Final answer:
The question inquires about the mesiodistal dimension of teeth surfaces, with the rule being that the mesiodistal width of the lingual side is usually greater than that of the facial side, except for canines and incisors. The correct answer to the question is (a) Canines and Incisors.
Step-by-step explanation:
Understanding Tooth Morphology and Eruption Patterns
When considering the morphology of human teeth, it's essential to understand how they are adapted to their functions. The question at hand relates to the mesiodistal (MD) width, which is the measurement from the middle (mesial) to the distant end (distal) of a tooth. Specifically, the question addresses the general rule that the lateral or mesiodistal dimension of facial surfaces (the side of the tooth facing the cheeks and lips) is less than that of the lingual surfaces (the side facing the tongue) for most teeth.
However, there are exceptions to this rule. When comparing specific types of teeth, we see that canines (cuspids) and incisors typically present the reverse of this rule. These teeth have a wider mesiodistal dimension on the facial surface than on the lingual surface. In contrast, other teeth like premolars (bicuspids) and molars tend to follow the general rule more closely, with the lingual dimension being broader than the facial dimension.
So, considering the options provided in the question (a) Canines and Incisors, (b) Molars and Premolars, (c) Anteriors and Posteriors, (d) Maxilla and Mandible, the correct answer is (a) Canines and Incisors. These are the two exceptions where the mesiodistal dimension is broader on the facial side than on the lingual side.
To reiterate, canines and incisors have pointed edges and sharp fronts, respectively, designed for tearing and cutting food. This functional necessity might be why their mesiodistal dimensions do not follow the typical pattern seen in other teeth categories. Canines are especially known for their prominent cusp which helps in piercing and tearing food, while incisors are characterized by their ability to make precise cuts due to their sharp edge.