Modified Angle's Classification for Primary Dentition.

AIM: This study aims to propose a modification of Angle's classification for primary dentition and to assess its applicability in children from Central India, Nagpur.
METHODS: Modification in Angle's classification has been proposed for application in primary dentition. Small roman numbers i/ii/iii are used for primary dentition notation to represent Angle's Class I/II/III molar relationships as in permanent dentition, respectively. To assess applicability of modified Angle's classification a cross-sectional preschool 2000 children population from central India; 3-6 years of age residing in Nagpur metropolitan city of Maharashtra state were selected randomly as per the inclusion and exclusion criteria.
RESULTS: Majority 93.35% children were found to have bilateral Class i followed by 2.5% bilateral Class ii and 0.2% bilateral half cusp Class iii molar relationships as per the modified Angle's classification for primary dentition. About 3.75% children had various combinations of Class ii relationships and 0.2% children were having Class iii subdivision relationship.
CONCLUSIONS: Modification of Angle's classification for application in primary dentition has been proposed. A cross-sectional investigation using new classification revealed various 6.25% Class ii and 0.4% Class iii molar relationships cases in preschool children population in a metropolitan city of Nagpur. Application of the modified Angle's classification to other population groups is warranted to validate its routine application in clinical pediatric dentistry.

Introduction

Angle[1] proposed a classification of occlusion based on the first permanent molars relationship. Since its introduction in 1899 Angle's classification has withstood testimony of time for over a century and almost two decades and is accepted as a gold standard of classifying malocclusions in contemporary clinical dental practice world over.

Review of the literature reveals that primary second molars terminal plane is mostly used to classify occlusion in primary dentition. However, if suitable modification of Angle's classification is proposed for application in primary dentition, then it will help in the diagnosis of developing malocclusion in primary dentition to be able to institute interceptive measures. Hence, modification of Angle's classification is proposed and an investigation was undertaken in preschool children of Nagpur to ascertain its applicability.

Methods

Healthy 2000 children irrespective of socioeconomic status having the full complement of primary dentition in the age range of 3–6 years were selected randomly. Children having any permanent tooth erupted, premature loss of primary tooth/teeth; proximal caries reducing arch length affecting molar relationship; history of pernicious oral habit or past orthodontic treatment and any dental and/or oral anomaly affecting occlusion were excluded from the study. Informed consent from the parents of children present on the day of the examination was obtained. The examination of children was done in sitting position in broad daylight after drying the arches with cotton and teeth in centric occlusion position.[2] Findings were recorded in the WHO[3] modified pro forma, especially designed for the study.

Modification of Angles criteria

Angle[1] used capital Roman numbers I/II/III to identify Class I, Class II, and Class III malocclusions, respectively. Janson et al.[4] have described half cusp Class II or III and Class II or III severity of malocclusions. In literature, the word end on, half cusp, cusp to cusp, and flush terminal plane (FTP) are used interchangeably. As the classification involves the description of cuspal relationships, we preferred term half cusp over other terms as clinically it can be observed, assessed, and checked with ease thereby help reduce interexaminer variability and increase intraexaminer reproducibility. In the modified Angle's classification for primary dentition, small Roman numbers i/ii/iii are used for the primary second molar relationship to represent Angle's Class I/II/III molar relationships as in permanent dentition, respectively. In addition to the Class i, ii, and iii molar relationships; half cusp Class ii, half cusp Class iii, and subdivision molar relationship are recorded as described below [Figures 1 and 2].

Figure 1

Primary second molar cuspal relationship – Occlusal view

Figure 2

Primary second molar cuspal relationship – Buccal view

Class i: When the mesiobuccal cusp of the primary maxillary second molar occludes with the mesiobuccal groove of the primary mandibular second molar

Class ii: When the mesiobuccal cusp of the primary maxillary second molar occludes with the interdental space between primary mandibular first and second molar

Class iii: When the mesiobuccal cusp of the primary maxillary second molar occludes with the distobuccal groove or distal surface of the primary mandibular second molar

Half cusp Class ii: When the mesiobuccal cusp of the primary maxillary second molar occludes with the mesiobuccal cusp of the primary mandibular second molar

Half cusp Class iii: When the mesiobuccal cusp of the primary maxillary second molar occludes with the distobuccal cusp of the primary mandibular second molar

Subdivision: When molar relationships on both sides in a child is different wherein one side is Class i and the other being any one of the other types described above. The subdivision is the side which is not Class i side.

Results

Distribution of the sample and prevalence of primary molar cuspal relationships according to proposed modified Angle's classification for primary dentition is shown in Tables 1 and 2, respectively. Maximum 93.35% children exhibited Bilateral Class i primary molar relationships followed by 2.5% bilateral Class ii and 0.2% children each had bilateral half cusp Class iii and a half cusp Class iii subdivision primary molar relationships. Nearly 3.75% children examined had various combinations of Class ii primary molar relationships such as Class ii subdivision, Class ii-half cusp Class ii, Half cusp Class ii subdivision and bilateral half cusp Class ii.

Table 1

Distribution of sample

Table 2

Prevalence of primary molar cuspal relationships

Age- and sex-wise distribution of various primary molar relationships as shown in Table 3 was found to be statistically insignificant. Since the number of children was smaller than 5 and even 0 in quite a few age- and sex-wise molar relationship groups; to evaluate the statistical significance the data of different age were pooled and two age groups, namely, ≤4 years and >4 years were formed [Table 4]. It is observed that the bilateral Class ii primary molar relationship children number was significantly higher (P < 0.0241) in more than 4 years children group (3.26%) as compared to children of ≤4 years (1.57%). Statistically, no significant sexual dimorphism was observed in primary molar cuspal relationships among two age groups children [Table 5].

Table 3

Age- and sex-wise distribution of primary molar cuspal relationships

Table 4

Age- group-wise comparison of primary molar cuspal relationships

Table 5

Sex-wise comparison of primary molar cuspal relationships

Discussion

Nagpur a metropolitan city in the state of Maharashtra having geographical coordinates 21° 9’ 0” North, 79° 6’ 0” East and is located in the center of the country having zero miles landmark. It is surrounded by three states and three national high ways number 6, 7, and 69 are passing through Nagpur. Marathi is the mother tongue of Maharashtra but people from other states speaking various other Indian languages and different religious faiths are also settled in this city apart from neighboring states of Madhya Pradesh, Chhattisgarh, and Telangana making Nagpur a cosmopolitan city. Only those children whose parents have been living in Nagpur for minimum one generation, i.e. born and brought up in Nagpur were selected for the study. Therefore, the children included in the study can be considered as representative of the central India.

As per the 2011 census of India, the population of Nagpur[5] was 24,05,665 and that of children below 6 years of age was 2,47,078. The sample for the cross-sectional epidemiological studies as per WHO[3] guidelines should be 0.1%–1% of the population of the study area and accordingly, the sample for below 6 years children population for Nagpur may comprise of 2471 children. Taking into account increase in the population from 2011 to 2016 and the age group for the present study being between 3 and 6 years; a total of 2000 children may be considered as a representative sample for this cross-sectional epidemiological study.

It is important that the pediatric dentist should identify normal and abnormal molar relationships to be able to institute interceptive orthodontic measures. About 93.35% preschool children in the present investigation were found to have normal bilateral Class i primary molar relationships. 2.5% bilateral Class ii children definitely need interceptive measures. Remaining 3.75 and 0.4% children having various combinations of Class ii and Class iii, primary molar relationships are the cases having unilateral Class i and/or transient unstable unilateral/bilateral half cusp Class ii or Class iii molar relationships may need supervision, monitoring, and depending on their transition into full cusp Class ii or Class iii molar relationships may need interceptive and/or corrective orthodontic measures.

The prevalence of bilateral Class ii molar relationship was seen to increase significantly in children more than 4 years of age. The 3.75% and 0.4% various combinations of Class ii and Class iii primary molar relationship children observed in this study may have the potential to undergo transition into Class II and Class III malocclusion in permanent dentition.

Infante[67] in two different studies has included both terminal plane and/or Angles molar relationship to classify the primary occlusal relationship, and therefore, the results of both his studies cannot be strictly compared with the present investigation. Trottman et al.[8] and Krishna et al.[9] have used Angle's molar relationship as such to classify the primary occlusion. Trottman A and Elsbach HG.[8] in their study observed white children having 78%, 14%, and 8% Class I, Class II, and Class III molar relationship respectively; whereas black children were found to have 76% Class I, 7% Class II, and 17% Class III molar relationships, respectively. Krishna et al.[9] observed 81.39% Class I, 15.35% Class II, and 3.26% Class III molar relationship in their study. The difference in the prevalence of the present investigation with these two studies may be related to factors, such as different study locations, sample selection criteria, and growth potential differences, and most importantly, the difference of modification in Angle's classification criteria of the present study with the above two studies.

The present pilot study had the objective of application of Angle's classification criteria in primary dentition. Majority of the investigations[10111213141516] have used the primary second molars terminal plane relationship to classify as the FTP or end on, mesial step, and distal step occlusion. However, few other investigators have used primary canine's relationship to classify the primary occlusion as Class 1, Class 2, and Class 3. Further studies are warranted to validate the utility of the new classification by correlating it with other assessment criteria such as the molar terminal plane and canine relationships and further with overjet, overbite, and spacing conditions observed in the primary dentition. The proposed modified Angle's classification for primary dentition may further be assessed in different population and geographic locations to ascertain its validity and clinical application thereof. Further longitudinal study is needed to determine whether the various primary second molar relationship as described in the article gets converted into corresponding or different first permanent molar relationship.

Conclusions

A modification of Angle's classification for application in primary dentition has been proposed, and an attempt is made to test its applicability in a cross-sectional preschool children population of Nagpur in the state of Maharashtra from central India. Maximum 93.35% children exhibited Bilateral Class i primary molar relationships.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.