Environmental impact of orthodontic treatment: a simplified fast-track comparative life-cycle impact assessment of self-ligating metal brackets and clear aligners

The aim of this work was to determine advanced the oxidative protein products (AOPPs), total antioxidant capacity (TAC), and myeloperoxidase activity (MPO) in the saliva of patients undergoing orthodontic treatment with clear removable aligners in comparison with another group in treatment with fixed passive self-ligating brackets applying light forces, before treatment, after 30 days, and after 90 days of treatment. This non-randomized clinical trial recruited patients consecutively, all of which were over 18 years of age and due to undergo orthodontic treatment. They were divided into two groups according to treatment type: Group A, 48 patients treated with clear aligners (Invisalign®); and Group B, 19 patients treated with Damon System® 0.22″ self-ligating brackets applying light forces. Saliva samples were collected by a single clinician following the same protocol and underwent three analyses—AOPPs, TAC, and MPO levels–at baseline before placing the apparatus, after 30 days, and after 90 days treatment. Orthodontic treatment, whether with clear aligners or fixed self-ligating brackets and light forces, increased AOPPs after the first 30 days of treatment. During the initial phases of orthodontic treatment, neither clear aligners nor fixed self-ligating brackets applying light forces showed changes in TAC and MPO. Orthodontic treatment with both clear aligners and fixed apparatus self-ligating brackets applying light forces increases oxidative stress (AOPPs) after the first 30 days of treatment. There are no differences in AOPP levels between treatment with clear aligners and self-ligating brackets during the first 90 days of treatment. The antioxidative capacity of saliva during the initial phases of orthodontic treatment, whether with self-ligating brackets or clear aligners, does not undergo significant changes. With either orthodontic technique, the patients’ salivary antioxidant capacity is similar.

Which orthodontic appliance is best for oral hygiene? A randomized clinical trial.

Aim: To evaluate orthodontists’ perspectives on clear aligner treatment in Turkey.Methods: A novel web-based survey consisting of 14 questions was developed and sent to 2027 members of the Turkish Orthodontic Society via e-mail to evaluate the reasons for why or why not they prefer clear aligners, their opinions about different brands in the market and their perspective on the future of this treatment modality. The association between demographic data and multiple choice questions was examined using Kruskal Wallis and Mann-Whitney U tests. The association between Likert-type questions and practice characteristics was analyzed using a one-way analysis of variance (ANOVA) and Turkey’s post hoc tests.Results: 62.7% of the 218 respondents currently treat their patients using clear aligners and 76.7% of them prefer Invisalign (Align Technology, California, USA), a clear aligner brand. The main reasons given by orthodontists to use clear aligners were ‘not to lag behind in technology’ and ‘to have prestige in the community’. The majority of participants (83.8%) treat fewer patients with clear aligners than with fixed appliances. 70% of the surveyed orthodontists do not believe that treatment with clear aligners will completely replace treatments with fixed appliances in the near future. 28.6% of the participants stated that they do not intend to use clear aligner treatment in at least the next 1-2 years due to ‘low financial income’ and ‘complexity of clear aligner treatments.Conclusion: The majority of the surveyed orthodontists currently use clear aligners in their practice, not because they believe clear aligners are more effective or more comfortable than braces or because they are more profitable, but rather to have prestige in the community and not to lag behind in technology. Therefore, it seems that fixed appliance treatment will maintain its place in orthodontic practice as an option for the near future.

The use of clear aligners in orthodontic treatment has grown in popularity because of its visual appeal and patient-friendly nature. In contrast to fixed appliance treatments (FAT), the relationship between external apical root resorption (ERR) and clear aligners is still unknown. The objective of this systematic review was to evaluate the frequency and severity of root resorption in clear aligner orthodontic treatment, compare it to fixed multi-bracket appliances, and determine the factors that contribute to this phenomenon. The review was conducted without regard to linguistic constraints, using PRISMA criteria and examining studies from 2000 to 2023. MEDLINE/PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials were among the databases that were searched. MeSH words about root resorption, aligners, and orthodontics were utilized. Cohort studies, case-control studies, randomized clinical trials, and comparative clinical studies assessing root resorption during clear aligner orthodontic therapy. Out of the 116 studies that were first found, 11 studies were included in the final analysis. While several trials revealed equal results or no significant differences, six reported decreased incidence and severity of ERR in clear aligner therapies (CAT) compared to FAT. A meta-analysis revealed that CAT had less severe ERRs than FAT. In both treatments, ERR frequently affected the maxillary lateral incisors. Potential significant factors included the mechanical distinctions between CAT and FAT, length of therapy, tooth movement velocity, degree of malocclusion, and extraction instances.The review indicates that there may be differences in the frequency and intensity of ERR between CAT and FAT. In multiple investigations, CAT demonstrated reduced ERR severity, although it did not completely eradicate its recurrence. Mechanical characteristics, length of therapy, degree of malocclusion, and number of extraction instances were factors affecting ERR. The included studies' quality assessment indicated a moderate to substantial risk of bias, highlighting the need for more thorough research using reliable measuring techniques, especially when utilizing CBCT imaging.

The purpose of this study is to compare the environmental impact differences of four types of vehicles on a life cycle assessment (LCA) perspective: a conventional gasoline vehicle, a pure electric vehicle, a plug-in hybrid gasoline-electric vehicle, and a plug-in hybrid fuel cell-battery vehicle. The novelty of the approach is to consider the different powertrains—electric and hybrids—as a repowering of the conventional powertrain. This way, the attention can be focused only on the powertrain differences and inefficiencies, with the added value of avoiding further assumptions, which could cause the analysis to be somehow rough. Thus, we compared four powertrain scenarios maintaining the same vehicle chassis, and we compared the impacts from the powertrain production, vehicle use phase, and powertrain end of life only. Hence, special attention was paid to the inventory for powertrain construction and use phase. For the powertrain components, an accurate literature survey has been carried out for the life cycle inventory. For the use phase, several driving cycles, both standardized and real-world type, have been simulated in order to properly evaluate the effect on the fuel/electricity consumption. For the comparison, environmental indicators according to cumulative energy demand (CED) and ReCiPe Midpoint methods have been used. This way, an analysis of the environmental impact, based on a life cycle impact assessment approach, is provided, which allows thoroughly comparing the systems based on the different powertrains. Moreover, a sensitivity analysis on different energy mixes has been included, which represents also a way to take into account changes in electricity production. Results are presented according to life cycle impact assessment, which examines the mass and energy inventory input and output data for a product system to translate these data to better identify their possible environmental relevance and significance. In the case of the climate change (CC), fuel depletion (FD), and CED indicators, the lowest value corresponds to the plug-in hybrid gasoline-electric vehicle, followed by the plug-in hybrid fuel cell-battery vehicle, the pure electric, and finally the conventional gasoline vehicle. Substituting a conventional gasoline powertrain with the corresponding pure electric one offers the lowest reduction, but still of valuable amount. In our analysis, for the considered systems, the reduction of the value of CC is about 15%, the reduction of the value of CED is about 12%, and the reduction of FD value is about 28%. This analysis underlines the weakness of a tank-to-wheel comparison, according to which the pure electric powertrain, having a very high average efficiency, results in being the less consuming, followed by the hybrid gasoline-electric and fuel cell-battery vehicles, respectively, and then by the conventional vehicle. Instead, in terms of CED, the bad influence of the low average efficiency of the Italian electricity production is highlighted. The LCA approach also stresses out the importance of the battery inventory, which can make the environmental performance of the system based on the pure electric vehicle significantly worse than those based on the conventional vehicle. Of a great significance is the presence of a group of indicators—including human toxicity, eutrophication, and acidification—with lower values in the case of conventional gasoline vehicle than in the electric and hybrid ones, which further confirms that the potential of electrified vehicles strictly depends on an efficient production and recycling of the battery. The analysis underlines an alarming list of environmental impact indicators, usually neglected, which are worsened by the powertrains electrification. Operating on the production processes, used materials and recycling phase can possibly mitigate these worsening effects. Also, the type of electricity is shown to strongly affect the results. Thus, performing specific evaluations for different countries is crucial and a sensitivity analysis, involving drastically different energy mixes, can allow for taking into account possible changes in the future electricity production.

Globally, there is an increased interest of the Food Industry, the Politicians and the consumers to be informed about the environmental impacts connected to the production and the supply of food products.In the framework of the Paris Agreement for Climate Change and the 2030 Agenda of the United Nations for Sustainable development, the European Union (EU) has set demanding targets for the years 2030 and 2050 regarding the mitigation of environmental impacts from all its economic activities. Within this legislative context, which is expected to become stricter, the Primary Sector in Greece in general and the Livestock Production Sector more specifically are and will be obliged to contribute to the accomplishment of these goals (at country and EU level).Recent studies have highlighted the increased importance of livestock production systems regarding global environmental pollution and the discussion about implementation of strategies at the farm level for mitigation of environmental impacts has already started. Evaluating such actions on the supply chain level, allows to ensure that these actions do not cause negative environmental effects (problem shifting) to other stages of the supply chain apart from the livestock farm and eventually to the supply chain in total. To this respect, Life Cycle Assessment (LCA) is considered and has been suggested as a suitable methodology for environmental impact assessment.It has to be noticed that differences in the supply chain systems and production practices of livestock products as well as differences in the climatic conditions that these systems occur, lead with high certainty in differences regarding their environmental performance. Τhere is also a lack of environmental LCA (ELCA) research which refers to Greek agricultural and livestock goods or the Food Industry. Implementation of ELCA further requires specialized scientific knowledge and the use of software for which special training is required. Thus, the access of Greek livestock farmers (but also other stakeholders of the livestock products’ supply chains) to the information that ELCA provides is almost impossible in the current conditions. Taking into consideration the aforementioned information, the goal of this PhD Research was to present the first estimates regarding the environmental performance of important livestock production systems in Greece (i.e. raw milk supply chains from dairy cattle farming and sheep and goat farming, animal live-weight supply chain from pig farming and broiler farming), by focusing on collecting data from commercial livestock farms and implementing the LCA methodology (adjusting the LCA methodology to case studies). Throughout the Thesis, focus was given on the compilation of life cycle inventories and models for the studied systems. In the case that more than one supply chain systems are involved, this research attempted to identify the reasons for variations in the environmental performance. This PhD Research further attempted to assess the effect of targeted modifications in livestock production practices (and more specifically in the rations of broiler chickens and fattening pigs) which are interesting for Greece but also on a global level, on the environmental performance of the respective supply chain systems. Within this Thesis, a discussion on how Precision Livestock Farming (PLF) technologies could be used in combination with the ELCA methodology in an effort to improve the environmental performance of a livestock product, was further initiated. Finally, in the framework of this PhD Research two easy-to-use tools for environmental impact assessment by using the LCA methodology (calculators for Greek intensive broiler and sheep and goat production processes) were developed.This PhD Thesis consists of 5 separate sections. In Section 1, an introduction to the legislative framework regarding environmental protection in the EU was presented, the importance of studying the environmental impacts of livestock systems was discussed, principles and important definitions of the ELCA methodology were given and the goals of this PhD Research were set. The rest of the sections constitute the core of this PhD research.The aim of Section 2 was to use a ‘cradle-to-farm-gate’ ELCA in order to estimate the environmental performance of the supply chain of the cow-milk produced in a dairy cattle farm located in the Region of Thessaly, Greece. The functional unit was equal to 1kg of Fat and Protein Corrected Milk (FPCM). This section also aimed to discuss a possible link between the ELCA methodology and Precision Livestock Farming technologies. The results of the Life Cycle Inventory (LCI) revealed that the enteric fermentation of cattle, the excretion and storage of manure and slurry application in ryegrass production were the most important contributing processes at the farm level to the total methane, nitrous oxide and ammonia emissions in this partial life-cycle of cow-milk. The Life Cycle Impact Assessment (LCIA) results suggested the following environmental hot spots for the studied supply chain and for the various impact categories studied (i.e. climate change, fossil fuel depletion, human and ecological toxicity, acidification, eutrophication, water depletion and land use): a) enteric fermentation of cattle, b) on-farm slurry handling, c) soybean cultivation in foreign countries (Argentina, Brazil and USA), d) domestic electricity production and e) domestic production of maize grain and silage. It is finally argued that the ELCA method could be used complementarily with PLF technologies in an effort to improve the quality of environmental impact assessment results of the supply chains of livestock products.In the context of Section 3, an experimental study was conducted to examine the combined effects of adding a dietary protease, reducing the levels of soybean meal (SBM) and introducing corn gluten meal (CGM) in the ration of a group of broilers reared on a commercial Greek farm (Region of Central Macedonia). Five hundred forty chicks were divided into three dietary treatments with six replicates of thirty birds each. The first group (Control) was fed a conventional diet based on corn and soybean meal, containing 21% w/w crude protein (CP). The second group (Soy-Prot) was supplied a corn and SBM-based diet containing a lower level of CP (20% w/w) and 200 mg of the protease RONOZYME® Proact per kg of feed. The third group (Gluten-Prot) was fed a diet without soybean-related constituents which was based on corn and CGM and with CP and protease contents identical to those of the diet of the Soy-Prot group. Body weight, feed intake and feed conversion ratio (FCR) were evaluated. Furthermore, a partial ELCA was performed in order to assess the potential environmental performance of the systems defined by these three dietary treatments and identify their environmental hot-spots. The growth performance of the broilers supplied the Soy-Prot diet was similar to the broilers supplied the Control diet. However, the broilers which were fed the Gluten-Prot diet at the end of the trial showed a tendency (P≤0.010) for lower weight gain and feed intake compared to those of the Control diet. The ELCA suggested that the ammonia and nitrous oxide emissions due to litter handling constitute the farm level hot-spots for the Acidification and Eutrophication Potentials of the Control and Soy-Prot systems and the Global Warming Potential of the Gluten-Prot system, respectively. The Latin American soybean production and domestic corn production and lignite mining are important off-farm polluting processes for the studied life cycles. The Soy-Prot and Gluten-Prot systems both performed better than the Control system in nine of Environmental Impact Category Indicators assessed, with the respective differences being generally larger for the Gluten-Prot system. The environmental impact estimates are regarded as initial, indicative figures due to their inherent uncertainty. Overall, the results could be considered as positive indications in the effort to replace the conventional, soybean-dependent control diet in the specific broiler production system in an environmentally friendly way. In Section 3, an environmental footprint calculator appropriate for the intensive broiler live-weight supply chains in Greece was further developed, based on an attributional ‘cradle-to-farm-gate’ ELCA methodology. It consists of an MS excel workbook whose user is invited to provide a number of inputs concerning the animal capital grown, its nutrition, the bedding material used, transport distances and fuel and electricity consumption. As a result, ten environmental impact category indicators (EICI’s) are estimated, among which the Acidification Potential (AP), the Eutrophication Potential (EP), the Cumulative Energy Demand (CED) and the Global Warming Potential (GWP100).In Section 4, an in situ experimental procedure was performed in order to investigate the effect of supplementing the conventional diet (CNVD) supplied to the fattening pigs of a commercial pig farm in Greece (located in Epirus Region) (based on maize, barley, wheat bran and soybean meal) with 0.4% w/w attapulgite and 0.5% w/w benzoic acid at the expense of maize (ATTBAD diet) on their feed efficiency and growth performance. The results suggested a significant increase (p≤0.05) in the weight gain (TWG) and the slaughter live-weight and a significant decrease (p≤0.05) in the feed intake (FI) and feed conversion ratio per fattening pig when supplied the ATTBAD. These results were further used as an input to a ‘cradle-to-farm-gate’ environmental Life Cycle Assessment (ELCA). The functional unit (FU) was 1 kg of sold pig live-weight and the environmental impact categories (EICs) assessed were climate change (CC) and CC from direct land use change, acidification, eutrophication, land use, water use and fossil energy use. The indicators for all EICs (EICIs) were

OBJECTIVE:To assess the gingival parameters in the clear aligner treatment versus the three other types of brackets, i.e., conventional metal, conventional ceramic, and metal self-ligating.MATERIALS AND METHODS:Eighty patients coming for regular appointments undergoing orthodontic treatment were included. They were further divided into four groups with 20 patients in each: Group one underwent conventional brackets (CB) treatment; Group two had conventional ceramic brackets (CCB); Group three was treated with self-ligating (SL) brackets; Group four underwent with clear aligner (CA) treatment. Inclusion criteria were any patient with a minimum age of 18 years having Class II, Class III skeletal relationship, undergoing orthodontic treatment for at least 6 months with fixed orthodontic appliances (FOA) on both arches. While smokers, pregnant, diabetics, or those taking medication affecting gingival health or having cardiovascular diseases were excluded. Also excluded were patients who used antiseptic solutions or mouthwash during the past 6 months, underwent any periodontal treatments in the past 6 months, or who had fixed bridges and crowns or extensive restorations close to the gingival margins. Seven indices, namely plaque index, gingival index, gingival bleeding index, sulcus bleeding index, papillary bleeding index, basic periodontal examination index, and bleeding on probing index, were recorded for all groups.RESULTS:Mean age for Group 1 with CB was 26.65 ± 5.15 years, whereas it was 27.65 ± 8.15 years for Group 2 with CCB, and 26.85 ± 5.19 for Group 3 with SB. Group-4 with CA treatment had a mean age of 26.85 ± 4.83 years. Multivariate analysis and a Bonferroni correction was performed (P = 0.008). CA treatment has better periodontal parameter values compared with the CB and the CCB groups, and no significance difference with the SL brackets group.CONCLUSION:CA treatment has better periodontal indices levels compared to other types of orthodontic treatments such as CB and the CCB groups; no significant difference with the SL brackets group. Importance should be given to oral hygiene instructions before, during, and after the treatment.

BackgroundTo evaluate the incidence and severity of open gingival embrasures (OGEs) in adult patients treated with clear aligners and fixed appliances.MethodsTwo hundred non-extraction adult subjects with less than 5 mm of crowding (mean age, 24.6 ± 3.8 years) were enrolled in this retrospective study. The subjects were divided into the clear aligner (n = 100) and fixed appliance group (n = 100). The intraoral photographs were utilized to determine the incidence of OGEs in the upper arch between maxillary central incisors, as well as the lower arch between mandibular central incisors. Crown overlap, crown shape, posttreatment root angulation, the distance from the interproximal contact point (ICP) to the alveolar bone crest (ABC) after treatment and interproximal enamel reduction (IPR) were determined in the two groups.ResultsThe incidence of OGEs between maxillary and mandibular central incisors after orthodontic treatment was 35.0% and 38.0% in the clear aligner group, respectively, significantly higher than that (18.0% and 24.0%) in the fixed appliance group (P < 0.05). The average area of an OGE after clear aligner treatment was larger both in the maxilla (0.16 ± 0.12mm2) and mandible (0.21 ± 0.24mm2) compared with that (0.05 ± 0.03mm2 and 0.05 ± 0.06mm2) after fixed appliance treatment (P < 0.05). No difference was found regarding pretreatment crown overlap, crown shape, treatment duration, posttreatment root angulation, amount and distribution of IPR and the distance from ICP to ABC.ConclusionsThe incidence and severity of OGEs were higher in adults treated with clear aligners. Clinicians should be aware of the risk of OGEs during treatment with clear aligners.

ENVIRONMENTAL SYSTEM ANALYSIS FOR HORTICULTURAL CROP PRODUCTION

To assess the efficacy and efficiency of treatment in adolescents presenting with mild malocclusions, comparing outcomes using clear aligners to fixed appliances. Patients identified retrospectively and consecutively from one private practice had been treated with either clear aligners (Invisalign, Align Technology, Santa Clara, Calif) or fixed appliances (0.022 Damon, Ormco, Orange, Calif; n = 26/group). Assessments of occlusion were made using the American Board of Orthodontics Discrepancy Index (DI) for initial records and Cast-Radiograph Evaluation (CRE) for final records. Number of appointments, number of emergency visits, and overall treatment time were determined from chart reviews. Data were analyzed using Pearson's correlation, Wilcoxon rank tests, unpaired t-tests, and Chi-square tests, with significance set to P ≤ .05. Pretreatment, the aligner and fixed groups showed no significant difference in overall severity (DI: 11.9 ± 5.3 vs 11.6 ± 4.8) or in any individual DI category. Posttreatment scores showed finishes for the aligner group had fewer discrepancies from ideal relative to the fixed appliance group (CRE: 30.1 ± 8.3 vs 37.0 ± 9.3; P < .01). Patients treated with aligners had fewer appointments (13.7 ± 4.4 vs 19.3 ± 3.6; P < .0001), fewer emergency visits (0.8 ± 1.0 vs 3.6 ± 2.5; P < .0001), and shorter overall treatment time (16.9 ± 5.7 vs 23.4 ± 4.4 months; P < .0001). Outcomes for treatment of mild malocclusions in adolescents showed equivalent effectiveness of clear aligners compared to fixed appliances, with significantly improved results for clear aligner treatment in terms of tooth alignment, occlusal relations, and overjet. Assessment of the number of appointments, number of emergency visits, and overall treatment time showed better outcomes for treatment with clear aligners.

Background, aim and scope Regional specificities are a key factor when analyzing the environmental impact of a biofuel pathway through a life cycle assessment (LCA). Due to different energy mixes, transport distances, agricultural practices and land use changes, results can significantly vary from one country to another. The Republic of Argentina is the first exporter of soybean oil and meal and the third largest soybean producer in the world, and therefore, soybean-based biodiesel production is expected to significantly increase in the near future, mostly for exportation. Moreover, Argentinean biodiesel producers will need to evaluate the environmental performances of their product in order to comply with sustainability criteria being developed. However, because of regional specificities, the environmental performances of this biofuel pathway can be expected to be different from those obtained for other countries and feedstocks previously studied. This work aims at analyzing the environmental impact of soybean-based biodiesel production in Argentina for export. The relevant impact categories account for the primary non-renewable energy consumption (CED), the global warming potential (GWP), the eutrophication potential (EP), the acidification potential (AP), the terrestrial ecotoxicity (TE), the aquatic ecotoxicity (AE), the human toxicity (HT) and land use competition (LU). The paper tackles the feedstock and country specificities in biodiesel production by comparing the results of soybean-based biodiesel in Argentina with other reference cases. Emphasis is put on explaining the factors that contribute most to the final results and the regional specificities that lead to different results for each biodiesel pathway.

The aim of this study was to investigate the factors that influence the sustainability of disposable baby diapers (nappies) using life cycle assessments (LCAs). Size 4 Pampers® Cruisers (North American name) and ActiveFit (European name) from 2007 are compared to new versions made in 2010 to determine if the design and materials changes intended to improve performance also lead to reductions in the most relevant environmental indicators. Cradle-to-grave LCAs, consistent with ISO 14040/14044 Standards, are conducted. The functional unit is “the number of diapers needed to collect excreta over a child’s diapering lifetime.” Input data come from P&G, suppliers, trade association reports, Franklin and ecoinvent databases, and Google. SimaPro 7 is used to model the LCA. Several life cycle impact assessments (LCIA) methods, sensitivity analyses, normalization to annual consumption, and Monte Carlo analysis are used to produce and check results. The consumption normalization identified that the diaper’s “environmental footprint” should include the IMPACT2002+ indicators: nonrenewable energy, global warming potential (GWP), respiratory effects from inorganics, total solid waste, and cumulative energy demand (CED). Other indicators are insignificant. Contribution analysis shows that the sourcing and production of diaper materials contribute most to the environmental indicators evaluated, accounting for ∼84% of all non-renewable energy uses and ∼64% of global warming potential. Diaper disposal is a small contributor (1–12%) to potential environmental impacts. Reductions observed for the 2010 US product are: CED—8%, solid waste—12%, non-renewable energy—1%, GWP500—4%, and respiratory inorganics—6%. For the European product, reductions are: CED—11%, solid waste—8%, non-renewable energy—3%, GWP500—5%, and respiratory inorganics—14%. The new Pampers® diapers sold in the USA and Europe have a reduced environmental footprint versus the previous versions (2007). Significant reductions are achieved in non-renewable energy use and global warming potential, as well as other environmental indicators by optimizing the diaper design and the materials. Although some of the results are single digit reductions, Monte Carlo analysis indicates that there is a high probability that the differences are real. The use of multiple LCIA methods to compare products is helpful to confirm consistency of results. Normalizing the LCIA scores to annual consumption also helps prioritize which environmental indicators can be impactful and affected by changing a product.

This study sought to systematically review the literature to determine whether clear aligner treatment results in different patient perceptions of treatment process and outcomes compared with conventional fixed appliance treatment. A systematic review was conducted to identify studies that examined differences in patient perceptions between clear aligners and conventional fixed appliance treatment. Studies were identified through searching relevant terms using PubMed and Embase. Following review of identified articles, key information about the studies including study design, setting, comparison groups, sample size/response rate, study location, primary outcomes, and statistical tests used were extracted. A total of 13 articles were identified that met the inclusion criteria for this study. These studies described a variety of outcomes which were divided into two broad categories: treatment process (pain, chewing, speech, daily routine, etc.) and treatment outcomes (satisfaction level, smile outcome perceptions, etc.). There was the strongest evidence that clear aligners had a positive impact with respect to treatment process compared with fixed orthodontic appliances. This study highlights that clear aligners may be effective for improving treatment-process-related outcomes among orthodontic patients. More studies need to be conducted to determine whether clear aligners have a beneficial impact with respect to treatment outcomes.

Optimizing the environmental sustainability of alternative post-harvest scenarios for fresh vegetables: A case study in Spain

Clear aligners have been frequently applied in orthodontic clinic practice. However, its effect on oral health-related quality of life (OHRQoL) compared with fixed appliance treatment (FAT) remains inconclusive. This systematic review aimed to compare the impacts of clear aligner treatment (CAT) with FAT on patients' OHRQoL. Electronic searches of databases (PubMed, Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, Embase, Medline, two Chinese databases and six grey literature databases) were conducted up to July 2019. Randomized controlled trials, controlled clinical trials, cohort studies and cross-sectional studies comparing the impact of CAT and FAT on OHRQoL with validated instruments were included. Extraction of data and assessment of the risk of bias were conducted using ROBINS-I-tool, Newcastle-Ottawa Scale and ROB 2.0 based on study design. Of the 1112 records initially identified, 2 studies were included in this review. One study evaluated OHRQoL at the last debonding appointment, while the other made evaluation at the early stage of treatment. In the aspect of functional dimensions, both studies reported less eating disturbance in CAT patients than FAT ones. Based on currently limited information, the effect of CAT on the overall OHRQoL compared to FTA was still inconclusive. In individual dimensions, however, weak evidence supported that CAT might cause less eating disturbance than FAT. More high-quality clinical trials using validated OHRQoL instruments are needed to draw more reliable conclusions in the effect of CAT and FAT on OHRQoL.