 Identify
hard tooth structures
 Mention functions of enamel, dentin and
cementum
 Define smear layer and its role
 Define iatrogenic trauma to tooth and
mention its type in oral cavity
 Describe how iatrogenic trauma can be
avoided
 Define thermogenesis
 Mention
causes of thermogenesis during an
operative dentistry procedure
 Explain how thermogenesis be controlled
 Describe effect of speed and pressure of
rotary instrument on pulp health
 Define desiccation
 Mention causes desiccation and its effects
 Describe eccentricity ,its causes and effects
Hard tissues
 Enamel
 Dentin
 Cementum
Soft tissue
 Pulp
Protection for dentin & pulp
Maintain the esthetic of the
tooth through translucency

A
good insulator of heat
 Forms reparative dentin in response
to any irritation
 Forms smear layer for protecting the
pulp (Biological importance)
Whenever dentin is cut or abraded,
a thin altered layer is created on the
surface
Few micrometer thick
 Formative
or developmental
Nutritive
 Sensory or protective
 Defensive or reparative

 Iatrogenic
Trauma
 Thermogenesis
 Speed
 Pressure
 Desiccation
 Vibration
 Pin drilling & insertion
Trauma to the tissues of oral cavity
caused by the operating dentist
 Mechanical
 Thermal
 Chemical

Use Sharp cutting instruments
completely dissipate energy applied
during the actual cutting
Avoid undue over-cutting of enamel &
dentin
it exposes more
dentinal tubules
Avoid unnecessary application of
pressure in scooping out carious
dentin to avoid pressure pain
Avoid using rotary instruments
without proper cooling
Generation of heat
The friction between the cutting tool & tooth
structure
Increased amount of pressure during cutting
by rotary instruments
 Hardness
of the tissues to be cut
(more heat generates when cutting enamel
than cutting dentin)
 Increased
area of tool to tooth contact
Type of bur (material):
Steel generates more heat than the
corresponding size carbide because steel has
lower hardness & cutting efficiency
Diamond points generate more heat than the
corresponding size carbide due to ‚their
abrasive action and wider area of tooth
contact
Use small sized burs
 Apply minimal amount of pressure
 Avoid use of eccentric tools
 Restrict use of diamond points to
enamel

Use coolant during cavity
preparation (Air-water spray)
 Never cut under dry condition at any
rotational speed

High speed produces higher amount
of heat
 Cutting under dry condition at any
rotational speed causes variable
pulp changes



Cutting with low speed instruments
requires more pressure than cutting
with high speed instruments
It induces deleterious pulp response
Injurious
 Harmful
 Destructive

Absolute dryness of dentin
Overheating of dentin during
cutting procedures
 Using chemicals as alcohol to sterile
the cavity
 Using air as a coolant or in
performing final toilet of cavity

 Sensitivity
 Pulp
pathology
 Increased Permeability of vital
dentin to any irritant
 Aspiration of odontoblasts from the
pulp toward the cut dentin at the
area of prepared cavity
Occurs due to eccentricity or run-out
of rotary instruments
Having the axis away from the center
1- Annoyance & discomfort to the
patient
2- Heat generation
3- Rebound
response:
due to increased speed of rotation,
limited area of necrosis occurs at an
area remote from the cut dentin
4- Calciotraumatic effect:
alteration areas of hyper & hypocalcification near the pulpal surface
of the cut dentin
5- Uncontrolled cutting
6- May cause cracks in enamel
7- May show different degree of pulp
changes
8- Reduction in growth rate of dentin,
absence of pre-dentin layer & formation
of irregular dentin
Sodium hypochlorite
used as canal
irrigant is toxic
ballooning,
bleeding ,
periodontal pain,
facial emphysema
and angioneurotic
edema may occur
Protective
shield
For dentist
Protective
glasses for
patients
Dentinal pins are used for extra retention of a
restoration
confine pin drilling within the elastic limit of
dentin
 Oversized pins, dull pins & clogged flutes
develop minute fracture lines or crazed
enamel

 Pin
insertion induces internal
stresses
 Injurious pin drilling may lead to
pulp exposure
 Luting cements used with cemented
pins à may irritate the pulp
 Thermal
& galvanic irritations can
be transmitted through pin to
underlying pulp
 The greater the pin diameter the
higher is the thermal conductivity