The management of non-cavitated carious lesions has two approaches. The invasive (mechanical) approach uses the traditional “drill and fill” concept to restore the carious lesion even though the lesion can be reversed or arrested before it is cavitated. The non-invasive approach uses preventive-directed procedures such as sealants and fluoride-containing materials .
5.1. Invasive Approach (Mechanical)
In the beginning, caries were diagnosed with visual, tactile, and radiographic methods,which have shown moderate specificitybut low sensitivity .The mechanical approach, using “drill and fill” procedures with ahigh-speed rotary cutting instrument to manage caries,has been used for decades in dentistry. Moreover, dentists have been guided for more than a century by the concept of extension for prevention, which was introduced by G. V. Black . In addition, the use of a sharp instrument to detect carious lesions leads to breakage of the enamel surface and starts the cavitation of the tooth, which is not a reversible stage . Most dentists usually choose to restore lesions that appear to exceed the dentino-enamel junction in the radiograph.However, most of these lesions can be treated with preventive therapy, since they are not yet cavitated. Restored teeth are more vulnerable to recurrent caries, which will decrease their longevity.As a result, a surgical approach can lead to the unnecessary removal of tooth structures and eventually lead to more extensive treatment, such as root canal therapy .
While considering the non-invasive or micro-invasive modalities, it is worth emphasizing that there will be cases in which the invasive approach is needed to arrest the progression of caries. The caries risk status of the patients as well as the finances, transportation, behavior, and compliance of the patients are all determinants of which approach is preferable .
5.2. Non-invasive Approach (Minimally or Micro-invasive)
The adoption of non-invasive approaches in the management of these lesions can preserve dental tissues, thus increasing tooth longevity . Ekstrand et al. in 2012 emphasized in their study the fact that deciding on the correct option for restoring smooth surface carious lesions should be based on whether the lesion is cavitated or not. The preventive therapy for non-cavitated lesions should aim to arrest and remineralize the lesion .
Consequently, the non-invasive approach to manage dental caries is defined as the clinical, evidence-based prevention and cause-related approach to dental caries, along with comprehension of the histopathological carious process as well as the development of diagnostic technologies and adhesive, bioactive restorative materials .
Dorri and his colleagues in their Cochrane systematic review in 2015 differentiated between non-invasive and micro-invasive (minimally invasive) approaches. These treatments aim to control the biofilm through practices carried out at home by the patient (e.g.,tooth brushing,flossing) or through professionally applied treatments that enhance mineralization of the carious lesion, like topical fluoride. In contrast, the micro-invasive approach includes conditioning the tooth surface with organic acids,which will eventually cause the loss of few micrometers of tooth enamel (e.g.,sealants and resin infiltration) . According to Santamaria et al. in 2017, non-invasive biofilm-control-based caries management modalities for treating carious primary teeth are becoming common, which provides potential benefits for conserving tooth structure by delaying or minimizing the need for operative procedures .
This is supported by the recommendation of the consensus statement released jointly by the European Federation of Conservative Dentistry, the European Organisation of Caries Research, and the German Society of Conservative Dentistry. They recommended considering non-invasiveas well as micro-invasive measures to managenon-cavitated carious lesions,while taking care to tailor the treatment plan for every patient according to his caries risk status .
5.2.1. Self-management and Home Measures
The process of controlling caries starts at home. This depends on three factors:a tooth-friendly diet; fluoride use at home; and regular teeth brushing to manage the biofilm. All these factors can reduce the caries risk on the individual level. Fluoridated toothpaste in particular can also arrest non-cavitated carious dental lesions . The prescribed dose of 5000ppm fluoride in toothpaste was recommended by the ADA to arrest non-cavitated carious lesions only in the root surface caries of permanent teeth only.However,using a 0.2% sodium fluoride mouthrinse once per week was strongly recommended to arrest non-cavitated carious lesions on the occlusal surfaces of primary and permanent teeth .
5.2.2. Fluoride Varnish
The effect of fluoride varnish on primary tooth occlusal enamel caries was evaluated by Autio-Gold and Courts in 2001 in a randomized sample of children. The experiment group received fluoride varnish at the baseline and after four months, while the control group received no professional fluoride applications. Nine months later, the experiment group showed that 81.2% of lesions became inactive, 2.4% progressed and 8.2% did not change. With this statistically significant difference, the authors concluded that the fluoride varnish applications may be an effective measure in reversing active pit-and-fissure enamel lesions in the primary dentition .
In contrast, Johansson et al. in 2014 evaluated the effect of fluoride varnish on occlusal caries in primary molars in a split-mouth study.However, they stopped the selection of carious lesions due to the continued progression of caries, which would lead to ethical conflicts . In addition, Turska-Szybka and his team found that the fluoride varnish alone showed lower results when compared to a combination of fluoride varnish with other non-invasive materials on smooth surface non-cavitated lesions .This can bring the use of fluoride varnish alone to manage the non-cavitated carious lesions into question especially in the occlusal lesions although, it is easily applied and more acceptable by children.
5.2.3. Acidulated Phosphate Fluoride (APF) Gel
The acidulated phosphate fluoride gel was assessed as a caries-preventive agent in a high-risk group of school children. Agrawal and Pushpanjali in 2011 conducted the study in two schools randomly selected from a list of schools catering to an underprivileged area. Children who had three or more incipient (occlusal, lingual, or buccal), cavitated primary, or secondary carious lesions were enrolled in the study. Follow-up examinations were performed at 6 and 12 months, which showed a significant difference in incipient carious lesions between the experimental and control groups. Accordingly, they suggested that a biannual APF gel application is an effective preventive measure in reversing incipient carious lesions .However, this was a field trial, and there might be unseen confounding factors affecting the results, which might change if the gel was applied individually. Moreover, its acidity and application technique make it not the most preferable material approach.
5.2.4. Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP)
Bailey et al. in 2009, conducted a clinical trial on post-orthodontic whitespot lesions to test whether more lesions would regress when CPP-ACP paste was combined with fluoride toothpaste and supervised fluoride mouthrinse for 12 weeks. Their results showed that asignificant31% of lesions regressed with CPP-ACP paste . However, Altenburger et al. in 2010 evaluated the effectiveness of CPP-ACP on the fluorescence of initial carious lesions in pits and fissures.They randomly recruited 32 participants, who showed DIAGNOdent values between 15 and 29 in premolar and molar teeth, and instructed the study group to use CPP-ACP in addition to 1450ppm fluoride toothpastedaily. The result of this trial showed significantly less laser fluorescence after 15days, while it did not significantly differ when evaluated visually . Moreover, other clinical trials measured the effectiveness of CPP-ACP application in preventing dental caries in primary teeth and reversing white spot lesions afterdifferent follow-up periods, and they found that it had no significant effect when compared to the use of fluoridated toothpaste alone [57, 58].
The results of the above-mentioned studies are supported by the conclusion of the recent systematic review done by Fernández-Ferrer et al. in 2018 and by the recommendations of the ADA,which concluded thatCPP-ACP toothpaste has no positive effect on enamel lesions and discouraged its use if other measures are accessible [59, 50]. Despite these results, it could be considered as an adjunctive tool in the dentist’s box if he has no other choice.
5.2.5. Pit and Fissure Sealants
Florio et al. in 2001 and Honkala et al. in 2015 studied the efficacy of fissure sealants as a method of treatment for incipient occlusal caries. After one year, both studies found the fissure sealants showed a significantly higher arrest of caries when compared to fluoride varnish. They concluded that fissure sealants were able to arrest the progression of occlusal caries and were better at preventing caries progression than fluoride varnish alone [60, 61].
This is compatiblewith the result of a split-mouth study designed to evaluate the efficacy of infiltrating, sealing, or fluoride varnishing on occlusal surfaces with initial caries lesions. Lesions were randomized, then infiltrated with resin and varnished, sealed and varnished, or only varnished. By following up with radiographs, the investigators concluded that infiltration and sealing occlusal surfaces with initial carious lesions on primary molar teeth had high efficacy in arresting caries progression .
In addition, Wright et al. in 2016 reviewed the available clinical evidence regarding the effect of dental sealants for the prevention and management of pit-and-fissure occlusal carious lesions in primary and permanent molars. With moderate-quality evidence, theyfound that the participants who received sealants had a reduced risk of developing carious lesions in occlusal surfaces of permanent molars compared with those who did not receive sealants, after 7 or more years of follow-up. They concluded that sealants are effective in preventing the progression of non-cavitated carious lesions . The only disadvantage of the sealant on the occlusal lesions is that it is technique-sensitive and needs close follow-up and maintenance.
The sealant has asubstantial limitation which is that it is not applicable in the proximal lesions.However, in a recent, randomized clinical trial with 2 years of follow-up, an innovative approach was used to manage proximal carious lesions using the separation and sealing techniques. The investigators aimed to seal the proximal incipient carious lesions at the same visit, using a metal separator between the proximal surfaces of the posterior permanent teeth. They measured the efficacy of the sealing in arresting caries and evaluated the acceptance of 48 patients. They pointed out that the separation enabled for more accurate diagnosis,whether there was cavitation or not. They found that the test group showed a significant caries arrest, and the separation was well accepted by the patients. Therefore, they recommended single-session separation for the diagnosis and sealing of proximal caries lesion . This study might change the traditional way that we use sealants for occlusal surfaces only, but it needs more investigation. This can extend the use of sealants to proximal lesions.
5.2.6. Resin Infiltration
Caries infiltration with a resin material is a micro-invasive technique widely used to arrest non-cavitated proximal carious lesions of both primary and permanent teeth, and it is used as an alternative to invasive restorations.However, it has to involve early detection of lesions and appropriate monitoring of the caries risk. Its function is based on the penetration of low-viscosity light-curing resins, called infiltrants, into the pores within the enamel lesion. This approach fits perfectly with the concept of minimally invasive treatment because it preserves the tooth structure and it can be achieved in a single visit, as well as creating a barrier inside the lesion by replacing the mineral lost with a low-viscosity light-curing resin [45, 65-67].
In 2011, Borges et al.evaluated non-surgical interventions such as the consumption of gum containing case in phosphopeptide-amorphous calcium phosphate (CPP-ACP), resin infiltration, and fissure sealing. Although in a few cases an invasive approach is needed to arrest caries progression, the non-surgical approach generally provides potential benefits that include conserving structure by delaying intervention or minimizing operative procedures. They concluded that resin infiltration and other non-invasive methods were effective in treating non-cavitated caries lesions, and they recommended the adoption of non-invasive approaches in the management of these lesions to preserve dental tissues, thus increasing tooth longevity .
In 2012, Meyer-Lueckel et al. conducted a split-mouth control trial to investigate the 3-year efficacy of resin infiltration (Icon, pre-product; DMG, Hamburg) to arrest the progression of proximal non-cavitated carious lesions, as compared with placebo treatment. In their sample, they studied the lesions that extended radiographically into the inner half of the enamel up to the outer third of the dentin of permanent teeth. The patients were given general advice on oral hygiene practice and diet habits.Following up after 3 years, they concluded that the infiltration of proximal carious lesions can be an efficacious approach to reduce lesion progression .
A systematic review was conducted by Domejean et al. in 2015, aiming to evaluate the in-vivo scientific evidence of the ability of resin infiltration to arrest proximal non-cavitated carious lesions. They found significant differences in caries progression between their test and control groups, indicating that resin infiltration may inhibit the carious process. Therefore, they concluded that resin infiltration appeared to be an effective method to arrest the progression of non-cavitated carious lesions .
More evidence was found by Dorri et al. in 2015 in their systematic review and meta-analysis, which included randomized controlled trials of at least six months’ duration to compare micro-invasive treatments (i.e., sealants and resin infiltrating) for managing non-cavitated proximal dental decay in primary teeth, permanent teeth, or both, versus non-invasive measures (i.e., fluoride varnish and floss). They performed a meta-analysis, which pooled the most sensitive set of data, showing that micro-invasive treatment significantly reduced the odds of lesion progression compared with non-invasive treatment (e.g., fluoride varnish) or oral hygiene advice (e.g., to floss).They analyzed eight trials held in seven different countries that randomized 365 participants in a split-mouth design. These studies evaluated the effects of micro-invasive treatments in permanent dentition and on primary dentition, with a follow-up period ranging from one to three years. The main outcome of all these studies is the evaluation of lesion progression using radiographs. Within the limitations and the increased risk of bias, the study concluded that the micro-invasive treatment of proximal caries lesions arrests non-cavitated enamel and initial dentinal lesions and is significantly more effective than non-invasive professional treatment or advice . Based on that, resin infiltration is an effective approach to control the non-cavitated proximal carious lesions but not to the occlusal lesions. However, it might not change the lesion radiolucency therefore it still could be mistakenly diagnosed as carious lesion by another dentist if no clear history.