Atraumatic restorative treatment compared to the Hall Technique for occluso-proximal carious lesions in primary molars; 36-month follow-up of a randomised control trial in a school setting

In Brazil, there is still a high dental treatment need for children, with approximately 80% of them experiencing untreated carious lesions in the primary dentition [1]. The most common intervention for dental caries continues to be conventional restorative treatment [2] where carious dentine is removed with rotary instruments and the cavity filled with composite resins. Treatment can improve children’s quality of life as well as that of their families [3, 4]. The most common intervention for dental caries continues to be conventional restorative treatment [2] where carious dentine is removed with rotary instruments and the cavity filled with composite resins. Although the origins of dental anxiety are multifactorial [5, 6], the use of rotary instrument and local anaesthesia during dental treatment has been found to contribute to negative experiences and affect behaviour, increasing dental fear and anxiety in future dental appointments [7‐9].

Minimally invasive dentistry (MID) as an approach, should be the standard care for managing carious lesions [10], slowing the downward restorative spiral and reducing discomfort during the treatment [11, 12]. Approaches such as the Atraumatic Restorative Treatment (ART) and the Hall Technique (HT), neither of which require local anaesthetic nor the use of rotary instruments, fit in with MID principles.

ART [12, 13], using only hand instruments to remove carious tissue and prepare the cavity, has been commonly used in paediatric dentistry because it is associated with lower levels of anxiety, pain and discomfort, as well as greater acceptance by children, compared to the conventional treatment [14‐17]. In addition, ART can be delivered, without electricity, running water or rotary instruments and can be used in dental clinics and communities where access to dental equipment is limited. Good survival rates have been reported for single-surface cavities in both the primary and permanent dentitions [18‐21]. However, when used to restore multi-surface cavities, ART has shown lower survival rates, ranging from 93 to 12.2% of success after 3 years [18, 19, 21, 22].

The HT [23] involves placing a preformed metal crown over a carious tooth using glass ionomer cement (GIC) [24]. No tooth preparation or carious tissue removal is required eliminating the need for rotary instruments and local anaesthetic. The HT has become routinely used in many countries and is currently recommended in the American Academy of Pediatric Dentistry [25] and SDCEP guidelines [26]. The technique has lower or similar levels of discomfort when compared to conventional treatments [27‐29]. However, child self-reported discomfort has only been assessed in one study [27], showing no difference between children treated with conventional restorations using local anaesthetic, HT and non-restorative cavity control. The HT has been reported to have high success rates (over 90% up to 5 years follow-up) for restoring multi-surface lesions in children [30, 31]. However, there are no trials comparing the HT with different approaches in a non-clinical setting for treating children where dental facilities are not available.

This randomised clinical trial aims to compare tooth level restoration survival at 36 months (primary outcome) for ART and the HT carried out in a school setting to manage occluso-proximal carious lesions in primary molars [32]. Secondary outcomes are: OVD resolution after the crown is placed using the HT; child reported discomfort related to the treatment; children and their parents’ acceptance after the treatments; and child’s OHRQoL.

This randomised controlled trial seems to be novel in two respects. Firstly, ART was compared to the HT and secondly, the HT was carried out in a community setting with no access to dental facilities. The HT achieved similarly high survival rates to trials set in dental clinics (between 95 and 98% after 5 years) [29‐31, 37] and equivalent to conventional crowns [38]. At 3 years, the HT had a statistically, and clinically, higher survival rate in dentinal occluso-proximal, cavitated carious lesion dentinal carious lesions in primary molars than ART (HT = 93.4%; ART = 32.7%). In other words: the HT had almost 1/10 unsuccessful restorations compared to approximately 7/10 in the ART group over 3 years.

ART was developed to be carried out without a dental chair, rotary instruments, aspiration, air-drying or radiography to observe the lesion’s depth (with cavities’ size limitations). Although studies support ART for primary teeth occlusal lesions, showing high survival rates with around 90% after 3 years [19] and an annual failure rate of approximately 5% [12, 21], the survival rates in occluso-proximal lesions are lower varying across studies; from 93 to 12% after 3 years follow-up with a mean annual failure rate from 17% [12] to 25% [21] presented by three different systematic reviews [18, 19, 21], which included results of eight different clinical trials. Investigations into the association between ART restoration failure and operators’ level of experience have shown contradictory findings [33, 39‐42]. In this trial, the operators were one Specialist in Paediatric Dentistry and two Undergraduate Students, all trained in both techniques. Independent of the operators’ level of experience, restoration survival rates for the ART group were still low (32.7%) and within the wide range presented by these systematic reviews (from 93 to 12%) for restoration survival when using the ART. This also shows that ART survival rates are not as consistent as those observed with the HT.

The known side effect of a temporary OVD increase with the HT has been shown to resolve within 2–4 weeks [27, 34, 43]. Our results agree with this, showing a return to pre-treatment OVD within four weeks.

Until a few decades ago, conventional PMCs were available to paediatric dentists in Brazil. However, the conventional technique is complex, requiring local anaesthetic and tooth preparation. At the same time, less sensitive techniques and materials, especially tooth coloured materials such as GIC and resin composites, were developed. This led to a reduction in the market for dental companies selling PMCs causing discontinuation of crown availability. The higher clinical success (survival rate) of the HT than ART, means that if preformed metal crowns were available in Brazil, the HT could be a more feasible treatment option for multi-surface carious lesions in primary molars. However, aesthetics may be a concern for parents.

Patient-centred outcomes have been of growing interest, especially in paediatric dentistry [5, 14‐17, 14, 15]. The largest subset of them, patient-reported outcome measures (PROMs), allows patients to give their own perceptions rather than them being gauged, and reported, by the person providing the treatment who will bring their own cognitive biases. Even an independent assessor (who is not the care provider) can be inaccurate in reporting a child’s level of discomfort. Using a child appropriate measure allowing the child to rate their experience in a ‘safe’ setting away from the care provider, is likely to give them the best opportunity to represent their feelings and thoughts most accurately.

To increase the possibility that children felt able to report their experience (positive or negative), without feeling pressured to please their dentist or being embarrassed in front of other children, they were assessed using the WBFPS immediately after treatment but out of the presence of the dentist providing the treatment and other children. Although overall discomfort scores indicated that both treatments gave low levels of discomfort, children who had a separator and a HT crown placed rated a higher discomfort level compared to those in the ART group. Both the separator and crown have to be pushed over the tooth or (for the crown) the patient can bite onto a cotton roll to push it over the tooth. Both options require a degree of pressure. Although there was a statistically significant difference between the HT and ART scores for discomfort levels reported by children, in relative terms the scores were low with over 70% of the children reporting “no” or “very low” discomfort for both timepoints for the HT group and over 80% for ART. This is similar to a trial comparing children’s discomfort between three caries management strategies where over 80% of children reported “very low” or “low” discomfort for the HT and no statistically significant differences compared to the other treatments (non-restorative treatment = 88%; conventional treatment = 72%) [27].

Children and parents’ treatment acceptability high levels were high for children, with the majority (ART = 73.9% and HT = 81.8%) answering “strongly agree” and “agree” to all questions. However, parental acceptability for appearance differed, with around a quarter (24%) of parents in the HT group but only 1 in 20 (5%) in the ART group disagreeing with the statement “the appearance of my child’s new restoration does not bother me”. ART uses glass ionomer cement, similar in colour to teeth and might not be noticed when looking in the children’s mouth whereas the metal, silver, shiny HT crown is easily noticed and especially visible if placed on a first primary molar when the child smiles or opens the mouth wide. In a study where children and their parents’ opinions on dental restorations were sought [44], 10 out of 11 parents (91%) preferred an aesthetic material (composite resin or GIC). The authors speculate that this might be related to a concern of the parents regarding a visible sign of perceived “lack of care”. The obvious appearance of the silver crown did not seem to concern children. Only 5 (8%) (ART = 2; HT = 3) said they would not show their treated tooth to their friends. Although young children may be less aware of, or bothered by, the aesthetics of their teeth than older children or adults, they may also have different aesthetic ‘norms’ compared to their parents. There were no other differences in parent’s/carers’ opinions of the treatments, in common with another study [27].

Children had only one tooth treated and included in this trial and if they needed further dental treatments, they were referred to the public dental service. This is a potential limitation of the trial as treatment may have influenced children’s OHRLQoL and may explain the improvement in both groups’ OHRQoL at 6-month follow-up despite only a single tooth being treated. In a similar setting, ART treatment of carious lesions was found to lead to a greater improvement in children’s OHRQoL when compared to caries-free children [45]. The authors suggest that the children’s positive perception of their dental care might have influenced their OHRQoL.

The study was carried out in Brazilian children and this might also pose a limitation for generalising this study results for the secondary outcomes. As cultural differences are often present in different populations, the self-reported discomfort and treatment acceptance by children and their parents may differ if treatments are applied in a different setting, communities, population or culture.

Since this trial was conducted in the schools with no access to dental facilities, radiographs could not be performed and the real extension of the lesions could not be assessed. When considering a dental setting, it is very likely that a more accurate diagnosis related to cavities depth would be performed. Likewise, the dental setting would provide better resources as lighting and equipment for performing the restorations and it is unlikely the outcomes would be worse than the presented in this manuscript.

The protocol for this trial had not previously set out to investigate tooth exfoliation. However, early exfoliation of teeth treated with the HT was observed. This differed from a retrospective study evaluating the same outcome where no difference was observed within the same child [46]. Further information related to the contralateral teeth (if present/absent) was not collected when the study tooth was evaluated by the outcome assessor.

The clinical success and low re-treatment rate of the HT might influence parental acceptability and outweighed concerns over appearance. This change in acceptability has been found in a study weighing up the disadvantages of discolouration of teeth using silver diamine fluoride with other treatments [47]. Parents’ “tipping point” for accepting discolouration changed when faced with other options they considered less favourable (e.g. sedation or general anaesthesia).

Shared clinical decision-making allows the clinician and patient (or parents/carers) to reach an informed decision. Treatment choices to manage carious lesions for children are not only based on which is the most comfortable, but also consider effectiveness and acceptability, for both children and their parents.

In Brazil, ART is the treatment of choice for children outside the clinical setting as no clinical facilities or complex devices are required. It is also commonly used in the public health service, because of its low resource costs, both for material and clinician time. Although this trial was conducted in Brazil, its results can be extrapolated worldwide given that the HT has shown similarly high success rates in clinical and non-clinical settings, where the conventional clinical facilities are not available.

Similar to ART, the HT is a non-aerosol generating procedure (non-AGP), so is particularly suitable as a treatment option during outbreaks of highly infectious diseases, such as COVID-19, when dental health care workers are potentially at high risk of infection from infected aerosolisation and droplet spread of contaminated body fluids.

Discomfort scores were lower for ART treated teeth, although were within acceptable clinical limits for both groups. There was high acceptability from parents and children for both treatments. However, a higher proportion of parents were bothered by the appearance of the HT crowns compared to the ART fillings. Both treatments are applicable where dental facilities are not available, being minimally invasive approaches, and non-AGPs, reducing cross-infection risk of dental treatment from aerosols and droplets. However, the HT restoration survival rate was almost three times higher than ART (93.4% compared to 32.7%) for restoring occluso-proximal dentine lesions in primary molars after 3 years.