From November 2018 until August 2021, an oral health promotion project for schoolchildren in Kerung, a remote village in Nepal, was performed. This project included an epidemiologic part, an educational part, and a treatment part. After the first visit (T0), it was suggested that the availability of biocompatible and bioactive materials to treat deep caries lesions could be most valuable [1].
Tricalcium silicate (Ca3SiO5) based cement is bioactive and biocompatible, inducing hard tissue formation [2] Mineral trioxide aggregate (MTA) is a first-generation tricalcium silicate cement. MTA is since 30 years a prominent product mainly used for endodontic purposes [3]. More recently, this material has been proposed as a restorative base material in patients with deep caries after selective caries removal as well as to obtain pulp regeneration [4-8]. The use of MTA in vital pulp therapy induces mineralisation and causes a perfect seal which inhibits bacterial infiltration. Due to the mineralisation capacity of the cement, it is possible to avoid pulp exposure in deep carious lesions [9-12].
Since 2010, laboratory-synthesised tricalcium silicate cement (Ca3SiO5) was launched by Septodont (St Maur des Fosses, Paris, France) as BiodentineTM (further written as Biodentine). The physical properties such as flexural strength (34 MPa), elastic modulus (22,000 MPa), compressive strength (300MPa) and push-out bond strength of Biodentine are higher than those of MTA and similar to human dentin [13]. Owing to similar mechanical properties as dentin, Biodentine can be used as a dentine substitute and a temporary filling for at least six months, as shown by Koubi et al. (2013). In the latter study, Biodentine was compared to a resin-based composite when used as a posterior restoration. Using USPHS criteria, the anatomical form, marginal adaptation and interproximal contact for both materials were rated as very satisfying at the moment of restoration. Biodentine received acceptable scores for the aforementioned characteristics six months after the restoration. After this period, the composite group showed better marginal adaptation, anatomic form, and proximal contact than the Biodentine restored group [4].
It has been shown that hydroxyapatite crystals can be formed within the dentinal tubules upon contact with human dentin and in contact with pulp tissue, a dentine bridge formation can be seen. The bridge formation is caused by the breakdown of the tricalcium silicate cement whereby the cement’s byproducts (Si, OH⁻ and Ca2+) are released. Moreover, when this cement is placed on human pulp cells, TGF-β1 is released. TGF-β1and Ca2+ stimulate pulp stem cell recruitment and differentiation into odontoblastic cells, thereby contributing to the formation of a dentine bridge [6,14].
Besides the optimum physical properties, Biodentine has an antibacterial effect when placed on the remaining carious dentin. This effect is mainly because the cavity is separated from cariogenic nutrients by a good adhesive restoration [15]. However, the release of OH- ions from calcium hydroxide also inhibits micro-organisms through an alkaline pH of up to 12.5 [12,16].
According to the study by Tziafa et al. (2019), a layer of tertiary dentin (mineralised matrix under the cavity floor) develops after the placement of Biodentine, in the presence or absence of a Dycal protective base (a calcium hydroxide rigid-setting material), in deep dental caries. There was significantly more development of the tertiary dentin after eight weeks when the cavity was restored with Biodentine in the absence of Dycal (142 µm ± 21 without Dycal vs 76 µm ± 14 with Dycal base). From this study [17], it can be assumed that, with the application of Biodentine in direct contact with the cavity floor, there is more stimulation of the formation of tertiary dentin compared to the application of a Dycal base. The latter supports earlier findings that this material can cause dentine bridge formation without inflammation of the pulp due to its byproducts and the secretion of TGF-β1 [18-21].
In the study by Li et al. (2017), Biodentine induced dense remineralisation of artificially demineralised dentin as early as one week after placement [22]. However, remineralisation remains incomplete in the deepest remaining demineralised dentin zone, even after six months. Therefore, to achieve better remineralisation in this zone, the release of Ca2+ ions from the cement should be prolonged and slowed down.
Furthermore, Biodentine can also achieve biomimetic remineralisation of the affected dentin. This bioactive material releases growth factors, such as TGF-β1, from dentin via collagen degradation. These growth factors can induce remineralisation. The high alkalinity also plays a role in the remineralisation effects of Biodentine. High alkalinity enables the formation of hydroxyapatite crystals at the interface between the cement and dentin walls. These crystals may contribute to the sealing efficiency of the material [23,24].
There is a considerable amount of literature on the performance of Biodentine as a dentine substitute for several indications [13]. However no literature on the performance as a temporary filling material has appeared since the study of Koubi et al., (2013). In this respect there is an urgent need for more clinical and long-term studies.
Aim of the study
The study aimed to perform Biodentine temporary fillings in deep carious lesions without pulp involvement after selective caries removal in asymptomatic patients in the remote village district of Kerung, Nepal during the second (T1) and third visit (T2) and to evaluate these treatments after 12, 24 and 36 months. Regarding the survival rate, the null hypothesis (H0) was that all Biodentine fillings would survive after one year. Furthermore, concerning a possible difference in single and multi-surface fillings, the null hypothesis (H0) was that there would be no difference in the survival rate.