Pathway 14-6 Pulp Reactions to Restorative Procedures

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Questions and Answers

Why is the cumulative effect of pulp insults important in dentistry?

It indicates a need for more invasive restorative procedures.

It shows that pulp vitality can be enhanced through repeated treatments.

It allows for quicker healing of the dental pulp.

It demonstrates that pulp has diminished capacity to remain vital with successive irritations. (correct)

What was the mean observation period for patients treated with single unit metal-ceramic crowns in the mentioned study?

15 years

12 years

13.5 years

14 years (correct)

What is the consequence of an intrapulpal temperature rise of 10°C during restorative procedures?

It has no effect on the dental pulp whatsoever.

It leads to the formation of reactionary dentin immediately.

It may cause irreversible pulp pathosis in a significant percentage of teeth. (correct)

It always results in pulp necrosis.

During cavity preparation, what is a significant effect of desiccation on the pulp?

It causes significant aspiration of odontoblastic nuclei into dentinal tubules. Signup and view all the answers

What happens to the pulp when desiccated for just 30 seconds according to SOME studies?

It causes necrosis in areas corresponding to drying. Signup and view all the answers

Which chemical agent has been proposed to disinfect cavities during preparation, but may exert toxic effects?

Hydrogen peroxide Signup and view all the answers

What was observed when the pulp was exposed to the oral environment for longer than 24 hours?

A bacterial biofilm may form, complicating immune response. Signup and view all the answers

What factor was found to be the most significant in pulp injury following cavity preparations?

Remaining dentin thickness (RDT) Signup and view all the answers

What relationship was observed between postoperative sensitivity and cavity depth?

Sensitivity is related to cavity depth but not to liners Signup and view all the answers

How does the density of dentinal tubules change as they approach the pulp?

It increases and density is higher near the pulp Signup and view all the answers

What was the average rate of secondary dentin deposition following restorative procedures according to the primate model study?

2.9 um per day Signup and view all the answers

What contributes to the reduction of PBF with age according to the findings?

Decreased response to cold application Signup and view all the answers

How does the presence of dental caries affect dentin permeability?

It decreases permeability in dentin subjacent to the carious lesion Signup and view all the answers

Which statement accurately describes the relationship between the diameter of dentinal tubules and their location within a tooth?

Diameter increases towards the pulp Signup and view all the answers

Which factor is NOT associated with an increase in pulp response as patients age?

Increased expression of differentiation-related biological factors Signup and view all the answers

According to the study of PRIMATES that has now been disproved, what percentage of teeth experienced irreversible pulp pathosis when the intrapulpal temperature rose by 10°C?

15% Signup and view all the answers

In the study where pulp abscess formation was observed, what percentage of teeth were affected when the intrapulpal temperature increased by 20°C?

60% Signup and view all the answers

How long did the pulp respond favorably to exposures in the study evaluating pulp capping procedures?

Up to 24 hours Signup and view all the answers

In the study using gradual controlled heat application, what was the approximate increase in intrapulpal temperature that did not show any clinical or histological changes after 2-3 months?

11°C Signup and view all the answers

How long did continuous air drying of class V cavities in human molars cause significant displacement of odontoblastic nuclei and pulp inflammation?

30 seconds Signup and view all the answers

Within how many days was there autolysis of aspirated cells and formation of reactionary dentin following desiccation? In other words, how long does it take for the dentin pulp to recover from Desiccation?

7 to 30 days Signup and view all the answers

⭐️What is the estimated range of shrinkage for resins during polymerization?

0.6% to 1.4% Signup and view all the answers

At what temperature did heat increase in rat pulp tissue raise heat shock protein-70 and cause changes in alkaline phosphatase and gap junction proteins?

42°C Signup and view all the answers

How far from the pulp did the cavity floor need to be for areas of coagulation necrosis to be seen in the study on heat application in deep cavity preparations?

Less than 0.5 mm Signup and view all the answers

For how long did patients remain asymptomatic in the study on heat application in deep cavity preparations?

1 month Signup and view all the answers

What temperature increase is linked to pulp abscess formation in 60% of teeth?

20°C Signup and view all the answers

Which of the following temperature increases could possibly cause pulp abscess formation in PRIMATES, according to the findings?

20°C Signup and view all the answers

Study Notes

Pulp Reactions to Restorative Procedures

Restorative procedures aim to treat dental caries, restore missing teeth, correct anomalies, and address fractures/failures.
Maintaining pulp vitality during restorative procedures requires a pre-existing diagnosis of reversible pulpitis.
Minimally traumatic procedures are preferred to avoid converting reversible pulpitis to irreversible pulpitis.
Irreversible pulpitis can be symptomatic or asymptomatic, potentially leading to pulp death.
The cumulative effect of restorative procedures, caries, and microleakage on pulp vitality is significant.
The pulp's ability to withstand irritation diminishes with each successive insult.
A study evaluating the pulp fate under metalceramic crowns and bridge abutments found a higher percentage of pulp necrosis (32.5%) in bridge retainer groups compared to single unit crowns (15.6%).
Anterior teeth serving as bridge abutments exhibited a significantly higher necrosis rate (54.5%).
The influence of dental procedures on pulp vitality depends on factors such as:
- Procedure type: Bridge abutments have a higher risk of pulp necrosis than single unit crowns.
- Tooth location: Anterior teeth used as bridge abutments are more susceptible to pulp necrosis.
- Procedure extent: Deeper procedures and larger restorations can increase the risk of pulp damage.
- Material used: Some materials may be more biocompatible than others.
- Patient factors: Age, overall health, and pre-existing conditions can influence the pulp's response.

Degree of Pulp Inflammation Preoperatively

Inflamed pulp is less responsive to irritation due to limited space and lack of collateral circulation
Most research on restorative procedures uses teeth with healthy pulp
Animal studies use anesthesia, which decreases pulp blood flow (PBF)
Findings may not reflect real-world scenarios with inflamed pulp and local anesthetics
Pulp responds well to capping procedures within 24 hours of exposure, but not after extended periods
Prolonged exposure allows bacterial biofilm formation, which is difficult to fight
Aseptic mechanical exposures or brief traumatic injuries often result in favorable pulp response to VPT procedures
Standardized inflammation models for chronic caries are not commonly used to assess effects of dental procedures
Older studies show unfavorable outcomes for capping carious exposures, while newer studies using tricalcium silicates demonstrate more favorable results
In the absence of severe symptoms or exposure, the degree of preoperative pulp inflammation is difficult to assess
Minimize irritation during restorative procedures to prevent irreversible pulp inflammation
Advise patients about potential pulp degeneration and importance of follow-up

Amount of Physical Irritation During Procedures

Heat from restorative procedures can cause significant pulp temperature increases
10°C increase may cause irreversible pulp pathosis, while a 20°C rise can lead to pulp abscess formation (primate models)
Older studies reported burns and inflammation without coolants
More recent studies show that controlled gradual heat application over a large area may not cause clinical or histological changes
Heat increase in rat pulp tissue to 42°C activates heat shock proteins, which are protective
Deep cavity preparation causes histological changes depending on proximity to pulp
Desiccation during cavity preparation can aspirate odontoblastic nuclei into dentinal tubules, leading to inflammation and necrosis
Effects of desiccation are usually temporary, with autolysis of aspirated cells and reactionary dentin formation
Sensitivity is restored with rehydration and can be increased by microbial contamination
Air cooling during crown and bridge preparations may cause minimal pulp damage

Biological and Chemical Irritation

Caries bacteria constantly irritate pulp, even in early stages
Cavity preparation may leave residual contamination despite caries removal
Rubber dams and water irrigation prevent contamination during preparation
Cavity disinfection with chemicals like hydrogen peroxide or sodium hypochlorite is debated due to toxicity concerns
Adequate restorations minimize significance of residual bacteria
Outward flow of dentinal fluid limits inward flow of noxious agents, reducing irritation
Etching agents, especially those used for total dentin etch, can irritate pulp
Superficial cavities sealed with resin may not be affected by dentin etching due to narrow tubules and low density in peripheral dentin
Etching with phosphoric acid may reduce bacterial presence and inflammation
Self-etching systems are growing in popularity, but their bond strength and effectiveness compare to total-etch systems
Bacterial leakage, regardless of the etching system, is the most significant factor affecting pulp inflammation
Unpolymerized monomers in resin may inhibit immune cells and cause chemical irritation
Polymerization shrinkage can create internal stresses on dentin and voids leading to microleakage
Salivary or dentin-based metalloproteinases or salivary esterases can degrade the hybrid layer, compromising bond strength
Chlorhexidine, galardin, benzalkonium chloride, or quaternary ammonium methacrylates can help maintain the hybrid layer stability

Conclusion

Chemicals used in modern restorative procedures can irritate pulp:
- Direct pulp exposure
- Microbial leakage at tooth-restoration interface
- Degradation of the hybrid layer sealing the restoration-dentin interface

Proximity of Restorative Procedures to Dental Pulp and Dentin Surface Area

Depth of the carious lesion significantly affects the pulp's reaction.
As the lesion progresses towards the pulp, especially when the Remaining Dentin Thickness (RDT) is less than 0.5 mm, the pulp is more likely to experience irreversible damage.
The diameter and density of dentinal tubules increase closer to the pulp.
Dentin tubule density at the DEJ (dentinoenamel junction) is approximately 65,000/mm2, while at the pulp, it is about 15,000/mm2.
The area occupied by tubule lumina at the DEJ is estimated to be 1% of the total surface area at the DEJ and 22% at the pulp.
Research shows that pulp inflammation in response to restorative procedures increases with the reduction in RDT.
RDT is a crucial factor in pulp injury, even after considering preparation methods, coolants, drill speed, conditioning with EDTA, and filling materials.
Over time after cavity preparation, the permeability of RDT decreases due to reactionary dentin deposition, protein migration into tubules, and dentin sclerosis.
Secondary dentin deposition occurs at a rate of 0.8mm/day but increases to an average of 2.9mm/day after restorative procedures.
Interestingly, dentin deposition is faster next to shallow cavities compared to deep cavities.
The total amount of reactionary dentin deposited is thicker in deeper and wider cavities.

Postoperative Sensitivity and Crown Preparations

Postoperative sensitivity is common following restorative procedures.
Postoperative sensitivity in resin composite restorations is linked to cavity depth, not the presence or absence of liners or bases.
Crown preparations expose more dentinal tubules to irritation, due to their greater size and the added irritation from preparation, impression techniques, and temporary restorations.
Reducing coolant during crown preparation, especially during finalizing finishing lines, can dramatically reduce Pulpal Blood Flow (PBF) in animal models.
Air coolant appears to be a suitable alternative to traditional water coolant.
Long-term outcomes reveal that pulp necrosis following crown placement ranges from 10% to 50%.

Dentin Permeability and the Odontoblastic Layer

Dentin permeability plays a critical role in the ingress of irritants to the pulp.
Dentin permeability is not uniform and varies based on location, patient age, and the presence of conditions like dental caries.
Tubular diameter increases from approximately 0.6 to 0.8mm near the DEJ to around 3mm at the pulp.
Deep cavity preparations, especially when employing total-etch procedures, allow bacteria to migrate through remaining dentin into the pulp.
Aging increases the width of peritubular dentin, reducing the tubular lumen or causing sclerosis.
Caries demineralizes superficial dentin but also causes remineralization and the formation of caries crystals within the tubules of inner dentin, reducing permeability—potentially a protective mechanism against caries progression.
Cavity preparation increases the permeability of the odontoblastic cell layer only at the site of preparation.
The odontoblastic layer acts as a physical barrier, produces reactionary or reparative dentin, and contributes to the host response by expressing inflammatory mediators and recognizing bacteria.

Age and Pulp Response

Resting PBF and changes in PBF in response to cold application decrease with age.
Aging might be associated with a reduction in pulp neuropeptides.
Studies show no significant differences between young and old pulp in odontoblast-like cell regeneration, or in the presence of cells expressing class II MHC, heat shock protein 25, or nestin, after cavity preparation.
Young pulp exhibits higher expression of biological factors related to cell differentiation, proliferation, and immune responses, while older pulp shows an increase in factors related to apoptosis.
PBF in anterior teeth is correlated with systolic blood pressure but not age, sex, or tooth type.
It remains unclear how the pulp's ability to cope with external stimulation or irritation changes with aging.

Pulp Temperature Increase

An increase in pulp temperature of 10°C causes irreversible pulp pathosis in 15% of teeth.
A 20°C increase in pulp temperature leads to pulp abscess formation in 60% of teeth.

Pulp Capping Procedures

Pulp responds favorably to exposures of up to 24 hours after exposure.

Controlled Heat Application

An 11°C increase in intrapulpal temperature followed by 2-3 months of evaluation showed no clinical or histological changes in the pulp.

Air Drying

30 seconds of continuous air drying of class V cavities in human molars causes significant displacement of odontoblastic nuclei, pulp inflammation, and even areas of necrosis.
Desiccation effects are transient, with autolysis of aspirated cells and the formation of reactionary dentin within 7 to 30 days.

Resins

Resin shrinkage during polymerization is estimated to range from 0.6% to 1.4%.

Heat Shock Protein-70

A heat increase in rat pulp tissue to 42°C raises heat shock protein-70, known for its tissue protection, causing changes in alkaline phosphatase and gap junction proteins.

Deep Cavity Preparations

In deep cavity preparations where the cavity floor is less than 0.5 mm from the pulp, areas of coagulation necrosis can be observed.
Patients remained asymptomatic for one month after deep cavity preparations.

Pulp Abscess Formation

A 20°C rise in temperature can cause pulp abscess formation in 60% of teeth

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