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Pulp protection during operative dentistry treatment by dr. ebsa
- 1. Pulp protection during operative dentistry treatment Presented By DR. EBSA TOWFIK(DI) Modulators: Dr. Getachew Abera, Dr. Selam Fisea
- 2. Course Outline ⢠INTRODUCTION ⢠PULPAL IRRITANTS ⢠EFFECT OF DENTAL CARIES ON PULP ⢠EFFECT OF TOOTH PREPARATION ON PULP ⢠EFFECT OF CHEMICAL IRRITANTS ON PULP ⢠Factors Influencing the Effect of Restorative Materials on Pulp ⢠PULP PROTECTION PROCEDURES ⢠Pulp Protection in Shallow and Moderate Carious Lesions. ⢠Pulp Protection in Deep Carious Lesions ⢠MATERIALS USED FOR PULP PROTECTION ⢠Varnish ⢠Adhesive Sealer ⢠Liners ⢠Bases ⢠METHODS OF PULP PROTECTION UNDER DIFFERENT RESTORATIONS ⢠Amalgam ⢠Restorative Resins ⢠Glass Ionomer Cements ⢠Cast Gold Restorations 8/28/2021 Pulp protection during operative dentistry treatment 2
- 3. INTRODUCTION ďśPulp is small tissue with big issues. ďśBy definition pulp is the highly specialized and sensitive vital structure within the tooth must be protected against all sorts of irritation during instrumentation.
- 4. PULPAL IRRITANTS ďVarious pulpal irritants can be: 1)Bacterial or chemical. 2)traumatic(mechanical), 3)Iatrogenic 4)Idiopathic
- 5. Bacterial irritants: ďMost common cause for pulpal irritation are bacteria or their products which may enter pulp through a break in dentin from: ďźCaries(most common route) ďźAccidental exposure ďźFracture ďźPercolation around a restoration ďźExtension of infection from gingival sulcus ďźPeriodontal pocket and abscess Pulp protection during operative dentistry treatment 8/28/2021 5
- 6. EFFECT OF DENTAL CARIES ON PULP ď Dental caries is localized, progressive, decay of the teeth characterized by demineralization of the tooth surface by organic acids, produced by microorganisms. ďAcids and other toxic substances penetrate through the dentinal tubules to reach the pulp. Pulp protection during operative dentistry treatment 8/28/2021 6
- 7. ⌠ďThe following defense reactions take place in a carious tooth to protect the pulp ⢠Formation of reparative dentin ⢠Dentinal sclerosis, i.e. reduction in permeability of dentin by narrowing of dentinal tubules ⢠Inflammatory and immunological reactions Pulp protection during operative dentistry treatment 8/28/2021 7
- 8. EFFECT OF TOOTH PREPARATION ON PULP ďFactors affecting response of pulp to tooth preparation 1) Pressure(10mmHg/13mmHg/35-40mmHg) 2) Heat(second)-more RPM, pressure, SA of contact, desiccation. Pulp protection during operative dentistry treatment 8/28/2021 8
- 9. ⌠1) Vibration(>amplitude+microcracks) 2) Speed(3000-30000rpm without coolent) 3) Nature of cutting instruments(worn off & dull)> +P> +T 4) Remaining dentin thickness(N:3 mm)-(2 mm or more enough R) Pulp protection during operative dentistry treatment 8/28/2021 9
- 10. EFFECT OF CHEMICAL IRRITANTS ON PULP ďpulp is subjected frequently to chemical irritation from materials generally used in dentistry; that could cause pulpal injury ďFactors Influencing the Effect of Restorative Materials on Pulp. 1)Acidity 2)Absorption of water from dentin during setting 3)Heat generated during setting 4)Poor marginal adaptation leads to bacterial penetration 5)Cytotoxicity of material. Pulp protection during operative dentistry treatment 8/28/2021 10
- 11. PULP PROTECTION PROCEDURES ďśThermal protection against temperature changes ďśElectrical protection against galvanic currents ďśMechanical protection during various restorative procedures ďśChemical protection from toxic components ďśProtection from microleakage interface between tooth and the restoration. Pulp protection during operative dentistry treatment 8/28/2021 11
- 12. Pulp Protection in Shallow and Moderate Carious Lesions⌠Pulp protection during operative dentistry treatment 8/28/2021 12 ďśIf hard dentin is present between carious lesion and the pulp and there is no threat to pulpal health after caries removal, give protective cement base and complete the permanent restoration as though it was a moderate lesion.
- 13. Pulp Protection in Shallow and Moderate Carious Lesions Pulp protection during operative dentistry treatment 8/28/2021 13 ďIn case of shallow cavities, if it is soft caries, complete removal should be done. ď After proper cavity preparation, ďbase should be applied, followed by desired restoration.
- 14. Pulp Protection in Deep Carious Lesions: ⢠In case of deep cavity, not extending to the pulp but reaching up to dentine, complete excavation of caries should be done first. ⢠Soft caries should be removed completely. ⢠Infected dentine should be removed completely. ⢠Affected dentine can be spared as it can help regenerating the secondary dentine. Pulp protection during operative dentistry treatment 8/28/2021 14
- 15. Pulp Protection in Deep Carious Lesions: ⢠After complete removal of the caries, calcium hydroxide should be placed, as it helps in the formation of secondary dentine. ⢠On top of calcium hydroxide, ⢠base should be applied. Then, ⢠The cavity should be filled with the desired restorative material. Pulp protection during operative dentistry treatment 8/28/2021 15
- 16. Two method 1) Indirect Pulp Capping 2) Direct pulp capping Pulp protection during operative dentistry treatment 8/28/2021 16
- 17. Indirect Pulp Capping Pulp protection during operative dentistry treatment 8/28/2021 17
- 18. Indications ďśDeep carious lesion near the pulp tissue but not involving it ďśNo mobility of tooth ďśNo history of spontaneous toothache ďśNo tenderness to percussion ďśNo radiographic evidence of pulp pathology ďśNo root resorption or radicular disease should be present radiographically. Pulp protection during operative dentistry treatment 8/28/2021 18
- 19. Contraindications ďśPresence of pulp exposure ďśRadiographic evidence of pulp pathology ďśHistory of spontaneous toothache ďśTooth sensitive to percussion ďśMobility present ďśRoot resorption or radicular disease is present radiographically. Pulp protection during operative dentistry treatment 8/28/2021 19
- 20. Direct Pulp Capping Pulp protection during operative dentistry treatment 8/28/2021 20 Within 6 week hard tissue will form
- 21. Indications ďśSmall mechanical exposure of pulp during Tooth preparation(<2mm) ďśTraumatic injury(<24h). ďśNo or minimal bleeding at the exposure site. Contraindications ďśWide pulp exposure ďśRadiographic evidence of pulp pathology ďśHistory of spontaneous pain ďśPresence of bleeding at exposure site Pulp protection during operative dentistry treatment 8/28/2021 21
- 22. MATERIALS USED FOR PULP PROTECTION Various materials are used to: ďśInsulate the pulp ďśProtect the pulp in case of deep carious lesion ďśAct as barriers to microleakage ďśPrevent bacteria and toxins from aďŹecting the pulp. Pulp protection during operative dentistry treatment 8/28/2021 22
- 23. They can be classified as following: 1) cavity sealers ďźVarnish ďźAdhesive sealer (Resin bonding agents) 2) Liners 3) Bases. ďSub-base under deep cavities (calcium hydroxide ) Pulp protection during operative dentistry treatment 8/28/2021 23
- 24. Varnish ⢠Varnish is an organic copal or resin gum suspended in solutions of ether or chloroform. ⢠When applied on the tooth surface the organic solvent evaporates leaving behind a protective film. ⢠Two coats of varnish are applied using a small cotton pellet for sufficient wetting of cavity walls. Pulp protection during operative dentistry treatment 8/28/2021 24
- 25. Advantages ďśIt is used to reduce microleakage ďśIn case of amalgam restoration, varnish improves sealing ability of amalgam ďśReduces postoperative sensitivity ďśPrevents discoloration of tooth by checking migration of ions into the dentin. Pulp protection during operative dentistry treatment 8/28/2021 25
- 26. Indications ⢠To seal the dentinal tubules ⢠To act as barrier to protect the tooth from chemical irritants from cements ⢠To reduce microleakage around restorations. Contraindications ⢠Under glass ionomers because varnish interferes chemical bonding of tooth and cements ⢠With restorative resins because varnish liners dissolve in monomer of the resin and it also interfere with the polymerization of resins. Pulp protection during operative dentistry treatment 8/28/2021 26
- 27. Resin Bonding Agents ⢠An adhesive sealer is commonly used under composite ⢠It helps in sealing and adhesion at the tooth restoration interface ⢠restorations. For application, cotton tip applicator is used to apply sealer on all areas of exposed dentin. Indications ⢠To seal dentinal tubules ⢠To treat dentin hypersensitivity. Pulp protection during operative dentistry treatment 8/28/2021 27
- 28. Liners ⢠Liners are typically ďŹuid materials that, because of their rheology, can adapt more readily to all aspects of a tooth preparation. ⢠They can be used to create a uniform, even surface that aids in adaptation of more viscous felling materials, such as amalgams or composites. ⢠Liners usually do not have sufficient thickness, hardness and strength to be used alone in the deep preparation. Pulp protection during operative dentistry treatment 8/28/2021 28
- 29. Indications ⢠To protect pulp from chemical irritants by sealing ability ⢠To stimulate formation of reparative dentin Materials ⢠Zinc oxide eugenol ⢠Calcium hydroxide ⢠Flowable composites ⢠Glass ionomer cements ⢠Light-cured resin-modifed glass ionomers (RMGIs). Pulp protection during operative dentistry treatment 8/28/2021 29
- 30. Bases ďśBases are used as pulp protective materials since they provide thermal insulation, encourage recovery of injured pulp form thermal, mechanical or chemical trauma, galvanic shock and microleakage. ďśBase is applied in an attempt to replace the lost dentin. ďśWhen cavity is deep, liner, base and varnish are applied to protect the pulp Pulp protection during operative dentistry treatment 8/28/2021 30
- 31. Classifcation ďśProtective bases: They protect the pulp before restoration is placed ďśSedative bases: They help in soothing the pulp which has been irritated by mechanical, chemical or other means ďśInsulating bases: They protect the tooth from thermal shock. Pulp protection during operative dentistry treatment 8/28/2021 31
- 32. Materials ďźPolycarboxylate cement (PCC) ďźGlass ionomer cement (GIC) ďźZinc oxide eugenol (ZOE) ďźZinc phosphate cement (ZPC) Pulp protection during operative dentistry treatment 8/28/2021 32
- 33. Sub-base under deep cavities(Ca (OH)2) ďśCalcium hydroxide has long been recognized as a valuable pulp capping material which facilitates the formation of reparative dentine ďśAfter certain period of time, the entire mass will disappear from under the restoration. ďśUse ďź As sub-base under deep cavities ďź As a base, especially under composite restorations ďź As an interim restoration Pulp protection during operative dentistry treatment 8/28/2021 33
- 34. Pulp protection in different situation Pulp protection during operative dentistry treatment 8/28/2021 34
- 35. i. Shallow preparation (âĽ1.5â2 mm of RDT) ďśIn a shallow tooth excavation (which includes âĽ1.5â2 mm of RDT), ďśpulpal protection, other than in terms of chemical protection, is not necessary. ďśFor an amalgam restoration, the preparation is coated with two thin coats of a varnish, ďśA single coat of a dentin sealer, or a dentin bonding system, and then restored. For a composite restoration, ďśThe preparation is treated with a bonding system (etched, primed, coated bonding agent) and then restored. Pulp protection during operative dentistry treatment 8/28/2021 35
- 36. ii. Moderately deep preparation (0.5â2.0 mm of RDT) ďśIn a moderately deep tooth excavation ďśfor amalgam that includes some extension of the preparation towards the pulp, so that a region includes less than ideal dentin protection, ďśit may be judicious to apply a base. ďź The commonly employed bases include resin modified glass ionomer cement (RMGIC), zinc polycarboxylate and zinc phosphate cement. ďśA sealer is then applied before placing a final amalgam restoration. ďśIn the case of a composite procedure, a bonding system is used. Pulp protection during operative dentistry treatment 8/28/2021 36
- 37. iii. Very deep preparation (iii. <iii. 0.5 mm of RDT) ⢠If extensive dentin is lost because of caries and the tooth excavation extends close to the pulp, a liner would be indicated. ⢠The ability of hard setting Calcium hydroxide material to stimulate the formation of reparative dentin makes it the material of choice to be employed as a Liner. ⢠An RMGIC base can then be placed over the calcium hydroxide liner. ⢠The final restorative material is thus placed over the underlying base and liner. Pulp protection during operative dentistry treatment 8/28/2021 37
- 38. Precautions to be Taken While Using Amalgam as a Restorative Material ⢠Use of varnish or dentin bonding agent at the margins of restoration if more than 2 mm of remaining dentin thickness is present. ⢠Use of liner or base under the silver amalgam restoration when remaining dentin thickness is 0.5 to 2 mm. ⢠Use of calcium hydroxide as sub-base (0.5-1 mm) covered with a base material in preparations with less than 0.5 mm remaining dentin thickness. Pulp protection during operative dentistry treatment 8/28/2021 38
- 39. Precautions to be Taken While Using Composite Resin as a Restorative Material ⢠Use of liner is advocated under composite restorations in deep preparations. ⢠Liners containing calcium hydroxide have shown to provide good protection against bacteria. ⢠Zinc oxide eugenol liners should not be used with composite resins since they interfere with polymerization of composites. Pulp protection during operative dentistry treatment 8/28/2021 39
- 40. METHODS OF PULP PROTECTION UNDER DIFFERENT RESTORATIONS When RDT >2mm(shallow) When RDT 0.5-2mm When RDT <0.5 For silver amalgam Varnish Base and varnish Calcium hydroxide, Liner base, and vanish required For composite resin Dentine bonding system RMGI base and Dentine bonding system Calcium hydroxide as Liner, RMGI base and, Dentine bonding system For GIC Not require Not require Calcium hydroxide as liner for cast gold restoration cement RMGI base and Cement(2mm thick) Calcium hydroxide as Liner, RMGI base, and Cement for ceramic restoration Dentine bonding system and Resin cement Dentine bonding system and Resin cement Calcium hydroxide as Liner, dentine bonding system and Resin cement Pulp protection during operative dentistry treatment 8/28/2021 40
- 41. Summery ⢠Excessive force should not be applied during insertion of restoration ⢠Restorative materials should be selected carefully, considering the physical and biological properties of the material ⢠Excessive heat production should be avoided while polishing procedures ⢠Avoid application of irritating chemicals to freshly cut dentin ⢠Use varnish or base before insertion of restoration ⢠Patent should be called on recall basis for periodic evaluation of status of the pulp. Pulp protection during operative dentistry treatment 8/28/2021 41
- 42. Reference ⢠Textbook_of_Operative_Dentistry_Nisha ⢠Sturdevantâs_Art_and_Science_of_Operative_Dentistry_Mosby;_5_edition ⢠Summitt's Fundamentals of Operative Dentistry ⢠Textbook_of_Preclinical_Conservative_Dentistry_by_Nisha_Garg__Amit_Garg Pulp protection during operative dentistry treatment 8/28/2021 42
- 43. THANK YOU FOR YOUR KIND ATTENTION
Editor's Notes
- Some important features of pulp are: ST / RL / SENSATIVE(1 to 2 sec after s+ go) Canât tolerate with edema/with no collateral circulation Odontoblasts (irritation dentin) Some important features of pulp are as follows Pulp is located deep within the tooth, so defes visualizaton It gives radiographic appearance as radiolucent line Pulp is a connectve tssue with several factors making it unique and altering its ability to respond to irritaton Normal pulp is a coherent sof tssue, dependent on its nor mal hard dentn shell for protecton and hence, once exposed, extremely sensitve to contact and te perature but this pain does not last for more than 1 to 2 seconds afer the stmulus removed Since pulp is totally surrounded by a hard tssue, dentn limits the area for expansion and restricts the pulpâs ability to toler ate edema The pulp has almost a total lack of collateral circulaton, which severely limits its ability to cope with bacteria, necrotc tssue and inďŹammaton The pulp possess unique cells the odontoblasts, as well as cells that can diďŹerentate into hard-tssue secretng cells that form more dentn and/or irritation dentin in an atempt to protect itself from injury.
- Various pulpal irritants can be : ⢠Bacterial irritants: Most common cause for pulpal irritation are bacteria or their products which may enter pulp through a break in dentin either from: â Caries â Accidental exposure â Fracture â Percolation around a restoration â Extension of infection from gingival sulcus â Periodontal pocket and abscess â Anachoresis (Process by which microorganisms get carried by the bloodstream from another source localize on inflamed tissue). ⢠Traumatic â Acute trauma like fracture, luxation or avulsion of tooth â Chronic trauma including parafunctional habits like bruxism. ⢠Iatrogenic: Various iatrogenic causes of pulpal damage can be: â Thermal changes generated by cutting procedures, during restorative procedures, bleaching of enamel, microleakage occurring along the restorations, electrosurgical procedures, laser beam, etc. can cause severe damage to the pulp, if not controlled. â Orthodontic movement â Periodontal curettage â Periapical curettage â Use of chemicals like temporary and permanent fillings, liners and bases and use of desiccants such as alcohol. ⢠Idiopathic â Aging â Resorptionâinternal or external
- The following defense reactions take place in a carious tooth to protect the pulp Formation of reparative dentin Dentinal sclerosis, i.e. reduction in permeability of dentin by narrowing of dentinal tubules Inflammatory and immunological reactions
- 1. Unnecessary application of excessive pressure on the dentin forming the base of a deep cavity; only gentle pressure must be employed either during the use of hand or rotary instruments, especially if this pressure is directed Pulp wards. Improper use of probes or instruments in the deep pulpal floor will transmit more mechanical pressure and might cause pulp exposure. 2. There is always an unavoidable degree of frictional heat resulting during cavity preparation. The ultimate goal of the clinician is to keep it within the physiological tolerance of the dentin-pulp organ i.e. within the limits of the TTZ (Thermal Tolerance Zone) of dentin which ranges between 85-132ÂşF (29-56o C). Thermal irritation during cavity preparation could be controlled by: ⢠Minimizing the frictional heat resulting during cavity preparation via: O Decreasing pressure, decreasing the area of cutting as well as the amount and time of cutting. O Using tools with high cutting efficiency. The tool should be sharp, of proper size and appropriate for the desired function. ⢠The use of coolants. Air-water spray jet is considered to be the most appropriate since the use of air drying only could desiccate the dentin while the use of water coolant only impairs the visibility during work. The coolant must fulfill the following requirements: o It must be copious in amount, with adequate rate. o It should be multidirectional, to produce an all-over cooling effect on the tooth. o It should be of the same temperature as that of the mouth i.e. 37ÂşC. Lower temperatures cause fogging, alters vision and may irritate the pulp. On the other hand, higher temperatures will not be that effective in cooling. Remaining dentin thickness (RDT) In human teeth, dentn is approximately 3 mm thick Dentn permeability increases with decreasing RDT RDT of 2 mm or more eďŹectvely precludes restoratve damage to the pulp At RDT of 0.75 mm, eďŹects of bacterial invasion are seen When RDT is 0.25 mm, odontoblastc cell death is seen ⢠Excessive cutting of enamel (width) since this will expose larger area of dentin. Increase in cavity width causes weakening of the remaining tooth structure and subjects it to more mechanical irritation. ⢠Overcutting of dentin (depth) and unnecessary deepening of the cavity. The deeper the cavity, the more the pulp will be irritated because the remaining protective dentin bridge will be decreased. ⢠Unnecessary application of excessive pressure on the dentin forming the base of a deep cavity; only gentle pressure must be employed either during the use of hand or rotary instruments, especially if this pressure is directed pulpwards. Improper use of probes or instruments in the deep pulpal floor will transmit more mechanical pressure and might cause pulp exposure. ⢠Cutting across the recessional lines of the pulp; the excavation of soft dentin must be carried out parallel to the pulp in scooping action and layer by layer. @A speed of 3,000 to 30,000 rpm without coolant can cause pulpal damage o Using tools with high cutting efficiency. The tool should be sharp, of proper size and appropriate for the desired function.
- l In case of deep cavity, not extending to the pulp but reaching up to dentine, complete excavation of caries should be done first. l Soft caries should be removed completely. l Infected dentine should be removed completely. l Affected dentine can be spared as it can help regenerating the secondary dentine. l After complete removal of the caries, calcium hydroxide should be placed, as it helps in the formation of secondary dentine. l On top of calcium hydroxide, base should be applied. l Then, the cavity should be filled with the desired restorative material. l In case of shallow cavities, if it is soft caries, complete removal should be done. l After proper cavity preparation, base should be applied, followed by desired restoration.
- Indications Deep carious lesion near the pulp tissue but not involving it No mobility of tooth No history of spontaneous toothache No tenderness to percussion No radiographic evidence of pulp pathology No root resorption or radicular disease should be present radiographically. Contraindications Presence of pulp exposure Radiographic evidence of pulp pathology History of spontaneous toothache Tooth sensitive to percussion Mobility present Root resorption or radicular disease is present radiographically.
- Indications Small mechanical exposure of pulp during ÂTooth preparation ÂTraumatic injury. No or minimal bleeding at the exposure site. Contraindications Wide pulp exposure Radiographic evidence of pulp pathology History of spontaneous pain Presence of bleeding at exposure site
- Sealer can be:  Varnish: A varnish is an organic gum or rosin suspended in organic solutions like ether or chloroform  Adhesive sealer: It helps in sealing and adhesion at the tooth restoration interface. For example, dentin bonding agent and resin luting cements. Liner: Liner is applied in thin layer of less than 0.5 mm so as to attain a physical barrier to pulp and to provide therapeutic eďŹect. Base: Base is applied in an attempt to replace the lost dentin and to provide thermal, physical and therapeutic advantages to the pulp NB:-Solution Liners(cavity selers) Both 1 and 2 chem protc Dentin sealer : used to decrease sensitivity through sealing dentinal tubule Bonding systems : helping composite to attached
- It is supplied in the form of a liquid composed of 10% natural gum (copal or resin) or synthetic resin dissolved in 90% organic solvent such as ether, acetone or chloroform. As each coat is dried, the solvent evaporates leaving a semipermeable thin resinous film that seals and protects the underlying structure.
- Function of varnish: 1. It forms a barrier against chemical irritation from the restorative material. 2. It seals dentinal tubules; thereby it reduces movement of dentinal fluid and subsequently decreases hypersensitivity. 3. It reduces the irregularities of the prepared surface thus improving the adaptation of the permanent restoration and decreases interfacial gaps. 4. It can provide electrical insulation. However, it is too thin and cannot provide thermal or mechanical insulation. 5. It is compatible with pulp-dentin organ, except if remaining dentin thickness is less than1 mm.
- not logical to use varnish under resin composite as it will prevent the mechanical interlocking of the resin into tooth structure. Chem x GIC and PCC as well as hinders the fluoride uptake from glass ionomer. Under amalgam restoration: It prevents penetration of metallic ions and corrosion products into dentinal tubules, thus preventing pulpal irritation and tooth discoloration (amalgam blues). It also decreases the initial microleakage space with amalgam. Under cast gold restoration: Used to seal tubules but it should be compatible with the utilized luting cement. Under acidic base material such as Zinc phosphate cement
- Cavity suspension liners: Unfortunately, the film thickness of these materials is insufficient to provide any thermal or electrical insulation
- Cement Liners: (100- 500Îźm) N.B: 1-There are two important aspects of pulpal medication; relief of pulpal inflammation and facilitating of dentinal bridging for physiologic protection. 2- Eugenol and calcium hydroxide are commonly used to provide these functions. 3-Newer liners as GIC and RMGIC place less emphasis on pulpal medication and focus more on chemical protection by sealing and mechanical protection. 4- All cement liners and bases have some degree of solubility in oral fluids. Thus, they should be placed only on dentin and completely removed from cavity walls and margins.
- Cement base(500- 2000Îźm is equal .5 - 2 mm) to substitute lost dentin and provide thermal and mechanical protection. Types of bases: 1. Resinous Hard-setting Calcium hydroxide (Ca (OH)2) 2. Reinforced Zinc oxide and eugenol (RZO/E) 3. Zinc phosphate cement (ZPC) 4. Zinc polycarboxylate (PCC) 5. Glass ionomer (GIC) 6. Resin modified glass ionomer cement (RMGIC)
- Zinc Oxide Eugenol It provides excellent sealing qualities and is bacteriostatic in nature. Zinc oxide eugenol is used as intermediatory base. Zinc oxide eugenol cement has anodyne eďŹect, in other words it is helpful for relieving toothaches in case of deep preparations because of its sedative action. Zinc oxide eugenol cement should not be used with composite resins as it inhibits the polymerization of the resin. Zinc Phosphate Cement A thick creamy mix of zinc phosphate cement is used as base to reduce the thermal conductivity of metallic restorations and to block the undercuts in the preparation wall in case of cast restorations. Tick mixes should be used to minimize pulp irritation and marginal leakage. Te thickness of the cement to provide eďŹective thermal insulation should be at least between 0.50 to 1.0 mm. Te cement should not cover on enamel wall or contact the cavosurface margin. If required, shape the cement with slow speed fssure bur or sharp explorer. Polycarboxylate Cement (Fig. 14.23) Zinc polycarboxylate cement contains modifed zinc oxide powder and an aqueous solution of polyacrylic acid. It chemically bonds to enamel and dentin and has antibacterial properties. Polycarboxylate cement is well tolerated by the pulp. Varnish should not be used with polycarboxylate cement because it would neutralize the adhesion potential of the cement Glass Ionomer Cement Glass ionomer cements possess anticariogenic properties because of continuous release of ďŹuoride throughout the life of restoration. Also these cements can bind to both enamel and dentin of the tooth via chemical bonding. Tey are also well tolerated by the pulp.
- Properties and indications of calcium hydroxide: Ca (OH)2 is applied for pulpal medication when the remaining dentin bridge is â¤0.5mm (indirect pulp capping) or in direct contact with the exposed pulp tissue (direct pulp capping). It will stimulate odontoblasts to form reparative dentin and form calcific bridging at the exposure site. It also relieves pulpal inflammation. This is owed to calcium ion concentration, alkalinity and antibacterial potential of this cement. It is thus used in direct and indirect pulp capping. It is porous and soluble; therefore it is neither an electric insulator nor a chemical insulator. However, its alkalinity has a neutralizing effect on acids of subsequently placed bases or restorative materials. Conventional formulations used as liners are too thin to provide thermal insulation. On the other hand, resinous hard-setting formulations have excellent handling characteristics and can be built up to the thickness required for thermal insulation. These formulations are strong enough to withstand condensation forces, but since they degrade over time, they can no longer provide mechanical support for the restoration. Hard-setting formulations rely on resin matrices and this makes the release of Ca and OH ions much more difficult. It is compatible with pulp-dentin organ, base materials and all restorative materials. It has no effect on the setting reaction or properties of any base or restorative material.
- Zinc oxide and eugenol (ZO/E and RZO/E) Form and Composition: It is supplied in the form of a powder of zinc oxide and a liquid of 85% eugenol or clove oil. Polymers are also added to increase the strength and homogeneity of the mix, and to decrease the flow and solubility. Fillers such as silica or alumina may also be added to increase the strength. In the modified formulations as RZO/E, substitution of a portion of eugenol with ethoxy benzoic acid results in an appreciable increase in strength, yet the solubility is dramatically decreased. The setting reaction is a chelation reaction, where eugenol chelates zinc producing zinc eugonolate (or zinc benzoate in RZO/E) and water as a byproduct Function of zinc oxide and eugenol: 1. It has multiple pharmacological actions. Eugenol produces palliative, sedative and obtundant action on the pulp. ZO/E also has an antiseptic and anti-inflammatory effect. It is thus used to alleviate discomfort resulting from mild-to-moderate pulpal inflammation. 2. ZO/E can be placed in moderately deep cavities, when remaining dentin thickness is as low as 1mm. However, RZO/E can have irritating action on pulp tissues at this depth. 3. It is an excellent thermal insulator in a film thickness as low as 0.25mm. 4. It is an excellent electrical insulator and has a good sealing ability. 5. ZOE has low strength properties, not rigid enough to be used as a base. Despite improved strength properties of RZO/E, it is still inferior to that of other cements.
- Clinical Note i. The ability of calcium hydroxide to stimulate the formation of reparative dentin, when it is in contact with pulpal tissue makes it the typical material of choice for application to very deep excavations. ii. RMGIC is recommended as the base of choice for most restorations including amalgam. iii. The earlier clinically recommended bases included zinc phosphate and zinc polycarboxylate cement. Between these two choices, the more appropriate base is zinc polycarboxylate. This cement is less irritating to the pulp compared to zinc phosphate due to the following reasons: a. The polyacrylic acid has a high molecular weight and hence, cannot diffuse into the pulp and cause irritation. This is because the diameter of the acid particles is greater than the diameter of the dentinal tubules. b. The powder neutralizes the acidic pH of the acid rapidly compared to zinc phosphate.
- Effects of Amalgam on Pulp Mild-to-moderate inďŹammation in deep caries Harmful eďŹects due to corrosion products Inhibition of reparative dentin formation due to damage to odontoblasts Copper in high copper alloy is toxic High mercury content exerts cytotoxic eďŹects on pulp Postoperative thermal sensitivity due to high thermal conductivity Defense mechanism of the pulp Tubular sclerosis Smear layer Reparative dentin formation Healthy reparative reaction Unhealthy reparative reaction Destructive reaction.
- Summery Prevention of pulpal damage due to operative procedure To preserve the integrity of the pulp, the dentist should observe certain precautions while rendering treatment: Excessive force should not be applied during insertion of restoration Restorative materials should be selected carefully, considering the physical and biological properties of the material Excessive heat production should be avoided while polishing procedures Avoid application of irritating chemicals to freshly cut dentin Use varnish or base before insertion of restoration Patent should be called on recall basis for periodic evaluation of status of the pulp.