IATROGENIC EFFECTS ON THE DENTAL PULP 1.Local Anesthesia 2.Cavity/Crown Preparation 3.Dental Materials 4.Depth of Preparation 5.Specific Materials 6.Vital Tooth Bleaching PROTECTING THE PULP FROM THE EFFECT OF MATERIALS VITAL PULP THERAPIES

1. Endo bookreading
CH2 Protecting the Pulp,
Preserving the Apex
Reporter:int 鄭家懋
Instuctor:VS 張淑芳
VS 錢正原
Date: 103/11/04

2. Chapter outline
 DEFINITIONS
 IATROGENIC EFFECTS ON THE
DENTAL PULP
1.Local Anesthesia
2.Cavity/Crown Preparation
3.Dental Materials
4.Depth of Preparation
5.Specific Materials
6.Vital Tooth Bleaching
 PROTECTING THE PULP FROM
THE EFFECT OF MATERIALS
 VITAL PULP THERAPIES
 THE OPEN APEX

3. Pulp Protection
 Threat to the healthy pulp→
dental caries and the treatment of dental caries
 Heat, desiccation, toxicity of restorative materials,
leakage at the margins
 When dental caries is present→ pulp is inflamed, even a
white spot lesions
 Restorative procedures →
restore the mechanical integrity and appearance
protect the pulp from further damage

4. Pulp Therapy
Direct pulp cap A dental material placed directly on a
mechanical or traumatic vital pulp exposure
Pulpectomy The complete surgical removal of the vital pulp
Pulpotomy The surgical removal of the coronal portion of a
vital pulp as a means of preserving vitality of
the remaining radicular portion is usually is
performed as an emergency procedure for
temporary relief of symptoms or therapeutic
measure

5. Pulp Therapy
Apexification Inducing a calcified or artificial barrier in a
root with an open apex or the continued
apical development of an incompletely
formed root in teeth with a necrotic pulp
Apexogenesis A vital pulp therapy procedure performed
to enable continued physiologic
development and formation of the root end;
term frequently used to describe vital pulp
therapy that encourages the continuation of
this process

6. IATROGENIC EFFECTS ON THE
DENTAL PULP

7. Local Anesthesia
 containing vasoconstrictors
 blood flow is reduced to less than half of its normal rate
and much effective
 the rate of oxygen consumption in the pulp is relatively
low
 pulp cells can produce energy anaerobically
 Survive episodes of ischemia lasting for 1 hour or more

8. Cavity/Crown Preparation
 Revolving bur contacts tooth → frictional heat
 Dentin is an effective insulator
 But! if the thickness of dentin is less than 1.0 mm or
not enough water coolant
 “boiling” away dentinal tubule fluid at the dentin
surface

9. Cavity/Crown Preparation
 The “blushing” of dentin during cavity or crown
preparation
 without the use of a coolant→vascular stasis and
thrombosis
 The amount of heat produced
 Sharpness of the bur
 Pressure
 Time

10. Cavity/Crown Preparation
 The safest way to prepare tooth
 use ultra-high speeds of rotation with an efficient
water cooling
 light pressure
 intermittent cutting
 air-water spray
 Hand instruments and low-speed cutting are
relatively safe ways
 laser

11. Cavity Depth/Remaining Dentin Thickness
 The deeper the cavity the greater the tubular surface
cause toxic substances can penetrate easily
 The longer of the dentinal tubules→ substances will
be diluted and buffered by the dentinal fluid
 remaining dentin thickness of 1 mm is usually
sufficient
 tertiary dentin is formed most rapidly when the
remaining dentin thickness is between 0.5 and 0.25
mm

12. Cavity Drying and Cleansing
 A prolonged blast of compressed air aimed onto
dentin →rapid outward movement of fluid
 Cause strong capillary forces
 Rapid outward fluid movement may also result in
odontoblast displacement
 odontoblast undergo autolysis and disappear

13. Cavity Drying and Cleansing
 replaced derived from stem cells deeper in the pulp
 Drying agents with rapid rate of evaporation
 Cavities should be dried with cotton pellets and
short blasts of air

14. Etching Dentin
 Cutting dentin results in a smear layer
 Impervious to bacteria, but is not a barrier to
bacterial products
 Interfere with the adherence
 Dissolution the smear layer opens the dentinal
tubules and increasing the permeability of dentin
 May reduce microleakage

15. Impressions, Temporary Crowns, and
Cementation
 Rubber base and hydrocolloid materials do not
injure the pulp
 Modeling compound may be damaging as a result of
the combination of heat and pressure
 Polymerization of autopolymerizing resins
 Provisional crowns fabricated→ 𝑀𝑢𝑠𝑡 𝑛𝑒𝑒𝑑 𝑐𝑜𝑜𝑙𝑎𝑛𝑡
 Postoperative sensitivity→ Microleakage
 Cement compresses the fluid→ strong hydraulic
forces

16. Polishing Restorations/Removing Old
Metallic Restorations
 frictional heat may be generated during the polishing
 Remove metallic restorations also can produce of
frictional heat
 Especially amalgam or other metallic restorations
can causes temperature increase of up to 20° C
 Polishing should be at low speeds using intermittent
pressure and a coolant
 Need combination of water and air

17. Postrestorative Hypersensitivity
 This may be due to any of the factors previously listed
 If pain is prolonged… pulpitis may have been
exacerbated
 If delayed in onset by days… microleakage!!
 restoration with modern composites may absence
of postoperative sensitivity

18. Postrestorative Hypersensitivity
 desensitizer does not reduce the incidence of sensitivity
 deep carious cavities→ Self−etching, self−priming
 If pain is evoked by biting… restoration may be exerting
a strong shearing force on the dentin walls
 does not injure the pulp but may cause a transient
hypersensitivity

19. Dental Materials

20. Cytotoxicity
 Certain restorative materials are composed of
chemicals-ZOE, ZPC…etc
 Intervening dentin limits the ability of such material
reaching the pulp
 The problems of these materials were a result of high
degree of shrinkage and cause microleakage
 the thickness and permeability of dentin affect the
response to the material

21. Cytotoxicity
 Materials are more toxic when they are placed
directly on an exposed pulp
 A set material may differ in toxicity from an unset
material
 The immediate pulpal response to a material is much
less significant than the long-term response
 The best measure of long-term response is the
thickness of tertiary dentin

22. Heat on Setting/Desiccation by Hygroscopy
 luting cements generate heat during setting
 Most exothermic luting material is zinc phosphate
 Some hygroscopic materials may cause injury by
withdrawing fluid from dentin
 But cause less damage than during cavity drying

23. Specific Materials

24. Zinc Oxide–Eugenol
 Has many uses in dentistry
 Antibacterial properties, pain control
 It is toxic when placed in direct contact with tissue
 When use in cements, it does reach the pulp
 The release of eugenol is by a hydrolytic mechanism
 Provides a tight marginal seal

25. Zinc Phosphate Cement
 ZnOP is a popular luting and basing agent
 High modulus of elasticity
 Cementation of castings with ZnOP is well tolerated
by the pulp
 More likely to produce pulpal sensitivity than GIC
 But no difference after 3 months

26. Restorative Resins
 Early adhesive bonding and resin composite systems
contract cause gross microleakage
 Composites absorb water and expand
 To limit microleakage and improve retention
→ beveled and acid etched
 recently developed hydrophilic adhesive bonding
composite systems

27. Glass Ionomer Cements
 Originally used as esthetic restorative materials
 Placed on exposed pulps in noncarious teeth, glass
ionomer cement of bacterial microleakage similar to
resins but less than calcium hydroxide cement
 The incidence of severe pulpal inflammation or
necrosis on exposed healthy pulps…
 If a narrow remaining dentin thickness…
 When used as a luting agent…

28. Amalgam
 Amalgam alloy is still a widely used material for
restoring posterior teeth
 Shrinkage, corrosion
 Amalgam is the only restorative material in which
the marginal seal improves with time
 In deep cavities in posterior teeth, composites are
associated with more pulpal injury than amalgams
because of microleakage

29. Vital Tooth Bleaching
 external bleaching with 10% carbamide peroxide
may causes mild pulpitis
 But can reversed within 2 weeks
 Both short-term and long-term clinical observation
on bleached teeth report no significant pulpal
changes

30. PROTECTING THE PULP FROM
THE EFFECT OF MATERIALS

31. Cavity Varnishes, Liners, and Bases
 Liner, to improve the overall performance of a
restoration
 main concern is to reduce or eliminate microleakage
 One 3-year clinical study, whether there is a liner or
not, the result is same
 In reduce dentin permeability, Bases provide the
largest reduction, varnishes the least

32. “Insulating” Effect of Bases
 A common misconception is the necessity of placing
an insulator beneath metallic restorations
 protect the pulp from thermal shock
 Dentin is an excellent insulator
 Thick cement bases are no more effective than just a
thin layer of dentin

33. VITAL PULP THERAPIES

34. VITAL PULP THERAPIES
 Maintaining an intact healthy pulp is preferable to
root canal treatment
 Dealing with a deep carious lesion→indirect pulp
capping
 carious exposure→ direct pulp capping
 Others procedure, removal of inflamed pulp tissue
 the remaining tissue is then covered with dressing

35. Removal of Dental Caries
 Most common cause of pulp disease
 Products of bacterial metabolism, notably organic
acids and proteolytic enzymes
 Eliciting an immune response and inflammatory
reaction
 near the pulpal wall→Don’t use high speed and Hand
instruments!!

36. Capping the Vital Pulp
 Step-Wise Excavation of Caries
caries is removed in two or three appointments
The deeper dentin may remineralize
glass ionomer base is placed
careful case selection is necessary

37. Capping the Vital Pulp
 Direct Pulp Cap
Two considerations for direct pulp capping
Differ in that the condition of the pulp
Hemorrhage controlled
Hard-set calcium hydroxide or MTA
Covered by glass ionomer cement should be followed
by a permanent restoration
The long-term success rate…

38. Pulpotomy
 When carious pulp exposures occur in young
permanent teeth, inflammation may be restricted to
the crown
 The pulp must be vital
 Carious dentin and the pulp to the level of the
radicular pulp are removed
 Control bleeding, rinsed with sodium hypochlorite

39. Pulpotomy
 capped with calcium hydroxide or MTA
 Follow-up examination should no severe pain or
swelling, internal or external resorption, canal
calcification
 Teeth with immature roots should continue normal
root development and apex formation and closure

40. THE OPEN APEX

41. THE OPEN APEX
 It is in the developing root of immature teeth
 Also develop as a result of extensive resorption of a
previously mature apex
 If the pulp becomes necrotic before root growth is
complete….
 Resultant root is short with thin and consequently
weakened dentin walls
 Provides significant challenges in the treatment of
pulpal injury
 The results of treatment are unpredictable
 apexogenesis or apexification

42. Diagnosis and Case Assessment
 subjective symptoms, clinical and radiographic
examination, diagnostic tests
 may be difficult at radiographic examination
 lesion tends to have a noncorticated, diffuse border
 comparison with the periapex of other tooth
 mesiodistal →close, buccalingual→open

43. Treatment Planning
 whether the tooth can be restored or fracture
 Patient compliance is important

44. Apexogenesis
 often the case when an immature tooth sustains a
small coronal exposure after trauma
 for up to 7 days after the traumatic incident,
inflammation is limited to the most superficial 2mm
of the pulp
 Treatment in these cases is a shallow pulpotomy
 When there is a larger exposure…

45. Apexogenesis
 Technique
Anesthesia, rubber dam
inflamed pulp tissue removed, use sharp round bur
or sharp spoon excavator
Hemorrhage is controlled
rinsed with 2.5% sodium hypochlorite
MTA, powder with sterile water or saline at a ratio
of 3 : 1
patted in place with a moist cotton pellet

46. Apexogenesis
The primary goal is to maintain pulp vitality
allowing dentin formation and root-end closure
The time required 1 and 2 years
patient should be recalled at 6-month intervals to
determine the vitality
Absence of symptoms does not indicate absence of
disease
 success rate is lower, calcific metamorphosis is a
common occurrence

47. Apexogenesis
The primary goal is to maintain pulp vitality
allowing dentin formation and root-end closure
The time required 1 and 2 years
patient should be recalled at 6-month intervals to
determine the vitality
Absence of symptoms does not indicate absence of
disease
success rate is lower, calcific metamorphosis is a
common occurrence

48. Apexification
Involves removal of the necrotic pulp and placement
of an antimicrobial medicament
 The critical factors in apical barrier formation are
thorough debridement of the root canal system and
establishment of a complete coronal seal
 Calcium hydroxide has been the most widely
accepted material for induction of an apical barrier
 Produces a multilayered, sterile necrosis permitting
subjacent mineralization
 Recently, interest has centered on the use of MTA

49. Apexification
 Technique
Anesthesia, rubber dam
removal of all necrotic tissue, H- file
Working length is established, slightly short of the
radiographic apex
maximize cleaning by copious irrigation with
sodium hypochlorite and minimal dentin removal
Large paper point
 Put MTA as barrier
patted in place with a moist cotton pellet

50. Success or Failure of Apexification
 The most common cause of failure is bacterial
contamination
 Loss of the coronal restoration, inadequate
debridement of the canal, root fracture, treatment
was not performed under strict aseptic conditions
 All patients should be recalled at 12-month intervals
for 4 years

51. Thanks for your
attention~!!