1 Flashcards
Problem with alginate impression - viscosity.
Because of their high viscosities, these impression materials will often displace the soft tissues ofthe vestibules, resulting in an overextended impression and resulting cast
Prior to making the impression, the patient is instructed to
rinse his or her mouth with water to reduce the \iscosit' of the saliva
Prior to inserting the impression tray, the patient should be asked to
swallow to elim- inate excess saliva
Figure 6-8 Note that a “fatty” pad of tissue (A) is often
present in the distobuccal area of the mandibular arch and may fold over the retromolar pad (B) and become trapped in an impression.This fold can be minimized by lifting this tissue upward and away from the retromolar pad while seating the impression.
An irreversible hydrocolloid impression should be poured in dental .stone within
10 minutes
Retention nodules for a cast
stone “mountains” on the bottom of the cast that are then used to prop up the initial die in another blob of wet stone so as to create a good land area.
Wlicn properly shaped, the cast sbould also exhibit land areas around the vestibules and a base of approx- imately
12-13 mm (1/2 inch) in tliickness
The land area shotild be approximately
2-3 mm (1/8 inch) wide on the buccal and labial
land area should be about
5-6 mm (1/4 inch) wide in the posterior
For most patients, the labial and lingual flange lengths will be of
equal length unless the patient has had a surgical extension of the vestibular notch or severe bone loss.
When border molding before you trim
chill in ice water **only when using wax/heated material
VPS does not have the viscosity or rigidity of modeling compound and therefore cannot be used to
correct borders that are underextended by more than 4-5 mm.
Also if not supported by the impression tray, VPS cannot be depended on to form
tray fianges 2-3 mm in thickness
The buccal shelf areas are initially border molded and must be completed
individ- ually
The minimum thickness of a master cast should be
12-15 mm in the thinnest area.
.The land areas should be trimmed so that the vestibules are no more than
3 mm In depth
Following the block out of the master cast, the cast is
soaked in room-temperature water for five tninutes in order to expel air from within the stone, which will help mini- mize the formation of bubble-like deiccts in the completed record base.
Tbe soaking of the cast must be completed after the cast has been blocked out with wax because
the wax will not stick to a wet surface.
Max record base; plane of occlusion is
parallel with the base of the cast
max record base: anterior portion of the occlusion rim is at approximately a
15° angle to offer lip support
support.The poste- rior ofthe maxillary occlusion rim should slope occlusally at approximately a
45 degree angle
Blocking out can
lead to more lip support than is necessary.
In the posterior, wax should be added or removed to achieve a bilateral
buccal corridor. This space is created by sloping the maxillaiA occltision rim inward in the posterior area
For photos use interpupillary distance ratios relative to teeth to
get size for denture teeth relative to current interpupillary distance.
Posterior denture teeth are not set on the slope leading from the residual ridge to the retromolar pad because of its tendency to act as an
inclined plane when the patient chews food - irritant.
Generally the teeth are arranged in the following order:
(1) maxillary anterior teeth—following the maxillary occlusion rim, (2) mandibular anterior teeth—using the occlusion rims and maxillary teeth as guides, (3) mandibular posterior teeth—using the anterior teeth, retromolar pads, and residual ridges as guides and (4) maxillar)’ posterior teeth—using the mandibular posterior teeth as guides.
The position of the incisai edge of a maxillary anterior tooth generally provides for
phonetics and esthetics, whereas the cervical portion,or necks, of the teeth and the fullness of the denture base determine lip support.
Christensen’s phenomena, lhe space that occurs between opposing occlusal surfaces during excursive movements, is
not acceptable for complete denture patients
For improved masticatory function, it is generally better to eliminate the
first premolar rather than the second molar
the mandibular posterior teeth are arranged on a
flat occlusal plane with the long axes of the posterior teeth arranged perpendicular to the plane of occlusion for a nonbalanced occlusion
for a balanced tooth arrangement, a
curved template is used
The labial frenulum area is often
prominent and easily displaced. Care must be taken when making an impression of this structure.
Wet a cast before trimming to prevent
slurry material from sticking.
The retromylohyoid areas receive minimal
wax relief (C) in order to have good adaptation of this area
A second guide that can be used to estimate the canine-to-canine measurement Is to measure between the
centers of the left and right hamular notches (A) and add 10 mm.
