To test the hypothesis that treatment with orthodontic appliances disturbs masticatory and swallowing performances. Twenty-seven subjects with malocclusions requiring orthodontic treatment were included in this prospective study. The masticatory and swallowing performances were evaluated at five different times: before bracket placement (T0), immediately after archwire placement (T1), 48 h after archwire placement (T2), 30 days after archwire placement (T3) and 3 months after the initial appointment (T4). Masticatory performance was determined by the median particle sizes for the Optocal test food after 15 chewing strokes, and the swallowing thresholds were registered for both the test food and a natural food (peanuts). Pain during mastication was evaluated using a 100-mm visual analogue scale. Masticatory performance was significantly reduced at T2, at which time patients reported the highest pain values. The time spent to the first swallow was increased at T2 for the natural food but not for the test food. The values for pain, masticatory and swallowing performances at T3 and T4 were similar to those at T0. Orthodontic patient masticatory function is only reduced during the period of higher pain experience, which could also disrupt the deglutition of harder foods. However, neither mastication nor deglutition processes were disturbed by orthodontic appliances in long-term treatment.4112897903Mandall, N.A., Wright, J., Conboy, F.M., O'Brien, K.D., The relationship between normative orthodontic treatment need and measures of consumer perception (2001) Community Dent Health, 18, pp. 3-6Reichmuth, M., Greene, K., Orsini, M., Cisneros, G., King, G., Kiyak, A., Occlusal perceptions of children seeking orthodontic treatment: impact of ethnicity and socioeconomic status (2005) Am J Orthod Dentofacial Orthop, 128, pp. 575-582Henrikson, T., Ekberg, E., Nilner, M., Can orthodontic treatment improve mastication? A controlled, prospective and longitudinal study (2009) Swed Dent J, 33, pp. 59-65van der Bilt, A., Engelen, L., Pereira, L.J., van der Glas, H.W., Abbink, J.H., Oral physiology and mastication (2006) Physiol Behav, 89, pp. 22-27Bates, J.F., Stafford, G.D., Harrison, A., Masticatory function - a review of the literature (1976) J Oral Rehabil, 3, pp. 57-67Fontijn-Tekamp, F.A., Slagter, A.P., van der Bilt, A., Van'T Hof, M.A., Witter, D.J., Kalk, W., Biting and chewing in overdentures, full dentures, and natural dentitions (2000) J Dent Res, 79, pp. 1519-1524English, J.D., Buschang, P.H., Throckmorton, G.S., Does malocclusion affect masticatory performance? (2002) Angle Orthod, 72, pp. 21-27Magalhães, I.B., Pereira, L.J., Marques, L.S., Gameiro, G.H., The influence of malocclusion on masticatory performance. A systematic review (2010) Angle Orthod, 80, pp. 981-987van den Braber, W., van der Bilt, A., van der Glas, H., Rosenberg, T., Koole, R., The influence of mandibular advancement surgery on oral function in retrognathic patients: a 5-year follow-up study (2006) J Oral Maxillofac Surg, 64, pp. 1237-1240Bergius, M., Kiliaridis, S., Berggren, U., Pain in orthodontics. A review and discussion of the literature (2000) J Orofac Orthop, 61, pp. 125-137Brown, D.F., Moerenhout, R.G., The pain experience and psychological adjustment to orthodontic treatment of preadolescents, adolescents, and adults (1991) Am J Orthod Dentofacial Orthop, 100, pp. 349-356Erdinç, A.M., Dinçer, B., Perception of pain during orthodontic treatment with fixed appliances (2004) Eur J Orthod, 26, pp. 79-85Kvam, E., Gjerdet, N.R., Bondevik, O., Traumatic ulcers and pain during orthodontic treatment (1987) Community Dent Oral Epidemiol, 15, pp. 104-107Scheurer, P.A., Firestone, A.R., Bürgin, W.B., Perception of pain as a result of orthodontic treatment with fixed appliances (1996) Eur J Orthod, 18, pp. 349-357Abed Al Jawad, F., Cunningham, S.J., Croft, N., Johal, A., A qualitative study of the early effects of fixed orthodontic treatment on dietary intake and behaviour in adolescent patients (2012) Eur J Orthod, 34, pp. 432-436Goldreich, H., Gazit, E., Lieberman, M.A., Rugh, J.D., The effect of pain from orthodontic arch wire adjustment on masseter muscle electromyographic activity (1994) Am J Orthod Dentofacial Orthop, 106, pp. 365-370Van Der Bilt, A., Assessment of mastication with implications for oral rehabilitation: a review (2011) J Oral Rehabil, 38, pp. 754-780Sierpinska, T., Golebiewska, M., Dlugosz, J., Kemona, A., Laszewicz, W., Connection between masticatory efficiency and pathomorphologic changes in gastric mucosa (2007) Quintessence Int, 38, pp. 31-37van der Bilt, A., van der Glas, H.W., Mowlana, F., Heath, M.R., A comparison between sieving and optical scanning for the determination of particle size distributions obtained by mastication in man (1993) Arch Oral Biol, 38, pp. 159-162Jones, M., Chan, C., The pain and discomfort experienced during orthodontic treatment: a randomized controlled clinical trial of two aligning archwires (1992) Am J Orthod Dentofacial Orthop, 102, pp. 373-381Fontijn-Tekamp, F.A., van der Bilt, A., Abbink, J.H., Bosman, F., Swallowing threshold and masticatory performance in dentate adults (2004) Physiol Behav, 83, pp. 431-436Pera, P., Bucca, C., Borro, R., Bernocco, C., De, L.A., Carossa, S., Influence of mastication on gastric emptying (2002) J Dent Res, 81, pp. 179-181Holt, S., Reid, J., Taylor, T.V., Tothill, P., Heading, R.C., Gastric emptying of solids in man (1982) Gut, 23, pp. 292-296Poitras, P., Boivin, M., Morais, J., Picard, M., Mercier, P., Gastric emptying of solid food in edentulous patients (1995) Digestion, 56, pp. 483-487Hattori, Y., Mito, Y., Watanabe, M., Gastric emptying rate in subjects with experimentally shortened dental arches: a pilot study (2008) J Oral Rehabil, 35, pp. 402-407