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Influence of oral appliances on craniocervical posture in obstructive sleep apnea–hypopnea syndrome patients
Available online at www.sciencedirect.com
Journal of Prosthodontic Research 53 (2009) 107–110 www.elsevier.com/locate/jpor
Original article
Influence of oral appliances on craniocervical posture in obstructive sleep apnea–hypopnea syndrome patients Yoshimi Inoko DDS, PhD*, Osami Morita DDS, PhD Department of Complete Denture, the Nippon Dental University School of Life Dentistry at Niigata, 1-8 Hamaura-cho, Chuo-ku, Niigata 951-8580, Japan Received 12 June 2008; accepted 26 November 2008 Available online 31 March 2009
Abstract Purpose: The existence of a relationship between head posture and mandibular function has been discussed by several authors. However, the relationship between head posture and the cervical spine in patients with obstructive sleep apnea–hypopnea syndrome (OSAHS) who are using oral appliances (OAs) remains unknown. The aim of this study was to evaluate the changes in the cervical spine associated with the use of OAs in patients with OSAHS. Methods: Fifteen patients (4 females and 11 males; mean age, 48 years) diagnosed with OSAHS were randomly selected. An OA was fabricated individually for each patient. Two lateral cephalometric radiographs were taken while the patient was sitting awake in an upright position. The first radiograph was taken in the intercuspal position and the second was taken while the subject was wearing the OA. Analyses based on the sella– nasion (SN) line were performed in the lateral cephalogram. Comparison of craniocervical angles in patients with and without the OA was performed using Wilcoxon’s signed-rank test. Results: Cephalometric analysis showed that the craniocervical angles (CVT-C2V and SN-C4) with OA were higher than those without OA (P < 0.05). It seems that the OA caused a significant flexion of the cranium on the upper cervical spine. A significant increase in the craniocervical angle occurred in the fourth cervical segment. Conclusion: The changes in forward flexion of the upper cervical spine found in this study imply that changes in the craniocervical relationship should be evaluated periodically after an OA has been inserted. # 2009 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved. Keywords: Craniocervical posture; Cervical spine; Oral appliance; Lateral cephalogram; Obstructive sleep apnea–hypopnea syndrome
1. Introduction Several authors have discussed an inter-relationship between the different constituents of the craniocervical–mandibular system [1–8]. The dental literature reports the influence of head and body posture on the mandibular rest position [5], the range of functional mandibular movements [6], and the use of removable oral appliances (OAs) [7,8]. Rocabado et al. [9] described a relationship between head posture and dental occlusion. Although some researchers have found that an increase in the occlusal vertical dimension is associated with significant changes in the craniocervical relationship [7,8], others have indicated that there were no significant changes in the
* Corresponding author. Tel.: +81 25 267 1500; fax: +81 25 267 8906. E-mail address: [email protected] (Y. Inoko).
craniocervical relationship when there was a temporary increase in the occlusal dimension [10,11]. In addition, Muto et al. [12] reported the relationship between the pharyngeal airway space and craniocervical angulations. Various types of dental OAs are used by dental practitioners for the treatment of patients. OAs are frequently used in orthodontics and for the treatment of nocturnal bruxism, temporomandibular disorders and, more recently, sleep apnea or snoring. OA therapies for snoring or obstructive sleep apnea (OSA) have a direct influence on mandibular position and thereby an increase in airway size [13–15] is expected. They provide an increase in the occlusal vertical dimension and anterior shift in the mandible. Moya et al. [16] showed that insertion of an occlusal splint led to significant changes in the craniocervical relationship. Therefore, we consider that there is a strong relationship between the mandibular posture, cervical spine angle, and pharyngeal space. However, the relationship
1883-1958/$ – see front matter # 2009 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved. doi:10.1016/j.jpor.2009.02.001
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Y. Inoko, O. Morita / Journal of Prosthodontic Research 53 (2009) 107–110
Table 1 Clinical characteristics of the subjects. Variable
Range (mean)
Age (years) Gender (male/female) Body mass index (kg/m2) Apnea–hypopnea index (no./h) CT90a (%)
20–70 (48.1) 11/4 16.0–29.4 (23.7) 0.9–25.5 (15.2) 0.0–18.8 (3.4)
a
A cumulative percentage of time spent at saturations below 90%.
between head posture and the cervical spine in patients with obstructive sleep apnea–hypopnea syndrome (OSAHS) who are using OAs remains unknown. The aim of the study was to evaluate the changes in the cervical spine associated with the use of OAs in patients with OSAHS. 2. Materials and methods 2.1. Subjects Fifteen subjects (4 females and 11 males) with OSAHS participated in this study (Table 1). The patients were referred to the Nippon Dental University, Niigata Hospital, because of symptoms consistent with snoring. The diagnosis of obstructive sleep apnea–hypopnea was based on polysomnographic findings. The study was performed with the approval of the Ethics Committee of the Nippon Dental University School of Life Dentistry at Niigata (#42), and informed consent was obtained from all patients. 2.2. Appliance description After each patient had undergone a baseline medical, dental, and stomatognathic examination, an OA was fabricated individually for each patient using the method of Harada et al. [15]. After checking the retentiveness of the maxillary and mandibular splints, the degree of protrusion of the OA was adjusted for individual patients. The splints were attached to each other with a self-curing resin in the patient’s mouth. The OA was then polished and completed (Fig. 1). The patients were instructed to use the OA only during sleep and were informed of the possible side-effects, such as transient tooth, temporomandibular joint or masticatory muscle discomfort, which may occur the following morning after initial use. If the patient had marked discomfort at the temporomandibular joint or masticatory muscle, it was possible to separate and rejoin the OA to decrease the degree of protrusion. Such adjustments were repeated until the discomfort disappeared.
Fig. 1. Image of an oral appliance used in this study.
parallel to the floor. For the first radiograph, the patient was instructed to make light contact in the intercuspal position; for the second, the OA was fitted intraorally. No instructions regarding tongue position were given to the patient. Lateral skull radiographs were taken with a cephalometric radiograph unit (CX-150SK; Asahi Roentgen Ind. Co. Ltd.) using a standard technique. The distance from the focus to the median plane was 1.5 m, and the enlargement was 10%, which was not corrected in the cephalometric analysis. Analysis of the lateral cephalogram was based on the sella– nasion (SN) line. The angles measured were SN-CVT (cervical vertebrae tangent), SN-C2V [line through cv2tg (the superior– posterior point of the second CV) and cv2ip (the inferior– posterior point of the second CV)], CVT-C2V, SN-C2 (tangent to the inferior edge of the second CV), SN-C3 (edge of the third CV), and SN-C4 (edge of the fourth CV) (Fig. 2). All analyses were performed by a single researcher. 2.4. Statistical analysis Six angles (SN-CVT, SN-C2V, CVT-C2V, SN-C2, SN-C3, and SN-C4) with and without the OA were compared using Wilcoxon’s signed rank test. P < 0.05 was selected as being statistically significant. 3. Results The results are shown in Table 2. Cephalometric analysis showed that the craniocervical angles (CVT-C2V and SN-C4) with OA were higher than those without OA. There was a significant increase in cervical forward flexion in the fourth cervical segment (P < 0.05). We observed that the fourth cervical segment inclined forward. It seems that the OA caused a significant flexion of the cranium on the upper cervical spine.
2.3. Cephalometric evaluation 4. Discussion Two lateral craniocervical radiographs were taken for each patient. They were obtained with the patient sitting awake in an upright position with the Frankfort horizontal plane
The aim of using OAs is to widen the oropharyngeal airway by repositioning the mandible advancement during
Y. Inoko, O. Morita / Journal of Prosthodontic Research 53 (2009) 107–110
109
Fig. 2. Reference points and lines. (1) Reference points. S, sella point; N, nasion point; cv2tg, target point of the superior–posterior extremity of the odontoid process of the second cervical vertebra; cv2ip, most infero-posterior point on the body of the second cervical vertebra; cv4ip, most infero-posterior point on the body of the fourth cervical vertebra. (2) Reference lines. SN, sella–nasion line (line through S and N); CVT, upper part of the cervical spine (line through cv2tg and cv4ip); C2V, tangent line through cv2tg and cv2ip; C2, tangent line to the inferior edge of the second cervical vertebra; C3, tangent line to the inferior edge of the third cervical vertebra; C4, tangent line to the inferior edge of the fourth cervical vertebra. Table 2 Median values of the craniocervical variables in 15 subjects.
SN-CVT SN-C2V CVT-C2V SN-C2 SN-C3 SN-C4
Without OA (degree)
With OA (degree)
P value
106.0 (89.0–123.0) 103.0 (94.0–117.0) 3.5 ( 4.0 to 7.0) 24.0 (17.0–39.0) 23.5 (11.0–46.0) 22.0 (13.0–42.0)
107.0 (92.0–121.0) 103.5 (86.0–118.0) 4.0 ( 3.0 to 8.0) 28.0 (16.0–42.0) 28.0 (16.0–42.0) 25.0 (17.0–35.0)
0.48 0.27 0.04 0.18 0.23 0.03
sleep. The American Academy of Sleep Medicine [17] has issued practice guidelines stating that OA therapy is indicated for simple snoring and mild OSAHS, and for moderate to severe OSAHS if nasal continuous positive airway pressure (NCPAP) is not acceptable or if surgery is inappropriate. Although NCPAP has been considered superior to the use of an OA, it is poorly tolerated and less often used. Therefore, OAs are important in the treatment of OSAHS and may be the preferred initial treatment. The use of OAs is an increasingly popular alternative to more established therapies [18]. However, excessive mandibular protrusion may have detrimental consequences in the long term, especially for dental occlusion and the temporomandibular joint, and requires further investigation. In the present study, we used cephalometric analysis to investigate the changes in the cervical spine associated with the use of an OA in OSAHS patients. We found that a significant increase in cervical forward flexion occurred in the fourth cervical segment immediately after the OA had
been inserted in the oral cavity. The fourth cervical segment showed a forward inclination. This result verifies the hypothesis that an increase in the occlusal dimension and mandibular protrusion distance caused by an OA is associated with the flexion of the head on the neck. This means that the head holder in the natural head position may interfere with, or correct, any posture changes that may have occurred in association with a change in the mandibular position when an OA is used. Few studies have reported the influence of the head and the use of removable OAs [7,8]. Urbanowicz [7] and Miralles et al. [8] found that an increase in the occlusal vertical dimension leads to significant changes in the craniocervical relationship. Using cephalometric analysis, Moya et al. [16] reported that a full-arch maxillary stabilization occlusal splint caused a significant extension of the head on the cervical spine in subjects with muscle spasms in the sternocleidomastoid and trapezius muscles. There was also a significant decrease in the cervical spine lordosis in the first, second, and third cervical segments. These results disagree with those of the present study, in which a significant increase in cervical forward flexion occurred in the fourth cervical segment. These differences are considered to be caused by mandible protrusion as a result of wearing the OA. 5. Conclusion The changes in forward flexion of the upper cervical spine found in this study imply that it is necessary to evaluate
110
Y. Inoko, O. Morita / Journal of Prosthodontic Research 53 (2009) 107–110
periodically the changes occurring in the craniocervical relationship after an OA has been inserted. References [1] Body CH. The effect of head position on EMG evaluations of representative mandibular positioning muscle groups. J Craniomandib Pract 1987;5:51–3. [2] Daly P, Preston CB, Evans WG. Postural response of the head to bite opening in adult males. Am J Orthod 1982;82:157–60. [3] Miralles R, Zunino P, Santander H, Manns A. Influence of occlusal splints on bilateral anterior temporal EMG activity during swallowing of saliva in patients with craniomandibular dysfunction. J Craniomandib Pract 1991;9:129–36. [4] Tripodakis AP, Smulow JB, Mehta NR, Clark RE. Clinical study of location and reproducibility of three mandibular positions in relation to body posture and muscle function. J Prosthet Dent 1995;73: 190–8. [5] Hairston LE, Blanton PL. An electromyographic study of mandibular position in response to changes in body position. J Prosthet Dent 1983;49:271–5. [6] Zafar H, Nordh E, Eriksson P-O. Temporal coordination between mandibular and head–neck movement during jaw opening–closing tasks in man. Arch Oral Biol 2000;45:675–82. [7] Urbanowicz M. Alteration of vertical dimension and its effect on head and neck posture. J Craniomandib Pract 1991;9:1174–9. [8] Miralles R, Moya H, Ravera MJ, Santander H, Zuniga C, Carvajal R, et al. Increase of the vertical occlusal dimension by means of a removable orthodontic appliance and its effect on craniocervical relationship and
[9] [10] [11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
position of the cervical spine in children. J Craniomandib Pract 1997; 15:221–8. Rocabado M, Johnston BE, Blakney MG. Physical therapy and dentistry: an overview. J Craniomandib Pract 1982;1:46–9. Root GR, Kraus SL, Razook SJ, Samson GS. Effects of intraoral splint on head and neck posture. J Prosthet Dent 1987;58:90–5. Huggare J, Raustia A. Head posture and cervicovertebral and craniofacial morphology in patients with craniomandibular dysfunction. J Craniomandib Pract 1992;10:173–7. Muto T, Takeda S, Kanazawa M, Yamazaki A, Fujiwara Y, Mizoguchi I. The effect of head posture on the pharyngeal airway space (PAS). Int J Oral Maxillofac Surg 2002;31:579–83. Nakazawa Y, Sakamoto T, Yasutake R, Yamaga K, Kotorii T, Miyahara Y, et al. Treatment of sleep apnea with prosthetic mandibular advancement (PMA). Sleep 1992;15:499–504. Yoshida K. Effects of a mandibular advancement device for the treatment of sleep apnea syndrome and snoring on respiratory function and sleep quality. J Craniomandib Pract 2000;18:98–105. Harada M, Inoko Y, Shimizu K, Morita O. The effectiveness of prosthodontics mandibular advancement for obstructive sleep apnea syndrome. J Jpn Prosthodont Soc 2004;48:733–40 [in Japanese with English abst]. Moya H, Miralles R, Zun˜iga C. Influence of stabilization occlusal splint on craniocervical relationship. Part 1: Cephalometric analysis. J Craniomandib Pract 1994;12:47–51. American Academy of Sleep Medicine. Sleep related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research. Sleep 1999;22:667–89. Standard of Practice Committee of the American Sleep Disorders Association. Practice parameter for the treatment of snoring and obstructive sleep apnea with oral appliance. Sleep 1995;18:511–3.
Journal of Prosthodontic Research 53 (2009) 107–110 www.elsevier.com/locate/jpor
Original article
Influence of oral appliances on craniocervical posture in obstructive sleep apnea–hypopnea syndrome patients Yoshimi Inoko DDS, PhD*, Osami Morita DDS, PhD Department of Complete Denture, the Nippon Dental University School of Life Dentistry at Niigata, 1-8 Hamaura-cho, Chuo-ku, Niigata 951-8580, Japan Received 12 June 2008; accepted 26 November 2008 Available online 31 March 2009
Abstract Purpose: The existence of a relationship between head posture and mandibular function has been discussed by several authors. However, the relationship between head posture and the cervical spine in patients with obstructive sleep apnea–hypopnea syndrome (OSAHS) who are using oral appliances (OAs) remains unknown. The aim of this study was to evaluate the changes in the cervical spine associated with the use of OAs in patients with OSAHS. Methods: Fifteen patients (4 females and 11 males; mean age, 48 years) diagnosed with OSAHS were randomly selected. An OA was fabricated individually for each patient. Two lateral cephalometric radiographs were taken while the patient was sitting awake in an upright position. The first radiograph was taken in the intercuspal position and the second was taken while the subject was wearing the OA. Analyses based on the sella– nasion (SN) line were performed in the lateral cephalogram. Comparison of craniocervical angles in patients with and without the OA was performed using Wilcoxon’s signed-rank test. Results: Cephalometric analysis showed that the craniocervical angles (CVT-C2V and SN-C4) with OA were higher than those without OA (P < 0.05). It seems that the OA caused a significant flexion of the cranium on the upper cervical spine. A significant increase in the craniocervical angle occurred in the fourth cervical segment. Conclusion: The changes in forward flexion of the upper cervical spine found in this study imply that changes in the craniocervical relationship should be evaluated periodically after an OA has been inserted. # 2009 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved. Keywords: Craniocervical posture; Cervical spine; Oral appliance; Lateral cephalogram; Obstructive sleep apnea–hypopnea syndrome
1. Introduction Several authors have discussed an inter-relationship between the different constituents of the craniocervical–mandibular system [1–8]. The dental literature reports the influence of head and body posture on the mandibular rest position [5], the range of functional mandibular movements [6], and the use of removable oral appliances (OAs) [7,8]. Rocabado et al. [9] described a relationship between head posture and dental occlusion. Although some researchers have found that an increase in the occlusal vertical dimension is associated with significant changes in the craniocervical relationship [7,8], others have indicated that there were no significant changes in the
* Corresponding author. Tel.: +81 25 267 1500; fax: +81 25 267 8906. E-mail address: [email protected] (Y. Inoko).
craniocervical relationship when there was a temporary increase in the occlusal dimension [10,11]. In addition, Muto et al. [12] reported the relationship between the pharyngeal airway space and craniocervical angulations. Various types of dental OAs are used by dental practitioners for the treatment of patients. OAs are frequently used in orthodontics and for the treatment of nocturnal bruxism, temporomandibular disorders and, more recently, sleep apnea or snoring. OA therapies for snoring or obstructive sleep apnea (OSA) have a direct influence on mandibular position and thereby an increase in airway size [13–15] is expected. They provide an increase in the occlusal vertical dimension and anterior shift in the mandible. Moya et al. [16] showed that insertion of an occlusal splint led to significant changes in the craniocervical relationship. Therefore, we consider that there is a strong relationship between the mandibular posture, cervical spine angle, and pharyngeal space. However, the relationship
1883-1958/$ – see front matter # 2009 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved. doi:10.1016/j.jpor.2009.02.001
108
Y. Inoko, O. Morita / Journal of Prosthodontic Research 53 (2009) 107–110
Table 1 Clinical characteristics of the subjects. Variable
Range (mean)
Age (years) Gender (male/female) Body mass index (kg/m2) Apnea–hypopnea index (no./h) CT90a (%)
20–70 (48.1) 11/4 16.0–29.4 (23.7) 0.9–25.5 (15.2) 0.0–18.8 (3.4)
a
A cumulative percentage of time spent at saturations below 90%.
between head posture and the cervical spine in patients with obstructive sleep apnea–hypopnea syndrome (OSAHS) who are using OAs remains unknown. The aim of the study was to evaluate the changes in the cervical spine associated with the use of OAs in patients with OSAHS. 2. Materials and methods 2.1. Subjects Fifteen subjects (4 females and 11 males) with OSAHS participated in this study (Table 1). The patients were referred to the Nippon Dental University, Niigata Hospital, because of symptoms consistent with snoring. The diagnosis of obstructive sleep apnea–hypopnea was based on polysomnographic findings. The study was performed with the approval of the Ethics Committee of the Nippon Dental University School of Life Dentistry at Niigata (#42), and informed consent was obtained from all patients. 2.2. Appliance description After each patient had undergone a baseline medical, dental, and stomatognathic examination, an OA was fabricated individually for each patient using the method of Harada et al. [15]. After checking the retentiveness of the maxillary and mandibular splints, the degree of protrusion of the OA was adjusted for individual patients. The splints were attached to each other with a self-curing resin in the patient’s mouth. The OA was then polished and completed (Fig. 1). The patients were instructed to use the OA only during sleep and were informed of the possible side-effects, such as transient tooth, temporomandibular joint or masticatory muscle discomfort, which may occur the following morning after initial use. If the patient had marked discomfort at the temporomandibular joint or masticatory muscle, it was possible to separate and rejoin the OA to decrease the degree of protrusion. Such adjustments were repeated until the discomfort disappeared.
Fig. 1. Image of an oral appliance used in this study.
parallel to the floor. For the first radiograph, the patient was instructed to make light contact in the intercuspal position; for the second, the OA was fitted intraorally. No instructions regarding tongue position were given to the patient. Lateral skull radiographs were taken with a cephalometric radiograph unit (CX-150SK; Asahi Roentgen Ind. Co. Ltd.) using a standard technique. The distance from the focus to the median plane was 1.5 m, and the enlargement was 10%, which was not corrected in the cephalometric analysis. Analysis of the lateral cephalogram was based on the sella– nasion (SN) line. The angles measured were SN-CVT (cervical vertebrae tangent), SN-C2V [line through cv2tg (the superior– posterior point of the second CV) and cv2ip (the inferior– posterior point of the second CV)], CVT-C2V, SN-C2 (tangent to the inferior edge of the second CV), SN-C3 (edge of the third CV), and SN-C4 (edge of the fourth CV) (Fig. 2). All analyses were performed by a single researcher. 2.4. Statistical analysis Six angles (SN-CVT, SN-C2V, CVT-C2V, SN-C2, SN-C3, and SN-C4) with and without the OA were compared using Wilcoxon’s signed rank test. P < 0.05 was selected as being statistically significant. 3. Results The results are shown in Table 2. Cephalometric analysis showed that the craniocervical angles (CVT-C2V and SN-C4) with OA were higher than those without OA. There was a significant increase in cervical forward flexion in the fourth cervical segment (P < 0.05). We observed that the fourth cervical segment inclined forward. It seems that the OA caused a significant flexion of the cranium on the upper cervical spine.
2.3. Cephalometric evaluation 4. Discussion Two lateral craniocervical radiographs were taken for each patient. They were obtained with the patient sitting awake in an upright position with the Frankfort horizontal plane
The aim of using OAs is to widen the oropharyngeal airway by repositioning the mandible advancement during
Y. Inoko, O. Morita / Journal of Prosthodontic Research 53 (2009) 107–110
109
Fig. 2. Reference points and lines. (1) Reference points. S, sella point; N, nasion point; cv2tg, target point of the superior–posterior extremity of the odontoid process of the second cervical vertebra; cv2ip, most infero-posterior point on the body of the second cervical vertebra; cv4ip, most infero-posterior point on the body of the fourth cervical vertebra. (2) Reference lines. SN, sella–nasion line (line through S and N); CVT, upper part of the cervical spine (line through cv2tg and cv4ip); C2V, tangent line through cv2tg and cv2ip; C2, tangent line to the inferior edge of the second cervical vertebra; C3, tangent line to the inferior edge of the third cervical vertebra; C4, tangent line to the inferior edge of the fourth cervical vertebra. Table 2 Median values of the craniocervical variables in 15 subjects.
SN-CVT SN-C2V CVT-C2V SN-C2 SN-C3 SN-C4
Without OA (degree)
With OA (degree)
P value
106.0 (89.0–123.0) 103.0 (94.0–117.0) 3.5 ( 4.0 to 7.0) 24.0 (17.0–39.0) 23.5 (11.0–46.0) 22.0 (13.0–42.0)
107.0 (92.0–121.0) 103.5 (86.0–118.0) 4.0 ( 3.0 to 8.0) 28.0 (16.0–42.0) 28.0 (16.0–42.0) 25.0 (17.0–35.0)
0.48 0.27 0.04 0.18 0.23 0.03
sleep. The American Academy of Sleep Medicine [17] has issued practice guidelines stating that OA therapy is indicated for simple snoring and mild OSAHS, and for moderate to severe OSAHS if nasal continuous positive airway pressure (NCPAP) is not acceptable or if surgery is inappropriate. Although NCPAP has been considered superior to the use of an OA, it is poorly tolerated and less often used. Therefore, OAs are important in the treatment of OSAHS and may be the preferred initial treatment. The use of OAs is an increasingly popular alternative to more established therapies [18]. However, excessive mandibular protrusion may have detrimental consequences in the long term, especially for dental occlusion and the temporomandibular joint, and requires further investigation. In the present study, we used cephalometric analysis to investigate the changes in the cervical spine associated with the use of an OA in OSAHS patients. We found that a significant increase in cervical forward flexion occurred in the fourth cervical segment immediately after the OA had
been inserted in the oral cavity. The fourth cervical segment showed a forward inclination. This result verifies the hypothesis that an increase in the occlusal dimension and mandibular protrusion distance caused by an OA is associated with the flexion of the head on the neck. This means that the head holder in the natural head position may interfere with, or correct, any posture changes that may have occurred in association with a change in the mandibular position when an OA is used. Few studies have reported the influence of the head and the use of removable OAs [7,8]. Urbanowicz [7] and Miralles et al. [8] found that an increase in the occlusal vertical dimension leads to significant changes in the craniocervical relationship. Using cephalometric analysis, Moya et al. [16] reported that a full-arch maxillary stabilization occlusal splint caused a significant extension of the head on the cervical spine in subjects with muscle spasms in the sternocleidomastoid and trapezius muscles. There was also a significant decrease in the cervical spine lordosis in the first, second, and third cervical segments. These results disagree with those of the present study, in which a significant increase in cervical forward flexion occurred in the fourth cervical segment. These differences are considered to be caused by mandible protrusion as a result of wearing the OA. 5. Conclusion The changes in forward flexion of the upper cervical spine found in this study imply that it is necessary to evaluate
110
Y. Inoko, O. Morita / Journal of Prosthodontic Research 53 (2009) 107–110
periodically the changes occurring in the craniocervical relationship after an OA has been inserted. References [1] Body CH. The effect of head position on EMG evaluations of representative mandibular positioning muscle groups. J Craniomandib Pract 1987;5:51–3. [2] Daly P, Preston CB, Evans WG. Postural response of the head to bite opening in adult males. Am J Orthod 1982;82:157–60. [3] Miralles R, Zunino P, Santander H, Manns A. Influence of occlusal splints on bilateral anterior temporal EMG activity during swallowing of saliva in patients with craniomandibular dysfunction. J Craniomandib Pract 1991;9:129–36. [4] Tripodakis AP, Smulow JB, Mehta NR, Clark RE. Clinical study of location and reproducibility of three mandibular positions in relation to body posture and muscle function. J Prosthet Dent 1995;73: 190–8. [5] Hairston LE, Blanton PL. An electromyographic study of mandibular position in response to changes in body position. J Prosthet Dent 1983;49:271–5. [6] Zafar H, Nordh E, Eriksson P-O. Temporal coordination between mandibular and head–neck movement during jaw opening–closing tasks in man. Arch Oral Biol 2000;45:675–82. [7] Urbanowicz M. Alteration of vertical dimension and its effect on head and neck posture. J Craniomandib Pract 1991;9:1174–9. [8] Miralles R, Moya H, Ravera MJ, Santander H, Zuniga C, Carvajal R, et al. Increase of the vertical occlusal dimension by means of a removable orthodontic appliance and its effect on craniocervical relationship and
[9] [10] [11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
position of the cervical spine in children. J Craniomandib Pract 1997; 15:221–8. Rocabado M, Johnston BE, Blakney MG. Physical therapy and dentistry: an overview. J Craniomandib Pract 1982;1:46–9. Root GR, Kraus SL, Razook SJ, Samson GS. Effects of intraoral splint on head and neck posture. J Prosthet Dent 1987;58:90–5. Huggare J, Raustia A. Head posture and cervicovertebral and craniofacial morphology in patients with craniomandibular dysfunction. J Craniomandib Pract 1992;10:173–7. Muto T, Takeda S, Kanazawa M, Yamazaki A, Fujiwara Y, Mizoguchi I. The effect of head posture on the pharyngeal airway space (PAS). Int J Oral Maxillofac Surg 2002;31:579–83. Nakazawa Y, Sakamoto T, Yasutake R, Yamaga K, Kotorii T, Miyahara Y, et al. Treatment of sleep apnea with prosthetic mandibular advancement (PMA). Sleep 1992;15:499–504. Yoshida K. Effects of a mandibular advancement device for the treatment of sleep apnea syndrome and snoring on respiratory function and sleep quality. J Craniomandib Pract 2000;18:98–105. Harada M, Inoko Y, Shimizu K, Morita O. The effectiveness of prosthodontics mandibular advancement for obstructive sleep apnea syndrome. J Jpn Prosthodont Soc 2004;48:733–40 [in Japanese with English abst]. Moya H, Miralles R, Zun˜iga C. Influence of stabilization occlusal splint on craniocervical relationship. Part 1: Cephalometric analysis. J Craniomandib Pract 1994;12:47–51. American Academy of Sleep Medicine. Sleep related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research. Sleep 1999;22:667–89. Standard of Practice Committee of the American Sleep Disorders Association. Practice parameter for the treatment of snoring and obstructive sleep apnea with oral appliance. Sleep 1995;18:511–3.