Year : 2007 | Volume
: 25 | Issue : 3 | Page : 130--132
The effect of anterior inclined plane treatment on the dentoskeletal of Class II division 1 patients
Meibodi Shahin Emami1, Abdolreza Jamilian1, Abdolrahman Showkatbakhsh2,
1 Department of Orthodontics, Islamic Azad University, Tehran, Iran
2 Department of Orthodontics, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Department of Orthodontics, Islamic Azad University, Tehran
Most of Class II malocclusions are due to underdeveloped mandible with increased overjet and overbite. Lack of incisal contact results in the extrusion of the upper and lower anterior dentoalveolar complex, which helps to lock the mandible and prevent its normal growth and development, and this abnormality is exaggerated by soft tissue imbalance. The purpose of this study was to evaluate the skeletal and dental changes in patients treated with anterior inclined plane appliance in growing patients with moderate Class II Division 1 having deep overbite. In this study, 25 patients, including 15 girls and 10 boys, with a mean age of 9 ±1.2 years were selected; all of them presented with moderate Class II deep bite with increased overjet and normal or horizontal growth pattern. Pre- and post-treatment X-rays and photos for an average of 8 months were taken. The statistical assessment of the data suggested that there were no significant changes in the vertical skeletal parameters. The mandibular incisors were protruded, whereas the maxillary incisors were retruded. Overbite and overjet were also reduced. There was significant increase in the mandibular length. The results revealed that in mixed dentition patients, the inclined plane corrected Class II discrepancies mostly through dentoskeletal changes.
|How to cite this article:|
Emami MS, Jamilian A, Showkatbakhsh A. The effect of anterior inclined plane treatment on the dentoskeletal of Class II division 1 patients.J Indian Soc Pedod Prev Dent 2007;25:130-132
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Emami MS, Jamilian A, Showkatbakhsh A. The effect of anterior inclined plane treatment on the dentoskeletal of Class II division 1 patients. J Indian Soc Pedod Prev Dent [serial online] 2007 [cited 2019 Dec 15 ];25:130-132
Available from: http://www.jisppd.com/text.asp?2007/25/3/130/36563
Functional appliances are used to correct the abnormal function that induces abnormal growth and development of the underlying hard tissues. Altering and directing the neuromuscular activity of the oral cavity to normal limits is the major goal of applying this method of the treatment. When there is mandibular retrognathia, positioning the mandible forward is believed to enhance its growth. ,,,, Previous studies have documented a significant increase in the mandibular length in comparison to the untreated controls.  The restraining effect of the functional appliances on maxillary growth has been reported to be of minor importance in improving maxillomandibular relationships in Class II Division 1 patients with deep overbite. ,,,,
The horizontal growth pattern of the retruded mandible with considerable overjet results in the loss of incisal contact, which might increase the antero-vertical dentoalveolar growth of the maxilla and the mandible. This phenomenon might act as mandibular growth barrier and the growth of the mandible will be restricted by the locking effect of abnormal occlusion. ,
The effect of functional appliances on masticatory muscle activity has been extensively reported in previous studies. Ahlgren  found no increase in the muscle activity during sleep, whereas an increased postural activity was detected in the masseter muscle during the day. Miralles et al .  found a significant increase in the muscle activity during the swallowing of saliva with these appliances.
Consequently, a review of the literature shows that functional appliances have favorable effects on dentoalveolar and skeletal structures. , Several types of functional appliances are currently used for treatment of Class II malocclusion. They aim at improving the existing skeletal imbalances, arch forms and orofacial functions.
The functional appliance is capable of altering the neuromuscular activity of the oral cavity; this leads to the normal growth induction combined with unlocking the mandible from the abnormal occlusion. However, due to the bulk of the appliance, the cooperation of the patient is a major concern due to restriction in oral physiological and functional activities. ,, In this study, a simple intramaxillary appliance was used in order to have free mandibular activity with the capability of altering the abnormal activity of the oral musculature system to achieve the same result as that of the functional appliance. The purpose of the present study is to investigate the influences of an anterior inclined plane on dentoskeletal changes.
Materials and Methods
The sample consisted of 25 subjects (15 females and 10 males) with a mean age of 9 ±1.2 years (range: 8-11 years of age). The patient inclusion criteria were: (1) Moderate skeletal and dental Class II malocclusion with deep overbite and underdeveloped mandible, (2) Moderate normal or low-angle growth pattern, (3) Early mixed dentition period, (4) An approximate overjet of 5 mm and (5) ANB > 4 degrees.
An anterior inclined plane was incorporated in the upper arch to decrease the overjet. The inclined plane is a removable appliance wherein during mouth closure; the mandible moves in the forward position [Figure 1].
The patients visited every four weeks and the study was carried out on 50 lateral cephalometric films, 25 of which were taken before the treatment and half of the remaining were taken at least 8 months after the treatment. The pretreatment and post treatment radiographs of each patient were traced on acetate paper at the same time by a single examiner to minimize any method errors. In order to assess the magnitude of the method error, 18 randomly selected cephalograms were traced and measured again by the same examiner after an interval of two weeks. The method error did not exceed 0.1 mm and 0.75° for the linear and angular measurements, respectively. The data were analyzed with descriptive statistics. The mean and standard deviations for the pretreatment, post-treatment and treatment changes were calculated. Paired t -test was used to evaluate the findings. Superimposition on the cranial base gives a general impression of the overall changes in facial pattern that have occurred with anterior inclined plane, which is illustrated in [Figure 2].
Statistical comparisons of the pretreatment and post-treatment data of the groups are shown in [Table 1]. The comparison of the cephalometric measurements revealed that the appliance had no skeletal effect on the maxilla. Increase in SNA was not statistically significant. The skeletal vertical parameters were evaluated and no significant change was found in SN-MP and Y axis.
When the measurements of the mandible were evaluated, significant changes were found. The ANB angle demonstrated a significant decrease when the two cephalograms were compared. Changes in Ar_B, Ar_Pog and SNB were significant, Ar-Pog distance increased 3.9 ± 4.3 mm, p p <0.01
The dental changes caused by the inclined plane were obvious. The upper incisors were significantly retroclined. On the other hand the lower incisors were proclined, although not significantly.
Literature review showed that there were no studies carried out regarding the anterior inclined plane application that overcomes many disadvantages of the conventional functional appliances. In this study, the results of treatment with this type of appliance are evaluated. The inclined plane is a removable intramaxillary appliance that forces the mandible to move in a forward position during the mandibular functional activity, particularly during the swallowing period. Protractor muscle involvement results in the intermittent activation of the retractor muscles that leads to favorable bone remodeling.
In comparison to the traditional functional appliances, this appliance does not restrict the three-dimensional mandibular movement nor it interferes with the regular physiological activity of the oral cavity, which has a great impact on the patient cooperation, and it requires less effort by the patient to follow oral hygiene instructions.
This method is more effective in early stages of Class II deep bite malocclusion treatment, particularly to redirect the mandibular growth anteriorly and vertically by eliminating the lack of occlusion that acts as a physical barrier against the normal growth of the mandible. This appliance prevents the further extrusion of the upper and lower anterior teeth because of the loss of anterior incisal contact. It provides a greater extrusion of the lower posterior teeth and this helps to correct the Class II relationship and opens the bite simultaneously in the early mixed dentition period.
The results showed that Class II correction was achieved mostly through dentoalveolar and skeletal changes of the mandible and revealed that the appliance had no effect on the nasomaxillary growth component.
Inclined plane favorably improved the profile. As the upper incisors retruded, the upper lip moved back and the lower lip was no longer trapped behind the upper incisors. Lip tension decreased favorably because of the upper incisor retrusion and mandibular protrusion.
This study demonstrated the skeletal and dental effects of the inclined plane in the early mixed dentition period. The results revealed that the appliance corrected the Class II discrepancies mostly through dentoskeletal changes of the mandible. As revealed by this study, it is recommended that, this treatment method might be an alternative to complicated functional appliances in the treatment of Class II malocclusion. This appliance has the advantages of allowing the mandibular lateral movements and normal physiological activity. Since it is a relatively smaller appliance, the patient cooperation is satisfactory. Further studies will be required to evaluate the long-term effects and stability of the appliance when it is used in Class II Division 1 malocclusion.
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