INTRODUCTION

DEVELOPMENT

Dental papilla

Enamel organ

Oral epithelium

• development of dental papilla 8thweek of embryonic life.

• Cell density of dental papilla is great.

• The young papilla is highly vascularise and well organized network of vessels at time of dentine formation bigins.

• Capillaries crowded among odontoblast period of dentinogenesis.

• Cells of dental papilla appear as undifferntiatedmesenchymal cells differntiated into fibroblst.

• Ameloblast differntiated from enamel organ and odontoblast differntiated from dental papilla.

-orbans

Anatomy of Pulp

Pulp Chamber or coronal pulp, located in the crown of the tooth.

Root canal or radicular pulp, is the portion of the pulp located in the root area.

The apical foramen is the opening from the pulp at the apex of the tooth.

Accessory canals or lateral canal, extra canal located on the lateral portions of the root.

Pulp horns

CORONAL PULP

RADICULAR PULP

APICAL FORAMEN

ACCESSORY CANALS

STRUCTURAL FEATURES

• Histologically, 4 distinct zones can be seen

1. Odontoblastic zone : at pulp periphery

2. Cell free zone of Weil : beneath

odontoblasts, prominent in coronal pulp,

odontoblasts move into this space during

development.

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3. Cell rich zone : High cell density

adjacent to cell free zone, contains

fibroblasts, undifferentiated mesenchymal

cells. Prominent in coronal pulp.

4. Pulp core : containing major vessels &

nerves of pulp.

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Predentin

Odontoblasts

Cell-free zone

Cell-rich zone

Cell bodies

Odontoblasticprocess

Dentin

Predentin

Odontoblasts layer

Cell free zone

Cell rich zone

Pulp core

INTERCELLULAR SUBSTANCE

• Functions :

COLLAGEN FIBERS• Typical cross striations at 64 nm

• Length – 10 to 100 nm

• Bundles of fibers appear throughout the pulp

Pulpal collagen is a mixture Types I & III at a ratio of 55:45

• Young pulp – 10 to 12 nm in diameter

• After root completion pulp matures & bundles of collagen fibers increase in number.

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UNDIFFERENTIATED MESENCHYMAL CELLS

FIBROBLASTS

ODONTOBLASTS

• Number of odontoblasts = Number of dentinal tubules.

• Size – 5 to 7 micro meter in diameter.

• 25 to 40 micro meter in length.

• Cross-sectional view reveals 59,000 –76,000

tubules per square millimeter.

• Numerous in coronal dentin than root dentin.

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ODONTOBLASTIC PROCESS

Cell bodies of odontoblasts have junctional complexes

There are 3 types of intercellular junctions.

1. Impermeable junctions : also known as tight junctions, help the cell maintain a distinct internal environment. In these junctions , the plasma membranes of adjacent cells appear to fuse and afford a tight seal between cells.

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2 . Adhering junctions : • Threads of tonofilaments project from the

cellular cytoplasm into and out of electro dence material called plaques or patches but do not cross over neighboring cells.

• They are maintained by desmosomes, which are intercellular bridges. Adhering junctions promote adhesion between 2 cells.

3. Communicating junction : also known as gap junction.

DEFENSE CELLS

• Histiocytes or macrophages, mast cells & plasma cells – these are important to defense of the pulp.

• In addition there are blood vascular elements such as neutrophils, eosinophils, basophils, lymphocytes & monocytes.

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BLOOD VESSELS• Extensively vascularized

• Blood vessels arise from - Inferior or Superior alveolar

artery

• Communication – pulp with Periodontium – Apical

foramen

Clinical significance –

• Potential pathological conditions

• Infection can also spread through the accessory canals.

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• Smaller arteries and arterioles enter the apical canal – direct route to coronal pulp.

• Along their course they give numerous branches in the radicular pulp – to form plexus in odontogenic region.

• Pulp blood flow is more rapid than in most areas of the body.

• Pulpal pressure is among the highest of body tissues.

• Flow of blood:

In arterioles – 0.3 – 1 mm /second

In venules – 0.15 mm/second

In capillaries – 0.08mm/second - weine

• The largest arteries in the human pulp are 50- 100 micro meter in diameter, equaling in size arterioles found in most areas of the body.

• These vessels possess 3 layers:

1. Tunica intima

2. Tunica media

3. Tunica adventitia

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LYMPH VESSELS

• Endothelial lined tubes that join thin walled

lymph venules or veins in the central pulp.

• Lymph vessels draining the pulp and PDL have

common outlet.

• Anterior teeth – Submental lymph node.

• Posterior teeth – Submandibular and deep

cervical lymph node.

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NERVES

• Majority of nerves that enter pulp are non myelinated.

• These will gain myelin sheath later in life.

• Non myelinated nerves are found in close association with blood vessels of pulp.

• Thick nerve bundles enter the apical foramen and proceed to the coronal area and radiate peripherally to the odontogenic zone.

• The no. of fibers vary from 150 to more than 1200.

• Largers fibers – 5 to 13 micro meter.

• Majority are smaller than 4 micro meter.

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• More nerve fibers and endings are found in the pulp horns than in peripheral areas of coronal pulp.

• Sensory response cannot differentiate between heat and touch, pressure or chemicals.

• Because of lack of receptors.

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FUNCTIONS

• Formative : It forms dentin and continues to do so throughout the life of the tooth.

• Nutritive : vascular tree nourishes all the vital elements of pulpodentinal complex.

• Nervous : both sensory and motor nerves play in pain transmission.

• Defensive : protective role played by odontoblasts.

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FORMATIVE

• Primary dentin – tubular & regularly

arranged, odontoblasts are not crowded and is under minimal functional stress.

• Secondary dentin – dentin produced is wavier and contains fewer tubules, odontoblastsbecome crowded and their direction is altered, also known as functional dentin.

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• Irritation dentin – operative procedures, caries produce initial episodes of rapid formation of dentin

• Defense mechanism to compensate for regional dentin loss on the surface

• Scar tissue formed in response to local lesion.

• Also known as tertiary dentin, reparative dentin, irregular dentin.

• Less sensitive to external stimuli as there is disruption in the continuity of odontoblasticprocess.

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NUTRITUVE• Maintains the vitality of dentin by providing

oxygen and nutrients to the odontoblasts and their processes.

• Arteries & veins are dental branches of superior & inferior alveolar vessels.

• Terminal Capillary Network (TCN) maintains the vitality of dentin by its numerous projections into the odontoblastic zone.

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NERVOUS

• Sensory nerves are branches of the Maxillary & Mandibular divisions of the Trigeminal nerve.

• They enter through the apical foramina & divide into smaller units as they proceed coronally.

• adjacent to the cell-free zone, the nerves branch extensively, forming the parietal layer of nerves called the plexus of Raschkow.

• Plexus of Raschkow containsMyelinated A-δ fibers – 2 - 5µm in diameterUnmyelinated C fibers – 0.3 -1.2µm in diameter

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Mechanism of Pain Transmission

Specificity theory:

Pattern theory

Gate control theory:

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Pattern theory:

• Pain is generated by non-specific receptors.

• All nerve fiber endings are alike & pattern for pain is produced by more intense stimulation than for other sensations.

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Gate control theory:

• A gating mechanism is located in a specific area of gray matter in the spinal cord called the substantia gelatinosa.

• Receives painful impulses from peripheral nerves & permits their passage to the brain by opening the gate, or prevents their passage by closing the gate.

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Whether the gate opens or closes depends on

• Speed of impulse

• Interaction between noxious pain stimuli transmitted along the smaller diameter fibers

• Those stimuli of touch & pressure that are transmitted along the larger diameter fibers.

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REGRESSIVE CHANGES

• Cell changes

• Fibrosis

• Pulp stones or denticles

• Diffuse calcifications

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CELL CHANGES

• Decrease in size & number of

cytoplasmic organelles

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FIBROSIS

• In aging pulp accumulation of both diffuse fibrillar components as well as bundles of collagen fibres

• Coronal pulp : diffuse

• Radicular pulp: longitudinal fiber bundles

• At traumatic area: localised fibrosis (scarring) - orbans

PULP STONES OR DENTICLES

• Nodular, calcified masses appearing in either or both the coronal or root portions of the pulp organs

• Single or multiple

• Seen in functional & embedded teeth

• - orbans

Classification:

1. According to structure

- True denticle

- False denticle

- Diffuse calcifications

2. According to location

- Free

- Attached

- Embedded

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TRUE DENTICLE

• Structure is similar to dentin, they exhibit dental tubuli containing process of odontoblasts

• Comparatively rare

• Usually located close to apical foramen

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• Caused by Inclusion of Remnants of epithelial root sheath within pulp.

• Induce cells of pulp to differentiate into odontoblasts.

• Which then form dentin masses called true pulp stones.

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FALSE DENTICLES

• Arise around vessels.

• Concentric layers of calcified tissue

• Appears within a bundle of collagen fibers

• In center of these concentric layers of calcified tissue – remnants of necrotic and calcified cells

• All denticles begin as small nodules –increase in size by incremental growth

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DIFFUSE CALCIFICATIONS

• Appears as irregular calcific deposits in the pulp tissue

• Following collagenous fiber bundles or blood vessels

• Usually seen in radicular pulp

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• Free denticle: entirely surrounded by pulp

• Attached: partly fused with dentin

• Embedded: entirely surrounded by dentin

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FREE TRUE DENTICLE

FREE FALSE DENTICLE

Pulp stones found in

• 66% of teeth in 10 –30 yrs

• 80% of teeth in 30 –50 yrs

• 90% of teeth in >50 yrs

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Disease of the dental pulp

• Hyperalgesia

Hypersensitive dentine

Hyperemia

• Pulpitis

Acute pulpitis

Subacute pulpitis

Chronic pulpitis

• Pulp necrosis

• Calcification

• Internal resorption

Applied aspect

• Each step in full crown procedure , like crownpreparation, impression making , temporaryrestoration and final cementation may injure thepulp and may lead to pulpitis or even necrosis.

• Heat, drying and chemical irritation are the mainoffending factors.

• So during each step proper precautions should totaken to prevent or minimize pulpal damage.

• Crown preparation:

• The shape of the pulp chamber and itsextensions into the cusps, the pulpal horns, isimportant to remember. The wide pulpchamber in the tooth of a young person willmake excessive tooth reduction hazardousand it should be avoided.

• Intermittent continuous preparation

Temperature

pulp temp. se by 5.5 15% I.P

se by 11.1 60% I.P

41.5 plpal inflammation

Preparation of full crown with air cooled high speed instrument can generate an average temperature increase by 8.8 degree Celsius.

-J.O.R

RDT(remaining dentinal thickness)

• Main etiological factor is dentine injury.

• No harmless, non traumatic technique for crown preparation.

• O.5 mm of RDT 75% reduction in toxin effect on pulp.

• 1mm RDT 90%

• Little pulpal reaction at 2 mm.

Type of handpiece

• High torque/high speed=air turbine handpiece

Speed of rotation

• 50,000 rpm greatest amount of

odontoblastic damage.

with belt and turbine driven.

• 150,000 rpm-250,000 rpm least damage.

Pressure during preparation

• Force should be less than 8oz.

• Increase bur pressure may cause displacement odontoblastic nuclie into dentinal tubules.

Nature of cutting instrument

• Carbide bur better than steel and diamond bur.

• Vibration of bur also affect the pulp.

Size of wheel and burs

• Larger size produce greater pulpal damage.

coolants

• Can be air spray

water spray

air-water spray.

Air spray: withot air spray temp. rise by 14 F

with air spray rise in 1 F

not much difference…

• Water spray:

with water spray pulpal blood flow reduced by 12% after 1 hr reduced within 7% of the control.

Without water spray 44% reduction of blood flow. after 1 hr further increase.

• Combination of air and water is not much effective.

Impression materials • Impression compound increase

temparature of pulp chamber. Rising temp upto 52 degree Celsius which is an increase of 15 degree celsius and remain for 3 minutes.

• Rubber base and hydrocolloid impression materials do not increase pulpal temp.

Restorative materials

• Zinc phosphate :it cause severe pulpal damage.

thin mix is better than thick.

• ZOE: it is toxic to the pulpal cells and more

irritating than zinc phosphate.

• GIC: when tested in cell culture it is toxic to the

fibroblast.

greater degree of pulpal inflammation than ZOE.

• Resin containing materials adhesive cement

Newer approach

•Regeneration

•Revascularization

Methods for saving pulp

• Indirect pulp capping

• Direct pulp capping

• Pulpotomy

Conclusions

• A vital/healthy pulp is essential for good dentition.

• So the preservation of a healthy pulp duringprosthetic and operative procedures and successfulmanagement in cases of disease are two of the mostimportant challenges to the clinical dentist.

• When filling materials containing harmful materialsare to be used, then an appropriate liner should beused.

References

• Oral histology and embryology-Orban’s 11th edition

• The dental pulp-Seltzer’s 3rd edition

• Wiene

- fifth edition

• Journal of oral rehabilitation 1997,24

• Dental materials journal,2008,27