dentistry they have a big importance because it facilitates a big range of nonsurgical parameters for therapy in the dental health.

Starting with the oldest device to diagnose caries apart from the dental probe, which is the x-ray machine, radiography has shown to be very reliable in detecting proximal caries but not as reliable with shallow occlusal caries particularly in the enamel outer one third (Angnes et al., 2005).

This led to the development of new and more advanced devices to be used in adjunct to the traditional dental probe and X-ray :-

Fiber-Optic trans-illumination(FOTI) device: High intensity light that is focused narrowly to penetrate the tooth permitting the recognition of different densities and thus identifying caries, (FOTI) was shown to be reliable in detecting occlusal and buccal caries however when looking at small proximal caries, bitewing radiography was significantly more sensitive in caries lesion detection. (Rochlen et al.,2011)

Laser Fluorescence-DIAGNOdent: A source of monochromatic light of around 655 nm wavelength passes through the enamel tooth structure unhampered, this device has the ability to excite bacterial protoporphyrin which results in the fluorescence, an advantage of this is that changes in the fluorescence can be quantified which will describe the presence and the severity of the carious lesion (Rochlen et al.,2011), yet these readings can be confounded by many restorative materials and the presence of discolorations or stains on the pits and fissures of the tooth in question. (Lussi et al.,2001)

Quantitative Light-Fluorescence(QLF): The dentin of the tooth is fluorescence by a specific wavelength of light , the image captured is quantified using a digital imaging software for the loss of fluorescence and surface area, when this data is measured it will allow the monitoring of the progression of caries, Nevertheless these units are limited to caries recognition on surfaces that are readily accessible and they are complicated to use, making QLF rare to find in the private practice (Stookey et al.,2005).

In conclusion the specificity and sensitivity of different techniques and devices were highly controversial in the literature and the consistency was lacking (Gomez et al.,2013)

Tri Plaque Gel/Disclosing agent: This is a material that can show different tones of colors to highlight the thin plaque, mature plaque and cariogenic plaque, this technique can provide a tool to motivate the patient by showing them the areas they frequently missed during their oral hygiene practice. (Walsh et al., 2013)

Visual tactile methods: Without properly validated and a reliable caries detection technique or device, Visual-tactile method has been emphasized. Furthermore, with the modern concept of (MID) and shift from surgical approach by G.V Black’s classification which only included cavitated dentine, thus caries indices including enamel lesions were developed such as Mount and Hume and International Caries Detection and Assessment System (ICDAS). (Frencken et al., 2012)

Caries Risk Assessment(CRA): Caries disease is a multi-factorial and very dynamic process in nature, Caries risk is defined as the development probability of future caries, it serves as the foundation for the patients prognosis for caries and is embodied in the individually tailored oral health management plan provided to the patients. (Frencken et al., 2012)

On the other hand, risk assessment for such dynamic disease is very challenging specially when (CRA) only provides a snapshot and risk factors can change in time. (Frencken et al., 2012), Harris et al., (2004) stated that past and present caries experience is still the most powerful and accurate predictor of future risk of developing caries.

Decreasing the susceptibility of the patient to the disease starts with the dental plaque biofilm, it was found that disturbance of the dental biofilm by mechanical brushing with a fluoridated toothpaste daily is regarded as an effective measure to control caries lesion development (Peters et al., 2010) , However, most patients fail to effectively remove dental plaque from high risk areas (Fontana & Cabezas, 2012), therefore in regards of paediatric patients horizontal brushing method is suitable (Ceyhan et al., 2018) along with parental supervision until the age of 7 (AAPD recommendations, 2016).

Diet counseling: Organic acid production from the metabolism of sugars(diet) by anaerobic bacteria was found to be the primary cause of demineralization of the tooth structure. (Bang et al., 1972), Moynihan et al.,(2014) found that a people with a sugar intake of greater than 10% of total energy compared to lower than 10% had higher incidence of caries, however Fontana et al.,(2012) states that because of the increase in fluoride consumptions it is now difficult to set a clear-cut correlation between sugar consumption and caries development, nonetheless World Health Organization(WHO) recommendations for sugar intake is suggested to be less than 10% of total energy intake and less than 5% when applicable. (Moynihan, 2016). and here where the use of a Diet diary becomes important, patients at high risk can provide the clinician with the diet record that can be effective in providing a picture of the dietary issues that can be linked to the child’s oral disease. (Watt et al.,2003), Regardless, Arheiam et al., (2018) states that diet-diary was perceived to carry a potential for blame and embarrassment for parents and levels of their commitment was affected by their priorities and values.

Sugar Substitutes: Xylitol is considered to reduce caries by providing higher salivary flow (Janket et al.,2019) and by inhibition of the growth of Streptococcus mutans (Bradshaw et al., 1994), On the other hand, Rethman et al.,(2011) stated that the quality of the research done on the benefits of Xylitol in caries reduction was low, therefore more research is needed.

Chlorhexidine: One of the most prescribed antiseptic in the dental practice, it is shown to be very effective when used with adjunction with mechanical oral hygiene. (Varoni et al.,2012), caries-inhibition using chlorhexidine varnish when applied every 3-4 months was moderately effective however 2 years after the last application its effect diminished (Zhang et al, 2006), Walsh et al., (2015) states that there is lack of evidence in Cochrane library to whether agree or disagree with the effectiveness of chlorhexidine in caries control therefore it is regarded as an inconclusive evidence.

Ozone: Tri-atomic state of di-oxygen in a gas form with a sterilizing effect and the potential for killing cariogenic bacteria which leads to arresting of the dental caries (Brazzelli et al., 2006), Dähnhardt et al.,(2006) conducted a study comparing occlusal caries lesion treated with ozone gas and control group, tactile hardness increased at 4,6, and 8 months compared to no increase in hardness in the control group, another study by Atabek et al., (2011) compared the effectiveness of ozone with or without adjunct use of remineralization agents and found that 90% of the lesions treated with ozone alone remineralized and 95% of the lesions treated with ozone and remineralizing solution reversed, therefore the use of ozone have shown to be an effective method for caries reversal, However, Duggal et al., (2012) states that ozone treatment had no additional benefit in caries reversal with an existing remineralizing therapy, In regard of safety the national institute of clinical guidelines(NICE) advise against the use of ozone in caries management, Although Merve Erkmen et al., (2013) found the Heal zone device to be safe to use, In conclusion the effectiveness of ozone therapy is still controversial in the literature and lack of quality evidence necessitates more research (Srinivasan& Amaechi, 2019).

Fissure Sealants: Biofilm accumulation on the openings of pits and fissure is responsible for the initiation of caries (Simonsen et al., 2011). The AAPD (2016) states the sealing of pits and fissure using sealants was shown to be more successful in reducing dental caries compared to unsealed teeth, the longevity of resin based dental sealants compared to glass ionomer sealants was higher (Locker et al., 2003), On the other hand, Leal (2014) found that resin-based materials require very good control of humidity. A recent study by Feifei et al., (2020) comparing the prevention effectiveness of dental sealants with fluoride varnish found that there was no significant statistical difference on caries incidence or occlusal DMFS between fluoride varnish and sealants group.

Fluoride(F): The mechanism suggested for F is that these ions gets incorporated into the hydroxyapatite crystals in the teeth, making them more resistant to demineralization by the acid pH (Doumit et al.,2017). Two methods of F systemic and topical; pre-eruptive and post-eruptive, it was hypothesized that F incorporation in the enamel tooth matrix when ingested pre-eruptively was the “optimum solution” to increase acid resistance potential hence reduce caries incidence (Fejerskov 2004), However, it is known that it only gets incorporated in the outer enamel surface and this does not withstand the dissolution of the acid (Featherstone 2000). Furthermore, the centers for Disease Control (CDC) (1991) stated that F predominantly prevent caries post-eruptively by the topical contact of the oral cavity with the ingested form of F, although more than 25 countries support the program of water fluoridation as a public health measure to reduce the dental caries. This is done in order to reach the optimal amount F in water which is around 0.7 ppm (Armfield, 2010; U.S. Public Health Service recommendations, 2015).On the other hand, some countries vote against it. Their whole point is that F in water is considered a drug and there will be an ethical issue that question the autonomy of the patients. In addition, some studies stated that the F could affect the IQ of the child patients, as well as the risk of dental fluorosis. (Council of Europe 1997; GMC,2008).

Topically applied F have a lot of forms from toothpaste, gels, foams and rinses; where F containing toothpaste is found to be the most common self-applied form worldwide (Clark et al.,2014), AAPD (2013) suggested a Pea size fluoridated toothpaste(0.25mg of F) as an amount used when brushing for children age 3-6 years old and a smear layer of a size of a rice grain(0.1mg of F) for children below 3, this was developed because of the fact that children swallow 80%-100% of the toothpaste during brushing (Cochran et al., 2004), Hence reducing the risk of fluorosis. Clark et al., (2014) suggests that F from rinses helps in dental cavity prevention, However the CDC in (2019) discouraged the use of mouth rinses in children below 6 years of age because of the increased risk of fluorosis from excessive swallowing. Professionally applied F in office include Acidulated phosphate fluoride APF: 1.23%, Sodium fluoride: 2%, Sodium fluoride NaF Varnish 5%, 2.26%, Fluoride varnish and gels have a great potential to decrease the incidence of dental caries (Marinho, 2003). Delbam and Cury (2002) compared APF with neutral fluoride gel they found that APF increased remineralization potential and increased F in enamel, Furthermore the ADA (2006) recommended F Varnish application every 6 months for patients with moderate risk and every 3 months for high risk, However in South Africa the low risk patients are recommended to apply F varnish or gel every 6 months, Moreover, The ADA in 2016 only recommended 2.26% F varnish for children younger than 6 years of age. In conclusion topical applications of F are infrequent 3-to-12 months interval therefore the risk of developing dental fluorosis is very low (CDC, 2019) and the most efficient way to prevent caries is by using fluoridated dental materials (Sun et al.,2020).

Silver Diamine Fluoride(SDF): Usually in 38% concentration where it contains 24.4%-28.8% silver ion and 5% to 5.9% fluoride; Silver kills the cariogenic bacteria while the fluoride acts to remineralize the tooth surface (Zaho et al.,2018), Besides, cavity treated with SDF 38% had arrest rate of 70% (AAPD, 2018), Advantages of using SDF include the reduction of hypersensitivity, arresting of dental caries, efficiency and its inexpensive, On the other hand, the disadvantages are black discoloration, metallic taste and irritation (Mei et al., 2016), Besides, Recent systematic review said that application of potassium iodide after SDF could potentially reduce the risk of staining in the short term (A Roberts et al., 2020), In conclusion the benefits of SDF outweigh the drawbacks in most cases (AAPD, 2018).

Casein phosphopeptide–amorphous calcium phosphate (CPP–ACP)complex: A nano-complex from protein in milk also called Tooth Mousse; enhance the remineralization by increasing the concentrations of calcium and phosphate in an amorphous state and increases their uptake (Prestes et al., 2013),In-situ and clinical study by Yengopal et al., (2009) states that CPP-ACP provides short-term remineralization effect, In Addition, a recent systematic review states that CPP‐ACP is effective in preventing and treating white spot lesions (Pithon et al., 2019) Yet, when comparing combination of fluoride and CPP-ACP with fluoride monotherapy in treating smooth surface lesions there was no significant difference in the effectiveness, The bottom line, despite the fact that CPP-ACP being a functional remineralization material, More High quality randomized clinical trials are needed to provide stronger evidence for its effectiveness (Wang et al.,2020).

Resin Infiltration: An approach of treating non-carious proximal and smooth surface lesions by the penetration of low-viscosity resin material in the subsurface of the enamel porosities (Lasfargues et al., 2013), Ekstrand et al., (2011) stated that combination of resin infiltration and F varnish was more effective compared to F monotherapy, Additionally, A recent RCT showed 82% lower risk of caries progression in patients treated with resin infiltration compared to no infiltration(control) (Sarti et al., 2020), Meyer-Lueckel et al., (2007) found that the infiltration penetration greatly enhanced when the conditioned surface is treated with hydrochloric acid HCL for 120 seconds, therefore, Pitfalls in proximal application of resin infiltration is the need for proper isolation of the neighbouring tooth surface with a barrier to allow etching plus proper Rubber dam placement for adequate prevention of contamination by saliva (Lasfargues et al., 2013), furthermore, proximal application requires 2 visits for insertion of separation orthodontic band to create space for to carry out infiltration (Ekstrand et al.,2010)

Air-Abrasion: A technique of conservative caries removal that involve bombarding the tooth surface with aluminum oxide particles(alumina) carried by a stream of air at high velocity (Jingarwar et al., 2014), the pressure of these particles is about 7-11 Atm(Atmospheric pressure) and size of the alumina is usually from 27-50μm, In Addition, the particle size and pressure can be adjusted to allow the practitioner to do different procedures (Hegde & Khatavkar, 2010). Air Abrasion is indicated in detection of pit and fissure caries, removing old restorations, superficial enamel caries removal and surface treatment for adhesive materials, On the other hand, Its use is contraindicated in patients with respiratory diseases such as asthma because of the fear of dust inhalation which can trigger a medical emergency (Hegde & Khatavkar, 2010), Besides, Using air-abrasion produce no pain so it reduce the need for local anaesthesia, Additionally, produce no noise or vibrations which is especially applicable in anxious patients, However, it requires special suction unit and water jets.

Air abrasion tends to remove sound tooth structure during cavity preparation along with lack of tactile sensation, so it requires special training. (Jingarwar et al., 2014), Hicks et al., (2001) found that air-abrasion cavity preparation had more rounded line angles compared to conventional drilling, thus, air-abrasion cavities can decrease internal stress and increase longevity of the restoration, However, the literature is conflicting and more research is needed to support the effectiveness and safety of Air-Abrasion.

Sono-Abrasion: This technique utilizes high frequency sonic-airscalers with modified tips which describe an elliptical motion, mainly to remove interproximal caries without physical excise of dentine rather abrading it with an oscillating tip, it was found rather beneficial in the proximal preparation in order to protect the adjacent tooth surface from iatrogenic injury done by using conventional burs (Jingarwar et al., 2014), furthermore, it was shown that Sono-abrasion is more minimally invasive in the removal of caries compared rotary handpiece and the debridement of caries is more controlled and selective (Ntovas et al.,2017).

On the other hand, Decup&Lasfargues (2014) reported that ultrasonic technology demonstrated higher risk of enamel micro-cracks and According to Van Meerbeek et al, (2003). the adhesive performance of sono-abraded surfaces is equivalent to that obtained after using conventional diamond burs, Although the literature did not confirm these results, Finally, the literature shows inconclusive evidence regarding the efficiency of the use of sono-Abrasion in the clinical practice and more research is needed to support it (Ntovas et al.,2017).

Lasers: Many uses for lasers in the modern dentistry include diagnosing of carious lesions, prevention of dental caries and restorative applications (Strakas & Norbert, 2018), lasers are considered efficient to use in minimally invasive conditions since the laser eradicate caries affected tissue which has higher water content compared to sound tooth structure (Coluzzi,2018), Olivi&Genovese (2011) described that using lasers minimize the anxiety of the patient and provides a more comfortable treatment since the non-contact feature of laser with the tooth structure produce no sound or vibration, Another advantage reported by Rezaei et al., (2001) is that the enamel surface of laser treated cavities are more acid resistant than conventionally treated cavities, However, the use of fluoride varnish along with laser treatment shows more effective results when compared to lasers alone (Pinar et al., 2019), besides, some of the Limitations of using laser include the high startup cost, additional training of the clinician and the fact that different functions of each wavelength requires more than one laser device (AAPD, 2017), In conclusion, the evidence of the clinical performance of the laser compared to conventional bur is still controversial in the literature and more research is needed (Dilsad et al., 2020).

Chemo-Mechanical caries removal: In general it’s the gentle removal of carious dentine softened by the chemical solution (Beeley et al., 2000) which is either sodium hypochlorite based(GK-101,Caridex or Carisolv) or Enzyme based(Papacarie, Cariecare), Indicated in uncooperative patients with deep carious lesions (Peric et al., 2009) and can be of a clinical significant in patients with infectious diseases i.e. Tuberculosis where it will reduce the spatter found with conventional rotary handpiece hence reducing risk of infection (Harrel et al.,2004). Sodium hypochlorite-based materials were introduced in 1975 by habib et al., which consisted of 5% sodium hypochlorite, these materials like GK-101, Caridex system are not used now anymore because of the large volumes of liquid(200-500ml),the length of the procedure(10-15 min) and the cost of their delivery system hence limited their use (Jingarwar et al., 2014), that’s why they introduced Carisolv which was developed to resolve problems with the older generation, this system uses gel form rather than liquid form in low volume, found easy to apply (Mithra et al, 2017) and doesn’t require the use of special delivery systems (Hammama et al, 2014), when carisolv was compared to conventional drilling it was found that it reduced pain, was more selective in caries removal which made it less invasive (Viral et al.,2015), However, In shallow pit and fissure caries the use of Carisolv is limited since the hand instruments can’t access the narrow fissures and it’s more feasible with bur and a handpiece (Jingarwar et al., 2014). Enzyme based materials included Papacarie and Carie-care contains papain gel; a protein extracted from papaya fruit which acts only on the necrotic tissue due to the presence of plasma antiprotease, healthy tissue is not affected due to the presence of Antitrypsin which protect it from the papain enzyme, Although Carie-care is more economical (Sontakke et al., 2019), Papacarie was found more effective in reducing bacterial remnants after caries removal (Sahana et al., 2016), Furthermore, El-Tekaya et al., (2012) found that Papacarie is remarkably more reliable in the reduction of cariogenic bacteria in the dentinal tubules of primary teeth compared to both Carisolv and hand excavation method.

Atraumatic restorative treatment(ART): A patient friendly approach that focuses on the exclusive use of hand instruments in restorative procedures followed by the filling of high viscosity glass ionomer cement, ART was originally developed for use in underserved communities, its use is now expanded into the private practice of developed countries (Frencken,2014). ART function not only by restoring the carious lesion but also by sealing the pits and fissures prone to caries (Frencken,2017),therefore it was found quite useful in young uncooperative patients including special needs children when traditional cavity preparation is not available. (AAPD 2017) On the other hand it was contraindicated when the cavity can be accessed by hand instruments or when the pulp of the tooth is exposed (Frencken et al.,1997), A recent systematic review by De Amorim et al.,(2018) reported that the survival rates of single surface ART restorations for first and second year in primary teeth were 94.3% and 65.4%,respectively , However, another systematic review Dorri&Martinez-Zapat (2017) concluded that ART restorations carried higher risk of failure than conventional restorations, Although, this evidence is of low quality and high quality of research in this field is still needed.

Hall technique(HT): A minimally invasive restorative technique done without anesthesia or caries removal and no tooth preparation by using preformed metal crown(PMC) with glass ionomer luting cement (Lakshmi et al., 2018), the mechanism of HT is by changing the cariogenic plaque environment by sealing the lesion thus, isolating nutrients and arresting the process of demineralization (Kadaluru et al.,2012), Innes et al., 2015 stated that patients treated with HT compared to normal fillings found reduced anxiety on the dental chair, A Cochrane review reported that for symptomless vital teeth, sealing of the cavity had advantages over complete caries removal; by decreasing the chances of pulp exposure and having no detriment on restoration longevity (Ricketts et al.,2013), A study by Fontana et al., (2014) found that 97% of teeth treated with hall technique on a follow up of 15 months were successful, However some practitioners do not accept the fact of leaving active caries lesion behind and finds the reliability of this technique a question (Calache et al., 2016). In Conclusion, according to AAPD (2016) the evidence for the use of hall technique in comparison to conventional SSC after caries removal is controversial due to the shortage of reliable studies in that area.

Minimally invasive cavity designs: techniques using conventional rotary handpiece in creating a cavity design that minimizes the amount of tooth structure sacrificed.

Tunnel preparation: Preserving the marginal ridge by accessing the cavity from the occlusal plane of the tooth and creating what so called a “tunnel” (Murdoch et al , 2003), Applied when the caries is more than 2.5 mm away from the crest of the marginal ridge (Gunda et al, 2015), However it is clinically unreliable and the long-term success was shown to be low.

Slot preparation: In the presence of a carious lesion interproximally that is at least 2.5 mm or less away from the marginal ridge. (Gunda et al, 2015)

Replacement Vs. Repair: Whenever a patient shows in the dental office with a defective filling the practitioner is faced with a dilemma which is whether to replace or repair. Blum IR,(2011) suggested that repairing a filling could be more time and cost efficient, less invasive to the pulp and may not require local anesthesia when the repair is not extensive, Additionally, it was found that replacements can lead to potential damage to the pulp and increase in cavity size (Sharif et al.,2014), Kanzow&Wiegand (2019) stated that even after previous repairs or replacement of the filling, further repairs are the most suitable treatment for the survival of the restoration, On the other hand, in 75% of the cases dentists chose to replace over repair of defective dental restorations (Gordon et al.,2012), especially when the restorations were not originally filled by the same dentist (Bader et al.,1992), In conclusion, the decision is still based on subjective parameters which should include the patients caries risk assessment (Frencken et al., 2012) and is still difficult to decide (Yousef & Khoja ,2009), as minimally invasive approach suggests, the practitioner should consider repair rather than replacement, as it is still a worthwhile procedure to pursue (Frencken et al., 2012).

Conclusion: Considering the current understanding of the caries disease process which remains globally the most prevalent child disease. Preservation of the tooth structure remains of the uttermost importance in the paediatric dentistry field, where dentists should withhold from the direction toward the traditional “drill and fill” concept, Modern dentistry today must encourage more dental practitioners to seek the minimal intervention dentistry concept into their treatment approach, which will help in prevention of the disease, establish less invasive treatment techniques and empower the parents to take responsibility for their children’s well-being.