ANATOMICAL CONSIDERATIONS - PRIMARY IMPRESSIONS

what material are most dentures made of

acrylic resin

what are the stages of making dentures

• denture construction

• denture provision

what steps is denture construction made up of

denture construction

1. record the shape of the ridges and supporting tissues via primary and secondary impressions

2. establish the correct placement of teeth

3. registration

4. make a wax template/ wax block and try it in

when do primary and secondary impressions take place

at visits 1 and 2

what is the process of taking primary and secondary impressions

• take primary impressions of edentulous ridges using stock trays filled with alginate

• a primary cast is made from the primary impression

• a special tray is made from the primary cast

• a secondary impression is taken using the special trays filled with zinc oxide

image of denture construction steps

• notice how the stock trays are perforated but the special tray is close-fitting tray

how is the correct placement of teeth established in denture construction

• registration - visit 3

• wax try-in - visit 4

how many appointments does denture construction require

4

outline the steps of denture provision

1. denture fit

2. post-fit review

3. 6-12 months post-fit review

how many clinical stages in total does it take to provide dentures

7 clinical stages

if everything goes to plan, after how many appointments should a patient receive their dentures

5 apointments

outline the fovae palatini

• two small indentations at the junction of the soft and hard palate (maxillary structure)

what is the relevance of the fovae palatini to dentures

• these indented regions identify the position of the posterior border of the maxillary denture

• the fovae palatini should lie 1-2mm distal to the posterior denture border

describe the placement of these dentures

these dentures are underextended

what is notable about this photo

• denture candidiasis is present on the hard palate

• appearance: speckled palate

• probably caused by patient wearing dentures at night leading to the fungal infection

outline the hamular notches

• maxillary structures

• formed at the junction of the maxilla and the pterygoid hamulus process of the sphenoid bone

what is the relevance of the hamular notches to dentures

• the hamular notches are where the back of the maxillary dentures should sit on the lateral sides

what happens if the maxillary dentures are improperly moulded in the hamular notch region

• soreness

• loss of retention

what other intraoral structures do we need to record

• frenae: record any prominent frenae (often found in canine region)

• sulci: record the full depth of the labial and buccal sulci

what is the significance of recording maxillary frenae and sulci

• if any prominent frenae are trapped within the dentures, it can lead to soreness and infections

• trapped frenae also reduce the retention of the dentures in function

why are frenae and sulci relevant to dentures

• these structures mark the maximum functional extent of the denture border

• the midline frenum is a key reference point when taking impressions to allow correct tray insertion

the ________ the sulcus the ____ resistance to lateral denture movement can be achieved

the shallower the sulcus, the less resistance to lateral denture movement can be achieved

i.e. the more the dentures will move around

what does the purple arrow represent

incisive papilla

what is the relevance of incisive papilla to dentures

• key guide to placement of maxillary central incisors in complete dentures

• the mean distance between the distal border of the incisive papilla and labial surface of the central incisor is approx. 12mm

outline retromolar pads

• mandibular structures

what is the relevan

outline the mylohyoid and external oblique ridges

what is the relevance of the MH ridge and EO ridge to dentures

• the mylohyoid ridge signifies the lingual peripheral border of the mandibular denture

• the external oblique ridge signifies the buccal peripheral border of the mandibular denture

outline the lingual gingival remnant

• not seen in every patient, more commonly in newly edentulous patients

what is the relevance of the lingual gingival remnant to dentures

• the LGR is an indicator for the lingual margin of posterior teeth and labial surfaces of anterior teeth

outline the genial tubercles

• insertion point for the genioglossus

• becomes more significant as the lower ridge resorbs

what is the relevance of the genial tubercles to dentures

• if the denture rocks on them it can be traumatic for the patient

outline the lingual frenum

• band of tissue that attaches the tongue to the floor of the mouth

• important when taking impressions that the patient moves their tongue from side to side and forwards so the LF is not trapped

what is the relevance of the mental foramen to dentures

• as the jaw resorbs, the mental foramen becomes closer to the surface so the mucosa covering it does not provide much protection

• the mental nerve therefore is more exposed

• patients can get shooting pains as a result of pressure from denture

what are examples of some key information to give to patients to gain informed consent

• diagnosis - current problem

• prognosis - chance of success of the new dentures

• can the patient’s desired be achieved

• the number of visits needed

• ask the patient if they understand and if they have any questions

• document in clinical notes what has been discussed

what information should be given to patients during subsequent visits

• explain what is going to happen this visit

• ask the patient if they understand/ have questions

• re-establish the treatment objectives

• write up in notes what has been discussed

what is the purpose of primary impressions

• to record the patient’s anatomy to allow the construction of special trays

what is the most popular primary impression material

alginate

what are advantages of alginate

• simple technique

• cheap to use

• bonds to tray with adhesive

• viscous during placement so less chance of patient discomfort

• elastic when set so does not crumble/ break easily

what are disadvantages of alginate

• unstable if not cast up quickly

• is inaccurate in recording large undercuts/ prominences if not fully supported by the tray

• can debond from the stock tray if large undercuts are present

how should you select the stock tray size

• if the patient already has a set of dentures, use a set of calipers and take an inter-hamular measurement and compare it to the tray size

• if not, just use an educated guess based on patient dimensions

• patients may need different sizes for the upper/ lower jaw

what is the next step after selecting a tray size

• try in the tray by rotating it into place

• ensure it covers the full denture bearing area

if none of the trays fit quite right, what can be done to adapt it

• use a material called greenstick

• most commonly used to add material to cover the retromolar pads and palate

how is greenstick used

• need very hot water to allow it to soften evenly

• need a flame for the ‘stick’ variety then hot water

• very difficult to attain the ideal temperature to allow it to work without burning

once the right tray size is acquired, what is the next step

• spray the adhesive, ensuring copious coverage

• leave for 5 minutes before taking the impression

where should you stand when taking impressions

• maxillary impression: stand behind the patient’s right shoulder, their maxilla should be at your elbow height

• mandibular impression: stand in front of the patient and the mandibular should be at your elbow height

» patient should be at a 60°

instructions for a maxillary impression

what anatomical landmark should be used as a key reference point when taking a primary impression

• the superior/ inferior labial frenum

what else should be done whilst taking an impression

• border moulding

• functional movements like lifting the upper lip, moving tongue around

what should you check for after taking out a primary impression

• check for alginate debonding

• if it debonds, then retake the impression

after taking a good primary impression, what is the next step

• trim peripheral excess with a scalpel until it is 1-2mm short of the sulcus depth

• trim the area of frenal attachment so it can move freely when put back in the mouth

how is a more accurate impression of the periphery achieved

• by carrying out a wash impression with a less viscous mix

• do not overfill with alginate

how should you mark the primary impression for the close fitting special tray

• use an indelible pencil

• mark 1-2mm inside the functional depth of the periphery

• this gives the technicians an idea of where you want the special trays to extend to

if the patient likes their old dentures, what can be done to mimic teh features in their new dentures

• provide an alginate impression of the old set of dentures

what is the last step before sending the impressions to the lab

• disinfect in Perform for 10 minutes