Introduction

Dental laboratories, while essential for comprehensive treatment plans, have a considerable environmental impact. Many materials used in dental laboratories are single-use, such as impression trays and personal protective equipment, which contribute to plastic waste. Dental laboratories also utilize various chemicals, such as polymers, gypsum products, etchants, ceramics, metals, wax, and solvents, which can be harmful to the air, land, and water if not disposed of properly [1]. Dental laboratories rely on energy-intensive equipment like furnaces, ovens, and casting machines, which can result in high carbon emissions from energy consumption [2].

Fossil fuel combustion releases carbon dioxide in the atmosphere. Carbon dioxide is a potent greenhouse gas (GHG), which absorbs and traps heat within the atmosphere [3]. Global warming is the progressive gradual rise of the planet’s surface temperature that is caused by the GHG effect and results in changes in global climate patterns [4]. Climate change refers to a change in the state of the climate which can be identified by changes in the mean and/or the variability of its properties and persists for an extended period, such as decades or longer. Climate change could be due to natural internal processes or external forces [5]. Climate change has a disastrous impact on the planet, including increased heatwaves, droughts, floods, rising sea levels, and extreme weather events. The continuous monitoring of GHG emissions and low-carbon sustainable solutions are required to limit global warming to well below 2 °C [6].

Monitoring of GHG emissions is done through carbon footprinting, which quantifies the direct and indirect GHG emissions released from a service, product, or process. It combines all GHGs into one unit named carbon dioxide equivalent (CO2e) [7]. The main methodologies for carbon footprinting are Process-based Life Cycle Analysis (PB-LCA), Environmental Input-Output Life Cycle Analysis (EIO-LCA), and a hybrid method. PB-LCA estimates GHG emissions by tracking the pathways of supply chains and multiplying them by conversion factors derived from scientific studies. EIO-LCA, the spend-based approach, estimates GHG emissions by calculating the amount of money spent on a service and multiplying it by a sector-specific conversion factor [7].

The global healthcare sector produced 1.6 to 2 gigatons of CO2e in 2019, representing 4.4% of the world GHG emissions [8]. The GHG emissions of the global dental sector constitute around 3% of the global healthcare sector’s GHG emissions [9]. The GHG emissions of dental laboratories can be explained through The Greenhouse Gas Corporate Accounting and Reporting Standard Protocol [10]. It defines three broad scopes of GHG emissions (Table 1).

Table 1 Scopes of GHG emissions according to the Greenhouse Gas Protocol [10].
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A systematic review showed that the CFP of laboratories is usually pooled with the CFP of other healthcare services [11]. The same approach was used to estimate the CFP of dental services in the National Health Service (NHS) England [2, 12,13,14]. A study showed that the laboratory fees constituted one third of the procurement fees of all NHS England dental clinics, accounting for 7679.3 kg CO2e [12]. However, this approach only accounted for the laboratory fees and may not fully reflect the CFP of dental laboratories [7, 12]. None of the previous studies solely assessed the CFP of dental laboratories.

Climate change disproportionately impacts the developing world, which has a limited capacity to adopt effective mitigation and adaptation strategies to reduce their projected vulnerability to climate change [15]. While Africa has negligibly contributed to climate change [16], it is one of the most vulnerable regions in the world. This is due to the low socioeconomic growth and high economic dependency on climate-related resources, such as fishing and agriculture [15]. To date, little is known about the CFP of oral healthcare in African and developing countries.

Egypt is a lower-middle income country located in North Africa [17]. Although Egypt shares by only 0.69% to the world’s CO2e emission [16], it is highly vulnerable to climate change. The Egyptian population growth (over 106 million people) is considered the major driver of escalating GHG emissions [17]. Climate projections indicate that Egypt will continue to experience a higher level of warming than the global average [18]. This necessitates the close monitoring of the CFP of healthcare facilities, especially the private healthcare sector, as it is the fastest-growing healthcare provider in Egypt [19]. This study aimed to assess the CFP of private dental laboratories in Egypt. This would help identify carbon-intensive areas, develop effective carbon mitigation strategies, enable targeted interventions for greener oral healthcare systems, and facilitate informed decision-making.

The Egyptian dental laboratory model, characterized by a mix of small laboratories and larger facilities, reliance on fossil fuel energy sources, and improper segregation of waste, may be representative of practices in other Low- and Middle-Income Countries LMICs. The study findings can be extrapolated to other LMICs, as they share similar socioeconomic contexts, including developing economies, limited resources, and nascent regulatory frameworks [20]. These shared characteristics often translate to similar challenges in energy production, transportation system, and waste management in the dental sector.

Materials and methods

A cross-sectional study was conducted in Cairo, Alexandria and Elbeheira, Egypt in August 2024. Cairo, the capital and largest city of Egypt, has a population size of over 10 million people and an area of 3085 km². Alexandria, the second largest city of Egypt and its main port, has a population size of over 5 million people and a size of 2300 km². Elbeheira, a northwestern governorate in the Nile Delta, has a population size of around 7 million people and an area of 9826 km² [17]. There are no data on the number of private dental laboratories in Egypt. Ethical approval was obtained from the Research Ethics Committee, Faculty of Dentistry, Alexandria University, Egypt (#0941-07/2024). Informed consent was obtained from the laboratories’ managers, technicians, and personnel. Data were collected from private dental laboratories from different areas in the three governorates. A laboratory was considered eligible if it was a private standalone laboratory with at least one full-time technician. Public laboratories at hospitals were excluded. Laboratories within integrated healthcare facilities were ineligible due to the difficulty of assessing independent water and energy consumption.

Interview questionnaires were done, in person or over the phone, to collect year-round data from each laboratory about the workflow from July 2023 to July 2024. The validated Duane et al. CFP calculator for dental clinics [2] was used. The calculator consists of 8 items: (1) the number of days that the clinic is open per year, (2) the number of staff, (3) the number of patient visits per year, (4) staff travel distance and method of transportation, (5) number of waste bags (infectious, domestic, plastic waste for recycling, and cardboard waste for recycling), (6) Energy consumption (standard and green electricity, electricity from solar panels on clinic’s roof, and gas), (7) water consumption, (8) procurement (Expenditure on dental materials and equipment excluding rent and interest). The calculator was based on some assumptions (Table 2). The third question was replaced by the number of prostheses/appliances fabricated per year to calculate the CFP per prosthesis/appliance. The validity of the questionnaire was assessed by a panel of experts.

Table 2 The assumptions of the items used in the carbon footprint calculator [2]
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The annual depreciation of the equipment was calculated assuming that they will be replaced within 5 years [21]. The sources of data are shown in Table 3. Respondents, Laboratory managers and personnel were asked to provide year-round electricity, gas, and water bills and dental materials’ and equipment’s invoices. The data of all laboratories were averaged to obtain the average CFP per laboratory, per prosthesis/appliance, both with and without the depreciation cost. The carbon footprinting approach was PB-LCA, except for procurement which was EIO-LCA.

Table 3 The source of information for items used in the carbon footprint calculator.
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Results

Twenty-one dental laboratories (2 in Cairo, 16 in Alexandria, and 3 in Elbeheira) consented to participate in the study out of 24 invited (87.5%). The average number of workdays in the laboratories was 309 days. The average full-time staff number was around 7 persons. The average number of fabricated prostheses/appliances per year was 7,119.

The average total distance traveled by staff was 972.1 miles per week, accounting for 9083.6 kg CO2e per year. Motorbikes were the highest source of carbon emissions (5545.4), followed by buses (1754.1), and petrol/diesel cars (1680.6) kg CO2e. An average of 1.2 infectious waste bags and 3.9 domestic waste bags were collected per week. There were no waste bags for recycling. The total waste CFP was 697.1 kg CO2e per year.

The average yearly electricity and gas consumption was around 17,789 and 1540 kWh, which accounted for 4889.5 and 323.4 kg CO2e, respectively. No green electricity or solar power were consumed. The average yearly water usage was around 89 m3, accounting for 30.1 kg CO2e per year. The average procurement was around 44,088 GBP, accounting for 5786.1 kg CO2e per year.

The average total CFP of a private dental laboratory in a year was around 20,820 kg CO2e, equal to 2.9 kg CO2e per prosthesis/appliance. This rose to around 22,426 Kg CO2e, 3.1 kg CO2e per prosthesis/appliance, after adding the cost of depreciation. Depreciation increased the CFP by 7.7% (Table 4). Staff travel represented 43.6% of the private dental laboratories CFP, followed by procurement (27.8%), energy consumption (25%), waste (3.3%) and water consumption (0.1%) (Fig. 1).

Fig. 1
figure 1

Distribution of the CFP of private dental laboratories in Egypt.

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Table 4 The average annual carbon footprint of private prosthodontic dental laboratories in Egypt (N = 21).
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Discussion

The study findings showed that in private dental laboratories in Egypt, staff travel was the greatest contributing factor to the CFP, followed by procurement and energy consumption, whereas waste and water had less impact.

Private dental laboratories in Egypt are not bound to a fixed work schedule, which contributes to the notable number of workdays. Additionally, the number of full-time staff in private laboratories could be attributed to the low salaries in Egypt [22], which allowed the laboratories to hire a significant number of staff. High workdays and staff number contributed to a high CFP of staff travel. The CFP calculator was designed according to travel in England, however, public transportation in Egypt may be older and less efficient [23], so we might be underestimating the CFP for staff travel in Egypt. It is important to invest in improving roads and public transportation for optimal fuel efficiency and to encourage energy-efficient mass transportation, such as electric buses and trams. Notably, the majority of staff travel CFP was attributed to motorbike travel, because the laboratories hired multiple couriers to deliver the prostheses/appliances and dental impressions to and from the clinics. Thus, dental laboratories could benefit from bulk delivery services which deliver multiple packages to different addresses while saving time and fuel.

The remarkable CFP of procurement could be attributed to the high number and diversity of dental materials needed for the fabrication of prostheses/appliances. However, the carbon calculator used the spend-based approach to estimate the CFP of procurement. The conversion factor was based on the carbon emissions of the NHS expenses, adjusted for the inflation in England [14]. This generic conversion factor may not accurately reflect the procurement CFP in other countries, as in Egypt, because both countries have different oral healthcare expenditure, inflation rates and supply chains. The NHS allocates considerably more annual funding to oral health care than Egypt (3 billion and 0.257 ≈ 0.3 billion GBP, respectively) [24, 25]. The inflation rate, in the present time, is 2.2% in England and 25.7% in Egypt [26]. Egypt imports a considerable amount of its dental products from European countries, which denotes longer transportation distances and supply chains [27], thus higher CFP. These differences in the CFP components for procurement between both countries emphasize the need to develop customized country-specific calculators to precisely assess the CFP of dental laboratories in different settings. Additionally, there is a need to locally manufacture dental machinery and equipment, thereby shorten the supply chain and eliminate the carbon emissions associated with cross-country transport.

Calculating the CFP of dental laboratories taking into consideration the depreciation of existing equipment resulted in a distinct increase in the CFP of procurement. This highlights the importance of investing in equipment with prolonged durable life, because such equipment decreases the need for frequent replacements, saving costs associated with purchasing, transporting, and installing new equipment. This ultimately contributes to improved environmental efficiency and more sustainable value chains [28].

There was a notable CFP of electricity consumption. This could be explained by several factors. First, the high temperature and humidity necessitated running the air conditioning at low temperatures [29]. Second, dental laboratories employ electricity-intensive machines, such as the CAD/CAM machines and furnaces [30]. Third, the air conditioning was often used year-round to cool the machines down. Fourth, the shortage of technicians led to extended work hours to meet the high demand of the dental clinics [31], resulting in prolonged electricity consumption. Conversely, gas consumption was minimal, as it was primarily used for waxing and was not needed during winter for heating [29]. Neither green electricity nor solar panels were used. Egypt utilizes electricity produced from a fuel mix, mainly fossil fuel (88%) [32]. This results in a higher CFP of electricity consumption. Transitioning to renewable energy is advised to mitigate carbon emissions. Dental laboratories’ buildings should be designed with thermal efficiency in mind to minimize the use of air conditioning and its associated GHG emissions [33].

The noticeable CFP of waste could be attributed to the lack of training that the technicians receive on waste segregation [34], lack of recycling, and deficient incineration facilities [35]. Reusing dental instruments, such as impression trays and finishing and polishing burs, after thorough cleaning, disinfection, and sterilization could help reduce waste CFP [36]. Recycling dental materials used in the laboratories, such as gypsum, acrylic resin, and orthodontic wires, could decrease the demand for raw materials and minimize waste. Rethinking the entire supply chain is needed to shift from the linear to circular economy models [37]. Linear economy is characterized by the consumption and disposal of products, leading to resources depletion, increased procurement rates, and end-of-life waste. Instead, circular economy involves reducing, reusing, and recycling resources throughout production, distribution, and consumption processes, thus, decreasing the CFP of waste, procurement and energy consumption along the entire supply chain [38].

The CFP of water consumption was not significant because water was only needed for mixing of gypsum and domestic purposes. In addition, some laboratories relied on digital fabrication of prostheses which involved less water consumption. The estimated CFP per prosthesis/appliance highlights the substantial environmental impact of oral diseases complications and tooth loss, in addition to their well-documented effects on health, community, and economy [39]. This underscores the necessity of considering the environmental impact as a part of the overall burden of oral diseases. There should be a collaborative effort among dental clinicians, laboratories, and regulatory bodies to rationalize the use of indirect restorations while considering both carbon emissions and patient comfort and satisfaction.

This study has several strengths. First, the study sheds light on the CFP of dental laboratories solely, unlike other studies which pooled the CFP of laboratories with dental clinics and hospitals [2, 12,13,14]. Second, the carbon footprinting of staff travel considered country-specific transportation methods, such as the Tuk-Tuk, which had lower carbon emissions than other vehicles. Third, considering the courier services used by the laboratories revealed a distinct factor which largely increased the CFP of Egyptian dental laboratories, highlighting its associated challenges. Fourth, the calculation of the depreciation of dental equipment identified a previously overlooked source of GHG emissions that accumulates over the equipment’s useful life.

Regardless, this study has some limitations. First, the CFP calculator was designed according to the dental practice in England, which may not accurately reflect carbon emissions in Egyptian dental laboratories and suggests the need to develop customized country-specific CFP calculators. Second, the data may not have been measured with absolute precision due to the complexities and uncertainties of the estimation of dental products’ supply chains, waste weighing, couriers travel, and gas consumption [14]. Third, the laboratories did not maintain records of the number of prostheses/appliances produced, so the measured CFP per prosthesis/appliance may not be accurate. Fourth, as the CFP estimation is typically limited to a specific timeframe (one year) [10], it did not account for carbon emissions resulting from the construction of dental laboratories, as none were recently built.

The study findings can be extrapolated beyond Egypt, particularly for other LMICs facing similar challenges in the dental sector. For example, the staff travel CFP underscores the need for exploring more sustainable energy solutions in countries with heavy reliance on fossil fuels [40]. Similarly, the waste CFP highlights a common issue in LMICs countries where recycling infrastructure may be limited [41]. However, the diversity of cultural practices across LMICs necessitates a cautious approach to extrapolating the study findings [20]. Future research should investigate the specific contexts of other LMICs to allow for comparison and develop tailored solutions.

It is recommended that dental laboratories foster environmental sustainability by implementing digital dentistry technology, e.g. CAD-CAM and 3D printing of dental restorations. Digital dentistry promotes higher precision and accuracy over conventional dentistry. This contributes to shorter laboratory work hours, less energy and water use, less frequent need for remaking restorations, thus less staff travel. Digital dentistry eliminates the need for dental impressions, gypsum products, and waxes which considerably lowers waste and procurement [42]. Further research is needed to compare the environmental impact of conventional and digital dentistry in dental laboratories.

As demand for oral healthcare increases, the corresponding carbon emissions will likely intensify, if oral diseases are not sustainably managed. Preventing oral diseases remains the most effective strategy for reducing carbon emissions of dental laboratories, as it reduces oral diseases, disease complications, and the need for indirect restorations [43]. The regulating bodies should increase the monitoring and supervision of dental laboratories. Continuous education courses should be conducted to educate dental technicians on carbon reduction interventions and to facilitate the adoption of sustainable practices.

Conclusion

Private dental laboratories in Egypt produce a substantial amount of carbon emissions. Staff travel was the primary contributor to these emissions mostly because laboratories hired multiple couriers to deliver the prostheses/appliances and impressions to and from the clinics. The CFP of electricity consumption was significant as the dental laboratories tended to keep the air conditioning on to cool down energy-intensive machines year-round. However, the CFP of gas consumption was minimal as heating was rarely needed. The CFP of procurement was substantial, highlighting the need to adopt a circular economy and local manufacturing of dental equipment. The notable CFP of waste was probably due to the lack of recycling and segregation. Future studies are needed to develop country-specific CFP calculators to accurately measure the carbon emissions of dental laboratories in various settings. Preventing oral diseases, regular monitoring of dental laboratories, educating technicians on sustainable dental practices, optimizing public transportation, shifting to renewable energy sources, and implementation of recycling are recommended to reduce carbon emissions of dental laboratories.

Note added to proof

Note that elements of this study, particularly the methods, have been published as part of a related study in a different setting which was published during the production of this paper [55].