With the increase in life expectancy, people are retaining more of their natural dentition for longer. As people age, medical conditions and other physical, intellectual and cognitive disabilities can negatively-impact their oral health and affect their overall wellbeing, which places an additional burden on the oral healthcare system.
Dental caries is a global disease affecting all ages and sectors of the population [1
]. It is a multifactorial disease that occurs as a result of interactions between the host, the environment, and microorganisms. Dental caries can be either an active or an arrested disease process. Active caries usually requires a susceptible host with suitable environmental factors created by high intake of dietary carbohydrates coupled with poor oral hygiene [1
]. Root caries is any carious lesion which occurs on the root surface of the tooth and is caused by the acid produced by bacteria [5
]. Older people are at higher risk of developing root caries due to gingival recession exposing the root surface, reduced salivary flow, inadequate oral hygiene, and dietary factors [5
]. Reduced salivary flow is often a result of polypharmacy, which is common in older people [6
]. Saliva plays a key role in oral lubrication and acid neutralisation [7
]. Moreover, older people are more likely to have impaired dexterity and mobility; live in rest homes with medical conditions so that they are more dependent on care; and have poor oral hygiene practices compared with the general population [8
]. Such a cohort would benefit from a quick and simple method of delivering cost effective root caries treatment that is less stressful than conventional treatment. If appropriate preventative measures are not implemented properly, the risk of developing root caries remains higher for older people. Preventive measures such as fluoride application can reduce the incidence of root caries [10
]. Minimal intervention dentistry has gained popularity in recent years, as exemplified by the effective Hall technique and atraumatic restorative treatment (ART) approaches [11
]. ART can be applied in both the deciduous and permanent dentitions, and has significant advantages compared to conventional restorative techniques. These include being pain-free, not requiring anaesthesia, involving minimal cavity preparation, being cost-effective, and having high restoration survival rates [13
The development of wear-resistant glass ionomer cements (GICs) in the mid-1990s replaced medium viscosity glass ionomers, and presently, wear-resistant glass ionomer cements are the material of choice when using ART [16
]. Although the development of ART was intended mainly for underprivileged children in developing countries [16
], it has gained popularity in the treatment of older people, specifically for root caries.
The antimicrobial properties of restorative materials are important for the long-term success of restorations. These benefits include the prevention of caries recurrence around the margins of restorations, the inhibition of plaque accumulation near restorations, and reduction in the number of cariogenic microorganisms in the salivary fluids and oral cavity [17
]. Several studies have evaluated the effect of incorporating antimicrobial agents such as chlorhexidine (CHX) into GIC [17
]. CHX has been shown to have great substantivity with human dentine. Furthermore, both the gel and solution forms of CHX have been shown to have up to 90 days of retention in dentine [21
]. This study aimed to evaluate the restoration integrity, survival rate, patient acceptability, and antimicrobial performance of chlorhexidine-modified GIC (GIC-CHX) in the treatment of root caries.
This study assessed the clinical effectiveness, restoration integrity, survival, patient acceptability, and microbial colonisation of a modified glass ionomer cement restoration placed using ART to treat root caries. The survival rate of the modified GIC-CHX restorations was higher than for conventional GIC restorations over the 6-month period.
Most participants in this study found the procedure to be quick, comfortable, and minimally painful or uncomfortable. This is in agreement with several previous studies that have reported that patients experienced less pain during the placement of an ART restoration than with conventional restorative techniques [24
]. Furthermore, the ART approach has other benefits, such as requiring only hand instruments to treat root caries, and the procedure can be carried out at rest homes where the elderly do not have to travel. Therefore, it provides a simple and cost-effective treatment modality which is a benefit to patients.
The cost-effectiveness of ART versus conventional restorative methods was assessed in a randomised clinical trial involving 82 adult patients in Ireland [15
]. The study found that ART was more cost-effective than placing conventional restorations, with cost effectiveness ratios of 0.18 and 0.29, respectively. In addition, when a dental hygienist provided ART, the cost-effective ratio reduced to 0.14 [15
], although this is not possible in some parts of the world because of the specific scope of practice for oral health therapists [26
In this study, only 8% of the participants were anxious during the restorative procedure, and at the 6-month appointment, none of the participants were anxious. This high level of patient acceptability could be due to the participants being made aware that this simple procedure involved only hand instruments with no drilling or local anaesthesia. Despite two participants being anxious at the first visit, both reported not being anxious at subsequent visits, most likely because of favourable experiences during their first visits. This makes ART, where appropriate, a suitable treatment modality for dentally anxious patients, especially when a proper explanation of the procedure is delivered to the patient before treatment. A study conducted in South Africa [28
] tested the hypothesis that ART would result in less dental anxiety compared to conventional restorations in outpatients attending public oral health clinics. The study found that ART caused less dental anxiety in both adults and children [28
]. Participant satisfaction with the ART was also investigated, and all participants were satisfied with ART at baseline and at all subsequent appointments. A previous study conducted in Zimbabwe showed that 95% of secondary school students who had never previously received dental restorations were satisfied with the ART procedure and restorations [29
]. Small and medium size cavities were found to be very easy to restore with ART by the operator; however, large cavities required extensive excavation, which may cause operating hand fatigue, so that the procedure takes longer than the conventional method which uses rotary instruments.
There was no change in taste perceived by participants with the GIC-CHX restorations. This indicates that the small amount of chlorhexidine in one GIC-CHX restoration may not have a significant effect on taste, even though chlorhexidine is known to impair taste when used as a mouthwash [30
]. The setting times of the GIC-CHX restorations were similar to or quicker than those for control GIC restorations. This indicates that modification with chlorhexidine did not affect the setting time of GIC. A previous study found that altering the powder-to-liquid ratio affects the setting time, and a high powder-to-liquid ratio has been found to shorten the setting time of GIC [31
In the present study, the clinical performance of GIC-CHX restorations was compared to that of control GIC restorations at baseline and 6 months using the modified Ryge criteria [23
]. In addition to the operator who placed the restoration, another independent operator assessed the clinical performance of the restorations at six months to reduce operator-based bias. At the 6-month examination, marginal adaptation was assessed. Of the 25 restorations, 23 GIC-CHX restorations were either continuous or slightly catchy with no obvious crevice at the margin, whereas 10 control GIC restorations had obvious crevices at the margin. An obvious crevice at the margin is considered a failure according to the modified Ryge criteria [23
]. Furthermore, no secondary caries lesions were evident in the test GIC-CHX restorations after 6 months (Table 6
). A possible reason for this difference could be that GIC-CHX restorations eliminated the bacteria remaining in the cavity, preventing the development of secondary caries. A study by Lo et al. (2006) revealed that secondary caries was one of the main reasons for the failure of ART restorations when conventional GIC was used [25
]. Secondary caries usually develops from the residual caries left in the prepared cavity, since the ART may not completely remove all the carious tissue [25
]. Although fluoride-containing restorations such as GIC are known to have a cariostatic effect, it is not known whether the level of fluoride release is sufficient for inhibiting demineralisation [32
]. However, incorporating an antibacterial agent in GIC may eliminate the remaining bacteria in the cavity, preventing secondary caries. De Castilho et al. (2013) showed that incorporation of chlorhexidine in resin-modified GIC eliminated all bacteria in the cavity when tested by re-entry into the cavity after 3 months [33
Surface roughness was also assessed for both types of restorations. At 6 months, 60% of GIC-CHX restorations were smooth, whereas 84% of control GIC restorations were slightly rough or rough. This could have been due to faster wear of modified GIC-CHX in comparison to GIC. Marti et al. (2014) showed that the hardness of GIC decreased when chlorhexidine was added, which resulted in accelerated wear of the material [34
In this study, the microbial counts in plaque samples from GIC-CHX restorations were not significantly lower than those around GIC restorations at all time points investigated. Previous studies have shown that incorporation of chlorhexidine in restorative materials increased the antibacterial effect of the material for up to 90 days [20
]; however, these were in vitro studies, which did not replicate the oral environment, where saliva is produced and secreted continuously [37
]. Given the fact that only a small amount of CHX was added to GIC, the high clearance rate of saliva could have reduced its effect significantly over time. In addition, fluid intake might have diluted the effect of chlorhexidine on the surface of the GIC and reduced its antimicrobial effect [38
The slight reduction in cariogenic bacteria after 1 month could have been due the improvement of participants’ oral hygiene habits, following the instructions given at the time of the initial consultation. This may have reduced the plaque accumulation and number of cariogenic bacteria. Another possible reason for the reduction in cariogenic bacteria could be related to the elimination of carious dentine during the ART procedure, resulting in a change in the environment that was harbouring these bacteria prior to treatment. Furthermore, the potential antibacterial effect of fluoride release from GIC restorations should not be ignored [39
], although some studies have suggested that the concentration of fluoride released is not high enough to result in significant antibacterial effects in GIC restorations [19
]. Overall, it appears that the concentration of chlorhexidine incorporated in GIC was insufficient to reduce the numbers of the tested microorganisms.
This study has some limitations, including the limited number of restorations placed and the short period of follow-up. The recruitment of participants with two root caries lesions in a limited demographic region proved more difficult than originally anticipated. Other limitations, such as patients’ oral hygiene routine, general health conditions compromising the oral environment, and the size and location of placement of the restorations were accounted for as much as possible, but could have influenced the results to a certain extent. Despite this, the findings reported here are encouraging, and further clinical research is needed with a larger number of participants and a longer monitoring period. The optimum concentration of CHX that can be added to the GIC (without compromising restoration integrity) should also be investigated further.