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Camouflage treatment in skeletal Class III cases combined with severe crowding by extraction of four premolars
orthodontic waves 68 (2009) 80–87
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/odw
Research paper
Camouflage treatment in skeletal Class III cases combined with severe crowding by extraction of four premolars Fang Ning, Yinzhong Duan *, Na Huo Department of Orthodontics, School of Stomatology, The Fourth Military Medical University, No. 145 West Changle Road, Xi’an 710032, PR China
article info
abstract
Article history:
Purpose: To evaluate the changes in dentoskeletal structures and profile after extraction of
Received 4 July 2008
four premolars in adult skeletal Class III borderline cases.
Received in revised form
Subjects and methods: Thirteen Chinese patients (mean age was 22.0 4.5 years) with
14 January 2009
skeletal Class III malocclusions and severe crowding in the upper arch were included in
Accepted 21 January 2009
the study. These cases were diagnosed to be in the borderline surgical-orthodontic range but
Published on line 23 February 2009
refused surgical treatments. All of them were treated by extraction of four premolars and standard edgewise technique. Lateral cephalometric radiographs taken at the start and end
Keywords:
of treatment were analysed. Twenty-six cephalometric variables were calculated and paired
Adult
t-tests were performed to assess the statistical significance of the treatment effects.
Skeletal Class III
Results: No significant changes were noted in the skeletal parameters (P 0.05). Regarding
Crowding
the dental parameters, the L1-MP angle decreased by 8.48, the U1-L1 angle increased by 11.78
Extraction
(P < 0.01), the L1-NB angle decreased by 10.18 and the L1-NB distance decreased by 5.2 mm (P < 0.01). The soft tissue parameters of Li-E, Li-H and Li-RL2 distance decreased by 3.3 mm, 3.3 mm and 4.5 mm, respectively (P < 0.01). All the patients finished with favorable occlusion and a straight profile. Conclusions: The orthodontic camouflage by extraction of four premolars provides a viable treatment alternative for borderline skeletal Class III cases to achieve satisfying occlusal relationship and improve facial esthetics. # 2009 Elsevier Ltd and the Japanese Orthodontic Society. All rights reserved.
1.
Introduction
Skeletal Class III is one of the most common malocclusions in orthodontic clinics in China, which can be corrected by either orthopedic, camouflage orthodontic, or combined surgicalorthodontic treatment. Different treatment approaches depends on the age of the patient, the pattern of malocclusion, its severity and patient’s request [1]. Studies have reported
that skeletal Class III discrepancy worsens with age [2,3]. Early intervention of skeletal Class III deformities in the mixed dentition or even in the deciduous dentition has received increasing attention in the orthodontic field. The alternative approaches include the use of reverse headgears, chin cups and functional appliances [4–8]. As for adult skeletal Class III patients, surgical-orthodontic therapy is often the recommended choice because it achieves a satisfying result, and the
* Corresponding author. Tel.: +86 29 84776138; fax: +86 29 83223047. E-mail address: [email protected] (F. Ning). 1344-0241/$ – see front matter # 2009 Elsevier Ltd and the Japanese Orthodontic Society. All rights reserved. doi:10.1016/j.odw.2009.01.004
orthodontic waves 68 (2009) 80–87
outcomes tend to be stable. However, sometimes, patients, especially borderline cases do not readily accept surgery because of the potential risk. Could orthodontic camouflage treatment work well in these cases? It provides a big challenge for orthodontists to satisfy individual’s request. Camouflage treatment can be carried out by different tooth extraction mode including lower second molars or premolars. Lin [9,10] successfully treated 13 severe skeletal Class III cases with tipe-edge technique and extraction of bilateral lower second molars. After treatment, the remarkable soft tissue change was noted and concave facial profiles improved to straight profiles. However, second molars extraction should be carefully selected, because the third molars do not always make satisfactory replacements for the lower second molars [11]. Lew [12] evaluated profile changes after extracting only two lower first premolars in Class III adults and considered this approach appeared to be a viable alternative in mild-tomoderate Class III patients who decline orthognathic surgery. Skeletal Class III cases sometimes accompany with severe crowding in the upper arch, which might due to the constriction of dental arches or some bad oral habits, such as tongue thrusting, sucking fingers, etc. However, few systemic studies ever reported the effects of camouflage treatment in such borderline skeletal Class III patients except few case reports [13,14]. Therefore, the aims of this retrospective study were to determine the changes in dentoskeletal structures and profile of adult Class III patients with severe crowding in upper dentition by extraction of four premolars and standard edgewise technique.
2.
Subjects and methods
2.1.
Subjects
81
each quadrant was extracted. Class III elastics were used in some cases where required. The mean duration of treatment was 2.1 0.4 years. The study protocol was approved by the Ethics Committee of the Fourth Military Medical University. The main idea in the treatment was extracting four premolars to relieve the upper arch crowding and to decrease the lower arch. We should be cautious to extract the upper premolars to avoid the reversed overjet after treatment. With extraction of two lower premolars in the mandible, there was much backward movement of the lower teeth. This contributed to correct the anterior crossbite and achieve Class I molar relationship [16–20].
2.2.
Cephalometric analysis
Standardized lateral cephalometric radiographs of each patient were obtained at the start and end of treatment. Each radiograph used in the present study were taken in the same cephalostat and traced on acetate paper. Twenty-six cephalometric landmarks (Figs. 1–3) were identified [12,15,21]. All the tracings and measurements were manually carried out twice with a 2-week interval by one examiner with a sharp pencil under optimal conditions. The method error in locating, superimposing and measuring the changes of different landmarksqffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi was ffi calculated by the Dahlberg’s formula P 2 Me ¼ d =2n, where d represents the difference between two registrations and n is the number of duplicate registrations. The method error determined was 0.3 mm for linear measurement and 0.4o for angular measurement, which were both statistically insignificant (P 0.05).
Five male and eight female consecutive patients (mean age: 22.0 4.5 years) were included in this study. All of these cases were treated with an orthodontic camouflage approach and had undergone the treatment at the Department of Orthodontics, School of stomatology, Fourth Military Medical University during the period from 2002 to 2008. Criteria for selection of subjects were as follows: (1) The molar relationships were between half- to full-unit Class III; (2) Anterior crossbite; (3) Concave facial profile; (4) 38 < ANB < 08; (5) No mandibular shift due to occlusal interference or premature contact of teeth; (6) No congenitally missing teeth (excluding third molars); (7) Severe crowding in the upper arches (arch length discrepancy <8 mm); (8) Patients and their families intensely rejected surgery; (9) Adult patients (ages 17 years) [15]; (10) No subjects had undergone orthodontic therapy of any type prior to this treatment. All patients were treated with the standard edgewise technique. In these cases, either the first or second premolar in
Fig. 1 – Skeletal measurements used in the study SN indicates Sella-nasion plane; RL1, horizontal reference line; RL2, vertical reference line; 1. SNA, 2. SNB, 3. ANB, 4. SN-MP, 5. Pg-NB, 6. A-RL1, 7. A-RL2, 8. B-RL2, 9. Ar-Pg, 10. Co-A and 11. Co-Gn.
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orthodontic waves 68 (2009) 80–87
2.3.
Statistical analysis
The statistical analysis was processed with SPSS 10.0 for Windows. The arithmetic mean and standard deviation were calculated for each variable. Paired t-tests were performed to assess the statistical significance of any dental and skeletal change. The levels of significance were: P 0.05 (NS), *P < 0.05; **P < 0.01.
3.
Results
At the end of the treatment, the anterior crossbite was corrected and Class I molar and canine relationships were achieved in all subjects. The facial profile was improved dramatically from a concave to a straight profile.
3.1.
Skeletal changes
No significant anteroposterior or vertical skeletal changes were identified during treatment (P 0.05).
3.2. Fig. 2 – Dental measurements used in the study SN indicates Sella-nasion plane; RL1, horizontal reference line; RL2, vertical reference line; 1. U1-SN, 2. L1-MP, 3. U1L1, 4. U1-NA (degree), 5. U1-NA (mm), 6. L1-NB (degree), 7. L1-NB (mm) and 8. OP-FH.
Dental changes
According to the pretreatment and posttreatment comparisons, statistically significant differences were noted in five dental measurements. L1-MP angle decreased by 8.48, U1-L1 angle increased by 11.78, L1-NB angle decreased by 10.18 and L1-NB distance decreased by 5.2 mm (P < 0.01). U1-SN decreased by 2.18 (P < 0.05) (Table 1).
3.3.
Soft tissue changes
After treatment, the results were statistically significant with Cm-Sn-Ls increased by 38 and Ls-RL2 distance decreased by 1.6 mm (P < 0.05), also Li-E distance decreased by 3.3 mm, Li-H distance decreased by 3.3 mm and Li-RL2 distance decreased by 4.5 mm (P < 0.01) (Table 1).
4.
Fig. 3 – Soft tissue measurements used in the study SN indicates Sella-nasion plane; RL1, horizontal reference line; RL2, vertical reference line; 1. Upper lip to E plane, 2. Lower lip to E plane, 3. Lower lip to H line, 4. Cm-Sn-Ls, 5. Ls-RL2, 6. Li-RL2 and 7. A-Ls.
Case report
A woman aged 18 years with chief complaints of crossbite, open bite and severe crowding (Figs. 4–12). The intraoral examination showed a Class III molar relationship on both sides without mandibular functional shift. A crossbite of 15–25 was noted. The open bite in anterior was 3 mm and the overjet was 1.5 mm. The arch length discrepancy was 8 mm in the maxilla. The upper second incisors on both sides are in the lingual side. Her facial photographs before treatment show a concave profile with a significantly protrusive mandible and normal maxillary indicating Class III skeletal discrepancy. Therefore, combined surgical-orthodontic treatment was recommended. However, she declined any treatment plan involving surgery and insisted on the orthodontic treatment. Treatment with a standard edgewise appliance was initiated after extraction of two upper second premolars and two lower first premolars. In order to avoid the occlusion interference during buccal movement of upper teeth, the lower bite-plate was fitted. Class III elastic was also used to
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orthodontic waves 68 (2009) 80–87
Table 1 – The comparison of cephalometrics value before and after orthodontic treatment (n = 13, mean W S.D.). Pretreatment
SNA (8) SNB (8) ANB (8) SN-MP (8) Pg-NB (mm) A-RL1 (mm) A-RL2 (mm) B-RL2 (mm) Ar-Pg (mm) Co-A (mm) Co-Gn (mm) U1-SN (8) L1-MP (8) U1-L1 (8) U1-NA (8) U1-NA (mm) L1-NB (8) L1-NB (mm) OP-FH (8) Ls-E (mm) Li-E (mm) Li-H (mm) Cm-Sn-Ls (8) Ls-RL2 (mm) Li-RL2 (mm) A-Ls (mm)
Posttreatment
Difference
P-value
Mean
S.D.
Mean
S.D.
Mean
S.D.
80.2 82.2 2 36.5 1.2 54.5 63.8 65.5 114.7 84.8 121.3 108.8 84.3 125.5 34.3 9.7 23.4 6.5 12.3 1.4 3.4 4.3 89.3 86.9 87.8 30.9
1.7 1.6 0.7 3.2 1.3 8.9 6.8 6.2 9.8 5.9 8.7 4.7 7.8 5.9 8.5 4.3 6.1 2.5 3.1 2.5 2.7 1.4 3.5 8.6 9.2 4.1
80.1 81.9 1.8 36.7 0.9 54.7 63.7 65.2 115 84.9 121.1 106.7 75.9 137.2 32.1 7.4 13.3 1.3 12.5 1.9 0.1 1 92.3 85.3 83.3 29.4
1.9 1.8 0.9 3.4 1.4 8.6 7.1 5.5 10.1 5.4 8.3 3.4 6.6 5.8 4 4 4.6 0.9 3.3 1.3 1.7 0.9 6.1 8.3 8.5 2.7
0.1 0.3 0.2 0.2 0.3 0.2 0.1 0.3 0.3 0.1 0.2 2.1 8.4 11.7 2.2 2.3 10.1 5.2 0.2 0.5 3.3 3.3 3 1.6 4.5 1.5
1.1 1.2 0.5 2.6 1.2 5.7 6.4 4.5 7.4 4.3 7.1 2.6 5.2 3.5 6.5 4.1 5.3 1.3 3.8 1.5 1.1 0.8 3.7 6.8 7.8 2.5
NS: P 0.05. P < 0.05. ** P < 0.01. *
Fig. 4 – Pretreatment facial photographs: (A) frontal view and (B) lateral view.
NS NS NS NS NS NS NS NS NS NS NS * ** **
NS NS ** **
NS NS ** ** * * **
NS
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orthodontic waves 68 (2009) 80–87
Fig. 5 – Posttreatment facial photographs: (A) frontal view and (B) lateral view.
relieve crossbite. At the end of treatment, her profile improved to straight and the severe Class III molar relationship was changed to Class I. The reversed overjet and the severe upper crowding were corrected and normal overbite and overjet were established with a good interdigitation. The active treatment time for this patient was 26 months. Skeletal Class III tendency still existed with a negative ANB angle, however, the corrected occlusion was harmonious and stable.
5.
Discussion
A strict selection of cases is crucial for this study. All of the cases selected in the study have been diagnosed as skeletal
Class III malocclusions with the ages all above 17, which meant that the development has basically stopped. And so, the change of cephalometric radiograph could be mainly attributed to the extraction of premolars instead of the effect of bone growth and development [12,15]. For skeletal Class III patients, the orthognathic surgery has been demonstrated to modify the skeletal pattern in addition to producing dramatic facial profile changes [9]. But some patients in clinic do not readily accept surgery because of potential surgical complications or other reasons and seek an orthodontic solution. It is a challenge for orthodontic doctors. The decision to treat the severe skeletal Class III malocclusion by surgical means or nonsurgical-orthodontic approaches still lacks a clear consensus [9,22,23]. Kerr et al. indicated that when ANB angle was
Fig. 6 – Pretreatment intraoral photographs: (A) lateral view on the right side, (B) frontal view, (C) lateral view on the left side, (D) occlusal view of maxillary dentition, (E) occlusal view of mandibular dentition and (F) lateral view of the anterior teeth.
orthodontic waves 68 (2009) 80–87
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Fig. 7 – Posttreatment intraoral photographs: (A) lateral view on the right side, (B) frontal view, (C) lateral view on the left side, (D) occlusal view of maxillary dentition, (E) occlusal view of mandibular dentition and (F) lateral view of the anterior teeth.
under 38 and L1-MP angle was under 838, the surgicalorthodontic treatment should be used to achieve the successful result [22]. Zeng et al. reported that orthodontic doctors should consider the orthognathic surgery when ANB angle was under 48 and L1-MP angle was under 828 [23]. In the sample selection we choose the borderline skeletal Class III patients (ANB angle was from 38 to 08) and use the
orthodontic camouflage treatment to achieve the good results. Also only the arch length discrepancy in the upper arch was under 8 mm are we supposed to extract two upper premolars. Otherwise the reversed occlusion in the anterior teeth might be still present after treatment. Skeletal crossbite are sometimes accompanied with upper arch severe crowding, which might be caused by the constriction of over developed mandible or be related with some other bad oral habits. In our study two upper premolars were extracted to resolve the severe crowding in the maxilla, while two lower premolars were extracted to eliminate the mild crowding and decrease the lower arch. The results of the clinical study indicated that the extraction of teeth affected little on skeletal parameters and there were no statistical significance observed (P 0.05). The change of ANB angle was not obvious with the value still negative, which proved that orthodontic treatment to skeletal Class III cases with extraction method had camouflage effects and surgical-orthodontic
Fig. 8 – Pretreatment panoramic radiograph.
Fig. 9 – Posttreatment panoramic radiograph.
Fig. 10 – Pretreatment lateral cephalometric radiograph.
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orthodontic waves 68 (2009) 80–87
Fig. 11 – Posttreatment lateral cephalometric radiograph.
treatment should be suggested for severe skeletal Class III cases to achieve a good effect. The change of lower teeth was significant with several items changed significantly on statistics (P < 0.01). The spaces by extraction of upper premolars were mainly occupied by relieving of severe crowding and the forward movement of upper molars. Also extraction of upper premolars might induce some mild changes of upper anterior teeth. It was found that the upper anterior teeth crown slightly inclined lingually but the change
Fig. 12 – Superimposition of pretreatment and posttreatment cephalometric tracings.
was not significant in appearance with U1-SN angle decreased by 2.18 (P < 0.05). The improvement of soft tissue profile was obvious with the concave profile before treatment transformed to straight profile after treatment. Pellegrino [13] and Fukui [14] separately reported a skeletal crossbite case with upper and lower arches severe crowding. Both of the patients were treated by extracting four premolars. The overjet and overbite became normal after treatment. Good occlusal relationship was achieved and the profile was turned to straight. Our results of cephalometric radiographs were consistent with their study. The mostly used extraction methods in the treatment of skeletal Class III malocclusions are the different ways. First, the only extraction of two lower second molars is one of the ways. According to the study of Lin [9,10], the indications to extract two lower second molars include severe skeletal Class III malocclusion, a mesial relationship of first molars and a well-arranged arch or only a minor crowding of lower arch. The author suggested that the extraction of two lower second molars was better than that of premolars. In this way the Class I molar and canine relationship could be established and the interlock canines relationship was helpful to retain a stable treatment effect. However, a strict indication should be conformed because the position of the third molars should be considered. The mean treatment time was comparatively longer about 2.6 0.6 years. Second, extraction of two lower premolars to treat skeletal Class III patients. Lew [12] made a clinical study with extraction of two lower first premolars to treat 38 adult skeletal crossbite cases. After the treatment, the lower incisors retracted by 6.4 mm (P < 0.001) and the lower lip retracted by 4.4 mm (P < 0.01). The upper teeth were inclined labially and well arranged with a result of upper incisor moving forward by 1.7 mm (P < 0.05) and upper lip moving forward by 1.2 mm (P < 0.05). A Class III molar relationship was established with a normal range of overjet and overbite and the facial profile was improved significantly. The treatment lasted 1.7 0.6 years averagely. Third, extraction of one lower incisor is sometimes adopted in terms of mild Class III malocclusions. This method is noted for a shorter treatment phase but usually causes a midline deviation. Fourth, skeletal crossbite cases with upper arch severe crowding could be solved by the method of extraction of one premolar from each quadrant. According to our study, it was indicated that the Class I molar relationship could be established and all the patients finished with favorable occlusion and a tendency to a straight profile. The mean treatment period was 2.1 0.4 years and shorter than that with extraction of two lower second molars. However, we should use slight and continuous forces when contract the lower anterior teeth backward to avoid the teeth inclined lingually and root resorption. Also the upper arch length discrepancy should be carefully analyzed before extraction of two upper premolars. Some scholars [12] argued that the Class III elastic may cause over eruption of upper molars and increase the mandibular plane angle. So it was not suitable for longface-type patients. The Class III elastic was also not recommended for adults, because it had a distalizing effect on the mandibular condyles, which may cause posterior displacement of the condyles, thereby impinging on the nonloadbearing retrodiscal tissues and leading to possible tempor-
orthodontic waves 68 (2009) 80–87
omandibular joint pain [24,25]. But this possibility has not been confirmed yet. And some other scholars argued that if the bruxism and disorder of TMJ could be excluded, they believe there was few chance for the damage of TMJ [26]. In our study the Class III elastic was used in latter phase of treatment to help finish the process and the results indicated that there was no significant change of mandibular plane angle and no TMJ disorder observed. So the influence of the Class III elastic on TMJ might be little and should be further investigated.
6.
Conclusions
The orthodontic camouflage by extraction of four premolars provides a viable treatment alternative for borderline skeletal Class III cases (especially combined with severe crowding in the upper arch) to achieve satisfying occlusal relationship and improve facial esthetics. However, for some severe skeletal Class III cases, the surgical-orthodontic treatment should be strongly recommended for more stable outcome.
Acknowledgement We thank Dr Juan Dai and Dr Junjie Wu for helpful discussions and criticism on this manuscript prior to resubmission.
references
[1] Yu HS, Baik HS, Sung SJ, Kim KD, Cho YS. Threedimensional finite-element analysis of maxillary protraction with and without rapid palatal expansion. Eur J Orthod 2007;29(2):118–25. [2] Guyer EC, Ellis 3rd EE, McNamara Jr JA, Behrents RG. Components of Class III malocclusion in juveniles and adolescents. Angle Orthod 1986;56(1):7–30. [3] Dietrich UC. Morphological variability of skeletal Class 3 relationships as revealed by cephalometric analysis. Rep Congr Eur Orthod Soc 1970;131–43. [4] Cha KS. Skeletal changes of maxillary protraction in patients exhibiting skeletal Class III malocclusion: a comparison of three skeletal maturation groups. Angle Orthod 2003;73(1):26–35. [5] Duan YZ, Yang ZH, Leng J. Effects of face mask/Class III elastic therapy on severe skeletal crossbite. J Modern Stomatol 2003;17(3):251–2. [6] Gu Y, Rabie AB, Hagg U. Treatment effects of simple fixed appliance and reverse headgear in correction of anterior crossbites. Am J Orthod Dentofacial Orthop 2000;117(6):691–9. [7] Uner O, Yuksel S, Ucuncu N. Long-term evaluation after chincap treatment. Eur J Orthod 1995;17(2):135–41.
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[8] Tollaro I, Baccetti T, Franchi L. Craniofacial changes induced by early functional treatment of Class III malocclusion. Am J Orthod Dentofacial Orthop 1996;109(3):310–8. [9] Lin JX, Gu Y. Lower second molar extraction in correction of severe skeletal Class III malocclusion. Angle Orthod 2006;76(2):217–25. [10] Lin JX, Gu Y. Preliminary investigation of nonsurgical treatment of severe skeletal Class III malocclusion in the permanent dentition. Angle Orthod 2003;73(4):401–10. [11] Richardson ME, Richardson A. Lower third molar development subsequent to second molar extraction. Am J Orthod Dentofacial Orthod 1993;104(6):566–74. [12] Lew KK. Soft tissue profile changes following orthodontic treatment of Chinese adults with Class III malocclusion. Int J Adult Orthodon Orthognath Surg 1990;5(1):59–65. [13] Pellegrino G. Italian Board of Orthodontics: case N. 2 adult malocclusion. Prog Orthod 2005;6(1):102–12. [14] Fukui T, Tsuruta M. Invisible treatment of a Class III female adult patient with severe crowding and crossbite. J Orthod 2002;29(4):267–75. [15] Demir A, Uysal T, Sari Z, Basciftci FA. Effects of camouflage treatment on dentofacial structures in Class II division 1 mandibular retrognathic patients. Eur J Orthod 2005;27(5):524–31. [16] Rodesano AJ. Treatment of Class III malocclusion with the Begg light-wire technique. Am J Orthod 1974;65(3):237–45. [17] Rodesano AJ. Incisor movement in Class III malocclusion treated with the Begg light wire technique. Am J Orthod 1971;60(4):355–67. [18] Lin JX, Huang JF, Zeng XL. A cephalometric evaluation of hard and soft tissue changes during Class III traction. Eur J Orthod 1985;7(3):201–4. [19] Xu TM, Lin JX, Kui H, Huang JF. Bite-opening mechanics as applied in the Begg Technique. Br J Orthod 1994;21(2):189– 95. [20] Xu TM, Lin JX, Huang JF, Cai P, Tan QF. Effect of the vertical force component of Class II elastics on the anterior intrusive force of maxillary archwire. Eur J Orthod 1992;14(4):280–4. [21] Nalbantgil D, Arun T, Sayinsu K, Fulya I. Skeletal, dental and soft-tissue changes induced by the Jasper Jumper appliance in late adolescence. Angle Orthod 2005;75(3):426– 36. [22] Kerr WJ, Miller S, Dawber JE. Class III malocclusion: surgery or orthodontics? Br J Orthod 1992;19(1):21–4. [23] Zeng XL, Lin JX, Huang JF. Skeletal crossbite: surgery or orthodontics? West Chin J Stomatol 1985;(3):233–7. [24] Owen 3rd AH. Orthodontic/orthopedic treatment of craniomandibular pain dysfunction. Part 2. Posterior condylar displacement. J Craniomandibular Pract 1984;2(4):333–49. [25] Ferro A, Nucci LP, Ferro F, Gallo C. Long-term stability of skeletal Class III patients treated with splints, Class III elastics, and chincap. Am J Orthod Dentofacial Orthop 2003;123(4):423–34. [26] Lin Z, Duan YZ, Din Y. Therapeutics of Orthodontics. Xi’an World Book Press Corporation; 2002. p. 224.
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/odw
Research paper
Camouflage treatment in skeletal Class III cases combined with severe crowding by extraction of four premolars Fang Ning, Yinzhong Duan *, Na Huo Department of Orthodontics, School of Stomatology, The Fourth Military Medical University, No. 145 West Changle Road, Xi’an 710032, PR China
article info
abstract
Article history:
Purpose: To evaluate the changes in dentoskeletal structures and profile after extraction of
Received 4 July 2008
four premolars in adult skeletal Class III borderline cases.
Received in revised form
Subjects and methods: Thirteen Chinese patients (mean age was 22.0 4.5 years) with
14 January 2009
skeletal Class III malocclusions and severe crowding in the upper arch were included in
Accepted 21 January 2009
the study. These cases were diagnosed to be in the borderline surgical-orthodontic range but
Published on line 23 February 2009
refused surgical treatments. All of them were treated by extraction of four premolars and standard edgewise technique. Lateral cephalometric radiographs taken at the start and end
Keywords:
of treatment were analysed. Twenty-six cephalometric variables were calculated and paired
Adult
t-tests were performed to assess the statistical significance of the treatment effects.
Skeletal Class III
Results: No significant changes were noted in the skeletal parameters (P 0.05). Regarding
Crowding
the dental parameters, the L1-MP angle decreased by 8.48, the U1-L1 angle increased by 11.78
Extraction
(P < 0.01), the L1-NB angle decreased by 10.18 and the L1-NB distance decreased by 5.2 mm (P < 0.01). The soft tissue parameters of Li-E, Li-H and Li-RL2 distance decreased by 3.3 mm, 3.3 mm and 4.5 mm, respectively (P < 0.01). All the patients finished with favorable occlusion and a straight profile. Conclusions: The orthodontic camouflage by extraction of four premolars provides a viable treatment alternative for borderline skeletal Class III cases to achieve satisfying occlusal relationship and improve facial esthetics. # 2009 Elsevier Ltd and the Japanese Orthodontic Society. All rights reserved.
1.
Introduction
Skeletal Class III is one of the most common malocclusions in orthodontic clinics in China, which can be corrected by either orthopedic, camouflage orthodontic, or combined surgicalorthodontic treatment. Different treatment approaches depends on the age of the patient, the pattern of malocclusion, its severity and patient’s request [1]. Studies have reported
that skeletal Class III discrepancy worsens with age [2,3]. Early intervention of skeletal Class III deformities in the mixed dentition or even in the deciduous dentition has received increasing attention in the orthodontic field. The alternative approaches include the use of reverse headgears, chin cups and functional appliances [4–8]. As for adult skeletal Class III patients, surgical-orthodontic therapy is often the recommended choice because it achieves a satisfying result, and the
* Corresponding author. Tel.: +86 29 84776138; fax: +86 29 83223047. E-mail address: [email protected] (F. Ning). 1344-0241/$ – see front matter # 2009 Elsevier Ltd and the Japanese Orthodontic Society. All rights reserved. doi:10.1016/j.odw.2009.01.004
orthodontic waves 68 (2009) 80–87
outcomes tend to be stable. However, sometimes, patients, especially borderline cases do not readily accept surgery because of the potential risk. Could orthodontic camouflage treatment work well in these cases? It provides a big challenge for orthodontists to satisfy individual’s request. Camouflage treatment can be carried out by different tooth extraction mode including lower second molars or premolars. Lin [9,10] successfully treated 13 severe skeletal Class III cases with tipe-edge technique and extraction of bilateral lower second molars. After treatment, the remarkable soft tissue change was noted and concave facial profiles improved to straight profiles. However, second molars extraction should be carefully selected, because the third molars do not always make satisfactory replacements for the lower second molars [11]. Lew [12] evaluated profile changes after extracting only two lower first premolars in Class III adults and considered this approach appeared to be a viable alternative in mild-tomoderate Class III patients who decline orthognathic surgery. Skeletal Class III cases sometimes accompany with severe crowding in the upper arch, which might due to the constriction of dental arches or some bad oral habits, such as tongue thrusting, sucking fingers, etc. However, few systemic studies ever reported the effects of camouflage treatment in such borderline skeletal Class III patients except few case reports [13,14]. Therefore, the aims of this retrospective study were to determine the changes in dentoskeletal structures and profile of adult Class III patients with severe crowding in upper dentition by extraction of four premolars and standard edgewise technique.
2.
Subjects and methods
2.1.
Subjects
81
each quadrant was extracted. Class III elastics were used in some cases where required. The mean duration of treatment was 2.1 0.4 years. The study protocol was approved by the Ethics Committee of the Fourth Military Medical University. The main idea in the treatment was extracting four premolars to relieve the upper arch crowding and to decrease the lower arch. We should be cautious to extract the upper premolars to avoid the reversed overjet after treatment. With extraction of two lower premolars in the mandible, there was much backward movement of the lower teeth. This contributed to correct the anterior crossbite and achieve Class I molar relationship [16–20].
2.2.
Cephalometric analysis
Standardized lateral cephalometric radiographs of each patient were obtained at the start and end of treatment. Each radiograph used in the present study were taken in the same cephalostat and traced on acetate paper. Twenty-six cephalometric landmarks (Figs. 1–3) were identified [12,15,21]. All the tracings and measurements were manually carried out twice with a 2-week interval by one examiner with a sharp pencil under optimal conditions. The method error in locating, superimposing and measuring the changes of different landmarksqffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi was ffi calculated by the Dahlberg’s formula P 2 Me ¼ d =2n, where d represents the difference between two registrations and n is the number of duplicate registrations. The method error determined was 0.3 mm for linear measurement and 0.4o for angular measurement, which were both statistically insignificant (P 0.05).
Five male and eight female consecutive patients (mean age: 22.0 4.5 years) were included in this study. All of these cases were treated with an orthodontic camouflage approach and had undergone the treatment at the Department of Orthodontics, School of stomatology, Fourth Military Medical University during the period from 2002 to 2008. Criteria for selection of subjects were as follows: (1) The molar relationships were between half- to full-unit Class III; (2) Anterior crossbite; (3) Concave facial profile; (4) 38 < ANB < 08; (5) No mandibular shift due to occlusal interference or premature contact of teeth; (6) No congenitally missing teeth (excluding third molars); (7) Severe crowding in the upper arches (arch length discrepancy <8 mm); (8) Patients and their families intensely rejected surgery; (9) Adult patients (ages 17 years) [15]; (10) No subjects had undergone orthodontic therapy of any type prior to this treatment. All patients were treated with the standard edgewise technique. In these cases, either the first or second premolar in
Fig. 1 – Skeletal measurements used in the study SN indicates Sella-nasion plane; RL1, horizontal reference line; RL2, vertical reference line; 1. SNA, 2. SNB, 3. ANB, 4. SN-MP, 5. Pg-NB, 6. A-RL1, 7. A-RL2, 8. B-RL2, 9. Ar-Pg, 10. Co-A and 11. Co-Gn.
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2.3.
Statistical analysis
The statistical analysis was processed with SPSS 10.0 for Windows. The arithmetic mean and standard deviation were calculated for each variable. Paired t-tests were performed to assess the statistical significance of any dental and skeletal change. The levels of significance were: P 0.05 (NS), *P < 0.05; **P < 0.01.
3.
Results
At the end of the treatment, the anterior crossbite was corrected and Class I molar and canine relationships were achieved in all subjects. The facial profile was improved dramatically from a concave to a straight profile.
3.1.
Skeletal changes
No significant anteroposterior or vertical skeletal changes were identified during treatment (P 0.05).
3.2. Fig. 2 – Dental measurements used in the study SN indicates Sella-nasion plane; RL1, horizontal reference line; RL2, vertical reference line; 1. U1-SN, 2. L1-MP, 3. U1L1, 4. U1-NA (degree), 5. U1-NA (mm), 6. L1-NB (degree), 7. L1-NB (mm) and 8. OP-FH.
Dental changes
According to the pretreatment and posttreatment comparisons, statistically significant differences were noted in five dental measurements. L1-MP angle decreased by 8.48, U1-L1 angle increased by 11.78, L1-NB angle decreased by 10.18 and L1-NB distance decreased by 5.2 mm (P < 0.01). U1-SN decreased by 2.18 (P < 0.05) (Table 1).
3.3.
Soft tissue changes
After treatment, the results were statistically significant with Cm-Sn-Ls increased by 38 and Ls-RL2 distance decreased by 1.6 mm (P < 0.05), also Li-E distance decreased by 3.3 mm, Li-H distance decreased by 3.3 mm and Li-RL2 distance decreased by 4.5 mm (P < 0.01) (Table 1).
4.
Fig. 3 – Soft tissue measurements used in the study SN indicates Sella-nasion plane; RL1, horizontal reference line; RL2, vertical reference line; 1. Upper lip to E plane, 2. Lower lip to E plane, 3. Lower lip to H line, 4. Cm-Sn-Ls, 5. Ls-RL2, 6. Li-RL2 and 7. A-Ls.
Case report
A woman aged 18 years with chief complaints of crossbite, open bite and severe crowding (Figs. 4–12). The intraoral examination showed a Class III molar relationship on both sides without mandibular functional shift. A crossbite of 15–25 was noted. The open bite in anterior was 3 mm and the overjet was 1.5 mm. The arch length discrepancy was 8 mm in the maxilla. The upper second incisors on both sides are in the lingual side. Her facial photographs before treatment show a concave profile with a significantly protrusive mandible and normal maxillary indicating Class III skeletal discrepancy. Therefore, combined surgical-orthodontic treatment was recommended. However, she declined any treatment plan involving surgery and insisted on the orthodontic treatment. Treatment with a standard edgewise appliance was initiated after extraction of two upper second premolars and two lower first premolars. In order to avoid the occlusion interference during buccal movement of upper teeth, the lower bite-plate was fitted. Class III elastic was also used to
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Table 1 – The comparison of cephalometrics value before and after orthodontic treatment (n = 13, mean W S.D.). Pretreatment
SNA (8) SNB (8) ANB (8) SN-MP (8) Pg-NB (mm) A-RL1 (mm) A-RL2 (mm) B-RL2 (mm) Ar-Pg (mm) Co-A (mm) Co-Gn (mm) U1-SN (8) L1-MP (8) U1-L1 (8) U1-NA (8) U1-NA (mm) L1-NB (8) L1-NB (mm) OP-FH (8) Ls-E (mm) Li-E (mm) Li-H (mm) Cm-Sn-Ls (8) Ls-RL2 (mm) Li-RL2 (mm) A-Ls (mm)
Posttreatment
Difference
P-value
Mean
S.D.
Mean
S.D.
Mean
S.D.
80.2 82.2 2 36.5 1.2 54.5 63.8 65.5 114.7 84.8 121.3 108.8 84.3 125.5 34.3 9.7 23.4 6.5 12.3 1.4 3.4 4.3 89.3 86.9 87.8 30.9
1.7 1.6 0.7 3.2 1.3 8.9 6.8 6.2 9.8 5.9 8.7 4.7 7.8 5.9 8.5 4.3 6.1 2.5 3.1 2.5 2.7 1.4 3.5 8.6 9.2 4.1
80.1 81.9 1.8 36.7 0.9 54.7 63.7 65.2 115 84.9 121.1 106.7 75.9 137.2 32.1 7.4 13.3 1.3 12.5 1.9 0.1 1 92.3 85.3 83.3 29.4
1.9 1.8 0.9 3.4 1.4 8.6 7.1 5.5 10.1 5.4 8.3 3.4 6.6 5.8 4 4 4.6 0.9 3.3 1.3 1.7 0.9 6.1 8.3 8.5 2.7
0.1 0.3 0.2 0.2 0.3 0.2 0.1 0.3 0.3 0.1 0.2 2.1 8.4 11.7 2.2 2.3 10.1 5.2 0.2 0.5 3.3 3.3 3 1.6 4.5 1.5
1.1 1.2 0.5 2.6 1.2 5.7 6.4 4.5 7.4 4.3 7.1 2.6 5.2 3.5 6.5 4.1 5.3 1.3 3.8 1.5 1.1 0.8 3.7 6.8 7.8 2.5
NS: P 0.05. P < 0.05. ** P < 0.01. *
Fig. 4 – Pretreatment facial photographs: (A) frontal view and (B) lateral view.
NS NS NS NS NS NS NS NS NS NS NS * ** **
NS NS ** **
NS NS ** ** * * **
NS
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Fig. 5 – Posttreatment facial photographs: (A) frontal view and (B) lateral view.
relieve crossbite. At the end of treatment, her profile improved to straight and the severe Class III molar relationship was changed to Class I. The reversed overjet and the severe upper crowding were corrected and normal overbite and overjet were established with a good interdigitation. The active treatment time for this patient was 26 months. Skeletal Class III tendency still existed with a negative ANB angle, however, the corrected occlusion was harmonious and stable.
5.
Discussion
A strict selection of cases is crucial for this study. All of the cases selected in the study have been diagnosed as skeletal
Class III malocclusions with the ages all above 17, which meant that the development has basically stopped. And so, the change of cephalometric radiograph could be mainly attributed to the extraction of premolars instead of the effect of bone growth and development [12,15]. For skeletal Class III patients, the orthognathic surgery has been demonstrated to modify the skeletal pattern in addition to producing dramatic facial profile changes [9]. But some patients in clinic do not readily accept surgery because of potential surgical complications or other reasons and seek an orthodontic solution. It is a challenge for orthodontic doctors. The decision to treat the severe skeletal Class III malocclusion by surgical means or nonsurgical-orthodontic approaches still lacks a clear consensus [9,22,23]. Kerr et al. indicated that when ANB angle was
Fig. 6 – Pretreatment intraoral photographs: (A) lateral view on the right side, (B) frontal view, (C) lateral view on the left side, (D) occlusal view of maxillary dentition, (E) occlusal view of mandibular dentition and (F) lateral view of the anterior teeth.
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Fig. 7 – Posttreatment intraoral photographs: (A) lateral view on the right side, (B) frontal view, (C) lateral view on the left side, (D) occlusal view of maxillary dentition, (E) occlusal view of mandibular dentition and (F) lateral view of the anterior teeth.
under 38 and L1-MP angle was under 838, the surgicalorthodontic treatment should be used to achieve the successful result [22]. Zeng et al. reported that orthodontic doctors should consider the orthognathic surgery when ANB angle was under 48 and L1-MP angle was under 828 [23]. In the sample selection we choose the borderline skeletal Class III patients (ANB angle was from 38 to 08) and use the
orthodontic camouflage treatment to achieve the good results. Also only the arch length discrepancy in the upper arch was under 8 mm are we supposed to extract two upper premolars. Otherwise the reversed occlusion in the anterior teeth might be still present after treatment. Skeletal crossbite are sometimes accompanied with upper arch severe crowding, which might be caused by the constriction of over developed mandible or be related with some other bad oral habits. In our study two upper premolars were extracted to resolve the severe crowding in the maxilla, while two lower premolars were extracted to eliminate the mild crowding and decrease the lower arch. The results of the clinical study indicated that the extraction of teeth affected little on skeletal parameters and there were no statistical significance observed (P 0.05). The change of ANB angle was not obvious with the value still negative, which proved that orthodontic treatment to skeletal Class III cases with extraction method had camouflage effects and surgical-orthodontic
Fig. 8 – Pretreatment panoramic radiograph.
Fig. 9 – Posttreatment panoramic radiograph.
Fig. 10 – Pretreatment lateral cephalometric radiograph.
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Fig. 11 – Posttreatment lateral cephalometric radiograph.
treatment should be suggested for severe skeletal Class III cases to achieve a good effect. The change of lower teeth was significant with several items changed significantly on statistics (P < 0.01). The spaces by extraction of upper premolars were mainly occupied by relieving of severe crowding and the forward movement of upper molars. Also extraction of upper premolars might induce some mild changes of upper anterior teeth. It was found that the upper anterior teeth crown slightly inclined lingually but the change
Fig. 12 – Superimposition of pretreatment and posttreatment cephalometric tracings.
was not significant in appearance with U1-SN angle decreased by 2.18 (P < 0.05). The improvement of soft tissue profile was obvious with the concave profile before treatment transformed to straight profile after treatment. Pellegrino [13] and Fukui [14] separately reported a skeletal crossbite case with upper and lower arches severe crowding. Both of the patients were treated by extracting four premolars. The overjet and overbite became normal after treatment. Good occlusal relationship was achieved and the profile was turned to straight. Our results of cephalometric radiographs were consistent with their study. The mostly used extraction methods in the treatment of skeletal Class III malocclusions are the different ways. First, the only extraction of two lower second molars is one of the ways. According to the study of Lin [9,10], the indications to extract two lower second molars include severe skeletal Class III malocclusion, a mesial relationship of first molars and a well-arranged arch or only a minor crowding of lower arch. The author suggested that the extraction of two lower second molars was better than that of premolars. In this way the Class I molar and canine relationship could be established and the interlock canines relationship was helpful to retain a stable treatment effect. However, a strict indication should be conformed because the position of the third molars should be considered. The mean treatment time was comparatively longer about 2.6 0.6 years. Second, extraction of two lower premolars to treat skeletal Class III patients. Lew [12] made a clinical study with extraction of two lower first premolars to treat 38 adult skeletal crossbite cases. After the treatment, the lower incisors retracted by 6.4 mm (P < 0.001) and the lower lip retracted by 4.4 mm (P < 0.01). The upper teeth were inclined labially and well arranged with a result of upper incisor moving forward by 1.7 mm (P < 0.05) and upper lip moving forward by 1.2 mm (P < 0.05). A Class III molar relationship was established with a normal range of overjet and overbite and the facial profile was improved significantly. The treatment lasted 1.7 0.6 years averagely. Third, extraction of one lower incisor is sometimes adopted in terms of mild Class III malocclusions. This method is noted for a shorter treatment phase but usually causes a midline deviation. Fourth, skeletal crossbite cases with upper arch severe crowding could be solved by the method of extraction of one premolar from each quadrant. According to our study, it was indicated that the Class I molar relationship could be established and all the patients finished with favorable occlusion and a tendency to a straight profile. The mean treatment period was 2.1 0.4 years and shorter than that with extraction of two lower second molars. However, we should use slight and continuous forces when contract the lower anterior teeth backward to avoid the teeth inclined lingually and root resorption. Also the upper arch length discrepancy should be carefully analyzed before extraction of two upper premolars. Some scholars [12] argued that the Class III elastic may cause over eruption of upper molars and increase the mandibular plane angle. So it was not suitable for longface-type patients. The Class III elastic was also not recommended for adults, because it had a distalizing effect on the mandibular condyles, which may cause posterior displacement of the condyles, thereby impinging on the nonloadbearing retrodiscal tissues and leading to possible tempor-
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omandibular joint pain [24,25]. But this possibility has not been confirmed yet. And some other scholars argued that if the bruxism and disorder of TMJ could be excluded, they believe there was few chance for the damage of TMJ [26]. In our study the Class III elastic was used in latter phase of treatment to help finish the process and the results indicated that there was no significant change of mandibular plane angle and no TMJ disorder observed. So the influence of the Class III elastic on TMJ might be little and should be further investigated.
6.
Conclusions
The orthodontic camouflage by extraction of four premolars provides a viable treatment alternative for borderline skeletal Class III cases (especially combined with severe crowding in the upper arch) to achieve satisfying occlusal relationship and improve facial esthetics. However, for some severe skeletal Class III cases, the surgical-orthodontic treatment should be strongly recommended for more stable outcome.
Acknowledgement We thank Dr Juan Dai and Dr Junjie Wu for helpful discussions and criticism on this manuscript prior to resubmission.
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