An In Vitro Comparative Evaluation of Fracture Strength of Composite Resin and Activa Kids Bioactive Restorative for Use in Strip Crowns

Introduction

A healthy smile can truly transform a child’s visual appearance, positivity of the mind-set, can improve not only the oral health but also the general health. Early childhood caries (ECC) can be considered as the most prevalent dental problem in the infancy and childhood period.1 Restoring and maintaining primary teeth till they exfoliate from the oral cavity is important because it maintains the space for the succedaneous teeth, helps in prevention of tooth migration, bone loss, arch collapse, aids in mastication, speech, as well as aesthetic appearance.²

According to AAPD, the central and lateral incisors are the initial teeth to erupt and the first to be subjected to bacterial assault resulting in caries. Their average period of eruption is between 5 to 10 months of age. Data shows that in young American children, caries in maxillary anterior primary teeth can account for 50% of the overall caries prevalence of the general population.³

As the caries progresses, more definitive treatment is required. Early stages of ECC can be managed with restorative therapy. As the stage advances, definitive treatment such as full coverage restorations with strip crowns becomes necessary.⁴ Composite restorative material is the traditional choice of material for use in strip crowns. According to AAPD guidelines, children with large multi surface caries without pulp therapy, poor oral hygiene and teeth which cannot be isolated are not ideal for composite restorations.⁵ Resin-based dental sealants and composites contain Bisphenol-A (BPA) and its derivatives as its components. Studies have shown that accumulation of certain BPA derivatives may pose health risks which can be attributed to their estrogenic properties. Research findings showed trace amounts of BPA derivatives up to three hours after resin placement which can be detectable in saliva through salivary enzymatic hydrolysis process.⁶

ACTIVA KIDS BioACTIVE-RESTORATIVE is considered as the first bioactive composite with a pedo shade, that delivers all the advantages of glass ionomers cement in a strong, resin matrix as resilient as composites, without any Bis Phenol derivatives.

Therefore, the purpose of the current study was to compare the fracture strength of composite resin and ACTIVA KIDS BioActive Restorative (Pulpdent, USA) when used as a core material in strip crowns for restoring primary teeth.

Materials and Methods

Based on the parameters from the previous research, the sample size was 10 in each group.⁷

Ethical committee clearance for approval of the study protocol was obtained from the Institutional Review Board (2021/10/1) of the Srinivas Institute of Dental Sciences, Mangalore. Figure 1 shows the armamentarium used in the study. In the presented in vitro study, twenty exfoliated human maxillary primary central incisors as well as lateral incisors were collected (Figure 2) and stored in 10 percent formalin till the use. Teeth with dental caries or any fracture were not included in the study. An ultrasonic scaler was used to clean the gross debris (Magbole, Guangzhou, China). The teeth were then embedded in a block of dental plaster made using a rigid rubber template (Figure 3). The teeth were separately numbered and the buccolingual aspect, mesiodistal aspect, and cervicoincisal aspect dimensions were independently measured by two investigators using Vernier caliper (Mitutoyo, Japan), and the mean was taken to establish baseline dimensions to guide the tooth preparation. Vernier caliper was kept on the greatest curvature at the cingulum of the incisor region and measured for the dimension of buccolingual aspect. The greatest dimension at the middle third of the crown was considered as the mesiodistal aspect dimension. The cervicoincisal aspect dimension was measured at the buccal surface from the most apical point of the cervical line to the incisal edge. The crowns of the teeth were prepared to receive a full coverage restoration with a strip crown. A 169L carbide bur (SS White) was used in a high-speed hand piece with water coolant while maintaining the parallelism of the proximal surfaces.

Teeth samples were prepared with a width of 3.5 mm at buccolingual aspect, width of 4 mm at mesiodistal aspect, and length of 4 mm at cervicoincisal aspect (Figure 4). All the mentioned measurements were made using a Vernier caliper by two independent investigators and the values were recorded (Figure 5 and 6). The strip crown (size UL1 914001) for primary maxillary left central incisor (3M ESPE, St. Paul, USA) was checked with the tooth and used for both the groups (Figure 7). According to the manufacturer’s instructions, the strip crowns were trimmed using sharp-curved scissors, and vent holes were created using a sharp explorer on the proximal surface to remove the air and excess material (Figure 8). The teeth in both the groups were dried and etched (Ivoclar Vivadent- Eco Etch) for 15 seconds. The etchant was rinsed off, and the dentin surface was dried with gentle air spray, taking care not to over dry the tooth. The bonding agent (Ivoclar Vivadent- TeEconom Bond) was applied and light-cured (Bluedent LED, Smart, Bulgaria) for 20 seconds at 1,200 mW/cm² .

The samples were randomly divided into two groups: Group I - Composite resin (Te-Encom Plus, Ivoclar vivadent) and Group II - ACTIVA Kids BioActive Restorative (Pulpdent USA). These materials were used to fill the inside of strip crown in each group, respectively (Figure 9). The strip crown was placed on the tooth with slight finger pressure, and the excess material was removed using a sharp explorer. The samples were lightcured through the strip crown for 40 seconds labially and 40 seconds lingually with 1,200 mW/cm2 curing unit (Blue dent LED Smart) as per the manufacturer’s instructions (Figure 10). A sharp spoon excavator (GDC Marketing, India) was used to cut the strip crown from the lingual aspect and the crowns were stripped off. The teeth were stored in isotonic saline for 24 hours prior to testing for fracture strength. The samples were tested for fracture strength using a Universal testing machine (Zwuick/Roell Z020 20KN) (Figure 11). The force was applied at the incisal edges of the crown with a crosshead speed of 1 mm/minute, and the force of fracture was recorded in Newton (N) and deformation at break was recorded in percentage.

Statistical analysis was done using SPSS 16.0 software. Mean and standard deviations were calculated. Student “t” test was used to compare the results between the groups. p value <0.05 was considered as statistically significant.

Results

It was found that the minimum to maximum force required to fracture strip crowns restored with ACTIVA Kids BioActive Restorative (235.08–682.71 N) was higher when compared to composite resins (167.57– 449.29N) (Table 1, Figure 12 and 13). 

Sample number and its colour code

However, based on student “t” test, no significant difference in the fracture strength between the two study groups (p=.062) was found. Deformation at break percentage has shown significant difference between both the groups (p=.004) which was higher for Group I (1.34%) when compared with Group II (0.68%) (Table 2).

Discussion

Early childhood caries (ECC), formerly referred to as ‘nursing bottle caries’ and ‘baby bottle tooth decay’, remains a significant chronic disease of childhood and a public health concern.⁴ Foremost objective of placing strip crown is to improve the aesthetics of the child. A remarkable change can be seen in the self-image of the child after correction with proper shade, texture and shape which helps to maintain good physiological form and function of the teeth.² Indications for full coronal restoration are: Multi surface caries lesions with involvement of incisal edges, extensive cervical decalcification, post endodontic therapy, high-risk patients with poor oral hygiene or the child’s disruptive behavior making placement of Class III restorations difficult.⁸

Kupietzky A et al.,⁹ reported the clinical success rate of strip crown was 88% by overall retention rate and he further stated advantages of strip crowns as, simple to trim and fit, easy and fast removal, matches easily with natural dentition, provides a smooth shiny surface, easy shade selection with multiple shades of composites available, superior in function, esthetic in appearance, economical, thin, transparent and easy to repair, and the overall parental and patient satisfaction with RSCs was reported to be high. Ram D et al.,¹⁰ stated that composites are most commonly used in strip crowns and the disadvantages include technique sensitive procedure, moisture contamination when in contact with saliva and blood could alter the shade or colour of the composite material. G. Schmalz et al.,⁶ reported that Bisphenol A (BPA) is extensively used in the manufacturing of many consumer plastic products and could become part of dental sealants and composites in three ways, such as a direct ingredient, as a by-product of other ingredients or as a trace material left-over from the manufacturing of other ingredients.

After application of resin-based dental composites and sealants, exposure to BPA is immediate and is considered as the most significant window of potential toxicities.

Based on the current evidence, US Food and Drug Administration (FDA) and the American Dental Association (ADA) stated that there is no basis for health concerns related to BPA exposure from any dental material and concluded that any low-level of BPA exposure that may result from dental sealants and/or composites pose no known health threat. Recommended measures to reduce potential BPA exposure from dental materials can be followed.⁵ However ACTIVA Kids Bioactive restorative does not contain any bisphenol derivatives.

Ashraf et al.,¹¹ reported that ACTIVA Bioactive restorative has exceptional ionic shock absorbing resin matrix, infiltrated with glass ionomer filler and considered to be the first bioactive resin composite with superior antimicrobial properties. Ana Raquel Benettia et al.,¹² reported that high fracture toughness was observed compared to compomers and RMGIC and wear was observed to be similar to resin composites. Riddhi TH et al.,¹³ reported less postoperative sensitivity, superior resistance to secondary caries, and sealing of margins against microleakage. Kathiria HP et al.,¹⁴ reported ACTIVA Kids to be the most resistant to discoloration, followed by GIC and composite.

Similar study was conducted by Neeraj Gugnani et al.,¹⁵ with temporization material (Luxatemp Star) in strip crown as a chair-side custom fabrication procedure in patients. Vignesh KC et al.,⁷ conducted a similar study with Protemp 4 to check the fracture toughness in strip crown which was comparable to composite resin. In the present study, ACTIVA Kids Bioactive Restorative was compared with composite resin, and showed better physico-chemical properties than composite resin and other temporization material. In the present study, the mean fracture strength for composite resin was 301.51 N and it was 400.05 N for ACTIVA Kids Bioactive Restorative, which were comparable. Deformation at break percentage was calculated between both the groups, which was statistically significant (p=.004*)

Conclusion

The primary objective of restoring teeth is to preserve healthy tooth structure or limit further extension of caries followed by protection and preservation of remaining tooth structure with maintenance of pulp vitality. The sample size used was less to derive any definitive conclusion. Thus, direct extrapolation to clinical conditions must be exercised with caution. With the use of a bioactive restorative, all the above mentioned benefits for better restoration can be achieved. Within the limitations of the present in vitro study, it can be stated that ACTIVA Kids BioActive Restorative has a higher mean fracture strength and higher deformation at break percentage when compared to composite resin. Thus, ACTIVA Kids Bioactive Restorative can be a better material of choice compared to traditional composite resins because of its excellent chemical and physical properties.

Conflicts of Interests

Nil