A study of dentists' preferences for the restoration of shortened dental arches with partial dentures.

OBJECTIVE: This study aimed to use a utility method in order to assess dentists' preferences for the restoration of shortened dental arches (SDAs) with partial dentures. Also, the impact of patient age and length of the SDA on dentists' preferences for the partial dentures was investigated.
MATERIALS AND METHODS: Totally, 104 subjects holding a basic degree in dentistry and working as staff members in a private dental college in Saudi Arabia were interviewed and presented with 12 scenarios for patients of different ages and mandibular SDAs of varying length. Participants were asked to indicate on a standardized visual analog scale how they would value the health of the patient's mouth if the mandibular SDAs were restored with cobalt-chromium removable partial dentures (RPDs).
RESULTS: With a utility value of 0.0 representing the worst possible health state for a mouth and 1.0 representing the best, dentists' average utility value of the RPD for the SDAs was 0.49 (sd= 0.15). Mean utility scores of the RPDs across the 12 SDA scenarios ranged between 0.35 and 0.61. RPDs that restored the extremely SDAs attracted the highest utility values and dentists' utility of the RPD significantly increased with the increase in the number of missing posterior teeth. No significant differences in dentists' mean utility values for the RPD were identified among SDA scenarios for patients of different ages.
CONCLUSION: Restoration of the mandibular SDAs by RPDs is not a highly preferred treatment option among the surveyed group of dentists. Length of the SDA affects dentists' preferences for the RPD, but patient age does not.

INTRODUCTION

Current adult dental health surveys indicate a significant decline in the rate of complete edentulism and growing trend of retaining teeth later in life than ever before.[123] Such trend reflects the rapid advancement in dental care along with increased awareness of oral health among the public in our contemporary world. Thus in the near and long-term future, it can be speculated that dentists will face an increasing number of partially edentulous patients seeking replacement for their missing teeth and/or treatment for their remaining teeth. This highlights the need to efficiently prepare and train dentists to deal with the different scenarios of partial edentulism. In addition, research should be directed toward identifying the factors that may affect treatment decisions for partially edentulous patients in order to achieve better treatment outcomes.

A common partial edentulsim scenario is the shortened dental arch (SDA). This is a reduced dentition with missing posterior teeth and intact anterior teeth.[4] Such dental situation may develop in a considerable number of subjects because molar teeth are “high-risk teeth” and tend to be lost at an earlier stage than anterior and premolar teeth.[567] Kayser[4] estimated that the proportion of subjects with SDAs may reach 25% of the population in the age group 41–45 and it could become 70% in the age group 61–65.

Basically, treatment options for the management of SDAs include:

Rehabilitation of the remaining dentition and stabilizing the occlusion without replacement of missing posterior teeth. This approach of treatment is known as the SDA concept. It aims at maintaining a functional dentition comprising the anterior and premolar teeth[48]

Extending the SDA by a removable partial denture (RPD) prosthesis

Extending the SDA by a cantilevered fixed dental prosthesis (either conventional or resin-bonded)

Extending the SDA by an implant-supported prosthesis.

The debate about the most acceptable treatment option for the SDAs, functionally and esthetically, is still ongoing. Devlin[9] discussed the problems associated with making a treatment decision in subjects with free-end saddles that is, SDAs. He considered replacement of missing molar teeth in such patients as “a prosthodontic dilemma.”

The RPD can be considered as the simplest and least costly prosthetic option for the SDAs. It was found to be the most popular prosthetic restoration for the SDAs in general dental practice in the UK.[10] However, Käyser et al.[11] considered the prosthodontic intervention to extend the SDA by a RPD a kind of “overtreatment.” Also, the findings of clinical research cast doubt about the impact of RPD on oral functions when it was used to restore an SDA comprising 3–5 occlusal units (an occlusal unit is a pair of antagonist teeth that supports the occlusion, e.g., premolars and molars).[121314151617] In addition, high failure rate, oral discomfort, and many problems were associated with RPDs that were used to restore the SDAs.[18] It is also believed that it is more appropriate to treat middle-aged and elderly SDA patients according to the SDA concept rather than to extend the SDA by a RPD. Elderly SDA subjects may feel more comfort to chew by their SDAs rather than by an SDA and a RPD.[192021] In addition, cantilever resin-bonded fixed partial dentures achieved better treatment outcomes compared to mandibular RPDs when they were used to restore the SDAs.[2223] Despite the aforementioned arguments, little is known about dentists’ preferences for the RPD as a treatment option for the SDA. Also, it is not yet clear to what extent important factors such as length of the SDA and patient age, would affect dentists’ preferences for the restoration of the SDAs by RPDs.

One of the common methods to assess dentists’ treatment preferences is to measure the value they place on the outcome of treatment using the utility measurements. The utility concept indicates to “levels of subjective satisfaction, distress or desirability that people associate with a particular outcome.”[24] The same authors stated that “utilities are defined as numbers that represent the strength of a person's preference for a particular outcome when faced with uncertainty.” Therefore, according to this definition the best possible health outcome can take the value ‘1’ while the worst possible health state will take the value ‘0.’ The values of any intermediate outcomes will come between these two ends of the utility scale. A review of the medical and dental literature shows that several utility methods have been developed and used to evaluate treatment preferences. These include the rating scale, the standard gamble, the time trade-off and the willingness to pay.[2526] The relative merits and limitations of these methods have been reviewed by Froberg and Kane,[27] whereas Matthews et al.[28] discussed their application in clinical decision making in dentistry and policy analysis.

The aim of this study was to use a utility method in order to assess dentists’ preferences for the restoration of SDAs with partial dentures. Also, the impact of patient age and length of the SDA on dentists’ preferences for the partial denture was investigated.

The examined hypostheses were: There are no differences in dentists’ preferences for the RPD that restored SDAs of varying length, and there are no differences in dentists’ preferences for the RPD that restored SDAs for patients of different ages.

MATERIALS AND METHODS

This study was approved by the Research Ethics Committee at Al-Farabi Colleges, Riyadh, Saudi Arabia. A list of teaching staff members working at Al-Farabi Colleges was obtained from the Directory of Teaching Staff, 2013–2014. Only those holding a Bachelor Degree in Dentistry or equivalent were eligible to participate (No = 138).

A special data collection form was developed and validated through a pilot study. The pilot study comprised 10 dentists and its aim was to evaluate the clarity of the described scenarios and the feasibility of the planned data collection form.

The study form presented four main scenarios for patients with complete maxillary dental arches and mandibular SDAs of different length. Under each main scenario, three sub-scenarios for SDA patients of different ages (30, 50, 70 years old) were presented. The total number of the presented scenarios was 12 [Table 1].

Table 1

The shortened dental arch scenarios that were used in this study

Patients were described as fit and healthy. They had no problems with any of the remaining teeth or their supporting structures. The interarch space was described as adequate and the mandibular residual ridge as able to provide adequate denture support.

In order to measure the utility placed on each SDA scenario, dentists were asked to indicate on a standardized visual analogue scale (VAS) how they would value the health of the mouth if the posterior mandibular space was restored with a properly designed clasp-retained cobalt-chromium RPD. The VAS was a 10-cm horizontal line with two clear end-points [Figure 1]. The left end-point represented the worst health state or number zero. This point was labeled by the statement “the mouth could not be worse.” On the other end of the line, the right-hand anchor or end-point represented the perfect health state. It was labeled by the statement ‘The mouth could not be better’. Dentists were instructed to make a vertical mark on the line and at the point between the extremes which they felt represented the position of the scenario being described. The distance of the mark from the left-hand side of the VAS, in centimeters, divided by ten, comprised the utility score. The division by ten was in order that full health is represented by unity (value = 1) which is the accepted convention in utility measurement.[29]

Figure 1

The visual analogue scale

The collected data were analyzed using the SPSS statistical package (IBM SPSS Statistics for Windows, Version 20.0, Released 2011, IBM Corp, Armonk, New York, USA).

The utility scores for each SDA scenario were obtained by calculating a simple mean for the participant group of dentists as a whole. Paired samples t-tests were used to examine whether there were differences in dentists’ mean utility values among the different SDA scenarios. Bonferroni's correction was applied to account for multiple comparisons and to set the significance level for each statistical comparison.

RESULTS

With the exception of the authors, all teaching staff with a Bachelor Degree in Dentistry or equivalent were invited to take part (No = 133). Totally, 104 teaching staffs approved to complete the study form, and 29 teaching staff declined participation. The final response rate was therefore 78%.

The mean age of participants was 32 years with a range between 25 and 46 years of age. The number of male dentists was equal to female dentists (52/52). Almost half of participants were holding a Master Degree in one of the dental specialties (48%). Approximately 40% were holding only a Bachelor Degree in Dentistry, 6% were holding a Postgraduate Diploma beside the basic dental degree and a minority had a PhD qualification in dentistry (4%). Year of graduation from the basic dental program ranged between 1989 and 2012. Mean years of work experience following graduation was 8 years.

The average utility value of the RPD among the described SDA scenarios was 0.49 ± 0.15 (standard deviation [SD]). Across the 12 SDA scenarios, the mean utility scores of the RPD ranged between 0.35 and 0.61. The mean utility values attached by dentists to the RPD in each SDA scenario are illustrated in Table 2.

Table 2

Dentists’ mean utility values of the partial denture for the mandibular SDAs

It can be noted from Table 2 that dentists’ utility of the partial denture increased with the decrease in the length of the SDA. In order to examine the null hypothesis of no significant differences in the mean utility values assigned by dentists to RPDs that restored SDAs of varying length, the t-test for paired observation was used. The statistical analysis indicated that the length of the SDA had a significant impact on dentists’ utility of the RPD in 13 out of the 18 statistical comparisons [Table 3].

Table 3

P values of t-test for paired observations to examine the differences in mean utility values assigned by dentists to partial dentures restored mandibular SDAs of varying length

The t-test for paired observation was also used to test the null hypothesis of no significant differences in the mean utility values assigned by dentists to RPDs that restored SDAs for patients of different ages. Table 4 shows that patient age had almost no impact on dentists’ utility of the RPD for the SDAs.

Table 4

P values of t-test for paired observations to examine the differences in mean utility values assigned by dentists to partial dentures restored mandibular SDAs for patients of different ages

DISCUSSION

Understanding treatment preferences of health care providers can be considered a cornerstone to achieve the aim of tailoring appropriate treatment decisions. In addition, efficient allocation of health care budgets requires clear insight on the attitudes of those who deliver the treatment.

The sample used in this study was based on subjects holding a degree in dentistry and working as staff members at a private dental college in Saudi Arabia. Staff members of this college are academic people graduated from different dental schools across the Arabic world and Middle East. However, the current study was not designed to evaluate the impact of the country of graduation, academic background or level of clinical experience on treatment preferences. The surveyed sample is relatively small, and the findings of this research may only reflect attitudes of this group of dentists.

This investigation implemented a utility method to elicit dentists’ preferences for the RPD in patients with SDAs. The utility concept is “a well-defined concept based on a solid body of theory and a set of compelling axioms.”[30] Although the utility measurements have been widely discussed and used in medical research, the popularity of the utility methods is still limited in dentistry. So far, only few authors adopted the utility methods in dental research.[3132333435363738]

Of the different utility methods reported in the literature, the VAS was chosen in this investigation. This type of rating scale has been shown to have good intrarater and interrater reliability (r = 0.70–0.94, r = 0.75–0.77 respectively). Test–retest reliability is also greater for rating scales than for other methods of utility measurement, such as standard gambles or time trade-offs.[2739] For this reason and because the rating scale is simpler and easier to understand by most people compared to other utility scales,[40] the rating scale was chosen as a utility measurement method in this study.

The results of this study show that participant dentists place a relatively little value on the option of extending the mandibular SDAs by cobalt-chromium RPDs (average utility value = 0.49, SD = 0.15). This result is almost identical with that reported by Ikebe et al.[41] among dentists in the Department of Prosthodontics and Oral Rehabilitation at Osaka University Dental Clinic (mean utility value of the metal RPD that restored a mandibular SDA with missing molar teeth was 48.6). In addition, attitudes of dentists in our study are in line with attitudes of partially edentulous British patients who attached a low utility value for the cobalt-chromium RPD as a treatment option for the SDA (0.42, SD = 0.3).[34]

In this study, the length of the SDA had a significant impact on dentists’ preferences for the RPD. The utility value of the RPD increased with increase in the number of missing posterior teeth that is, the shorter the SDA, the higher was dentists’ preference for the RPD.

The scenarios for the extremely SDAs that is, SDAs with missing molar and premolar teeth, attracted the highest utility values for the RPD. Clinical research shows that RPDs that were used to restore the extremely SDAs had a positive impact on masticatory function.[121342] Attitudes of the surveyed dentists may reflect their appreciation of such clinical benefit for the RPD when it is used to restore the extremely SDAs.

Age of patient may have a significant impact on the prognosis of treatment with removable dentures. Younger patients were reported to be more reluctant than older patients to wear removable dentures.[3441] On the other hand, older patients may have poorer oral conditions and might lack the neuromuscular control to manage removable dentures.[4344] Our study shows that age of the patient had no effect on dentists’ preferences for the RPD that restore the SDAs.

By taking into account the impact of cross-cultural variations and professional characteristics on making treatment decisions,[4546] further work among other cohorts of dentists from different cultural and professional backgrounds is recommended to confirm the findings of this investigation.

CONCLUSION

The results of this investigation show that restoration of the mandibular SDAs by RPDs is not a highly preferred treatment option among the surveyed group of dentists. Length of the SDA affected dentists’ preferences for the RPD, but patient age had no evident impact on dentists’ treatment preferences.