We designed a Budget Impact Analysis in accordance with the Methodological Guidelines of the Methodological Guidelines for Budget Impact Analysis of the Brazilian Network for Health Technology Assessment (REBRATS)  and with the presupposition of gradual diffusion of oral rehabilitation by means of CISP on two implants.
The presupposition of gradual diffusion was determined, because although there is an expectation that more effective technologies will be rapidly incorporated into clinical practice, this limitation must be recognized, particularly within the context of SUS. Diverse variables could interfere in the process of diffusion of a technology, such as for example, training and qualification of human resources, in addition to the culture itself of the patients .
The CISP on two implants has been pointed out as being the minimum treatment indicated for the rehabilitation of patients with edentulous mandibles [8–10]. Nevertheless, the CCP is the treatment most frequently offered as the proposal for rehabilitation in SUS, and continues to be routinely used in dental clinical practice because of its low cost .
We adopted the perspective of the Federal Management of the Brazilian National Health System - SUS (Ministry of Health of Brazil).
Discount Rate and Time Horizon
We applied no discount rate and adopted the horizon of 5 years, starting in 2020 through to 2024, as recommended in the Guidelines of REBRATS .
Federal government financing incentive was assumed for the incorporation of substitutive rehabilitation by means of implant-supported dental prostheses, from the perspective of the Federal manager. The method for collecting cost data was based on the top-down, or macro costing approach, and was obtained from the table of SIGTAP - system for management of the table of procedures, medications and OPM of SUS “Sistema de Gerenciamento da Tabela de Procedimentos, Medicamentos e OPM do SUS” . These are presented in Table 1 in US dollars (Year 2019).
Population of Interest
To predict and eligible population and the need for total investments to increase the diffusion of rehabilitative treatment of edentulous mandibles in SUS we combined epidemiological information, estimates of participation of the population and treatment costs.
The eligible population for treatment with CISP in our study was the same as that for CCP and concerned edentulous mandibles. In Brazil, this condition affects approximately 23 million persons of all age groups, but particularly the elderly .
In view of this high prevalence, initially and in the temporal horizon of 5 years, it must be admitted that large scale implementation of CISP is not feasible for 100% of those affected by the condition, for budget reasons.
Starting with this reality, we considered that for analysis from the perspective of the Ministry of Health, calculation of the population of interest by the method of demand found was more appropriate for helping with decision making .
In 2017, a total of 162,105 Complete Mandibular dental prostheses were approved in Brazil . This means that this demand exists in the country. From these data, we were able to predict an approximate demand of 900,000 edentulous mandibular patients to be attended over the course of 05 years [temporal horizon of the analysis] in the SUS.
Initially, therefore, this would be the eligible population. However, some presuppositions were considered. One of these was that there were contraindications relative to the surgical procedure for implant placement. These limitations included smoker patients, those with some cardiovascular disorders, the use of certain medications and some systemic pathologies. Secondly, we needed to consider that some patients might simply not wish to go through the surgical procedure required. Added to this, there is still the fact that in Brazil, the offer of services included in the public health and private system. So that it was a common occurrence for patients who had economic resources to choose to have treatments they considered more complex performed in the private system.
Within this context, we presupposed that only 30% of the total number of patients initially foreseen would fit into the profile of the target population. Considering the initial calculation, we predicted a demand of 270,000 to be attended by means of implant supported prosthesis on two implants, in five years.
According to this reasoning, in the new scenario proposed, the patients who met the criteria for rehabilitation with CISP would receive the new treatment, and the remainder would receive CCP.
Reference Scenario and Analysis per Scenarios
The reference scenario of the Budget Impact Analysis considered that all of the 900,000 patients would be rehabilitated with CCPs, while in the scenario proposed, the 270,000 patients eligible for rehabilitation with CISP would receive this treatment and the remainder would be rehabilitated with CCP, as illustrated in Fig. 1. Furthermore, in the period of the temporal horizon, it was considered that there would be no increase in the Federal financial transfer value.
Analysis per scenarios were made, due to the possibility of the following parameters and presuppositions generating uncertainty in the results:
I) Variation in the number of patients to be rehabilitated.
II) Variation in the Federal transfer value.
The Federal transfer value and the number of the elected population were simultaneously varied [raised and lowered] by 25%. In the most optimistic scenario, the population and the transfer values were varied by lowering them, thus calculating a lower impact on the manager. In turn, in the most pessimistic scenario, the population and the transfer values were varied by raising them, thus calculating a higher impact on the manager.
Budget Impact Calculation
Since the difference between the scenarios (actual and proposed) was in the portion of patients treated with CISP and in the value of this treatment, the incremental budget impact was considered the difference between the cost of rehabilitating these patients with CISP and the cost of rehabilitating them with CCP. No adjustment for inflation was considered and the values are presented in US dollars (Year 2019) . The formula applied for calculation is presented below:
INI = N x (CCISP - CCCP)
IBI = Incremental Budget Impact
N = Total number of patients with indication for mandibular implant-supported and conventional complete mandibular dental prosthesis.
CCISP = Total Cost of Implant-supported Dental Prosthesis.
CCCP = Total Cost of Conventional Complete Dental Prosthesis.