#D3/S2/W10
#Endo

Causes of Discolouration

External

• compounds absorbed onto pellicle or via affected colour chemical interaction with tooth surface
• associated with dietary chromogens, cationic antiseptics, metallic salts
  Internal
• originates from within pulp chamber
• systemic
  • tetracycline, fluorosis
• local
  • pulp necrosis, calcification, intrapulpal haemorrhage, pulp tissue remnant, endo materials, coronal resto material, root resorption, aging

Pulp necrosis

• release of tissue disintegration by products permeating dentine tubules (including tissue remnants in pulp horns etc)

Pulp non necrosis

• pulp canal calcification, ageing, invasive cervical resorption (pinkish)

Internal (pulp canal calcification)

• darker hue, almost always yellow, loss of translucency
• complicated tx paln decision wise
• 

Endo materials

• ledermix, dark grey brown discolouration regardless of sunlight exposure
• sealer: grey if not removed from coronal pulp chamber walls
• MTA: grey, mechnism not understood
  • other bioceramics dont cause staining
• pulp tissue remnants

General dental materials

• metallic resto
• leakage around adhesive tooth coloured material

Internal )trauma related

• following intrapulpal haemorrhage leading to accumulation of haemoglobin, appears grey after regraction through dentine and enamel
• can be reversible but not if necrosis occurs

Mechanism and action of bleach

• hydrogen peroxide is a strong oxiding agent, breaking down into free radicals which reduce or cleave double bonds of macromolecules into smaller molecules that are less pigmented and more diffusible
• hydrogen peroxide may also open carbon rings of pigments and create lighter chains
• 
• carbamide peroxide (urea hydrogen peroxide)
  • available 3-15%, yields approx 1/3 h2o2 by percentage
  • commercial prep include some glycerine, soidum stannate and acid
  • 
• sodium perborate
  • water fre h2o2, comes in powder form
  • in water breaks down sodium metaborate, h2o2 and oxygen

Internal Bleaching

Procedure (walking bleach)

• orifice barrier?
• resto material 2mm below CEJ up to CEJ
  • advocated by many to reduce risk of invasive cervical roto resorption and to prevent penetration of bleaching materials into root filling
• cavity refined but removing pulp horns ( and materials/debris) and removal of GP just below gingival margin (or 2mm lower if orifice barrier being used)
• GP removal can be done with no3 Glidden or size 90 pulp bur
• 
• prepare and place bleach
• coronal seal over bleach (prevent bacterial ingress and loss of bleach)
• pre etch can help clean but does not improve diffusion
• Cavit
• good seal asd long as it isnt occlusaly loaded, though what thickness requires is uncertain
• after bleaching is good definitive coronal seal essential for stability

Diffusion of hydrogen peroxide

• can diffuse from pulp chamber to external root surface
• diffusion speed is debated, as is duration of bleach
• recommendations between 3 days - 2 weeks, anecdotally 2 weeks is standard
  Effectiveness
• bleaching effect not diminished with perborate and water compared to 30% peroxide but may take longer and need more changes
• possibly affected but age (tubule thickness) almost certain affected type duration intensity of discolouration
• recurrence significant 10% at 2 years, leakage possibility but mechanism not understood

Case selection

• tooth and patient factors considered
• tooth
  • likely cause of discolouration, history of sensitivity, history of resorption
• patient
  • expectations, possibility of prostho management in addition to bleach, pre and post op photo

Complications

• external invasive cervical root resorption (EICR)
  • insidious resorption, hyperplastic in nature, require complex treatment with poor outcome
  • incidence varies but marked increased when peroxide and heat used
  • Controversy
    • aetiology still unknown
    • bleaching case with EICR almost always have additional risk like trauma history or ortho treatment hist

Effects of bleaching on hard tissues

Changes

• enamel
  • reduced microhardness and increased surface roughness but same as fruit juice, mechanism not understood
• dentine
  • vary evidence but likely some minor negative morphologic chemical and biomechanical effects
• GIC
  • uncertain, contradictory evidence about microhardness
• GIC bonding
  • uncertain
• composite
  • minor change in porosity, surface roughness, reduction in surface hardness
• enamel bonding
  • significant reduction in bond strength
• dentine bonding
  • no effect
• margin quality
  • likely of minimal clinical significance

Improving bond strength in resin composite

• 1 day - 3 weeks for bond strength to return
• various chemicals have been tested but not shown effective
• likely unnecessary to take any additional steps to improve bond strength prior to definitive resto