Measuring the Cost of Implant Overdenture Therapy
Dental implant treatment is a safe, efficacious, and effective therapy for edentulous arches.1,2 However, the relatively high initial costs for current implant treatments often lead patients, especiallythe elderly, to choose the less expensive option-treatment with conventional dentures. This choice is driven in large part by patients’ limited ability to pay; edentulous patients tend to come from households with below-average incomes.3 Therefore, before implant therapy can become the standard of treatment for edentulous patients, cost-effective, simpler implant treatments that are affordable for patients must be developed. Economic data for such treatments would provide important information to all relevant parties: patients, health care providers, and third-party payers.
This chapter compares the cost of mandibular overdentures supported by two implants to conventional denture treatment through I year after delivery of the prosthesis. Because of their simplicity, mandibular overdentures supported by two implants with ball attachments may be less expensive than other implant treatments for which economic data are available.4,5 This analysis was conducted alongside a randomized controlled trial involving 60 elderly edentulous patients in Montreal, Canada. A resource-based microcosting of the direct and indirect costs (in 1999 Canadian dollars) of all scheduled and unscheduled visits was conducted through I year after delivery of the prosthesis.
While implant overdentures are less expensive than implant-supported fixed prostheses, they do cost more than conventional dentures. The cost identification through year I is the first step in a long-term evaluation of the cost effectiveness of treatment modalities and, hence, a step toward the answer to the question, Are implant overdentures worth the cost?
The economic analysis was designed prospectively as part of a randomized controlled trial comparing the efficacy of overdentures supported by two implants to conventional dentures in patients aged 65 to 75 years. The primary outcome of the study was to assess the difference in patient satisfaction, and the primary endpoint was 2 months after delivery of the prosthesis. Patients who met all inclusion and exclusion criteria were asked to participate in the study.6 Thirty patients in the implant overdenture group and 30 in the conventional denture group participated in the study. The overdenture patients received two root-form implants (ITI dental implant system, solid screw sandblasted, large-grit, acid-etched implants, Straumann, Waldenburg, Switzerland) placed in front of the mental foramina. Details of the clinical procedures have been described elsewhere. 6,7 To compare the two groups, Student t or Mann-Whitney U tests were performed with SPSS 10.0 (SPSS, Chicago, IL).
For the economic portion of the study, visits were subdivided into scheduled and unscheduled visits. Unscheduled visits were defined as visits initiated by patients.6,7 The treatment was divided into one surgical phase and four prosthodontic phases, PI to P4.The surgical phase was from preliminary examination to postoperative reline. PI was from the day preliminary impressions were taken to the day of delivery; P2 was from the day of delivery to 2 months postdelivery; P3 was from 2 to 6 months postdelivery; and P4 was 6 months to I year postdelivery.
Costs were subdivided into direct and indirect costs and were estimated based on microcosting of the resources used (clinician time, etc), rather than clinician charges. The direct costs included costs of labor, materials, pharmaceuticals, laboratory work, and radiography.The indirect costs included patients’ time and out-of-pocket expenses.
To determine the opportunity cost of labor, the time spent by the clinicians and the surgical assistant was measured.This time included setup, treatment, clean up, and administrative tasks associated with patient contact. A detailed account of the time spent at each treatment stage has been reported previously.6,7 The opportunity cost of time was estimated from data on Quebec incomes from the 1996 Canadian census.8 Adjusted to 1999 dollars, the average hourly wages of dentists and dental assistants were Can $51.97 and Can $15.87, respectively. Since there are no data available on the incomes of Canadian oral surgeons, data on clinician incomes from the United States were used to calculate the ratio of specialist-to-generalist incomes. This ratio was applied to the 1996 Canadian census data to obtain an estimated value of an oral surgeon’s time of Can $73/h.9 Since the American Dental Association (ADA) data indicated that the wages of American prosthodontists and general practitioners are quite similar, the prosthodontist’s wage was estimated at Can $52/h.10 Costs of nonmonetary “fringe” benefits of clinicians and staff were included in the overhead costs described below.
All disposable and reusable materials used for both groups were recorded. A product catalog (Henry Schein Arcona, Canada) from 1999 was used for acquiring market prices of all materials. To estimate the cost per use of reusable items, 28 Montreal-area dentists were asked to fill out a questionnaire regarding the useful life and the frequency of use per week of the relevant items. Using the useful life, the purchase price, and a discount rate of 5%, the annualized costs were computed using the standard textbook calculation.11 The cost per use then was estimated by dividing the equivalent annual cost by the frequency of usage in one year, provided by the clinician survey.
Laboratory costs were based on the fee of a commercial dental laboratory in Montreal and pharmaceutical prices were obtained from a Montreal retail pharmacy. Radiographs were covered by the Régie de l‘assurance maladie du Québec, the universal provincial health care insurance plan.The cost for one panoramic radiograph, Can $27.23, was used for the cost calculation and was provided by the administrators of the Royal Victoria Hospital. The radiographs are read by the oral surgeon and the cost of radiograph evaluation is included in his time cost. Indirect costs included patients’time of seeking treatment and their transportation. Following the recommendations of published guidelines, the human capital method was used to value this time.12,13 The average of hourly earnings reported in the 1996 Canadian census for Quebec workers aged 55 and older, Can $17.16 (adjusted for inflation to 1999 Canadian dollars), was used. Transportation costs included hospital parking, taxis, public transportation, and patients’ own motor vehicle operation. Estimates of transportation costs were based on a patient self-administered questionnaire.
The cost analysis for this study reflects the costs of resources directly associated with treatment or, in the case of indirect costs, with seeking treatment. However; a significant portion of ove rall cost is related to the overhead of operation of the dental practice. As time required by prosthodontists is similar for both treatment modalities studied here, incorporation of overhead costs does not significantly impact the estimated cost difference. Nevertheless, adoption or nonadoption of an implant strategy is likely to influence the long-term number of oral surgery practices. For this reason, it is important to incorporate overhead practice expenses.
Although no published data on practice expenses in Canada are available, the ADA published estimates of overhead and other expenses as a percentage of the gross billing of solo unincorporated specialists practicing in the United States.14 Adjusting the ADA data to accommodate the particular features of the practices studied in this chapter, the practice overhead was calculated to be 40% and 38% of total billings for oral surgeons and prosthodontists, respectively. Since the ADA data />