anatomic landmarks

7/30/2019 Anatomic Landmarks

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Anatomic landmarks of the maxilla and mandible



Limiting areas



• Frenum: Folds of mucous membrane, do not containsignificant muscle fibres. High frenum attachments will

compromise denture retention and may require frenectomy.

• Labial vestibule: When the vestibule is properly filled with

the denture flange, greatly enhances stability and retention.



• Buccal frenum: The muscles attached to it arelevator anguli oris, buccinator and orbicularis oris.

• Buccal vestibule: Extends from the buccal

frenum to the hamular notch. Thickness of thedenture border in this area is determined bycoronoid process of the mandible and masseter muscle.



Hamular Notch: It is present between maxillarytuberosity and hamulus of the medial pterygoidplate. The pterygomandibular ligament attaches to

the pterygoid hamulus. Capturing the hamular notch in the impression is critical to the retention of the maxillary denture. Improper molding of this areacould lead to soreness and loss of retention.



• Vibrating line: It is an imaginary line drawnacross the palate that marks the beginning

of motion in the soft palate when the patient

says “ah”.• Extends from one hamular notch to another.

Denture border should extend 1-2 mm

beyond the vibrating line.



Supporting areas



• Canine eminence: This bony eminence provides denture support,

prevents the denture from rotating and improves denture stability• Incisive papilla: It is a pad of fibrous connective tissue overlying

the orifice of the nasopalatine canal. Pressure in this area will

cause a disruption of the blood flow and impingement on the

nerve, causing the patient to complain of pain or burning

sensation. The denture should be relieved over this area



• Tuberosity: It is an important primarydenture support area. It also provides

resistance to horizontal movements of the

denture



• Coronoid process: the patient is instructed to openwide, protrude and go into lateral movements. The widthof the distobuccal flange will then be contoured by theanterior border of the coronoid process.

• Fovea palatina: two small pits or depressions in theposterior aspect of the palate, one on each side of themidline, at or near the attachment of the soft palate tothe hard palate and slightly posterior to the termination of the denture.



• Primary stress bearing area :

Crest of the residual alveolar ridge

• Secondary stress bearing area: Rugae

• Relieving area: Incisive papilla and

mid palatine raphe



Ideal maxillary ridge: • Abundant keratinized attached tissue

• Square arch • Palate U-shaped in cross-section

• Moderate palatal vault

• Absence of undercuts

• Low frenum attachments

• Well-defined hamular notches



a. incisive papilla

b. palatal rugaec. median palatine raphe

d. maxillary tuberosity

e. pterygomaxillary notch

f. fovea palatini andvibrating line area

g. buccal space

h. zygomatic process

i. residual alveolar ridge

j. buccal frenum

K. labial frenum



Limiting areas in the mandible



Labial frenum: Fibres of orbicularis oris are attached



• Labial vestibule: limited inferiorly by the mentallismuscle.

• Mentalis: elevates the skin of the chin and turns thelower lip outward. Dictates the length and thickness of the labial flange extension of the lower denture



• Buccal frenum: histologically and functionally the

same as in the maxilla• Buccal vestibule: Extends from the buccal

frenum to the retromolar pad



Masseter Groove - the actionof the masseter muscle reflectsthe buccinator muscle in asuperior and medial direction.The distobuccal flange of the

denture should be contoured toallow freedom for this actionotherwise the denture will bedisplaced or the patient willexperience soreness in the area



• Retromylohyoid space - lies at the distal end of thealveolingual sulcus. Bounded medially by the anterior tonsilar pillar, posteriorly by the retromylohyoid curtainwhich is formed posteriorly by the superior constrictor

muscle, laterally by the mandible and pterygomandibular raphe, anteriorly by the lingual tuberosity of the mandibleand inferiorly by the mylohyoid muscle.

• ***The retromylohyoid space is very important for denture stability and retention.



• The curtain moves upward and backward as the tongue moves

upward and

• backward in swallowing. It moves upward and forward during

• protrusive and lateral movements of the tongue. The amount of

• upward and forward movement of the curtain during these protrusive• and lateral movements is referred to as the lateral throat form of the

• mandibular denture. If this movement is slight and the angle formed

by

• the posterior part of the curtain to the retromolar pad is

approximately

• 90 degrees, it is a Class I throat form. Extreme forward movement of

• the curtain resulting in an angle of 45 degrees or less in Class III

throat

• form and in between the two is Class II throat from



• The amount of posterior lingual extension of the base is controlledby the movement of this curtain. Overextension of the denture flange

results in the patient complaining of a sore throat or unseating of the

denture. Underextension handicaps the tongue in controlling the

lower denture and allows ingress of food under the denture. This

tissue offers very little resistance to pressure so the operator mustbe careful not to create a false undercut by displacing it when

making the impression.



Supporting areas



• Buccal Shelf: bordered externally by the externaloblique line and internally by the slope of the residual

ridge. This region is a primary stress bearing area in themandibular arch.

• The buccal shelf is the primary support area because itis parallel to the occlusal plane and the bone is verydense. These two factors make it relatively resistant toresorbtion.



Buccal shelf area (area within the dotted lines).

The greater the access to the buccal shelf the moresupport there is available for the denture. Access is

determined by the attachment of the buccinator.



The size and position of the buccal shelf vary relative to the

degree of alveolar ridge resorption



Mental Foramen: the anterior exit of the mandibular canaland the inferior alveolar nerve. In cases of severe residualridge resorption, the foramen occupies a more superior position and the denture base must be relieved to preventnerve compression and pain.



• One constant, relatively unchanging structure on themandibular denture bearing surface is the retromolar pad (dotted line).

• The pad contains glandular tissue, loose areolar connective

tissue, the lower margin of the pterygomandibular raphe,fibers of the buccinator, and superior constrictor and fibersof the temporal tendon. The bone beneath does not resorbsecondary to the pressure associated with denture use. Theretromolar pad is one of the primary support areas.



Genial tubercle: present on the anterior surface of the

mandible and serve as the attachment sites for thegeniohyoid and genioglossus muscles. In patients’ withsevere ridge resorption, the genial tubercles may causediscomfort if they are exposed to the denture base



Mylohyoid muscle: forms the muscular floor of

the mouth. Arises from the mylohoid ridge of themandible. Determines the lingual flange extensionof the denture



Note the position of the

mylohyoid ridge as itvaries relative to thedegree of the alveolar ridge resorption



• Primary stress bearing area:

Buccal shelf

• Secondary stress bearing area: Slopes of the residual alveolar ridge

• Relieving area: Crest of the residual

alveolar ridge



Ideal mandibular ridge:

• Well defined retromolar pad

• Blunt mylohyoid ridge

• Deep retromylohyoid space

• Low frenum attachments

• Absence of undercuts

• Abundant attachedkeratinezed mucosa

• Adequate alveolar height



a. labial frenum

b. residual alveolar ridge

c. retromolar padd. lingual frenum

f. external oblique line

g. buccal frenumh. masseteric notch

anatomic landmarks

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