Tuesday, October 10, 2017

Changes in the molar relationship between the deciduous and permanent dentition: a longitudinal study

Article Title: Changes in the molar relationship between the deciduous and permanent dentition: a longitudinal study
Author(s): Bishara SE; Hoppens BJ; Jakobsen JR; Kohout FJ
Journal: American Journal of Orthodontics and Dentofacial Orthopedics
Date: 1988; 93: 19-28
Major Topic: Molar relationships and their progression from the primary to mixed to permanent dentition
Type of Article:  Longitudinal study
Main Purpose: This article aimed to describe the changes in molar relationship from the primary to the permanent dentitions.
Key Points: The more favorable the molar relationship in the primary dentition, the more likely the patient will end up in class I.
·      ~50% of patients in primary dentition have a flush-terminal plane relationship
·      2 mechanisms for how a cusp-cusp relationship in the mixed dentition can result in a class I permanent dentition
o   Greater anterior growth of the mandible relative to the maxilla
o   Greater leeway space in mandibular arch compared to maxillary arch, which would allow for greater mesial migration of mandibular molars
·      Distal steps occlusions (10% of total population) ALL resulted in class II permanent dentition relationships
o   Once a class II, always a class II
o   2 cases resulted in class I due to premature loss of mandibular primary second molars due to caries
o   Distoocclusion in the primary or mixed dentition will not self-correct and the patient will need orthodontic treatment when indicated
Flush Terminal Relationship (29% of total population)
Class I
Class II
Class III

Mesial Step (1.0mm) Relationship (42% of total population)
Class I
Class II
Class III

Mesial Step (2mm or more) Relationship (19% of total population)
Class I
Class II
Class III

·      62% of patients ended class I; 34% ended with class II; 4% in class III
·      Comparisons of right and left sides demonstrated almost no difference between the two
·      Final occlusion is dependent on many dental and skeletal changes, both genetic and environmental, and leeway space is not a good predictor of final molar relationship
·      Mesial step primary dentition occlusion increases chance of having class I occlusion but the greater the mesial step the greater the chance of getting a class III occlusion

1-    I am not sure how to take the article because it took one patient and used them to get two different data sets by using their right and left sides. I think this may skew the results.
2-    Keeping male and female subjects separate in orthodontic studies?
Assessment of Article:  Level of Evidence/Comments: II-2

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