Thursday, October 26, 2017

Available space for the incisors during dental development - A growth study based on physiologic age

Department of Pediatric Dentistry
                                                                  NYU Langone

Resident’s Name: Suhyun Rue                                                                   Date: 11/01/2017
Article Title:   Available space for the incisors during dental development - A growth study based on physiologic age
Author(s): Coenraad F. A. Moorrees, D.D.S. and Jagdish M. Chadha, B.D.S.
Journal: The Angle Orthodontist
Date: Jan. 1965
Major Topic: Spacing and crowding during incisor transition
Type of Article: Observational/investigative
Main Purpose: Investigate available space for the incisors of the growing child by grouping children at similar stages of dental maturation with reference to tooth eruption instead of chronological age
Key Points/Summary:
Methods: 78 maxillary and 70 mandibular study casts were used for studying the available space in the incisor segment. Each tooth in an individual series of dental casts was classified according to one out of six stages:  1. Deciduous tooth present  2. Extracted  3. Exfoliated  4. The permanent successor emerging 5. ½ of the crown erupted 6. Fully erupted.  The difference between each stage and the previous one in the series for each child was recorded, thus events occurring during specific eruption phases could be identified.
Findings: Emergence of mandibular central and lateral incisors resulted in 1.6mm crowding in males and 1.8mm crowding in females. In the maxilla either a small excess or a small (0.2mm) lack of space for the erupting permanent incisors was encountered. Increments in the inter-canine distance and in arch length during eruption of the lateral incisors provided enough space for the alignment of these teeth, except in the mandible where 0.2 and 0.5mm crowding was noted for males and females, respectively. No changes were noted during the emergence of the permanent canines. Pattern of change in the maxillary and mandibular dentitions of the sexes was similar. Females recover better than males from the loss of available space.
Key points:
·  Available space is dependent on tooth size so observing tooth emergence and eruption should provide a realistic account of the changes in available space.   Also, combining early and late maturing children in the same chronological age has been shown to hide the actual loss of space during the incisor transition.
· The changes in arch length and arch width are consistent with the pattern of change in available space for the incisor segment. Incisors are largely relieved when the crowns of the lateral incisors are fully erupted while if growth increments in arch size are also completed at that time.
· A slight increase in arch width occurs in the maxillary arch when the permanent canines erupt. Increase in arch length is confined to the maxillary arch and explains why emerging incisors have nearly sufficient space for their alignment as opposed to the mandibular incisors.
· At the end of the incisor transition the spaces between the deciduous canines and molars are closed. Mesial migration of the permanent first molars occupies most of the leeway space between the crown diameters of the deciduous posterior teeth and their permanent successors reflected in a reduced arch length.
· The level of dental maturation gives decisive clues for diagnosis and treatment planning since it defines the timetable of individual development. Chronologically based methods often mask the characteristic features that distinguish one child from the next. The sources of variance for available space of the incisors are tooth size and growth of the alveolar processes.
Assessment of Article:  Level of Evidence/Comments:  Level III

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