pulpal reaction to cavity and crown

PULPAL REACTION TO PULPAL REACTION TO CAVITY AND CROWNCAVITY AND CROWN

PREPARATIONPREPARATION

DR. BAHJAT ABU HAMDAN DR. BAHJAT ABU HAMDANCONSULTANT PROSTHODONTISTCONSULTANT PROSTHODONTIST

DDS, CES, DSODDS, CES, DSO

PULPAL REACTION TO PULPAL REACTION TO CAVITY AND CROWNCAVITY AND CROWN

PREPARATIONPREPARATION

DR. BAHJAT ABU HAMDAN DR. BAHJAT ABU HAMDANCONSULTANT PROSTHODONTISTCONSULTANT PROSTHODONTIST

DDS, CES, DSODDS, CES, DSO

Pulpal Reaction to C.. and C.. PrepPulpal Reaction to C.. and C.. Prep

1. Introduction . 2. Thermal injury . 3. Transection of the Odontoblastic Processes and its

Implication in the Dentin and Pulp Complex . 4. Crown Preparation . 5. Vibratory Phenomenon . 6. Desiccation of Dentin . 7. Pulp Exposure . 8. Smear Layer .

Pulpal Reaction to C.. And C.. PrepPulpal Reaction to C.. And C.. Prep

9. Remaining Dentin Thickness . 10. Acid Etching . 11. Immunodefense of the pulp to Tooth Preparation . 12. Comparison of Cavity Preparation by High-Speed

Handpiece and Bur and Er:YAG Laser . 13. Pin Insertion . 14. Pulp Horn Extension . 15. Prevention of pulp injury.

1. Introduction1. Introduction

The vital pulp tissues are the best filling for the root canal. (Marmasse) .

These tissues have the following advantages: a: Play a role of a warning system. b: They form a protection and defense system . c: They give the indication of sound periapical tissues

. d: They play an important role in the formation of

normal root (apexigenesis). e . A vital tooth has normal esthetic appearance.

1. Introduction .1. Introduction .

Of the various forms of treatment, operative procedures are the most frequent cause of pulpal injury .

Trauma to the pulp can’t always be avoided, particularly with extensive restorations .

A competent clinician, recognizing the hazards associated with each step of the restorative process, can often minimize if not prevent, trauma to preserve the vitality of the tooth .

2. Thermal injury2. Thermal injury

Cutting of dentin with bur or stone produce a considerable frictional heat .

This operation can be presented in the following equation ;

Mech.E >>>> Cut + Heat . Based on that equation several factors influence the

quantity of the heat produced; a .Speed of rotation . A higher speed has more mechanical

energy, so it will produce more cut and more heat .

2. Thermal injury .2. Thermal injury .

b. Size and shape of cutting instrument . More important the contact with tooth tissues higher the mechanical energy transferred is , so the heat produced is more important .

c. Quality of the instrument. A new instrument produce less heat than old one.

Mech.E-----> Cut + Heat New bur ---> More Cut + Less Heat Old bur (more friction)---> Less Cut + More Heat

A. TUNGSTEN CARBIDE ROUND BUR BEFORE USE B. SAME A. TUNGSTEN CARBIDE ROUND BUR BEFORE USE B. SAME BUR AFTER PREPARING 5 CAVITIES. C. EXTRA-COARSE BUR AFTER PREPARING 5 CAVITIES. C. EXTRA-COARSE

DIAMOND BUR BEFORE USE. D. SAME AFTER PREPARING 2 DIAMOND BUR BEFORE USE. D. SAME AFTER PREPARING 2 CAVITIES. LOSS OF ABRASIVEON DOME END. TUNGSTEN CAVITIES. LOSS OF ABRASIVEON DOME END. TUNGSTEN CARBIDE ALWAYS CHATTERED. THE COARSE DIAMOND CARBIDE ALWAYS CHATTERED. THE COARSE DIAMOND

WAS THE ONLY ONE THAT CUT SMOOTHLY AND REMAINED WAS THE ONLY ONE THAT CUT SMOOTHLY AND REMAINED EFFECTIVE AFTER 5 CAVITIES PREP(Stokes AN and Tidmarch EFFECTIVE AFTER 5 CAVITIES PREP(Stokes AN and Tidmarch

BG.) BG.)


d. Length of time the instrument in contact with the dentin. Interrupted touches produce less heat than long contact.

This situation could be compared to one who try to touch a hot instrument or try to drink a hot coffee or tea (energy source), a touch for short time doesn’t harm and he doesn’t feel the heat, but a touch for long time will cause burn.

DIAGRAM ILLUSTRATING THE DIFFERENCE IN SIZE AND DIAGRAM ILLUSTRATING THE DIFFERENCE IN SIZE AND DENSITY IN TUBULES IN THE DENTINAL FLOOR BETWEEN A DENSITY IN TUBULES IN THE DENTINAL FLOOR BETWEEN A

SHALLOW (A) AND A DEEP (B) CAVITY PREPARATION. SHALLOW (A) AND A DEEP (B) CAVITY PREPARATION. (Trowbridge HO: Dentistry 22(4):22-29 1982)(Trowbridge HO: Dentistry 22(4):22-29 1982)


e. Amount of pressure exerted on the handpiece. This situation could be a reflex when the bur doesn’t cut anymore (dull bur).

f. The thermal conductivity of the dentin is relatively low, so the heat produced in the shallow preparation is less likely to injure the pulp than a deep cavity prep.

2. Thermal injury.2. Thermal injury.

The greatest potential for damage (during dry prep.) was within 1-2 mm radius of the dentin being cut; so deeper the cavity is more dentinal tubules and more odontoblast will be involved in the heat effect.

So how to control this produced heat. In a study using a low speed (11000 RPM) with and without coolant;

With water and air spray---> only minor change in blood pulpal flow.

RISE IN TEMPERATURERISE IN TEMPERATURE AT THE DENTIN-ENAMEL JUNCTION AT THE DENTIN-ENAMEL JUNCTION

AS RELATED TO TYPE OF COOLANT USED .(Thompson, R,E; AS RELATED TO TYPE OF COOLANT USED .(Thompson, R,E; Thermal effects in teeth. Thesis ,University of Utah, June 1971) Thermal effects in teeth. Thesis ,University of Utah, June 1971)

PULPAL TEMPERATURE RISE DURING TOOTH PULPAL TEMPERATURE RISE DURING TOOTH PREPARATION. GROUP I, AIR TURBINE, WATER COOLED; PREPARATION. GROUP I, AIR TURBINE, WATER COOLED;

GROUP II, AIR TURBINE, DRY;GROUP III,LOW SPEED WATER GROUP II, AIR TURBINE, DRY;GROUP III,LOW SPEED WATER COOLED; GROUP IV, LOW SPEED, DRY.( Zach L, Cohen G: oral COOLED; GROUP IV, LOW SPEED, DRY.( Zach L, Cohen G: oral

surgery 19:515 1965.) surgery 19:515 1965.)


Without coolant ---> heat generation---> the flow was further reduced 1 hour after cutting cessation---> suggesting severe damage underneath the cutting site--->irreversible damage.

g. Effect of local anesthesia. Vasocontrictor potentiate and prolong the anesthesia effect by reducing blood flow, which place the pulp in jeopardy (danger).

B A or infiltration cause significant decrease in pulpal blood flow last for short time.

EFFECTS OF CROWN PREP. IN DOGS, WITH AND WITHOUT EFFECTS OF CROWN PREP. IN DOGS, WITH AND WITHOUT WATER AND AIR SPRAY (AT 350,000 RPM) ON PULPAL WATER AND AIR SPRAY (AT 350,000 RPM) ON PULPAL

BLOOD FLOW. (Pathways of the pulp, Eight Edition)BLOOD FLOW. (Pathways of the pulp, Eight Edition)


Ligamental injection of (lidocain 1/100000) will decrease the pulpal blood flow for 30 minutes. Irreversible pulpal injury apt to occur when dental procedure such as full crown prep performed immediately after ligamental injection.

However healthy pulp can withstand a period of reduced blood flow which return to normal with the sensory nerve activity after 3 h of total cessation of blood flow.

EFFECTS OF INFILTRATION ANESTHESIA (2% LIDOCAINE EFFECTS OF INFILTRATION ANESTHESIA (2% LIDOCAINE WITH 1:100,000 EPINEPHRINE) ON PULPAL BLOOD FLOW IN WITH 1:100,000 EPINEPHRINE) ON PULPAL BLOOD FLOW IN THE MAXILLARY CANINE TEETH OF DOGS (Kim S: Effects of THE MAXILLARY CANINE TEETH OF DOGS (Kim S: Effects of local anesthetic on pulpal blood flow in dogs, J Dent Res.63 (5) local anesthetic on pulpal blood flow in dogs, J Dent Res.63 (5)

650 1984.) 650 1984.)

LIGAMENTAL INJECTION (2% LIDOCAINE 1:100,000 LIGAMENTAL INJECTION (2% LIDOCAINE 1:100,000 EPINEPHRINE) CAUSED TOTAL CESSATION OF PULPAL EPINEPHRINE) CAUSED TOTAL CESSATION OF PULPAL

BLOOD FLOW FOR 30 MINUTES.BLOOD FLOW FOR 30 MINUTES.


So cessation of blood flow for 30min +tooth prep for full C which release--->vasoactive agent, substance p, will result in the accumulation this substance and other metabolic waste products which may result in permanent damage to the pulp.

Based on that it is advisable to avoid ligamental injection for cavity and crown preparation and keep this type of injection for tooth extraction and pulp extirpation.

2. Thermal injury2. Thermal injury h. Blushing of teeth is attributed to frictional heat. It is

the result of vascular stasis in the subodontoblastic capillary plexus flow, if the dentin with pinkish hue the case could be reversible under favorable conditions. If it is purplish color, it indicates a thrombosis, so a poor prognosis should be expected.

Goodacre summarized (to minimize the thermal effects, tooth preparation should be performed using an ultra highspeed handpiece (250,000-400,000 rpm) with an air-water spray from multidirectional water ports

2. Thermal injury. 2. Thermal injury.

Waetr flow rate should be at 50 ml/minute and the water should be regulated to be below body temperature (ideally 30-34 C).

Excavation of soft tissues in the deep part of the tooth should be done by slower speed (160,000 rpm or less) using a new carbide bur.

DIAGRAMMATIC REPRESENTATION OF THE ODONTOBLAST DIAGRAMMATIC REPRESENTATION OF THE ODONTOBLAST LAYER AND SUBODONTOBLAST REGION OF THE PULP. LAYER AND SUBODONTOBLAST REGION OF THE PULP.

(Pathways of the Pulp, Eight Edition)(Pathways of the Pulp, Eight Edition)

3. Transection of the 3. Transection of the odontoblastic processodontoblastic process

Determining the exact cause of the death when the odontoblasts disappear after restorative procedure is not possible.

Seltzer et al. showed that damaging pulp changes may develop when impressions are taken under pressure.

Bacteria placed into a freshly prepared cavity were forced into the pulp. Moreover, the negative pressure created in removing an impression may also cause odontoblastic aspiration.

SCHEMATIC ILLUSTRATION OF FACTORS THAT MIGHT SCHEMATIC ILLUSTRATION OF FACTORS THAT MIGHT CAUSE PULPAL REACTION. (Pathways of the Pulp, Eight CAUSE PULPAL REACTION. (Pathways of the Pulp, Eight

Edition).Edition).

4. Crown preparation4. Crown preparation

Studies of long term effects of crown prep on the pulp vitality found a higher incidence of pulp necrosis.

With full crown prep 13.3%.With partial veneer prep 5.1%.Unrestored control tooth 0.5%.

5.Vibratory phenomenon.5.Vibratory phenomenon. Shock waves produced by vibration are particularly

pronounced when: The cutting speed is reduced. Distorted bur. Loose bur clutch. Eccentric rotation looseness of handpiece tip. Crazing of enamel can be caused by eccentric rotation of

the bur. The vibration across enamel or early in the dentinoenamel

junction may induce slight inflammation in the underlying pulp.

6. Desiccation of dentin. 6. Desiccation of dentin.

In cavity or crown prep, about 1mm in the dentin, (2.1--->2.5mm away from the pulp) the number of dentinal tubules is 11000---> 36000/mxm.

When the surface of freshly cut dentin is dried with a jet of air, or a cavity drying agent, a strong hydraulic forces are created on the dentinal tubules, causing a phenomenon of odontoblast displacement.

In this reaction the cell bodies of odontoblast are displaced upward in the dentinal tubules.

DIAGRAM ILLUSTRATING MOVEMENT OF FLUID IN THE DIAGRAM ILLUSTRATING MOVEMENT OF FLUID IN THE DENTINAL TUBULES RESULTING FROM THE DEHYDRATION DENTINAL TUBULES RESULTING FROM THE DEHYDRATION

EFFECTSOF A BLAST OF AIR FROM AN AIR SYRINGE. EFFECTSOF A BLAST OF AIR FROM AN AIR SYRINGE. (Pathways of the Pulp,Eight Edition).(Pathways of the Pulp,Eight Edition).

ODONTOBLASTS (ARROW) DISPLACED UPWARD IN THE ODONTOBLASTS (ARROW) DISPLACED UPWARD IN THE DENTINAL TUBULES.(Pathways of the Pulp,Eight Edition).DENTINAL TUBULES.(Pathways of the Pulp,Eight Edition).

6. Desiccation of dentin.6. Desiccation of dentin.

Such displacement result in the loss of odontoblasts which undergo autolysis and disappear from the tubules.

Desiccation of dentin by cutting procedures or air does not injure the pulp.

The destroyed odontoblasts are replaced by new ones arise from the cell-rich zone of the pulp, and in 1-3 month reparative dentin is formed.

7. Pulp exposure.7. Pulp exposure.

Exposure of the pulp may occur during : a. Cavity preparation. b. Excavation of carious dentin. c. Accidental mechanical exposure may result

during placement of pins or retention point in dentin.

In general, if it is sterilized exposure vitality of the tooth could saved.

Occasionally a pulp exposure is made unknown to the dentist because there is no bleeding.

Cement forced into the pulp during Cement forced into the pulp during cementation. pulpitis and severe pulpalgia cementation. pulpitis and severe pulpalgia

resulted.(Ingle. Blackland Endodontics 5resulted.(Ingle. Blackland Endodontics 5 thth Ed.) Ed.)

8. Smear layer.8. Smear layer.

It is amorphous smooth layer of microcristalline debris.

This layer may interfere with the adaptation of restorative material to dentin, it may not be desirable to remove the entire layer but leaving plugs in aperture of the dentinal tubules.

Brannstrom believes that most of restorative materials do not adhere (has poor adaptation) to the dentinal wall which leaves gaps invaded by bacteria from oral cavity or the contaminated smear layer causing pulp irritation.


Removal of the entire smear layer by acid etching increase the permeability of the dentinal tubules, so the incidence of hypersensitivity and pulpal inflammation may be increased unless a cavity liner, base, or dentin bonding is used.

However, current treatment of hypersensitive teeth is directed toward reducing the functional of the dentinal tubules to limit fluid movement.

Four possible treatment modalities are considered to achieve this goal:


A. formation of smear layer on the sensitive dentin by BURNISHING the exposed dentin.

B. application of agents, such as OXALATE COMPOUNS that form insoluble precipitates within the tubules.

C. impregnation of the tubules with PLASTIC RESINS. D. application of DENTIN BONDING AGENTS to

seal off the tubules. LASER irradiation can modify dentin sensitivity, but

care should be considered of its pulp effects.

9. Remaining dentin 9. Remaining dentin thickness.thickness.

Dentin permeability increases almost logarithmically with increasing cavity depth (difference in number and size of dentinal tubules.

Increasing dentin permeability means increasing of dental pulp injury from restorative procedures.

2mm of dentin thickness would protect the pulp from the effects of restorative procedures. (Stanley)

In carious teeth a distance of 1.1mm or more between the invading bacteria and the pulp the inflammatory responses are negligible.

REPARATIVE DENTIN (RD) DEPOSITED IN RESPONSE TO A REPARATIVE DENTIN (RD) DEPOSITED IN RESPONSE TO A CARIOUS LESION IN THE DENTIN. (Trowbridge HO; CARIOUS LESION IN THE DENTIN. (Trowbridge HO;

Pathogenesis of pulpitis resulting from dental caries, J Endod. 7;52 Pathogenesis of pulpitis resulting from dental caries, J Endod. 7;52 1981) 1981)

9. Remaining dentin 9. Remaining dentin thickness.thickness.

Reversible pulpitis can be noticed when the remaining sound dentin between the lesion and the pulp is about 0.5mm. The irreversible pulpitis takes place when this reparative dentin is invaded.

Reparative dentin has low permeability so it reduces the incoming bacterial antigens,but it must be considered that this not always the case. Reparative dentin can be deposited in a pulp which is irreversibly injured, SO PRECAUTIONS SHOULD BE DONE IN THE DIAGNOSIS AND TREATMENT.

9. REMAINING DENTIN TH.9. REMAINING DENTIN TH. In young teeth,try to limit the preparation,so using the

resin bonded bridge (Maryland) is advised. Consider the preparatory treatment to correct the

position ( inclination, buccal or lingual position) of the teeth to be prepared.

Consider the tooth anatomy when you prepare. Use a carbide bur to excavate the soft tissues when

there is no symptoms indicating irreversible pulpitis, but don’t excavate completely the soft tissues over the pulp.

Protect the dentin freshly cut by using temporary filling or temporary crown.

RELATIONSHIP BETWEEN TOOTH PREP. AND PULP RELATIONSHIP BETWEEN TOOTH PREP. AND PULP CHAMBER SIZE. THE DOTTED LINES REPRESENT PULP CHAMBER SIZE. THE DOTTED LINES REPRESENT PULP CHAMBER MORPHOLOGY AT VARIOUS AGES. (Ohashi CHAMBER MORPHOLOGY AT VARIOUS AGES. (Ohashi

Y:Shikagakuho 68:726, 1968.)Y:Shikagakuho 68:726, 1968.)

10. Acid etching.10. Acid etching.

Its designed to enhance the adhesion of the restorative materials.

It increases the permeability and bacterial penetration of the dentin.

Results of one physiologic investigation have shown that acid etching with a remaining of 1.5m has little effect on pulpal blood flow.

In practice etching dentin for 15sec has no pulp effects, but protecting the pulp when the cavity is deep should be considered.

10. Acid etching.10. Acid etching. Acid etching is necessary to improve bonding to the

enamel as a part of the composite technique. On the dentin, it is believed that it may improve bonding

by the removal of the smear layer, grinding debris, bacteria and denaturated collagen.

Citric and phosphoric acids were used, these experiments were followed by pulpal inflammatory responses.

Apparently these reactions were because of the strength of the acid 50%, length of application 5min, remaining dentin, micro leakage under the resin and the bacterial invasion.

10. Acid etching.10. Acid etching. Brannstrom, Pashley, White and Cox, concluded that acid etching on vital

dentin doesn’t cause pulp inflammation when the acid is diluted and applied for short time.

Fusayama in Japan, and Kanca and Bertalotti in U.S.A. popularized dentin acid treatment claiming no deleterious pulpal effects, taking in consideration the application of a dentin bonding agent, thus eliminating the micro leakage.

Kanca used 37% ph.acid gel for 15 sec.only, others 10% polyacrylic, or citric acid for 10 sec .

Acid etching open dentinal tubules so a liner or base, or better dentin bonding agent to be used.

11. Immunodefense of the 11. Immunodefense of the pulp to tooth preparationpulp to tooth preparation

It is related to the depth and the extension of the preparation.

Negligible changes follow shallow preparation with copious water coolant.

A deep prep impact the pulp more severely with stronger pulp cell reaction, release of substance p and by the sensory nerve cells.

Increasing of the pulp flow initially then decreased severely because of the low –compliance environment of the pulp.

11. Immunodefense11. Immunodefense……

Finally, immunodefense cells of the type that appeared in response to caries accumulate underneath the area of tooth preparation.

Reaction to cavity or crown prep relatively deep result in loss of of primary odontoblasts.

Formation of reparative dentin by new odontoblasts which due to a mitotic activity an differentiation of the fibroblast in the cell-rich zone.

12. Comparison of cavity prep 12. Comparison of cavity prep by high speed handpiece and by high speed handpiece and

bur and Er.YAG laserbur and Er.YAG laserIn general there were no noticeable

histopathologic difference between the laser and the high speed.

The question to be asked is whether the laser is more efficient than the high speed handpiece for this purpose.

(Erbium,chromium:yetterium-scandium-gallium-garnet laser hydrokinetic system)

13. Pin insertion.13. Pin insertion. Increase in pulp inflammation and death has been

noted since the use of dentinal pins. In a study on on extracted molar teeth, researchers

found that placing 1 pin in its correct position caused cracks extended into the pulp in73%,2 pins would cause pulp exposure in 93%,3 pins 98%.

Placing the pins, close to the pulp,in presence of calcium hydroxide protect the underlying pulp which remained normal, otherwise it may cause pulp inflammation. (Suzuki and colleagues)

Pins are gradually replaced by adhesive.

CRACKS CAUSED BY INSERTION OF DENTINAL PIN.CRACKS CAUSED BY INSERTION OF DENTINAL PIN.(Courtesy of Schlissell et al, J. Dent. Res.). (Courtesy of Schlissell et al, J. Dent. Res.).

Pin placement with calcium hydroxide.note Pin placement with calcium hydroxide.note dentinal cracks from the force of insertion. dentinal cracks from the force of insertion. Cracks filled with CH.with moderate pulp Cracks filled with CH.with moderate pulp

inflammation under affected tubules. (Suzuki M, inflammation under affected tubules. (Suzuki M, Goto G, Jordan RE. J Am Dent. Goto G, Jordan RE. J Am Dent.

Assoc.1973;87;636).Assoc.1973;87;636).

Pin placement with calcium hydroxide and no Pin placement with calcium hydroxide and no dentinal fracture. Irritation dentin response is dentinal fracture. Irritation dentin response is apparent in 28 days. The remaining dentin apparent in 28 days. The remaining dentin

thickness is 0.5mm. (Suzuki M, Goto G, Jordan thickness is 0.5mm. (Suzuki M, Goto G, Jordan RE. J Am Dent Assoc 1973;87:636.)RE. J Am Dent Assoc 1973;87:636.)

14. Pulp horn extension.14. Pulp horn extension.

In a remarkable investigation of the coronal pulp chamber of U/L molars, Sproles discovered cervical pulp horns in about 66.8---->96.3%.

This extra pulp horn, in the furcal plane area where the pulp is only 1.5-2mm away before prep, is considered a real danger in crown and cavity prep.

It is found in the mesio-buccal of the U/molars 65%,and 61%in the /L molars.

SPROLESPROLE’’S CERVICAL PULP HORNS, FOUN IN MULTIPLE S CERVICAL PULP HORNS, FOUN IN MULTIPLE LOCATION IN UP TO 96.3% OF MOLAR TEETH, EXTEND LOCATION IN UP TO 96.3% OF MOLAR TEETH, EXTEND

PERILOUSLY CLOSE TO THE TOOTH SURFACE NEAR THE PERILOUSLY CLOSE TO THE TOOTH SURFACE NEAR THE CEMENTOENAMEL JUNCTION.(Sprole RA.)CEMENTOENAMEL JUNCTION.(Sprole RA.)

15. Prevention of pulp injury.15. Prevention of pulp injury.

The University of Connecticut reported that “previous restorative treatment was the major etiologic factor leading to root canal therapy”

There are many day-to-day insults levied against the pulp that can be PREVENTED: (1) depth of cavity and crown prep, (2) width and extension of cavity and crown prep, (3) heat damage and desiccation during cavity prep, (4) chemical injury through medicaments, (5) toxic cavity liner and base, (6) toxic filling materials, and (7) prevention of micro leakage.

THANK YOUTHANK YOU

pulpal reaction to cavity and crown

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