Randomized clinical trial of encapsulated and hand-mixed glass-ionomer ART restorations: one-year follow-up

Abstract Objective This prospective, randomized, split-mouth clinical trial evaluated the clinical performance of conventional glass ionomer cement (GIC; Riva Self-Cure, SDI), supplied in capsules or in powder/liquid kits and placed in Class I cavities in permanent molars by the Atraumatic Restorative Treatment (ART) approach. Material and Methods A total of 80 restorations were randomly placed in 40 patients aged 11-15 years. Each patient received one restoration with each type of GIC. The restorations were evaluated after periods of 15 days (baseline), 6 months, and 1 year, according to ART criteria. Wilcoxon matched pairs, multivariate logistic regression, and Gehan-Wilcoxon tests were used for statistical analysis. Results Patients were evaluated after 15 days (n=40), 6 months (n=34), and 1 year (n=29). Encapsulated GICs showed significantly superior clinical performance compared with hand-mixed GICs at baseline (p=0.017), 6 months (p=0.001), and 1 year (p=0.026). For hand-mixed GIC, a statistically significant difference was only observed over the period of baseline to 1 year (p=0.001). Encapsulated GIC presented statistically significant differences for the following periods: 6 months to 1 year (p=0.028) and baseline to 1 year (p=0.002). Encapsulated GIC presented superior cumulative survival rate than hand-mixed GIC over one year. Importantly, both GICs exhibited decreased survival over time. Conclusions Encapsulated GIC promoted better ART performance, with an annual failure rate of 24%; in contrast, hand-mixed GIC demonstrated a failure rate of 42%.


Introduction
The Atraumatic Restorative Treatment (ART) approach is based on the removal of infected tooth tissues with hand instruments, followed by restoration of the cavity and sealing of adjacent pits and fissures 2 . This approach, which is an economical and effective method to prevent and control carious lesion development, causes less discomfort and dental anxiety to patients than the conventional rotatory instruments 2 .
Glass ionomer cements (GICs) have become the most used material for the ART approach due to their biological, physical, and chemical properties 17 .
Notably, hand mixing of GICs might allow for an increased incidence of operator errors during material preparation, as the ratio of powder to liquid may vary according to manufacturer's recommendations 4  With the purpose of decreasing these variables, encapsulated dental cements have been introduced in the market 21 . These premade mixtures utilize mechanical mixing methods and allow standardization of the powder/liquid ratio in a sealed capsule, which is expected to reduce variation in clinical outcomes 21,22 .
A meta-analysis of ART showed that high-viscosity GICs presented higher clinical survival rates than conventional or medium-viscosity glass ionomers 28 .
This classification was only based on the powder/ liquid ratio. However, a characterization of high viscosity GICs also considered improvement in the liquid components as well as changes in the powder 13 .
Some products are classified as medium-viscosity glass ionomers but are indicated by the manufacturers for ART techniques, and are available for hand mix or in capsules. Laboratory studies have shown that encapsulated GICs produce specimens with less porosity and higher mechanical strength than hand mix specimens 19,21,22 . However, there is no literature describing the survival rates of encapsulated versus hand-mixed GICs.
The purpose of this study was to evaluate the clinical performance of one conventional GIC (Riva Self-Cure, SDI Limited, Bayswater, VIC, Australia) supplied as both hand-mixed kits and in an encapsulated form.
The null hypotheses to be tested were: 1) there is no difference in the survival rates of Class I restorations performed with hand-mixed or encapsulated GICs; and 2) there is no difference in the survival rates of GICs evaluated at different time periods.

Material and methods
We performed a randomized and split-mouth clinical trial. Experimental design followed the Consolidated Standards of Reporting Trials (CONSORT) guidelines; the experimental flow chart is shown in We obtained informed consent forms from the legal guardians of all children recruited to the study.
Then, we reviewed each child's record for demographic information, as well as their medical and dental history.
Parents were asked to provide information about their socio-economic status, according to criteria from the Brazilian Association of Market Survey Institutes 3 .
Visible plaque index (VPI), gingival bleeding index (GBI), and decayed, missing and filled teeth The selected tooth was isolated with cotton rolls.
Then, the chair assistant used a lottery method to randomly allocate the material (encapsulated or hand-mixed) used for each patient's first procedure.
Initially, the tooth surface was cleaned with a wet cotton pellet. The ART approach was used to remove infected dentine with an excavator. Thin, unsupported enamel was carefully removed using a hatchet placed  Sample size (n) was calculated, using a proportional comparison formula for two-tailed test. Significance sequence (Zα) and statistical power (Zβ) were adopted in 5% and 80%, respectively. The noneffectiveness ratio of encapsulated and hand-mixed GIC is respectively 5.3% 29 and 28.3% 30 . To offset any losses during the study, 15% were added to the amount found. Therefore, the initial sample size was

Results
The socio-economic status assessment indicated that 77.5% of the participants were classified as class C; 20% as class D; and 2.5% as class E. No perception of patient pain or discomfort was observed in 52.5% of teeth; minor pain was observed in 33.8% of teeth; and severe pain was observed in 13.7% of teeth.  Statistically significant reduction in the VPI index between baseline and one year was observed (p=0.007). We did not find any statistically significant differences in the GBI index (p≥0.05). We found statistically significant differences in the DMFT index between baseline and 6 months (p=0.017), and between baseline and 1 year (p=0.010).
The distribution of lesions and clinical procedure characteristics between encapsulated and handmixed GICs is shown in Table 2. We did not find any statistically significant differences on the distribution of teeth, lesions, cavities, and restorations characteristics between the evaluated groups. Maxillary second molar 7.5 5   year (p=0.026). For hand-mixed GICs, we observed statistically significant differences only between the period of baseline to 1 year (p=0.001). There was a statistically significant difference between the clinical performance for the following periods: 6 months to 1
Logistic regression analysis showed that no variables studied had statistical influence on the clinical performance of GICs (Table 4). There were   The manipulation of GICs in lower powder-to-liquid ratios than those recommended by the manufacturer has been reported to significantly reduce mean compressive fracture strength 10  In a study in which physical properties of handmixed Riva Self Cure were studied, the 1-week compressive strength was maintained through 1 year. However, the 1-week surface hardness was only maintained through 6 months 25 . A progressive wear was also observed for hand-mixed Riva Self Cure through 1 year in a laboratory study 5

Conclusion
Based on our present results, encapsulated GICs appear to promote better ART performance, contrasting an annual failure rate of 24% with 42% for hand-mixed GICs. Encapsulated GICs may be a more promising option for the ART approach than their hand-mixed equivalents.