The deciduous mandibular first molar along with the other deciduous molars of the maxillary and the mandibular dental arch grind food into small particles. This tooth does not resemble morphologically with any other deciduous or permanent teeth.
Timeline of Development and Eruption
Following is the summary of the timeline of the development of the deciduous mandibular first molar.
- Beginning of calcification: 15.5 weeks in utero
- Crown completion: 5.5 months after birth
- Tooth eruption: 16 months
- Completion of root: 2.5 years
The deciduous mandibular first molar is replaced with the mandibular first premolar around the age of 10-11 years by the process of exfoliation.
Buccal Aspect
- The mesial outline of the crown of the deciduous mandibular first molar is almost straight. While the distal outline of the crown it converges from the contact area to the cervical area of the crown.
- The height of the distal part of the crown is less compared to the mesial part of the crown.
- There are two cusps on the buccal aspect mesiobuccal cusp and the distobuccal cusp.
- The mesiobuccal cusp is slightly wider and higher as compared to the distobuccal cusp which is round and smaller.
- In between the two buccal cusps a shallow developmental groove is present called the buccal developmental groove.
- There are two roots, the mesial and distal roots.
- The root trunk on all the deciduous molars including the deciduous mandibular first molar is small and the roots are long and slender.
- In the apical third portion, the roots spread beyond the crown outline, especially the distal root.
Lingual Aspect
- The crown and the root converge towards the lingual aspect.
- There are two cusps on the lingual aspect, mesiolingual and distolingual cusps.
- The mesiolingual cusp is long and sharp while the distolingual cusp is short and round.
- Parts of the mesiobuccal and mesiolingual cusps are visible from the lingual aspect.
- The cervical line is straight on the lingual aspect.
Mesial Aspect
- The buccal surface of the tooth on the cervical one-third of the crown has a bulge or convexity.
- Mesiobuccal and mesiolingual cusps are visible from the mesial aspect.
- A well-developed mesial marginal ridge connects the mesiobuccal cusp with the mesiolingual cusp.
- The lingual outline of the crown extends beyond the outline of the root. While the buccal outline is nearly in line with the buccal root outline.
- The mesial root is broad buccolingually and it has a square outline. Sometimes a developmental depression extends the full length of the root surface.
Distal Aspect
- The cervical line extends almost straight buccolingually on the distal aspect.
- The distobuccal and distolingual cusps are not long or as sharp as the mesial cusps. Therefore, parts of the mesiobuccal and mesiolingual cusps are visible from the distal aspect.
- The distal marginal ridge connects the distobuccal cusp with the distolingual cusp and it is not well developed.
- The distal root is more rounded, shorter, and tapered as compared to the mesial root. Therefore, part of the mesial root is visible from the distal aspect.
Occlusal Aspect
- The outline of the deciduous mandibular first molar is irregular.
- On the buccal aspect of the crown, prominence is present on the mesiobuccal part.
- The mesiolingual cusp is the largest and most well-developed cusp.
- The central developmental groove extends from the pit of the mesial triangular fossa and crosses the occlusal surface and terminates into the distal triangular fossa. This central developmental groove divides the occlusal surface into buccal and lingual halves.
- There are three fossae on the occlusal surface. The central fossa, mesial triangular fossa, and distal triangular fossa.
- The mesial profile of the crown appears flat while the distal profile is convex.
- There is numerous supplementary groove that emerges from the main developmental groove.
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