Restorative Dentistry #2

Notes

Removable Prosthodontics

Surveying - show areas of undercut, determine potential paths of insertion, removal or displacement of prostheses

Complete Dentures

Retention = resistance to displacement of a denture away from ridge

Support = resistance of vertical movement of a denture towards the ridge

Muscle balance = muscular forces of tongue, lips and cheeks do not dislodge a denture during functional movements of mouth

Occlusal balance = forces of one denture on another do not dislodge either denture during functional jaw movements with the teeth in contact

Stability = ability of a denture to resist displacement by functional stresses

Retruded contact position = position of mandible when the condyles are in most retruded position in glenoid fossa, most reproducible position

Common Denture Problems

• Inadequate retention - improve peripheral seal / relining
• Inadequate support - burning sensation in denture bearing area with no redness / ulceration, trimming of poor support areas
• Muscle balance - denture loose only when patient eats / speaks, dentures feel too large, cheek biting, lower denture rises on tongue protrusion, trimming of denture areas encroaching on muscles
• Occlusal balance - pain / loose at mealtimes, selective grinding, laboratory remount and resetting teeth
• Appearance - tooth shade, shape, tooth shows, lip, face looks asymmetrical
• Speech - lisping 'f' and 'v', tooth position or vertical dimension of occlusion
• Retching - progressive adaptation to dentures by constructing baseplates first, hypnotherapy, desensitizing therapy
• Acrylic allergy - alternative materials e.g. nylon / polycarbonate, porcelain teeth

Partial Dentures

Design

Stage ① - support (mucosa / tooth / tooth and mucosa borne)

Stage ② - connect saddles (types of connector)

Maxilla : anterior palatal bar / mid palatal bar / posterior palatal bar / palatal horseshoe connector / full-coverage palatal plate

Mandible : lingual bar (4mm deep, 3mm thick, 1.5mm away from gingival margin, 1.5mm above highest level of floor of mouth)/ lingual plate / lingual bar and continuous clasp / buccal bar / sublingual bar

Stage ③ - choose path of insertion and delineate undercuts → surveyor

Stage ④ - direct retention → clasp (proximal 2/3 flexible, terminal 1/3 rigid)

👉 Undercut depths - 0.25 mm (cast cobalt-chromium), 0.5 mm (wrought gold), 0.75 mm (wrought stainless steel)

Stage ⑤ - indirect retention → resist movement as saddle rises

Stage ⑥ - resistance of movement towards teeth and tissues → occlusal rest (1-1.5 mm preparation)

Stage ⑦ - resistance to horizontal movement → clasp, contours of palate, etc.

Stage ⑧ - simplification

Copy Dentures - patients with old, worn or loose denture which where otherwise successful, satisfied with aesthetic result, poor patient cooperation e.g. dementia, autistic spectrum disorder

Overdentures - gains support from one / more abutment teeth by enclosing them beneath its fitting surface

Immediate dentures - replace one / more teeth and inserted on the day of extraction

👉 Problems - aftercare required (relining), frequent adjustments, post-extraction discomfort

Shortened Dental Arch (SDA)

Minimum number of teeth for adequate function - 20, 9 - 10 contacting pairs

↓ potential risks of partial denture wear e.g. caries, oral hygiene regimes easier, ↓ number and complexity of restorations

👉 Problems - poor transition to denture wear, ↑ tooth wear due to lack of posterior support, overloading of premolar teeth, mobility / drifting of teeth

Posselt's Envelope of Motion

RCP = retruded contact position

ICP = intercuspal position

PR = maximum protrusion

R = maximum mandibular opening with the condylar heads in reproducible retruded position, no antero-inferior condylar translation

T = maximum mandibular opening with full antero-inferior condylar translation

E = edge to edge position of incisors