Theory relates to a model in science because it presents the possible paradigms and patterns of the said concept and fact. It explains and elaborates the phenomenon of why it happened, how it happened and the factors that are involved in the process. A theory is a possible explanation of certain occurrence. 
In addition, any time a scientific theory is challenged, it means it's not a good theory. And this statement is not valid. In theoretical models, they are revisited when there are further studies and discoveries found in a certain area where they can be remodeled and reintegrated instead of disregarding its credibility. Models, theories, and paradigms are not challenged but rather encouraged, they are supported in many studies since these theories and models were created in order for us to understand a certain phenomenon but it would likely help the scientific society to be updated in the new forms or spheres of improvement rather than discouragement.  <span> </span>
        
             
        
        
        
Answer:
Mammalian dentition is characterized by heterodonty, in which both the upper and lower teeth are differentiated morphologically into four types: flat, chisel-shaped incisors, conical canines, bicuspid premolars and multicuspid molars in the mesiodistal direction.
Explanation:. 
- <u>The mesiodistal crown:</u>dimension is the smallest of any maxillary teeth.The mesiodistal measurement of the pulp chamber is wider compared to the labiopalatal one. The periphery of the socket often dips down palatally, labially, mesially and distally to accommodate the shape of the root. 
- <u>Maxillary central incisor:</u>The general shape is similar to maxillary central incisor except that they are shorter and narrower. It has the most cervically located contact area of any incisor. The mesioincisal and distoincisal angles are more rounded than the corresponding angles of maxillary central incisor.
- <u>Permanent mandibular central incisor:</u>The crown dimensions are the smallest of any tooth, it has bilaterally symmetrical crown, and the line angles are the sharpest of any tooth.It shows the shallowest labial developmental grooves, smoothest lingual surface contour and the least developed cingulum.
 
        
             
        
        
        
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