Cement-Based Materials in Dentistry

Abstract

Cement-based materials in dentistry have experienced rapid development. In the field of operative dentistry, there are mainly developing calcium silicate cements, which have made it possible to solve previously difficult situations such as perforation of the root-canal system, direct pulp capping, filling and preserving teeth with widely open foramen apicale. These materials are based on the Portland cement. This chapter will describe the development, properties, indications and limitations of these materials. In the field of prosthodnotics, the prosthetic restoration is connected to the remaining tissues with the help of cements. Requirements for such materials and the available options will be described. The choice of suitable cement is based on its properties, requirements (such as moisture control), the material of the restoration (optimal choice can affect and strengthen the material) and the characteristics of the remaining dental tissues (such as the conicity of the prepared tooth). The chemical preparation of the tooth and prosthetic material connected with the individual types of the cements, which are capable to ensure the firm connection leading to the long-term and aesthetic result, will be described.

1. Introduction

According to ISO 9917-2:2017, cement-based materials in dentistry can be used as luting materials, as base or lining material, as material of restoration and as tooth core build-up [1].

The aim of this chapter is to present new treatment options and considerations based on up to date research and knowledge about cement-based materials in dentistry. For didactical and comparative reasons, the material with long history of use is discribed, too.

In operative dentistry, cements are used as base or lining material and as material of the direct provisional restoration.

Calcium silicate cements are the most developing materials in operative dentistry for their biological proprieties. Recently, the interaction of the calcium silicate materials and stem cells from periodontal ligament has been studied in vitro. The calcium silicate cements showed adeqaute osteogenic and cementogenic potential. The influence of additives, mixing technique and different condition on biological proprieties and clinical success stays as a question for future [2].

As recent research studies showed with use of calcium silicate cements immature teeth with pulp inflamation can be maintained and even the development of the tooth can continue, when the diagnosis is done properly, biology and material are understood and the protocol for treatment is done properly [3].

According to up-to-date proofs, the pulpotomy can be considered as less invasive alternative to root canal treatment for teeth with massive caries destruction and with pulp alteration, even if it is irreversible in the defined part of the pulp. Consideration for treatment and material selection are going to be described. New materials allow clinican less invasive treatment options [4].

For its high biokompatibility, the calcium silicate materials are also studied apart from dentistry as a drug delivery system [5].

Cement-based materials in prosthodontics are used for luting indirectly fabricated restoration and core build-up.

Composite resin-based cements (adhesive cements) are indicated for core build-up for their mechanical proprietes.

Luting could be done as provisional or definitive.

The connection of prosthesis and dental tissue—cementation is an extremely important step in prosthodontics. The prosthesis is cemented to different prosthetic materials, different dental tissues and filling materials. Individual materials have different requirements for maintaining dryness in the oral cavity. Based on material characteristcs, the suitable cement is choosen. Materials of the cementation are constantly evolving and improving.

As in 2019, there was a question if universal adhesives can bond to zirkonium ceramics, as this is unpretreatable by etching in contrast to ceramic with glass, nowdays the protocols for adhesive cementation are defined and can be discussed [6].

New protocols and molecule of 10-Methacryloyloxydecyl dihydrogen phosphate (10-MDP) allow adhesive fixation of zirconium ceramics, what used to be unpredictable and challenging. This presents a milestone in a prosthodontic dentistry. The higher clinical success of ceramic restorations is expected [7].

However, the adhesive layer can be decomposed by enzymes matrix metalloproteinases, what makes it instable in time. Recent studies show that the molecules such as chlorhexidine digluconate and captopril are able to inhibit these enzymes. Effectivity of these molecules and other alternatives should be researched [8, 9].

Improper selection of cementation material, incorrect use or imperfect removal of excess can result in premature failure.

Cement ensures the retention of the restoration. In the following chapter, the protocoles and materials are discussed as well as materials with long history of use. This chapter goes systematicly through different options of cements use and summarises evidence-based protocols, considerations for modern materials selection and discusses their advantages and disadvantages.

2. Cements in operative dentistry

2.1 Provisional restoration materials

Provisional filling is used for two main reasons: for sealing endodontic access before final root canal obturation to prevent reinfection, and from time reasons to maintain esthetics and functionality of teeth which will be repaired by definitive filling in near future.

Regarding deep caries lession, the marginal seal could not be suficient. It is clinicans‘ choice to restore with provisional filling and wait or with definite one which can also act as preendodontic build-up in case of failure.

Different materials can be used such as zinc polycarboxylate (also known as zinc polyacrylate), zinc phosphate cement, zinc oxid sulphate and glass ionomer cement (for filling material maximum particle size is 50 um, mechanical proprieties are described American National Standards Institute–American Dental Association (ANSI-ADA) Specification No. 96 (ISO 9917 [2000]). Although the glass ionomer releases flourides, it is sensitive during setting and the final the surface can be rough, so the author does not see an advantage for patients with low oral hygiene level [10, 11].

2.2 Base and lining material

Those are materials placed between restoration and dentin with the intention to protect the pulp. They were used espcialy under amalgam fillings.

Dental liner is placed in thinner layer, then dental base material.

Liner is a material that should idealy seal dentinal tubules and protect the pulp.

As liner, a varnish and calcium hydroxide can be used. In literature, glass ionomer and resin can be found, but these materials are used as a whole filling.

Layer of liner is approximately 0.5 mm.

Varnish is natural gum dissolved in solveont which is going to evaporate after its placement to cavity, leaving thin layer, thus reducing microleakage. It was used historicaly with amalgams. Varnish is wash-out of the margin and inhibits bonding of glass ionomer [12].

Calcium hydroxide has ability to stimulate tertiary dentin formation. It can be used even for direct pulp capping. Calcium hydroxide can be supplied in two paste forms or as light-cured material. It shows bactericidal proprieties, pH is around 11–12, and it is highly soluble. The material is moisture sensitive with weak mechanical proprietes. It can be used in proximity to pulp approximately 1–2 mm. Calcium hydroxide can be placed under the base material. There is a long history of use of calcium hydroxide. Calcium hydroxide can be also used in endodontics as intracanal medicament to desinfect root canal system [13].

Base materials are zinc oxid phosphate, zinc oxid eugenol, zinc polycarboxylate (zinc polyacrylate). Dental base material should protect the pulp by thermal isolation and by absorbing oclusal forces. Dental specialist can find these materials after removing old amalgam restoration, where they were used.

Glass ionomer and composite resin are not used as base materilas, but they have the same characteristcs such as providing barrier. Composite resin can be shaped and prepared complex morphology of the tooth surface for indirect restoration [12].

2.3 Calcium silicate cements and its development

Calcium silicate cements are hydraulic cements based on portland cement. First commercialy available product was Pro Root MTA (mineral trioxide aggregate). In literature, sometimes MTA is used for whole group of cements—calcium silicate cements. Calcium silicate materials are setting by hydration, and they have low solutibility. During setting the cements are slightly expanding in volume.

Original patent for MTA—the first of a large generation of calcium silicate cements—“MTA consists of 50-75% calcium oxide and 15-25% silicon dioxide.” MTA is type 1 portland cement according to American Society for testing and materials Standard C150/C150M–12 2012–12 2012. Bismuth oxide was added to the first product MTA as radioopaficer [14].

Clinker of portland cement consists mainly of tricalcium silicate. Dicalcium silicate reacts and solidifies slower. These two components can be 80% of potland cement. Around 10% is gypsum. Calcium carbonate forms relatively bigger particles, thus reacting as nuclaeting centrum, thus accelerating setting. As 3–4 h are clinically in some situations unacceptable. Calcium carbonate is contained in Biodentin. This material sets in 12 minutes, and it can be used as provisional filling. Dicalciumphosphate is a dash of the latest calcium silicate materials, which encourages the production of hydroxypatite layer. This can lead to higher bond to dentin. Dicalciumphosphate is a dash of the latest calcium silicate materials, which encourages the production of hydroxypatite layer. This can lead to higher bond to dentin [15, 16].

Calcium silicate materials in wet condition release Ca2+ ions, these react with phospahtes present in the blood, and on the surface of calcium silicate material, the apatite/hydroxyapatite layer is formed. This is the reason of the biological tolerance of this material [17].

MTA sets (medium setting time) at 165 + −5 min. It reacts with water [18].

The pH after mixing was measured to be 10.2. It rises to 12.5 in 3 h and then stays constant [19].

During mixing, the higher volume of fluids leads to increased porosity and consequent solubility [20].

Calcium silikate materials unlike calcium hydroxide are not absorbed so quickly and lead predictably to form an apical seal. This is used for obturation root canals with wide apical foramen [21].

As mentioned before, the MTA expands slightly during solidification, which contributes to marginal seal. This depends on the proportion of water contained in the mixing.

Gypsum is added to MTA to influence time of the setting. Bi₂O₃ was added to increase radiopacity. Bi₂O₃ after contact with NaClO (commonly used root canal disinficient) changed its colour to dark brown. Radioopaficier can migrate in dentin and cause tooth disoloration. Other radioaque matherials are used in different calcium silicate cements such as zirconium dioxide or tantalum pentoxide [22].

To facilitate manipulation in latest materials, propylenglycol can be used by the manufacturer to adjust consistency [23].

Accelerators of setting such as calcium chloride can be used, what was a new step of the material development. This allowed to introduct provisional filling material based on calcium silicate cements. Material called Biodentin (Septodont) sets 12 min, what is clinically acceptable time of setting. This material is indicated for direct and indirect pulp capping [24].

Calcium silicate cements can be mixed by dental assistent or mechanically. They can be delivered premixed in syringe or as powder and liquide or as paste in consistency. They can be delivered unpremixed such as powder and liquid. Diffrent consistencies are available such as sealer, putty, paste.

Delivery on its place is possible by plugger, map system, dovgan applicator, micro-carrier, or Lentulo spiral [25, 26, 27, 28, 29].

Development of these materials was follow these principles. Adding radioopaficier. And subsequently searching for radioopaficier which does not react with natrium hypochloride and does not cause tooth discolouration. Easier preparation and easier handling were achieved. Influencing setting time and thus allowing easier clinical application.

Clinical applications of the calcium silicate cements are pulp capping (direct or indirect), pulpotomy, open apex obturation, root perforation rapair, endodontic apical microsurgery, external and internal resoption repair and regenerative endodontics and as a root canal canal sealer.

2.3.1 Direct pulp capping

During treatment of deep caries, in dental traumatology or even during preparation for prosthetic work, the vital pulp can be exposed. To avoid inflamatory complications in dental pulp, this tissue should be treated in correct way (Figure 1).

Figure 1.

Large carious defect resotred by composite filling, in the pulp chamber the calcium silicate cement used for direct pulp capping is visible. Three years after treatment the reaction on the cold test is positive.

MTA was found as a superior material for a direct pulp capping when compared with CaOH in research with 2-year follow up [30].

Direct pulp capping for success requires uninfected pulp without inflamatory changes and peripheral seal which does not allow further bacterial iritation. Differential diagnosis between reversible and ireversible changes in dental pulp cannot be based only on patient complaint, but more objectively is based on ability to ensure hemostasis during 5–10 min with 1.5–6% sodium hypochlorite. Calcium silicate cement used for direct pulp capping should not contain bismuthtrioxide because of discolouration risk. Calcium silicate cement should be applied through the preforatin to ensure proper bond to hard dental tissues. The antimicrobial aktivity of calcium silicate material is advantageous. Clinacaly reasonable is utilisation of materials with shorter setting and with higher compressive strength resistence [31, 32].

2.3.2 Pulpotomy

Pulpotomy according to American Association of Endodontists means removing irreverisibly inflamatory changed coronal part of the pulp and remaining and preserving radicular part of the pulp. Pulpotomy can be done on permanent teeth with or without closed apical foramen (what is a sign of the end of the root development). Pulpotomy can be also done on decidual teeth. Procedure is done by sterile diamond bur or by electorsurgery. After hemostatis the CaOH or calcium silicate cement is placed and the tooth is adhesively reconstructed. Calcium silicate cements are superior materials in this indication. Logically it is not indicated when whole pulp is necrotic and apical periodontitis is present. The vitilaty tests and finding pulp tissues intracoronaly are the mandatory conditions. Periapical radiographs can mislead clinican by periapical rarefaction—flase-positive presence of periapcal radiolucency. Pulpotomy of permanent teeth with closed foramen apicale is advantageous when the complicated root canal anatomy is present, also from time reasons and requirements for minimal invasivity. When the hemostasis cannot be obtained, the conventional endodontic treetment is indicated.

The pulpotomy on vital undeveloped teeth with pulp exposure is justified by intent to end the root development.

Pulpotomy on decidous teeth is technically very difficult, because children as patients are not so cooperative as adult patients and handling with rubberdam can be very difficult. General anestesia can be the solution for uncooperative patient, but its indications should be judged carefully [33, 34] (Figures 2 and 3).

Figure 2.

Dental trauma in dog. Pulpotomy was performed using calcium silicate cement and composite filling.

Figure 3.

Dental trauma in dog. The pulp tissue stays vital after pulpotomy using calcium silicate cement and composite filling.

2.3.3 Open apex obturation

Open apex occurs after pulp necrosis at incomplete root development what may be caused by dental trauma, iatrogenic by overinstrumentaion and as result of inflammatory root apex resorption when the root canal infection is present. Thin walls of immature teeth with necrotic pulp are more prone to fracture, additional layer of calcium silicate material at least 3 mm thickness should be placed. Thin walls of immature teeth with necrotic pulp are more prone to fracture, additionally. The clinical challenges are in the determination of working length as well as optimal obturation avoiding the extrusion of the material beyond foramen apicale.

First of all, the appropriet approach should be choosen. The clinican should choose if it is desirable to create “apical constriction”. Apexification is the procudure based on repative aplication of calcium hydroxide, thus creating calcified aoical barier. This can take from 5 to 20 months.

Due to development of calcium silicate materials, single visit obturation of open apex is now possible.

A layer of calcium silicate material at least 3 mm thickness should be placed. Can be condensed against the inner matrix for resorbable hemostipic material which does not allow extrusion through the apex. Than the adhesive coronal seal is made (Figures 4–6) [35].

Figure 4.

Open apex and wide foramen apicale, coronal part is filled with internal bleaching aget, as a complication of the treatment, tooth discolaration was observed.

Figure 5.

Open apex and wide root canal system filled with calcium silicate cement.

Figure 6.

Apical part of the tooht is filled with calcium silicate material.

Regenerative endodontics is another option to create apical stop using calcium silicate materials placed on blood clot. Although the changes in root apex are visible on radiographs, the dentin in the cervical area will not regenerate. histological finndings and practical consideration are discussed in the chapter on regenerative endodontics.

2.3.4 Root perforation repair

Success of treatment of root perforation repair is affected by localisation of perforation, abscence of contamination and time to the definitive treatment. Root perforation contaminated by communication with oral cavity (for example, by perio pocket) has the worse prognosis for healing. The higher the perforation is, the mechanicaly weaker the tooth is. Bleeding control is more difficult, so the inner matrix technique can be the option. Root perforation in supracrestal area is reparable by composite resin with combination with surgical approach. The success with calcium silicate cement is jeopardised by wash-out. Calcium silicate cements should not block visibility or make it impossible to find and work in root canals. This is the reason why the calcium silicate material should be placed after root canals negotiation. Apical perforation can be treated by ortograde access or retrograde microsurgical access. Coronal perforation is in danger of periopocket formation, even after surgical repair of the perforation (Figure 7) [36, 37, 38].

Figure 7.

Perforation repair.

2.3.5 Endodontic apical microsurgery

The calcium silicate cements with high biokompatibility, setting in wet conditions, antimicrobioal activity and bonding to dentin present highly indicated materials for endodontic microsurgery. Handling of the material is very important for the very difficult conditions in apical microsurgery. The visibility and the application in limited space are challenges. Radiologic control is neccesery. Fast set materials are advantageous. Putty concistency materials can be placed comfortably for the clinician (Figure 8) [39].

Figure 8.

Calcium silicate cement placed ortogradialy followed by root resection and cystic lession removal facilitate surgical procedure.

2.3.6 External and internal resorption repair

Dental tissue resorption can occur after trauma, orthodontic treatment, chronic inflamatory dissease in pulp or in periodontal tissues. Predentin and precement layer are protecting the tissues before clastical cells. In general, two big groups of resoption exist: internal and external. Internal resorption origins in root canal, and it is the consequence of chronicaly inflamatory changed pulp. Even in condition when part of the pulp is necrotic, the apical part can be inflamatory changed and caused resorption. Root canal treatment is indicated and calcium silicate sealers or calcium silicate cements can be option for root canal obturation. External resorption exists in four forms: 1. external surface resorption, which is transient and requires no treatment; 2. invasive cervical resorption which can be consequent of trauma, intracoronal bleaching, orthodontic, surgical or periodontal treatment. Based on its range the surgical approach, endodontical approach or extraction can be indicated. Pulp tissue is protected by predentin layer. The vitality of the teeth should be protected, but it is sacrificed when this approach is less invasive due to apical extent of resorption. Calcium silicate cements can be used to root canal obturation or resorption cavity filling. This can be done also with composite resin or glass ionomer. 3. Inflamatory root resorption is often consequence of trauma and infected necrosis of the pulp. The bacteria and interleucine induct inflammation which leads to prograssive root resorption. Open apex can be created this way, then the calcium silicate materials in apical portion of the root canal are indicated for obturation as descused before. 4. Replacement resorption is connected with luxation and necrosis of periontal ligaments. The tooth itself is gradualy replaced by bone [40, 41].

2.3.7 Regenerative endodontics

Immature necrotic teeth can be revascularised by intracanal bleeding stabilised by calcium silicate cement. Advantageous is cement with low tendention to discolouration and fast setting. The radiological dentin-like structure is then observed to form in the canal—immitating the root development. From mechanical point of view, it is not clear if the resistence of the tooth is going to get stronger to occlusal forces. The dentin in cervical area will not be formed [33].

There is a histological finding not confirming dentin production. The mineralised tissue does not adhere to dentinal walls [42].

2.3.8 Root canal sealers

Root canal sealers are group of cements used with guttapercha to fill the root canal space, where are irregularieties between gutapercha and root canal walls block further bacterial growth and isolate remaining bacterias from nutrients. The hermetic seal is desired. Sealer can fill lateral canals, voids and apical delta. Root canal sealers should have optimal mixing and setting time (to allow proper obturation), radioopacity, reology and should not discolourate teeth. It is desirable to be antimicrobiologicly active and not to cause inflamatory respons or cytotoxicyty. Bind to the dentinal walls of the canal and tacky consistency. It is required to contain fine powder. Insolubility is desired as well as posibility of removal during retreatment. Preferably biocative in nature. Ideal root canal sealer does not exist. MTA-based sealers fullfil many of desired characteristics (Figure 9) [43, 44].

Figure 9.

Root canal is filled with calcium silicate cement based sealer, composite cement is used for core build-up and provisional restoration is cemented with provisional oil-based cement.

3. Cement-based material in prosthodontics

3.1 Provisional cements

Temporary cementation is suitable for temporary restorations, which will soon be replaced by definitive ones. Temporary restoration has the following advantages: 1. protection of the abutment against mechanical, thermal and chemical damage; 2. gingiva shaping or definition of ideal gingival zenith (using biologically oriented preparation technique); 3. protection of finish line against damage; 4. preservation of spatial conditions—prevents the inclination of adjacent teeth, prevents the tooth from entering supraocclusion; 5. aesthetically and functionally replaces lost tissues. In case the final restoration is cemented adhesively, the temporary cement must not contain eugenol. Temporary cements are usually oil-based. Modern temporary cements are oil-based zinc oxide without eugenol. Compared with final cements, they have weaker physical properties and form a thicker layer of material. Temporary cement is also suitable for office cementation of suprastructures on implants. It will allow us greater repairability of protective work compared with final cements. Cemented implant work is rarely used, excess cement can cause periimplantitis. Screwed restoration is more suitable [45, 46].

The requirements for temporary cements are: biocompatibility, easy removal from the tooth surface, easy removal from the restoration surface, easy material preparation, easy removal of excess, clinically acceptable setting time, temporary cement must allow easy removal of the temporary restoration but ensure good retention. It must not react with the final cement [47].

Temporary cementation of definitive restoration is high risk! Abutment teeth can be damaged when removing the final prosthesis. The author does not recommend the use of temporary cements for big prosthetic reconstructions. It is more appropriate to extend the time with temporary prosthetic work than to temporarily cement the final work. In addition, temporary work can be easily modified. Temporary cement must be thoroughly removed before final cementation, residues of temporary cement preclude the achievement of maximum efficiency of the final cement. In a special case—that is, during reconstruction with aesthetic veneers—when preparation is non-retentive, a point-adhesive-prepared surface and composite cement can be used to cement the temporary veneers. The size of the adhesively prepared surface in clinical practice is approximately 1 mm × 1 mm. There is also a possibility to use mock up [48].

3.1.1 Definitive cements

Definitive cements can be divided in two groups: water-based and adhesive cements (composite resin based) [1].

In addition to cement, the retention of the restoration is also ensured by the preparation itself and the bevel angle of the preparation. At the same bevel angle, the adhesive cements provided twice the retention force than conventional glass ionomer cement or zinc oxide phosphate cement. At a 24 degree preparation angle, the retention force was 20% higher using resin cements than at a 6 degree preparation angle using conventional cements. This demonstrates the higher retentive properties of adhesive cements [49].

We generally require low viscosity from cements so that they form the smallest possible layer [50].

The preparation of surfaces, which are connected with cements, also varies.

3.1.2 Water-based cements (acidobasic cements)

When setting, they go through acido-basic reaction. This may explain the transient increased pulpal sensitivity after cementation [51, 52].

They are not as susceptible to the presence of water as hydrophobic resin cements. It is clinically appropriate to provide a relative dry field. We use it advantageously for deep preparations, where the moisture control is problematic.

The main represenatatives of watter-based cements are: zinc oxide phosphate, glass ionomers and resin-modified glass ionomers.

3.1.2.1 Zinc oxide phosphate

Zinc oxide phosphate does not bond to teeth structure. What is advantageous is easy removal of excesses. High early strength makes it suitable for cementing metal cast posts. The material is characterised by high compressive strength and low tensile strength. There is very low Ph during solidification. It is well soluble at first. Clinican should be aware of contamination with saliva [53].

3.1.2.2 Glass ionomers

Although they are well-known as glass ionomers, the correct name for them according to the International Organisation for Standardisation is glass polyalekenoate cements. It is a mixture of weak acids and with glasses, which is chemically based and except of setting reaction, it works as a filler. Glass ionomers are characterised by binding to hard dental tissues. This bond is mediated on a mineral basis and is slightly higher to the enamel (2.6–9.6 MPa) than to the dentin (1.1–4.1 MPa), but the failure in most studies was cohesive. The tensile strength of glass ionomer cements is relatively low. It solidifies in minutes, can be mixed by hand or in a blender and be applied from a capsule. The acids used in glass ionomer cements are polyalkenoic acids, either as a homopolymer of acrylic acid or a copolymer of acrylic acid and maleic acid. The contained glass is alumino-silicate with floride and phosphate. Without aluminimum, the glass only from SiO₄ would not be reactive with acids. Al caries 3+ charge and when implemented into tetraedrical geometry of silicon—the glass become base [1, 53].

Solidification takes place in several stages. It usually takes 2–3 min before they lost flow (sometimes up to 6 min). Early solidification of the material leads to an improper fit of prosthetic work or to the impossibility of applying this material to the cavity. The first phase of solidification is just the reaction of weak acids and glass, ions such as Ca, Na move. Subsequently, cross-linking occurs, for which Al ions are responsible. It takes about a day. They are initially sensitive to water, premature drying out or early matrix removal can lead to rough surfaces [53].

Water is the medium in which the reaction takes place and in which the acids are dissolved. Excessive drying and cracking of the surface can occur during solidification—this is prevented by varnishes from resin.

Glass ionomer cements can be used as a fixing material, but also as a restorative material as mentioned before. The properties it should achieve are defined by the iso standard. In both cases, they are different. The minimum compressive strength for luting material is 70 MPa [53].

Glass ionomers are bonding chemically to hydroxipapatit. As advantage can be seen that they are releasing fluorides, this property decreases with its maturation [53].

Disadvatage is mainly in restorative dentistry as glass ionomer fillings are not so mechanically resistant to function as a long-lasting definitive filling. Fixation cements are radiopaque to check for excess removal.

Traditionally, there are three types: 1. fixation, 2. restorative, 3. lining and base [53].

For fixation the dentin can be slightly wet, but with no watter or saliva pooling on the surface.

Cementation in prosthetics by glass ionomer is indicated especially for these materials: metal and metal-ceramic crowns, zirconium ceramics . Otis indicated for this prosthetic works: crowns, fixed partial denture and root inlay. The onlay or adhesive bridges cannot be cemented by water-based cements as the preparation itself is not retentive. The indication does not differ for other watter-based cements.

3.1.2.3 Resin-modified glass ionomers

The improvement of mechanical properties and handling of glass ionomer materials was created by their modification with a resin matrix. Cements are more mechanically resistant and are not so prone to early water contamination in contrast to conventional glass ionomer cements. The solidification of the resin matrix can be ensured chemically. However, the content of HEMA compromises their biocompatibility [54].

3.1.2.4 Adhesive cements

For adhesive fixation, we use composite cements (based on methacrylate resin with different contents of monomer, fillers and silane) light-curing or dual-curing. Dual-curing has the advantage of curing even under a prosthesis that is opaque or too large for light to penetrate, as the light begins polymerisation. Low translucency lithium disilicate discs showed improper degree of conversion under 1.2 mm thick material for light-curing cements [55, 56] (Figure 10).

Figure 10.

Example of adhesive cement before mixing.

Light-curing materials show less tendency to colour change in time than dual-curing materials. They are therefore more suitable when there is high aesthetic demand [57].

Adhesive cementation of the etchable ceramic leads to a significant increase in the flexural strength of the ceramic. However, this is sensitive to water contamination. For long-term success, it is important to maintain absolute dry field during cementation secured by rubberdam [58] (Figures 11 and 12).

Figure 11.

Lower second molar before adhesive cementation. Dry field is maintained by rubberdam.

Figure 12.

X ray showing the fit and the lack of cement excesses after cementation of lower left first molar.

If it is possible to fix the ceramic work adhesively, it is recommended, because it also improves the mechanical properties of the ceramic itself, especially in bending.

We use them if the preparation of the tooth pillar itself does not provide good retention.

For example, veneer preparations do not provide retention. It is therefore advisable to use adhesion to the enamel. Seventy percent of the enamel should be considered as a recommended.

Materials with a high glass content provide the possibility of high aesthetics such as transparent incisions. However, the amorphous ceramic glass and the low content of crystals (responsible for the mechanical resistence) require a very strong adhesive fixation to ensure the resistance of the restoration.

It is easier to achieve higher adhesion to enamel than to dentin. Adhesive preparation of dentin for indirect replacement should be performed immediately, collagen fibres are not exposed to saliva, bacteria are prevented from accessing the pulp. IDS or resin coating thus takes over some of the functions of the temporary restoration [59].

American Dental Association (ADA) specification no. 8 and ADA/ANSI specification No. 96 defined ideal thickness of the material of the cementation as 25 um or less. This is important for precise setting of the restoration and also for dental technician to fabricate the restoration which is satisfying even after adding material of the cementation. Depending on the material of the restoration, the luting cement colour and opacity can slightly influence the perceived colour. In the case of severly discoloured abutment teeth, the desired colour change is probably not achievable by 25 um of cement material. It is reasonable to change the colour in the prosthetic restoration [60, 61, 62].

3.1.2.5 Adhesion to hard dental tissues

Adhesion to natural hard dental tissues involves two basic approaches: total etch (also known as etch and rinse) and self-etch adhesive. Composite cements used for total etch approach require etching by 37% phosporoc acid (enamel 30 s and dentin 10 s) and rinsing. After this procedure, apllication of the adhesive (one or two botles) is possible. Although the adhesive system is self-etch, cements connecting acid monomers are self-etch, self-adhesive. By this the application of the adhesive system is eliminated. Self-etch self-adhesive cements contain acid monomer, which is etching and priming tooth structure. This leads to reducing steps in cementation procedure. Etch and rinse systems lead to creating more retentive pattern in enamel. Total etch approach is superior when the retention is mostly to enamel. Effectivness of self-etch self-adhesive cements can be improved by selective etching [A] (Figures 13 and 14).

Figure 13.

Veneer preparation—note the preserved enamel.

Figure 14.

Selective etching before cementation.

Bonding to dentin is complicated by higher organic and watter contain. The bonding strength decreases over time. The bonding strength of self-etch adhesives is more stable in time in dentin. Self-etch approach offers this advantage when bonding to the large areas of dentin [63, 64, 65].

Self-etch self-adhesive cements bond suffciently to dentin, but preetching of the enamel is advisable [66, 67].

As was shown in a recent study [67], if only IDS is performer, than the sandblasting exposes the dentin and reetching and pretreating dentin are advisable. Another option is to reinforce IDS with flowable composite, thus creating a resin coating. Then the adhesive procedure is done on composite surface [B].

3.1.2.6 Bonding to dental composite

Bonding to dental composite brings several challenges such as no presence of free monomer in the composite (during the direct fabrication of the composite filling the layering technig utilise the inhibition layer on the surface of the composite by which next layer is connected). The highest bonding strength to industrial composite was achieved by mechanical and chemical conditioning. Mechanical sand blasting with alumina—air abrasion. Chemical pretreating by etching, application of universal primer and silane. This was suggested as a best strategy by meta-analysis from 2019. Other strategies reducing steps were also suggested. However, pretreatment of the surface of composite is indicated [68].

The sandblasting, rinsing with water and air drying are also efficient ways of preparing composite surface to applying adhesive [69].

3.1.2.7 Bonding to ceramic with glass contain

Ceramic with glass offers high estetic solution. However, it is suspectible to fracture. The lithium disilicate ceramic (representative of resistant but esthetic ceramic) can with thickness 0.3 mm offer a flexural strength of 400 MPa (Figure 15).

Figure 15.

Indirect prosthetic restoration before cementation.

Ceramic restoration is etched by HF 4–9%. The time of etching depends on glass. For lithium disilate ceramic, the time of etching is 20 s. The ceramic restoration is rinsed with water spray and can be placed into ultrasonic cleaner. Salt hexaflourosilicate is released. The crystals are exposed and micropores for resin cement are accesible. Silane (SiH4) reacts with OH group (inorganic part) and with methacrylate group (organic part), thus connecting restoration and cement. Feldspatic ceramic with high content of glass should be etched in 60 s, but is also vulnerable to over-etching. Ceramic with high content of Al₂O₃ even after etching is not sufficiently prepared. For such a ceramic sandblasting can create microporosites. This requires very resistant ceramic and ceramic with higher content of glass could be broken (Figures 16–18) [70, 71, 72].

Figure 16.

Surface of ceramic with low glass contain, application of 4% HF.

Figure 17.

Surface of ceramic with low glass contain after etching using 4% HF.

Figure 18.

Silane applied on indirect restoration with low glass contain.

3.1.2.8 Bonding to the polycrystalic ceramic

The flexural strength of ZrO2-based ceramics is up to two times greater than lithium disilicate ceramic. Cementation in relative dry field on glassionomer cement is clinicaly easy. However, some clinical conditions ask for adhesive cementation to ensure higher bonding strength and hopefully longevity of the restoration. For example, parafunctional habbit requires high resistant restoration and the length of clinical crown can be compromised, this is a combination of risk factors, which is dificult to solve without polycrystalic ceramic and without adhesive cementation. Polycrystalic zirconia ceramic can refer to differently marked ceramics such as 3Y, 4Y and 5Y. This refers to Yitria content, with the higher content of Yitria, the higher translucency can be achieved. Adversely, with higher Yitria content, the less flexural strength of the ceramic. The damage of the ceramic through sandblasting is neglectable. The same protocol can be applied on 3Y, 4Y and 5Y zirconia. Air abrasion followed by application of special primer with monomer 10-methacryloyloxydecyl dihydrogen phosphate (MDP) or composite resin cements containing MDP can lead to the long-term bond [73, 74, 75].

4. Conclusion

Calcium silicate cements and adhesive cementation of different materials offer many advantages, which changed dental medicine. Less invasive approach is now possible due to development in the field of cements. Nevertheless, these materials have their own disadvantages and challenges. Clinicans should keep in mind both and not to believe in marvellous material, but to know their own materials, their requirements and still follow basic principles.

Acknowledgments

Authors appreciate support from Klinika zubního lékařství LF a FN which creates incredible working condition for both scientific and dental work.

The chapter was supported by funds IGA LF 2022 043 and IGA LF 2022 021.

Conflict of interest

The authors declare no conflict of interest.

Thanks

To my parents for continuous support and encouragement during work as a scientist and doctor.

To Abanoub Riad, PhD. for humble, hard-working scientific work, which inspire me.

To Dr. Pavel Holík, PhD., Dr. Roman Moštěk, Dr. Matouš Kašpar and Dr. Matěj Rosa for their friendship and for their X-rays which they provided to me.

To the women I love.