Journal of

Oral Rehabilitation

Journal of Oral Rehabilitation 2014 41; 897--903

The influence of fixed orthodontic appliances on masticatory and swallowing threshold performances ~ S*, L. J. PEREIRA†, A. S. ANDRADE‡, D. B. GOUVEA§ & I . B . M A G A L H AE G. H. GAMEIRO§ *Department of Clinical Dentistry, Vale do Rio Verde University – UNINCOR, Tres Coracoes, †Department

of

Physiology and Pharmacology, Federal University of Lavras – UFLA, Lavras, ‡Department of Pediatric Dentistry, State University of Campinas – UNICAMP, Piracicaba, and §Department of Physiology, Federal University of Rio Grande do Sul – UFRGS, Porto Alegre, Brazil

SUMMARY 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

Introduction Although the aesthetic characteristics of malocclusions are the main factor in determining orthodontic treatment demand (1, 2), it is well known that individuals with malocclusions also complain about functional problems, such as mastication difficulty, which is usually resolved after orthodontic treatment (3). Mastication is the first step in the process of digestion; mechanical degradation of food facilitates the action of the salivary enzymes and is meant to prepare the food for swallowing and further processing in the digestive system (4). This oral function can be objectively evaluated by determination of masticatory performance, which pertains to the particle size © 2014 John Wiley & Sons Ltd

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. KEYWORDS: malocclusion, masticatory performance, orthodontics, deglutition, pain, occlusion Accepted for publication 31 July 2014

distribution of food that is chewed for a standard number of cycles (5). Several factors potentially influence masticatory performance, including bite force, occlusal contact area, number of functional tooth units and malocclusion severity (6–8). Malocclusions negatively affect subjects’ ability to process and break down foods, and although the orthodontic and/or surgical correction of malocclusions usually improves this problem, masticatory performance is still impaired compared to subjects with normal occlusion (3, 9). However, only a few studies on masticatory problems of patients undergoing orthodontic treatment have been performed. Some have shown that almost all of the patients report moderate to extreme difficulty in chewing and biting doi: 10.1111/joor.12218

898

~ S et al. I . B . M A G A L H AE foods of a firm-to-hard consistency, and this caused them to change the consistency of their diet (10, 11), although statistically non-significant results have also been reported (12). Orthodontic pain is probably the main factor responsible for the masticatory limitations associated with fixed appliances. After 24 h, pain is reported by up to 95% of orthodontic patients undergoing treatment (13, 14), but it usually resolves by the 7th day after appliance activation (14). The pain experienced within the first 48 h is so disturbing that approximately 20% of patients report being awakened at night; some of them take medication, and almost all of them report difficulty with eating due to pain (13, 14). Despite the clinical relevance of orthodontic pain, the methodological approaches to analyse the effects of pain on mastication and deglutition in patients during orthodontic therapy are very limited. A qualitative study of the early effects of fixed orthodontic treatment on dietary intake and behaviour in adolescent patients showed that during the first few days after appliance placement, the majority of individuals adopted a soft diet because it was easier to chew and less painful (15). In fact, orthodontic pain is significant enough to reduce masticatory muscular activity 48 h after archwire activation (16). However, the masticatory and swallowing performances (regarding the median size of crushed particles) of orthodontic patients were not evaluated in previous studies. These analyses are necessary considering not only the pain, but also the fear of breaking the brackets could affect the masticatory function of orthodontic patients. Moreover, patients normally overestimate their masticatory ability when they are only evaluated by subjective methods (17). It is important to point out that the use of fixed appliances to correct malocclusions can involve occlusal interferences and discomforts associated with orthodontic movement, which could temporarily alter masticatory and swallowing performances. However, this hypothesis was not substantiated by controlled experimental studies. This study was designed to investigate the effects of fixed orthodontic appliances on masticatory and swallowing performances during orthodontic treatment.

Materials and methods Twenty-seven healthy subjects (14 men and 13 women, aged 21
1  10
4 years) participated in this

prospective longitudinal study. The participants were selected from private practice offices after an initial screening examination, and the following inclusion criteria were considered: approximately equal number of males and females and an approximately equal number of occlusal units with malocclusions requiring orthodontic treatment. Twelve individuals had Class I malocclusions, nine had Class II and six had Class III. Bonding of at least 10 teeth in the maxillary arch and 0
012, 0
014 (NiTi) and 0
016 (stainless steel) inches archwires were used during the experimental period (the archwires were changed every month). Only one orthodontist (IBM) performed the treatments. No extractions were performed during this period, and no patients reported taking analgesics during the study. The exclusion criteria were previous orthodontic treatment or symptoms of temporomandibular joint dysfunction. Informed written consent was obtained from all participants prior to their enrolment in the study. The local ethics committee approved the protocol. Sample size was determined based on clinically relevant masticatory performance data from the literature (6, 18), with a power of 90% and a = 0
05. Ultimately, 27 individuals were deemed ideal for this longitudinal study. We started with 30 individuals, but 3 were excluded due to bracket breakages during the study. To evaluate masticatory performance, patients were instructed to habitually chew the artificial test food, Optocal, for 15 chewing strokes. This test food is based upon the silicone component Optosil Plusâ* and consists of a mixture of the following materials: mixing condensation silicone (58
3% by weight), common plaster (10
2% by weight), alginate (12
5% by weight), solid vaseline (11
5% by weight), tooth paste (7
5% by weight) and catalyst paste (20
8 mg g 1) (6). This test food is much easier to chew than Optosil, and orthodontic patients judged its texture to be comparable with that of natural foods they usually consumed in periods when they experienced pain. The test food was offered in portions of 17 cubic particles with an edge size of 5
6 mm, corresponding to approximately 3 cm3 (3
2 g). After 15 strokes, the patients spat the particles into a plastic cup, rinsed their mouth with water and spat the remaining mouth contents until all particles were

*Heraeus Kulzer GmBH, Hanau, Germany. © 2014 John Wiley & Sons Ltd

ORTHODONTIC APPLIANCES AND MASTICATORY PERFORMANCE Table 1. Mean/standard deviation (SD) of masticatory performance (X50), pain experience (VAS, in mm) and body variables at the five experimental 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) Variables

T0

T1

T2

T3

T4

Masticatory Performance (X50) VAS Age (years) Weight Height BMI

5
62a/1
03

5
89a/1
07

7
45b/2
88

5
93a/1
43

5
93a/1
45

10
96a/17
24 21
15/10
41 58
67a/19
59 1
62a/0
11 22
02a/5
76

22
54b/20
25 21
15/10
41 58
65a/19
56 1
62a/0
11 22
01a/5
76

52
72c/34
35 21
15/10
41 58
38a/19
19 1
62a/0
11 21
91a/5
60

17
81ab/22
97 21
15/10
41 58
15a/19
21 1
62a/0
11 21
82a/5
61

7
44a/15
52 21
41/10
52 58
72a/18
72 1
62a/0
11 22
05a/5
40

Distinct letters indicate statistical difference (Friedman/Dunn or repeated measures

removed. The particles were washed and dried for 24 h in a stove at 60 °C. After that, they were sieved through a stack of up to 10 sieves, with square apertures decreasing from 5
6 to 0
5 mm, for 5 min. Median particle sizes (X50) were determined as previously described (19). X50 is defined as the aperture of a theoretical sieve through which 50% of the weight can pass. Disturbances in performance are detected by an increase in the X50 value. Swallowing threshold tests were performed with both a test and a natural food. The term swallowing threshold can be represented by different variables: (i) the median particle size (X50 determined as previously described) of the crushed particles that were expectorated just before a subject felt the need to swallow, and (ii) time and (iii) number of strokes needed to prepare the food for swallowing. In this study, these three swallowing thresholds were registered for the artificial food. Optocal was chosen as the artificial food because it is much easier to chew than others artificial food (as Optosil or Cuttersil), and patients judged its texture to be comparable with that of natural foods they usually consumed in periods of pain experience, such as cheese and boiled vegetables. For the natural food, we selected a food that was harder than the artificial one. We used unsalted medium-size peanuts (they are considered a harder food, such as raw carrots and apples) that were offered in portions of 6 g (6 cm3). Subjects were instructed to eat and swallow the food as usual, and the swallowing thresholds (time and number of strokes) were also registered. Pain was evaluated by a 100-mm visual analogue scale (VAS), and subjects were asked to mark their degree of discomfort (0, no pain; 10, worst pain © 2014 John Wiley & Sons Ltd

ANOVA/Tukey’s

test, P < 0
05).

imaginable) immediately after the masticatory performance test with artificial food. Body weight, height and body mass index (weight per height2) were also registered. The tests 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). Shapiro–Wilks tests were used to verify data normality. Variables that were normally distributed were analysed by repeated measures analysis of variance (ANOVA) with post hoc Tukey’s tests, and the X50 for masticatory performance and VAS scores were analysed by Friedman tests and Dunn’s tests because they were not normally distributed. SPSS software† was used for all analyses, and the significance level was set at P < 0
05. The X50 data of 10 subjects with the same age were also analysed with the Dahlberg formula ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi pP EM = d2 =2n and paired t-tests after two analyses with a 7-day interval. There was no statistical difference between the evaluations (P > 0
05), and the reproducibility error was