The Lewis offset is a term for the portion of the central groove on a permanent

mandibular first molar The mandibular first molar or six-year molar is the tooth located distally (away from the midline of the face) from both the mandibular second premolars of the mouth but mesial (toward the midline of the face) from both mandibular second molars. It ...

which lies between the two central pits. It was named for long time dental anatomy instructor Dr. Christopher S. Lewis, a Mercer Island, WA dentist.

Details

The offset lies at an angle to the mesio-distal axis of the tooth, and causes the

mesial This is a list of definitions of commonly used terms of location and direction in dentistry. This set of terms provides orientation within the oral cavity, much as anatomical terms of location provide orientation throughout the body. Terms ...

portion of the central groove to be located further buccally than the distal portion. This buccolingual shift correlates with a relative difference in size between the mesial and distal cusps on these teeth - the mesiolingual cusp is larger than the mesiobuccal cusp, but the distobuccal cusp is larger than the distolingual cusp. It also allows for the buccal groove to be located mesial to the lingual groove which is mandatory to accommodate the relative sizes of the three cusps on the buccal and two cusps on the lingual of the occlusal surface of the tooth.

References

*Ash, Major M. and Stanley J. Nelson, 2003. ''Wheeler’s Dental Anatomy, Physiology, and Occlusion.'' 8th edition. Teeth {{dentistry-stub nl:Eerste molaar pt:Primeiro molar inferior