Test 1 Flashcards
Prosthodontics
Replacing missing or deficient teeth or other maxillofacial tissues.
What are the two different approaches to CD fabrication?
Remote: After extractions and healing.
Immediate: At the time of extractions.
What is happening to our population that indicates the importance of CDs?
Increased age of americans. 9 million Americans through 2030.
What is the overview of CD fabrication?
- Med/dent hx, panorex, interview and exam.
- Primary impressions. (make custom tray)
- Final impressions.
- Jaw relation records.
- Wax try-in of set teeth.
- Delivery of CDs and clinical remount.
- Post delivery care.
What is a general list of the relevant MX anatomy?
Residual alveolar ridge. Tuberosity. Hard palate with the mid-palatine suture and posterior nasal spine. Median palatal raphe. Rugae Incisive papilla Pterygomaxillary notch Vestibule (buccal and labial) Frena (bucal and labial)
Fovea Palatinae
May or may not coincide with the vibrating line. Useful landmarks.
Vibrating “ah” line
A clinically generated demarcation on palatal tissue at which movement occurs when the patient says “ah”. There is no soft tissue movement to the anterior of the line and is the posterior limit of the MX CD.
What is the posterior limit of the MX CD?
The Vibrating “ah” line
What muscles and structures define the MX CD borders?
Obicularis oris m Buccinator m Pterygomaxillary notches Coronoid process (MN) Vibrating line Frena
What are good areas to bear weight in the MN?
Retromolar pad and the buccal shelf.
What is the relevant MN anatomy for CD?
Retromolar pad Residual alveolar ridge Buccal shelf Genial tubercles Vestibule (buccal, labial, lingual) Frena (buccal, labial, lingual) Retromylohyoid undercut Tongue
What muscles and structures define the MN CD borders?
Obicularis oris m Mentalis m Buccinator m Genioglossus m Genial tubercles Mylohyoid m Superior constrictor m Palatoglossus m Masseter m Frena
Residual Ridge Resorption
On going process, very dynamic in the first 12 months after extractions. Mandibular is 4 times greater than maxilla. MX: from labial to the palate and vertical 3-4 mm. MN: Vertical and lingual 10+ mm
What are the primary areas of support for CDs?
The areas of the edentulous ridges that are perpendicular to occlusal forces, resistant to resorption, good mucosa type, quality and quantity of bone.
MX: Firm tuberosities, hard palate on either side of palatal raphe.
MN: Buccal shelf and retromolar pads.
What are the secondary areas of support?
Areas of the edentulous ridge that are greater than right angles or parallel to occlusal forces. The areas of the edentulous ridges that are at a right angle to occlusal forces, but tend to resorb under load. Residual ridge slopes, maxillary alveolar ridge, mandibular alveolar ridge.
Can the incisive papilla and mid-palatine suture bear a load?
No. They cause a lot of soreness.
What happens during the first patient visit?
Patient interview. Intraoral exam. Pre-prosthetic evaluation. Diagnosis. Prognosis. Preliminary impressions.
Who has a better chance of success? A first time denture wearer or a veteran denture wearer?
If the first time experience was good, a veteran. But if it was bad, a first time wearer.
What is the goal of the patient interview for a current denture wearer?
To determine if denture is inadequate or if patient is maladaptive. What don’t you like about current dentures? What are your expectations?
Realistic expectations.
Can be met and chances of success are reasonable.
Unrealistic expectiatons
Should be identified prior to initiating treatment, discussed and defused. NEVER PROMISE WHAT YOU CANNOT DELIVER.
What are some extenuating circumstances that may decrease the chances of success and the patient must be made aware of?
Poor residual ridge morphology. Poor history of denture adaptation. Systemic conditions and medications. Inoperable intra-oral conditions.
Tense facial muscle tone
Extensions are critical.
Average facial muscle tone
Slight overextension possible
Flaccid facial muscle tone
Maximum extension possible.
Small jaw size
Minimal supporting area.
Medium jaw size
Average supporting area.
Large jaw size
Maximum supporting area.
Arch Shape
Square is most favorable for retention and stability. Ovoid is slightly less favorable and tapering is the least favorable.
Arch height
Broad and high is the most favorable. Narrow and low is the least favorable
Residual Ridge Relationship Classes
Class 1: Average range of mandibular movement.
Class 2: Wide range of mandibular movement (A-P)
Class 3: Vertical chewer, establish sufficient distal occlusion.
Crossbite possible posteriorly.
Residual Ridge Parallelism
Parallel is ideal. If divergent, the potential for shunting of dentures occlusal plane is critical. Less likely for the dentures to slide anteriorly or posteriorly.
What is the ideal palatal vault form?
U-shaped.
Shallow/flat palatal vault
No resistance to lateral forces. Easily displaced by torquing. Good vertical support.
Rounded Palatal vault
Better resistance to vertical and torquing forces
U shaped palatal vault form
Best resistance to vertical and torquing forces.
V-shaped palatal vault
Difficult do to any vertical or torquing forces tending to break the seal, good lateral resistance but there is difficult adaptation of CD. There is a loss of support from the palate.
What are the 3 classifications of the palatal throat form?
I: Broad “ah” line area. More than 5 mm from the “ah” line to the drape of the soft palate.
II: Well defined “ah” line area. 2-5 mm from the “ah” line to the drape of the soft palate.
III: Narrow, 1 mm “ah” line. Less than 1 mm from the “ah” line to the drape of the soft palate. Placement of the post-dam is critical. No error is tolerated.
Gag reflexes
Normal, exaggerated (presents challenges to treatment), sever (successful treatment may not be possible)
Tongue size
Small and medium presents no special problems. Large has difficult impression process, difficult tooth arrangement and longer adjustment period.
Tongue Position
Normal: Most common, stabilized MN CD, apex lingual to anterior teeth.
Retracted: May affect anterior lingual seal. Lifts the MN CD, very maladaptive factor.
BIG DEAL
Functional mobility of the floor of the mouth
Highly mobile is difficult to establish lingual seal. Normal is most common. Relatively immobile is ideal for mandibular retention.
Lateral Throat Form: Neil’s Classification
I: Ideal. 1/2 inch or more from the mylohyoid ridge to retromylohyoid fold (lingual vestibule)
II: Average?
III: If the mirror jumps out of the mouth.
Saliva
Thick and ropy leads to a loss of retention. Need to use astringent rinse before impressions. Water is ideal. Lack of saliva is the worst scenario.
Lip Length/mobility
Normal leads to no special problems. However, if they are short/active the esthetics is critical. A gummy smile is very difficult to deal with.
Philosophical Patient
The best! Most healthy mental disposition. Can be reasoned with and sensible. Motivated in their treatment and adjusts most rapidly. POSITIVE RESPONSES.
Exacting Patient
Requires extreme care, effort, diligence and patience. Methodical, precise, accurate, demanding. Requires detailed explanation of each step. Often takes notes on what you say. Can be very successful because they are invested in the treatment.
Indifferent Patient
Questionable prognosis. Shows little if any concern/interest during the treatment. Apathetic, unmotivated, no ownership. All aspects of treatment may be problems after the treatment. Excuses. Don’t get good feedback.
Hysterical Patient
Highly emotionally unstable, excitable. Extremely apprehensive. Very unfavorable prognosis. Enlist additional help. Could be a cognitive deficient patient.
Traumatized Tissue can lead to….
Ill fitting dentures and improper occlusion.
Candida associated Denture stomatitis
A pathological reaction of the denture bearing palatal mucosa. Candida is a co-factor. Associated with an ill-fitting MX CD or continuous wearing of MX-CD. Hyperemic and hyperplastic changes with inflammation and infection.
Soft tissue treatment
Rest tissue for 24 to 48 hours and massage if mild case. Adjust occlusion and tissue conditioning with a soft liner.
Soft Liners
Used prior to final CD impression. Ethyl methacrylate with plasticizers. Can have short, medium and long term. May add an anti-fungal agent.
Examples of soft liners
Coe-comfort (tissue conditioners 4-5 days)
Coe-soft (Soft liner 2-3 weeks)
Lynal (soft liner and tissue conditioner 2-3 weeks)
Tissue conditioning
Using a soft liner and anti-fungal to improve soft tissue health prior to making a CD.
What topical treatments are used?
Mild to moderate stomatitis and candida infection.
Nystatin oral suspension. Nystatin vaginal tablets. Clotrimazole troches. Nystatin powder added to tissue conditioner.
What are systemic treatments used?
Severe cases. Itraconazole, Fluconazole, ketoconazole.
Radiographic findings
Retained root tips: may or may not take them out.
Embedded or impacted teeth: May or may not take them out.
Perceived pathology: Refer.
ALWAYS inform the patient of your findings.
Would you surgically resect a MX or MN anterior flabby ridge with movement?
Usually not because the resultant ridge would be nonexistent and you have more stability with it. Not a pathology. Simply because of resorption of the ridge.
What impression material consistance do you want?
Light weight.
Frena
Low: Away from ridge crest. Most favorable.
Average.
High: Close to the ridge. Least favorable. Presents challenges during treatment. Successful treatment may not be possible without surgical modification.
The proximity to the crest of the ridge has an impact on denture border.
Fenectomy. Get that shit outta there.
A MN CD can easily be compromised by a high attaching lingual frenum due to necessary modifications of the MN CD. Easily broken. Creates a weak point.
Epulis Fissuratum
Benign soft tissue lesion occurs in conjunction with an ill fitting denture border. The resultant tissue is reactive in nature. Failure to remove the lesion will compromise the denture fabrication and fit. Hyperplastic gingival tissue. Response of irritation. RESECT SURGICALLY.
Prominence of Maxillary Anterior Ridge
If labially prominent, may have to shorten the labial flange to avoid undercut. An alveoplasty is only recommended if it is severe.
Impacted or unerupted teeth
Is there associated pathology? Age and medical condition is a concern. Enough overlying bone? Most teeth are removed prior to CDs unless the surgery would create an anatomic defect detrimental to CDs. Ex: 3rd molars
Retained root tips
If deeply embedded in the bone, there is often no treatment. If close or exposed to the oral environment, you usually extract.
Large Maxilary tuberosities
Flabby tissue is usually resected. If there is inadequate clearance for denture bases, surgical reduction is required. If there are bilateral undercuts, you must reduce one side because they cause problems with the seals. If there is insufficient clearance for the coronoid process during MN opening, surgery is indicated.
Sharp spiny ridges and undercuts
Alveoloplasty is indcated. Usually come post extraction bony growth.
Exostoses
On the facial surface of the alveolar ridge. Need to surgically remove for a proper path of insertion for CDs and adequate peripheral seal.
Mandibular tori
Most should be removed and if present bilaterally they have to be removed.
Maxillary torus
If lobulated, undercut or extensive (to the vibrating line) they must be removed. However if they are small or flat, usually construct the CD over the torus.
What are the basic objectives of impression making?
Preservation of alveolar ridges. Support. Retention. Stability.
Preservation of alveolar ridges
You want to preserve them. DON’T USE HEAVY PRESSURE DUING IMPRESSION MAKING. You want to cover as much supporting tissue as possible to use the snow show effect, spreading the pressure across as much surface area. Minimizes soft tissue abuse and bone resorption.
Support
You need resistance to vertical forces of mastication and to occlusal (non chewing) forces applied toward the basal seat.
Primary areas of support
At right angles to occlusal forces and don’t easily resorb.
Secondary areas of support
Greater than right angles to or parallel to occlusal forces. Tent to resorb.
What are the Maxillary primary and secondary areas of support?
Primary: Firm tuberosities. Hard palate on either side of the raphe.
Secondary: Residual alveolar ridge and all ridge slopes.
What are the mandibular primary and secondary areas of support?
Primary: Buccal shelf and retromolar pads.
Secondary: Residual alveolar ridge and ridge slopes.
Retention
Resistance to removal in a direction opposite to its insertion. Resistance to vertical displacement. Resists adhesiveness of foods, force of gravity and forces associated with jaw opening.
What are some factors of retention?
Adhesion. Cohesion. Interfacial surface tension. Mechanical locking into undercuts. Peripheral seal and atmospheric pressure. Oral and facial musculature.
Adhesion
Physical attraction of UNLIKE molecules. Saliva is an adhesive agent and sticks to the denture base and mucous membrane of basal seat. It is dependent on close adaptation of denture, size of the denture bearing area and saliva type. The best type of saliva is thin but containing some mucous components.
Cohesion
Physical attraction of LIKE molecules. Works within the saliva between the denture base and the mucosa. The saliva needs to be thin. Works to maintain the integrity of the layer of fluid.
Interfacial Surface Tension
Cohesion + Adhesion. Resistance to the separation of denture base and supporting tissues. FUNCTION OF SALIVA. Combines the actions of cohesion and adhesion and is similar to capillary action. Saliva film needs to be thin and even and you need an excellent impression to get superior denture base adaption to undistorted soft tissue.
Mechanical locking into undercuts
Existence of modest undercuts can enhance CD retention. (retromylohyoid undercut, labial to anterior ridges, lateral to tuberosities) Access to undercuts is achieved do to resiliency of mucosa and submucosa. Clinically effective only if proper internal relief is provided and suitable path of insertion and removal is employed with minimal soft tissue distortion.
Peripheral seal
Positive contact of the entire perimeter of the denture base to the mucosal tissues. The function of the physiologic border molding is to establish the seal.
Atmospheric Pressure
When a force is exerted perpendicular to and away from the basal seat of properly extended and fully seated denture, pressure between the prosthesis and basal tissues drobs below ambient pressure, resisting displacement of the denture.
Retention an atmospheric pressure are directly proportional to the area covered by denture base and yield good suction.
Oral and Facial Musculature
Important to shape polished surfaces so that they are a series of favorable inclined planes in relation to lips cheeks and tongue. Each inclined plane comes into contact with a muscle at an angle that pushes the denture into place.
Tongue on lingual of MN CD. Buccinator on facial of MX/MN CDs.
Stability
Ability of the denture to remain in place when subjected to horizontal movements. Requirements for good stability include: Good retention, great ridges. Non-interfering occlusion. Proper tooth position in relation to ridge. Proper form and contour of polished surfaces. Proper orientation of occlusal plane. PATIENT FACTOR: GOOD MUSCULAR CONTROL AND CORDINATION.
What are the goals in making final impressions?
Excellent tissue health. Properly extended custom tray. Anatomically correct, physiologically formed borders=clinical border molding.
What are the functions of the border molding?
Seeks to extend the denture flange physiologically. It is not to correct tray deficiencies. Creates a retentive peripheral border seal. Facilitates proper tray orientation intraorally when seating the tray for the final impression. Carries the impression material to the vestibule.
Clinical Maxillary Border Molding
Anterior: Kiss function. Lip elevated and extended out.
Buccal: Cheek moved backward and forward to mimic fibers of buccinator muscle.
Posteriorly: Have patient open wide, move mandible from side to side, activate the coronoid process.
Clinical Mandibular border molding
Labial flange: Kiss function.
Buccal frenum area: Same as MX
Posterio-laterally: Cheek pulled upward and inward. Ask patient to close while you stabilize tray with downward pressure. Masseter muscle notch.
Anterior lingual flange: Patient protrudes tongue and ask them to push against your thumbs (rest on handle with resistance). Lick upper lip side to side.
Mid lingual flange: Protrude tongue, make a “k” sound.
Distal lingual flange: Protrude tongue, ask patient to close while you seat tray with downward pressure.
Postero-medial border of retromolar pad: Open wide.
Goals in making final impressions
Uniform space for impression material. Clinically formed “stops” in the tray. Dimensionally stable materials. Accurate reproduction of intraoral anatomy.
Techniques for Final Impressions
Functional or Dynamic: Pressure applied to entire ridge.
Mucostatic: Passive, no pressure
Selective pressure.
Impression with Pressure
Usually a closed mouth technique. Patient applies pressure on occlusion rims or existing dentures (functional). Patient executes muscle actions. Materials used: Impression waxes or tissue conditioners.
Light “biting” pressure is used in reline impressions for CDs.
Rationale: Denture retention is severely tested during mastication, so you use the same amount of pressure as during chewing.
Criticism: Presumes occlusal loading is the same during impression making and function. Constant pressure during impression may overstress tissues.
Mucostatic Impression
Open mouth technique. No pressure on bearing tissues. No attempt to produce a border seal. No attempt to border mold. Use oversized tray for first impression. Mucostatic paste impression material (impression plaster) and borders are determined on master cast.
Rationale: Creates a cast with excellent potential for interfacial surface tension. Ideal for retention.
Criticism: A truly non-pressure impression could only be obtained by sacrificing ideals of maximum ridge coverage and border seal. Functional stress is concentrated in smaller surface area.
Selective Pressure Impression
Combines extension for maximum tissue coverage with selective pressure (intimate contact) Applied to pre-determined primary stress bearing areas (stops) and the border seal. Open mouth technique. Use tray with tissue stops and adequate relief. Selected pressure on primary force/stress bearing tissues (“stops”) and peripheral seal. Physiologic border molding is a functional component of this technique.
Problems with final impressions that often lead to remakes
Failure to fully seat the tray short of the vestibule creating “wings of impression material”. Failure to cover borders with impression material. Inadequate amount of impression material causing voids. Excessive seating pressure creating “show through” pressure areas. Incorrect tray position in the mouth often due to excessive impression material. Too anterior, posterior or lateral with uneven borders that are too thick or too thin.
Alginate
Also called irreversible hydrocolloid. Used for preliminary impressions.
Reactor: Calcium Sulfate dihydrate.
Retarder: Sodium Phosphate
Accelerator: Potassium titanium sulfate.
Must use adhesive or perforated metal trays.
Material must be a uniform bulk 3-6 mm thick.
The set impression is 80% water meaning it is very unstable and you must disinfect and pour within 5-10 min.
Don’t alter water:powder ratio. It has a deleterious effect on physical properties impairing tear strength and elasticity.
Recommend to be removed from the mouth 3 minutes after gelation. Doubles compressive strength during the first 4 minutes.
Easily distorts.
Imbibition
The imbibing of moisture into the alginate causing the distortion.
Syneresis
The release of moisture from the alginate causing distortion
What are the different types of dental plaster and stone?
I: Impression
II: Model
III: Dental stone
IV Dental stone with high strength and LOW expansion (resin rock). 5000 psi after 1 hour.
V: Dental stone with high strength and HIGH expansion (die Keen). 7000 psi after 1 hour and 18,000 psi in 24-48 hours.
Impression compound
Made up of waxes, thermoplastic resins, acids and fillers. Green has the lowest fusion temperature at 122 degrees. Black is the highest fusion.
Advantages: Easy to use, inexpensive, rigid when cooled, adhesive sticks well to it.
Disadvantages: Poor dimensional stability over time. Technique is clinically sensitive. too hot or too cold. DON’T OVER HEAT.
Tissue Conditioners and Soft Liners
Plasticized acrylic resins.
DIBUTYL PHTHALATE.
The plasticizer, a large molecule, interferes with the entanglement of polymer chains allowing them to “slip” past each other. This permits rapid changes in shape of the soft liner for up to 24 hours. This defines their use as functional final impression materials. Must wait 24 hours before pouring the reline impression.
Plasticizers leach out resulting in rigidity.
Silicone liners are poorly adherent to the denture base, undergo significant volumetric changes with a gain and loss of water. There is a high friction coefficient that is detrimental with xerostomia.
Can’t effectively clean them. Use gentle soft brush and water. Eventually have bad tastes and odors. Debris accumulate in pores and support microbial growth.
Time use guideline
Coe Comfort 4-5 days
Coe Soft 2-3 weeks
Lynal 2-3 weeks
Durabase Soft 4-6 months
What are the 5 stages of setting?
Sandy, stringy, dough like, rubbery, set.
Denture Resins
Heat activated denture denture base resins used in lab step of processing. Compression molding technique. Used for the bases of CD.
Powder (polymer): Prepolymerized spheres of poly methyl methacrylate and initiator benzoyl peroxide.
Liquid (monomer): Unpolymerized methyl methacrylate and inhibitor hydroquinone. The cross linking agent is glycol dimethacrylate.
Polymerization shrinkage: 3:1 polymer:monomer mix results in a 6-7% volumetric shrinkage. Because it is uniformly distributed, denture base adaption is not compromised.
Porosity is caused by: Vaporization of non-reacted monomer too much heat, too fast. Incomplete mix of polymer/monomer. Inadequate pressure during molding. Air inclusions during mixing. Leads to voids that are physical, esthetic and hygienic problems.
Expand with water and saliva absorption. Slight shrinkage when they dry out. Low thermal conductivity. Low solubility in oral fluids.
Lucitone 199
High impact denture base resin. Due to addition of Styrene Butadiene. It is a rubber material so you drop it and it doesn’t break.
Denture Teeth
Acrylic, vinyl-acrylic or composite resin. High degree of cross- linking which makes them very strong.
Most are made of poly-methyl-methacrylate.
Resin vs. Porcelain denture teeth
Resin: Greater fracture toughness, easier to adjust, chemically bonded to denture base.
Porcelain: Abrasive to enamel and gold porcelain. Require mechanical retention to denture base. Better color stability and wear resistance.
Ideal properties of elastomeric impression materials
Accuracy Elasticity Dimensional stability Flow Flexibility Patient comfort
Large molecules with weak interaction. Two component systems which provide polymerization and or cross linking by chemical reaction.
Elastomeric Impression Materials
Polysulfide. Rubber base. Condensation reaction in which lead dioxide is the catalyst and water is the by product. Pour no less than 10 minutes but within 60 min. Mix equal lengths of catalyst and base to a streak free consistency. Use with custom tray.
Best surface detail. Ample working time. Thixotrophic meaning upon pressure it flows better. Excellent tear strength and it can remove undercuts.
Messy and poor odor. Has to be poured within 60 min. Potential for significant distortion. One shot impression, not modifiable. Must use a border molding material.
Polysulfide 2 min rule
Mix for 2 min until streaks are blended. Place in tray and sculpt for 2 min until the material stops being “runny” then place in mouth and muscle trim for 2 min. Out down in forward back, out up in forward back. Tongue movements. Last two min: O for maxillary impression. Tongue out to upper lip for MN impresson.
Addition Silicones
Vinyl Poly Siloxane. Addition reaction of base and catalyst. No reaction by-products and very stable. most popular.
Border mold custuom tray with impression compound and final light or medium body wash impression…
OR
Border mold custom tray with heavy body wash or putty material. Correct the tray and the first impression for pressure areas/extensions with light body wash.
Fine detail reproduction. Best elastic recovery, allowing for second pours. Excellent dimensional stability. Patients like it.
Expensive. Best in a dry field. Flash set. Rigid. Not as good of tear strength as the polysulfide in the stress, stretch recoil phenomenon.
Polyether
Addition reaction with base and catalyst. No biproduct. Different viscosities. Used similarly to the vinyl poly siloxane.
adequate tear strength. Slightly hydrophilic. Bitter taste but fastest set time. Immediate dimensional stability. Very accurate.
Very expensive. Fluid absorption and leaching of plasticizer compromise long term dimensional stability. High rigidity making it hard to remove from intraoral undercuts.
How are maxillomandibular relation records used in CD fabrication?
Used to determine lip and facial support. verify the plane of occlusion. Establishes a reasonable vertical dimension of occlusion (VDO) Make the CRR. Transfer info to an articulator.
Arch form or Neutral zone
Tooth and supporting structures occupy a position of equilibrium among the tongue, cheeks and lip muscles. You make the record base and wax rims within these limits.
Lip support
Need to establish unstrained lip support from all angles.
Older male adults: Length of MX rim should be as long as the length of the upper lip.
Female patients: MX rim should extend 1-2 mm below the lip.
Labial-incisal 1/3 of MX rim supports the superior border of lower lip. Wax rim should contact wet-dry line (vermilion border_ of lower lip during fricative sounds. (F’s and ph’s and v’s)
Camper’s line
A line from the ala of the nose to the tragus of the ear bilaterally. Check the parallelism of wax rim to the camper’s line (occlusal plane) using fox plane.
Inter-pulpillary line
Should be parallel to the rim. Check with Fox plane
After the proper occlusal plane as been established, what happens next?
Facebow transfer and the maxillary cast transferred to the articulator for mounting. Transfer midline!
Objective of the facebow transfer.
To record the position of the MX arch as related to the opening axis of the mandible and transfer this position to the articulator.
Commissures of the mouth
MN wax rim should be level with these structures with the mouth slightly open.
Tongue
The sides of the tongue should rest just above the lingual edge of the MN occlusal plane.
VDR
Vertical Dimension of Rest. Vertical dimension of the face with the jaws in an unstrained rest relation and the teeth apart, not touching. Say “emma emma m” then relax and hold the position.
Unstrianed Upright Head positon
Where you measure VDR. It is an arbitrary # of mm’s depending on the placement of facial reference marks.
Vertical Dimension of Occlusion
VDO. Vertical dimension of the face when the teeth or rims are in contact in CR. The numeric value of VDR and VDO change with the location of facial marks.
VDR vs VDO
Teeth do not touch at rest VDR. Touch after 2-4 mm of MN closure to VDO. The 2-4 mm is the interocclusal distance or space dependent on the posturing of the MN. Must be present. Adjust rim to give the patient it. MX rim has already be contoured so only the MN is altered.
VDR - 2-4 mm = VDO
Acceptable VDO
Patient should be able to swallow comfortably in CR and can’t swallow in protrusive posture.
Phonetics
Fricatives, silibants, Th’s, pronunciation.
Speaking space
1-2 mm between the incisal edges of the anterior teeth. Posterior don’t contact either.
Centric Relation
Reference point for jaw relations. Verifiable and reproducible. A functional position at the end of swallowing. The starting point for all CD occlusions.
Guides for Anterior tooth selection
Pre extraction record such as photos, diagnostic casts, old xrays. Existing dentrures. Facial characteristics, sex, personality, age, hair and skin color, arch size and shape, preferences.
Size of teeth
Mark rims at the junction of the commissure of the lips. Represent the distal and proximal surface of the canines and can me measured in mm. Used to choose teeth.
Square tooth molds
Angular. Central incisor is dominant and the gingivo-incisal curvature is moderate. Offers maximum light deflection. Bold.
Tapering Tooth molds
Characterized by rounded contours which taper towards the cervical ridge. Moderate gingivo-incisal curvature. Larg triangular incisor.
Ovoid
The teeth have a pronounced gingivo-incisal curvature which tends to disperse the light relection and create as soft appearance.
Soft Characteristics
Rounded arch form and tooth corners. Curve of MX anteriors closely follow the lower lip. Laterals overlap centrals. Smaler laterals and cuspids with sharp canines.
Bold Characteristics
Angular outlines. Larger lats and canines. Square arch form. Centrals overlap laterals. Blunt canines.
Sex and age factors
Feminine: tapering and ovoid.
Masculine: Square
Age: Tooth wear may result in #6-11 being close to the same length in older patients. Labial surfaces are flatter and the outlines are more square.
Length of teeth
Manufacturer. Lip line. High lip line need a longer tooth to avoid the gummy smile.
Color of teeth
Patients choice. We only make recommendations.
Posterior tooth selection
Size and number determined by the existing space between the canines and the tuberosities MX and retromolar pads MN. Form. No conclusive evidence supports one posterior tooth form over another.
Anatomic or semianatomic posterior teeth
Cusped
Non anatomic posterior teeth
Non cusped
Anterior Maxilla pattern of resorption
Labial towards lingual. Never place anterior teeth directly over resorbed ridge.
Max Central Incisor
Incisal edge is located .05 mm below the occlusal plane. Slight distal tilt to the perpendicular. Facial surface is nearly perpendicular to the occlusal plane with the neck very slightly depressed. Even labially with wax rim.
Max Lat Incisor
Incisal edge is .5 to 1 mm above occlusal plane. In line with max rim. Slightly more distal tilt in frontal view. Slightly more depressed than the central.
Canine
.5 mm below the occlusal plane even with central. Neck leans distally and is prominent as it supports the corner. Distal surface isn’t visible from anterior view. Long axis is almost vertical. 2 planes. Mesial follows anterior. Distal follows posterior.
A-P compensating curve
Curve of spee
M-L compensating curve
Curve of Wilson.
Mandibular Anteriors
Long axis of central incisors are perpendicular to the occlusal plane. Lateral incisors are set with slight distal inclination. Canines have even more distal inclination. Tip of incisal edge is slightly labial. Depress the neck of the tooth. .5 to 1 overbite. 1-2 mm overjet.
Incisal Guidance Angle
Determined by the vertical/horizontal overlap and is equivalent to the incisal guide table sagittal setting.
Distoincisal angle
Points in the direction of the crest of the posterior residual ridge.
Balanced artculation
The bilateral, simultaneous, anterior and posterior occlusal contact of teeth in centric relation and eccentric positions (built from a CR starting point)
Anatomic
Cuspal inclines of 30-40 degrees.
semi anatomic
Cuspal inclines of 10-22 degrees.
Anatomic and semi-anatomic advantages and disadvantages
Positive interdigitation of cusps. Esthetically resembles natural dentition. All CD occlusions should be balanced. Some shearing ability. Employs A-P and M-L to achieve bilateral balance.
Setting denture teeth is challenging. Less adaptable to arch relation discrepancies. Inclines cause horizontal forces. Balance of occlusion can be compromised by settling of bases.
Lingualized
Cuspal inclines of 15 degrees. Dominant MX lingual cusp and uncomplicated MN central fossa create a mortar and pestle contact. Good esthetics. Occlusal freedom/space. Centralized vertical forces. Minimized tipping. Good for patients with RRR. Beter bolus penetration? A-P and M-L.
Non-Anatomic
Cuspal inclines of 0 degrees. Minimal horizontal forces. Good for severe RRR. Occlusal freedom. Ease in setting and adjusting. No cusps to help with shearing. Reduce chewing efficiency. Lack of interdigitation. Relative esthetic compromise.
