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Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium
G Model JPOR 484 No. of Pages 5
journal of prosthodontic research xxx (2018) xxx–xxx
Contents lists available at ScienceDirect
Journal of Prosthodontic Research journal homepage: www.elsevier.com/locate/jpor
Original article
Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium Yuko Wataraia,* , Fumi Mizuhashib , Toshihide Satob , Kaoru Koidea,b a b
Functional Occlusal Treatment, The Nippon Dental University Graduate School of Life Dentistry at Niigata, Niigata, Japan Department of Removable Prosthodontics, The Nippon Dental University School of Life Dentistry at Niigata, Niigata, Japan
A R T I C L E I N F O
A B S T R A C T
Article history: Received 12 January 2018 Received in revised form 21 June 2018 Accepted 26 June 2018 Available online xxx
Purpose: A new method inducing the physiologic rest position of the mandible using the lip contact position with the closed mouth have compared with those obtained using conventional methods of placing the mandible in the physiologic rest position. Methods: The lip contact position with the closed mouth as a method was investigated whether the technique was useful for determining the occlusal vertical dimension. The relationship between the space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth and the areas of the prolabia was also investigated. Results: Median space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth was 1.53 mm, a value intermediate between the value of 2.16 mm in the resting mandibular position obtained by the conventional technique and that of 1.33 mm in the swallowing position. The coefficient of variation of the space in the lip contact position with the closed mouth was significantly lower than those in the resting mandibular position and in the swallowing position. A significant positive correlation was recognized between the space in the lip contact position with the closed mouth and the area of the prolabium of the upper lip. Conclusions: These results clarified that the lip contact position with the closed mouth obtained the excellent reproducibility comparing to the conventional methods. These findings suggested that the area of the prolabium of the upper lip might offer an effective index for individual determination of the correct free-way space. © 2018 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.
Keywords: Occlusal verical dimension Rest position of mandible Freeway space Lip contact position
1. Introduction Determination of interocclusal relationship in the correct mandibular position is important to provide dental treatments that fit stomatognathic system in patients with multiple tooth loss, edentulous jaw, and loss of occlusal dimension. Morphological evidences such as cephalograms [1–3] and facial measurements [4,5] and functional evidences such as rest position of the mandible [6,7] and mandibular position during speech [8,9] have been used in the previous methods for determination of the occlusal vertical dimension. However, these methods have not been evaluated as the standard one. Therefore, combination of several different
* Corresponding author at: Functional Occlusal Treatment, The Nippon Dental University Graduate School of Life Dentistry at Niigata, 1-8, Hamaura-cho, Chuo-ku, Niigata city, Niigata 951-8580, Japan. E-mail address: [email protected] (Y. Watarai).
methods has been employed in some cases [10]. The physiologic rest position of the mandible is widely used in clinical practice as a functional method for determination of occlusal vertical dimension. However, the mandibular position is considered to be affected by various factors such as head and body postures [11,12], and mental state [1,13] as well as masticatory and facial muscles and temporomandibular joints [14]. Therefore, high reproducibility of the mandibular position is considered to be significantly difficult. Several different methods have been available for inducing the mandible to the physiologic rest position using the arbitrary mandibular position at rest, the position after swallowing of saliva and the position during speech [15,16]. Judging from the present situation of the studies in this field, it is strongly required to identify highly reproducible method of placing the mandible in the exactly physiologic rest position. Individual variation is apparently recognized in the amount of free-way space which is important when the occlusal vertical dimension is determined using the physiologic rest position of the mandible. Although there have
https://doi.org/10.1016/j.jpor.2018.06.005 1883-1958/ © 2018 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Y. Watarai, et al., Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium, J Prosthodont Res (2018), https://doi.org/ 10.1016/j.jpor.2018.06.005
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been a report on the relationship between the amount of free-way space and the lip length [17], the amount of free-way space have not been accepted as the index of the physiologic rest position of the mandible. Both highly reproducible method of placing the mandible in the physiologic rest position and appropriate standard for determination of the amount of free-way space are required to enable accurate reproducibility of the occlusal vertical dimension in individuals. A new method inducing the physiologic rest position of the mandible using the lip contact position with the closed mouth have been tried to develop in the present study, and the results of this method have compared with those obtained using conventional methods of placing the mandible in the physiologic rest position. In addition, the space between maxillary and mandibular front teeth and the area of the prolabium in the lip contact position of the closed mouth have also investigated. From these results, it have been discussed whether the lip contact position with the closed mouth is effective for determination of the occlusal vertical dimension. 2. Materials and methods 2.1. Subjects A hundred and five healthy, dentulous individuals (61 men, 44 women; mean age, 22.9 2.4 years) were examined in this study. The research protocol of this study was reviewed and approved by the Ethics Committee of The Nippon Dental University School of Life Dentistry at Niigata (approval number ECNG-H-228), and informed consent was obtained from all subjects prior to enrolment. 2.2. Measurement device A head posture-fixing device that had been modified in our department was used to fix the head posture in a natural head position (Fig. 1A,B). This device consisted of earpieces to fix the horizontal head tilt angle, vertically movable horizontal acrylic plates to fix the anteroposterior head tilt angle, and a scale aligned with the positions of individual subjects’ lips while frontal facial standardized photographs were taken. This scale was used to calibrate measurements of lip area on standardized photographs. The digital calipers (Mini Digital Calipers with 100-mm Hold Function; Shinwa Rules Co., Ltd., Sanjo, Japan) was used to measure the space between the maxillary and mandibular front teeth. 2.3. Measurement conditions Each subject was asked to assume a comfortable sitting position without leaning on the backrest because mandible position varies markedly depending on head and body posture [11,12,18]. Horizontal head posture was fixed by inserting earpieces into each external auditory canal and adjusting them to the same level with each other. Anteroposterior head tilt angle was fixed to the natural head position [18]. Namely, the horizontal acrylic plates were adjusted to be the same level of the anterior reference point located 23.0 mm below the right inner canthus as the right arbitrary condylar point (Beyron’s point) which was the posterior reference point. This point was defined to be 13.0 mm from the center of the tragus trailing edge on the line extending to the external canthus [19]. The subject was instructed to look straight ahead while measurements were made. The space between the maxillary and mandibular front teeth was measured in the natural head position under three different conditions: (1) in the subjectspecific resting mandibular position (RP); (2) in the mandibular position after swallowing saliva (SP); and (3) in the lip contact
Fig. 1. The measurement device. (A) Frontal view. (a) Earpiece. (B) Side view. (b) Horizontal acrylic plate.
position with the closed mouth (LP). Measurements were repeated five times each in random order, and differences with the intercuspal position were calculated to obtain the space between the maxillary and mandibular front teeth under each condition. 2.4. Measurement methods The space between the maxillary and mandibular front teeth was measured using digital calipers. Tapes were applied on the points of subnasal and gnathion, and circles of approximately 0.3 mm in diameter were marked on these tapes. The tips of the calipers were placed in the center of these marks during measurements of the distance between subnasal and gnathion. The distance was accurately measured to the order of 0.01 mm. The space between the maxillary and mandibular front teeth was measured by subtracting the distance between subnasal and gnathion in the intercuspal position from that in each specific mandibular position. The three conditions, in which the space between the maxillary and mandibular front teeth was measured in each subject, were defined as follows. The condition RP (the subject-specific resting mandibular position) was defined as the mandibular position 5 s after the
Please cite this article in press as: Y. Watarai, et al., Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium, J Prosthodont Res (2018), https://doi.org/ 10.1016/j.jpor.2018.06.005
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subject had adopted at rest posture in relaxed. The condition SP (the mandibular position after swallowing saliva) was defined as the stable mandibular position 5 s after the subject had swallowed saliva. The condition LP was defined as the mandibular position when the upper and lower lips were evenly in contact with each other after the mouth of the subject was first opened around 20 mm, then was closed in relaxed. To prevent the effect of the previous measurement on the next, the subject opened the mouth by approximately 20 mm before each measurement. Coefficients of variation were also calculated to compare variations in the space between maxillary and mandibular front teeth under each condition. Areas of the prolabia were measured by frontally facial photographs standardized in the condition LP. These photographs were taken by digital camera (EX-ZR1100; Casio Computer Co., Ltd., Tokyo, Japan) at a distance of 1 m from the earpieces of the head posture-fixing device. Then, areas of the prolabia of the upper and lower lips were measured by image analysis software (ImageJ; National Institutes of Health, Bethesda, MD, USA) to an accuracy of 0.1 mm2 (Fig. 2). The calibration of lip area on standardized photographs of individuals was carried out by the vertical scale attached to the anteroposterior position of the lips. The margins of the prolabia of the upper and lower lips were plotted at 0.5-mm intervals on 15 magnified images, and then the areas of the prolabia were measured with great accuracy. The areas of the prolabia were repeatedly measured three times and the mean
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values were calculated. Finally, the relationship among these results was considered and discussed. 2.5. Method of analysis Bellcurve for Excell statistical software (Social Sourvey Research Information Co., Ltd., Tokyo, Japan) was used for statistical analyses. Friedman’s test was used to investigate the space between maxillary and mandibular front teeth in the conditions RP, SP, and LP and the coefficient of variance, and significant factors were investigated using Scheffé’s method of multiple comparison. Spearman’s correlation coefficient test was used to investigate the association between the space between maxillary and mandibular front teeth in the condition LP and the area of the prolabium of the upper lip, and Pearson’s correlation coefficient to investigate its association with the area of the prolabium of the lower lip. 3. Results 3.1. Space between maxillary and mandibular front teeth in the conditions RP, SP, and LP Fig. 3 shows that the space between maxillary and mandibular front teeth is significantly smaller in the conditions SP (1.33 mm) and LP (1.53 mm) than the value in the condition RP (2.16 mm) (p < 0.01). Fig. 4 shows the coefficients of variation under the three different conditions. The median value was 20.4 % for measurements in the condition RP, 19.5 % for measurements in the condition SP, and 11.5 % for measurements in the condition LP. Values of measurements in the condition LP were significantly lower than those in the conditions RP and SP (p < 0.01). 3.2. Association between areas of prolabia and measurements of the condition LP Fig. 5 shows the relationship of the space between maxillary and mandibular front teeth measured in the condition LP to the area of the prolabium of the upper lip. A significant positive correlation was seen in the area of the prolabium of the upper lip (r = 0.61, p < 0.01), but the space between the maxillary and mandibular front teeth in the conditions LP correlated weakly with the area of the prolabium of the lower lip (r = 0.24, p < 0.05) (Fig. 6).
Fig. 2. Measurement of the area of the prolabium of the upper lip.
Fig. 3. Spaces between upper and lower front teeth measured under the three different conditions, the subject-specific resting mandibular position (RP), the mandibular position after swallowing saliva (SP), and the lip contact position with the closed mouth (LP), **p < 0.01.
Fig. 4. Coefficients of variation under the three different conditions, the subjectspecific resting mandibular position (RP), the mandibular position after swallowing saliva (SP), and the lip contact position with the closed mouth (LP), **p < 0.01.
Please cite this article in press as: Y. Watarai, et al., Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium, J Prosthodont Res (2018), https://doi.org/ 10.1016/j.jpor.2018.06.005
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Fig. 5. Correlation of space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth and area of the prolabium of the upper lip, r = 0.61, p < 0.01.
Fig. 6. Correlation of space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth and area of the prolabium of the lower lip, r = 0.24, p < 0.05.
4. Discussion
be relaxed, have opened the mouth by around 20 mm, and then have closed the mouth relaxedly. The lip contact position with the closed mouth would be an effective method for head and body postures. In the case of attempting to determine the mandibular position immediately before moving apart of the upper and lower lips from each other from the closed position of the mouth, there was a possibility that the upper and lower lips might be extended and by maintaining homeostasis of a vital body based on the function of muscles including the mentalis, depressor labii inferioris, depressor angle oris and so on. At the same time, there was also another possibility that the free-way space might also increase as a result of the physical adhesive force between the upper and lower lips. Therefore, to remove these possibilities, the mandibular position was decided at the time when the upper and lower lips were evenly in contact with each other after the mouth has been closed from the opening position.
4.1. Measurement conditions The rest position of the mandible is adjusted by both active factors reacting to sensory receptors of the masticatory and facial muscles and the temporomandibular joints and passive factors such as the viscoelasticity of the various stomatognathic system and negative intraoral pressure [20], and is also susceptible to the effects of head and body postures as well as psychological influences [1,11–14,18]. The device used in this study was equipped with earpieces to fix the horizontal head tilt angle, and used horizontal acrylic plates to fix the anteroposterior head tilt angle in the natural head position by ensuring that the anterior reference point and posterior reference point were the same level. Each subject was also instructed to look straight ahead. This instruction minimized the effects of head and body postures, and accurate comparison was possible among the three different conditions. Each subject was explained to be relaxed in order to remove psychological influences in the measurement as far as possible. A variety of different methods have been used to measure the subject-specific mandibular position. For example, it is said that the subject-specific mandibular position was the mandibular position a few seconds after a movement such as mouth-opening. In this study, measurements in the condition RP were made 5 s after subjects had been instructed to adopt a resting posture. Some studies have reported that the lips of some subjects were not always touching in the physiologic rest position of the mandible [6], and these subjects were also recognized in the condition RP of our study. Many studies have employed swallowing of saliva to place the mandible in the physiologic rest position. It is said that the maxillary and mandibular teeth were in contact with each other during swallowing of saliva, and that the mouth opened slightly immediately after swallowing of saliva, and subsequently the mandible returned within the range of the resting position. In addition, it is said that a mean of around 3.5 s is required to return to a stable state within a certain range after the mouth-opening followed by dry swallowing movement. Based on these data, we have carried out measurements in the condition SP approximately 5 s after swallowing of saliva in this study. The condition LP has been newly employed as a mandibular position in this study. This position was defined as the mandibular position that the upper and lower lips were evenly and loosely in contact with each other after the subjects have been instructed to
4.2. Measurement methods In this study, the front of the lower surface of the gnathion was employed as the measurement point of gnathion in measuring the distance between subnasal and gnathion. The front of the lower surface of the gnathion [21] is the most closely point between the mandibular bone and reference point on the skin when the mandible was moving from intercuspal position to the physiologic rest position. Image analysis software (ImageJ) was used to measure the areas of the prolabia on facial photographs. For providing highly accurate measurements of the areas of the prolabia, the margins of the prolabia of the upper and lower lips were plotted at 0.5-mm intervals on 15 magnified images. 4.3. Measurement results The median values of the space between the maxillary and mandibular front teeth was 2.16 mm in the condition RP, 1.33 mm in the condition SP, and 1.53 mm in the condition LP in the present study. The median value of the space between the maxillary and mandibular front teeth measured in the condition LP was located between those measured in the resting position of the mandible and the condition SP, which were obtained by conventional techniques of placing the mandible in the physiologic rest position. This result might indicate that the condition LP was useful for inducing the physiologic rest position of the mandible. Miralles et al. [15] reported that the value of the free-way space in healthy
Please cite this article in press as: Y. Watarai, et al., Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium, J Prosthodont Res (2018), https://doi.org/ 10.1016/j.jpor.2018.06.005
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dentulous individuals was 1.82 mm, while the value reported by Campillo et al. [22] was 1.40 mm. These values are very close to the value of 1.53 mm for the space between the maxillary and mandibular front teeth in the condition LP in this study. We measured the space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth of six subjects by three operators and compared the space. As a result, after performing a one-way analysis of variance with the correspondence, there was no significant difference with 5 % of levels of significance. In addition, to investigate the difference by the measurement day, operator measured the space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth of the same six subject ten days later, there was no significant difference between the measurement days. A comparison of the coefficients of variation indicated that the median value was 20.4 % for measurements in the condition RP, 19.5 % for measurements in the condition SP, and 11.5 % for measurements in the condition LP. The coefficient of variation was significantly lower in the condition LP than in the conditions RP and SP. This suggested that the condition LP might provide a highly reproducible resting mandibular position comparing to the occlusal vertical dimension, because variation of the condition LP was apparently less than those of the conditions RP and SP. Although the condition SP is believed to provide a relatively stable mandibular position because of the maxillary and mandibular teeth contact with each other on the swallowing of saliva, the absence of tooth contact of edentulous individuals make it difficult to apply to those as a method of placing the mandible in the physiologic rest position. The condition LP in this study is usable for edentulous individuals, and is also suitable for both dentulous and edentulous individuals as a method of placing of the mandible in the physiologic rest position because of a little variation. A correlation coefficient of 0.61 indicated a significant positive correlation between the space between maxillary and mandibular front teeth in the condition LP and the area of the prolabium of the upper lip. However, the correlation coefficient of 0.24 for the area of the prolabium of the lower lip was very weak. The areas of the prolabia lips being different in an individual. Therefore, we analyzed the areas of the prolabia lips of the subject and investigated the relations between the value of the space between the maxillary and mandibular front teeth and the areas of prolabia lips. We consider the area of the prolabium of the upper lip would be usable for the occlusal vertical dimension determination because positive correlation was accepted (Fig. 5), but the area of the prolabium lower lip was not useful too much because a correlation is weak (Fig. 6). A limitation of the present study, in the clinical, determination of the amount of individual space between the maxillary and mandibular front teeth according to the area of the prolabium of the upper lip after setting the appropriate lip support, and subtraction of the individual space between the maxillary and mandibular front teeth from the distance between subnasal and gnathion under the condition LP may enable to determine the appropriate occlusal vertical dimension that fit stomatognathic system in patients with multiple tooth loss, edentulous jaw, and loss of occlusal dimension as well as dentulous jaw.
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position, had the excellent reproducibility comparing to the conventional methods of placing the mandible in the physiologic rest position. These findings suggested that the area of the prolabium of the upper lip might offer an effective index for individual determination of the correct amount of free-way space. This new method for determination of occlusal vertical dimension by subtracting the free-way space according to the area of the prolabium of the upper lip from the distance between subnasal and gnathion under the lip contact position with the closed mouth might be applied in patients with multiple tooth loss, edentulous jaw, and loss of occlusal dimension. References [1] Atwood DA. A cephalometric study of the clinical rest position of the mandible: part I. The variability of the clinical rest position following the removal of occlusal contacts. J Prosthet Dent 1956;6:504–19. [2] Orthlieb JD, Laurent M, Laplanche O. Cephalometric estimation of vertical dimension of occlusion. J Oral Rehabil 2000;27:802–7. [3] Tavano KT, Seraidarian PI, de Oliveira DD, Jansen WC. Determination of vertical dimension of occlusion in dentate patients by cephalometric analysis—pilot study. Gerodontology 2012;29:e297–305. [4] Willis FM. Esthetics of full denture construction. J Am Dent Assoc 1930;17:636–42. [5] McGee GF. Use of facial measurements in determining vertical dimension. J Am Dent Assoc 1947;35:342–50. [6] Niswonger ME. The rest position of the mandibule and centric relation. J Am Dent Assoc 1934;21:1572–82. [7] Pleasure MA. Correct vertical dimension and freeway space. J Am Dent Assoc 1951;43:160–3. [8] Silverman MM. Determination of vertical dimension by phonetics. J Prosthet Dent 1956;6:465–71. [9] Igi c M, Kruni c N, Aleksov L, Kosti c M, Igi c A, Petrovi c MB, et al. Determination of vertical dimension of occlusion by using the phonetic vowel “O” and “E”. Vojnosanit Pregl 2015;72:123–31. [10] Alhajj MN, Khalifa N, Abduo J, Amran AG, Ismail IA. Determination of occlusal vertical dimension for complete dentures patients: an updated review. J Oral Rehabil 2017;44:896–907. [11] Cohen S. A cephalometric study of rest position in edentulous persons: influence of variations in head position. J Prosthet Dent 1957;7:467–72. [12] Tingey EM, Buschang PH, Throckmorton GS. Mandibular rest position: a reliable position influenced by head support and body posture. Am J Orthod Dentofacial Orthop 2001;120:614–22. [13] Murphy WM. Rest position of the mandible. J Prosthet Dent 1967;17:329–32. [14] Ramfjord SP. The significance of recent reserch on occlusion for the teaching and practice of dentistry. J Prosthet Dent 1966;16:96–105. [15] Miralles R, Dodds C, Palazzi C, Jaramillo C, Quezada V, Ormeño G, et al. Vertical dimension. Part 1: comparison of clinical freeway space. Cranio 2001;19: 230–6. [16] Fresno MJ, Miralles R, Valdivia J, Fuentes A, Valenzuela S, Ravera MJ, et al. Electromyographic evaluation of anterior temporal and suprahyoid muscles using habitual methods to determine clinical rest position. Cranio 2007;25:257–63. [17] Hurst WW. Vertical dimension and its correlation with lip length and interocclusal distance. J Am Dent Assoc 1962;64:496–504. [18] Ishii M, Koide K, Ueki M, Asanuma N. Influence of body and head posture on deviation of the incisal point undergoing dental treatment. Prosthodont Res Pract 2007;6:217–24. [19] O’Malley AM, Milosevic A. Comparison of three facebow/semi-adjustable articulator systems for planning orthognathic surgery. Br J Oral Maxillofac Surg 2000;38:185–90. [20] Faigenblum MJ. Negative oral pressures. A research report. Dent Pract Dent Rec 1966;16:214–6. [21] Alhajj MN, Khalifa N, Amran A. Eye-rima oris distance and its relation to the vertical dimension of occlusion measured by two methods: athropometric study in a sample of Yemeni dental students. Eur J Dent 2016;10:29–33. [22] Campillo B, Martín C, Palma JC, Fuentes AD, Alarcón JA. Electromyographic activity of the jaw muscles and mandibular kinematics in young adults with theoretically ideal dental occlusion: reference values. Med Oral Patol Oral Cir Bucal 2017;22:e383–91.
5. Conclusion These results clarified that the lip contact position with the closed mouth, which placed the mandible in the physiologic rest
Please cite this article in press as: Y. Watarai, et al., Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium, J Prosthodont Res (2018), https://doi.org/ 10.1016/j.jpor.2018.06.005
journal of prosthodontic research xxx (2018) xxx–xxx
Contents lists available at ScienceDirect
Journal of Prosthodontic Research journal homepage: www.elsevier.com/locate/jpor
Original article
Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium Yuko Wataraia,* , Fumi Mizuhashib , Toshihide Satob , Kaoru Koidea,b a b
Functional Occlusal Treatment, The Nippon Dental University Graduate School of Life Dentistry at Niigata, Niigata, Japan Department of Removable Prosthodontics, The Nippon Dental University School of Life Dentistry at Niigata, Niigata, Japan
A R T I C L E I N F O
A B S T R A C T
Article history: Received 12 January 2018 Received in revised form 21 June 2018 Accepted 26 June 2018 Available online xxx
Purpose: A new method inducing the physiologic rest position of the mandible using the lip contact position with the closed mouth have compared with those obtained using conventional methods of placing the mandible in the physiologic rest position. Methods: The lip contact position with the closed mouth as a method was investigated whether the technique was useful for determining the occlusal vertical dimension. The relationship between the space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth and the areas of the prolabia was also investigated. Results: Median space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth was 1.53 mm, a value intermediate between the value of 2.16 mm in the resting mandibular position obtained by the conventional technique and that of 1.33 mm in the swallowing position. The coefficient of variation of the space in the lip contact position with the closed mouth was significantly lower than those in the resting mandibular position and in the swallowing position. A significant positive correlation was recognized between the space in the lip contact position with the closed mouth and the area of the prolabium of the upper lip. Conclusions: These results clarified that the lip contact position with the closed mouth obtained the excellent reproducibility comparing to the conventional methods. These findings suggested that the area of the prolabium of the upper lip might offer an effective index for individual determination of the correct free-way space. © 2018 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.
Keywords: Occlusal verical dimension Rest position of mandible Freeway space Lip contact position
1. Introduction Determination of interocclusal relationship in the correct mandibular position is important to provide dental treatments that fit stomatognathic system in patients with multiple tooth loss, edentulous jaw, and loss of occlusal dimension. Morphological evidences such as cephalograms [1–3] and facial measurements [4,5] and functional evidences such as rest position of the mandible [6,7] and mandibular position during speech [8,9] have been used in the previous methods for determination of the occlusal vertical dimension. However, these methods have not been evaluated as the standard one. Therefore, combination of several different
* Corresponding author at: Functional Occlusal Treatment, The Nippon Dental University Graduate School of Life Dentistry at Niigata, 1-8, Hamaura-cho, Chuo-ku, Niigata city, Niigata 951-8580, Japan. E-mail address: [email protected] (Y. Watarai).
methods has been employed in some cases [10]. The physiologic rest position of the mandible is widely used in clinical practice as a functional method for determination of occlusal vertical dimension. However, the mandibular position is considered to be affected by various factors such as head and body postures [11,12], and mental state [1,13] as well as masticatory and facial muscles and temporomandibular joints [14]. Therefore, high reproducibility of the mandibular position is considered to be significantly difficult. Several different methods have been available for inducing the mandible to the physiologic rest position using the arbitrary mandibular position at rest, the position after swallowing of saliva and the position during speech [15,16]. Judging from the present situation of the studies in this field, it is strongly required to identify highly reproducible method of placing the mandible in the exactly physiologic rest position. Individual variation is apparently recognized in the amount of free-way space which is important when the occlusal vertical dimension is determined using the physiologic rest position of the mandible. Although there have
https://doi.org/10.1016/j.jpor.2018.06.005 1883-1958/ © 2018 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Y. Watarai, et al., Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium, J Prosthodont Res (2018), https://doi.org/ 10.1016/j.jpor.2018.06.005
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been a report on the relationship between the amount of free-way space and the lip length [17], the amount of free-way space have not been accepted as the index of the physiologic rest position of the mandible. Both highly reproducible method of placing the mandible in the physiologic rest position and appropriate standard for determination of the amount of free-way space are required to enable accurate reproducibility of the occlusal vertical dimension in individuals. A new method inducing the physiologic rest position of the mandible using the lip contact position with the closed mouth have been tried to develop in the present study, and the results of this method have compared with those obtained using conventional methods of placing the mandible in the physiologic rest position. In addition, the space between maxillary and mandibular front teeth and the area of the prolabium in the lip contact position of the closed mouth have also investigated. From these results, it have been discussed whether the lip contact position with the closed mouth is effective for determination of the occlusal vertical dimension. 2. Materials and methods 2.1. Subjects A hundred and five healthy, dentulous individuals (61 men, 44 women; mean age, 22.9 2.4 years) were examined in this study. The research protocol of this study was reviewed and approved by the Ethics Committee of The Nippon Dental University School of Life Dentistry at Niigata (approval number ECNG-H-228), and informed consent was obtained from all subjects prior to enrolment. 2.2. Measurement device A head posture-fixing device that had been modified in our department was used to fix the head posture in a natural head position (Fig. 1A,B). This device consisted of earpieces to fix the horizontal head tilt angle, vertically movable horizontal acrylic plates to fix the anteroposterior head tilt angle, and a scale aligned with the positions of individual subjects’ lips while frontal facial standardized photographs were taken. This scale was used to calibrate measurements of lip area on standardized photographs. The digital calipers (Mini Digital Calipers with 100-mm Hold Function; Shinwa Rules Co., Ltd., Sanjo, Japan) was used to measure the space between the maxillary and mandibular front teeth. 2.3. Measurement conditions Each subject was asked to assume a comfortable sitting position without leaning on the backrest because mandible position varies markedly depending on head and body posture [11,12,18]. Horizontal head posture was fixed by inserting earpieces into each external auditory canal and adjusting them to the same level with each other. Anteroposterior head tilt angle was fixed to the natural head position [18]. Namely, the horizontal acrylic plates were adjusted to be the same level of the anterior reference point located 23.0 mm below the right inner canthus as the right arbitrary condylar point (Beyron’s point) which was the posterior reference point. This point was defined to be 13.0 mm from the center of the tragus trailing edge on the line extending to the external canthus [19]. The subject was instructed to look straight ahead while measurements were made. The space between the maxillary and mandibular front teeth was measured in the natural head position under three different conditions: (1) in the subjectspecific resting mandibular position (RP); (2) in the mandibular position after swallowing saliva (SP); and (3) in the lip contact
Fig. 1. The measurement device. (A) Frontal view. (a) Earpiece. (B) Side view. (b) Horizontal acrylic plate.
position with the closed mouth (LP). Measurements were repeated five times each in random order, and differences with the intercuspal position were calculated to obtain the space between the maxillary and mandibular front teeth under each condition. 2.4. Measurement methods The space between the maxillary and mandibular front teeth was measured using digital calipers. Tapes were applied on the points of subnasal and gnathion, and circles of approximately 0.3 mm in diameter were marked on these tapes. The tips of the calipers were placed in the center of these marks during measurements of the distance between subnasal and gnathion. The distance was accurately measured to the order of 0.01 mm. The space between the maxillary and mandibular front teeth was measured by subtracting the distance between subnasal and gnathion in the intercuspal position from that in each specific mandibular position. The three conditions, in which the space between the maxillary and mandibular front teeth was measured in each subject, were defined as follows. The condition RP (the subject-specific resting mandibular position) was defined as the mandibular position 5 s after the
Please cite this article in press as: Y. Watarai, et al., Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium, J Prosthodont Res (2018), https://doi.org/ 10.1016/j.jpor.2018.06.005
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subject had adopted at rest posture in relaxed. The condition SP (the mandibular position after swallowing saliva) was defined as the stable mandibular position 5 s after the subject had swallowed saliva. The condition LP was defined as the mandibular position when the upper and lower lips were evenly in contact with each other after the mouth of the subject was first opened around 20 mm, then was closed in relaxed. To prevent the effect of the previous measurement on the next, the subject opened the mouth by approximately 20 mm before each measurement. Coefficients of variation were also calculated to compare variations in the space between maxillary and mandibular front teeth under each condition. Areas of the prolabia were measured by frontally facial photographs standardized in the condition LP. These photographs were taken by digital camera (EX-ZR1100; Casio Computer Co., Ltd., Tokyo, Japan) at a distance of 1 m from the earpieces of the head posture-fixing device. Then, areas of the prolabia of the upper and lower lips were measured by image analysis software (ImageJ; National Institutes of Health, Bethesda, MD, USA) to an accuracy of 0.1 mm2 (Fig. 2). The calibration of lip area on standardized photographs of individuals was carried out by the vertical scale attached to the anteroposterior position of the lips. The margins of the prolabia of the upper and lower lips were plotted at 0.5-mm intervals on 15 magnified images, and then the areas of the prolabia were measured with great accuracy. The areas of the prolabia were repeatedly measured three times and the mean
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values were calculated. Finally, the relationship among these results was considered and discussed. 2.5. Method of analysis Bellcurve for Excell statistical software (Social Sourvey Research Information Co., Ltd., Tokyo, Japan) was used for statistical analyses. Friedman’s test was used to investigate the space between maxillary and mandibular front teeth in the conditions RP, SP, and LP and the coefficient of variance, and significant factors were investigated using Scheffé’s method of multiple comparison. Spearman’s correlation coefficient test was used to investigate the association between the space between maxillary and mandibular front teeth in the condition LP and the area of the prolabium of the upper lip, and Pearson’s correlation coefficient to investigate its association with the area of the prolabium of the lower lip. 3. Results 3.1. Space between maxillary and mandibular front teeth in the conditions RP, SP, and LP Fig. 3 shows that the space between maxillary and mandibular front teeth is significantly smaller in the conditions SP (1.33 mm) and LP (1.53 mm) than the value in the condition RP (2.16 mm) (p < 0.01). Fig. 4 shows the coefficients of variation under the three different conditions. The median value was 20.4 % for measurements in the condition RP, 19.5 % for measurements in the condition SP, and 11.5 % for measurements in the condition LP. Values of measurements in the condition LP were significantly lower than those in the conditions RP and SP (p < 0.01). 3.2. Association between areas of prolabia and measurements of the condition LP Fig. 5 shows the relationship of the space between maxillary and mandibular front teeth measured in the condition LP to the area of the prolabium of the upper lip. A significant positive correlation was seen in the area of the prolabium of the upper lip (r = 0.61, p < 0.01), but the space between the maxillary and mandibular front teeth in the conditions LP correlated weakly with the area of the prolabium of the lower lip (r = 0.24, p < 0.05) (Fig. 6).
Fig. 2. Measurement of the area of the prolabium of the upper lip.
Fig. 3. Spaces between upper and lower front teeth measured under the three different conditions, the subject-specific resting mandibular position (RP), the mandibular position after swallowing saliva (SP), and the lip contact position with the closed mouth (LP), **p < 0.01.
Fig. 4. Coefficients of variation under the three different conditions, the subjectspecific resting mandibular position (RP), the mandibular position after swallowing saliva (SP), and the lip contact position with the closed mouth (LP), **p < 0.01.
Please cite this article in press as: Y. Watarai, et al., Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium, J Prosthodont Res (2018), https://doi.org/ 10.1016/j.jpor.2018.06.005
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Fig. 5. Correlation of space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth and area of the prolabium of the upper lip, r = 0.61, p < 0.01.
Fig. 6. Correlation of space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth and area of the prolabium of the lower lip, r = 0.24, p < 0.05.
4. Discussion
be relaxed, have opened the mouth by around 20 mm, and then have closed the mouth relaxedly. The lip contact position with the closed mouth would be an effective method for head and body postures. In the case of attempting to determine the mandibular position immediately before moving apart of the upper and lower lips from each other from the closed position of the mouth, there was a possibility that the upper and lower lips might be extended and by maintaining homeostasis of a vital body based on the function of muscles including the mentalis, depressor labii inferioris, depressor angle oris and so on. At the same time, there was also another possibility that the free-way space might also increase as a result of the physical adhesive force between the upper and lower lips. Therefore, to remove these possibilities, the mandibular position was decided at the time when the upper and lower lips were evenly in contact with each other after the mouth has been closed from the opening position.
4.1. Measurement conditions The rest position of the mandible is adjusted by both active factors reacting to sensory receptors of the masticatory and facial muscles and the temporomandibular joints and passive factors such as the viscoelasticity of the various stomatognathic system and negative intraoral pressure [20], and is also susceptible to the effects of head and body postures as well as psychological influences [1,11–14,18]. The device used in this study was equipped with earpieces to fix the horizontal head tilt angle, and used horizontal acrylic plates to fix the anteroposterior head tilt angle in the natural head position by ensuring that the anterior reference point and posterior reference point were the same level. Each subject was also instructed to look straight ahead. This instruction minimized the effects of head and body postures, and accurate comparison was possible among the three different conditions. Each subject was explained to be relaxed in order to remove psychological influences in the measurement as far as possible. A variety of different methods have been used to measure the subject-specific mandibular position. For example, it is said that the subject-specific mandibular position was the mandibular position a few seconds after a movement such as mouth-opening. In this study, measurements in the condition RP were made 5 s after subjects had been instructed to adopt a resting posture. Some studies have reported that the lips of some subjects were not always touching in the physiologic rest position of the mandible [6], and these subjects were also recognized in the condition RP of our study. Many studies have employed swallowing of saliva to place the mandible in the physiologic rest position. It is said that the maxillary and mandibular teeth were in contact with each other during swallowing of saliva, and that the mouth opened slightly immediately after swallowing of saliva, and subsequently the mandible returned within the range of the resting position. In addition, it is said that a mean of around 3.5 s is required to return to a stable state within a certain range after the mouth-opening followed by dry swallowing movement. Based on these data, we have carried out measurements in the condition SP approximately 5 s after swallowing of saliva in this study. The condition LP has been newly employed as a mandibular position in this study. This position was defined as the mandibular position that the upper and lower lips were evenly and loosely in contact with each other after the subjects have been instructed to
4.2. Measurement methods In this study, the front of the lower surface of the gnathion was employed as the measurement point of gnathion in measuring the distance between subnasal and gnathion. The front of the lower surface of the gnathion [21] is the most closely point between the mandibular bone and reference point on the skin when the mandible was moving from intercuspal position to the physiologic rest position. Image analysis software (ImageJ) was used to measure the areas of the prolabia on facial photographs. For providing highly accurate measurements of the areas of the prolabia, the margins of the prolabia of the upper and lower lips were plotted at 0.5-mm intervals on 15 magnified images. 4.3. Measurement results The median values of the space between the maxillary and mandibular front teeth was 2.16 mm in the condition RP, 1.33 mm in the condition SP, and 1.53 mm in the condition LP in the present study. The median value of the space between the maxillary and mandibular front teeth measured in the condition LP was located between those measured in the resting position of the mandible and the condition SP, which were obtained by conventional techniques of placing the mandible in the physiologic rest position. This result might indicate that the condition LP was useful for inducing the physiologic rest position of the mandible. Miralles et al. [15] reported that the value of the free-way space in healthy
Please cite this article in press as: Y. Watarai, et al., Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium, J Prosthodont Res (2018), https://doi.org/ 10.1016/j.jpor.2018.06.005
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dentulous individuals was 1.82 mm, while the value reported by Campillo et al. [22] was 1.40 mm. These values are very close to the value of 1.53 mm for the space between the maxillary and mandibular front teeth in the condition LP in this study. We measured the space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth of six subjects by three operators and compared the space. As a result, after performing a one-way analysis of variance with the correspondence, there was no significant difference with 5 % of levels of significance. In addition, to investigate the difference by the measurement day, operator measured the space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth of the same six subject ten days later, there was no significant difference between the measurement days. A comparison of the coefficients of variation indicated that the median value was 20.4 % for measurements in the condition RP, 19.5 % for measurements in the condition SP, and 11.5 % for measurements in the condition LP. The coefficient of variation was significantly lower in the condition LP than in the conditions RP and SP. This suggested that the condition LP might provide a highly reproducible resting mandibular position comparing to the occlusal vertical dimension, because variation of the condition LP was apparently less than those of the conditions RP and SP. Although the condition SP is believed to provide a relatively stable mandibular position because of the maxillary and mandibular teeth contact with each other on the swallowing of saliva, the absence of tooth contact of edentulous individuals make it difficult to apply to those as a method of placing the mandible in the physiologic rest position. The condition LP in this study is usable for edentulous individuals, and is also suitable for both dentulous and edentulous individuals as a method of placing of the mandible in the physiologic rest position because of a little variation. A correlation coefficient of 0.61 indicated a significant positive correlation between the space between maxillary and mandibular front teeth in the condition LP and the area of the prolabium of the upper lip. However, the correlation coefficient of 0.24 for the area of the prolabium of the lower lip was very weak. The areas of the prolabia lips being different in an individual. Therefore, we analyzed the areas of the prolabia lips of the subject and investigated the relations between the value of the space between the maxillary and mandibular front teeth and the areas of prolabia lips. We consider the area of the prolabium of the upper lip would be usable for the occlusal vertical dimension determination because positive correlation was accepted (Fig. 5), but the area of the prolabium lower lip was not useful too much because a correlation is weak (Fig. 6). A limitation of the present study, in the clinical, determination of the amount of individual space between the maxillary and mandibular front teeth according to the area of the prolabium of the upper lip after setting the appropriate lip support, and subtraction of the individual space between the maxillary and mandibular front teeth from the distance between subnasal and gnathion under the condition LP may enable to determine the appropriate occlusal vertical dimension that fit stomatognathic system in patients with multiple tooth loss, edentulous jaw, and loss of occlusal dimension as well as dentulous jaw.
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position, had the excellent reproducibility comparing to the conventional methods of placing the mandible in the physiologic rest position. These findings suggested that the area of the prolabium of the upper lip might offer an effective index for individual determination of the correct amount of free-way space. This new method for determination of occlusal vertical dimension by subtracting the free-way space according to the area of the prolabium of the upper lip from the distance between subnasal and gnathion under the lip contact position with the closed mouth might be applied in patients with multiple tooth loss, edentulous jaw, and loss of occlusal dimension. References [1] Atwood DA. A cephalometric study of the clinical rest position of the mandible: part I. The variability of the clinical rest position following the removal of occlusal contacts. J Prosthet Dent 1956;6:504–19. [2] Orthlieb JD, Laurent M, Laplanche O. Cephalometric estimation of vertical dimension of occlusion. J Oral Rehabil 2000;27:802–7. [3] Tavano KT, Seraidarian PI, de Oliveira DD, Jansen WC. Determination of vertical dimension of occlusion in dentate patients by cephalometric analysis—pilot study. Gerodontology 2012;29:e297–305. [4] Willis FM. Esthetics of full denture construction. J Am Dent Assoc 1930;17:636–42. [5] McGee GF. Use of facial measurements in determining vertical dimension. J Am Dent Assoc 1947;35:342–50. [6] Niswonger ME. The rest position of the mandibule and centric relation. J Am Dent Assoc 1934;21:1572–82. [7] Pleasure MA. Correct vertical dimension and freeway space. J Am Dent Assoc 1951;43:160–3. [8] Silverman MM. Determination of vertical dimension by phonetics. J Prosthet Dent 1956;6:465–71. [9] Igi c M, Kruni c N, Aleksov L, Kosti c M, Igi c A, Petrovi c MB, et al. Determination of vertical dimension of occlusion by using the phonetic vowel “O” and “E”. Vojnosanit Pregl 2015;72:123–31. [10] Alhajj MN, Khalifa N, Abduo J, Amran AG, Ismail IA. Determination of occlusal vertical dimension for complete dentures patients: an updated review. J Oral Rehabil 2017;44:896–907. [11] Cohen S. A cephalometric study of rest position in edentulous persons: influence of variations in head position. J Prosthet Dent 1957;7:467–72. [12] Tingey EM, Buschang PH, Throckmorton GS. Mandibular rest position: a reliable position influenced by head support and body posture. Am J Orthod Dentofacial Orthop 2001;120:614–22. [13] Murphy WM. Rest position of the mandible. J Prosthet Dent 1967;17:329–32. [14] Ramfjord SP. The significance of recent reserch on occlusion for the teaching and practice of dentistry. J Prosthet Dent 1966;16:96–105. [15] Miralles R, Dodds C, Palazzi C, Jaramillo C, Quezada V, Ormeño G, et al. Vertical dimension. Part 1: comparison of clinical freeway space. Cranio 2001;19: 230–6. [16] Fresno MJ, Miralles R, Valdivia J, Fuentes A, Valenzuela S, Ravera MJ, et al. Electromyographic evaluation of anterior temporal and suprahyoid muscles using habitual methods to determine clinical rest position. Cranio 2007;25:257–63. [17] Hurst WW. Vertical dimension and its correlation with lip length and interocclusal distance. J Am Dent Assoc 1962;64:496–504. [18] Ishii M, Koide K, Ueki M, Asanuma N. Influence of body and head posture on deviation of the incisal point undergoing dental treatment. Prosthodont Res Pract 2007;6:217–24. [19] O’Malley AM, Milosevic A. Comparison of three facebow/semi-adjustable articulator systems for planning orthognathic surgery. Br J Oral Maxillofac Surg 2000;38:185–90. [20] Faigenblum MJ. Negative oral pressures. A research report. Dent Pract Dent Rec 1966;16:214–6. [21] Alhajj MN, Khalifa N, Amran A. Eye-rima oris distance and its relation to the vertical dimension of occlusion measured by two methods: athropometric study in a sample of Yemeni dental students. Eur J Dent 2016;10:29–33. [22] Campillo B, Martín C, Palma JC, Fuentes AD, Alarcón JA. Electromyographic activity of the jaw muscles and mandibular kinematics in young adults with theoretically ideal dental occlusion: reference values. Med Oral Patol Oral Cir Bucal 2017;22:e383–91.
5. Conclusion These results clarified that the lip contact position with the closed mouth, which placed the mandible in the physiologic rest
Please cite this article in press as: Y. Watarai, et al., Highly producible method for determination of occlusal vertical dimension: relationship between measurement of lip contact position with the closed mouth and area of upper prolabium, J Prosthodont Res (2018), https://doi.org/ 10.1016/j.jpor.2018.06.005