mandible anatomy

Question 1

limiting structures in complete denture design

Answer 1

(blue)

• Sites that will guide us in having an optimum extension of the denture, so as to engage maximum surface area without encroaching upon the muscle actions
• Encroaching upon these structures will lead to dislodgement of the denture and/or soreness of the area, while failure to cover the areas up to the limiting structure will imply decreased retention stability and support

Question 2

relief areas in complete denture design

Answer 2

(green)

• Areas where there are either resorption under constant load, having fragile structures within or covered by thin submucosa which can easily be traumatised
• Denture should be designed in such a way that the masticatory load is not concentrated over these areas

Question 3

supporting structures/stress bearing areas in complete denture design

Answer 3

(red)

• Load bearing areas
• Most the load should be concentrated on these areas
• Support is the resistance to displacement towards underlying structures

Question 4

labial frenum

Answer 4

limiting structure

• Fibrous band extending from the labial aspect of the residual alveolar ridge to the lip containing a band of the fibrous connective tissue, which helps in the attachment of the orbicularis oris muscle
• Quite sensitive – hence need for appropriate labial notch

Question 5

labial sulcus

Answer 5

limiting structure

• Runs from the labial frenum to the buccal frenum on each side
• Mentalis muscle is quite active in this region

Question 6

buccal frenum

Answer 6

limiting structure

• Fibres of buccinator area attached to the buccal frenum
• Should be relived to prevent displacement of the denture during function

Question 7

buccal sulcus

Answer 7

limitng structure

• Extends posteriorly from the buccal frenum to the outside back corner of the retromolar region
• Area maximisation can be safely done here as the fibres of the buccinator run parallel to the border, hence displacing action due to buccinator during it’s contraction is slight
• The impression is at widest within this region

Question 8

alveolingual sulcus

Answer 8

limiting structure

Divided into 3 parts

• Anterior part
  
  • From lingual frenum to mylohyoid ridge
  • Shallowest portion (least height) of the lingual flange
• Middle region
  
  • From the premylohyoid fossa to the distal end of the mylohyoid region
• Posterior portion
  
  • From the end of the mylohyoid ridge end to the retromylohyoid curtain
  • Provides a valuable undercut area, so important retention

Overextension causes soreness and instabilit

Question 9

lingual frenum

Answer 9

liminting structure

• Relief should be provided in the anterior region of lingual flange

Question 10

retromolar pads

Answer 10

limiting structure

• Pear shaped triangular soft pad tissue at the distal end of the lower ridge
• Important structure – forms the posterior seal of the mandibular denture
• Denture base should extend up to 2/3 of the retromolar pad triangle

Question 11

genial tubercle

Answer 11

relief area

• Areas of muscle attachment (genioglossus and geniohyoid)
• Lies away from the crest of the ridge
• Prominent in resorbed ridges, therefore adequate relief should be provided

Question 12

torus mandibularis

Answer 12

relief area

• Abnormally bony prominence
• Bilaterally on the lingual side near the premolar area
• Covered by thin mucosa, so it should be relieved

Question 13

mylohyoid ridge

Answer 13

relief area

• Attachment of the mylohyoid muscle
• Running along the lingual surface of the mandible
• Anteriorly the ridge lies close to the inferior border of the mandible
• Posterior it lies close to the residual ridge
• Covered by thin mucosa which may be traumatised by denture base, hence it should be relived
• Extension of the lingual flange is to be beyond the palpable position of the mylohyoid ridge but is not in the undercut

Question 14

residual alveolar ridge

Answer 14

support area

• Secondary stress bearing area
  
  • Buccal and lingual slopes are secondary stress bearing areas

Question 15

buccal shelf

Answer 15

support area

• Primary stress bearing area
  
  • Extends from the buccal frenum to retromolar pad
  • Between external oblique ridge and crest of alveolar ridge
• Boundaries
  
  • Medially – crest of the ridge
  • Laterally – external oblique ridge
  • Distally – retromolar pad
  • Mesially – buccal frenum
• Width of area increases as the alveolar resorption continues