Removable Pros Flashcards
What are the 4 categories of Prosthodontics?
- Removable Pros (RPD, FD)
- Fixed Pros (Crown/Bridge)
- Implant Pros (Implant supported crown)
- Maxillofacial Pros (Prosthetic Eye/Nose, Denture with hard palate)
What are the 2 categories of maxillofacial pros?
Stomatognathic (Teeth/Jaw/Soft Tissue: dentures involving hard palate)
Craniofacial (Head/Neck: artificial nose/ear/eyes)
What is the aim of prosthodontics?
Restoration of teeth + maxillofacial tissues with biocompatible substitutes
What is a prosthesis?
An artificial replacement for an absent part of the human body
What are different types of Removable Partial Dentures?
Acrylic Denture
Chrome Denture
Titanium Dentures
Valplast
What are advantages of acrylic dentures?
Easily Adjustable Simple Design Accommodates Additions Can do as immediate denture Faster (if suitable primary impression) Good if patient's teeth/gum health is variable Cheaper Good wettability (retention via suction)
What are disadvantages of acrylic dentures?
Thicker Less durable Not well accepted by patients Stains Easily (Porous) High fracture rate Plaque retention
What are acrylic dentures made out of?
Denture: Methyl Metharcrylate (MMA)
Clasps: Gold/Stainless Steel
What are advantages of chrome dentures?
Thinner Lighter Stronger - less coverage needed More durable (10 years+) Less Plaque retention Lower fracture rate Less staining
What are disadvantages of chrome dentures?
Additions difficult (unless planned for) More complex More expensive (casting) Conductive of hot and cold Slower (primary + master impression)
What are chrome dentures made out of?
Alloy of chrome and cobalt
What are advantages of valplast dentures?
Better Aesthetics Fast to fabricate Easier for single tooth Less muscle control needed than acrylic More expensive than acrylic Plaque retention Close fitting
What are disadvantages of valplast dentures?
Special cleaning products needed Stains Easily (Porous) Can't use free end saddle Very lab specific Special handpieces and burs needed to adjust chairside
What are valplast dentures made out of?
Biocompatible Nylon + Thermoplastic Resin
What features are examined when doing an extra-oral assessment of an existing denture?
- Type: partial vs full
- Material: acrylic, chrome, titanium, gold, valplast
- Denture experience
- Happy with fit/comfort
- Denture age
- Repairs/Additions
- Wear Patterns
- Denture Hygiene
What features are examined when doing an intra-oral assessment of an existing denture?
- Appearance
- Speech
- Designed
- Extensions: to palate/sulcus (Satisfactory/Under/Over)
- Retention: resist dislodgement (Satisfactory/Good/Poor)
- Stability on function (Satisfactory/Good/Poor)
- Neutral Zone Compatibility
- Freeway Space (IOD)
- Occlusion (CR, CO, Eccentric positions)
What material is used to do additions on acrylic dentures?
Cold Cure Acrylic
Are additions on acrylic dentures noticeable?
Yes, by differences in colour from different rates of staining
What is neutral zone compatibility ?
The potential space in the mouth for a denture between the lips/cheeks and tongue. Poor compatibility will affect mastication and risk of trauma
Adaptation to using dentures requires what 3 things?
Learning
Muscular Skill
Motivation
What are the 14 steps in denture construction?
- Examination + Treatment Planning
- Mouth Preparation
- Tooth Preparation
- Primary Impressions
- Special Tray
- Master Impressions
- Jaw Relations
- Denture Construction
- Check Fit
- Tooth Selection
- Try In
- Insertion
- Post Insertion
- Recall
How do you measure vertical dimension for pros?
Distance between tip of nose (Pronasale) and chin (ST Pog) using Calipers or Willis Gauge
How do assess if speech has been affected by the freeway space (IOD) created by an existing denture?
With denture fitted get patient to say words with S
- Inadequate Freeway Space: clicking of teeth on speaking
- Accurate Freeway Space: articulate S sounds
- Excess Freeway Space: Muffled/Unclear Words
What do we expect freeway space to be in Class I, II and III occlusion?
Class I: 2-4mm
Class II: 6-10mm
Class III: 1mm
How do you calculate freeway space?
IOD = OVD - RVD
Are bite records necessary for all RPDs?
No, if only a few teeth are missing then Centric Occlusion is well established.
What needs to be validated at a Try In?
Patient is happy with current tooth shade and bite
What diagnostic elements can be part of the initial examination?
- Chief Complaint
- Medical History: factors preventing insertion/cleaning
- Dental History: past denture experience, tooth loss, active disease
- Social History: reasons/attitude for denture
- Occlusion
- Study Models
- Radiographs - OPG of full dentition, PA of abutment teeth
- Referral to Specialist Prosthodontist
- Examination of existing denture
What is the purpose of a primary impression?
To create special trays to take the master impression
What are requirements for a good RPD?
- Good/Reliable Lab
- Good Impression taking skills
- Preservation of bone
- Inactive caries/perio
- Satisfactory Oral Hygiene
- Simple/Practical Design
- Patient cooperation/motivation
- Recall/Maintenance Protocol
Is masticatory efficiency improved by posterior RPDs?
No - reduced dentition will focus on mastication on remaining dentition. Replacing missing molars will help control direction of food bolus but does not added to chewing efficiency
What is the philosophy behind RPDs?
Perpetual preservation of what remains rather than meticulous restoration of what is missing
What is displaceable mucosa and why is it an issue for RPDs?
Overgrowth of soft tissue after bone levels from missing teeth shrink back.
Poses an issue because it is not a stable position for free-end saddles - denture movement occurs on contact
Can displaceable mucosa be treated?
Yes, it can be excised by an oral surgeon, but this could result in a bony ridge that is even less comfortable
What anatomy could pose issues for lower RPDs?
Shallow resorbed lower ridges
What anatomy could pose issues for upper Full Dentures?
High Palatal Roof - poor retention form (vertical)
Flat Palatal Roof - poor resistance form (horizontal)
What are anatomical restrictions for dentures?
Mandibular Tori Buccal Exostosis Overeruption Limited Neutral Zone Limited IOD
What denture would you use as transitional or permanent?
Transitional: Acrylic
Permanent: Chrome
What is a Free End Saddle?
Where there is no posterior attachment - only one anchor tooth
What is a Bounded Saddle?
Where are there are anchor teeth on both sides of the saddle
What are the disadvantages of a free end saddle?
Apply considerable pressure on gingival tissue
What is an Occlusal Rest?
A rigid extension onto an anchor tooth that has been prepared to receive it.
The Rest can be a naturally low marginal ridge, but more commonly is a prepared depression
What is the best way to prepare an occlusal rest?
Using a high speed round diamond in order to create a reproducible prep in both the patient’s tooth and master impression
What should a primary impression cover?
Maxilla
- Labial Sulcus including Frenum
- Maxillary Tuberosity
- Hamular Notch
- Hard Palate to the border of the Soft Palate
Mandibule
- Labial Sulcus including Frenum
- Retromolar Pad
What is involved with Primary Impressions and Record Bases?
- Alginate Impressions
- Pour Primary Cast
- Make Record Bases + Rims with CCA/Wax
- Chairside adjustment of Wax Rims
- Mounting on plane-line articulator
What are the different properties between Cold Cure Acrylic and Wax
Wax: more flexible, quicker
CCA: more rigid
What soft tissue factors need to be managed doing mouth preparation
- Nutrition
- Periodontal Treatment
- Tissue Distortion
- Denture Stomatitis (usually candida)
- Angular Cheilitis
- Surgical Issues: Retained Roots, Unerupted Teeth, Cysts, Tumours, Hyperplastic Tissue, High Frenal Attachment, Exostoses/Tori
What is the aim of mouth preparation?
Ensuring mouth is in a healthy and stable condition before commencing pros treatment
What are the objectives of tooth preparation?
- Increase stability
- No interference with opposing teeth
- Provide axial loading on abutment teeth
- Reduce undesirable undercuts
- Alter survey line for better clasp/reciprocal arm placement
- Create space for minor connectors, rests and clasp arms if insufficient occlusal embrasures
Is doing an occlusal rest on an existing crown a good idea?
No - uncertainty about the crown depth - likely to expose dentine
For a free-end saddle, where should an occlusal rest be located
On the opposite aspect of the anchor tooth to the saddle
For a bounded saddle, where should an occlusal rest be located
On the same side of the anchor tooth to the saddle
What should an occlusal rest also have?
Active buccal clasp below the survey line
Reciprocal lingual arm above the survey line
Why can’t you have a reciprocal lingual arm below the survey line?
Would prevent path of insertion
Where can you have a rest
Occlusal
Cingulum
What are the design sequence of a RPD?
- Saddle: replacing missing teeth
- Support: tooth/mucosal support
- Retention: how the denture stays in
- Connectors: how to join everything together
- Simplication: reduce plaque traps, optimal clasps
If a patient is happy with an existing denture fit but needs a replacement, how can you proceed
- Take an impression of the denture
2. Take an impression of the denture in the mouth
Where does a free-end saddle find it’s support?
Tooth + Soft Tissue
Where does a bounded saddle find it’s support?
Tooth + Tooth
What is the Kennedy classification for RPD?
Class I: Bilateral free-end Saddle
Class II: Unilateral free-end Saddle
Class III: Unilateral bounded Saddle
Class IV: Anterior Saddle
How is tooth support achieved?
On Abutment teeth via Occlusal Rests
How is mucosal support achieved?
Well adapted acrylic base that maximises coverage
Which arch would provide better mucosal support if you only had enough room on one arch
Mx (hamular notch) > Mn (retromolar pad)
How do you maximise mucosal support on a maxillary RPD?
- Buccal Flange
- Coverage over maxillary tuberosity to the hamular notch
How do you maximise mucosal support on a mandibular RPD?
- Buccal and Lingual Flanges
- Coverage over at least 1/3rd of retromolar pad
Are long bounded saddles tooth or mucosal supported or both?
Both Tooth and Mucosal Support
What is retention?
The property of the prosthesis to resist the forces of dislodgement along the path of insertion
What are the 5 methods of providing physical retention in RPDs?
- Cohesive Forces between molecules
- Adhesive forces between saliva and denture base
- Surface Tension (Wettability)
- Viscosity
- Border/Peripheral Seal
What is the implication of poor denture hygiene on retention?
Debris and plaque interfere with peripheral seal of the denture
What physiological forces can interfere with retention?
Interference from Cheek (Buccal Flange)
Interference from Tongue (Lingual Flange)
Poor muscle control (eg stroke victims)
Poor mucosal adaption (poor impressions)
What are the 3 types of forces aid retention for RPDs?
- Physical Forces
- Physiological Forces
- Mechanical Forces
What are the two types of clasps that provide mechanical forces to aid retention?
- Gingivally Approaching Clasps [Canines/Pre-Molars]
2. Occlusally Approaching /Circumferential Clasps [Molars]
What are some design considerations for clasps?
- Chrome clasp arm need to be 15mm in length to be resilient
- Undercut/Clasp tips must be at least 2mm clear of gingival margins
- Chrome clasps need to have an undercut depth of 0.25mm
- Stainless Steel clasps need an undercut depth of 0.75mm
What does a lab technician use to conduct surveying
Gibling Brothers Surveyor
What happens to any anatomy below the survey line?
Undercuts are blocked out by the lab tech to prevent blockages to the path of insertion
How is surveying done?
- Cast is mounted horizontallly
- Analysing rod determines path of insertion
- Survey rod marks the most labial survey
- Undercut gauge marks the 0.25mm undercut
- Undercuts are blocked out with wax
What are the 2 types of gingivally approaching clasps?
L Bar: more aesthetic, approachs distally
Y Bar: approach from midline
What is the issue with a Y bar on a canine?
Buccal bulge presses onto gum on compression
Where do occlusal approaching clasps originate from?
Extends from the Occlusal Rest + Saddle
What is the purpose of a reciprocal arm?
Prevents excessive force on tooth to prevent displacement forces by the action of the occlusal clasp
What are examples of Connectors?
Mid Palatal Strap Full Palatal Coverage Lingual Bar Lingual Plate Labial Bar
What are pros and cons with a lingual bar?
Pros
- Better biocompatibility: less of a plaque trap
Cons
- Less patient acceptability: sits in the floor of the mouth
When is a lingual plate used?
To support new anterior artificial teeth
How much room do you need for the lingual plate?
Top: 2mm below incisal edge of teeth
Bottom: 2mm before the floor of mouth
Can be used when less than 7mm distance between gingival margin + floor of mouth
How much room do you need for the lingual bar?
2mm above and below the lingual bar
7mm total between gingival margin + floor of mouth
When should a labial bar be used?
If mandibular teeth are heavily retroclined such that a lingual plate/bar would be undercut
What is involved with simplication?
Removing components that don’t compromise the final denture success.
What retentive features are used when supporting on a canine
Lingual Cingulum Rest
Labially approaching L Bar
What retentive features are used when supporting on a molar
Occlusal Rest
Occlusally Approaching Clasp
Reciprocating Arm
What is an indelible marking stick used for?
Marking where in the impression you want the special tray to end
How should you prepare a special tray if you’re using alginates?
Perforate the tray to allow alginate to flow
What are some characteristics of a special tray?
Constructed from primary coast Made of Cold Cure Acrylic Rigid Perforated for alginate Free of Undercuts Smooth and Rounded Centrally placed handle
How thick should the master impression be when using alginate?
Thickness of 2 wax strips
How thick should the master impression be when using PVS/PE?
Thickness of 1 wax strip
If there is a possibility of taking an impression of an undercut in a master impression, what material should you use
Alginate
PE/PVS the tray will get stuck!
How do you adjust a chrome base?
Usually in the lab
Chairside handpieces don’t have enough torque
What jaw position should dentures be made for in an edentulous patient?
In Centric relation
Assess RVD and ensure that will be adequate IOD remaining after
If there are insufficient oppositing teeth what things can be used to guage bite?
- Existing dentures
- RVD measurement and use of average IOD
- Speech
- Swallowing
- Patient Comfort
- Aesthetics
- Ridge Relations - Mx/Mn should be parallel
What materials can be used to take the bite record?
Wax, Zinc-Oxide Eugenol, Polyether, Silicone
What is squash-bite?
- Preforming 2 strip of pink wax
- Softening them against the study casts
- Softening them again to take record in patient’s mouth
What things are performed in Check Fit?
- Replicating Path of Insertion
- Removing any sharp edges
- Checking retention is adequate
- Adjust if poor seating
What 2 factors are important in tooth selection?
Tooth Shade: A-D
Tooth Shape + Size: Square, Ovoid, Tapered
What are some qualities about various tooth shades?
A: very white: good to use in full dentures - natural warm
B: has a bit of brown
C-D: has a bit of grey: often good to match older existing teeth
What materials are used to pour Study Casts?
Yellowstone
What materials are used to pour chrome Master Casts?
Glastone
What materials are used to pour acrylic Master Casts?
Greenstone
What is a checklist of things to check during a try-in appointment?
- Check extensions, retention, stability
- Check aesthetics
- Check position of teeth (neutral zone)
- Check occlusion
- Check speech
- Record adjustments
- Check patient satisfaction
- Send lab instructions
If a sore spot is not present but the patient has complained of this in the past, how do you check this clinically?
Insert the denture and use some pressure indicating paste
What patient instructions are important to convey during the insertion appointment
- Written and Verbal format
- Changes in speech
- Changes in eating
- Set expectations of adaption period
- Patient to practice insertion and removal
- Oral Hygiene instruction
- Denture Hygiene instruction: remove at night
What observations can be made a post insertion appointment?
Patient's problem list Pain (high/low pain threshold) Appearance Fit (loose/tight) Intolerance Denture Hygiene Oral Hygiene Patient's attitude and habits Excess Salivation Orafacial features with/out dentures - presence of any soreness/ulceration
How frequently are follow up pros appointments done
SADS: 2 weeks
Private Practice: 1 week
What is the recall frequency for a pros patient?
Every 6-12 months
