Pulp Capping Techniques and Materials
- Direct Pulp Capping: used when there is a pulpal exposure due to caries or accidental exposure during caries removal. Feasible if exposure is through non-infected dentin and there is no recent history of spontaneous pain. Tooth is isolated using a dental dam, and a protective material is placed over the exposure, followed by a dental restoration for a bacteria-tight seal.
- Stepwise Caries Excavation Technique: used when most of the decay has been removed from a deep cavity, but some softened dentin and decay remains over the pulp chamber. Leaves the softened dentin/decay in place and uses a layer of protective temporary material to promote remineralization. Cavity is re-opened after about 6 months to remove any residual softened dentin and place a permanent filling.
- Preferred materials for pulp capping are calcium hydroxide and mineral trioxide aggregate (MTA). Zinc oxide eugenol (ZOE) is controversial due to its cytotoxicity and non-adhesive nature. Glass ionomer (GI) and resin modified glass ionomer (RMGIC) are used as lining or base materials, but not preferred for direct pulp capping. Adhesive systems have shown unfavorable results due to vasodilating properties, chronic inflammation, and toxicity to pulp cells.
Benefits and Considerations of Calcium Hydroxide Cement
- Calcium hydroxide cement has high antimicrobial activity, reducing viable bacteria by 64-100%.
- Creates an alkaline environment that stimulates dentin regeneration.
- Releases growth factors and bioactive molecules from dentine matrix, inducing formation of dentin bridges.
- Disadvantages include low compressive strength and lack of adhesive properties.
- Requires a stronger separate lining material before placing the final restorative material.
- Pulp capping is not always successful in maintaining pulp vitality.
- Difficulty in estimating the rapidity of carious process and knowing when to stop excavating to avoid pulp exposure.
- Proper isolation techniques, such as dental dam, are important to prevent contamination during the procedure.
Mineral Trioxide Aggregate (MTA)
- Developed in the 1990s as a root canal sealer and direct pulp capping material.
- Comprises a blend of tricalcium silicate, dicalcium silicate, and tricalcium aluminate. Bismuth oxide is added for radiopaque properties.
- Produces CaOH as a hydration product and maintains an extended duration of high pH.
Success Rates of Pulp Capping Procedures
- Indirect pulp capping with bioactive tricalcium silicate and light-activated calcium hydroxide had success rates of 98.3% and 95% respectively.
- Clinical success rates of indirect pulp capping with calcium silicate cement and glass ionomer cement were 83.3%.
- Varying success rates of 73%-93% were found for indirect pulp capping with medical Portland cement, MTA, and calcium hydroxide.
- Direct pulp capping with ProRoot MTA had a success rate of 92.6%.
- Mature permanent teeth had success rates of 84.6% using MTA and 92.3% using Biodentine for direct pulp capping.
Hydration Products and Solubility of MTA
- The hydration products of MTA have been characterised in studies. MTA forms a calcium silicate hydrate gel when it comes into contact with moisture. The gel forms a hard, mineralised barrier that helps protect the pulp.
- MTA has low solubility, contributing to its long-term stability and sealing ability. Factors such as pH and temperature can influence its solubility.
- MTA has been compared to other materials for pulp capping and has shown superior properties compared to calcium hydroxide. It has better sealing ability and dentin bridge formation. It has also shown comparable or better results compared to materials like biodentine.
- Clinical trials have shown high success rates for MTA in pulp capping procedures. It has a high rate of clinical success in both primary and permanent teeth. Long-term follow-up studies have confirmed its durability as a pulp capping material.
Pulp capping is a technique used in dental restorations to prevent the dental pulp from necrosis, after being exposed, or nearly exposed during a cavity preparation, from a traumatic injury, or by a deep cavity that reaches the center of the tooth causing the pulp to die. When dental caries is removed from a tooth, all or most of the infected and softened enamel and dentin are removed. This can lead to the pulp of the tooth either being exposed or nearly exposed which causes pulpitis (inflammation). Pulpitis, in turn, can become irreversible, leading to pain and pulp necrosis, and necessitating either root canal treatment or extraction. The ultimate goal of pulp capping or stepwise caries removal is to protect a healthy dental pulp and avoid the need for root canal therapy.
To prevent the pulp from deteriorating when a dental restoration gets near the pulp, the dentist will place a small amount of a sedative dressing, such as calcium hydroxide or MTA. These materials, protect the pulp from noxious agents (heat, cold, bacteria) and stimulate the cell-rich zone of the pulp to lay down a bridge of reparative dentin. Dentin formation usually starts within 30 days of the pulp capping (there can be a delay in onset of dentin formation if the odontoblasts of the pulp are injured during cavity removal) and is largely completed by 130 days.
Two different types of pulp cap are distinguished. In direct pulp capping, the protective dressing is placed directly over an exposed pulp; and in indirect pulp capping, a thin layer of softened dentin, that if removed would expose the pulp, is left in place and the protective dressing is placed on top. A direct pulp cap is a one-stage procedure, whereas a stepwise caries removal is a two-stage procedure over about six months.
