Internal Bleaching of Discoloured Teeth¹

Tooth Bleaching - Terminology²

Warning

==It is crucial to use correct terminology. The terms vital bleaching and non-vital bleaching are inappropriate.==

Internal
- → used to repalce “Non-vital”
  - i.e. Root-filled
External
- → used to repalce the term “Vital”
  - i.e. Normal pulp

Tooth Stains³

Extrinsic
Intrinsic

Essential to determine the cause of the discolouration prior to treatment

Extrinsic Tooth Discolourations

Cigarettes, pipes, cigars, chewing tobacco - yellowish-brown to black
- Staining is often worse in teeth with infractions (cracks) or exposed dentine.
Marijuana - dark brown to black rings
Coffee, tea, foods - brown to black
Poor oral hygiene - various colours
Fluorosis - White, yellow, brown, grey, and/or black

Intrinsic Tooth Discolourations⁴

Genetic conditions
- Amelogenesis imperfecta - brown, black
- Involves improperly formed enamel, typically affecting all teeth.
Systemic Conditions
- Jaundice - blue-green or brown
- Porphyria - purplish-brown
Medications during tooth development
- Tetracyclines, fluoride - many colours
If taken during tooth development, tetracyclines can cause distinct grey or black bands of discolouration within the tooth structure.
Body by-products
- Bilirubin - blue-green or brown
- Haemoglobin - grey, black
  - A common cause is internal haemorrhaging of the pulp following trauma.
Pulp changes
- Pulp canal calcification (PCC)
  - Increased dentine thickness - yellow
  - The increased thickness of dentine determines the tooth's shade.
- Pulp necrosis (PN)
  - With haemorrhage - grey, black
    - Release of haemoglobin and iron
    - e.g. trauma
  - No haemorrhage - grey-brown
    - Protein degradation products
Iatrogenic causes
- Trauma during pulp removal
- Pulp tissue remnants in pulp chamber
- Restorative materials
  - Amalgam, composite, gold, pins, etc
  - If marginal breakdown these materials lead ot discolouration
- Endodontic materials
  - Medicaments, sealers, temp. fillings, etc.
    - ==Medicaments: Ledermix paste, containing tetracycline, can cause significant discolouration if left in the coronal portion of the tooth. - Cements: Root canal cements (e.g., AH26) can turn black when exposed to moisture over time, leading to severe tooth discolouration.==
    All iatrogenics caues usually cause brown, grey or black discolouratoin of the teeth

Extrinsic and Intrinsic Discolouration⁵⁶⁷⁸

Fluorosis
- White, yellow, brown, grey, and/or black
- Often with mottled enamel
Ageing
- Yellow
- Often with added discolouration effects of tooth wear, cracks, restorations, illness, etc

Management of Discoloured Teeth⁹¹⁰¹¹

Determine the cause of the discolouration
This will indicate the treatment approach
Intrinsic stains
- Internal Bleaching - after RCF
Extrinsic stains
- Change addictive behaviour / habits
  - If applicable
  - e.g. Smoking, chewing tobacco, coffee, etc.
- Prophylaxis
- Abrasion - air, ultrasonics, sonics
- Enamel microabrasion
- External whitening

Alternatives to bleaching and whitening

Labial veneer restorations
- Porcelain, composite resin
  - Porcelain is more colour-stable long-term than composite.
    - A key disadvantage is that adjacent natural teeth may yellow with age, creating a mismatch that requires the veneer to be replaced.

Case Example

A patient with a yellow tooth due to pulp canal calcification opted for a porcelain veneer because locating and treating the calcified canal for internal bleaching was unpredictable and risked compromising the tooth.

Crowns
- Porcelain, composite resin, acrylic
BUT: these do not remove the underlying discolouration
- The aesthetic result may be compromised

Tip

==Sometimes, internal bleaching is performed before placing a veneer or crown to lighten the underlying tooth structure, making it easier to achieve an excellent aesthetic result. In many cases, the result of bleaching is so good that a crown or veneer is no longer necessary.==

Advantages of Bleaching¹²¹³

Quick
Cheap
Predictable
Can be re-done
Conservative procedure
No change to the occlusion
Original crown form retained
Restores natural colour and translucence
No effect on the periodontal tissues
Allows stabilisation of gingivae before crowns or veneers – especially in young patients
- Ideal for young patients as it avoids placing restorations like crowns whose margins could become exposed as the gingiva matures and recedes to its stable adult position.

Disadvantages of Bleaching¹⁴

Caustic solutions
Can change the structure of tooth substance
- this is an extreme and rarely occurs
Not always permanent
claims of External invasive resorption (EIR) following internal bleaching
- Reports of an association
- But not proven

Effectiveness of Bleaching¹⁵

In Vitro internal bleaching studies¹⁶

Typical method used
- Stained with blood products
  - Erythrocyte decomposition
  - Easier to remove than other causes
  - Dental material stains are the most difficult to remove
- Considered to be easier to bleach recent stains

Range of results¹⁷

Info

A review of multiple clinical studies shows a wide range of outcomes, making direct comparisons difficult due to varying methodologies and success criteria.

“Success”
- 45–100%
“Acceptable”
- 2–58%
“Failures”
- 0–55%

In Vivo studies of internal bleaching - Some typical examples¹⁸

Longevity of Bleaching¹⁹

In Vivo studies of longevity of internal bleaching

Discolouration after Bleaching

Info

==The chemical reaction of bleaching is a one-way oxidation process; it does not reverse. Therefore, any subsequent discolouration is considered a new stain. The most likely cause is microleakage around restorations, allowing bacteria, their byproducts, and stains from food and drink to penetrate the tooth.==

Possible reasons (Howell 1981)
- Break down of restorations
  - Bacteria and their by-products
  - Food, drinks
- Permeability of tooth
  - Saliva or tissue fluid
  - Food, Drinks
- Chemical reduction of oxidation products from the bleaching agent - H₂O₂
  - Unlikely to occur: since bleaching is a one way chemical reaction

The Chemistry of Bleaching²⁰

Bleaching Materials and Methods

Oxalic acid - 1877
Hydrogen Peroxide (H₂O₂) - 1884
Electric current - 1895
Ultraviolet light - 1911
Intracoronal heat - 1913
Superoxol + electric light rays - 1918
Superoxol + Sodium Perborate - 1924
Sodium Perborate and Water - 1959
“Walking bleach” - 1963
==This is the modern recommended technique. A paste of 35% hydrogen peroxide (Superoxol) and sodium perborate is sealed inside the pulp chamber for several days.==

Internal Bleaching - Chemistry²¹

“Walking Bleach” Technique
- Hydrogen peroxide - H₂O₂
  - Superoxol - 35% H₂O₂
- Sodium Perborate - 2NaBO₂[OH]₂[nH₂O]

Hydrogen Peroxide - H₂O₂

An oxidising agent:
- Produces perhydroxyl and oxygen “free radicals”
  - Highly unstable and very reactive
Weakly acidic in pure aqueous form:
- Produces more free oxygen radicals
  - Weaker bleaching agent than the perhydroxyl radical
BUT at alkaline pH:
- Greater bleaching effect as more perhydroxyl free radical is released
- pH: 9.5 – 10.8

Sodium Perborate - 2NaBo₂[OH]₂[nH₂O]²²²³

When contact with water:
- Breaks down to produce H₂O₂ - Approx. 10%
Has alkaline pH of 10.0
- ∴ Increases the effectiveness of bleaching if used with H₂O₂
==When mixed with H₂O₂, the alkaline pH shifts the reaction to produce more of the highly effective perhydroxyl free radicals (•OOH), significantly increasing the bleaching effect. This is why the combination is recommended.==

Internal Bleaching - Chemistry²¹

Bleaching - an oxidation-reduction reaction
Agent must diffuse through the dentine
Free radicals attack organic molecules
- These free radicals diffuse through the dentine and attack the organic molecules causing the discolouration. They break down complex, pigmented carbon ring structures into simpler, non-pigmented molecules that reflect less light, resulting in a whitening effect.
- Break unsaturated bonds to create simpler molecules
  - Less absorption energy
  - ∴ Less light reflected
  - ⇒ Produces a whitening effect
Has a “saturation point”
- → Lightening effect slows dramatically
  - If bleaching continues after the stain is removed, the free radicals will start to break down the tooth's protein matrix. The saturation point is reached when the lightening effect slows dramatically.
  - Breaks down proteins & carbon-containing molecules this increases tooth brittleness and porosity
  - If continued - converts dentine & enamel to CO₂ and H₂O
ESSENTIAL to Know When to Stop !!!

An in vitro comparison of different bleaching agents in the discoloured tooth

The age of the sodium perborate powder did not affect its efficacy, as long as it was kept dry.

Recommendations:

Na Perborate - avoid moisture contamination
H₂O₂ - Use a fresh solution
- Replace supply every 6 months: track dates
- Buy a small jar only: 25 mls
- Store in brown glass jar with tight lid/seal
- Store in the fridge: cool and dark

H₂O₂ - Effects on Tooth Structure²⁴

H₂O₂ produces a precipitate on the enamel surface
Acid etch first + then H₂O₂
- More precipitate and a more porous enamel surface
H₂O₂ leaves an amorphous precipitate on dentine
Acid etch first + then H₂O₂
- Less precipitate and more tubules open
Peroxide is absorbed by both enamel and dentine during bleaching
Leaches out if left in water for a long time
Can not remove just by rinsing

H₂O₂ - Effects on Bonding Materials²⁵²⁶

- H₂O₂ significantly reduces bond strength of GIC to dentin and composite to enamel.

It can prevent measurable adhesion of composite to dentin.
H₂O₂ affects bonding resin setting and adhesion to filled resin.
Soaking in water for 7 days can restore bond strength for composite to peroxide-treated enamel, possibly due to improved surface conditioning.
Saliva may have a similar, slower effect.

Clinical Recommendations

After internal bleaching:
- Delay restoration of the access cavity and replacement of other restorations
  - For a minimum of 14 days
    - ==The speaker recommends waiting 3–4 weeks to be safe.==
    - Fill the entire access cavity with Cavit (with NO cotton pellet) for this time

External Invasive Resorption (EIR)²⁷

not clear whether IER is a side effect, only 36 cases have been reported
- very difficult to say that bleaching causes EIR

Prevalence

Total 36 cases reported 1979–2003
- But how many teeth have been bleached?
  - Probably millions!
Clinical studies: Total 701 teeth
- 8 cases of EIR (1.1%)
- *Slightly higher than the population estimate of 0.02%

Possible Factors / Mechanisms²⁸

Trauma
Base over RCF
Level of RCF removed
Heat used in bleaching
Chemical burn from O₂ and H₂O₂
- Cause coagulation and inflammation
- May lead to necrosis of p.d.l.
Cementum defect

Analysis of Reported EIR Cases

An analysis of 36 reported cases of post-bleaching EIR revealed common factors:

==No protective base was placed over the gutta-percha in 26 cases.==

==All used hydrogen peroxide.==

==22 of 26 cases used heat to accelerate the bleaching.==

==10 cases had a history of trauma (details were missing for the other 16).==

Cervical root resorption following bleaching of endodontically treated teeth

Factors associated with EIR (study in dog teeth ):

30% H₂O₂ plus heat
Dentine thickness

Factors NOT associated with EIR:

Walking bleach technique
Internal etching
H₂O₂ and Na Perborate

Na Perborate inhibits macrophages Macrophages stimulate clastic cells clastic cells are the ones that cause resorption so if they are inhibited its way less likely

Protective Effect of Sodium Perborate

Sodium Perborate may have a protective effect, as it has been shown to inhibit macrophages, which are the precursors to resorptive clastic cells.

Cementum Defect²⁸

Cemento-Enamel Junction

The anatomy of the CEJ varies:

==~65%: Cementum overlaps the enamel.==

==30%: Cementum and enamel meet edge-to-edge.==

==5–10%: There is a gap between the cementum and enamel, leaving dentine exposed to the oral environment and periodontal tissues. This gap may provide an entry point for resorptive cells to invade the tooth.==

Heithersay et al - ADJ 1994²⁹

“There is a very low, although positive, risk of EIR after bleaching – especially if there has been a history of trauma to the tooth”

Heithersay - Quintessence Int 1999³⁰

Concluded:
- “There is a very low, although positive, risk of EIR after bleaching ….
- … especially in association with other potential predisposing factors such as trauma and orthodontic treatment”

Cervical Canal Leakage³¹

Conclusions - Smith et al 1992

Info

==This study found that significant dye penetration occurred through the cervical dentine, especially on the proximal surfaces.==

2mm Cavit base was sufficient to prevent dentinal penetration of the dye
Cavit should be placed slightly coronal to labial CEJ
Cemental defects – greater dye penetration in areas of defects

An in vitro comparison of bleaching agents on the crowns and roots of discoloured teeth Warren MA, Wong M, Ingram TA. J Endod 1990; 16: 463-7

Warren et al - 1990³²

==IRM is therefore not a suitable base material for this purpose.
- as its seal against liquid penetration is questionable=

Recommendation for Bleaching Procedure³³

Why not GIC?

Glass Ionomer Cement (GIC) is not recommended as a base material for several reasons:

==Poor Seal: It does not provide an adequate seal against liquid penetration.==

==Difficult to Place: It is challenging to place and shape correctly deep within the access cavity.==

==Difficult to Remove: If any GIC gets on the labial wall, it will block the bleaching agent. Removing it is difficult without also removing tooth structure, as it requires a bur. Cavit, being a soft material, is easy to place, shape, and remove.==

RECOMMENDED to cover root canal filling with 2mm Cavit before bleaching

Recommended Procedure

Based on the evidence, the following procedure is recommended to maximize effectiveness and minimize risks:

==Remove Gutta-Percha: The root filling material should be removed to a level at least 2 mm apical to the labial CEJ.==

==Place a Protective Base: A 2 mm thick layer of Cavit should be placed over the remaining gutta-percha.==

==Shape the Base: The Cavit should be shaped into a saddle shape to reach the CEJ

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Quartz 4

Explorer

O6A Discoloured Teeth

Internal Bleaching of Discoloured Teeth1

Tooth Bleaching - Terminology2

Tooth Stains3

Extrinsic Tooth Discolourations

Intrinsic Tooth Discolourations4

Extrinsic and Intrinsic Discolouration5678

Management of Discoloured Teeth91011

Alternatives to bleaching and whitening

Advantages of Bleaching1213

Disadvantages of Bleaching14

Effectiveness of Bleaching15

In Vitro internal bleaching studies16

Range of results17

In Vivo studies of internal bleaching - Some typical examples18

Longevity of Bleaching19

In Vivo studies of longevity of internal bleaching

Discolouration after Bleaching

The Chemistry of Bleaching20

Bleaching Materials and Methods

Internal Bleaching - Chemistry21

Hydrogen Peroxide - H₂O₂

Sodium Perborate - 2NaBo₂[OH]₂[nH₂O]2223

Internal Bleaching - Chemistry21

Recommendations:

H₂O₂ - Effects on Tooth Structure24

H₂O₂ - Effects on Bonding Materials2526

Clinical Recommendations

External Invasive Resorption (EIR)27

Prevalence

Possible Factors / Mechanisms28

Analysis of Reported EIR Cases

Factors associated with EIR (study in dog teeth ):

Factors NOT associated with EIR:

Cementum Defect28

Cemento-Enamel Junction

Heithersay et al - ADJ 199429

Heithersay - Quintessence Int 199930

Cervical Canal Leakage31

Conclusions - Smith et al 1992

An in vitro comparison of bleaching agents on the crowns and roots of discoloured teeth Warren MA, Wong M, Ingram TA. J Endod 1990; 16: 463-7

Warren et al - 199032

Recommendation for Bleaching Procedure33

Why not GIC?

Footnotes

Graph View

Table of Contents

Backlinks

Internal Bleaching of Discoloured Teeth¹

Tooth Bleaching - Terminology²

Tooth Stains³

Intrinsic Tooth Discolourations⁴

Extrinsic and Intrinsic Discolouration⁵⁶⁷⁸

Management of Discoloured Teeth⁹¹⁰¹¹

Advantages of Bleaching¹²¹³

Disadvantages of Bleaching¹⁴

Effectiveness of Bleaching¹⁵

In Vitro internal bleaching studies¹⁶

Range of results¹⁷

In Vivo studies of internal bleaching - Some typical examples¹⁸

Longevity of Bleaching¹⁹

The Chemistry of Bleaching²⁰

Internal Bleaching - Chemistry²¹

Sodium Perborate - 2NaBo₂[OH]₂[nH₂O]²²²³

Internal Bleaching - Chemistry²¹

H₂O₂ - Effects on Tooth Structure²⁴

H₂O₂ - Effects on Bonding Materials²⁵²⁶

External Invasive Resorption (EIR)²⁷

Possible Factors / Mechanisms²⁸

Cementum Defect²⁸

Heithersay et al - ADJ 1994²⁹

Heithersay - Quintessence Int 1999³⁰

Cervical Canal Leakage³¹

Warren et al - 1990³²

Recommendation for Bleaching Procedure³³