4.4 artifiical teeth set-up etc

What does the occlusion rim provide?

• guideline (midline, high lip line, canine guidnace)

• proper placement of occlusal plane

• proper lip support

• correct jaw relationship

what are factors affecting setting of upper anterior teeth?

• alveolar ridge resorption

• esthetics

• phonetics

what is alveolar ridge resorption?

• In anterior maxilla it occurs upwards and backwards

• In anterior mandible it occurs downwards and backwards (lingually)

• Anterior teeth in maxillary dentures are placed forward and inferiorly

how is alveolar ridge resorption minimised/prevented in anterior teeth placed in maxillary denture?

• teeth are placed forward and inferiorly

What is importance of aesthetics when setting upper anterior teeth?

• lip support by teeth is important

• amount of tooth showing about 1mm

What is speech (phonetics) affected by setting of upper anterior teeth?

• speech affected, contour + bulk of palate affected

• Central incisor - incisal edge in contact with horizontal plane

• Lateral incisor - incisal edge is 1-2 mm higher than plane

• Canine - its cusp is in contact with horizontal plane

what is the inclination of central incisor compared to sagittal plane and vestibularly?

• long axis is parallel to sagittal plane

• vestibular inclination is around 5-8 degrees

what is inclination of lateral incisors compared to sagittal plane and frontal plane?

• inclination to sagittal plane is between 10-20 degrees

• inclination to the frontal plane is approx 8 degrees

what is the inclination of canines compared to sagittal plane?

• inclination to sagittal plane is about 7-10

• there is axial rotation of crown as well

• from frontal view, only mesial part of crown should be visible

what should be the only part visible of canines from frontal view?

• mesial part of crown

what are the factors to remember when arranging posterior teeth?

• neutral zone

• position on ridge

• balanced occlusion

what is neutral zone (arrangement of posterior teeth)?

• potential space between lips/cheek and tongue

• area where forces between them as equal, providing equilibrium

• ensures denture stability

how does position on ridge affect arrangement of posterior teeth?

• posterior teeth placed on ridge crest are vital for lower denture stability

• Maxillary dentures, teeth may be placed outside ridge crest if needed

how is balanced occlusion important in arranging posterior teeth?

• bilateral, simultaneous contact of anterior and posterior teeth in various positions, ensuring proper chewing and stability

what is the compensating curve?

• anteroposterior and mediolateral curving within alignment of artificial teeth used for balance occlusion development

• Arc introduced in complete removable dental prostheses to counteract opening influences during mandibular excursive movements.

• Necessary for balanced occlusion, involves curve of spee (posterior teeth) and curve of monson

what is curve of spee?

• occlusal alignment of teeth

• median plane from mandibular canine cusp tip through premolar and molar buccal cusp tips to anterior border of mandibular ramus, ending at anterior portion of mandibular condyle

• essential for balanced occlusion

what is curve of monson?

• each cusp and incisal edge conforms to a segment of an 8-inch diameter sphere, centred around region of glabella (in between eyebrows)

• Crucial for balanced occlusion, aid in lateral and protrusive mandibular excursive movements

what is curve of wilson?

• represents mediolateral curve in occlusion theory

• Lower arch - it’s concave due to lingual inclination of right and left molars, allowing corresponding cross-aligned cusps to fit into circle’s circumference

• Upper arch - it’s convex due to buccal inclination of long axes of upper teeth. Essential for spherical occlusion theory, maintaining balanced occlusion

what is NEEDEDD for balanced occlusion?

• anteroposterior curve of posterior teeth (curve of spee)

• mediolateral curve (curve of monson)

what is the anteroposterior curve?

• on middle plane

• tip of lower canine and follows outer cusps of premolars and molars

• continues to front border of lower jaw and ends at frontmost part of jaw joint

• also known as curve of spee

what is mediolateral curve?

• curve formed by alignment of teeth when viewed from front

• helps ensure proper contact and distribution of forces during biting and chewing

how should maxillary posterior teeth be aligned?

• make contact in two ways:

  • posterior teeth buccal surfaces make contact with a straight line drawn from labial surface of canine backwards

  • Angle between vestibular surfaces of canines and premolars and molars is 155 degrees

how is alignment of mandibular teeth done?

• They are set to occlude with maxillary teeth in anteroposterior and mediolateral curves

how are upper/lower posterior teeth positioned?

• buccal cusps of upper posterior teeth overlap those of lower

• Palatal cusps of upper posterior teeth contact with central fossae of mandibular teeth

what are the rules for distal teeth arrangement?

• 1st premolar - contact with horizontal plane with vestibular cusp only

• 2nd premolar - contacts horizontal plane with both vestibular and lingual cusps

• 1st molar - contacts horizontal plane with mesiolingual cusp (mesiobuccal cusp 0.5mm, distolingual cusp 1mm, distobuccal 1.5mm over horizontal plane )

• 2nd molar - 1mm over horizontal plane

Lower

• 1st molar - mesiobuccal cusp of 1st upper molar in contact with groove between mesiobuccal and distobuccal surface of lower 1st molar

• 1st premolar/2nd premolar/2nd molar - vestibular cusp in contact with central groove of antagonist

steps of flasking

1. mix gypsum with proper water/powder ratio

2. fill lower part of flask, place model (make sure not to exceed edge of flask)

3. use soap water/isodent/other materials for isolation after hardening

4. Put upper part of flask and fill with gypsum

5. after hardening, put flask in boiling water for 5 mins

6. open flask and remove plasticised base plate and wax

7. properly isolate denture

what occurs in polymerisation?

1. mix acrylic resin (Polymer+monomer)

2. stages of polymerisation:

   • wet sand phase

   • sticky (threads) phase

   • plastic (working) phase

   • elastic (gummy) phase

3. put acrylic in empty space, close flask and press it

4. Two options for high-temperature polymerisation cycle:

   • long cycle - gradually heat flask in room temperature water, reach 60 degrees for 1 hour, then 100 degrees for 30 minutes, followed by slow cooling

   • Short cycle - boil water for 30 minutes, don’t exceed 100 degrees as monomer evaporates at 100.3 degrees

5. After cooling, remove denture from gypsum, clean/polish should be done to ensure smooth polished finish

what are immediate removable partial dentures?

• any removable dental prosthesis fabricated for the placement immediately following removal of natural teeth

what are examples of immediate removable partial dentures?

• Kemeney denture

• Pelots RPD

• Immediate removable partial dentures

Kemeney denture

• plastic toot-alveolar clasps

• main indication: abutment teeth mobility

Pelots RPD

• plastic alveolar clasps

• mobility of teeth, retentive

Immediate removable partial dentures?

• any removable dental prosthesis fabricated for placement immediately following removal of natural tooth/teeth

• Alveolar ridge in upper frontal area