Which statement is true regarding the morphology of mandibular first permanent molars?

The statement that mandibular first permanent molars are the largest teeth in the lower arch is accurate, as these molars are specifically designed to handle the significant force required for mastication. Their large size aids in their primary function of grinding and breaking down food, making them crucial for efficient chewing. In addition to their size, they possess a complex tooth morphology with multiple cusps and grooves, which enhances their surface area for better occlusion with opposing teeth.

In contrast, other attributes such as the presence of an oblique ridge, the number of cusp tips, and susceptibility to caries do not apply to the mandibular first molars in the same context or may be more characteristic of different teeth. For example, the oblique ridge is a feature commonly found on certain maxillary molars, and the mandibular first molar typically has five cusp tips. While susceptibility to caries can vary among all teeth based on factors such as location and oral hygiene practices, it isn't specifically noted that mandibular first molars are the last to be affected compared to other permanent teeth. Thus, recognizing that these molars are indeed the largest within the lower arch is a key aspect of understanding their role and characteristics.