Published on March 8, 2014
Pulp Protection Dr. Hakan ÇOLAK DDS, PhD Department of Restorative Dentistry Ishık University School of Dentistry
INTRODUCTION • By definition, pulp is a soft tissue of mesenchymal origin residing within the pulp chamber and root canals of teeth.
PULPAL IRRITANTS • Various pulpal irritants can be : – Bacterial irritants • • • • Caries Accidental exposure Fracture Percolation (filtration of a liquid through a porous substance) around a restoration • Extension of infection from gingival sulcus • Periodontal pocket and abscess
SEM of the interproximal surface of an amalgam restoration showing a marginal gap between the amalgam (A) and the tooth (T) at cervical margin. Photo by Dr. Jorge Perdigao.
Bacteria from caries resulting in pulpal irritation
PULPAL IRRITANTS (con’t) • Traumatic – Acute trauma like fracture, luxation or avulsion of tooth – Chronic trauma including parafunctional habits like bruxism • Idiopathic – Aging – Resorption: Internal or external.
PULPAL IRRITANTS (con’t) • Iatrogenic: Various iatrogenic causes of pulpal damage can be: – 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 – Orthodontic movement – Periodontal curettage – Periapical curettage – Use of chemicals like temporary and permanent fillings, liners and bases and use of desiccants such as alcohol.
EFFECT OF DENTAL CARIES ON PULP • Dental caries is the most common route for causing irritation to the pulp • 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.
The rate of reparative dentin formation is related to rate of carious attack More reparative dentin is formed in response to slow chronic caries than acute caries.
Caries in the infundibulum of the second upper premolar tooth in the horse C = cement (light brown), D1 = primary dentin (white/yellowish), D2 = secondary dentin overlying pulp horn (dark brown). * = enamel (visible as a winding ridge). I = infundibulum, (A cone shaped invagination from the occlusal surface of the tooth. The invagination is lined with enamel and filled with cementum (C) to different degrees).8 Lundström et al. Acta Veterinaria Scandinavica 2007 49:10 doi:10.1186/1751-0147-49-10
Dark Sclerotic Dentin
Minimal mesial caries, picked up well on radiograph
EFFECT OF TOOTH PREPARATION ON PULP • Factors affecting response of pulp to tooth preparation – Pressure – Heat – Vibration – Remaining dentin thickness – Speed – Nature of cutting instruments
EFFECT OF TOOTH PREPARATION ON PULP • Pressure – The pressure of instrumentation on exposed dentin characteristically causes the aspiration of the nuclei of the odontoblasts or the entire odontoblasts themselves or nerve endings from pulp tissues into the dentinal tubules. – This will obviously stimulate odontoblasts, disturb their metabolism and may lead to their complete degeneration and disintegration. – This can occur by excessive pressure of hand or rotary instruments, especially in decreased effective depths.
The effects of repetitive hydrostatic pressure stimulation of dentine on the structure of dentine and pulp
EFFECT OF TOOTH PREPARATION ON PULP • Heat Production – RPM • more the RPM more is the heat production. • In deep penetrations of dentin without using coolants, e.g. pin holes, the cutting speed must not exceed 3,000 rpm – Pressure • It is directly proportional to heat generation. • Whenever, the RPMs are increased, pressure must be correspondingly reduced
EFFECT OF TOOTH PREPARATION ON PULP • Heat Production (con’t) – Surface area of contact: • It is related to the size and shape of the revolving tool. • The more the contact between the tooth structure and revolving tool, the more is the heat generation
EFFECT OF TOOTH PREPARATION ON PULP • Vibration – can create microcracks in enamel and dentin. • Remaining Dentin Thickness
EFFECT OF TOOTH PREPARATION ON PULP • Nature of Cutting Instrument – Use of worn off and dull instruments should be avoided. – Damaged cutting edges cause vibration and reduced cutting efficiency. – Use of dull instruments encourages the dentist to use excessive operating pressure, which results in increased temperature. This can result in thermal injury to pulp.
EFFECT OF CHEMICAL IRRITANTS ON PULP • The pulp is subjected frequently to chemical irritation from materials generally used in dentistry. • Various filling materials produce some irritation ranging from mild-to-severe, as do various medicaments used for desensitization or dehydration of the dentin
EFFECT OF CHEMICAL IRRITANTS ON PULP • Factors influencing the effect of restorative materials on pulp – Acidity – Absorption of water from dentin during setting – Heat generated during setting – Poor marginal adaptation leads to bacterial penetration – Cytotoxicity of material
PULP PROTECTION PROCEDURES • Pulp needs protection against various irritants as following ; – Thermal protection against temperature changes – Electrical protection against galvanic currents – Mechanical protection during various restorative procedures – Chemical protection from toxic components – Protection from microleakage interface between tooth and the restoration
A preoperative occlusal view of tooth No. 12. Recurrent decay and marginal leakage existed, requiring that the defective restoration be replaced.
Need of pulp protection from various irritants
Indirect Pulp Capping • Indirect pulp capping is a procedure performed in a tooth with deep carious lesion adjacent to the pulp • In this procedure, all the carious tissue is removed except – the soft undiscolored carious dentin which lies adjacent to the pulp. – Caries near the pulp is left in place to avoid pulp exposure and preparation is covered with a biocompatible material
Indirect Pulp Capping
Direct Pulp Capping • Direct pulp capping procedure involves the placement of biocompatible material over the site of pulp exposure to maintain vitality and promote healing
Direct Pulp Capping
MATERIALS USED FOR PULP PROTECTION • Various materials are used to: – Insulate the pulp – Protect the pulp in case of deep carious lesion – Act as barriers to microleakage – Prevent bacteria and toxins from affecting the pulp
Varnish • A varnish is an organic copal or resin gum suspended in solutions of ether or chloroform • When pplied on the tooth surface the organic solvent evaporates leaving behind a protective film
Liners • Liners are typically fluid materials that, because of their rheology,(study of flow characteristics) 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 filling materials such as amalgams or composites.
Liners • Indications of use of liners – To protect pulp from chemical irritants by sealing ability – To stimulate formation of reparative dentin.
Liners • Following materials are most commonly used as liner – Zinc oxide eugenol liners – Calcium hydroxide – Flowable composites – Glass ionomers
Liners • Calcium hydroxide
Calcium hydroxide has been used as liner in deep preparations because of its following features:
Liners • Calcium hydroxide – Limitations: • It has low strength, high solubility thus when it is exposed to the oral environment (e.g. due to leakage) it dissolves. This limits its use over only small areas requiring pulp protection.
Liners • Flowable composites – Flowable composites are the composites with a lower amount of filler. – This reduced filler content allows more fluid consistency, less strength and lower modulus than fully filled composites
Liners • Flowable composites – Advantages of using flowable composites as liners: – Adaptation to preparation walls because of their flow – Placement ease since the materials are injected directly into the preparation – Esthetic – Consistency
Liners • Glass ionomer cements (GIC): – Glass ionomer (GI) or resin modified glass ionomer (RMGI) liners have been used as a renewable source of fluoride under restorations which has been shown to reduce the incidence of caries.
Glass ionomer and light cured resin modified glass ionomer cement
Bases • Bases are used as pulp protective materials since they provide thermal insulation, encourage recovery of injured pulp from thermal, mechanical or chemical trauma, galvanic shock and microleakage • Bases should have sufficient strength so as to withstand forces of mastication and condensation of permanent restorations
Zinc Oxide Eugenol • The main components are zinc oxide and eugenol. • It has a pH of approximately 7 and is reported to have a sedative effect on the pulp • In high concentrations eugenol can be toxic • it does not adhere to tooth structure
Zinc Oxide Eugenol The setting of ZOE is due to hydrolysis of the zinc oxide followed by a reaction between the resulting zinc hydroxide and the eugenol. The reaction needs water to begin (water is also a product of the reaction), and explains why the reaction is faster in the presence of moisture
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