A Comparison Study of Upper Airway among Different Skeletal Craniofacial Patterns in Nonsnoring Chinese Children

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1 Originl Article A Comprison Study of Upper Airwy mong Different Skeletl Crniofcil Ptterns in Nonsnoring Chinese Children Zhe Zhong ; Zhihui Tng b ; Xuemei Go c ; Xing-Long Zeng c ABSTRACT Objective: Ptients with OSAS (obstructive sleep pne syndrome) demonstrte decresed upper irwy dimension nd crniofcil skeletl bnormlities. The study ws performed to nlyze whether upper irwy dimensions differed mong Chinese nonsnoring children of different sgittl nd verticl skeletl fcil morphologies. Mterils nd Methods: Lterl cephlometric records were used to mesure the dimensions of the upper irwy. Two groups of subjects were studied. A group of subjects with normodivergent fcil pttern (n 5 190; FH-MP ngle between 23.5u nd 30.5u) ws divided into three subgroups ccording to ANB ngle (Clss I, II, or III). A second group of subjects with norml sgittl fcil pttern (n 5 180; ANB ngle between 0.7u nd 4.7u) ws divided into three subgroups ccording to the FH-MP ngle (low ngle, norml ngle, or high ngle). All subgroups were mtched for ge nd sex. Results: In the group of subjects with normodivergent fcil pttern, significnt tendency for reduced upper irwy dimension in the inferior prt (pltophryngel nd hypophrynx) ws found in the Clss III, Clss I, nd Clss II subgroups, in tht order. In the group of subjects with norml sgittl fcil pttern, the superior prt of the irwy (nsophryngel nd pltophryngel) decresed with incresing mndibulr plne ngle. Conclusion: The sgittl nd verticl skeletl ptterns my be contributory fctors for the vrition of the inferior nd superior prt of the upper irwy, respectively. Skeletl deficiency of nonsnoring Chinese children my predispose them to upper irwy obstruction. (Angle Orthod. 2010;80: ) KEY WORDS: Nonsnoring children; Lterl cephlometry; Inferior prt of upper irwy; Superior prt of upper irwy; Sgittl skeletl fcil morphology; Verticl skeletl fcil morphology INTRODUCTION The pthogenesis of obstructive sleep pne (OSA) hs been investigted for mny yers. Previous studies of different smples hve shown n ssocition between crniofcil skeletl morphology nd upper irwy dimension in OSA ptients. 1 4 The conclusions noted vribles tht my ffect irwy size or ventiltion. These included mndibulr deficiency, bimxillry retrusion, steep occlusl plne, incresed mndibulr plne ngle, nd more cudlly positioned hyoid bone. 5 8 According to the close reltionship between the phryngel structures nd dentofcil structures in OSA ptients, mutul ssocition is expected to exist between the phryngel structures nd the dentofcil pttern in the common popultion. Mergen nd Jcobs 9 reported tht the midsgittl nsophryngel re nd the nsophryngel depth re significntly lrger in subjects with norml occlusion thn in those with Clss II mlocclusion. Solow et l 10 presumed tht irwy dequcy ws relted to the size nd position of the mndible rther thn mxillry vribles. Ceyln nd Okty 11 demonstrted tht the phryngel struc PhD Cndidte, Deprtment of Orthodontics, School nd Hospitl of Stomtology, Peking University, Beijing, People s Republic of Chin. b Grdute Student-M.S., Deprtment of Orthodontics, School nd Hospitl of Stomtology, Peking University, Beijing, People s Republic of Chin. c Professor, Deprtment of Orthodontics, School nd Hospitl of Stomtology, Peking University, Beijing, People s Republic of Chin. Corresponding uthor: Xing-Long Zeng, DDS, MSD, Deprtment of Orthodontics, School nd Hospitl of Stomtology, Peking University, No. 22 Zhong Gun Cun Southern Street, Beijing , People s Republic of Chin (e-mil: zeng_xinglong@sin.com) Accepted: August Submitted: Mrch G 2010 by The EH Angle Eduction nd Reserch Foundtion, Inc. DOI: /

2 268 ZHONG, TANG, GAO, ZENG tures were not ffected by chnges in the ANB ngle. De Freits et l 12 reported tht mlocclusion type did not influence upper phryngel irwy width; however, Clss II nd Clss III ptients with verticl growth ptterns hd significntly nrrower upper phryngel irwys thn those with norml growth pttern. The present study sought to ssess the effect of crniofcil morphology on the upper irwy dimension with sufficient smple size nd to control for interctions between sgittl nd verticl ptterns. In ddition, few studies of Chinese subjects hve been reported to dte. 13,14 Becuse cephlometry is useful nd inexpensive clinicl tool to evlute Chinese ptients with OSA, 15 we chose it for the mesurement of Chinese nonsnoring children. The im of the present study ws to investigte whether the upper irwy dimensions of Chinese nonsnoring children were ffected by sgittl nd verticl skeletl vribles, respectively. MATERIALS AND METHODS The smple for this study ws tken from the Deprtment of Orthodontics, School nd Hospitl of Stomtology, Peking University, Chin. A totl of 370 subjects, ges 11 to 16 yers, ws selected. All subjects were informed of the reserch content, nd consent form ws signed by ech child s prents. The study did not proceed without the pprovl of both the institutionl review bord nd the prticipnts prents. No subjects hd history of previous orthodontic/ orthopedic tretment or ny pltl/lip cleft symptom. The prents were questioned bout their children s medicl history to exclude ny children with chronic mouth brething, permnent snoring, nd tonsillectomy or denoidectomy. Subjects with obvious hyperplsi of tonsils nd denoids on cephlometric films were excluded from further nlysis. The subjects were divided into two groups: normodivergent fcil pttern group nd norml sgittl fcil pttern group. The selection criteri for the normodivergent fcil pttern group were FH-MP between 23.5u nd 30.5u (men 26.6u). This group ws divided into three subgroups ccording to the ANB ngle. Subgroup 1: Clss III, ie, ANB ngle smller thn 0.7u (54 subjects) Subgroup 2: Clss I, ie, ANB ngle between 0.7u nd 4.7u (82 subjects) Subgroup 3: Clss II, ie, ANB ngle lrger thn 4.7u (54 subjects) The selection criteri for the norml sgittl fcil pttern group were ANB ngle between 0.7u nd 4.7u (men 2.9u). This group ws divided into three subgroups ccording to the FH-MP ngle: Figure 1. Cephlometric lndmrks. Subgroup 1: Low ngle, ie, FH-MP ngle smller thn 23.5u (51 subjects) Subgroup 2: Norml ngle, ie, FH-MP ngle between 23.5u nd 30.5u (82 subjects) Subgroup 3: High ngle, ie, FH-MP ngle lrger thn 30.5u (47 subjects) Lterl cephlometric rdiogrphs were exposed with the ptients seted in n upright position with Frnkfort horizontl plne prlleled to the floor. Ptients were instructed to brethe t ese with the teeth in centric occlusion. The rdiogrphs were obtined with UNTPANOCP-80 cephlometer with liner mgnifiction of 11%. All the films were digitized with MICROTEK ScnMker4 scnner nd Photoshop 9.0 CS softwre. The cephlometric lndmrks nd nlysis were bsed on the methods described previously by Lowe et l, 16 Tngugsorn et l, 17 nd Liu et l. 18 The lndmrks nd mesurements identified in this study with OPAIM softwre re outlined in Figures 1 nd 2 nd Tble 1. One opertor mesured 10 films twice 1 week prt to determine repetbility of the mesurements, nd intrclss correltion coefficients were clculted. Sttisticl procedures were performed on the recorded dt using SPSS 11.0 softwre. One-wy nlysis of vrince (ANOVA) nd lest significnt difference (LSD) test for cephlometric comprison were performed mong the subgroups.

3 UPPER AIRWAY AMONG DIFFERENT CRANIOFACIAL PATTERNS 269 Figure 2. Cephlometric mesurements. To control distribution of sex nd ge in blnce nd to eliminte the interction between the sgittl nd verticl skeletl ptterns mong the three subgroups, the following nlyses were performed for both the normodivergent fcil pttern group nd the norml sgittl fcil pttern group. A chi-squre test ws performed to exmine the sex distribution in ech subgroup of the normodivergent fcil pttern group. No significnt difference ws detected (Tble 2). Age distribution ws compred mong the three subgroups (Tble 3), nd no sttisticl difference ws observed. For the norml sgittl fcil pttern group, the sme nlyses were performed. No significnt differences with regrd to sex or ge distribution were detected (Tbles 4 nd 5). RESULTS Intrclss correltion coefficients for the two seprte mesurements on the cephlometric rdiogrphs rnged between nd (Tble 6). Prt A: Normodivergent Fcil Pttern Group There ws no significnt difference in the nsophrynx s mesured from the PNS-R to SPP-SPPW levels mong the subgroups of normodivergent fcil pttern subjects (one-wy ANOVA). The sgittl dimension of the inferior prt of the upper irwy (pltophryngel nd hypophrynx) decresed from Tble 1. Cephlometric Lndmrks nd Mesurements Used in Figures 1 nd 2 Vrible Definition Lndmrks Hor Most inferior point of spheno-occipitl synchondrosis R Point of intersection of line from Hor to PNS nd posterior phryngel wll B Lowermost point on nterior mrgin of formen mgnum Ad1 Point of intersection of posterior phryngel wll nd line Ptm-B SPPW Point of intersection of line from soft plte center perpendiculr to posterior phryngel wll nd posterior phryngel wll SPP Point of intersection of line from soft plte center perpendiculr to posterior phryngel wll nd posterior mrgin of soft plte U The tip of the uvul MPW Foot point of perpendiculr line from point U to posterior phryngel wll TPPW Point of intersection of posterior phryngel wll nd extension of line B-Go TB Point of intersection of bse of the tongue nd extension of line B-Go V The most posteroinferior point on the bse of the tongue LPW Foot point of perpendiculr line from point V to posterior phryngel wll Upper irwy (mm) PNS-B Distnce between PNS nd B PNS-R Distnce between PNS nd R PNS-Ad1 Distnce between PNS nd Ad1 SPP-SPPW Distnce between SPP nd SPPW U-MPW Distnce between U nd MPW TB-TPPW Distnce between TB nd TPPW U-MPW Distnce between U nd MPW TB-TPPW Distnce between TB nd TPPW V-LPW Distnce between V nd LPW Crniomxillry complex S-N (mm) Distnce between S nd N ANS-PNS (mm) Distnce between ANS nd PNS PNS-B (mm) Distnce between PNS nd B Mndibulr size nd position Ar-Gn (mm) Distnce between Ar nd Gn Go-Gn (mm) Distnce between Go nd Gn FH plne Plne defined by Or nd Por NP plne Plne defined by N nd Pog FH-NP (u) Angle between FH plne nd NP plne Clss III to Clss I to Clss II, nd these differences were significnt. The most significnt difference existed t the TB-TPPW level of the low orophrynx (P,.01) (Tble 7, Figure 3). Pirwise comprisons mong subgroups were done vi the LSD test (Tble 8). The dt demonstrted significnt difference between Clss II nd Clss III subgroups t the levels of the uvul, low orophrynx, nd hypophrynx. At the level of TB-TPPW there ws

4 270 ZHONG, TANG, GAO, ZENG Tble 2. Sex Distribution in the Subgroups of Subjects with Normodivergent Fcil Pttern Clss I Clss II Clss III Totl P Femle Mle Totl significnt difference between the Clss I nd Clss III subgroups. The literture suggests tht there is reduced tendency from Clss III to Clss I to Clss II for the dimension of the inferior prt of the upper irwy, nd this my contribute to the different mndibulr sizes nd positions. The LSD test ws pplied to the mesurements of the mndibulr size nd position, nd the results showed significnt difference (Tble 9). Prt B: Norml Sgittl Fcil Pttern Group A sttisticlly significnt difference ws found mong the subgroups in the nsophrynx, s mesured on the PNS-R nd PNS-Ad1 levels nd in the pltophryngel re s mesured on the SPP- SPPW level with (one-wy ANOVA). The superior prt of the upper irwy dimension decresed with n incresing FH-MP ngle. However, no significnt difference could be found in the inferior prt of the upper irwy, in contrst to the normodivergent group (Tble 10, Figure 4). The LSD test for pirwise comprisons ws performed to determine whether there were differences in the superior upper irwy mong the subgroups (Tble 11). The dt demonstrted significnt difference, except between the norml-ngle nd high-ngle subgroups. We tested for significnt differences in the size of the crniomxillry complex mong the subgroups. There were significnt differences in S-N, ANS-PNS, nd PNS-B (Tble 12). DISCUSSION Norml respirtion is dependent on sufficient ntomicl dimensions of the irwy. In recent yers, mny studies hve contributed to the knowledge tht vritions in the skeletl pttern could predispose persons to upper irwy obstruction. Bcon et l 19 Tble 4. Sex Distribution in the Subgroups of Subjects with Norml Sgittl Fcil Pttern Low Angle Norml Angle High Angle Totl P Femle Mle Totl reported tht lower fce height ws the leding fctor ffecting the phrynx. Liu et l 20,21 demonstrted tht OSA ptients with more retrognthic mndibles showed significntly higher pne index nd respirtory disturbnce index. They lso reported tht OSA ptients showed Clss II nd hypodivergent skeletl pttern compred with norml popultion. In 1999, Go et l 22 reported tht nsophryngel size is closely ssocited with OSA syndrome. More recently, scholrs hve focused on ssessing the intrinsic reltionship between crniofcil morphology nd upper irwy morphology in orthodontic popultions to predict the occurrence of OSA nd to fcilitte tretment for OSA ptients. Becuse of inconsistencies in the conclusion of these studies, we tried to enhnce the knowledge in the field by controlling for known fctors. We expnded the smple size nd controlled the distribution of sex nd ge, without significnt differences mong the three subgroups of ech group. The influence of tonsil nd denoid hypertrophy ws lso limited. The influence of verticl skeletl pttern ws excluded in the normodivergent group to detect the effects of sgittl skeletl pttern on upper irwy structure nd the influence of sgittl skeletl pttern in group of subjects with norml ANB ngle. Therefore, the interference of mny interrelted nd confounding vribles ws minimized, since the selection criteri were defined strictly. In this study, the sgittl skeletl pttern did not ffect the dimensions of the nsophrynx in the normodivergent fcil pttern group. In greement with our findings, Sos et l 23 could find no cler-cut reltionship between the nsophryngel re nd Clss I or Clss II, division 1, mlocclusions. Wenzel et l 24 reported no correltions between irwy size nd mndibulr morphology, lthough significnt reltionship ws observed between chnges in nsophryngel irwy size nd mxillry prognthism. How- Tble 3. Age Distribution in the Subgroups of Subjects with Normodivergent Fcil Pttern N Men SD P Clss I Clss II Clss III Tble 5. Age Distribution in the Subgroups of Subjects with Norml Sgittl Fcil Pttern N Men SD P Low ngle Norml ngle High ngle

5 UPPER AIRWAY AMONG DIFFERENT CRANIOFACIAL PATTERNS 271 Tble 6. Intrclss Correltion Coefficients of Cephlometric Mesurements No. of Cses No. of Items Intrclss Correltion PNS-R ,.01** PNS-Ad ,.01** McNmr line ,.01** SPP-SPPW ,.01** U-MPW ,.01** TB-TPPW ,.01** V-LPW ,.01** P ever, Kerr 25 reported tht Clss II mlocclusion subjects showed smller nsophryngel dimensions compred with Clss I nd norml occlusion subjects. However, in his study, control of verticl skeletl pttern ws not emphsized. With respect to the inferior prt of the upper irwy, the results of this study seemed to suggest tht the dimension of the orophrynx decresed mrkedly, from Clss III to Clss I to Clss II subgroups, in the normodivergent fcil pttern group. A significnt difference ws found between the Clss II nd Clss III subgroups t ll levels, from U-MPW to V-LPW. At the level of TB-TPPW, significnt difference existed between the Clss I nd Clss III subgroups. However, no significnt differences were found between the Clss I nd Clss II subgroups for ll the levels checked. Ceyln nd Okty 11 climed tht the phryngel structures were not ffected by the ANB ngle, lthough they found significnt difference in the orophryngel re between Clss I nd Clss III, s well s between Clss II nd Clss III. Also, no verticl role could be found in his study. Most recently, Freits Tble 7. Cephlometric Comprison of Normodivergent Subgroups Mesurement Men SD P PNS-R I II III PNS-Ad1 I II III SPP-SPPW I II III U-MPW I ,.05* II III TB-TPPW I ,.01** II III V-LPW I ,.05* II III I indictes Clss I; II, Clss II; nd III, Clss III. Figure 3. Cephlometric comprison of normodivergent subgroups (Clss I, Clss II, nd Clss III). et l 12 mesured the dimensions of the upper nd lower orophrynx nd found no significnt difference between Clss I nd Clss II mlocclusions. Although tht study clssified its smple by molr reltionships, which differed from the present clssifiction by skeletl pttern subgroups, the results were similr. It seems tht the sgittl skeletl pttern predisposes pltophrynx nd hypophrynx obstruction s result of the decresed size nd posterior position of the mndible. Lm et l 26 found tht retroposition of the mndible ws ssocited with severe OSA in Chinese subjects. Similrly, the reserch of Hou et l 27 showed tht mndibulr body length ws significnt predictor for OSA. Ang et l 28 suggested tht the mndible tended to be more retrognthic in their moderte to severe smple of OSA ptients. When we detected difference in mndible size nd position mong the subgroups, the sme significnt reduced tendency ws seen with the dimension of the inferior prt of the upper irwy, from the Clss III to the Clss I to the Clss II subgroups. The phryngel cephlometric nlysis in this study reveled significnt dimensionl differences in the superior prt of the upper irwy mong hypodivergent, normodivergent, nd hyperdivergent subgroups of norml sgittl fcil pttern subjects. Dimensions t the PNS-R nd PNS-Ad1 levels in the nsophrynx Tble 8. Multiple Comprison of Inferior Prt of Upper Airwy with LSD Test in the Normodivergent Subgroups Mesurement Subgroups Men P U-MPW I-II I-III II-III 1.68,.05* TB-TPPW I-II I-III 21.78,.05* II-III 2.64,.01** V-LPW I-II I-III II-III 1.80,.01** I indictes Clss I; II, Clss II; nd III, Clss III.

6 272 ZHONG, TANG, GAO, ZENG Tble 9. Cephlometric Comprison of Mndible Size nd Position in the Normodivergent Subgroups Mesurement Subgroups Men P Ar-Gn I-II 3.15,.01** I-III 25.87,.01** II-III 29.02,.01** Go-Gn I-II 2.66,.01** I-III 23.86,.01** II-III 26.51,.01** FH-NP I-II 1.365,.05 I-III ,.01** II-III ,.01** I indictes Clss I; II, Clss II; nd III, Clss III. decresed with n incresing Frnkfort mndibulr plne ngle. So did the dimension t SPP-SPPW in the middle of the pltophrynx. From the U-MPW level to the V-LPW level of the hypophrynx, no significnt dimensionl difference could be found mong the subgroups. Since no significnt difference in the ANB ngle distribution existed in the subgroups, the impct of different sgittl skeletl pttern on the superior prt of the upper irwy ws excluded. The finding is in greement with Kerr, 25 who suggested tht the depth of the nsophrynx correltes with fce height. Joseph et l 29 lso reported tht the nsophryngel irwy in hyperdivergent individuls ws significntly nrrower thn in normodivergent individuls. However, they suggested tht the difference occurred becuse of the reltive bimxillry retrusion exhibited by the hyperdivergent group. Their selection criteri of n experimentl group included lip incompetence of 4 mm nd no medicl history regrding denoids nd tonsils; moreover, there ws Tble 10. Cephlometric Comprison of Norml Sgittl Subgroups Mesurement Subgroups Men SD P PNS-R Low ngle ,.01** Norml ngle High ngle PNS-Ad1 Low ngle ,.01** Norml ngle High ngle SPP-SPPW Low ngle ,.01** Norml ngle High ngle U-MPW Low ngle Norml ngle High ngle TB-TPPW Low ngle Norml ngle High ngle V-LPW Low ngle Norml ngle High ngle Figure 4. Histogrm plots of cephlometric comprison of norml sgittl subgroups (low-ngle, norml-ngle, nd high-ngle). no restriction of sgittl skeletl pttern in the subjects in their study. Freits et l 12 lso demonstrted tht verticl growth ptterns influence the upper orophryngel irwys but hve no impct on the lower orophryngel irwys in Clss I nd Clss II mlocclusion. Interestingly, our findings in the norml sgittl group re in greement with this. The reltionship between the superior prt of the upper irwy nd the verticl fcil pttern my be result of deficient development of the crniomxillry complex. Hou et l 27 suggested tht norml-weight OSA ptients hd significntly shorter nterior crnil bse nd mxillry length. Poli et l 30 hd found tht ptients of OSA with body mss index,30 hd shorter nterior floor of crnil bse. In this study, the nlysis of the crniofcil skeleton demonstrted tht the dimensions of S-N, ANS-PNS, nd PNS-B lso decresed with increses in the Frnkfort mndibulr plne ngle. The identicl tendency my imply tht the deficient development of the crniomxillry complex cused the decrese in the superior prt of the upper irwy dimensions in hyperdivergent ptients. As result, we suggest sgittl fcil pttern s the potentil explntion for the discrepncy in the depth of the inferior prt of the upper irwy s result of Tble 11. Multiple Comprison of Superior Prt of Upper Airwy Depth with LSD Test of Norml Sgittl Subgroups Mesurement Subgroups Men P PNS-R L-N 1.4,.05* L-H 2.2,.01** N-H PNS-Ad1 L-N 2.2,.01** L-H 3.4,.01** N-H SPP-SPPW L-N 1.8,.01** L-H 2.2,.01** N-H L indictes low ngle; N, norml ngle; nd H, high ngle.

7 UPPER AIRWAY AMONG DIFFERENT CRANIOFACIAL PATTERNS 273 Tble 12. Cephlometric Comprison of Crniomxillry Complex Among Norml Sgittl Subgroups Mesurement Subgroups Men P S-N L-N 1.5,.01** L-H 2.2,.01** N-H ANS-PNS L-N 1.2,.01** L-H 1.9,.01** N-H 0.7,.05* PNS-B L-N 0.9,.01** L-H 2.6,.01** N-H 1.7,.01** L indictes low ngle; N, norml ngle; nd H, high ngle. mndibulr size nd position. A verticl fcil pttern ws responsible for the deficiency in depth of the superior prt of the upper irwy becuse of the crniomxillry complex. We believe tht the upper irwy obstruction of OSA ptients could be trced bck to their juvenile stge, with susceptible crniofcil morphology s the potentil mechnism. The present study prtilly demonstrted tht skeletl deficiency might predispose person to upper irwy nrrowing, which in turn might predispose the person to obstruction in popultion without permnent snoring. A longitudinl study of crniofcil morphology s potentil pthogenic fctor is wrrnted in the future. CONCLUSIONS N The present study confirms the ssocition between phryngel structure nd sgittl or verticl crniofcil skeletl pttern in nonsnoring Chinese children. N The sgittl skeletl pttern my be contributory fctor in vritions in the inferior prt of the upper irwy. N Vritions in the superior prt of the upper irwy my be ttributble to verticl skeletl pttern. ACKNOWLEDGEMENT This study ws supported by the Ntionl Nturl Sciences Foundtion of the Peoples Republic of Chin Grnts REFERENCES 1. Lowe AA, Sntmti JD, Fleethm JA, et l. Fcil morphology nd obstructive sleep pnoe. Am J Orthod Dentofcil Orthop. 1986;90: Bcon WH, Turbot JC, Krieger J, et l. Crniofcil chrcteristics in ptients with obstructive sleep pnoes syndrome. Cleft Plte J. 1988;25: Hui DS, Ko FW, Chu AS, et l. Cephlometric ssessment of crniofcil morphology in Chinese ptients with obstructive sleep pne. Respir Med. 2003;97: Bttgel JM, L Estrnge PR. The cephlometric morphology of ptients with obstructive sleep pnoe. Eur J Orthod. 1996;18: Jmieson A, Guilleminult C, Prtinen M, Quer-Slv MA. Obstructive sleep pne ptients hve crniomndibulr bnormlities. Sleep. 1986;9: Tngugsorn V, Sktvedt O, Krogstd O, Lyberg T. Obstructive sleep pne: cephlometric study. Prt I. Cervicocrniofcil skeletl morphology. Eur J Orthod. 1995;17: Tsuchiy M, Lowe AA, Pe EK, Fleethm JA. Obstructive sleep pne subtypes by cluster nlysis. Am J Orthod Dentofcil Orthop. 1992;101: Andersson L, Brtttrom V. Cephlometric nlysis of permnently snoring ptients with nd without obstructive sleep pne syndrome. Int J Orl Mxillofc Surg. 1991;20: Mergen DC, Jcobs RM. The size of nsophrynx ssocited with norml occlusion nd Clss II mlocclusion. Nsophrynx. 1970;40: Solow B, Siersbæk-Nielsen S, Greve E. Airwy dequcy, hed posture, nd crniofcil morphology. Am J Orthod. 1984;86: Ceyln I, Okty H. A study on the phryngel size in different skeletl ptterns. Am J Orthod Dentofcil Orthop. 1995;108: De Freits MR, Alczr NM, Jnson G, et l. Upper nd lower phryngel irwys in subjects with Clss I nd Clss II mlocclusions nd different growth ptterns. Am J Orthod Dentofcil Orthop. 2006;130: Shen GF, Smmn N. Cephlometric studies on the upper irwy spce in norml Chinese. Int J Orl Mxillofc Surg. 1994;23: Zeng XL, Forsberg CM, Linder AS. Crniofcil morphology in Chinese nd Swedish Children with Angle Clss I nd Clss II occlusion reltion. Aust Orthod J. 1998;15: Chng ET, Shio GM. Crniofcil bnormlities in Chinese ptients with obstructive nd positionl sleep pne. Sleep Med. 2008;9: Lowe AA, Ono T, Fleethm JA, et l. Cephlometric comprisons of crniofcil nd upper irwy structure by skeletl subtype nd gender in ptients with obstructive sleep pne. Am J Orthod Dentofcil Orthop. 1996;110: Tngugsorn V, Sktvedt O, Krogstd O, et l. Obstructive sleep pne: cephlometric study. Prt II. Uvulo-glossophryngel morphology. Eur J Orthod. 1995;17: Liu Y, Zeng X, Lowe AA, et l. Effects of mndibulr repositioner on obstructive sleep pne. Am J Orthod Dentofcil Orthop. 2000;118: Bcon WH, Krieger J, Stierle JL, et l. Cephlometric evlution of phryngel obstructive fctors in ptients with sleep pnes syndrome. Angle Orthod. 1989;60: Liu Y, Zeng X, Fu M, Hung X. A comprtive study on the severity of respirtory disturbnce mong the OSAS ptients with different crniofcil morphology. J Clin Stomtology. 1998;14: Liu Y, Lowe AA, Zeng X, Fu M, Fleethm JA. Cephlometric comprisons between Chinese nd Cucsin ptients with obstructive sleep pne. Am J Orthod Dentofcil Orthop. 2000;117: Go X, Zeng X, Fu M, Hung X. Nsophrygel size in obstructive sleep pne syndrome. Chin J Otorhinolryngol. 1999;34: Sos FA, Grber TM, Muller TP. Postphryngel lymphdenoid tissue in Angle Clss I nd Clss II mlocclusions. Am J Orthod. 1982;81:

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