ORIGINAL ARTICLE
Follow-up study of dental and skeletal changes in patients with obstructive sleep apnea and hypopnea syndrome with long-term treatment with the Silensor appliance Xiaoyu Wang,a Xu Gong,b Zhe Yu,c Xuemei Gao,d and Ying Zhaoe Beijing, China
Introduction: In this study, we aimed to investigate the dental and skeletal changes associated with long-term use of the Silensor appliance (Erkodent, Cologne, Germany) in patients with obstructive sleep apnea and hypopnea syndrome. Methods: The sample included 42 patients with mild-to-severe obstructive sleep apnea and hypopnea syndrome (mean apnea-hypopnea index, 27; range, 5-74) who had been treated with the Silensor appliance for an average of 4 years (range, 1-11 years). A questionnaire was used to assess of the side effects subjectively; the cephalometric analysis was conducted to identify the dental and skeletal changes of different treatment times objectively. Results: The Silensor appliance was associated with few subjective side effects. Most subjective side effects decreased after long-term use of the Silensor appliance. Significant changes after long-term use of the Silensor appliance were observed in incisor angulation, overbite, overjet, mandibular plane angle, anterior lower facial height, and anterior facial height. Overbite and skeletal changes at treatment times between 1 year and 3 years were a decrease in overbite and increases in the mandibular plane angle, anterior lower facial height, and anterior facial height. Overjet and other dental changes at treatment times longer than 3 years were a decrease in overjet, retroclination of the maxillary incisors, and proclination of the mandibular incisors. Conclusions: The Silensor appliance was well tolerated and preferred by most subjects. Common but mild dental and skeletal changes resulted from using the appliance over a long period of time. The changes after 1 to 3 years of use were skeletal changes predominantly. Both dental and skeletal changes were observed simultaneously at treatment times longer than 3 years. (Am J Orthod Dentofacial Orthop 2015;147:559-65)
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bstructive sleep apnea and hypopnea syndrome (OSAHS) is a sleep-related breathing disorder characterized by repeated narrowing or collapse of the upper airway during sleep, resulting in hypoxemia, arousal, and fragmentation of sleep.1,2 Since the first a Resident, Department of Dentistry, Xuanwu Hospital, Capital Medical University, Beijing, China. b Lecturer, Department of Orthodontics, School and Hospital of Stomatology, Peking University, Beijing, China. c Lecturer, Department of Dentistry, Xuanwu Hospital, Capital Medical University, Beijing, China. d Professor, Department of Orthodontics, School and Hospital of Stomatology, Peking University, Beijing, China. e Professor, Department of Dentistry, Xuanwu Hospital, Capital Medical University, Beijing, China. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: Ying Zhao ,No. 45 Changchun St, Xicheng District, Beijing, China 100053; e-mail, [email protected]. Submitted, February 2014; revised and accepted, January 2015. 0889-5406/$36.00 Copyright Ó 2015 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2015.01.013
description of the disease, many treatment methods have been attempted, including weight loss, medication, surgery, and continuous positive airway pressure (CPAP).3 Mandibular advancement devices (MADs) have also been reported to be an effective treatment option for patients with OSAHS.4-6 Therapy with MADs is increasingly popular not only because of its good efficacy, but also because of its simplicity, high acceptance, noninvasiveness, and low cost.7 According to the American Academy of Sleep Medicine, MADs are indicated in patients with primary snoring and upper airway resistance syndrome, patients with mild-to-moderate OSAHS who prefer MADs to CPAP, and those with severe OSAHS who refuse CPAP.8 Many MADs that vary in design are in use, but it is now recognized that the anterior repositioning of the mandible is an essential mechanism of the MAD by which the oropharyngeal space is increased.9,10 The Silensor appliance (Erkodent, Cologne, Germany) is a type of custom-made semirigid MAD with a satisfying efficacy11-14 and a low 559
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frequency of subjective side effects.11,14 Furthermore, a recent study suggested that the Silensor appliance is suitable for the first phase of oral appliance treatment for OSAHS.14 Dental and skeletal changes associated with longterm use of MADs have been studied with cephalometric analysis. Most authors evaluated the side effects induced by MAD use for an average of 2 to 3 years. In addition, in most studies, only patients with mild-to-moderate OSAHS or snorers were included.15-17 Among various authors, Almeida et al18 reported changes after at least 5 years of oral appliance use. However, the oral appliances in that study were rigid MADs and held the mandible in a fixed forward and slight downward position. MAD design is thought to be one factor that could affect the side effects from use of the appliance.19 Compared with rigid MADs, the Silensor appliance has an adjustable advancement of the mandible with mouth opening. Any further opening of the mouth increases the anterior displacement of the mandible. Therefore, a better understanding of the possible side effects after longterm treatment with semirigid MADs is meaningful. The aim of this study was to investigate the possible dental and skeletal changes associated with long-term use (4 years on average) of the Silensor appliance in patients with mild-to-severe OSAHS. MATERIAL AND METHODS
In this study, 56 subjects who fulfilled the following inclusion criteria were initially selected: (1) diagnosed with OSAHS based on polysomnography examination and suitable for Silensor appliance treatment (with mandibular retrognathia, a downward positioned hyoid bone, or a narrow oropharyngeal airway); (2) no mental or psychological illness; (3) enough teeth to retain the appliance without periodontitis; (4) no active temporomandibular dysfunction; (5) answered the pretreatment questionnaire and had cephalometric radiography; and (6) signed written informed consent. The follow-up polysomnography was completed after 4 weeks for the final adjustment of the Silensor appliance to evaluate the efficiency. Then 4 subjects who did not meet the success criteria based on the polysomnography examination (a decrease in the apnea-hypopnea index to \5 for mild OSAHS patients and a reduction in the apneahypopnea index by 50% for moderate and severe OSAHS patients20) were excluded. During this study, we recalled them for regular clinical reviews at 1-year intervals. At the end of this study, we recalled the subjects for questionnaires and follow-up cephalometric radiographs. The exclusion criteria included (1) not wearing the Silensor appliance for more than 5 hours per night and 5 days
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Table I. Clinical characteristics of the 42 subjects Parameter Sex Age (y) Apnea-hypopnea index Treatment time (y)
Value 31 men (74%), 11 women (26%) 47 6 10 (range, 26-70) 27 6 19 (range, 5-74) 4 6 3 (range, 1-11) \3 (22 subjects) $3 (20 subjects)
Fig 1. Design of the Silensor appliance.
per week for at least 1 year (5 subjects), (2) had CPAP therapy or surgical treatment during the study (2 subjects), (3) had tooth extractions or periodontal surgery during the study (1 subject), or (4) lost to follow-up (2 subjects). Overall, 42 subjects were included in this study. Their clinical characteristics are shown in Table I. All patients received treatment at the Department of Dentistry, Xuanwu Hospital, Capital Medical University, and the Department of Orthodontics, Peking University School and Hospital of Stomatology, in China. This study was approved by the institutional review board of Xuanwu Hospital, Capital Medical University. The Silensor appliance is a type of custom-made semirigid MAD, composed of soft methyl methacrylate and 2 separate splints connected by bars with 4 different lengths. Most teeth in both arches are covered by the splints, except for the third molars. The design of the Silensor appliance is shown in Figure 1. The Silensor appliance induced mandibular advancements of 65% to 75% of maximum protrusion and 4.5 to 5 mm of vertical displacements. The adjustment was performed during the first 2 to 4 weeks of treatment. Then a questionnaire was completed as the baseline after 4 weeks for the final adjustment of the Silensor appliance. The questionnaire included several yes or no questions that addressed the side effects. At the end of this study, we recalled the patients with long-term use of Silensor appliance, and the same questionnaire was repeated to evaluate the longterm subjective side effects.
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Table II. Questionnaire evaluations at baseline and follow-up Subjective side effects* Excessive salivation Dry mouth Dental discomfort Occlusal change Loosening of tooth Tongue discomfort Gingival discomfort Maxillofacial discomfort
Baseline 15 (36%) 7 (17%) 18 (43%) 0 (0%) 0 (0%) 0 (0%) 0 (0%) 15 (36%)
Follow-up 9 (21%) 4 (10%) 7 (17%) 1 (2%) 0 (0%) 0 (0%) 0 (0%) 2 (5%)
*Subjects were asked to mark “yes” when the side effect occurred subjectively.
Fig 2. Cephalometric analysis: landmarks, reference lines, angles, and distances. Points: S, sella; N, nasion; ANS, anterior nasal spine; A, innermost point on the anterior contour of the maxilla; B, innermost point on the contour of the mandible; Me, menton; Go, gonion; P, porion; Or, orbitale. Planes: SN, anterior cranial base; FH, Frankfort horizontal plane (P-Or); MP, mandibular plane (Me-Go); U1, maxillary incisor axis (connects incisor edge to root apex); L1, mandibular incisor axis (connects incisor edge to root apex). Dental: U1-SN angle, maxillary incisor angle related to SN; U1NA angle, maxillary incisor angle related to NA; U1-NA distance, maxillary incisal edge to NA; L1-MP angle, mandibular incisor angle related to MP; L1-NB angle, mandibular incisor angle related to NB; L1-NB distance, mandibular incisal edge to NB; U1-L1 angle, interincisal angle; OB, overbite, vertical overlap between the edges of the maxillary and mandibular incisors; OJ, overjet, horizontal distance between the maxillary incisal edge and the labial surface of the most prominent mandibular incisor. Skeletal: SNA angle, anteroposterior position of the maxilla; SNB angle, anteroposterior position of mandible; ANB angle, magnitude of the skeletal jaw discrepancy; MP-FH angle, mandibular plane angle; ALFH, anterior lower facial height (ANS-Me); AFH, anterior facial height (N-Me); PFH, posterior facial height (S-Go).
Standardized lateral cephalometric radiographs were routinely obtained at pretreatment as the baseline. At the end of this study, we recalled the patients not only for the questionnaire, but also for the follow-up lateral cephalometric radiograph (without the Silensor appliance). The baseline and the follow-up lateral cephalometric radiographs were measured and compared to evaluate dental and skeletal changes in the patients who received treatment with the Silensor appliance. The patients were asked to bite in intercuspation, breathe slowly, and not swallow during the radiograph
procedure. The cephalometric analysis was based on the methods of the Steiner21 and Wylie,22 using the professional cephalometric analysis software Dental Studio NX (version 6.0; Nemotec, La Plaine de Saint-Denis, France). The landmarks, reference lines, angles, and distances used in the cephalometric analysis are shown in Figure 2. To improve accuracy, all distances and angles were measured twice, on 2 separate occasions 2 weeks apart, by a blinded operator (X.W.). The method errorP was assessed P using Dahlberg's formula23: ME2 5 d2/2n, 2 where d is the sum of the squared differences between pairs of recordings, and n is the number of double measurements. The method error in the linear measurements fell within the range of 0.18 to 0.40 mm, and the angular measurements fell within 0.23 to 0.41 . The mean values were used for statistical analysis. Statistical analysis
The data are presented as the mean values and standard deviations. Dental and skeletal characteristics between the baseline and follow-up were compared using the Student paired t test (version 11.5) with a significance level of 0.05. Further analysis of the data was then undertaken by comparing each treatment time (\3 years and $3 years) between the baseline and follow-up. RESULTS
All 42 patients completed the questionnaire and underwent a clinical examination. The Silensor appliance was associated with a low rate of side effects. Most subjective side effects were decreased after long-term use of the Silensor appliance. Only 1 patient reported an occlusal change at the follow-up, but positive overjet and overbite and multiple occlusal contacts were maintained. The questionnaire data at baseline and at followup are shown in Table II.
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Table III. Dental changes after long-term use of the Silensor appliance Baseline 100.51 6 6.37 20.16 6 5.69 4.75 6 2.64 99.16 6 7.26 30.78 6 6.24 8.84 6 2.96 122.37 6 9.38 3.28 6 1.40 4.32 6 1.73
U1-SN angle ( ) U1-NA angle ( ) U1-NA distance (mm) L1-MP angle ( ) L1-NB angle ( ) L1-NB distance (mm) U1-L1 angle ( ) Overbite (mm) Overjet (mm)
Follow-up without Silensor appliance 99.02 6 6.86 18.75 6 6.28 4.07 6 2.68 100.10 6 7.24 31.80 6 6.29 8.91 6 2.93 122.57 6 9.20 2.27 6 1.46 3.29 6 1.75
Difference 1.49 6 1.55 1.41 6 1.85 0.68 6 0.87 0.94 6 1.31 1.02 6 1.09 0.07 6 0.70 0.20 6 0.81 1.01 6 0.81 1.03 6 0.90
P value \0.001* \0.001* \0.001* \0.001* \0.001* 0.495 0.115 \0.001* \0.001*
*Significant at P 5 0.05 level.
Table IV. Skeletal changes after long-term use of the Silensor appliance SNA angle ( ) SNB angle ( ) ANB angle ( ) MP-FH angle ( ) ALFH (mm) AFH (mm) PFH (mm)
Baseline 80.80 6 4.10 75.53 6 3.93 5.27 6 1.94 27.20 6 5.86 72.14 6 6.20 127.44 6 8.56 86.17 6 9.08
Follow-up without Silensor appliance 80.64 6 3.84 75.69 6 3.93 4.94 6 2.13 28.68 6 6.10 73.66 6 6.23 129.01 6 8.72 86.17 6 8.74
Difference 0.16 6 1.32 0.16 6 0.82 0.32 6 1.90 1.48 6 1.77 1.52 6 1.02 1.56 6 1.20 0.00 6 1.25
P value 0.426 0.217 0.277 \0.001* \0.001* \0.001* 0.990
*Significant at P 5 0.05 level.
After 4 years on average of treatment with the Silensor appliance, the maxillary incisors showed significant retroclinations, with decreases in the U1-SN angle, U1NA angle, and U1-NA distance. There were significant proclinations of the mandibular incisors, with increases in the L1-MP and L1-NB angles. Furthermore, the relationship between the maxillary and mandibular incisors significantly changed, with decreases in overbite and overjet. Dental changes after long-term use of the Silensor appliance are shown in Table III. No significant changes were observed in the SNA and SNB angles. Regarding the intermaxillary relationships, the ANB angle did not change significantly. A downward rotation of the mandible was observed, with an increase in the MP-FH angle. There were increases in anterior lower facial height and anterior facial height. No significant changes were observed in posterior facial heights. Skeletal changes after long-term use of the Silensor appliance are shown in Table IV. In the group that used the Silensor for less than 3 years, changes were observed in interincisor relationships and skeletal measurements, with decreases in overbite and increases in the MP-FH angle, anterior lower facial height, and anterior facial height. In the group that used it for 3 years or longer, more changes were observed in the dental and skeletal measurements, with decreases in the U1-SN angle, U1-NA angle, U1-NA
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distance, overbite, overjet, and ANB angle; and increases in the L1-NB angle, MP-FH angle, anterior lower facial height, and anterior facial height. In addition, the differences between baseline and follow-up were greater than those in the less-than-3-years group. Significant dental and skeletal changes in relationship to time are shown in Table V. DISCUSSION
The use of MADs in the treatment of OSAHS is well established, and the therapeutic effect of MADs for treating OSAHS has been demonstrated.7,24,25 The usefulness of Silensor appliances for treating OSAHS is no longer in question. However, little is known about the long-term side effects after such treatment. In our study, the Silensor appliance was well tolerated by the subjects, and the questionnaire data also showed a relatively low proportion of subjective side effects. Furthermore, the subjective side effects were relieved with an extension of treatment time. We had a relatively high level of compliance compared with a long-term study.26 Only 1 patient after 1 year of treatment reported that his occlusion was somehow different from pretreatment, but he could not describe it precisely. We did not find any abnormalities. The patient was asked to continue to wear the Silensor appliance and to have clinical examinations at 3-month intervals. Otsuka et al27 concluded
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Table V. Significant dental and skeletal changes in relationship to time \3 years Overbite (mm) MP-FH angle ( ) ALFH (mm) AFH (mm) $3 years U1-SN angle ( ) U1-NA angle ( ) U1-NA distance (mm) L1-NB angle ( ) Overbite (mm) Overjet (mm) ANB angle ( ) MP-FH angle ( ) ALFH (mm) AFH (mm)
Difference
P value
Baseline
Follow-up without Silensor appliance
3.13 6 1.54 26.79 6 5.59 69.53 6 5.42 124.93 6 7.57
2.54 6 1.62 28.04 6 5.50 70.99 6 4.94 126.14 6 8.06
0.59 6 0.70 1.25 6 2.53 1.46 6 1.29 1.21 6 1.77
0.001* 0.031* \0.001* 0.004*
98.08 6 6.80 18.16 6 5.33 4.55 6 2.64 30.83 6 6.10 3.35 6 1.16 4.38 6 1.33 5.70 6 2.43 28.40 6 7.94 72.73 6 6.09 127.46 6 8.56
96.35 6 7.43 16.40 6 5.99 3.33 6 2.31 31.78 6 6.73 2.54 6 1.50 3.37 6 1.86 5.17 6 2.03 29.95 6 7.42 74.91 6 6.26 129.78 6 9.04
1.74 6 2.20 1.76 6 2.78 1.22 6 1.67 0.95 6 2.13 0.81 6 1.41 1.00 6 1.13 0.53 6 1.12 1.56 6 2.97 2.18 6 1.32 2.32 6 2.25
0.001* 0.007* 0.003* 0.049* 0.014* \0.001* 0.039* 0.023* \0.001* \0.001*
*Significant at P 5 0.05 level.
in their study that the occlusal contact area and bite force showed significant decreases after short-term oral appliance use. This information might explain our findings. The occlusal analysis could show statistically significant but clinically insignificant differences, and this might have clinical implications. An objective occlusal analysis by pressure sensor should be involved in the regular follow-up protocol. MAD therapy is considered to be a long-term treatment; therefore, the side effects on the dental and skeletal systems must be considered and well controlled. Cephalometric analysis has been widely used in orthodontics to record craniofacial morphology. Moreover, it has also been regarded as an effective research tool to evaluate the dental and skeletal changes associated with the long-term use of MADs in patients with OSAHS.15,16,18,28,29 In our study, there were mild but statistically significant dental and skeletal changes in patients after 4 years of treatment with the Silensor appliance. As a result of the orthodontic side effects of the Silensor appliance, retroclination of the maxillary incisors and proclination of the mandibular incisors with associated reductions in overbite and overjet were observed. The Silensor appliance with full-arch coverage imposed forces on the dentition, holding the mandible in a forward position, and the mandible had a tendency to return to a less constrained position. Therefore, a palatal force was applied to the maxillary incisors, and a labial force was applied to the mandibular incisors. As a consequence of the retroclination of the maxillary incisors and the proclination of the mandibular incisors, overbite and overjet decreased. With objective cephalometric analysis, similar results were also described in previous
studies.15,18 In contrast to our findings, Ringqvist et al28 found no significant changes in the inclination of the maxillary or mandibular incisors, overbite, and overjet after 4 years of treatment with MADs. The differences were most likely attributed to the different designs and the different mandibular protrusions of the MAD that they used compared with the Silensor appliance. First, the MAD that they used was a 1-piece splint that covered only the bilateral posterior teeth in both arches. Consequently, there were no directed forces acting on the maxillary or mandibular incisors. Second, 65% to 75% maximum protrusions were applied in our study, whereas they used 50% of the maximum protrusion to advance the mandible. This could be explained by the fact that we included patients with mild-to-severe OSAHS (apnea-hypopnea index range, 5-74) in our study. However, Ringqvist et al only included patients with mild-to-moderate OSAHS. Previous studies have shown that greater mandibular advancements proved to be more efficient in treating OSAHS.30,31 Thus, a greater mandibular advancement was needed by patients with severe OSAHS in our study. Marklund et al32 and Marklund33 implied that the degree of mandibular advancement was a predictor of orthodontic side effects. After long-term follow-up studies, they suggested that OSAHS patients could try a soft elastomeric device with a mandibular advancement less than 6 mm and a low-to-moderate vertical displacement to diminish the risks of orthodontic side effects. It would be increasingly important, since with increasing age, OSAHS symptomatology may worsen in patients who require a more extended protrusive mandibular position. The amount of mandibular advancement should primarily be considered in the overall therapeutic effect for
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OSAHS and must be properly titrated to prevent side effects. The design of the adjustable Silensor appliance could be beneficial in obtaining an optimal mandibular advancement by changing the connection bars with those of different lengths throughout treatment. Downward rotation of the mandible was observed, as the mandibular plane angle (MP-FH angle) increased significantly. Anterior lower facial height and anterior facial height were increased. These findings corroborate the results from previous studies.16,29 These skeletal changes, however, were predominantly induced by dental changes. Increases in lower and total anterior facial heights resulted from changes to the maxillary and mandibular incisors. Downward rotation of the mandible was caused by the retroclination of the maxillary incisors and the proclination of the mandibular incisors through incisal guidance, and lower and total anterior facial heights were thus increased. In our further analysis regarding treatment times, changes were initially observed in interincisor relationships and skeletal measurements in the \3 years group, with decreases in overbite and increases in the MP-FH angle, anterior lower facial height, and anterior facial height. Changes in incisor measurements were not evident. Similar changes were observed in the $3 years group. The differences in that group between baseline and follow-up were greater than those of the \3 years group. Furthermore, significant dental changes were observed, with retroclination of the maxillary incisors and proclination of the mandibular incisors, and reductions in overbite and overjet. This implies that skeletal changes tend to occur after treatment in a relatively short term. On the contrary, dental changes tend to occur with a longer treatment time. Although the results were obtained from different subjects with different treatment times, this potential change trend is still important in the clinic. Further regular long-term cephalometric reviews of these patients are needed. Moreover, in the \3 years group, facial height was increased significantly without obvious dental changes. Therefore, it seems that the incisal guidance mechanism is not the unique reason to explain the increases in lower and total anterior facial heights in our study. Robertson17 described similar results. In his study, changes of facial height, overbite, and overjet were observed after 6 months of treatment. These changes were attributed to repositioning of the head of the mandibular condyle in the glenoid fossa. Dental changes were initially observed at the 12-month review, and they enlarged with the increasing length of treatment. Obvious dental changes occurred much earlier in that study than in our study. The difference was most likely due to the different MAD used in his study; it was rigid with 75% of
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maximum protrusion. The semirigid Silensor appliance with 65% to 75% of maximum protrusion has the advantage of making a balance between optimal therapeutic effects and side effects. The strength of this study was the long-term use of the Silensor appliance, but there were some limitations. The compliance reported by the subjects was not objectively measured because there was no available compliance monitor. The wearing time and frequency of Silensor appliance use met the inclusion criteria, but these parameters were verified in different subjects; to some degree, this process was inexact. The large range of treatment times of the subjects was another limitation of this study. It would be more rigorous to divide the subjects into several groups according to treatment time and evaluate the side effects separately. Unfortunately, that is difficult to achieve because of the small number of subjects. Furthermore, because of the need for treatment or material aging, the Silensor appliances of 20 patients were adjusted or remade during the study. Despite that, the amounts of mandibular advancement and the vertical displacements still met the abovementioned manufacturing standard (mandibular advancements of 65%-75% of maximum protrusion and 4.5-5 mm of vertical displacements), and the basic data of the Silensor appliance was changed. In addition, the subjects who used the Silensor appliances had a mean age of 47 years (range, 26-70 years), when periodontal disease tends to increase; this could have resulted in errors in evaluating the dental changes. CONCLUSIONS
Our results showed that the Silensor appliances were well tolerated and preferred by most subjects. This study demonstrates that common but mild dental and skeletal changes were caused by the Silensor appliance over a long period of time. The changes after 1 to 3 years of use of the Silensor appliance were predominantly skeletal. Both dental and skeletal changes were observed simultaneously at treatment times longer than 3 years. Although these changes were unnoticed by most patients, patients should be told about these potential changes in the dentition and the skeleton, and regular reviews are recommended in the treatment of patients with OSAHS. REFERENCES 1. Bates CJ, McDonald JP. The relationship between severity of obstructive sleep apnoea/hypopnoea syndrome (OSAHS) and lateral cephalometric radiograph values: a clinical diagnostic tool. Surgeon 2005;3:338-46. 2. Kitahara Y, Hattori N, Yokoyama A, Nakajima M, Kohno N. Effect of CPAP on brachial-ankle pulse wave velocity in patients with OSAHS: an open-labelled study. Respir Med 2006;100:2160-9.
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3. Chen H, Lowe AA. Updates in oral appliance therapy for snoring and obstructive sleep apnea. Sleep Breath 2013;17:473-86. 4. Schwarting S, Huebers U, Heise M, Schlieper J, Hauschild A. Position paper on the use of mandibular advancement devices in adults with sleep-related breathing disorders. Sleep Breath 2007;11: 125-6. 5. Yow M. An overview of oral appliances and managing the airway in obstructive sleep apnea. Semin Orthod 2009;15:88-93. 6. Dieltjens M, Vanderveken OM, Hamans E, Verbraecken JA, Wouters K, Willemen M, et al. Treatment of obstructive sleep apnea using a custom-made titratable duobloc oral appliance: a prospective clinical study. Sleep Breath 2013;17:565-72. 7. Schmidt-Nowara W, Lowe A, Wiegand L, Cartwright R, PerezGuerra F, Menn S. Oral appliances for the treatment of snoring and obstructive sleep apnea: a review. Sleep 1995;18:501-10. 8. Kushida CA, Morgenthaler TI, Littner MR, Alessi CA, Bailey D, Coleman J Jr, et al. American Academy of Sleep. Practice parameters for the treatment of snoring and obstructive sleep apnea with oral appliances: an update for 2005. Sleep 2006;29:240-3. 9. Zhao Y, Zeng XL, Fu MK, Huang XZ. The relationship between the changes of upper airway and genioglossus muscle activity after the treatment with Snoreguard. Chin J Stomatol 2003;38:377-80. 10. Chan AS, Lee RW, Cistulli PA. Dental appliance treatment for obstructive sleep apnea. Chest 2007;132:693-9. 11. Tan YK, L'Estrange PR, Luo YM, Smith C, Grant HR, Simonds AK, et al. Mandibular advancement splints and continuous positive airway pressure in patients with obstructive sleep apnoea: a randomized cross-over trial. Eur J Orthod 2002;24:239-49. 12. Friedman M, Hamilton C, Samuelson CG, Kelley K, PearsonChauhan K, Taylor D, et al. Compliance and efficacy of titratable thermoplastic versus custom mandibular advancement devices. Otolaryngol Head Neck Surg 2012;147:379-86. 13. Suga H, Mishima K, Nakano H, Nakano A, Matsumura M, Mano T, et al. Different therapeutic mechanisms of rigid and semi-rigid mandibular repositioning devices in obstructive sleep apnea syndrome. J Craniomaxillofac Surg 2014;42:1650-4. 14. Nakano H, Mishima K, Matsushita A, Suga H, Matsumura M, Mano T, et al. Efficacy of the Silensor for treating obstructive sleep apnea syndrome. Oral Maxillofac Surg 2013;17:105-8. 15. Fritsch KM, Iseli A, Russi EW, Bloch KE. Side effects of mandibular advancement devices for sleep apnea treatment. Am J Respir Crit Care Med 2001;164:813-8. 16. Doff MH, Hoekema A, Pruim GJ, Huddleston Slater JJ, Stegenga B. Long-term oral-appliance therapy in obstructive sleep apnea: a cephalometric study of craniofacial changes. J Dent 2010;38:1010-8. 17. Robertson CJ. Dental and skeletal changes associated with longterm mandibular advancement. Sleep 2001;24:531-7. 18. Almeida FR, Lowe AA, Sung JO, Tsuiki S, Otsuka R. Long-term sequellae of oral appliance therapy in obstructive sleep apnea patients: part 1. Cephalometric analysis. Am J Orthod Dentofacial Orthop 2006;129:195-204.
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19. Hoffstein V. Review of oral appliances for treatment of sleepdisordered breathing. Sleep Breath 2007;11:1-22. 20. Piskin B, Sentut F, Sevketbeyoglu H, Avsever H, Gunduz K, Kose M, et al. Efficacy of a modified mandibular advancement device for a totally edentulous patient with severe obstructive sleep apnea. Sleep Breath 2010;14:81-5. 21. Steiner CC. Cephalometrics in clinical practice. Angle Orthod 1959; 29:8-29. 22. Wylie WL. Overbite and vertical facial dimensions in terms of muscle balance. Angle Orthod 1944;14:13-7. 23. Dahlberg G. Statistical methods for medical and biological students. New York: Interscience Publications; 1940. 24. Gotsopoulos H, Chen C, Qian J, Cistulli PA. Oral appliance therapy improves symptoms in obstructive sleep apnea: a randomized, controlled trial. Am J Respir Crit Care Med 2002;166:743-8. 25. Lim J, Lasserson TJ, Fleetham J, Wright JJ. Oral appliances for obstructive sleep apnoea. Cochrane Database Syst Rev 2006;25: CD004435. 26. Hammond RJ, Gotsopoulos H, Shen G, Petocz P, Cistulli PA, Darendeliler MA. A follow-up study of dental and skeletal changes associated with mandibular advancement splint use in obstructive sleep apnea. Am J Orthod Dentofacial Orthop 2007;132:806-14. 27. Otsuka R, Almeida FR, Lowe AA. The effects of oral appliance therapy on occlusal function in patients with obstructive sleep apnea: a short-term prospective study. Am J Orthod Dentofacial Orthop 2007;131:176-83. 28. Ringqvist M, Walker-Engstr€om ML, Tegelberg A, Ringqvist I. Dental and skeletal changes after 4 years of obstructive sleep apnea treatment with a mandibular advancement device: a prospective, randomized study. Am J Orthod Dentofacial Orthop 2003; 124:53-60. 29. Gong X, Zhao Y, Gao XM, Zeng XL. A follow-up study on the dental and skeletal changes of patients with obstructive sleep apnea and hypopnea syndrome treating by oral appliance. Chin J Orthod 2009;16:130-4. 30. Kato J, Isono S, Tanaka A, Watanabe T, Araki D, Tanzawa H, et al. Dose-dependent effects of mandibular advancement on pharyngeal mechanics and nocturnal oxygenation in patients with sleep-disordered breathing. Chest 2000;117:1065-72. 31. Walker-Engstr€ om ML, Ringqvist I, Vestling O, Wilhelmsson B, Tegelberg A. A prospective randomized study comparing two different degrees of mandibular advancement with a dental appliance in treatment of severe obstructive sleep apnea. Sleep Breath 2003;7:119-30. 32. Marklund M, Franklin KA, Persson M. Orthodontic side-effects of mandibular advancement devices during treatment of snoring and sleep apnea. Eur J Orthod 2001;23:135-44. 33. Marklund M. Predictors of long-term orthodontic side effects from mandibular advancement devices in patients with snoring and obstructive sleep apnea. Am J Orthod Dentofacial Orthop 2006; 129:214-21.
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Follow-up study of dental and skeletal changes in patients with obstructive sleep apnea and hypopnea syndrome with long-term treatment with the Silensor appliance Xiaoyu Wang,a Xu Gong,b Zhe Yu,c Xuemei Gao,d and Ying Zhaoe Beijing, China
Introduction: In this study, we aimed to investigate the dental and skeletal changes associated with long-term use of the Silensor appliance (Erkodent, Cologne, Germany) in patients with obstructive sleep apnea and hypopnea syndrome. Methods: The sample included 42 patients with mild-to-severe obstructive sleep apnea and hypopnea syndrome (mean apnea-hypopnea index, 27; range, 5-74) who had been treated with the Silensor appliance for an average of 4 years (range, 1-11 years). A questionnaire was used to assess of the side effects subjectively; the cephalometric analysis was conducted to identify the dental and skeletal changes of different treatment times objectively. Results: The Silensor appliance was associated with few subjective side effects. Most subjective side effects decreased after long-term use of the Silensor appliance. Significant changes after long-term use of the Silensor appliance were observed in incisor angulation, overbite, overjet, mandibular plane angle, anterior lower facial height, and anterior facial height. Overbite and skeletal changes at treatment times between 1 year and 3 years were a decrease in overbite and increases in the mandibular plane angle, anterior lower facial height, and anterior facial height. Overjet and other dental changes at treatment times longer than 3 years were a decrease in overjet, retroclination of the maxillary incisors, and proclination of the mandibular incisors. Conclusions: The Silensor appliance was well tolerated and preferred by most subjects. Common but mild dental and skeletal changes resulted from using the appliance over a long period of time. The changes after 1 to 3 years of use were skeletal changes predominantly. Both dental and skeletal changes were observed simultaneously at treatment times longer than 3 years. (Am J Orthod Dentofacial Orthop 2015;147:559-65)
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bstructive sleep apnea and hypopnea syndrome (OSAHS) is a sleep-related breathing disorder characterized by repeated narrowing or collapse of the upper airway during sleep, resulting in hypoxemia, arousal, and fragmentation of sleep.1,2 Since the first a Resident, Department of Dentistry, Xuanwu Hospital, Capital Medical University, Beijing, China. b Lecturer, Department of Orthodontics, School and Hospital of Stomatology, Peking University, Beijing, China. c Lecturer, Department of Dentistry, Xuanwu Hospital, Capital Medical University, Beijing, China. d Professor, Department of Orthodontics, School and Hospital of Stomatology, Peking University, Beijing, China. e Professor, Department of Dentistry, Xuanwu Hospital, Capital Medical University, Beijing, China. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: Ying Zhao ,No. 45 Changchun St, Xicheng District, Beijing, China 100053; e-mail, [email protected]. Submitted, February 2014; revised and accepted, January 2015. 0889-5406/$36.00 Copyright Ó 2015 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2015.01.013
description of the disease, many treatment methods have been attempted, including weight loss, medication, surgery, and continuous positive airway pressure (CPAP).3 Mandibular advancement devices (MADs) have also been reported to be an effective treatment option for patients with OSAHS.4-6 Therapy with MADs is increasingly popular not only because of its good efficacy, but also because of its simplicity, high acceptance, noninvasiveness, and low cost.7 According to the American Academy of Sleep Medicine, MADs are indicated in patients with primary snoring and upper airway resistance syndrome, patients with mild-to-moderate OSAHS who prefer MADs to CPAP, and those with severe OSAHS who refuse CPAP.8 Many MADs that vary in design are in use, but it is now recognized that the anterior repositioning of the mandible is an essential mechanism of the MAD by which the oropharyngeal space is increased.9,10 The Silensor appliance (Erkodent, Cologne, Germany) is a type of custom-made semirigid MAD with a satisfying efficacy11-14 and a low 559
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frequency of subjective side effects.11,14 Furthermore, a recent study suggested that the Silensor appliance is suitable for the first phase of oral appliance treatment for OSAHS.14 Dental and skeletal changes associated with longterm use of MADs have been studied with cephalometric analysis. Most authors evaluated the side effects induced by MAD use for an average of 2 to 3 years. In addition, in most studies, only patients with mild-to-moderate OSAHS or snorers were included.15-17 Among various authors, Almeida et al18 reported changes after at least 5 years of oral appliance use. However, the oral appliances in that study were rigid MADs and held the mandible in a fixed forward and slight downward position. MAD design is thought to be one factor that could affect the side effects from use of the appliance.19 Compared with rigid MADs, the Silensor appliance has an adjustable advancement of the mandible with mouth opening. Any further opening of the mouth increases the anterior displacement of the mandible. Therefore, a better understanding of the possible side effects after longterm treatment with semirigid MADs is meaningful. The aim of this study was to investigate the possible dental and skeletal changes associated with long-term use (4 years on average) of the Silensor appliance in patients with mild-to-severe OSAHS. MATERIAL AND METHODS
In this study, 56 subjects who fulfilled the following inclusion criteria were initially selected: (1) diagnosed with OSAHS based on polysomnography examination and suitable for Silensor appliance treatment (with mandibular retrognathia, a downward positioned hyoid bone, or a narrow oropharyngeal airway); (2) no mental or psychological illness; (3) enough teeth to retain the appliance without periodontitis; (4) no active temporomandibular dysfunction; (5) answered the pretreatment questionnaire and had cephalometric radiography; and (6) signed written informed consent. The follow-up polysomnography was completed after 4 weeks for the final adjustment of the Silensor appliance to evaluate the efficiency. Then 4 subjects who did not meet the success criteria based on the polysomnography examination (a decrease in the apnea-hypopnea index to \5 for mild OSAHS patients and a reduction in the apneahypopnea index by 50% for moderate and severe OSAHS patients20) were excluded. During this study, we recalled them for regular clinical reviews at 1-year intervals. At the end of this study, we recalled the subjects for questionnaires and follow-up cephalometric radiographs. The exclusion criteria included (1) not wearing the Silensor appliance for more than 5 hours per night and 5 days
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Table I. Clinical characteristics of the 42 subjects Parameter Sex Age (y) Apnea-hypopnea index Treatment time (y)
Value 31 men (74%), 11 women (26%) 47 6 10 (range, 26-70) 27 6 19 (range, 5-74) 4 6 3 (range, 1-11) \3 (22 subjects) $3 (20 subjects)
Fig 1. Design of the Silensor appliance.
per week for at least 1 year (5 subjects), (2) had CPAP therapy or surgical treatment during the study (2 subjects), (3) had tooth extractions or periodontal surgery during the study (1 subject), or (4) lost to follow-up (2 subjects). Overall, 42 subjects were included in this study. Their clinical characteristics are shown in Table I. All patients received treatment at the Department of Dentistry, Xuanwu Hospital, Capital Medical University, and the Department of Orthodontics, Peking University School and Hospital of Stomatology, in China. This study was approved by the institutional review board of Xuanwu Hospital, Capital Medical University. The Silensor appliance is a type of custom-made semirigid MAD, composed of soft methyl methacrylate and 2 separate splints connected by bars with 4 different lengths. Most teeth in both arches are covered by the splints, except for the third molars. The design of the Silensor appliance is shown in Figure 1. The Silensor appliance induced mandibular advancements of 65% to 75% of maximum protrusion and 4.5 to 5 mm of vertical displacements. The adjustment was performed during the first 2 to 4 weeks of treatment. Then a questionnaire was completed as the baseline after 4 weeks for the final adjustment of the Silensor appliance. The questionnaire included several yes or no questions that addressed the side effects. At the end of this study, we recalled the patients with long-term use of Silensor appliance, and the same questionnaire was repeated to evaluate the longterm subjective side effects.
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Table II. Questionnaire evaluations at baseline and follow-up Subjective side effects* Excessive salivation Dry mouth Dental discomfort Occlusal change Loosening of tooth Tongue discomfort Gingival discomfort Maxillofacial discomfort
Baseline 15 (36%) 7 (17%) 18 (43%) 0 (0%) 0 (0%) 0 (0%) 0 (0%) 15 (36%)
Follow-up 9 (21%) 4 (10%) 7 (17%) 1 (2%) 0 (0%) 0 (0%) 0 (0%) 2 (5%)
*Subjects were asked to mark “yes” when the side effect occurred subjectively.
Fig 2. Cephalometric analysis: landmarks, reference lines, angles, and distances. Points: S, sella; N, nasion; ANS, anterior nasal spine; A, innermost point on the anterior contour of the maxilla; B, innermost point on the contour of the mandible; Me, menton; Go, gonion; P, porion; Or, orbitale. Planes: SN, anterior cranial base; FH, Frankfort horizontal plane (P-Or); MP, mandibular plane (Me-Go); U1, maxillary incisor axis (connects incisor edge to root apex); L1, mandibular incisor axis (connects incisor edge to root apex). Dental: U1-SN angle, maxillary incisor angle related to SN; U1NA angle, maxillary incisor angle related to NA; U1-NA distance, maxillary incisal edge to NA; L1-MP angle, mandibular incisor angle related to MP; L1-NB angle, mandibular incisor angle related to NB; L1-NB distance, mandibular incisal edge to NB; U1-L1 angle, interincisal angle; OB, overbite, vertical overlap between the edges of the maxillary and mandibular incisors; OJ, overjet, horizontal distance between the maxillary incisal edge and the labial surface of the most prominent mandibular incisor. Skeletal: SNA angle, anteroposterior position of the maxilla; SNB angle, anteroposterior position of mandible; ANB angle, magnitude of the skeletal jaw discrepancy; MP-FH angle, mandibular plane angle; ALFH, anterior lower facial height (ANS-Me); AFH, anterior facial height (N-Me); PFH, posterior facial height (S-Go).
Standardized lateral cephalometric radiographs were routinely obtained at pretreatment as the baseline. At the end of this study, we recalled the patients not only for the questionnaire, but also for the follow-up lateral cephalometric radiograph (without the Silensor appliance). The baseline and the follow-up lateral cephalometric radiographs were measured and compared to evaluate dental and skeletal changes in the patients who received treatment with the Silensor appliance. The patients were asked to bite in intercuspation, breathe slowly, and not swallow during the radiograph
procedure. The cephalometric analysis was based on the methods of the Steiner21 and Wylie,22 using the professional cephalometric analysis software Dental Studio NX (version 6.0; Nemotec, La Plaine de Saint-Denis, France). The landmarks, reference lines, angles, and distances used in the cephalometric analysis are shown in Figure 2. To improve accuracy, all distances and angles were measured twice, on 2 separate occasions 2 weeks apart, by a blinded operator (X.W.). The method errorP was assessed P using Dahlberg's formula23: ME2 5 d2/2n, 2 where d is the sum of the squared differences between pairs of recordings, and n is the number of double measurements. The method error in the linear measurements fell within the range of 0.18 to 0.40 mm, and the angular measurements fell within 0.23 to 0.41 . The mean values were used for statistical analysis. Statistical analysis
The data are presented as the mean values and standard deviations. Dental and skeletal characteristics between the baseline and follow-up were compared using the Student paired t test (version 11.5) with a significance level of 0.05. Further analysis of the data was then undertaken by comparing each treatment time (\3 years and $3 years) between the baseline and follow-up. RESULTS
All 42 patients completed the questionnaire and underwent a clinical examination. The Silensor appliance was associated with a low rate of side effects. Most subjective side effects were decreased after long-term use of the Silensor appliance. Only 1 patient reported an occlusal change at the follow-up, but positive overjet and overbite and multiple occlusal contacts were maintained. The questionnaire data at baseline and at followup are shown in Table II.
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Table III. Dental changes after long-term use of the Silensor appliance Baseline 100.51 6 6.37 20.16 6 5.69 4.75 6 2.64 99.16 6 7.26 30.78 6 6.24 8.84 6 2.96 122.37 6 9.38 3.28 6 1.40 4.32 6 1.73
U1-SN angle ( ) U1-NA angle ( ) U1-NA distance (mm) L1-MP angle ( ) L1-NB angle ( ) L1-NB distance (mm) U1-L1 angle ( ) Overbite (mm) Overjet (mm)
Follow-up without Silensor appliance 99.02 6 6.86 18.75 6 6.28 4.07 6 2.68 100.10 6 7.24 31.80 6 6.29 8.91 6 2.93 122.57 6 9.20 2.27 6 1.46 3.29 6 1.75
Difference 1.49 6 1.55 1.41 6 1.85 0.68 6 0.87 0.94 6 1.31 1.02 6 1.09 0.07 6 0.70 0.20 6 0.81 1.01 6 0.81 1.03 6 0.90
P value \0.001* \0.001* \0.001* \0.001* \0.001* 0.495 0.115 \0.001* \0.001*
*Significant at P 5 0.05 level.
Table IV. Skeletal changes after long-term use of the Silensor appliance SNA angle ( ) SNB angle ( ) ANB angle ( ) MP-FH angle ( ) ALFH (mm) AFH (mm) PFH (mm)
Baseline 80.80 6 4.10 75.53 6 3.93 5.27 6 1.94 27.20 6 5.86 72.14 6 6.20 127.44 6 8.56 86.17 6 9.08
Follow-up without Silensor appliance 80.64 6 3.84 75.69 6 3.93 4.94 6 2.13 28.68 6 6.10 73.66 6 6.23 129.01 6 8.72 86.17 6 8.74
Difference 0.16 6 1.32 0.16 6 0.82 0.32 6 1.90 1.48 6 1.77 1.52 6 1.02 1.56 6 1.20 0.00 6 1.25
P value 0.426 0.217 0.277 \0.001* \0.001* \0.001* 0.990
*Significant at P 5 0.05 level.
After 4 years on average of treatment with the Silensor appliance, the maxillary incisors showed significant retroclinations, with decreases in the U1-SN angle, U1NA angle, and U1-NA distance. There were significant proclinations of the mandibular incisors, with increases in the L1-MP and L1-NB angles. Furthermore, the relationship between the maxillary and mandibular incisors significantly changed, with decreases in overbite and overjet. Dental changes after long-term use of the Silensor appliance are shown in Table III. No significant changes were observed in the SNA and SNB angles. Regarding the intermaxillary relationships, the ANB angle did not change significantly. A downward rotation of the mandible was observed, with an increase in the MP-FH angle. There were increases in anterior lower facial height and anterior facial height. No significant changes were observed in posterior facial heights. Skeletal changes after long-term use of the Silensor appliance are shown in Table IV. In the group that used the Silensor for less than 3 years, changes were observed in interincisor relationships and skeletal measurements, with decreases in overbite and increases in the MP-FH angle, anterior lower facial height, and anterior facial height. In the group that used it for 3 years or longer, more changes were observed in the dental and skeletal measurements, with decreases in the U1-SN angle, U1-NA angle, U1-NA
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distance, overbite, overjet, and ANB angle; and increases in the L1-NB angle, MP-FH angle, anterior lower facial height, and anterior facial height. In addition, the differences between baseline and follow-up were greater than those in the less-than-3-years group. Significant dental and skeletal changes in relationship to time are shown in Table V. DISCUSSION
The use of MADs in the treatment of OSAHS is well established, and the therapeutic effect of MADs for treating OSAHS has been demonstrated.7,24,25 The usefulness of Silensor appliances for treating OSAHS is no longer in question. However, little is known about the long-term side effects after such treatment. In our study, the Silensor appliance was well tolerated by the subjects, and the questionnaire data also showed a relatively low proportion of subjective side effects. Furthermore, the subjective side effects were relieved with an extension of treatment time. We had a relatively high level of compliance compared with a long-term study.26 Only 1 patient after 1 year of treatment reported that his occlusion was somehow different from pretreatment, but he could not describe it precisely. We did not find any abnormalities. The patient was asked to continue to wear the Silensor appliance and to have clinical examinations at 3-month intervals. Otsuka et al27 concluded
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Table V. Significant dental and skeletal changes in relationship to time \3 years Overbite (mm) MP-FH angle ( ) ALFH (mm) AFH (mm) $3 years U1-SN angle ( ) U1-NA angle ( ) U1-NA distance (mm) L1-NB angle ( ) Overbite (mm) Overjet (mm) ANB angle ( ) MP-FH angle ( ) ALFH (mm) AFH (mm)
Difference
P value
Baseline
Follow-up without Silensor appliance
3.13 6 1.54 26.79 6 5.59 69.53 6 5.42 124.93 6 7.57
2.54 6 1.62 28.04 6 5.50 70.99 6 4.94 126.14 6 8.06
0.59 6 0.70 1.25 6 2.53 1.46 6 1.29 1.21 6 1.77
0.001* 0.031* \0.001* 0.004*
98.08 6 6.80 18.16 6 5.33 4.55 6 2.64 30.83 6 6.10 3.35 6 1.16 4.38 6 1.33 5.70 6 2.43 28.40 6 7.94 72.73 6 6.09 127.46 6 8.56
96.35 6 7.43 16.40 6 5.99 3.33 6 2.31 31.78 6 6.73 2.54 6 1.50 3.37 6 1.86 5.17 6 2.03 29.95 6 7.42 74.91 6 6.26 129.78 6 9.04
1.74 6 2.20 1.76 6 2.78 1.22 6 1.67 0.95 6 2.13 0.81 6 1.41 1.00 6 1.13 0.53 6 1.12 1.56 6 2.97 2.18 6 1.32 2.32 6 2.25
0.001* 0.007* 0.003* 0.049* 0.014* \0.001* 0.039* 0.023* \0.001* \0.001*
*Significant at P 5 0.05 level.
in their study that the occlusal contact area and bite force showed significant decreases after short-term oral appliance use. This information might explain our findings. The occlusal analysis could show statistically significant but clinically insignificant differences, and this might have clinical implications. An objective occlusal analysis by pressure sensor should be involved in the regular follow-up protocol. MAD therapy is considered to be a long-term treatment; therefore, the side effects on the dental and skeletal systems must be considered and well controlled. Cephalometric analysis has been widely used in orthodontics to record craniofacial morphology. Moreover, it has also been regarded as an effective research tool to evaluate the dental and skeletal changes associated with the long-term use of MADs in patients with OSAHS.15,16,18,28,29 In our study, there were mild but statistically significant dental and skeletal changes in patients after 4 years of treatment with the Silensor appliance. As a result of the orthodontic side effects of the Silensor appliance, retroclination of the maxillary incisors and proclination of the mandibular incisors with associated reductions in overbite and overjet were observed. The Silensor appliance with full-arch coverage imposed forces on the dentition, holding the mandible in a forward position, and the mandible had a tendency to return to a less constrained position. Therefore, a palatal force was applied to the maxillary incisors, and a labial force was applied to the mandibular incisors. As a consequence of the retroclination of the maxillary incisors and the proclination of the mandibular incisors, overbite and overjet decreased. With objective cephalometric analysis, similar results were also described in previous
studies.15,18 In contrast to our findings, Ringqvist et al28 found no significant changes in the inclination of the maxillary or mandibular incisors, overbite, and overjet after 4 years of treatment with MADs. The differences were most likely attributed to the different designs and the different mandibular protrusions of the MAD that they used compared with the Silensor appliance. First, the MAD that they used was a 1-piece splint that covered only the bilateral posterior teeth in both arches. Consequently, there were no directed forces acting on the maxillary or mandibular incisors. Second, 65% to 75% maximum protrusions were applied in our study, whereas they used 50% of the maximum protrusion to advance the mandible. This could be explained by the fact that we included patients with mild-to-severe OSAHS (apnea-hypopnea index range, 5-74) in our study. However, Ringqvist et al only included patients with mild-to-moderate OSAHS. Previous studies have shown that greater mandibular advancements proved to be more efficient in treating OSAHS.30,31 Thus, a greater mandibular advancement was needed by patients with severe OSAHS in our study. Marklund et al32 and Marklund33 implied that the degree of mandibular advancement was a predictor of orthodontic side effects. After long-term follow-up studies, they suggested that OSAHS patients could try a soft elastomeric device with a mandibular advancement less than 6 mm and a low-to-moderate vertical displacement to diminish the risks of orthodontic side effects. It would be increasingly important, since with increasing age, OSAHS symptomatology may worsen in patients who require a more extended protrusive mandibular position. The amount of mandibular advancement should primarily be considered in the overall therapeutic effect for
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OSAHS and must be properly titrated to prevent side effects. The design of the adjustable Silensor appliance could be beneficial in obtaining an optimal mandibular advancement by changing the connection bars with those of different lengths throughout treatment. Downward rotation of the mandible was observed, as the mandibular plane angle (MP-FH angle) increased significantly. Anterior lower facial height and anterior facial height were increased. These findings corroborate the results from previous studies.16,29 These skeletal changes, however, were predominantly induced by dental changes. Increases in lower and total anterior facial heights resulted from changes to the maxillary and mandibular incisors. Downward rotation of the mandible was caused by the retroclination of the maxillary incisors and the proclination of the mandibular incisors through incisal guidance, and lower and total anterior facial heights were thus increased. In our further analysis regarding treatment times, changes were initially observed in interincisor relationships and skeletal measurements in the \3 years group, with decreases in overbite and increases in the MP-FH angle, anterior lower facial height, and anterior facial height. Changes in incisor measurements were not evident. Similar changes were observed in the $3 years group. The differences in that group between baseline and follow-up were greater than those of the \3 years group. Furthermore, significant dental changes were observed, with retroclination of the maxillary incisors and proclination of the mandibular incisors, and reductions in overbite and overjet. This implies that skeletal changes tend to occur after treatment in a relatively short term. On the contrary, dental changes tend to occur with a longer treatment time. Although the results were obtained from different subjects with different treatment times, this potential change trend is still important in the clinic. Further regular long-term cephalometric reviews of these patients are needed. Moreover, in the \3 years group, facial height was increased significantly without obvious dental changes. Therefore, it seems that the incisal guidance mechanism is not the unique reason to explain the increases in lower and total anterior facial heights in our study. Robertson17 described similar results. In his study, changes of facial height, overbite, and overjet were observed after 6 months of treatment. These changes were attributed to repositioning of the head of the mandibular condyle in the glenoid fossa. Dental changes were initially observed at the 12-month review, and they enlarged with the increasing length of treatment. Obvious dental changes occurred much earlier in that study than in our study. The difference was most likely due to the different MAD used in his study; it was rigid with 75% of
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maximum protrusion. The semirigid Silensor appliance with 65% to 75% of maximum protrusion has the advantage of making a balance between optimal therapeutic effects and side effects. The strength of this study was the long-term use of the Silensor appliance, but there were some limitations. The compliance reported by the subjects was not objectively measured because there was no available compliance monitor. The wearing time and frequency of Silensor appliance use met the inclusion criteria, but these parameters were verified in different subjects; to some degree, this process was inexact. The large range of treatment times of the subjects was another limitation of this study. It would be more rigorous to divide the subjects into several groups according to treatment time and evaluate the side effects separately. Unfortunately, that is difficult to achieve because of the small number of subjects. Furthermore, because of the need for treatment or material aging, the Silensor appliances of 20 patients were adjusted or remade during the study. Despite that, the amounts of mandibular advancement and the vertical displacements still met the abovementioned manufacturing standard (mandibular advancements of 65%-75% of maximum protrusion and 4.5-5 mm of vertical displacements), and the basic data of the Silensor appliance was changed. In addition, the subjects who used the Silensor appliances had a mean age of 47 years (range, 26-70 years), when periodontal disease tends to increase; this could have resulted in errors in evaluating the dental changes. CONCLUSIONS
Our results showed that the Silensor appliances were well tolerated and preferred by most subjects. This study demonstrates that common but mild dental and skeletal changes were caused by the Silensor appliance over a long period of time. The changes after 1 to 3 years of use of the Silensor appliance were predominantly skeletal. Both dental and skeletal changes were observed simultaneously at treatment times longer than 3 years. Although these changes were unnoticed by most patients, patients should be told about these potential changes in the dentition and the skeleton, and regular reviews are recommended in the treatment of patients with OSAHS. REFERENCES 1. Bates CJ, McDonald JP. The relationship between severity of obstructive sleep apnoea/hypopnoea syndrome (OSAHS) and lateral cephalometric radiograph values: a clinical diagnostic tool. Surgeon 2005;3:338-46. 2. Kitahara Y, Hattori N, Yokoyama A, Nakajima M, Kohno N. Effect of CPAP on brachial-ankle pulse wave velocity in patients with OSAHS: an open-labelled study. Respir Med 2006;100:2160-9.
American Journal of Orthodontics and Dentofacial Orthopedics
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American Journal of Orthodontics and Dentofacial Orthopedics
May 2015 Vol 147 Issue 5
