Clinical performance of an alkasite-based bioactive restorative in class II cavities: a randomized clinical trial

Abstract Objective This clinical study aimed to evaluate the clinical performance of an alkasite-based bioactive material by comparing it with a resin composite (RC) in the restoration of Class II cavities over a year. Methodology A hundred Class II cavities were restored at 31 participants. Groups were as follows: Cention N (CN) (Ivoclar Vivadent, Schaan, Liechtenstein) and G-ænial Posterior (GP) (GC, Tokyo, Japan) in combination with G-Premio Bond (etch&rinse). Restorative systems were applied following manufacturers’ instructions. They were finished and polished immediately after placement and scored based on retention, marginal discoloration, marginal adaptation, sensitivity, surface texture, and color match using modified USPHS criteria after 1 week (baseline), 6 months, and 12 months. Statistical analyses were performed using chi-square, McNemar’s, and Kaplan Meier tests. Results After 12 months, the recall rate was 87%. Survival rates of CN and GP restorations were 92.5% and 97.7%, respectively. Three CN and one GP restorations lost retention. Seven CN (17.9%) and five (11.6%) GP restorations were scored as bravo for marginal adaptation and no significant difference was seen between groups (p=0.363). One (2.7%) CN and two GP (4.7%) restorations were scored as bravo for marginal discoloration, but no significant difference was observed between groups(p=1.00). For surface texture, three (8.1%) CN and three (7%) GP restorations were scored as bravo (p=1.00). None of the restorations demonstrated post-operative sensitivity or secondary caries at any examinations. Conclusion The tested restorative materials performed similar successful clinical performances after 12 months. ClinicalTrials.gov (NTC04825379).


Introduction
High plaque accumulation at the proximal surfaces of posterior teeth can lead to the development of caries and the necessity of dental treatments. 1,2 The complexity of application methods for resin composites (RC) could influence the risk of secondary caries due to bacterial microleakage. 3 Resin-based ion leaching materials such as resin-modified glass ionomer cements (RMGICs) have been used over the years to reduce recurrent caries 4 since fluoride ions are released from these materials and mechanical properties are comparable with RCs. 5 However, in modern dentistry, simplified, esthetic, and satisfactory restoration of tooth decay has led to innovative material developments. Rapidly cured restorative materials applied in large increments with selfadhesive properties became an important solution for easy and effective applications. Adhesion to tooth surface without additional procedures or conditioning has led to a single step placement that demands a short period of time. Furthermore, restorative materials with bioactive or caries-protective abilities have been introduced, such as highly viscous glassionomer cements (GICs). 6 Recently, to overcome the limitations of restorative materials, it was attempted to add caries-protective ions, especially alkaline and alkaline earth ions, such as calcium, in addition to phosphate or fluoride. 7 This newly introduced material contains alkalizing properties due to the release of hydroxyl ions. Caries lesions are caused by the imbalance of ions re-precipitated into tissues and ions that are released from the dental tissues. The calcium, fluoride, and phosphate releasing properties lead to apatite formations on tooth surface, which can explain their caries protective mechanisms. 8, 9 The monomer matrix of this new bioactive material, which consists of a mixture of urethane dimethacrylates, either aliphatic (UDMA) or aromatic-aliphatic, provides the alkasite characteristics. Moreover, studies have stated that this alkasite-based material has acid-neutralizing capabilities and prevents demineralization of enamel and dentin when subjected to lactic acid over a prolonged period. 8,9 The alkasite-based tooth-colored material Cention N (Ivoclar Vivadent, Schaan, Liechtenstein) is considered integrant of a subgroup of RCs. This self-curing restorative, with optional additional light curing, displays a high polymer network density and degree of polymerization over the complete depth of the restoration. 10 It was introduced as an amalgam replacing restorative material or as a white material that can compete to the physical properties of amalgam and bioactive properties of GICs. 11 Several studies have demonstrated that this alkasite-based material releases acceptable levels of fluoride, calcium, and phosphate. 7,12,13 A laboratory study reported that this material led to a reduction in enamel demineralization compared to a RC. 14 Additionally, other studies on calcium releasing materials have shown volumetric expansion due to water sorption, potentially compensating for polymerization shrinkage. 15,16 As a result, the use of this material may reduce the occurrence of gap formation between the tooth and the restoration.
Although several in vitro studies were performed on its mechanical properties since this material has been introduced, its clinical behavior has not yet been adequately monitored in clinical studies. Thus, the purpose of this randomized clinical trial was to assess the clinical performance of this alkasite-based restorative by comparing it with a RC in Class II cavities after 12 months. The null hypothesis was that there would be no significant difference between the clinical performance of the two restorative systems.

Methodology
The Consolidated Standards of Reporting Trials (CONSORT) statement was followed to design the study.

Ethics approval
The Ethics Committee of the institution approved the present clinical trial (KA-21046) and informed consent forms were taken from participants.

Protocol registration
The study was registered at ClinicalTrials.gov

Patient selection
Thirty-one patients with an average age of 33 years who fulfilled the inclusion and exclusion criteria were selected ( Figure 1). One of the researchers performed the assessments using a dental explorer, mouth mirror and periodontal probe.

Randomization
Each patient received at least two restorations.
Computer-generated tables were used to randomize restorative systems. A number was assigned to each restorative system in the tables for patient allocation.
Only a researcher who was not involved in the study could access the tables.

Restorative procedures
One hundred restorations were placed in Class II cavities of 31 patients (17 males, 14 females) with an average age of 33 years. One week before the restorative procedures, dental prophylaxis was performed on participants and oral hygiene instructions were provided. All restorations were performed by the same researcher, who did not participate in the selection of study individuals. Teeth were cleaned with a slurry of pumice before preparations. Diamond fissure burs at high speed were used under watercooling for preparations, whereas tungsten carbide burs with slow speed handpiece were used to remove carious tissues. If the patient felt pain or sensitivity, local anesthesia was applied. Tissue preserving cavity design was applied and the prepared cavities did not involve any cusps; additionally, the gingival walls were located supra gingivally. The cavities which did not meet these criteria were excluded. In

Results
The flow chart was shown in Figure 3. Recall rates for 6 and 12-month assessments were 96.7% and 87%, respectively. Clinical outcomes of tested groups were given in Table 1.
One (3%) CN restoration lost retention after 6 months, and two (5.1%) CN and one (2.3%) GP restorations lost retention at 12-month evaluations.  This study has some limitations that must be considered. Firstly, the short evaluation period. This study is a preliminary report and the evaluation period is not long enough. However, no clinical data on this material has been available to date. Therefore, studies examining the restoration of Class II cavities with longer follow-ups are needed. Secondly, this study included individuals with healthy periodontal tissues and, thus, studies with different participants should be performed in the future.
Lastly, in this study, cotton rolls were used for isolation to imitate clinical conditions. A meta-analysis

Conflict of interest
The authors declare no conflict of interest.

Data availability statement
The datasets generated and analyzed during the current study are available from the corresponding author on reasonable request.