11 The Permanent Maxillary Molars
The maxillary molars differ in design from any of the teeth previously described. These teeth assist the mandibular molars in performing the major portion of the work in the mastication and comminution of food. They are the largest and strongest maxillary teeth, by virtue both of their bulk and of their anchorage in the jaws. Although the crowns on the molars may be somewhat shorter than those on the premolars, their dimensions are greater in every respect. The root portion may be no longer than that of the premolars, but instead of one root or a bifurcated root, the maxillary molar root is broader at the base in all directions and is trifurcated into three well-developed prongs that are actually three full-size roots emanating from a common broad base above the crown.
The normal location of the first permanent molar is at the center of the fully developed adult jaw anteroposteriorly. As a consequence of the significance of their positions and the circumstances surrounding their eruption, the first molars may also be considered cornerstones of the dental arches. A full realization of the significance of these teeth as units in the arches and their function and positions relative to the other teeth will be gained when an opportunity comes to study the arrangement of the teeth with their occlusion and the temporomandibular articulation of the jaws. Subsequent chapters cover those phases. The mandibular molars are described in Chapter 12.
Maxillary First Molar
Figures 11-1 through 11-18 illustrate the maxillary first molar from all aspects. The crown of this tooth is wider buccolingually than mesiodistally. Usually the extra dimension buccolingually is about 1 mm (Table 11-1). This, however, varies in individuals (see Figure 11-17, 1, 5, 7, and 9). From the occlusal aspect, the inequality of the measurements in the two directions appears slight. Although the crown is relatively short, it is broad both mesiodistally and buccolingually, which gives the occlusal surface its generous dimensions.

Figure 11-1 Maxillary right first molar, occlusal aspect. MBCR, Mesiobuccal cusp ridge; CF, central fossa (shaded area); MTF, mesial triangular fossa (shaded area); MMR, mesial marginal ridge; MLCR, mesiolingual cusp ridge; OR, oblique ridge; DLCR, distolingual cusp ridge; DF, distal fossa; DTF, distal triangular fossa (shaded area); DMR, distal marginal ridge; DBCR, distobuccal cusp ridge.

Figure 11-2 Maxillary right first molar, occlusal aspect, developmental grooves. BG, Buccal groove; BGCF, buccal groove of central fossa; CGCF, central groove of central fossa; FCG, fifth cusp groove; LG, lingual groove; DOG, distal oblique groove; TGOR, transverse groove of oblique ridge; CP, central pit.

Figure 11-3 Maxillary right first molar, buccal aspect. LR, Lingual root; MBR, mesiobuccal root; BDG, buccal developmental groove; MBC, mesiobuccal cusp; MLC, mesiolingual cusp; DBC, distobuccal cusp; CL, cervical line; DBR, distobuccal root.
The development of maxillary first molars rarely deviates from the accepted normal. Ten specimens with uncommon variations are shown in Figure 11-18.
DETAILED DESCRIPTION OF THE MAXILLARY FIRST MOLAR FROM ALL ASPECTS
Buccal Aspect
The crown is roughly trapezoidal, with cervical and occlusal outlines representing the uneven sides (see Figures 11-4, 11-13, 11-14, and 11-15). The cervical line is the shorter of the uneven sides (see Figure 4-16, D).

Figure 11-5 Maxillary right first molar, lingual aspect. DBR, Distobuccal root; LR, lingual root; CL, cervical line; LDG, lingual developmental groove; DLC, distolingual cusp; MLC, mesiolingual cusp; FC, fifth cusp; MBR, mesiobuccal root.
When the buccal aspect of this tooth is viewed with the line of vision at right angles to the buccal developmental groove of the crown, the distal side of the crown can be seen in perspective, which is possible because of the obtuse character of the distobuccal line angle (see Occlusal Aspect later in this chapter). Parts of four cusps are seen, the mesiobuccal, distobuccal, mesiolingual, and distolingual.
The mesiobuccal cusp is broader than the distobuccal cusp, and its mesial slope meets its distal slope at an obtuse angle. The mesial slope of the distobuccal cusp meets its distal slope at approximately a right angle. The distobuccal cusp is therefore sharper than the mesiobuccal cusp, and it is at least as long and often longer (see Figure 11-15, 4, 6, 7, 8, and 9).

Figure 11-8 Maxillary right first molar, mesial aspect. LR, Lingual root; FC, fifth cusp; MLC, mesiolingual cusp; MMR, mesial marginal ridge; MBC, mesiobuccal ridge; MCA, mesial contact area; CR, cervical ridge; MBR, mesiobuccal root.

Figure 11-9 Maxillary right first molar, distal aspect. DBR, Distobuccal root; MBR, mesiobuccal root; BDG, buccal developmental groove; DBC, distobuccal cusp; DMR, distal marginal ridge; DLC, distolingual cusp; DCA, distal contact area; CL, cervical line; LR, lingual root.
The reader must keep in mind the fact that molar roots originate as a single root on the base of the crown. They then are divided into three roots, as in the maxillary molars, or two roots, as in the mandibular molars. The common root base is called the root trunk (see Figures 11-3 and 11-8).
Lingual Aspect
From the lingual aspect, the gross outline of the maxillary first molar is the reverse of that from the buccal aspect (see Figures 11-5, 11-6, 11-13, and 11-14). Photographs or drawings show this only approximately, because all teeth have breadth and thickness; consequently, the perspective of two dimensions plus the human element, which enters into the technique of posing specimens and making drawings and photographs, are bound to result in some error in graphic interpretation.

Figure 11-11 Maxillary molar primary cusp triangle. The distolingual lobe, represented by shaded areas, becomes progressively smaller on maxillary molars, starting with the first molar, which presents the greatest development of the lobe. The plain areas, roughly triangular in outline, represent the maxillary molar primary cusp triangles.

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