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The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery
Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e5
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The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery Koichiro Ueki*, Kohei Marukawa, Akinori Moroi, Megumi Sotobori, Yuri Ishihara, Ran Iguchi, Akihiko Kohsaka, Yoshio Nakano, Masatoshi Higuchi, Ryuichi Nakazawa, Hiroumi Ikawa Department of Oral and Maxillofacial Surgery (Head: Prof. Dr. K. Ueki), Division of Medicine, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 1110 Shimokato, Chuo-shi, Yamanashi 409-3898, Japan
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 15 May 2013 Accepted 3 January 2014
Objectives: The purpose of this study was to examine the changes with time in lip pressure after orthognathic surgery for skeletal Class III patients. Study design: The subjects consisted of 63 patients (32 female and 31 male) diagnosed with mandibular prognathism who underwent sagittal split ramus osteotomy with and without Le Fort I osteotomy. Maximum and minimum lip closing forces were measured with Lip De CumÒ. The changes with time were compared statistically. Results: The maximum and minimum lip closing force increased time-dependently in men and women after surgery and there were significant differences between men and women with changes with time in the maximum lip closing force (p ¼ 0.0086) and the minimum lip closing force (p ¼ 0.0302). After 1 year, the Class III group maximum lip closing force was significantly smaller than the control group in both men (p < 0.0001) and women (p < 0.0001). Conclusions: This study suggests that there was significant difference in over time in the lip closing force between men and women in Class III patients. Although the maximum lip closing force increased with time, it did not reach the level of the control group after 1 year. Ó 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Lip closing force Mandibular prognathism Orthognathic surgery
1. Introduction Lip-closing function can be achieved by various types and various amounts of lip-closing movements, depending on the physiological behaviour required. Lip closing movements are not simple tasks like eye blinking, but complex and well-organized tasks that are performed by the orbicularis oris muscle, with additional facial muscles that have muscle fibres in various directions, around the orifice of the mouth. The orbicularis oris muscle is a sphincter muscle composed of two parts in the upper and lower lips (Standring, 2005). Most dental professionals accept the theory of Tomes (Tomes, 1973), who asserted that opposing forces or pressure from the lips and cheeks on one side and the tongue on the other, determine the position of the teeth (Mitchell and Williamson, 1978; Posen 1976).
* Corresponding author. Tel./fax: þ81 55 273 6761. E-mail addresses: [email protected], [email protected] (K. Ueki).
In some patients with maxillary protrusion or severe Class II Division 1 malocclusion, lip incompetency and muscle imbalance are seen (Gould and Piston, 1962; Posen, 1972, 1976). Posen (1976) found that subjects with bimaxillary protrusion have low lip strength, compared with Class I and Class II Division 2 patients, using a device for measuring the strength of the lips. Ruan et al. (2007) reported that patients aged 4e6 years with Class III malocclusion had lower perioral forces and this muscle hypofunction might be secondary to the spatial relation of the jaws. There are some studies regarding morphological changes following orthognathic surgery (Ueki et al., 2012b,c; Ueki et al., 2013). Orthognathic surgery induces not only morphological but also functional changes. Surgical orthodontic correction of skeletal class III physiology reportedly has favourable effects on the function of the mandible, such as an increased range of maximum motion in the anterior, posterior, and lateral excursions (Nagamine et al., 1993). Several studies have examined the opening and closing movements (Aragon et al., 1985; Boyd et al., 1991) as well as the chewing rhythm and path (Ueki et al., 2005, 2007).
1010-5182/$ e see front matter Ó 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jcms.2014.01.007
Please cite this article in press as: Ueki K, et al., The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.01.007
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K. Ueki et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e5
There had been no report regarding lip closing force in Class III patients following orthognathic surgery until our previous study, which showed that maximum lip closing force at 6 months postoperative increased more than the preoperative value after orthognathic surgery in Class III patients (Ueki et al., 2012a). It was unclear whether the lip closing force continued to increase 1 year after surgery and whether there was a significant difference in the change between men and women with time. The purpose of this study was to compare the temporal changes in lip pressure after orthognathic surgery between male and female skeletal Class III patients. 2. Patients and methods 2.1. Patients The subjects consisted of 31 men (average age, 25.5 7.7 years) and 32 women (average age, 32.9 12.5 years) with Class III malocclusion. All cases were diagnosed as skeletal class III, including mandibular prognathism and/or maxillary retrognathism on the basis of a lateral cephalogram analysis. All the patients underwent orthognathic surgery. Control groups consisted of 20 women (average age, 29.5 4.9 years) and 20 men (average age, 29.5 3.9 years) with normal occlusion without dento-alveolar deformity. Although this was a retrospective study, informed consent was obtained from the patients and the study was approved by Kanazawa University Hospital. 2.2. Measurement of lip closing force Maximum and minimum lip closing forces were measured with Lip De Cum LDC-110RÒ (Cosmos instruments Co. LTD, Tokyo, Japan) (Fig. 1) for the control groups and subject groups preoperatively and at 6 months and 1 year postoperatively. This device consists of a sensor with a lip adaptor and digital display (Noro et al., 2002). The Lip Closure Strength (force) Indicator (Lip De CumÒ) was set up with a Lip holder (DucklingsÒ) mounted to the sensor, and the subject was instructed to bite the holder between the upper and lower lips. Following this the Lip Closure Strength (force) of the subject was measured while the subject was sitting upright (with the FH plane parallel to the floor plane). The subject was instructed to close the upper and lower lips with utmost strength without allowing the upper and lower teeth to touch. The device contains 4 strain gauges at the sensor and converts the measurement value
Fig. 1. Lip Closure Strength (force) Indicator (Lip De CumÒ) with a Lip holder (DucklingsÒ).
into load value (N). During a measurement lasting for 30 s, the shape of the wave is shown on the display of a personal computer connected to the Lip De CumÒ. In the wave, the largest and smallest values were respectively defined as the maximum and minimum values (Fig. 2).
2.2.1. Cephalogram assessment The cephalograms were entered into a computer and analysed using appropriate computer software (Cephalometric Ato Z, Yasunaga Labo Com, Fukui, Japan). Measurements landmarks were as follows, SNA, SNB, ANB, FMA, IMPA, FMIA, U1 to FH plane, Gonial angle, Ramus inclination (FH), Occlusal plane (FH), Interincisal angle, Mandibular length (Co-Gn), Incisor overjet, Incisor over bite, Convexity, S-A parallel to SN (distance between Sella and A-point parallel to SN plane), S-A perpend SN (distance between Sella and A-point perpendicular to SN plane), S-PNS parallel to SN (distance between Sella and PNS parallel to SN plane), S-PNS perpend to SN (distance between Sella and PNS perpendicular to SN plane), S-ANS parallel to SN(distance between Sella and ANS perpendicular to SN plane), S-ANS perpend to SN (distance between Sella and ANS perpendicular to SN plane). These measurements were used to examine which variants significantly correlated to maximum lip closing force using stepwise regression analysis. One skilled observer performed all digitization so that errors in the cephalometric method were small and acceptable for the purposes of this study. Error analysis by digitization and remeasurement of 10 randomly selected cases generated an average error of less than 0.4 mm for the linear measurements and 0.5 for the angular measurements.
2.2.2. Statistical analysis Data were statistically analysed with. SPSSII (SPSS Japan Inc., Tokyo, Japan). Total changes with time from pre-operation to 1 year after surgery were examined by analysis of variance (ANOVA). Comparisons between men and the women in each time period were performed and adjusted using Bonferroni correction. Stepwise regression analysis was carried out to examine the morphological factors affecting the maximum lip closing force. The differences were considered significant at p < 0.05.
Fig. 2. The recorded wave of the lip closing force for 30 s.
Please cite this article in press as: Ueki K, et al., The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.01.007
K. Ueki et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e5
3
3. Results
3.1. Comparisons between men and women in each period
18 of 31 men with mandibular prognathism underwent Le Fort I osteotomy with bilateral sagittal split ramus osteotomy (SSRO) and 13 underwent bilateral SSRO alone.12 of 32 women with mandibular prognathism underwent Le Fort I osteotomy with bilateral SSRO, 20 underwent bilateral SSRO. The mean setback amount by SSRO with and without Le Fort I osteotomy was 6.4 3.5 mm on the right side and 5.6 3.8 mm on the left side in men, and 5.8 3.5 mm on the right side and 6.1 3.6 mm on the left side in women. There were no significant differences in setback amount between men and women. When the post-operative recording at 6 months and 1 year was performed, the occlusion was normal and stable in all patients. Preoperative maximum and minimum lip closing forces (mean and standard deviation) were 9.4 2.1 and 3.4 1.4 (N) in Class III men group, 7.8 2.7 and 2.9 1.4 (N) in Class III women group, 15.0 1.8 and 6.8 0.9 (N) in control men group, and 12.7 1.1 and 6.2 1.0 (N) in control women group. Maximum and minimum lip closing force (mean and standard deviation) after 6 months were10.4 2.7 and 4.2 1.3 (N) in Class III men group, and 8.6 2.6 and 3.8 1.9 (N) in Class III women group. Maximum and minimum lip closing forces (mean and standard deviation) after 1 year were10.4 2.0 and 6.0 1.4 (N) in Class III men group, and 9.3 2.4 and 4.9 1.3 (N) in Class III women group. In Class III patients, there were significant differences between men and women in the l changes with time in the maximum lip closing force (repeated-measures ANOVA, between subjects F ¼ 7.379; df ¼ 1; p ¼ 0.0086; within subjects, F ¼ 20.046; df ¼ 2; p < 0.0001) and the minimum lip closing force (repeated-measures ANOVA, between subjects F ¼ 4.927; df ¼ 1; p ¼ 0.0302; within subjects, F ¼ 77.793; df ¼ 2; p < 0.0001) (Fig. 3 and Table 1). In the maximum lip closing force in men, the value after 6 months was significantly larger than preoperative value (p ¼ 0.0037) and the value after 1 year was still larger than preoperative value (p ¼ 0.0001). There was no difference between after 6 months and 1 year. In the maximum lip closing force in women, the value after 6 months and after 1 year were significantly larger than preoperative value (p ¼ 0.0273 and p < 0.0001) and the value after 1 year was larger than the value after 6 months (p ¼ 0.0304). In the minimum lip closing force in men, the value after 6 months was significantly larger than preoperative value (p ¼ 0.0004), the value after 1 year was larger than preoperative value (p < 0.0001) and the value after 1 year was larger than preoperative value (p < 0.0001). In the minimum lip closing force in women, the value after 6 months and after 1 year were significantly larger than preoperative value (p ¼ 0.0021 and p < 0.0001) and the value after 1 year was larger than the value after 6 months (p ¼ 0.0006). In summary, the maximum and minimum lip closing force increased with time in both men and women after surgery.
Before surgery, the maximum lip closing force in men was significantly larger than that in women in both the Class III group (p ¼ 0.0330) and control group (p ¼ 0.0097). Before surgery, the Class III group maximum lip closing force was significantly smaller than the control group in both men (p < 0.0001) and women (p < 0.0001). After 6 months, the Class III group maximum lip closing force was significantly smaller in the control group regarding both men (p < 0.0001) and women (p < 0.0001). The maximum lip closing force in men was significantly larger than that in women in the Class III group after 6 months (p ¼ 0.0225). After 1 year, the Class III group maximum lip closing force was significantly smaller than the control group in both men (p < 0.0001) and women (p < 0.0001). There was no significant difference between men and women in the Class III group after 1 year (p ¼ 0.1326). Before surgery, there was no significant difference regarding the minimum lip closing force between men and women in both the Class III and control groups, but the maximum lip closing force in the Class III group was significantly smaller than the control group in both men (p < 0.0001) and women (p < 0.0001). After 6 months, a similar tendency was shown. There was no significant difference in the minimum lip closing force between men and women in the Class III group and the Class III group showed a significantly smaller maximum lip closing force value than the control group in both men (p < 0.0001) and women (p < 0.0001). After 1 year, the minimum lip closing force in men was significantly larger than that in women in the Class III group (p ¼ 0.0147), but there was no significant difference between men in the Class III group and men in the control group, although the minimum lip closing force value for women in the Class III group was still smaller than that of the control group (p ¼ 0.0056) (Fig. 3 and Table 1). Statistical comparison between surgical procedures (SSRO group versus SSRO with Le Fort I osteotomy group) did not show any significant differences. Furthermore, there were no significant differences among the groups regarding the other procedures for lip closing force. Stepwise regression analysis showed the maximum lip closing force could be defined by an equation using only the morphological parameter as follows:
A
3.2. Pre-operation (Maximum lip closing force) ¼ 0.387e0.258 (ANB) þ 0.123 (S-ANS parallel to SN) (N ¼ 63, R ¼ 0.497, adjusted R2 ¼ 0.247, RMS Residual ¼ 2.257, F ¼ 9.832; p ¼ 0.0002).
B
Fig. 3. Result of the lip closing force. A) Maximum lip closing force, B) Minimum lip closing force. Error bars indicate standard deviation.
Please cite this article in press as: Ueki K, et al., The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.01.007
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K. Ueki et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2014) 1e5
Table 1 Results of the lip closing force. SD, indicates standard deviation. Pre-operative
Class III Men Class III Women Control Men Control Women
Mean SD Mean SD Mean SD Mean SD
After 6 months
After 1 year
Maximum (N)
Minimum (N)
Maximum (N)
Minimum (N)
Maximum (N)
Minimum (N)
9.4 2.1 7.8 2.7 15.0 1.8 12.7 1.1
3.4 1.4 2.9 1.4 6.8 0.9 6.2 1.0
10.4 2.7 8.6 2.6
4.2 1.3 3.8 1.9
10.4 2.0 9.3 2.4
6.0 1.4 4.9 1.3
3.3. After 1 year (Maximum lip closing force) ¼ 3.253 þ 0.105 (FMIA) þ 0.136 (S-PNS perpend to SN) (N ¼ 63, R ¼ 0.497, adjusted R2 ¼ 0.247, RMS Residual ¼ 2.008, F ¼ 9.829; p ¼ 0.0002). 4. Discussion Orthognathic surgery including orthodontic treatment can improve not only aesthetics but also function. Many studies have been published regarding occlusal force after orthognathic surgery (Harada et al., 2000; Ohkura et al., 2001; Ueki et al., 2009). Despite this there had been no knowledge regarding the lip closing force in skeletal class III patients. Our previous study showed that maximum lip closing force at 6 months postoperative increased more than the preoperative value after orthognathic surgery in Class III patients (Ueki et al., 2012a). However, it was unclear whether the lip closing force continued to increase at the period of 1 year after surgery and whether there was a significant difference in the temporal change between men and women. When the maximum lip closing force was measured and examined, it was necessary to recognize the difference between the sexes, with a higher lip pressure measured in men than in women. Kato et al. (1989) and Posen (1972) also demonstrated the same variation in the force with sex. The same trend was found by Ruan et al. (2005) who measured muscle pressure exerted on the primary normal occlusion and concluded that the primary dentition is in a state of dynamic equilibrium. In this study, there were significant differences between men and women in the changes with time in the maximum lip closing force and the minimum lip closing force. This suggests that increase in the lip closing force after surgery was also different between the sexes. Proffit described the primary and secondary force factors related to tooth position, and he concluded that pressure of the tongue and lips is one of the primary factors, but other factors are also related to equilibrium (Proffit, 1975; Proffit, 1978; Proffit et al., 2007). Thüer and Ingervall (1986) recorded, with a dynamometer, the lip pressure of 84 patients at rest and during chewing and swallowing of crisp bread. They found that a Class II division 2 malocclusion was not due to by a strong upper lip but that the incisor position was responsible for the low lip pressure in such patients. In contrast, the study of the maximum lip pressure during maximum voluntary contraction showed that lip pressure was lowest in children with a Class II division 2 malocclusion. Posen (1972) stated that great lip strength, measured with the pommeter (perioral muscle metre) during maximum voluntary contraction, can be an indication of high lip tonus and thus substantial outer forces are acting on the anterior teeth. The study showed that Class II division 2 subjects had high lip strength, while bimaxillary protrusion subjects had low lip strength, and the pressure in Class II division 1 subjects was lower than in subjects with
Class I occlusion. Lambrechts et al. (2010) found that the maximum lip pressure in Class II division 1 was lower than that in Class I, but there were no significant differences in the other comparisons (Class I, Class II division 1, Class II division 2 and Class III). Ruan et al. (2007) showed that paediatric patients (4e6 years old) with a Class III malocclusion generated lower perioral muscle forces. This may cause less bone apposition in this area, which aggravates the clinical features of Class III malocclusion. They postulated that their results reflected muscle hypofunction secondary to the spatial relationship of the jaw in Class III subjects, namely, retroposition of the maxilla. With regard to the change in lip, cheek and tongue pressures after rapid maxillary expansion (RME) using a diaphragm pressure lu (2003) reported that the transducer, Küçükkeles¸ and Ceylanog cheeks and lips almost adapt to a new position of the dental arches at the end of the third month, whereas tongue adaptation took comparatively longer. In their study, pressure values while patients were in the rest position increased significantly after RME and started decreasing by the end of the first month of retention. At the end of the third month, the values decreased to a level almost equal to their preexpansion values. The diaphragm pressure transducer was, however placed at the central incisor buccally, so that it could not be compared with the lip closing pressure that we performed in this study. It is important to measure the upper and lower lip closing forces separately in order to understand the muscle function in detail. However, the device used in this study could not measure the upper and lower lip closing force separately. Therefore, the data in this study are a measure of the total resultant force. In the previous study, Class III patients had significantly lower maximum lip closing force than those in the control group. This finding was similar to that of the previous study of Ruan et al. (2007). This suggested that the maximum lip closing force of Class III patients is weaker in both adults and children. Postoperative maximum lip closing force was significantly larger than the preoperative value in Class III patients in this study. With regard to the surgical procedure, there was no significant difference between SSRO alone and SSRO with Le Fort I osteotomy. This suggested that change in the maximum lip closing force was not related to the surgical procedure, and the skeletal and occlusal changes per se could increase the maximum lip closing force. However, at 1 year postoperative, the maximum lip closing force in the Class III patients was still smaller than that in the control group. Postoperative training of lip closure may play an important role in the maintenance of skeletal and occlusal stability. Jung et al. (2003) found that the values of lip closing forces were related to the variables of upper incisor angulation, and that in Class II were related to the vertical skeletal pattern, with Y-metre (measurement device of the vertical closing force of the upper lip). ANB and S-ANS parallel to SN were selected as related measurements to maximum lip closing force preoperatively. FMIA and SPNS perpend to SN were selected as related measurements to
Please cite this article in press as: Ueki K, et al., The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.01.007
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maximum lip closing force after 1 year surgery. These findings suggested that the region reflected by lip closing force was different in each skeletal and occlusal pattern. Furthermore, the region related to lip closing force could change after correction in skeletal and occlusal pattern. Further studies using larger sample number will be necessary. 5. Conclusion This study showed that the postoperative maximum lip closing force value increased more than the preoperative value after orthognathic surgery in Class III patients, although the postoperative value was significantly smaller than that of the control group. Ethical approval Not required. Competing interests None declared. References Aragon SB, Van Sickels JE, Dolwick MF, Flanary CM: The effects of orthognathic surgery on mandibular range of motion. J Oral Maxillofac Surg 43: 938e943, 1985 Boyd SB, Karas ND, Sinn DP: Recovery of mandibular mobility following orthognathic surgery. J Oral Maxillofac Surg 49: 924e931, 1991 Gould MS, Piston DC: A method of measuring forces acting on the teeth from the lips, cheeks and tongue. Br Dent J 174: 175e180, 1962 Harada K, Watanabe M, Okura K, Enomoto S: Measure of bite force and occlusal contact area before and after bilateral sagittal split ramus osteotomy of the mandible using a new pressure-sensitive device: a preliminary report. J Oral Maxillofac Surg 58: 370e373, 2000 Jung MH, Yang WS, Nahm DS: Effects of upper lip closing force on craniofacial structures. Am J Orthod Dentofacial Orthop 123: 58e63, 2003 Kato Y, Kuroda T, Togawa T: Perioral force measurement by a radiotelemetry device. Am J Orthod Dentofacial Orthop 95: 410e414, 1989 lu C: Changes in lip, cheek, and tongue pressures after rapid Küçükkeles¸ N, Ceylanog maxillary expansion using a diaphragm pressure transducer. Angle Orthod 73: 662e668, 2003 Lambrechts H, De Baets, Fieuws S, Williems G: Lip tongue pressure in orthodontic patients. Eur J Orthod 32: 466e471, 2010 Mitchell JI, Williamson FH: A comparison of maximum perioral muscle forces in North American blacks and whites. Angle Orthod 48: 126e131, 1978 Nagamine T, Kobayashi T, Nakajima T, Hanada K: The effects of surgical-orthodontic correction of skeletal class III malocclusion on mandibular movement. J Oral Maxillofac Surg 51: 385e389, 1993
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Noro A, Hosokawa S, Takahashi J, Akihiro Y, Nishimoto Y, Hosokawa I, et al: Basic and clinical subjects of myofunctional therapy using a new oral rehabilitation apparatus. Jpn J Conserv Dent 45: 817e828, 2002 Ohkura K, Harada K, Morishima S, Enomoto S: Change in bite force and occlusal contact area after orthognathic surgery for correction of mandibular prognathism. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 91: 141e145, 2001 Posen AL: The influence of maximum perioral and tongue force on the incisor teeth. Angle Orthod 42: 285e309, 1972 Posen AL: The application of quantitative perioral assessment to orthodontic case analysis and treatment planning. Angle Orthod 46: 118e143, 1976 Proffit WR: Equilibrium theory revisited: factors influencing position of the teeth. Angle Orthod 48: 175e186, 1978 Proffit WR: Muscle pressures and tooth position: North American whites and Australian aborigines. Angle Orthod 45: 1e11, 1975 Proffit WR, Sarver DM, Ackerman JL: Orthodontic diagnosis: the development of a problem list. In: Proffit WR, Fields HW, Sarver DM (eds), Contemporary orthodontics, 4th edn. Philadelphia, PA: Mosby Elsevier, 181e185, 2007 Ruan WH, Chen MD, Gu ZY, Lu Y, Su JM, Guo Q: Muscular forces exerted on the normal deciduous dentition. Angle Orthod 75: 785e790, 2005 Ruan WH, Su JM, Ye XW: Pressure from the lips and the tongue in children with class III malocclusion. J Zhejiang Univ Sci 8: 296e301, 2007 Standring S: Gray’s anatomy, 39th edn. Oxford: Elsevier, 2005 Thüer U, Ingervall B: Pressure from the lips on the teeth and malocclusion. Am J Orthod 90: 234e242, 1986 Tomes CS: The bearing of the development of the jaws on irregularities. Dental Cosmos 15: 292e296, 1973 Ueki K, Marukawa K, Shimada M, Nakagawa K, Yamamoto E, Niizawa S: Changes in the chewing path of patients in skeletal class III with and without asymmetry before and after orthognathic surgery. J Oral Maxillofac Surg 63: 442e448, 2005 Ueki K, Marukawa K, Shimada M, Nakagawa K, Yamamoto: Changes in occlusal force after mandibular ramus osteotomy with and without Le Fort I osteotomy. Int J Oral Surg 36: 301e304, 2007 Ueki K, Mukozawa A, Okabe K, Miyazaki M, Moroi A, Marukawa K, et al: Changes in lip closing force of patients with Class III malocclusion before and after orthognathic surgery. Int J Oral Maxillofac Surg 41: 835e838, 2012a Ueki K, Marukawa K, Hashiba Y, Nakagawa K, Degerliyurt K, Yamamoto E: Changes in the duration of the chewing cycle in patients with skeletal class III with and without asymmetry before and after orthognathic surgery. J Oral Maxillofac Surg 67: 67e72, 2009 Ueki K, Okabe K, Marukawa K, Mukozawa A, Moroi A, Miyazaki M, et al: Effect of self-setting a-tricalcium phosphate between segments for bone healing and hypoaesthesia in lower lip after sagittal split ramus osteotomy. J Craniomaxillofac Surg 40: e119ee124, 2012b Ueki K, Okabe K, Marukawa K, Mukozawa A, Moroi A, Miyazaki M, et al: Assessment of bone healing and hypoesthesia in the upper lip after Le Fort I osteotomy with self-setting a-tricalcium phosphate and absorbable plates. J Craniomaxillofac Surg 41: 129e134, 2013 Ueki K, Moroi A, Sotobori M, Ishihara Y, Marukawa K, Yoshizawa K, et al: Changes in temporomandibular joint and ramus after sagittal split ramus osteotomy in mandibular prognathism patients with and without asymmetry. J Craniomaxillofac Surg 40: 821e827, 2012c
Please cite this article in press as: Ueki K, et al., The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.01.007
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The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery Koichiro Ueki*, Kohei Marukawa, Akinori Moroi, Megumi Sotobori, Yuri Ishihara, Ran Iguchi, Akihiko Kohsaka, Yoshio Nakano, Masatoshi Higuchi, Ryuichi Nakazawa, Hiroumi Ikawa Department of Oral and Maxillofacial Surgery (Head: Prof. Dr. K. Ueki), Division of Medicine, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 1110 Shimokato, Chuo-shi, Yamanashi 409-3898, Japan
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 15 May 2013 Accepted 3 January 2014
Objectives: The purpose of this study was to examine the changes with time in lip pressure after orthognathic surgery for skeletal Class III patients. Study design: The subjects consisted of 63 patients (32 female and 31 male) diagnosed with mandibular prognathism who underwent sagittal split ramus osteotomy with and without Le Fort I osteotomy. Maximum and minimum lip closing forces were measured with Lip De CumÒ. The changes with time were compared statistically. Results: The maximum and minimum lip closing force increased time-dependently in men and women after surgery and there were significant differences between men and women with changes with time in the maximum lip closing force (p ¼ 0.0086) and the minimum lip closing force (p ¼ 0.0302). After 1 year, the Class III group maximum lip closing force was significantly smaller than the control group in both men (p < 0.0001) and women (p < 0.0001). Conclusions: This study suggests that there was significant difference in over time in the lip closing force between men and women in Class III patients. Although the maximum lip closing force increased with time, it did not reach the level of the control group after 1 year. Ó 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Lip closing force Mandibular prognathism Orthognathic surgery
1. Introduction Lip-closing function can be achieved by various types and various amounts of lip-closing movements, depending on the physiological behaviour required. Lip closing movements are not simple tasks like eye blinking, but complex and well-organized tasks that are performed by the orbicularis oris muscle, with additional facial muscles that have muscle fibres in various directions, around the orifice of the mouth. The orbicularis oris muscle is a sphincter muscle composed of two parts in the upper and lower lips (Standring, 2005). Most dental professionals accept the theory of Tomes (Tomes, 1973), who asserted that opposing forces or pressure from the lips and cheeks on one side and the tongue on the other, determine the position of the teeth (Mitchell and Williamson, 1978; Posen 1976).
* Corresponding author. Tel./fax: þ81 55 273 6761. E-mail addresses: [email protected], [email protected] (K. Ueki).
In some patients with maxillary protrusion or severe Class II Division 1 malocclusion, lip incompetency and muscle imbalance are seen (Gould and Piston, 1962; Posen, 1972, 1976). Posen (1976) found that subjects with bimaxillary protrusion have low lip strength, compared with Class I and Class II Division 2 patients, using a device for measuring the strength of the lips. Ruan et al. (2007) reported that patients aged 4e6 years with Class III malocclusion had lower perioral forces and this muscle hypofunction might be secondary to the spatial relation of the jaws. There are some studies regarding morphological changes following orthognathic surgery (Ueki et al., 2012b,c; Ueki et al., 2013). Orthognathic surgery induces not only morphological but also functional changes. Surgical orthodontic correction of skeletal class III physiology reportedly has favourable effects on the function of the mandible, such as an increased range of maximum motion in the anterior, posterior, and lateral excursions (Nagamine et al., 1993). Several studies have examined the opening and closing movements (Aragon et al., 1985; Boyd et al., 1991) as well as the chewing rhythm and path (Ueki et al., 2005, 2007).
1010-5182/$ e see front matter Ó 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jcms.2014.01.007
Please cite this article in press as: Ueki K, et al., The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.01.007
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There had been no report regarding lip closing force in Class III patients following orthognathic surgery until our previous study, which showed that maximum lip closing force at 6 months postoperative increased more than the preoperative value after orthognathic surgery in Class III patients (Ueki et al., 2012a). It was unclear whether the lip closing force continued to increase 1 year after surgery and whether there was a significant difference in the change between men and women with time. The purpose of this study was to compare the temporal changes in lip pressure after orthognathic surgery between male and female skeletal Class III patients. 2. Patients and methods 2.1. Patients The subjects consisted of 31 men (average age, 25.5 7.7 years) and 32 women (average age, 32.9 12.5 years) with Class III malocclusion. All cases were diagnosed as skeletal class III, including mandibular prognathism and/or maxillary retrognathism on the basis of a lateral cephalogram analysis. All the patients underwent orthognathic surgery. Control groups consisted of 20 women (average age, 29.5 4.9 years) and 20 men (average age, 29.5 3.9 years) with normal occlusion without dento-alveolar deformity. Although this was a retrospective study, informed consent was obtained from the patients and the study was approved by Kanazawa University Hospital. 2.2. Measurement of lip closing force Maximum and minimum lip closing forces were measured with Lip De Cum LDC-110RÒ (Cosmos instruments Co. LTD, Tokyo, Japan) (Fig. 1) for the control groups and subject groups preoperatively and at 6 months and 1 year postoperatively. This device consists of a sensor with a lip adaptor and digital display (Noro et al., 2002). The Lip Closure Strength (force) Indicator (Lip De CumÒ) was set up with a Lip holder (DucklingsÒ) mounted to the sensor, and the subject was instructed to bite the holder between the upper and lower lips. Following this the Lip Closure Strength (force) of the subject was measured while the subject was sitting upright (with the FH plane parallel to the floor plane). The subject was instructed to close the upper and lower lips with utmost strength without allowing the upper and lower teeth to touch. The device contains 4 strain gauges at the sensor and converts the measurement value
Fig. 1. Lip Closure Strength (force) Indicator (Lip De CumÒ) with a Lip holder (DucklingsÒ).
into load value (N). During a measurement lasting for 30 s, the shape of the wave is shown on the display of a personal computer connected to the Lip De CumÒ. In the wave, the largest and smallest values were respectively defined as the maximum and minimum values (Fig. 2).
2.2.1. Cephalogram assessment The cephalograms were entered into a computer and analysed using appropriate computer software (Cephalometric Ato Z, Yasunaga Labo Com, Fukui, Japan). Measurements landmarks were as follows, SNA, SNB, ANB, FMA, IMPA, FMIA, U1 to FH plane, Gonial angle, Ramus inclination (FH), Occlusal plane (FH), Interincisal angle, Mandibular length (Co-Gn), Incisor overjet, Incisor over bite, Convexity, S-A parallel to SN (distance between Sella and A-point parallel to SN plane), S-A perpend SN (distance between Sella and A-point perpendicular to SN plane), S-PNS parallel to SN (distance between Sella and PNS parallel to SN plane), S-PNS perpend to SN (distance between Sella and PNS perpendicular to SN plane), S-ANS parallel to SN(distance between Sella and ANS perpendicular to SN plane), S-ANS perpend to SN (distance between Sella and ANS perpendicular to SN plane). These measurements were used to examine which variants significantly correlated to maximum lip closing force using stepwise regression analysis. One skilled observer performed all digitization so that errors in the cephalometric method were small and acceptable for the purposes of this study. Error analysis by digitization and remeasurement of 10 randomly selected cases generated an average error of less than 0.4 mm for the linear measurements and 0.5 for the angular measurements.
2.2.2. Statistical analysis Data were statistically analysed with. SPSSII (SPSS Japan Inc., Tokyo, Japan). Total changes with time from pre-operation to 1 year after surgery were examined by analysis of variance (ANOVA). Comparisons between men and the women in each time period were performed and adjusted using Bonferroni correction. Stepwise regression analysis was carried out to examine the morphological factors affecting the maximum lip closing force. The differences were considered significant at p < 0.05.
Fig. 2. The recorded wave of the lip closing force for 30 s.
Please cite this article in press as: Ueki K, et al., The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.01.007
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3. Results
3.1. Comparisons between men and women in each period
18 of 31 men with mandibular prognathism underwent Le Fort I osteotomy with bilateral sagittal split ramus osteotomy (SSRO) and 13 underwent bilateral SSRO alone.12 of 32 women with mandibular prognathism underwent Le Fort I osteotomy with bilateral SSRO, 20 underwent bilateral SSRO. The mean setback amount by SSRO with and without Le Fort I osteotomy was 6.4 3.5 mm on the right side and 5.6 3.8 mm on the left side in men, and 5.8 3.5 mm on the right side and 6.1 3.6 mm on the left side in women. There were no significant differences in setback amount between men and women. When the post-operative recording at 6 months and 1 year was performed, the occlusion was normal and stable in all patients. Preoperative maximum and minimum lip closing forces (mean and standard deviation) were 9.4 2.1 and 3.4 1.4 (N) in Class III men group, 7.8 2.7 and 2.9 1.4 (N) in Class III women group, 15.0 1.8 and 6.8 0.9 (N) in control men group, and 12.7 1.1 and 6.2 1.0 (N) in control women group. Maximum and minimum lip closing force (mean and standard deviation) after 6 months were10.4 2.7 and 4.2 1.3 (N) in Class III men group, and 8.6 2.6 and 3.8 1.9 (N) in Class III women group. Maximum and minimum lip closing forces (mean and standard deviation) after 1 year were10.4 2.0 and 6.0 1.4 (N) in Class III men group, and 9.3 2.4 and 4.9 1.3 (N) in Class III women group. In Class III patients, there were significant differences between men and women in the l changes with time in the maximum lip closing force (repeated-measures ANOVA, between subjects F ¼ 7.379; df ¼ 1; p ¼ 0.0086; within subjects, F ¼ 20.046; df ¼ 2; p < 0.0001) and the minimum lip closing force (repeated-measures ANOVA, between subjects F ¼ 4.927; df ¼ 1; p ¼ 0.0302; within subjects, F ¼ 77.793; df ¼ 2; p < 0.0001) (Fig. 3 and Table 1). In the maximum lip closing force in men, the value after 6 months was significantly larger than preoperative value (p ¼ 0.0037) and the value after 1 year was still larger than preoperative value (p ¼ 0.0001). There was no difference between after 6 months and 1 year. In the maximum lip closing force in women, the value after 6 months and after 1 year were significantly larger than preoperative value (p ¼ 0.0273 and p < 0.0001) and the value after 1 year was larger than the value after 6 months (p ¼ 0.0304). In the minimum lip closing force in men, the value after 6 months was significantly larger than preoperative value (p ¼ 0.0004), the value after 1 year was larger than preoperative value (p < 0.0001) and the value after 1 year was larger than preoperative value (p < 0.0001). In the minimum lip closing force in women, the value after 6 months and after 1 year were significantly larger than preoperative value (p ¼ 0.0021 and p < 0.0001) and the value after 1 year was larger than the value after 6 months (p ¼ 0.0006). In summary, the maximum and minimum lip closing force increased with time in both men and women after surgery.
Before surgery, the maximum lip closing force in men was significantly larger than that in women in both the Class III group (p ¼ 0.0330) and control group (p ¼ 0.0097). Before surgery, the Class III group maximum lip closing force was significantly smaller than the control group in both men (p < 0.0001) and women (p < 0.0001). After 6 months, the Class III group maximum lip closing force was significantly smaller in the control group regarding both men (p < 0.0001) and women (p < 0.0001). The maximum lip closing force in men was significantly larger than that in women in the Class III group after 6 months (p ¼ 0.0225). After 1 year, the Class III group maximum lip closing force was significantly smaller than the control group in both men (p < 0.0001) and women (p < 0.0001). There was no significant difference between men and women in the Class III group after 1 year (p ¼ 0.1326). Before surgery, there was no significant difference regarding the minimum lip closing force between men and women in both the Class III and control groups, but the maximum lip closing force in the Class III group was significantly smaller than the control group in both men (p < 0.0001) and women (p < 0.0001). After 6 months, a similar tendency was shown. There was no significant difference in the minimum lip closing force between men and women in the Class III group and the Class III group showed a significantly smaller maximum lip closing force value than the control group in both men (p < 0.0001) and women (p < 0.0001). After 1 year, the minimum lip closing force in men was significantly larger than that in women in the Class III group (p ¼ 0.0147), but there was no significant difference between men in the Class III group and men in the control group, although the minimum lip closing force value for women in the Class III group was still smaller than that of the control group (p ¼ 0.0056) (Fig. 3 and Table 1). Statistical comparison between surgical procedures (SSRO group versus SSRO with Le Fort I osteotomy group) did not show any significant differences. Furthermore, there were no significant differences among the groups regarding the other procedures for lip closing force. Stepwise regression analysis showed the maximum lip closing force could be defined by an equation using only the morphological parameter as follows:
A
3.2. Pre-operation (Maximum lip closing force) ¼ 0.387e0.258 (ANB) þ 0.123 (S-ANS parallel to SN) (N ¼ 63, R ¼ 0.497, adjusted R2 ¼ 0.247, RMS Residual ¼ 2.257, F ¼ 9.832; p ¼ 0.0002).
B
Fig. 3. Result of the lip closing force. A) Maximum lip closing force, B) Minimum lip closing force. Error bars indicate standard deviation.
Please cite this article in press as: Ueki K, et al., The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.01.007
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Table 1 Results of the lip closing force. SD, indicates standard deviation. Pre-operative
Class III Men Class III Women Control Men Control Women
Mean SD Mean SD Mean SD Mean SD
After 6 months
After 1 year
Maximum (N)
Minimum (N)
Maximum (N)
Minimum (N)
Maximum (N)
Minimum (N)
9.4 2.1 7.8 2.7 15.0 1.8 12.7 1.1
3.4 1.4 2.9 1.4 6.8 0.9 6.2 1.0
10.4 2.7 8.6 2.6
4.2 1.3 3.8 1.9
10.4 2.0 9.3 2.4
6.0 1.4 4.9 1.3
3.3. After 1 year (Maximum lip closing force) ¼ 3.253 þ 0.105 (FMIA) þ 0.136 (S-PNS perpend to SN) (N ¼ 63, R ¼ 0.497, adjusted R2 ¼ 0.247, RMS Residual ¼ 2.008, F ¼ 9.829; p ¼ 0.0002). 4. Discussion Orthognathic surgery including orthodontic treatment can improve not only aesthetics but also function. Many studies have been published regarding occlusal force after orthognathic surgery (Harada et al., 2000; Ohkura et al., 2001; Ueki et al., 2009). Despite this there had been no knowledge regarding the lip closing force in skeletal class III patients. Our previous study showed that maximum lip closing force at 6 months postoperative increased more than the preoperative value after orthognathic surgery in Class III patients (Ueki et al., 2012a). However, it was unclear whether the lip closing force continued to increase at the period of 1 year after surgery and whether there was a significant difference in the temporal change between men and women. When the maximum lip closing force was measured and examined, it was necessary to recognize the difference between the sexes, with a higher lip pressure measured in men than in women. Kato et al. (1989) and Posen (1972) also demonstrated the same variation in the force with sex. The same trend was found by Ruan et al. (2005) who measured muscle pressure exerted on the primary normal occlusion and concluded that the primary dentition is in a state of dynamic equilibrium. In this study, there were significant differences between men and women in the changes with time in the maximum lip closing force and the minimum lip closing force. This suggests that increase in the lip closing force after surgery was also different between the sexes. Proffit described the primary and secondary force factors related to tooth position, and he concluded that pressure of the tongue and lips is one of the primary factors, but other factors are also related to equilibrium (Proffit, 1975; Proffit, 1978; Proffit et al., 2007). Thüer and Ingervall (1986) recorded, with a dynamometer, the lip pressure of 84 patients at rest and during chewing and swallowing of crisp bread. They found that a Class II division 2 malocclusion was not due to by a strong upper lip but that the incisor position was responsible for the low lip pressure in such patients. In contrast, the study of the maximum lip pressure during maximum voluntary contraction showed that lip pressure was lowest in children with a Class II division 2 malocclusion. Posen (1972) stated that great lip strength, measured with the pommeter (perioral muscle metre) during maximum voluntary contraction, can be an indication of high lip tonus and thus substantial outer forces are acting on the anterior teeth. The study showed that Class II division 2 subjects had high lip strength, while bimaxillary protrusion subjects had low lip strength, and the pressure in Class II division 1 subjects was lower than in subjects with
Class I occlusion. Lambrechts et al. (2010) found that the maximum lip pressure in Class II division 1 was lower than that in Class I, but there were no significant differences in the other comparisons (Class I, Class II division 1, Class II division 2 and Class III). Ruan et al. (2007) showed that paediatric patients (4e6 years old) with a Class III malocclusion generated lower perioral muscle forces. This may cause less bone apposition in this area, which aggravates the clinical features of Class III malocclusion. They postulated that their results reflected muscle hypofunction secondary to the spatial relationship of the jaw in Class III subjects, namely, retroposition of the maxilla. With regard to the change in lip, cheek and tongue pressures after rapid maxillary expansion (RME) using a diaphragm pressure lu (2003) reported that the transducer, Küçükkeles¸ and Ceylanog cheeks and lips almost adapt to a new position of the dental arches at the end of the third month, whereas tongue adaptation took comparatively longer. In their study, pressure values while patients were in the rest position increased significantly after RME and started decreasing by the end of the first month of retention. At the end of the third month, the values decreased to a level almost equal to their preexpansion values. The diaphragm pressure transducer was, however placed at the central incisor buccally, so that it could not be compared with the lip closing pressure that we performed in this study. It is important to measure the upper and lower lip closing forces separately in order to understand the muscle function in detail. However, the device used in this study could not measure the upper and lower lip closing force separately. Therefore, the data in this study are a measure of the total resultant force. In the previous study, Class III patients had significantly lower maximum lip closing force than those in the control group. This finding was similar to that of the previous study of Ruan et al. (2007). This suggested that the maximum lip closing force of Class III patients is weaker in both adults and children. Postoperative maximum lip closing force was significantly larger than the preoperative value in Class III patients in this study. With regard to the surgical procedure, there was no significant difference between SSRO alone and SSRO with Le Fort I osteotomy. This suggested that change in the maximum lip closing force was not related to the surgical procedure, and the skeletal and occlusal changes per se could increase the maximum lip closing force. However, at 1 year postoperative, the maximum lip closing force in the Class III patients was still smaller than that in the control group. Postoperative training of lip closure may play an important role in the maintenance of skeletal and occlusal stability. Jung et al. (2003) found that the values of lip closing forces were related to the variables of upper incisor angulation, and that in Class II were related to the vertical skeletal pattern, with Y-metre (measurement device of the vertical closing force of the upper lip). ANB and S-ANS parallel to SN were selected as related measurements to maximum lip closing force preoperatively. FMIA and SPNS perpend to SN were selected as related measurements to
Please cite this article in press as: Ueki K, et al., The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.01.007
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maximum lip closing force after 1 year surgery. These findings suggested that the region reflected by lip closing force was different in each skeletal and occlusal pattern. Furthermore, the region related to lip closing force could change after correction in skeletal and occlusal pattern. Further studies using larger sample number will be necessary. 5. Conclusion This study showed that the postoperative maximum lip closing force value increased more than the preoperative value after orthognathic surgery in Class III patients, although the postoperative value was significantly smaller than that of the control group. Ethical approval Not required. Competing interests None declared. References Aragon SB, Van Sickels JE, Dolwick MF, Flanary CM: The effects of orthognathic surgery on mandibular range of motion. J Oral Maxillofac Surg 43: 938e943, 1985 Boyd SB, Karas ND, Sinn DP: Recovery of mandibular mobility following orthognathic surgery. J Oral Maxillofac Surg 49: 924e931, 1991 Gould MS, Piston DC: A method of measuring forces acting on the teeth from the lips, cheeks and tongue. Br Dent J 174: 175e180, 1962 Harada K, Watanabe M, Okura K, Enomoto S: Measure of bite force and occlusal contact area before and after bilateral sagittal split ramus osteotomy of the mandible using a new pressure-sensitive device: a preliminary report. J Oral Maxillofac Surg 58: 370e373, 2000 Jung MH, Yang WS, Nahm DS: Effects of upper lip closing force on craniofacial structures. Am J Orthod Dentofacial Orthop 123: 58e63, 2003 Kato Y, Kuroda T, Togawa T: Perioral force measurement by a radiotelemetry device. Am J Orthod Dentofacial Orthop 95: 410e414, 1989 lu C: Changes in lip, cheek, and tongue pressures after rapid Küçükkeles¸ N, Ceylanog maxillary expansion using a diaphragm pressure transducer. Angle Orthod 73: 662e668, 2003 Lambrechts H, De Baets, Fieuws S, Williems G: Lip tongue pressure in orthodontic patients. Eur J Orthod 32: 466e471, 2010 Mitchell JI, Williamson FH: A comparison of maximum perioral muscle forces in North American blacks and whites. Angle Orthod 48: 126e131, 1978 Nagamine T, Kobayashi T, Nakajima T, Hanada K: The effects of surgical-orthodontic correction of skeletal class III malocclusion on mandibular movement. J Oral Maxillofac Surg 51: 385e389, 1993
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Please cite this article in press as: Ueki K, et al., The time-course change in the lip closing force in Class III malocclusion after orthognathic surgery, Journal of Cranio-Maxillo-Facial Surgery (2014), http://dx.doi.org/10.1016/j.jcms.2014.01.007