Pulp response to
cavity
preparation
Restorative
materials
CONTENTS
Introduction
Pathophysiology of pulpal infection
Pulpal reactions
Causes of possible pathologic response
of pulp to operative procedures
• Reaction to operative procedures
•
•
•
•
Factors causing pulpal reaction
• Dessication of dentin
• Vibratory phenomenon
• Depth of cavity preparation
• Speed of rotation
• Heat and pressure
• Dry cavity procedures
•
•
•
•
•
•
Nature of cutting instrument
Size of wheels and burs
Extensiveness of preparation
Pin restoration
Rebound response
Polishing of restoration
Chemical irritants
• Dentin sterilizing agents
• Cleansing and drying medicaments
• Acid etchants
• Bleaching
Laser
INTRODUCTION
• The effect of restorative procedures on
dentin and pulp represent a combined
response to preparation and to restoration.
• Every aspect of restorative dentistry
potentially has an effect on pulp dentin
complex.
• Most of these effects are indirect,
mediated via diffusion through dentin.
• No restorative material exists that is
truly inert in biologic sense and any
Pulpal and dentinal change that result
from the preparation can effect the
evaluation of reactions to the entire
restorative procedure.
•
Long term maintenance of a healthy pulp is a
result of atraumatic preparation and the use
of biologically acceptable materials that can
seal the tooth restoration interface to
prevent or minimize bacterial leakage.
Pathophysiology of pulpal inflammation
Pulpal reactions
Langeland 1957,Stanley 1968
SLIGHT
MODERATE
SEVERE
Slight
•
in no of cells in cell free zone
• fibroblasts & undifferentiated
mesenchymal cells
• Few inflammatory cells
• Increase no of capillaries
• Localized to affected dentinal tubules
Moderate reaction
• More cells in area subjacent to affected
dentin
• Neutrophilic and mononuclear leukocytes
invade odontoblast- predentin area
• Increased number of capillaries & vessels are
found in infiltrated tissue and its border
Severe reactions
• Marked cellular infiltration with abscess
formation
• PMN’s & mononuclear leucocytes predominate
in affected area
• Odontoblastic layer cannot be identified
• No predentin is formed and with in days
existing predentin mineralizes
Causes of possible pathological
responses of dental pulp related to
operative dentistry
• Physical: occlusal interference,
condensation, air blowing or dentin
dehydration
• Thermal: heat from cutting, insufficient
pulpal protection for metallic restoration
• Electrochemical: galvanism
• Chemical: toxicity of dental materials, acid
etching
• Bacterial: toxin products
• Traumatic stimuli: abrasion, attrition,
erosion  dentin exposed
• Operator: poor contour-contact,
overhanged margin, poor anatomy,
damage of adjacent tooth
Natural defense mechanisms
• Dentinal sclerosis
• Reparative dentin formation
• Smear layer; controversial
Reparative dentin is a
tertiary dentin matrix
formed by new
odontoblast like cells in
response to a specific
stimulus, while
Reactionary dentin is
formed by surviving
odontoblasts subjacent
to diseased or otherwise
damaged dentin.
Reparative dentin under restorations
• Avg. daily reparative dentin reported to be
2.8microns for deciduous and 1.5 microns for
permanent teeth (stanley)
• Begins earlier in shallow cavities
• rate is more rapid but the quality is poorer
than dentin formed under shallow preparation.
Reaction to operative
procedures
Restorative factors contributing to Pulpal injury
Effects of
Cavity
Preparation
Frictional heat
Desiccation
Exposure of dentinal tubules
Direct damage to odontoblast processes
Chemical treatmt of the exposed dentinal surface
Factors associated with
restorative material
& its placement
Effects subsequent
to restoration
Material toxicity
Insertion pressures
Thermal effects
Induced stresses
Marginal leakage
Cuspal flexure
Factors that might cause pulpal reaction
Cleansing & Sterilizatn
Acid etching
Impressions
Restorative materials
Frictional HEAT
Vibration
Dessication
Insertion & Cementation
of restorations
Marginal leakage
Pulpal inflammation
Pulpal NECROSIS. Probably
[ Cohen ]
THERMAL INJURY
Swerdlow & Stanley → Temp rise in Pulp :
1. FORCE applied by the operator
2. Size, Shape & CONDITION of cutting tool
3. R P M
4. Duration of actual cutting TIME.
Frictional heat will depend on : → By Seltzer
1. Rotational speed & Torque
2. Amount of FORCE applied to bur
3. Cooling efficiency of irrigant
4. Prior wear & design of bur.
PULP
THERMAL INJURY
PULP
Goodacre’s conclusion
• Thermal elevation
low speed ˂ high speed ˂ ultrahigh speed.
Goodacre quoted note of Ottl & Lauer :
Thermal change : Carbide burs ˂ Diamond points.
Temp ↑
: Fine diamonds ˂ Coarse diamonds.
THERMAL INJURY
PULP
Zach & Cohen :
• An intrapulpal temp rise of 5.5°C (10°F) – 15% pulps
become nonvital. (rate of heat application is more)
• Recommended “WASHED – FIELD” Tech :
Before cutting , tooth surface is exposed to the airwater spray for 5 sec. After initial cutting;
following every 4 sec’s of cutting, bur is lifted off the
surface for 1 second. (pulpal temp never rises above
basal temp).
THERMAL INJURY
PULP
BLUSHING of teeth → frictional heat.
• Coronal dentin develops a pinkish hue {vascular
stasis
in
the
sub-odontoblastic
capillary
plexus} very soon after the dentin is cut.
• Under favourable conditions, this reaction is
reversible & pulp will survive.
• But dark purplish color → thrombosis →
poorer prognosis.
• Histologically →adjacent to blushed
dentinal surface RBC’s extravasated
(rupture
of
capillaries
in
odontoblastic plexus).
• Greatest beneath full-crown prepn
sub-
Crown Preparation
In long term study on pulp vitality
PULP NECROSIS
Full- crown preparation
→
13.3 %
Partial veneer restorations → 5.1 %
Unrestored control teeth
→ 0.5 %
Foundations for
full- crown restorations
→ 17.7 %
dessication
Desiccation of Dentin
• Surface of freshly cut dentin → dried (while cutting
or) with a jet of air → rapid outward movt of fluid
thr’ dentinal tubules ( capillary action ).
• Stimulatn of sensory nerves of pulp [ Acc to
hydrodynamic theory ].
• Fluid movt also draw odontoblasts
up into the
tubules.
• These displaced odontoblasts soon die (autolysis)
& disappear.
• But does not injure the pulp.
• Ultimately, ODONTOBLASTS THAT
HAVE BEEN DESTROYED AS A
RESULT OF DESICCATN ARE
REPLACED BY NEW ODONTOBLASTS
THAT ARISE FROM THE CELL-RICH
ZONE OF PULP & REPARATIVE
DENTIN FORMS IN 1 to 3
MONTHS.
Vibratory Phenomenon
• Shock waves produced by vibration are
particularly pronounced when the cutting
speed was reduced.
• Therefore
BY
ON
“STALLING
INCREASED
THE
AVOIDED”.
OF
DIGITAL
HANDPIECE
THE
BUR
PRESSURE
SHOULD
BE
DEPTH OF PREPARATION
&
REPARATIVE DENTIN FORMATION
• Increase the depth of preparation → Increased
rate of reparative dentin formation.
Only if RDT [bet pulp & base of cavity]
half the original thickness
Maximum threshold of stimulus will be
reached.
If further cutting
Greater injury to odontoblasts
Rate of
formation of reparative dentin
decreases
{ irregular structure, Poorly mineralized }.
Even less thickness of dentin if remains formation of reparative dentin inhibited
temporarily &
Odontoblastic cells show signs of atrophy.
Kinetic Cavity Prepn = Airborne Particle Prepn
= Microprepn
• Due to advances in microabration technology
• Precisely remove enamel & dentin.
• Laurell et all found that higher pressures &
small particles had significantly fewer pulpal
effects than the high- speed treated teeth.
• stream of particles cannot be controlled,
resulting in pitting & abratn of adjacent teeth
& injury to gingival tissues.
Depth Of Cavity Preparations
Cavity preparation causes
• Increased rate of collagen turn over
• Odontoblastic cell damage
• Protein synthesis by odontoblasts directly under and
adjacent, to the cavity prep is curtailed.
• As cavity depth if increased more severe is injury to
odontoblasts – increase rate of production of rep dentin.
• With 0.5mm of dentin b/w base of
cavity and pulp decrease of 0.1mm
produces more severe inflammation in
low speed prep without coolant
• With coolant the floor can be brought
much closer to pulp (0.3mm)
• Pashley
Reduction in dentin thickness
increases permeability (increase in
number and diameter of tubules)
Speed of rotation
• Speeds with 3000 or less and 2,00,000rpm
or above are safest with coolant
• Speeds between 3000-30,000 rpm are most
deleterious even with coolant
Riethe
• Without use of coolant no high safe speed
• At 3000-5000rpm less damage without
coolant than at ultra high speed without
coolant
HIGH SPEED CUTTING
• Burns of dentin
• Integrity of pulp threatened
• Charred dentinal tubules – susceptible
to decay
• Ultra high speed should be used for
removal of superficial enamel and
dentin ,finishing done with very low
speed.
• With increase in speed of rotation of cutting
instrument, not only greater heat is
generated but greater vibrations also which
affects the pulp
• Sears mechanical vibrations may be
responsible for protein denaturation of
odontoblasts
• Causes morphologic changes leading to
destruction of cells
Heat & pressure
Heat and Pressure
Factors in production of heat within pulp as a
result of cavity preparation are
•
•
•
•
•
•
•
•
Depth of preparation
Speed of rotation of bur or stone
Size, shape composition of bur / stone
Amount and direction of pressure on cutting
Amount of moisture
Direction and kind of coolant used
tissue being cut
Length of time instrument in contact.
DRY CAVITY PROCEDURES
• Greater trauma than air water spray
• Produces both reversible and irreversible
changes
Prolonged dehydration with air causes
• odontoblastic damage, displacement, pulpal
edema which cannot be reversed.
• Vasodilation
• Increase capillary permeability
• Above 46°c – irreversible changes – stasis,
thrombosis
Initially there is drop of intra pulpal pressure
followed by rise
due to result of chemical mediators (persistent
vasodilation)
• Escape of plasma proteins into interstitial
fluid
↓
• Lowering of osmotic pressure and
accumulation of fluid in pulp chamber.
Kramer (1963),Brown (1978)
Enamel temperature increases with dry
preparation
• May fracture
• May effect dentin and then pulp
• Breakdown tooth structure at margins
• Marginal leakage
• Recurrent caries
Nature of cutting instrument :
Weiss et al
• Greater thermal damage with steel burs, than carbide
• With proper cooling carbide burs produces negligible pulp
damage
• Even with coolant diamond inst are capable of producing
damage to pulp this may be related to additional pressure.
• Simultaneous inc of rotational speeds and pressure by rotary
inst cause temp inc and inc inflammation of pulp
• When force above 8 oZ applied – even use of coolant does
not resist minimize inflammation
↓
• Displacement of odontoblastic nuclie into tubules
Size of Wheels and burs :
• Larger size produce greater damage
• Peripheral speed of larger disc is higher than
small disc at same rpm
• When using large inst greater area is cut.
Coolant cannot get to the tooth as readily
resulting in more severe reactions
• Less severe reactions when smaller size inst
used.
Hand instruments
• damage more severe with hand
instruments
• no heat generations but pressure causes
pulp damage
Coolants
Eliminate heat generation
• Air spray
• Combination air and water
• Water spray
• Water applied through hollow bur
• Water as a jet stream
Air spray
• Air blasts are damaging to pulp
• Compressed air for 10seconds – produces disp of
odontoblastic nuclie.
• Although greater cellular damage with air coolant
repair follows in absence of other irritating
factors
• Recovery depends on health of pulp extent and
depth of prep, extent of damage and no. of cells
present
• Cavity should not be dried with air blasts, instead
use cotton pellets
Water spray
• Temperature elevation is reduced
• Rate of removal of debris increased
• Control inflammation reaction in pulp
Bodecker At high speed/without cooling
“ Cooking the pulp in its own juice”
• Speed 50000 and above – water in form
of jet stream must be used
• Delivered directly at contact between
bur and tooth simultaneously
• cutting done with brush stroke
Temperature of coolants
• Clinically no significant damage on pulp
Temperature Rise during Tooth Preparation without Coolant
60
60
No coolant
Air from syringe
Spray from turbine
Water from syringe
50
40
40
30
30
20
20
10
10
0
0
-10
-10
0
2
4
6
8
10
Time (seconds)
12
14
16
Temperature (degree Celcius)
Temperature (degree Celcius)
50
Extensiveness of the
preparation
Extensiveness of preparation
– Class I and Class V – produce lower heat reaction than
MOD or full crown preparation
– In class I – inc the width & depth of fissure gradually by
shallow angular cuts
– Cavity preparation with high speed inst should be widened
and deepened gradually for proper cooling and to minimize
pulp damage
– In crown preparation – high speed for
gross cutting ,finish the grooving part of
preparation with burs at low speed.
– Shoulder preparation are more harmful
than shoulder less ones – as preparations
are deeper into dentin closer to pulp
Pin restoration
• Avoid use of high speed instruments
• Insertion of pins introduce dentinal
fracture or unnoticed pulp exposures
• Deep insertion can cause pulpal
irritation
• Inflammatory reaction, necrosis
Rebound response
Bernier & Knapp
• High energy which is released by
ultrasonic cutting or by ultrahigh speeds
• When cavity prepared at one side of
tooth reaction occur on opposite side
• Stanley,Langeland controversy exist
about actual occurance
Polishing of restorations
• Polishing of rest with out taking precautions for
dissipation of heat is dangerous to pulp
• Elevation of temp because of friction,
sandpaper, disc, rubber cups run at high speeds
can generate sufficient heat to damage the
pulp
• Heat generated can cause enamel to fracture
• Polishing inst should run intermittently at low
speeds or in conjunction with coolants
CHEMICAL IRRITANTS
DENTIN STERILIZING AGENTS
• Phenol : cytotoxic, poor sterilizing agent
increase permeability of dentin tubules
• Silver nitrate : causes irritation to pulp –
inflammation reaction
• Camphorated Parachlorophenol : pulpal
inflammation
Cleansing and drying medicaments:
• Smear layer removal
• Enhances bonding of resin
Hydrogen peroxide – formation of emboli in pulp
• Potentially damaging
• Rupture of blood vessels
35% H2O2on enamel – severe but reversible
changes.
Alchohol : Injures odontoblasts
• denatures protein
Drying of cavity by rinsing with warm water and
rubbing with cotton pellets produce least
damage
Acid etchants
• Pashley : Increase dentin permeability
• Allow penetration of streptococcus mutans into
dentinal tubules
• Rated as mild to moderate reaction
• Use of Ca(OH)2 base or liner before
pretreatment
• Rapid buffering of acid by dentinal fluid is
Negligible
• Reversed by 3% solution of potassium hydrogen
oxalate
VITAL bleaching tech
For RCT Treated teeth
THERMO / PHOTO B
Walking B
MOUTHGUARD B
Thermo catalytic B
Laser – Activated B
UV Photo Oxidation B
Pulpal response to THERMO / PHOTO B
• Common immediate postoperative problem is
PULPALGIA characterized by intermittent
shooting pain [during or after].
• Persists for bet 1 & 2 days.
• Intensity → duration & temp of B procedure.
• Shorter B Periods recommended.@
Max 30 min.
• Reversible if adequate B agents & tech used
Dan Nathanson JADA 1997,128,41S-44s.
JOE Sept 2007 Camargo et al concluded
that
• Independent of presence of restn, all
teeth submitted to B presented peroxide
penetratn into the pulp chamber.
•
The human teeth presented higher penetratn than bovine teeth.
• Peroxide penetratn into the pulp chamber
of restored teeth depend on type of
restorative material; it is higher in teeth
restored
with
Resin
[↔Composite resin,GIC].
modified
GIC
Pulpal response to vital bleaching
Ritter et al
10% CP for 6 weeks was safe for the pulp
up to 10 years post operatively.
J Esthet Restor Dent 2002;14:275-85.
If minor inflammatory changes observed, it
will be reversible by fluoride application
[Neutral NaF gel for 3 to 5 min].
Effects of bleaching on pulp
• Pulp penetration during bleaching vary
among commercial 10% carbamide
peroxide Resulting in diff level of tooth
sensitivity or bleaching efficacy
• Potential for pulp damage as result of
enamel and dentin penetration
• Cooper et al - pulp penetration can occur
with in 15 mins
• Less penetration from carbamide
peroxide than H2O2
• 3% solution of H2O2 cause a transient
reduction pulpal blood circulation and
occlusion of pulpal blood vessels
• Most common side effect experienced
by patients is transient, mild temp
sensitivity
• to achieve faster whitening, frequency
is inc which inc sensitivity
• More dose related than pH related
Effects of vital bleaching on pulp histology.
• Researchers have observed that vital
tooth bleaching produces histological
evidence of minor inflammation of
superficial layers of pulp.
• minor inflammatory response is
proportional to the pain response.
• The histological and immunostaining
studies confirm that the response of
pulp to bleaching appeared self-limiting.
• Evidence of pulp inflammation did not
worsen with increased time of
bleaching, and in all cases, responses
appeared self-resolving
• Studies support that controlled home
bleaching is safe to pulp
EFFECT OF
LASER
ON
PULP
LIGHT AMPLIFICATION BY
STIMULATED EMISSION OF
RADIATION
• CO2 Lasers : Excessive thermal heat,
dentin permeability ↑d significantly.
utility
&
safety
on
hard
tissues ?
• Nd :YAG = Neodynium : yttrium aluminum
garnet
• NdYAG with 1064 nm wavelength (white et
al) is safe for the human pulp when used
with in safe parameters
• when applied to one area for more than
10sec significant structural damage is
caused.
• when lasing for longer than 15 sec,
crater resulted (almost exposing the
pulp)
• Pulp damage includes nerve injury &
hemorrhage leading to irreversible
damage.
Er : YAG
Clinically cavity prep by
Er:YAG lasing is safe to the
pulp than Nd:YAG & diode
laser systems.
PREVENTION
CUTTING PROCEDURES:•
use light, intermittent cutting,
an efficient cooling system & high
speeds of rotation
• AVOID DESICCATING THE
DENTIN.
• Do not overdry the cavity preparation
• Establish a patient recall system that
ensures periodic evaluation of the
status of pulps that have been
exposed to injury
 Pathways of the pulp, Stephen Cohen, Richard C. Burns, 8th & 9th
ed.
 Endodontics, Ingle & Bakland, 5th ed& 6th ed
 Seltzer’s The Dental Pulp, Samuel Seltzer & J.B.Bender4th Ed.
 Endodontic Therapy, Franklin S. Weine, 6th ed.
 Dynamic Aspects of Dental Pulp, Chapman & Hall.
 JOE
 JADA &J of Esth Rest Dent.
 OD-Modern theory & Practice, M.A.Marzouk
 Art and science of operative dentistry,sturdevant,5th ed
THANK YOU