Resident’s Name: Jessica Wilson

Program: Lutheran Medical Center - Providence

Article title: Bleaching of Nonvital Teeth, A Clinically Relevant Literature Review

Author(s): Zimmerli et al.

Journal: Schweiz Monatsschr Zahnmed?

Year. Volume (number). Page #’s: 2010. 120(4). 306-313.

Major topic: Bleaching

Overview of method of research: Literature Review

Purpose:
Review current literature presenting the etiology if tooth discolorations, different treatment techniques, their degrees of success and risks of bleaching procedures.

Materials & Methods:
A PubMed literature search was performed and predominantly articles from the last 10 years were analyzed.

Findings:
1. Etiology of Intrinsic Discolorations
A. Pre-eruptive causes: medications (tetracycline), metabolism (fluorosis), genetics (AI, hyperbilirubinaemia), trauma.
B. Post-eruptive causes: pulpal necrosis, intrapulpal hemorrhage, residual pulp tissue after endo treatment, endo materials, filling materials, root resorption, aging process.
a. hemorrhage after trauma is the most common cause as blood enters dental tubules and decomposes into hemosiderin, hemine, hematin and hematoidin. Pulpal necrosis can also produce these products.
b. protein degradation products
c. calcification of the pulp (often follows trauma, erosion, abrasion or other iatrogenic irritations)
d. combinations of irrigants such as NaOCl and chlorhexadine or Biopure MTAD
e. CaOH, MTA and sealers

2. Mechanism of bleaching
A. Long chain organic pigment molecules are oxidized into smaller, lighter C, water and oxygen
B. Some manufacturers also recommend heat or light, but these can lead to root resorption

3. Bleaching Agents: in Switzerland products >6% hydrogen peroxide (or equivalent) for professional use
A. hydrogen peroxide- used with caution in high concentration (>30%) to avoid root resorption
B. sodium perborate- when water is added H2O2 is released, same bleaching effect
C. sodium percarbonate- mixed with water to produce H2O2, but clinical studies still lacking
D. carbamide peroxide- organic cmpd containing H2O2 and urea, equal effects as H2O2

4. Indications for Internal Bleaching
A. Discolorations due to metal ions (silver pins or alloys) not reliably bleachable
B. Symptoms free endodontically treated tooth with a sealed root canal filling (base material)
a. perforation restorations must also be sealed as MTA exhibits reduced marginal seal when in contact with bleaching agents
C. Sufficient coronal restorations

5. Root Resorptions
A. When only thin dentinal walls remain, it is recommended that only low concentrations of bleaching agent are used in order to prevent the material from entering the periodontal space causing inflammation and subsequent root resorption
B. Incidence reported between 1-13%, the exact etiology has not been explained
C. Heat is generally not recommended as increases in root resorption are seen.

6. Recurrence
A. Recurrence rates are relatively high
B. One study reported that after a 5 year observation period, 75% of dentists judged a case successful while 98% of patients were satisfied.

7. Technique: Pre and post treatment photos should be documented.
A. Walking Bleach technique
a. The access made and 2-3mm subginival filling material is removed and sealed. Sodium perborate is mixed with water or H2O2 and inserted into the access as a paste and a temporary closure material is applied. Cavit and Coltosol have been shown to work the best. Optimal timing for re-eval has been shown to be 33 hours for young patients and 18 hours for older patients. Sometimes CaOH is recommended to counteract the increased permeability of the dentin and raise the low pH, but the authors find little clinical relevance for this as dentin has a great buffering capacity. Ascorbic acid solution can promote normal adhesive bond strengths prior to restoration placement.
b. H2O2 has been shown to have detrimental effects on the microhardness of enamel and dentin whereas sodium perborate has not.
B. Inside/Outside Bleaching
a. One advantage is that low concentration of bleaching material is required. A vacuum formed splint is fabricated on a model where the adjacent teeth have been slightly ground down to ensure a tight fit and to prevent accidental exposure to bleaching agent. 10% carbamide peroxide is placed once the tooth has been accessed and the splint is worn at night and the patient is to return for re-eval every 2-3 days. One week later a definitive restoration is to be placed.
b. One obvious downside to this treatment is patient compliance as well as lack of bacterial control during bleaching. Although initial results may be better in the first few days, after 6 months and rehydration of the tooth the results are similar to those of the walking bleach technique.
C. In-Office Bleaching
a. This method is well known, but offers the least predictable long-term results as much of the color change is due from the dehydration of the teeth with the rubber dam.
b. Rubber dam is placed, 30% H2O2 is placed onto and in the tooth for 15-20 minute periods which can be repeated as necessary. The definitive access closure should be performed at a subsequent appointment as a large amount of H remains in the cavity

Key points/Summary:
There is relatively low risk with bleaching endodontically treated teeth and it is a valuable option when appropriately indicated. However, cervical root resorptions can occur more frequently with higher concentrations of bleaching agent, past trauma and the application of heat. It is also important to notify patients of the relatively high recurrence rate and possible risks involved.

Assessment of Article: This was a great review of bleaching nonvital teeth and very applicable clinically. I had heard of some of these techniques, but it was great to read the overviews and compare them side by side.