International Journal of Oral Health Sciences

ORIGINAL ARTICLE
Year
: 2018  |  Volume : 8  |  Issue : 2  |  Page : 99--103

Assessment of mandibular retrognathism and maxillary prognathism as contributory factors for skeletal Class II malocclusion: A cephalometric study


Suraj Prasad Sinha, Krishna U S Nayak, Crystal Runa Soans, PS Murali, Akhil Shetty, MS Ravi 
 Department of Orthodontics and Dentofacial Orthopaedics, A B Shetty Memorial Institute of Dental Sciences, Nitte University, Mangalore, Karnataka, India

Correspondence Address:
M S Ravi
Department of Orthodontics and Dentofacial Orthopaedics, A B Shetty Memorial Institute of Dental Sciences, NITTE - Deemed to be University, Mangalore, Karnataka
India

Abstract

Aim: The aim of this study is to evaluate the skeletal factor (maxillary excess and/or mandibular deficiency) contributing for the skeletal Class II malocclusion. Materials and Methods: Lateral cephalograms of 100 individuals (50 males and 50 females) in the age group of 18–30 years, having skeletal Class II malocclusion with ANB of more than 4, were evaluated. The parameters to be used for prediction of maxillary prognathism include linear measurement of Nasion perpendicular to point A, and for the mandibular retrognathism, it is linear measurement of Nasion perpendicular to Pogonion, as suggested by Burstone analysis. Results: The 34% of the studied sample size had the Class II skeletal pattern (ANB >4), but their observed values for the maxilla and the mandible (with respect to the cranium) were in the normal range according to Burstone's cephalometric norms. Mandibular retrognathism with 68% prevalence in the final studied sample size is the major contributory factor for the skeletal Class II malocclusion which is followed by maxillary prognathism with 27% prevalence in the studied sample size, and the last contributory factor is the combination of the above two which accounts for the 5% of the studied sample size. Conclusion: The cephalometric study of skeletal Class II participants suggests mandibular retrognathism to be the major component in the given sample size. The other important conclusion from this study is that the ANB angle is not a reliable indicator to assess the skeletal malocclusion.



How to cite this article:
Sinha SP, Nayak KU, Soans CR, Murali P S, Shetty A, Ravi M S. Assessment of mandibular retrognathism and maxillary prognathism as contributory factors for skeletal Class II malocclusion: A cephalometric study.Int J Oral Health Sci 2018;8:99-103


How to cite this URL:
Sinha SP, Nayak KU, Soans CR, Murali P S, Shetty A, Ravi M S. Assessment of mandibular retrognathism and maxillary prognathism as contributory factors for skeletal Class II malocclusion: A cephalometric study. Int J Oral Health Sci [serial online] 2018 [cited 2019 Aug 20 ];8:99-103
Available from: http://www.ijohsjournal.org/text.asp?2018/8/2/99/247803


Full Text



 Introduction



The analysis of maxillary and mandibular skeletal positions is essential in planning dentofacial orthopedic treatment or orthognathic surgery. The skeletal nature of a child's malocclusion may have a bearing on the choice of the appliance and the evaluation of the treatment result.[1] The dentoskeletal morphology of Class II malocclusion has been analyzed in some cephalometric investigations. The value of these studies is limited, mainly, by the following factors:

No clear definition of Class II malocclusion; the demarcation of Class II and Class I, especially in the mixed dentition, is vagueNo differentiation between Class II Division 1 and Class II Division 2 cases; such a differentiation is most important, as Division 2, participants may have a special craniofacial morphologyInsufficient sample size; this is especially true when evaluating Class II Division 2 malocclusions.[2]

Many treatment approaches are currently available to the orthodontist for alteration of the occlusal relationships of Class II malocclusions. Since specific therapeutic techniques affect craniofacial structures in different ways, the variety available should correspond to the variety of true etiologies.[3] Studies evaluating maxillary and mandibular skeletal and dental positions and vertical components of Class II individuals have reported conflicting results from both cross-sectional and longitudinal studies. No common results have been found regarding cranial base configurations.[4]

The angle classification of malocclusion was based on the occlusal relationship of the teeth. Angle chose the upper first permanent molar as the “key” to occlusion, and to his classification, the variable factor was the anteroposterior position of the lower first molar in its occlusal relation to the upper molar. The assumption of constancy of position of the first permanent molars relative to the jaws led to the further assumption that the manner of occlusal locking of these teeth determined the relative anteroposterior position of the maxilla and mandible. Therefore, in Class II cases, angle postulated a posterior positioning of the mandible, and in Class III cases, an anterior positioning of the mandible. With this, there gradually developed the theory that various malocclusions led to rather distinctive craniofacial patterns. This assumption, accepted by some and challenged by others, has led to extensive investigation involving attempts to reveal likenesses or dissimilarities in group of individuals selected on the basis of anteroposterior denture relationship.[5]

In orthodontic diagnosis and treatment planning, great importance has been attached to evaluating the sagittal apical base relationship. Both angular and linear measurements have been incorporated into various cephalometric analyses to help the clinician diagnose anteroposterior discrepancies and establish the most appropriate treatment plan. Although the ANB angle is still very popular and useful, it has been demonstrated in the literature that there is often a difference between the interpretation of this angle and the actual discrepancy between the apical bases.[6]

A skeletal Class II malocclusion may be the result of the prognathic maxilla, retrognathic mandible, and/or combination of both. It is very much essential to differentiate the exact contributing factor for Class II skeletal malocclusion as the orthopedic/orthognathic surgical treatment plan varies accordingly. Hence, this study is designed and planned to evaluate the skeletal factor (maxillary excess and/or mandibular deficiency) contributing for the skeletal Class II malocclusion.

 Materials and Methods



This retrospective study was conducted on 100 individuals (50 males and 50 females) in the age group of 18–30 years, who reported for their orthodontic/orthognathic surgical treatment.

This retrospective study was done on the local population.

Individuals having skeletal Class II malocclusion with ANB of more than 4 with no previous orthodontic, orthopedic, or surgical treatment, no craniofacial trauma, no congenital anomalies, and no neurologic disturbances were included in the study. Individuals who were not willing to be a part of the study, the individuals whose radiographs were not clear for interpretation, and the individuals with major illness or medical conditions were excluded from the study.

Only ANB was taken as the criteria, to check the reliability of ANB in diagnosing the skeletal malocclusion.

The lateral cephalograms used for the study were taken from the department archives. Digital lateral skull radiographs were taken with Planmeca ProMax (Planmeca Finland, Inc.). This radiographic system uses a charge-coupled device sensor chip as an image receptor. The exposure parameters for the digital cephalographs were 68 kV, 5 mA, and 18.7 s.

The lateral cephalograms were traced on 0.003'' acetate paper with 2H lead pencil. All tracings were done by the same operator to avoid interoperator errors. The parameters to be used for prediction of maxillary prognathism include linear measurement of Nasion perpendicular to point A [Figure 1], and for the mandibular retrognathism, it is linear measurement of Nasion perpendicular to Pogonion [Figure 2], as suggested by Burstone analysis.{Figure 1}{Figure 2}

Based on the expected prevalence of individuals with maxillary protrusion as 56%,[1] the sample size of 100 individuals was decided. The frequency was calculated from the sample size to get the prevalence percentage of the contributory factors.

 Results



Of 100 individuals, the lateral cephalogram of 21 individuals showed increased linear measurement of Nasion perpendicular to point A, suggestive of the prognathic maxilla. Decreased linear measurement of Nasion perpendicular to Pogonion was recorded in 48 individuals, suggestive of the retrognathic mandible. However, this includes those three individuals who had the combination discrepancy, i.e., prognathic maxilla and retrognathic mandible.

Interestingly, the 34% of the studied sample size had the Class II skeletal pattern (ANB >4), but their observed values for the maxilla and the mandible (with respect to the cranium) were in the normal range according to Burstone's cephalometric norms. Therefore, these individuals were not considered into the study. Hence, the final sample size of the study came to 66 in number.

Hence, mandibular retrognathism with 68% prevalence in the final studied sample size is the major contributory factor for the skeletal Class II malocclusion [Table 1] which is followed by maxillary prognathism with 27% prevalence in the studied sample size, and the last contributory factor is the combination of the above two which accounts for the 5% of the studied sample size.{Table 1}

The results showed that the average Nasion perpendicular to point A in the male group was 5.43 ± 0.98 mm with maxillary prognathism and −3.27 ± 3.15 mm with mandibular retrognathism as the causative factor for the skeletal Class II malocclusion, whereas in female, it was 3.41 ± 1.72 mm with maxillary prognathism and −3.61 ± 2.71 mm with mandibular retrognathism. Similarly, the average Nasion perpendicular to Pogonion for the male group came to be −2.14 ± 2.73 mm and −16.14 ± 4.42 mm with maxillary prognathism and mandibular retrognathism, respectively. Moreover, for female, it was −3.18 ± 4.12 mm and −17.26 ± 4.61 mm with maxillary prognathism and mandibular retrognathism, respectively. The female individuals with the combination of both the factors of maxillary prognathism and the mandibular retrognathism had the average Nasion perpendicular to point A as 3.5 ± 0.71 mm and the average Nasion perpendicular to Pogonion value as −15.00 ± 2.83 mm [Table 2].{Table 2}

 Discussion



The evaluation of the sagittal relationship of the maxilla and mandible is mandatory in planning dentofacial treatment or orthognathic surgery. Hence, the present study was done to evaluate the nature of skeletal Class II malocclusion. The result clearly shows that the skeletal Class II pattern was observed due to retrognathic mandible in 68% of the screened sample, 27% with the prognathic maxilla, and the remaining 5% of the population with the combination of both prognathic maxilla and retrognathic mandible.

The 34% of the studied cases depicted skeletal Class II relation (ANB >4) of the apical bases, but their maxilla and mandible were in the normal range according to Burstone's cephalometric norms. This shows that the ANB angle may not be a reliable indicator in determining the skeletal relationship. And hence, other cephalometric values should be considered and should be related clinically before coming to a final diagnosis.

The observed values of Nasion perpendicular to point A and Nasion perpendicular to Pogonion were compared with those of Burstone's cephalometric norms which say that the maxilla is normal (orthognathic), if the linear measurement of N perpendicular to A ranges from +3.7 mm to −3.7 mm for male and +1.7 mm to −5.7 mm for female and the mandible is normal (orthognathic) if the linear measurement of N perpendicular to Pogonion ranges from +4.2 mm to −12.8 mm for male and −1.4 mm to −11.6 mm for female. The maxilla was said to be prognathic if the observed values were more than +3.7 mm for male and +1.7 mm for female. In a similar manner, the mandible was considered retrognathic if the linear measurements were [1] McNamara,[3] and Hitchcock[7] who concluded that Class II Division 1 as a group had some dysplasia between the cranial base and the mandible.

However, the study by Rosenblum,[1] Blair Eugene,[5] and Altemus[8] found that the dominant pattern was maxillary protrusion with a normal mandible, which could be attributed to the fact that the parameters were measured using the Downs angle of convexity and the Kim anteroposterior dysplasia indicator in contrast to the Burstone's cephalometric norms.

The other contradictory study was done on 100 French participants by Amoric,[9] who analyzed McNamara's linear measurements for the maxilla and mandible and Ricketts facial axis. His results were more protrusive for point A and less retrusive for Pogonion than McNamara's. The reason for this difference could be because the sample group of Amoric was more horizontal growers than McNamara's, thus leading to less mandibular retrusion.

The result of this study varies with the literature related to the study which could be due to the ethnicity of the sample population, age group as well as the sample size.

The study signifies that majority of the skeletal Class II malocclusion in the studied sample is due to the mandibular retrognathism. The treatment of the skeletal malocclusion depends on the age of the patient; if these cases are detected early during the growth phase of life, then they can be managed with growth modulation appliances or else have to go for orthognathic surgery to achieve harmonious profile.

 Conclusion



The cephalometric study of skeletal Class II participants suggests mandibular retrognathism be the major component in the given sample size. The maxillary prognathism was the next major component leading to the skeletal Class II malocclusion, and the third component was the combination of the above two. The other important conclusion from this study is that the ANB angle is not a reliable indicator to assess the skeletal malocclusion. Further studies with bigger sample size and in the different ethnic group may be required to validate the results of the present study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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