Fractured instrument

1 If fractured instrument could not be retrieved, but was bypassed, would success rate be affected?

2 In this case, provided that sterile field was maintained, what factors would influence success?

3 How long should we wait before restoration? What are the factors that influence follow up schedule?

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Success vs Healing

Firstly, scientific discussion needs to be specific.  We need terms that are not easily misinterpreted, that don’t mean different things to different people.  Success can be many things.  Patients may think of success as no pain. Clinicians, on the other hand, may think of success as tooth retention. In the field of implant, success may mean implant retention, while in endo, success may mean healing of apical radiolucency. Secondly, success is a value-laden term.  The opposite of success is failure. There’s negative connotation to failure, at least to general public. The term is screaming for someone to be blamed. Treatment deals with biological processes. Even though the treatment is done to the highest possible standard, that doesn’t mean it will work as planned. There are things that are beyond our controls. This point should be conveyed in a subtle manner through the use of non-value-laden terms. 

Healed, healing and disease are recommended terms to be used to categorise treatment outcome in endodontics (Friedman’02). They are objective, descriptive, specific, neutral and not value-laden like success. Treatment outcomes in endodontics is generally measured by healing rates i.e. the number of cases with disappearance of apical radiolucency at one-year review divided by the number of total cases.

1 If fractured instrument could not be retrieved but was bypassed, would healing rates be affected?

There are two ways to approach this question.  One through evidence and the other through logic. 

A quick check on pubmed for literature that looked into the treatment outcome of bypassing a fractured instrument amounts to nothing. This is by no mean an exhaustive search, but I don’t think there’s specific literature/evidence addressing this question directly. It is expected that such study would be difficult to come by as fractured instrument is a rare event, successfully bypassing an instrument can be even rarer, documenting all these is very difficult, to say the least. If there’s no evidence directly answer this question, we probably have to resort to logic to answer this question.

It’s reasonable to say that treatment of a disease is essentially the removal of the cause of a disease. Given that bacteria is the cause of endodontic disease, if bacteria is removed, disease should be cured. Bypassing a fractured instrument allows cleaning and disinfection of the root canal system, the cause is, therefore, removed. As long as fractured instrument is bypassed, canals are enlarged to proper sizes, antibacterial irrigant goes down canals and obturation is done properly, treatment particulars are not different from any other conventional cases, healing rates, therefore, shouldn’t be any different. The problem is not a fractured instrument per se, but bacteria.

2 In this case, provided that sterile field was maintained, what factors would influence healing rates?

We are talking about prognostic factors here. The only universally accepted prognostic factor in endodontic treatment is preoperative apical radiolucency. Teeth with apical radiolucency, in general, have lower chance of healing than teeth without apical radiolucency. So this should be applicable to cases with successfully bypassed fractured instrument as well.

3 How long should we wait before restoration? What are the factors that influence follow up schedule?

The first question is discussed in more details here. As fractured instrument is bypassed, there’s no reason to treat these cases differently from any other normal cases.

Sources:

Friedman S. Prognosis of initial endodontic therapy. Endodontic Topics 2002: 2: 59-88