The Development of the Dentition in Class II/1 Malocclusions
At the end of the last century, Dr. Edward H. Angle1 introduced a classification of sagittal (anteroposterior) relations between the mandibular and maxillary dental arches. This classification is internationally accepted and was named after its inventor. The Angle Classification is still used commonly today.
The normal sagittal relation between the two dental arches is indicated with the term Class I. A dorsal position of the mandibular dental arch in relation to the maxillary one is specified as a Class II malocclusion. A reversed situation, with the mandibular dental arch too much ventrally in relation to the maxillary one, is called a Class III malocclusion. The terms Class II and Class III leave undecided whether the deviating component is located in the mandible or in the maxilla or in a combination of both. Only the sagittal relation between the two dental arches is indicated. No judgment is passed on causal factors. Later, the sagittal relation between the bony parts of the lower and upper jaws was added to the Angle Classification.2 However, this aspect is not incorporated in this discussion nor in that of Class III malocclusions in Chapter 12.
Angle has further divided the Class II malocclusions into Class II division 1 (II/1) and Class II division 2 (II/2) malocclusions. In Class II/1 malocclusions, the maxillary incisors have a more or less normal labiolingual inclination or are too much protruded. In Class II/2 malocclusions, to be discussed separately in the next chapter, two or more maxillary incisors are tipped palatally. As the position of the lips is directly related to those of the incisors, a Class II/1 malocclusion may be associated with a lower lip situated between the mandibular and maxillary incisors. An adequate lip seal may not exist, particularly in children. In Class II/2 malocclusions, the lips are in contact with each other.
Sagittal deviations between the two dental arches, complicated by an asymmetry of the dental arch relation, have been labeled by Angle with the supplementary term subdivision. A Class II subdivision stands for a Class II dental arch relation on the one side and a Class I on the other side. The Class II/1 subdivision will not be dealt with here but will be treated together with the Class III subdivision in Chapter 14.
Abnormalities in the dental arches themselves, which may complicate a Class II/1 malocclusion, are not discussed in this chapter either. In principle, all abnormalities in the dental arches presented in chapter 9 can occur in Class I, Class II, and Class III conditions and may, as such, be thought of as superimposed on the sagittal dental arch relation.
In this discussion of Class II/1 malocclusions, basically normal conditions are assumed to be present in each dental arch. However, certain deviations in the location of maxillary and mandibular teeth are caused by the abnormal relation between the two dental arches. These deviations are exclusively the consequences of the abnormal sagittal relation and will be discussed in that context.
The Class II/1 malocclusions in the deciduous dentition (Fig. 10-1), in the intertransitional period (Fig. 10-2), and in the permanent dentition (Fig. 10-3) are described successively. In addition, the eruption of the first permanent molars and the transition of the incisors are treated (Figs. 10-4 and 10-5). Finally, the transition of the posterior teeth is discussed (Fig. 10-6).
Fig. 10-1 Survey of a Class II/1 malocclusion in the complete deciduous dentition (compare with Fig. 3-1).
A,B The mandibular dental arch is dorsally situated in relation to the maxillary one. A good transverse relation exists between the opposing deciduous molars. The transverse dimensions of the mandibular dental arch are normal; those of the maxillary are too small.
D In occlusion, the mandibular deciduous molars are positioned too far dorsally in relation to the maxillary ones. The terminal plane of the deciduous dentition exhibits a distal step.
Fig. 10-2 Survey of a Class II/1 malocclusion in the intertransitional period (compare with Fig. 5-1).
A,B Dorsal position of the mandibular dental arch in relation to the maxillary one, abnormally large overjet, and a normal transverse relation between the opposing posterior teeth. Relatively too narrow and too tapering maxillary dental arch.
C Increased overbite. The permanent incisors erupt until vertical support is obtained in habitual occlusion. The incisal edges of the mandibular incisors may touch the palate instead of the lingual surfaces of the opposing teeth.
D The mandibular first permanent molar occludes too far dorsally to the maxillary one. However, the opposing surfaces of both teeth are quite large, as is the intercuspating area.