One-year evaluation of a new restorative glass ionomer cement for the restoration of non-carious cervical lesions in patients with systemic diseases: a randomized, clinical trial

Abstract Objective This randomized and clinical trial aimed to evaluate the performance of a new restorative Glass Ionomer Cement (GIC) for the restoration of non-carious cervical lesions (NCCLs) of patients with systemic diseases compared with a posterior resin composite after 12 months. Methodology 134 restorations were placed at 30 patients presenting systemic diseases by a single clinician. NCCLs were allocated to two groups according to restorative system used: a conventional restorative GIC [Fuji Bulk (GC, Tokyo Japan) (FB)] and a posterior resin composite [G-ænial Posterior (GC, Tokyo Japan) (GP)] used with a universal adhesive using etch&rinse mode. All restorative procedures were conducted according to manufacturer’s instructions. Restorations were scored regarding retention, marginal discoloration, marginal adaptation, secondary caries, surface texture, and post-operative sensitivity using modified United States Public Health Service (USPHS) criteria after 1 week (baseline), 6, and 12 months. Descriptive statistics were performed using chi-square tests. Cochran Q and Mc Nemar’s tests were used to detect differences over time. Results After 12 months, recall rate was 93% and the rates of cumulative retention failure for FB and GP were 4.9% and 1.6% respectively. Both groups presented similar alpha rates for marginal adaptation (FB 86.2%, GP 95.5%) and marginal discoloration (FB 93.8%, GP 97%) at 6-month recall, but FB restorations showed higher bravo scores than GP restorations for marginal adaptation and marginal discoloration after 12 months (p<0.05). Regarding surface texture, 2 FB restorations (3.1%) were scored as bravo after 6 months. All restorations were scored as alpha for secondary caries and postoperative sensitivity after 12 months. Conclusion Although the posterior resin composite demonstrated clinically higher alpha scores than the conventional GIC for marginal adaptation and discoloration, both materials successfully restored NCCLs at patients with systematic disease after a year. Clinical relevance Due to its acceptable clinical results, the tested conventional restorative GIC can be used for the restoration of NCCLs of patients with systemic diseases.


Introduction
Non-carious cervical lesions (NCCLs) develop in exposed root surfaces due to several factors, including abrasion, friction, and stress forces, 1 and they are presented in different clinical forms, such as shallow grooves, large wedge-shaped defects with sharp line angles, and disc-shaped lesions. They are mostly observed on incisors, canines, and premolars, and they have been shown to affect the maxillary teeth more than the mandibular teeth. 2 Abrasion of the root is associated with esthetic problems, hypersensitivity, and bacterial plaque accumulation, which are considered the main reasons for treatment and restoration. 3 Multiple factors are involved in the occurrence of NCCLs, and the lesions depth and width can vary. 4 Although their etiology differs among cases, the prevalence of NCCLs is increasing with the aging of the population, and thus the risk of developing systemic disease is also increasing. [5][6][7] Either glass ionomer cement (GIC) or resin composite in combination with resin-based adhesive are preferred to restore NCCLs. The choice is usually based on the clinician's preference and ease of handling the material without considering the durability of restorations supported by strong clinical evidence.
A number of clinical trials have assessed the performance of GICs for restoring NCCLs, and these trials have demonstrated acceptable clinical results. [8][9][10][11] Fluoride release from GICs may provide effective tooth surface protection against demineralization, also supporting teeth integrity. 12 The weaker physical properties of GICs are considered as disadvantages compared to resin composites, along with their poor esthetic properties (e.g., limited range of shades). 1,12 GICs bond to teeth by micromechanical and chemical bonding, and therefore they are considered selfadhesive materials. 13 Recently, a new conventional GIC system (Fuji Bulk; GC, Tokyo Japan) was introduced. 14 This new GIC offers a faster setting time, so that it can be used for older patients and patients who are unable to stay in the dental chair for a long time. 14 The manufacturer claims that a purpose-designed glass filler and a new higher-molecular-weight polyacrylic acid enable this GIC to have increased resistance. 14 Hence, this material may be a better choice for use in geriatric patients and individuals with dry mouth or active caries, and also for patients with systemic diseases who have to struggle with more challenging oral conditions than healthy individuals.
Increases in life expectancy have been followed by changes in the morbidities rates that mostly affect older individuals. Chronic and systemic diseases, such as heart disease, 15 cancer, 16

Sample size calculation
The sample size was calculated using G*Power One-year evaluation of a new restorative glass ionomer cement for the restoration of non-carious cervical lesions in patients with systemic diseases: a randomized, clinical trial J Appl Oral Sci. 2020;28:e20200311 3/10 software (version 3.1) with 95% confidence interval, 90% power, and 0.40 effect size in the chi-square test.
The highest degree of freedom was assumed to be 5 and the minimum restoration number was determined to be 51 per group. Considering the possibility of dropouts during the study period, the sample size was increased to 67 in each group and a total of 134 restorations were performed.

Patient screening
A clinician recruited participants who met the inclusion criteria ( Figure 1) among patients seeking routine dental care from the Restorative Dentistry Department. Non-retentive lesions with a cavosurface margin involving at most 50% of the enamel were included. Assessments were carried out using an explorer, a mouth mirror, and a periodontal probe. The cold test was also performed for sensitivity to avoid the inclusion of patients with severe hypersensitivity.
Patients were asked to grade their pain on a scale ranging between 0 and 10 and some patients were excluded if the pain rating was 7 or higher.
Patients older than 50 years who had at least one systemic disease (Table 1) were included in the study.
All patients had at least 20 teeth 20,21 in occlusion and at least 2 teeth with NCCLs that had to be restored.
Teeth had to be vital without mobility. Patients with severe caries or heavy bruxism were excluded. A total of 72 patients were screened for the study and 30 participants were selected. A total of 134 NCCLs were restored in 30 (17 female, 13 male) patients with a mean age of 61.8 years. The study design is presented in Figure 1.

Randomization
Randomization was carried out by another clinician who was not involved in the research protocol. The teeth were randomized for each of the two restorative treatments by a random number table generated by the program "Research Randomized Program" (http:// www.randomizer.org/form.htm). Similar numbers of restorations were placed in both groups, and each patient received at least two restorations. In some cases, more lesions were restored following the same randomization protocol.

Restorative treatments
The materials used in the study are listed in Figure   2. Patients with lesions 1~3 mm deep, were included in the study. Before starting the restorative procedures, the distribution of demographic characteristics of Heart disease -coronery artery disease 4
Patients received dental prophylaxis and oral hygiene instructions one week before treatments.
The gingival index (GI) and plaque index (PI) of each tooth were determined before treatment. 22 In total, 13 (9.7%) teeth were scored as 0 (no bleeding), 69 teeth (51.5%) were scored as one (some bleeding after probing), 45 (33.6%) teeth were scored as two (bleeding immediately after probing), and seven (5.2%) teeth were scored as three (bleeding on probing spreading toward the marginal gingiva). The overall PI for patients was 0.96 (SD: 0.32, n=134).
Patients' salivary flow rate and saliva pH were checked before starting treatments. Mean unstimulated and stimulated salivary flow rates were 0.19±0.75 and 0.82±1.23 mL/min, respectively, both flows were low. Six patients had salivary pH 6.8-7.8 (healthy saliva) and 24 patients had moderately acidic saliva (pH 6.0-6.6).

Fuji Bulk / GC Corporation, Tokyo, Japan Powder
Floro-amino-silicate-glass 92-97wt% Polyacrylic acid 3-8wt% Pigment Liquid Polyacrylic acid Distilled water Polybasic carboxylic acid Shake the capsule or tap its side on a hard surface to loosen the powder. To activate the capsule, push the plunger until it is fully depressed with the main body and hold it down for 2 sec) Ensure the plunger is fully pressed to avoid the incorrect mixing ratio of powder and liquid. Immediately set it into a mixer (or an amalgamator) and mix for 10 sec (+/-4,000 RPM). Immediately remove the mixed capsule from the mixer and load it into the GC CAPSULE APPLIER. Make two clicks to prime the capsule then syringe. The working time is 1 minute 15 sec from start of mixing at 23°C. Within 10 sec maximum after mixing, start to extrude the mixture directly into the preparation.    The lesions were cleaned with a slurry of pumice and water on slow-rotating rubber cup in a slow-speed hand piece, rinsed, and dried. One operator performed all restorations; despite having more than 8 years of experience, the operator performed 10 restorations with each test material in patients not included in the study before starting the trial. Each restoration was scored as alpha by the two previously calibrated operator. At this point, the operator was considered calibrated to perform restorative procedures during the study. 23 Restorative procedures were carried out after isolating the lesions using cotton rolls. Restorative

Results
Clinical evaluation scores of restorations are shown in Table 4. Most restored teeth were premolars (73%). After randomization, 53% were placed at the mandibular arch and 47% were placed at the maxillary arch. At baseline, all restorations scored alpha regarding the modified USPHS criteria evaluated (retention, marginal adaptation, marginal discoloration, surface texture, secondary caries, and postoperative sensitivity).

At 6-month examinations, only two FB restorations
showed bravo scores for surface texture. At 12-month assessments, a total of 10 (7 FB, 3 GP) restorations were scored as bravo, and the difference between the two groups was not statistically significant (p>0.05).    The literature presents few reports of restorative treatment in patients with systemic diseases. [42][43][44] In patients with high caries risk, the placement of a viscous GIC is able to prevent the occurrence of secondary caries. 42  Authors' contributions