Presence and Maturation Dynamics of Mandibular Third Molars and Their Influence on Late Mandibular Incisor Crowding: A Longitudinal Study.

Martina Zigante,Stjepan Spalj,Andrej Pavlic,Vaska Vandevska-Radunovic,Luka Morelato

doi:10.3390/ijerph181910070

Abstract

The objective of this study was to investigate the relationship between the absence, presence and dynamics of mandibular third molar development and the occurrence and amount of late mandibular incisor crowding. Dental plaster casts and panoramic radiographs of 72 orthodontically untreated subjects from the Nittedal growth study, Norway were analyzed. The subjects were recalled for a checkup at 12, 15, 18 and 21 years of age. Mandibular incisor crowding was assessed using Little’s irregularity index and dental maturation of the third molars by the Cameriere’s index. The majority of the subjects (64%) had ≥1 mm increase in irregularity; 22% experienced an increase of 0.1–0.9 mm and 14% had unchanged or decreased irregularity. Incisor irregularity increased with age, regardless of absence or presence of third molars. The amount of change in incisor irregularity from 12 to 21 years did not differ significantly between subjects with hypodontia of third molars, extraction and those with third molars present. No differences were observed between erupted, unerupted or impacted third molars. No correlation was found between the amount of change in irregularity and maturation of the third molars. In conclusion, occurrence and amount of mandibular late incisor crowding is not significantly influenced by the presence of mandibular third molars or their development dynamics.

Highlights

The relationship between third molars and mandibular incisor crowding is one of the most debated and studied fields in orthodontics, and despite all, is still quite controversial.Late crowding is considered to have multifactorial etiology, whereas etiological factors may differ between individuals
Mandibular incisor crowding is highly prevalent, as up to 40% of the general population has moderate to severe crowding [9]
This study aimed to investigate absence, presence and mandibular third molar development dynamics, i.e., rate; occurrence and amount of late mandibular incisor crowding and their possible interrelationship

Summary

Introduction

The relationship between third molars and mandibular incisor crowding is one of the most debated and studied fields in orthodontics, and despite all, is still quite controversial. Late crowding is considered to have multifactorial etiology, whereas etiological factors may differ between individuals. Many studies have attempted to clarify and evaluate the third molars and incisor crowding interrelationship [3,4,5,6,7,8]. They focused on third molar angulations, position, space, or their extraction, but none analyzed their maturation dynamics. Maxillary incisor crowding is one of the most frequent reasons for

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