The term “biosilicate” can be broken down into two components: “bioactive” and “silicatebased”.
A “bioactive” material can be defined as a material with the ability to directly interact with a biological system to elicit an appropriate biological response at the interface of the tissue and the material.3 Furthermore, “silicate-based” refers to the composition of the ceramic compound which consists of a form of calcium silicate that is capable of a roomtemperature hydraulic setting reaction. 4 Hence, for the purposes of this essay, the term “biosilicate” will be used to describe a bioactive material intended for dental use which incorporates a hydraulic calcium silicate.5

This literature review is presented in Brisbane Dentist Pure Dentistry Journal Club.

One of the most important objectives in paediatric dentistry is the preservation of functional primary teeth until natural exfoliation. 1 In addition to retaining carious or traumatised primary teeth for maintenance of arch length, apexogenesis, the continued physiologic development and formation of the apex of a vital tooth, is the aim of many vital pulp therapies to maintain immature permanent teeth. 2 Furthermore, non-vital pulp treatment is also indicated for preservation of bone, space, and function.

With the never-ending development of new dental materials and techniques, various materials have emerged for use in paediatric dentistry. One class of materials gaining a lot of attention in the scientific and clinical community is biosilicates. This essay aims to review the applications of biosilicates in paediatric dentistry and discuss their performance and efficacy compared to the alternative materials.

Biosilicates have many uses such as in temporary and permanent restorations, direct and indirect pulp capping, pulpotomy, root canal obturation, repair of root resorption and fractures. These uses can extend to both primary teeth and immature permanent teeth. The uses can be broadly separated into vital and non-vital pulp therapy.

Biosilicates are derived from Portland cements, which contain mixtures of calcium silicates, calcium aluminates, calcium alumino-ferrites, and calcium sulfates.6 However, unlike historical Portland cements which have many uses in the building industry, dental biosilicates are free from metal impurities to improve mechanical properties.7 The first documented use of Portland cement in dentistry was by Dr. Witte who used Portland cement to fill root canals in the 19 th Century. 8

Later, Portland cement was patented for use in endodontics as mineral trioxide aggregate (MTA), composed of Portland cement with the addition of bismuth oxide for radiopacity. 9 Some concerns associated with the original MTA formula included leaching of trace elements, stability of bismuth oxide, difficulty of manipulation and long setting time.5 As a result of these problems, a second generation of materials have been developed to address many of the concerns with MT A and improve biomechanical properties. These bioceramics are based on pure tricalcium silicate, and also allow biomineralization due to the formation of monobasic calcium phosphate by the reaction between calcium ions released from hydration of tricalcium silicate with free phosphate ions in tissue fluids. 5

Variations in composition of these cements results in a range of commercially available materials with various physical properties, chemical interactions, and dental applications. Of all the hydraulic calcium silicates that are available worldwide, most research conducted has been focused on MTA and Biodentine.

Indirect pulp capping
Indirect pulp capping is a non-invasive procedure which involves intentionally leaving the deepest layer of dentine intact over a symptom-free tooth with no signs of irreversible pulp inflammation or degeneration.2 The aim of indirect pulp capping is to place a biocompatible liner and a restoration with a satisfactory seal to avoid progression of the carious lesion, reduce the risk of pulp exposure, and allow tertiary dentinogenesis to occur .1

In addition to the other medicaments for indirect pulp capping such as calcium hydroxide, glass ionomer cements (GIC) and resin-modified GICs (RMGIC), biosilicates have also been indicated due to their high biocompatibility. While literature suggests that there are no significant differences in the success rates of indirect pulp capping with use of bioactive calcium silicates, calcium hydroxide cements, and RMGIC, it has been reported that the use of MTA induces harder dentine and reduces the presence of bacteria more than calcium hydroxide. 1,10

Calcium hydroxides have also been associated with disintegration and formation of tunnel defects in newly formed dentine, a problem that is not present with MT A. Although the need to re-open a cavity to remove all caries-affected dentine is questionable, the lack of void formation beneath insoluble MTA suggests that MTA is more suitable for use as a one-step treatment, allowing placement of a coronal restoration on a more solid base. 10

A randomized controlled clinical trial that compared Biodentine and Fuji IX GIC also failed to find a statistically significant difference in the clinical efficacy between these two materials. 11 However, on radiographic CBCT examination, they found that the majority of teeth with healed and healing periapical lesions had been treated with Biodentine whereas those with new or progressing lesions had received treatment with GIC. 11

Nonetheless, it is widely agreed that an accurate diagnosis of the pulpal status as well as the quality of the seal achieved by the coronal restoration are the main determinant for success of caries control and pulp preservation.

Direct pulp capping

A direct pulp cap with a biocompatible base such as MTA or calcium hydroxide can be placed in contact with a pinpoint mechanical pulpal exposure which has occurred through trauma or iatrogenic means.2 This procedure aims to maintain tooth vitality, allow pulp healing and dentine bridge formation in both primary and permanent teeth, but is not recommended for capping of a carious pulp exposure in a primary tooth.2

The ideal pulp capping material should be biocompatible, antibacterial, radiopaque, adhere to dentine, and induce tissue healing. Previous studies have investigated the effectiveness of different direct pulp capping materials, many of which have been summarised in a systematic review by Paula and colleagues. 12

This paper concluded that MTA and other tricalcium silicate cements have comparable success rates with lower inflammatory responses and more predictable dentine bridge formation compared to calcium hydroxide cements. Dental adhesive systems such as composite resin were found to have the lowest success rates and overall poorer results than use of calcium hydroxide. In addition, the use of hydroxyapatite material and enamel morphogenetic proteins were both reported with poor clinical results and in some cases, a complete absence of dentine bridge formation.

Despite the high success rates reported for laser light technique, it was not possible to determine whether the outcomes were due to the laser or the biomaterial applied following laser treatment. Finally, IRM has been shown to result in cytotoxicity and increased proinflammatory mediators compared to MT A. 13

Restorative material

Common restorative materials for use in posterior teeth have been amalgam, composite resins and glass-ionomer cements. Composite resins have seen a rise in application due to the demand for aesthetic adhesive restorations, however, they are associated with up to 30% of patients experiencing postoperative sensitivity. 14

Biodentine has been found to be a successful dentine substitute due to its increased compressive strength, decreased porosity and tight sealing properties compared to other biosilicates, as well  as their lack of postoperative sensitivity.7

For class I and class II posterior restorations, particularly in the case of deep carious lesions where evaluation of pulp healing is required before a definitive restoration is placed, Biodentine can act as a clinically satisfactory and  symptom free temporary restoration for up to six months. Is After six months, scores for  anatomic form, marginal adaptation and proximal contacts in Biodentine restorations were statistically significantly reduced. It was concluded that Biodentine is not a satisfactory enamel replacement but can act as a successful dentine substitute beneath composite restorations in Class I and Class II cavities. 15

Partial pulpotomy

Partial pulpotomy for carious exposures, or partial pulpotomy for traumatic exposures (Cvek pulpotomy) are the procedures in which l-3mm of the inflammed pulp tissue is removed in a vital tooth with normal pulp or reversible pulpitis. 2 This procedure is especially important to allow continued root development and apexogenesis in immature permanent teeth. Following haemostasis via a bactericidal solution such as sodium hypochlorite or chlorhexidine, the pulp is covered with a dressing material, a light-cured RMGIC, and a coronal restoration. 16

Although the gold standard, calcium hydroxide has been reported with high success rates as the gold standard for these procedures, recent evidence has demonstrated that MTA results in more  predictable pulpal response and dentine bridging.2,7

Pulpotomy

This procedure involves amputation of the coronal pulp and treatment of the remaining pulp tissue with a long-term medicament in a primary tooth with a carious or mechanical pulp exposure, in the absence ofradicular pathology.2 Pulpotomies have been performed using formocresol, ferric sulfate, calcium hydroxide, sodium hypochlorite and electrosurgery.

The access cavity is then filled with a suitable base, and a coronal restoration, typically a preformed stainless steel crown is placed. Formocresol was previously viewed as the gold standard, but with more recent concerns of cytotoxicity and carcinogenicity associated with formaldehyde, ferric sulfate has become the most currently accepted material. 18

Issues reported with calcium hydroxide such as internal resorption and lower rates oflong-term success have led to recommendations that this material is not suitable for pulpotomies. 18 MTA has been demonstrated to be more clinically and radiographically successful than both formocresol and ferric sulphate. 19

Furthermore, Biodentine has been found to have comparable success rates to MTA, but with the additional advantages of good marginal adaptation and strength for suitability as a restorative material.20 This avoids the need for placement of a separate restoration prior to placement of a stainless steel crown, thereby reducing treatment  time for paediatric patients.7

Apexification
Apexification refers to inducing calcific root end closure in an incompletely formed, nonvital permanent tooth by intracanal placement of a biocompatible medicament following removal of the coronal and radicular tissue. 2 Calcium hydroxide is often used for apexification but involves limitations such as variable treatment time ofup to 20 months, need for multiple visits, and increased risk of tooth fracture. 21

MTA is able to achieve similar rates of apexification compared to calcium hydroxide within a  significantly shorter amount of time, allowing earlier placement of a root canal filling and reducing chances for coronal leakage. In cases where complete apical closure cannot be achieved via intracanal medicaments, an apical plug can be placed using MTA or Biodentine.

The advances with Biodentine solves the issues of MTA such as difficulty of manipulation, poor mechanical properties and slow setting time, while also reducing treatment to a one-step obturation visit and releasing more calcium ions in solution.5•7

Root canal sealer

Biosilicates are not indicated for pulpectomy because that requires the material to resorb when the tooth exfoliates. In permanent teeth, bioceramics have been used as an alternative root canal sealer to the classical obturation with gutta-percha and resin-based sealer. Apart from the  advantage of not requiring a dry canal and removal of the smear layer, many obstacles are associated with the use ofbioceramic sealers. 5

The usual irrigating solutions such as NaOCl and ethylenediaminetetraacetic acid (EDTA) cannot be used with these bioceramic sealers, and while a phosphate-buffered saline irrigant is compatible for use and also results in enhanced biomineralizing ability, this irrigant reduces the sealer’s antimicrobial activity. Finally, the method of dentine bonding via alkaline etching causes softening of dentinal collagen and reduced flexural strength.5

Perforation

Perforation is the communication between the root canal system and external tooth surface caused by iatrogenic or pathologic means. Materials such as amalgam, cavit, composite resin, GIC, IRM and calcium hydroxide have been investigated as non-surgical perforation repair materials with a range of levels of success. 22 Some drawbacks of these materials include solubility, difficult handling, low mechanical strength and moisture incompatibility.7

Success has been demonstrated with the use ofbiosilicates such as MTA and Biodentine due to their excellent biocompatibility. 22 Furthermore, Biodentine has greater ease of handling compared to MTA, high push out bond strength, and is not affected by blood or moisture contamination. 7

Resorption

External and internal root resorption are possible complications following trauma, orthodontic treatment, pressure from teeth and cysts, as well as other pathological and infectious conditions. Resorption is often managed via removal of necrotic or infected pulp, intracanal medication with a corticosteroid-antibiotic and/or calcium hydroxide dressing, and restoration of the defects. 23

A number of case reports have used biosilicates, particularly Biodentine and MTA for the repair ofdentinal defects as well as obturation of the entire root canal system.7,23 Their efficacy is attributed to their alkalinity and sustained calcium hydroxide release.

Root fractures

Root fractures are another complication of traumatic tooth injury. While the survival rate for horizontal root fractures is relatively high, vertical root fractures are often associated with a poor prognosis and are a common indication for extraction. 24,25

In the case of horizontal root fractures, splinting of the tooth and monitoring is often the only management required. However, when a root canal treatment is indicated, the coronal, and in some situations the apical fragment, can be filled with conventional materials or with biosilicates as previously discussed. 24

Successful attempts at treating vertical root fractures have involved extraoral reconstruction of the fragments followed by intentional replantation, as well as surgical preservation technique with MTA sealing. 25

Unfortunately, all the literature on successful treatment of horizontal and vertical root fractures with biosilicates have only been case reports and further research is required.

From the first recorded use of Portland cement as an endodontic sealer in the 19th Century, the formulation and use ofbioactive calcium silicate materials has been developed and grown to encompass many applications within paediatric dentistry. Particularly in comparison to the alternatives, biosilicates have demonstrated similar, if not superior, results in direct and indirect pulp capping, temporary restoration, permanent dentine replacement, pulpotomy, apexification and perforation repair.

Reviews of the efficacy ofbiosilicates in applications such as root canal obturation, management of root resorption, and repair of vertical and horizo!1tal root fractures have yielded uncertain conclusions and require more research to be conducted. As improvements and modifications to the currently available dental materials continues to occur, it can be anticipated that new endodontic and restorative materials will be introduced for use in the treatment and preservation of pulp and teeth in both paediatric and general dental practice.

1. Garrocho-Rangel A, Quintana-Guevara K, Vazquez-Viera R, Arvizu-Rivera JM,
Flores-Reyes H, Escobar-Garcia DM, et al. Bioactive Tricalcium Silicate-based
Dentine Substitute as an Indirect Pulp Capping Material for Primary Teeth: A 12-
month Follow-up. Pediatric Dentistry. Sep 2017;39(5):377-82.
2. American Association of Pediatric Dentistry. Guideline on pulp therapy for primary
and immature permanent teeth. Reference Manual 2016-2017. Pediatr Dent 2 016;
38(6):280-8
3. Hench LL, Splinter RJ, Allen W, Greenlee T. Bonding mechanisms at the interface of
ceramic prosthetic materials. Journal of Biomedical Materials Research Part A. Nov
1971 ;5: 117-141.
4. Primus CM, Tay FR, Niu L. Bioactive tri/dicalcium silicate cements for treatment of
pulpal and periapical tissues. Acta Biomaterialia. Sep 2019;96:35-54.
5. Camilleri J. Will Bioceramics be the Future Root Canal Filling Materials? Curr Oral
Health Rep. Sep 2017;4:228-38.
6. Septodont. Biodentine™: Active Biosilicate Technology™ [Scientific File]. R&D
Department.
7. Sulaiman MA, Najlaa MA, Omar AE. Clinical Applications ofBiodentine in Pediatric
Dentistry: A Review of Literature. Oral Hygiene and Health. 2015;3(3).
8. Witte. The filling of a root canal with Portland cement. German Quarterly for
Dentistry. J Cent Assoc German Dent. 1878;18:153-154.
9. Torabinejad M, White DJ. Tooth filling material and method of use. US Patent.
1993;5:415,547.

10. Petrou MA, Alhamoui FA, Welk A, Altarabulsi MB, Alkilzy M, Splieth CH. A
randomized clinical trial on the use of medical Portland cement, MTA and calcium
hydroxide in indirect pulp treatment. Clin Oral Invest. Sep 2014;18:1383-9.
11. Hashem D, Mannocci F, Patel S, Manoharan A, Brown JE, Watson TF, et al. Clinical
and Radiographic Assessment of the Efficac of Calcium Silicate Indirect Pulp
Capping: A Randomized Controlled Clinical Trial. J Dent Res. Feb 2015;95(4):562-8.
12. Paula AB, Laranjo M, Marto C, Paulo S, Abrantes AM, Casalta-Lopes J, et al. Direct
Pulp Capping: What is the Most Effective Therapy? – Systematic Review and MetaAnalysis.
J Evid Based Dent Pract. Dec 2018; 18( 4):298-314.
13. Chang SW, Lee SY, Kum KY, Kim EC. Effects ofProRoot MTA, Bioaggregate, and
Micromega MT A on Odontoblastic Differention in Human Dental Pulp Cells. J
Endod. Jan 2014;40(1):113-8.
14. Briso ALF, Mestrener SR, Delicio G, Sundfeld RH, Bedran-Russo AK, de Alexandre
RS, et al. Clinical Assessment of Postoperative Sensitivity in Posterior Composite
Restorations. Operative Dentistry, Sep 2007;32(5):421-6.
15. Koubi G, Colon P, Franquin J, Hartmann A, Richard G, Faure M, et al. Clinical
evaluation of the performance and safety of a new dentine substitute, Biodentine, in
the restoration of posterior teeth – a prospective study. Clin Oral Invest. Jan
2013;17:243-9.
16. Mejare I, Cvek M. Partial pulpotomy in young permanent teeth with deep carious
lesions. Endod Dent Traumatol. Dec 1993;9(6):238-42.
17. Chacko V, Kurikose S. Human pulpal response to mineral trioxide aggregate (MTA):
A histological study. J Clin Pediatr Dent. Apr 2006;30(3):203-10.

18. Huth KC, Hajek-Al-Khatar N, Wolf P, Ilie N, Hickel R, Paschos E. Long-term
effectiveness of four pulpotomy techniques: 3-year randomised controlled trial. Clin
Oral Invest. Aug 2011;16:1243-50.
19. Ng FK, Messer LB. Mineral trioxide aggregate as a pulpotomy medicament: A
narrative review. Eur Arch Paediatr Dent. Mar 2008;9(1 ):4-11.
20. Juneja P, Kulkarni S. Clinical and radiographic comparison ofbiodentine, mineral
trioxide aggregate and formocresol as pulpotomy agents in primary molars. Eur Arch
Paediatr Dent. Aug 2017;18:271-8.
21. Lin JC, Lu JX, Zeng Q, Zhao W, Li WQ, Ling JQ. Comparison of mineral trioxide
aggregate and calcium hydroxide for apexification of immature permanent teeth: A
systematic review and meta-analysis. J Formos Med Assoc. Jul 2016;115(7):523-30.
22. Siew K, Lee AH, Cheung GS. Treatment Outcome of Repaired Root Perforation: A
Systematic Review and Meta-analysis. J Endod. Nov 2015;41(11):1795-1804.
23. Ashwini T, Hosmani N, Patil C, Yalgi V. Role of mineral trioxide aggregate in
management of external root resorption. J Conserv Dent. Nov 2013;16(6):579-81.
24. Cvek M, Tsilingaridis G, Andreasen JO. Survival of 534 incisors after intra-alveolar
root fracture in patients aged 7-17 years. Dent Traumatol. Aug 2008;24( 4 ):3 79-87.
25. Floratos SG, Kratchman SI. Surgical Management of Vertical Root Fractures for
Posterior Teeth: Report of Four Cases. J Endod. Apr 2012;38(4):550-5