Tutorial 9 - anatomy relevant to RPD construction Flashcards
What muscles and anatomical structures lie at the periphery of correctly extended upper and lower partial dentures in a patient with only their canine teeth remaining?
Upper Denture: Bordered by the buccinator orbicularis oris, levator anguli oris laterally. Posteriorly, the hamular notch, fovea palatini, and the soft palate influence the extension.
Lower Denture: Bordered by the buccinator and orbicularis oris laterally, mylohyoid medially, and retromylohyoid fossa posteriorly. The lingual frenum and genioglossus also influence the lingual extension. Also the superior constrictor muscle, genuiglossus, sublingual gland.
Where can the retromyloid fossa be found?
google image
Why does the mylohyoid muscle influence denture design?
Limits lingual extension of the lower denture as it forms the floor of the mouth.
Therefore, Impression techniques should record the functional position of the mylohyoid to avoid an overextended denture, which could cause discomfort or instability.
What are the attachments of Mylohyoid muscle?
Origin: Mylohyoid line of the mandible.
Insertion: Body of the hyoid bone and midline raphe.
What anatomical features will influence your choice of major connector for the lower denture?
Lingual frenum: Limits the superior border of a lingual bar.
Floor of the mouth height: If shallow, a lingual plate may be preferred over a lingual bar. less than 7mm, plate used instead, but more plaque retentive. FOM, sublingual gland, lingual fraenum and genuiglossus will affect depth of sulcus.
Mental foramen - lots of bone resorption can lead to it being compressed.
Mandibular tori: Presence may require an alternative design, such as a sublingual bar.
Perio status of the teeth - lingual plate can be used for better support for mobile teeth
Muscle attachments
Alveolar ridge shape
What anatomical structures may influence / prevent implant placement?
Maxillary sinus may limit implant placement in the posterior region.
Nasopalatine canal could affect central incisor implant positioning.
Inferior alveolar nerve and mental foramen could limit implant depth and position.
Insufficient bone height due to resorption.
Lingual concavity in the posterior mandible poses a risk of lingual plate perforation.
How could you determine whether your special trays are overextended and encroaching on some of these oral muscles?
Ask the patient to perform movements like tongue protrusion and cheek retraction to see if the tray is displaced.
Inspect impressions for signs of tissue impingement or lack of retention.
What problems may a palatal torus give when constructing an upper partial denture? How may these problems be overcome when designing the denture?
problems include:
1. Prevents proper adaptation of the major connector.
2. Can cause ulceration due to excessive pressure.
3. Mucosa overlying torus is very friable and easily traumatised - pain and infection (with improper hygeine)
Solutions:
1. Avoid placing a major connector directly over the torus. Use a U-shaped palatal connector or relief areas in the denture base.
- Surgical removal if interference is significant
What problems may occur as a result of the differences in support between the mucosa and the natural teeth? How are these overcome?
The mucosa is approx 10-times more displaceable than the periodontal ligament, so the denture will pivot around the rest seat and the rigid clasp will grip the abutment tooth and may damage it!!
Overcome by:
Solution 1 - Place the rest seat mesially
Solution 2 - Use a flexible gingivally approaching clasp e.g. an I Bar
Solution 3 – maximise support Use the Altered Cast Technique:
what is incisive papilla?
A small mass of fibrous tissue about 1 cm behind the upper incisors over the incisive canal.
What is the lingogingival/palatal gingival remnant in edentulous patients?
scar seen in maxilla just palatal to the alveolar crest. It indicates position of the palatal gingivae when teeth were present
what are the fovea palatinae?
A pair of mucous gland duct orifices near the midline at the junction of the soft and hard palate.
What is the hamular notch?
Posterior border of special tray/denture should rest in these notches in order to obtain a posterior seal, BUT if denture extends distal to the notches it will interfere with the action of the pterygomandibular raphe
What is the Vibrating Line?
marks the boundary between the movable and immovable parts of the palate:
Hard palate: The front part of the roof of the mouth, which is firm and fixed in place.
Soft palate: The back part of the roof of the mouth, which is soft and moves during swallowing or speech.
Where is the coronoid process?
lies lateral to maxillary tuberosity
What are rugae?
transverse ridges of the hard palate shaped to facilitate movement of food towards the pharynx
Where is the palatine raphe?
midline of palate
what is the frenum
fibrous tissue fold between lip and alveolus - labially and buccally
Where is the retromolar pad?
fucntion in denture design?
MANDIBULAR
ESSENTIAL to record for dentures for sealing and retention
Where can we find the mylohyoid ridge?
essentual for retention (via border seal) and stability.
What is the area behind where the molars would be called? maxillary
maxillary tuberosity
How can coronoid process affect denture design?
can impinge on buccal flange of upper denture and cause instability.
Hoe can the thickness of the submucosa affect fit of denture?
*Thickness of the submucosa – affects support retention and stability. e.g. a fibrous anterior ridge will lead to poor stability and support which will in turn affect retention.
How does the Obicularis Oris affect dentures?
will deseat the denture if place to labially
