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 »  Home  »  Endodontic Articles 4  »  The perceived benefit of endodontic retreatment
The perceived benefit of endodontic retreatment
Introduction - Materials and methods.



T. Kvist & C. Reit
Department of Endodontology and Oral Diagnosis, Faculty of Odontology, Göteborg University, Gothenburg, Sweden.

Introduction.
Several investigators have focused attention on the substantial variation amongst clinicians in the management of symptom-free periapical lesions in endodontically treated teeth (Smith et al. 1981, Reit & Gröndahl 1984, 1988, Petersson et al. 1989, Hülsmann 1994). Various aspects of the endodontic retreatment decision-making process have been explored (Reit et al. 1985, Petersson et al. 1989, Reit & Kvist 1998) and a theory explaining dentist behaviour has been suggested. In a ‘Praxis Concept theory’ (PC theory), Kvist et al. (1994) proposed that dentists perceive periapical lesions of varying sizes as different stages on a continuous health scale, based on their radiographic appearance. Inter-individual variations could then be regarded as the result of the choice of different cut-off points on the continuum for prescribing retreatment.

Assessment of clinicians inclination to re-treat.
On the basis of PC theory, Kvist et al. (1994) developed a technique for assessing and numerically expressing the inclination of a dentist to propose endodontic retreatment. It was assumed that their disposition could be summed up in a ‘Retreatment Preference Score’ (RPS). The RPS is based on the judgement of five periapical conditions in root-filled teeth (Fig. 1). These conditions are described in six cases presented as line drawings of simulated radiographs. For each case the individual’s cut-off point for retreatment is determined and scored between 0 and 1. The mean value is given as the RPS. Hence, the higher the value, the higher the inclination to re-treat. The RPS has been found to be subject to large interindividual variation amongst inexperienced decision makers (Kvist et al. 1994). The situation amongst experienced endodontists is not known.
The RPS may be influenced by several factors but the PC theory suggests that an individual’s placement of the cut-off point depends to a large extent on his/her personal values. It has been proposed that the value of endodontic retreatment lies in its contribution to a person’s well-being (Reit & Kvist 1998). Well-being has been defined as ‘the fulfilment of informed desire’ (Griffin 1986) and is concerned with what an individual regards as ‘good’ in life. In the present study it was suggested that, in endodontic retreatment decision making, these values are significantly related to the ‘goodness’ of an action, that is, the benefit a retreatment procedure might bring to a patient.

Figure 1. Assessment of the retreatment preference score (RPS). Five periapical conditions were positioned on a health continuum, with 'no lesion' and 'big lesion' at either end. For each case a cut-off point on the continuum was identified separating conditions requiring retreatment from those not requiring retreatment. The score of a case could vary between 0 and 1, with a higher RPS indicating a higher retreatment preference.

Assessment of the retreatment preference score
Figure 2. An individual may benefit from endodontic retreatment by moving from a state with an asymptomatic lesion (health state B) to a state where the lesion has healed (health state A). The numerical difference in assigned U-values was defined as the 'retreatment benefit' (RTB).

individual may benefit from endodontic retreatment

It is thought that there is a close connection between a person’s values and his value judgements (Österman 1995). The idea of systematic inclusion of value judgements in clinical decision making was introduced by Ledley & Lusted (1959) and discussed in detail by Lusted (1968) and Weinstein & Fineberg (1980). This approach is based on rational choice theory (for reviews see Hargreaves Heap et al. 1992, Bacharach & Hurley 1994). Within this theoretical framework ‘utility values’ ( U - values) are produced. A U -value represents the value a person assigns to a certain health state. This value can be numerically expressed using certain techniques (von Neumann & Morgenstern 1947, Torrance 1986) and placed on a scale ranging from ‘perfect’ health (given a value of 1) to ‘death’ (given a value of 0). This type of scale was transposed to an endodontic setting by Reit & Kvist (1998) (Fig. 2).

Assessment of retreatment benefit.
When a patient moves from a worse to a better health state he or she benefits, from a medical point of view. Thus, a patient potentially benefits from endodontic retreatment if he/she moves from a health state with a periapical inflammation to a postretreatment situation where the lesion has healed. In this model the distance on the scale between the two health states (the numerical difference in assigned U -values) will define the ‘retreatment benefit’ (RTB). RTB has been found to vary substantially amongst inexperienced decision makers (Reit & Kvist 1998) but the situation amongst endodontic specialists is not known. If U -values constitute a significant part of the personal values, the PC theory suggests that variations in RPS could be explained by variations in RTB.
In the present study the hypothesis that the PC theory describes the decision making strategy of endodontic experts was tested. The validity of the proposition that RPS and RTB are causally related was also investigated.

Materials and methods.

Endodontic experts.
Sixteen dentists (nine women and seven men) affiliated with the Departments of Endodontology at the dental schools in Gothenburg (7), Malmö (5) and Stockholm (4), Sweden, were enrolled to serve as decision makers. The mean age of the group was 47.

Assessment of Retreatment Preference Score (RPS).
Written forms presenting data on six cases of endodontically treated teeth were provided. Line drawings of simulated radiographs depicting the quality of root fillings and the presence or absence of posts and crowns were systematically varied. In each case five periapical conditions were judged (Fig. 1). An identical clinical history accompanied each case:

  • The patient is 45 years old, in good general health and presents with a full set of teeth except for third molars. There are no symptoms from the teeth or oral tissues. The ‘radiographs’ were taken at a routine examination. The root-fillings are more than 4 years old. This is your first examination of the patient, who has no other dental problems, and no further dental treatment is being planned.

The examiner was asked to select one of the following five options for each case and periapical condition: no therapy, wait and see, non-surgical retreatment, surgical retreatment, or extraction. A ‘cut-off point’ was identified for each examiner and case to separate periapical conditions that were not selected for retreatment from those selected for retreatment. The cut-off point was numerically represented in the ‘retreatment preference score’ (RPS) on a scale from 0 to 1, with the higher values indicating a higher retreatment preference. The scores were: 0 = no retreatment selected, 0.2 = cut-off point at ‘big lesion’, 0.4 = cut-off point at ‘medium size lesion’, 0.6 = cut-off point at ‘small but clearly visible lesion’, 0.8 = cut-off point at ‘widened periodontal contour’, 1 = cut-off point at ‘no lesion’ (Fig. 1). The individual mean RPS of the six cases judged was calculated.

Assessment of U –values.
Two different dental health states associated with maxillary incisors were presented to the decision makers as radiographic images printed on paper. The prints were accompanied by the following texts:

  • State A : ‘Imagine that this is a tooth in your own mouth. The tooth has a good-quality root filling. There are no clinical symptoms or any radiographically visible signs of periapical pathology. The situation is not expected to change for the rest of your life.’
  • State B : ‘Identical to state A except that the radiograph shows a 5-mm large periapical radiolucency.’

The standard gamble technique (von Neumann & Morgenstern 1947, Torrance 1986) was used to give each subject a choice between two alternative courses of action. The options available were to continue living in the state of health described in the scenario, or to take a gamble that had two possible outcomes: a ‘best’ outcome or a ‘worst’ outcome.
In this study, the ‘best’ outcome was a hypothetical immediate restoration of perfect pulpal and periapical health and was given a utility of 1.0. The ‘worst’ outcome was an immediate loss of the tooth, which was given a utility of 0. For each health state (A and B) the probability of attaining the best outcome was systematically varied until the subject was indifferent to continuing to stay in that health state or taking the gamble. The probabilities were varied using a questionnaire where they were graphically illustrated with pie charts, and the utility of the health state was calculated as described previously (Reit & Kvist 1998). Negative utilities were accepted (Torrance 1984), but for calculations and representation in tables and figures such assessments were set to U = 0.

Calculation of retreatment benefit (RTB).
An individual’s potential retreatment benefit was defined as the numerical difference between the U -values of health states A and B (Fig. 2).

Judgement procedures.
Procedures to obtain RPS and U -values were carried out individually in the presence of one of the authors (TK). Procedures were repeated after 1 year; the experimental layout is shown in Fig. 3.

Figure 3. Experimental setup. The Retreatment Preference Score (RPS) and the retreatment benefit (RTB) were assessed by 16 endodontists on two occasions with a one-year interval.

Retreatment Preference Score

Statistical methods.
Descriptive measures were given as means, standard deviations (SD), medians and ranges. Spearman’s rank correlation coefficient ( r s ) was used for correlation analyses. The intrarater reliability between assessments was expressed as standard deviations of the differences between first and second assessments and limits of agreement (Bland & Altman 1986). The Wilcoxon Signed Rank Test for matched pairs was used to test systematic changes between assessments. All hypothesis tests were two-tailed and conducted at the 0.05 level of significance.