Cost Calculation

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.