Orthodontics | Development of Occlusion | INBDE, ADAT

The video begins with an introduction to the orthodontics series, focusing on the development of occlusion through four stages. The first stage is the gum pad stage, which occurs from birth to six months, characterized by the absence of teeth and the presence of gum tissue pads. The video explains the features of this stage, such as the incisive papilla and transverse grooves that demarcate the development of tooth buds. The second stage is the primary dentition stage, ranging from six months to six years, during which the first primary tooth erupts until the first permanent tooth comes in. This stage is marked by minimal overbite and overjet, with spacing between primary incisors being necessary to prevent crowding of the larger permanent teeth. The concept of incisor liability is introduced, highlighting the size difference between primary and permanent front teeth.

The second paragraph discusses the mixed dentition stage, which occurs from six to twelve years and involves the transition from primary to permanent dentition. This stage is characterized by the closure of interdental and leeway spaces, as well as the transition of molar relationships from the terminal plane to class 1, 2, or 3. The 'ugly duckling' stage, marked by a gap between the upper central incisors, is part of this period. The video also explains how the terminal plane relationship of the primary molars can predict the permanent molar relationship, and how the mesial step, flush terminal plane, and distal step relate to the eventual occlusion. The importance of understanding these relationships for orthodontic treatment planning is emphasized.

The third paragraph delves into the prediction of occlusion based on the primary molar relationships, with a focus on class 2 (disto-occlusion), class 1 (normal occlusion), and class 3 (mesio-occlusion). The video discusses the likelihood of each occlusion type based on the terminal plane relationship and how differential jaw growth and differential shift of teeth can change the occlusion from flush terminal plane to class 1 or class 3. The concept of early and late mesial shifts, and their impact on the occlusion, are explained. The importance of understanding these shifts for orthodontic diagnosis and treatment planning is highlighted.

The fourth paragraph introduces the concept of mixed dentition space analysis, which predicts the amount of crowding or spacing that will occur as permanent teeth erupt. The video explains two common methods for this analysis: the Tanaka-Johnston method and the Moyers method. Both methods involve measuring the width of the lower incisors and using either a mathematical equation or a prediction table to determine the space required for the maxillary and mandibular buccal segments. The video then discusses the permanent dentition stage, which begins at twelve years old and continues throughout life. It covers the ideal overbite, overjet, and occlusion for this stage, as well as the phenomenon of late lower incisor crowding, which can worsen with age due to lower lip pressure and mandibular growth.

The final paragraph discusses the changes in arch dimensions that occur during the transition from mixed to permanent dentition. It covers the increase in intercanine and intermolar width, the stabilization of these dimensions after the eruption of canines and molars, and the decrease in arch length and perimeter. The video explains how the upper arch tends to expand more than the lower arch due to the direction of tooth eruption and the curve of Wilson. The impact of leeway space on arch dimension changes is also discussed, with a net decrease in the lower arch perimeter and a slight increase in the upper arch perimeter. The video concludes with a review of the four stages of dentition development and encourages viewers to like, share, and subscribe for more dental education content.