Lecture 7_Gypsum Products

-gypsum= “chalk” or “plaster”, white powdery mineral Calcium Sulphate /

• formed through calcination —> heat applied to calcium sulphate dihydrate (gypsum) so water is evaporated to make crystallization calcium sulphate hemihydrate (dental stone/plaster)

• heated at 100-130 degree celcius

  • diff methods of calcination makes diff forms of calcium sulphate hemihydrate

    • beta-hemihydrate —> (110-120 C) large irregular shaped orthorhombic crystal particles with capillary pores

    • alpha-hemihydrate —> (125-130 C) also boiled in 30% aqueous calcium and magnesium chloride; small regularly shaped smoother and denser crystalline particles in the form of prisms and rods

• DISSOLUTION-PRECIPTATION THEORY= dissolution of hemihydrate and instant recrystallization of dihydrate followed by interlocking of the crystals to form the set solid

  • plater/dental stone when mixed with water will harden

  • the setting rxn: hemihydrate mixed with water —> fluid workable suspension formed —> hemihydrate dissolves and saturates solution —> dihydrate precipitates and nuclei of dihydrate crystals appear and grow and interlink (crystallization) —> crystals take up more space and continue to exapnd creating a exothermic reaction

-classification of gypsum products

• -classification of gypsum products

  Beta-hemihydrate	Alpha-hemihydrate
  Type I - impression plaster	Type III - dental plaster
  Type II - model plaster	Type IV - die stone (high strength/ low expansion)
  	Type V - die stone (high strength/ high expansion)

• Type 1 Impression Plaster

  • plaster of paris with modifiers to regulate setting time and setting expansion

  • used as final impression for full dentures

  • compression strength 580 psi

  • setting expansion 0.15%

• Type 2 Model Plaster

  • used for flasking complete dentures, mounting models, or plaster cast for provisional fabrication

  • compressive strength 1300 psi

  • setting expansion 0.30%

• Type 3 Dental Stone

  • aka yellow stone, microstone, orthostone

  • used for diagnostic cast, opposing arch cast, removable prosthodontics, orthodontic models

  • compressive strength 3000 psi

  • setting expansion 0.20%

• Type 4 Die Stone

  • aka “fuji rock”

  • used for dies fabrication of crowns, fpd, and implants

  • w/ added borax and potassium sulphate to reduce expansion; high strength, low expansion

  • compressive strength 5000 psi

  • setting expansion 0.10%

• Type 5 Die Stone

  • aka “die keen”

  • (Die-Keen Green Die Stone) was used in class; 13mL water for 60g of powder. ALWAYS add powder to the water

  • used for dies for crowns and FPD

  • high strength, high expansion (high expansion will compensate for the casting shrinkage)

  • compressive strength 7000 psi

  • setting expansion 0.30%

***dental investment material= when plaster is mixed with fillers such as phosphate or silicate

-physical properties of dental gypsum products

• water/powder ratio (W/P)

  • theoretical w/p ratio needed for chemical rxn of crystallization for 100g of powder (gauging water-water for 100g of powder)

  • gauging water= extra water need for workability

    • once gauging water evaporates, porosities will form

  • less gauging water —> stronger and denser material

  • note: type V die stone requires lowest w/p ratio and has the most strength

  • 

  • 

• mixing time (MT)

  • defined as time from the addition of the powder to the water until the mixing is complete

  • can use vacuum mixing (20 to 30s; helps rid porosities) OR hand-spatulation (60s for smooth homogenous mix)

  • combo: handmix 15s —> vacuum mix 20-30s

• working time (WT)

  • time available to use a workable mix that maintains a uniform consistency for mixing and pouring before setting

  • approx. 3 min working time is considered adequate

• setting time

  • defined as beginning of mixing until material hardens

  • 

  • loss of gloss= excess water in rxn is taken up to form dihydrate and mix loses it gloss; occurs at 9 mins from begin of mixing

  • initial gillmore= gillmore needle no longer leaves mark on surface; occurs at 13 min

  • vicat setting time= time elapsed until needle with weighted plunger no longer penetrates to bottom of the mix is known as the setting time

  • final gillmore= elapsed time at which the larger needle leaves only a barely perceptible mark on the surface is the final set; occurs 20 mins

  • ready for use= the set material may be considered ready for use at the time when the compressive strength is at least 80% of that which would be attained at 1 hr; occurs 30 mins

    • retarders —> added to increase setting time by reducing gypsum solubility and inhibiting growth of crystals (ex: borax, potassium citrate)

    • accelerators —> added to increase setting time by increasing solubility (ex: gypsum, potassium sulfate)

    • 
      

• setting expansion= crystals of dihydrate will form, grow, take up space and lead to expansion

  • rxn is exothermic; max heat @ time of final setting

  • maximum rate of setting expansion occurs at time when temp is increasing most rapidly

  • some accelerators or retarders have ability to reduce setting expansion (aka anti-expansion agents)

  • hygroscopic expansion

    • setting occurs under water

    • expansion will almost double

    • used for dental investing materials when casting metal where investment ring is immersed in water during setting

    • that additional expansion will compensate for the metal shrinkage

    • base metals will shrink more than low-Au metals

  • thermal expansion

    • increase in dimension of a set investment due to increasing temperature

    • occurs during burn out lost wax technique for casting metal

    • additional expansion to compensate for the metal shrinkage

-Wet and Dry Strength

• wet strength —> when excess water required for hydration of the hemihydrate is left in test specimen (wet 1 hr)

• dry strength —> measured when excess water in specimen has been dried off (day 24 hrs)

• dry strength is 2-3 times higher than wet strength

-Properties of the Set Gypsum Material

A) Compressive Strength

• lost excess water by evaporation creates increased strength where dissolved dihydrate precipitates and interlinks the crystals of gypsum

• what increases strength of gypsum: (and therefore decreases porosity)

  • the porosity of the set material —> alpha-hemihydrate finer particles

  • W/P ratio —> less water needed for the mix

  • more homogenous mix

  • longer time to dry out after setting

B) Flexural Strength

• gypsum is very brittle

• plaster is fragile with low value of flexural strength

• stone is less fragile but must be treated with care to avoid fracturing; it is relatively rigid but has poor impact strength

C) Dimensional Stability

• dimensional stability is good

• following setting. further changes in dimensions are immeasurable and the materials are sufficiently rigid to resist deformations when work is being carried out upon them

D) Solubility

• dihydrate (set plaster) is slightly soluble in water; solubility increases with temp

• if hot water poured over plaster cast, the surface layer dissolves and will be roughened

E) Detail Reproduction

• Types I, II detail reproduction of 75 micrometers

• Types III, IV, V detail reproduction of 50 micrometers

• note: PVS material is more accurate than dental stone (<25micrometers)

-Manipulation of Gypsum Products

• Proportion of Water and Powder

  • use correct W/P ratio; strength of stone inversely proportional to amount of water used for mix

  • add powder to water to ensure good wetting and avoid clumps and air bubbles

  • gypsum residue in mixing bowl can reduce working time and setting of stone; clean spatula and bowl before use

• Mixing Time and Technique

  • Vibrating the gypsum mix to bring air bubbles to the surface

  • Hand mix for 15 seconds and vacuum mix for 20-30 seconds

  • improper mixing leads to air bubbles; fast spatulation will prevent this

• Compatibility with Impression Materials

  • alginate impression material is hydrophilic and will allow the dental stone mix to flow

  • PVS is hydrophobic; need surfactant to wet surface prior to pouring (de-bubble-izer)

• Pouring Stone in the Impression

  • add small amount of stone mix and allow to flow into details, use vibrating table to increase flow of mix and allow air bubbles to come to surface

  • continue adding stone mix until impression is filled, then add make base

• Separating Cast from Impression

  • allow stone to set; ready to use occurs @ 30mins

  • alginate impressions- must remove stone within 60 mins; but after 30 min setting period

  • PVS impressions- best to leave cast impression in for 24hrs to allow dry strength to occur (this important for thin/fragile dies)

• Trimming Casts

  • prior to trim, soak cast in slurry water for 10 mins; prevents dry gypsum from sticking to surface of cast

• Mounting Diagnostic Cast

  • make notches on base of trimmed diagnostic cast using Joe Dandy for mechanical retention

  • wet stone base to allow for plaster to adhere when mounting

  • use least amount needed (more plaster means more expansion) and avoid smoothing it with water

  • allow for initial core to completely set (24hrs), then add more plaster around core to fill in and smooth

Lecture 8_Anterior Teeth Crown Preparations

• Challenges and things to consider:

  • Esthetics

    • soft tissue management

    • preparation design

    • shade selection

  • Occlusion

    • anterior guidance

    • canine guidance

    • anterior overlap

Occlusion

• anterior max teeth will have MIP contacts on lingual surface; wheras posterior teeth MIP contact on occlusal surface

• anterior teeth DRAG mylar in MIP; whereas posterior HOLD mylar

• posterior teeth take majority of occlusal load

  • load is reduced by the distance from the fulcrum

• posterior teeth protect anterior in MIP occlusion

• Occlusion Determinants

  • 

  • posterior teeth partially influenced by joints and anterior guidance

  • anterior teeth greatly influenced by anterior guidance and less by TMJ

  • the closer a tooth is located to a determinant, the more it is influenced by that determinant

  • in protrusive mvmnt, the incisal edges of mandibular anterior teeth more forward and down along lingual concavity of maxillary

  • anterior guidance is 5-10 degrees steeper than condylar path in a sagittal plane; allows for disocclusion of posterior teeth

  • condylar inclination (posterior determinant) will influence cusp size in posteriors

  • anterior guidance (anterior determinant) will also influence cusp size of posteriors

  • vertical overlap: vertical distance max incisal edges extend over mandibular teeth when in MIP VS horizontal overlap: projection of teeth beyond their antagonist in horizontal plane

• Mutually Protected Occlusion

  • canine guidance protects posteriors in lateral excursive mvmnts through disocclusion

  • anterior guidance protects posteriors in protrusive mvmnts

  • posterior teeth provide vertical stops for mandibular closure and guid mandible into position for maximal intercuspation

    • take much of the occlusal load in MIP and protect anterior teeth from oblique forces in MIP

• Posterior Group Function

  • distribution of load in mandibular mvmnts working side contacts between posterior teeth

• Balanced Occlusion

  • bilateral, simultaneous, anterior, and posterior occlusal contact of teeth in centric and eccentric positions

  • used in complete dentures

• Note: in edge-to-edge, open anterior bite, class II, or class III occlusion cases there is no anterior guidance

  • our goal is to restore anterior teeth in a normal relationship and reestablish anterior guidance

Re-establishing Anterior Guidance

• increasing incisal length will increase vertical overlap

  • loss of anterior guidance and canine guidance may result in accelerated wear of anterior and posterior teeth

• modifications can be made in the diagnostic wax-up stage or provisionalization stage

Steps for Restoring Anterior Teeth

• Data Collection

  • facial analysis and photography/video

  • lip analysis

  • intraoral scanning or diagnostic casts

  • intraoral photography

• Wax-up and treatment planning

  • wax up should be morphological, esthetic, and functional on a duplicate of the diagnostic cast mounted in the articulator; done by student

    • changing occlusal table and morphology

    • alteration of the plane of occlusion

    • replacing a missing tooth with an implant or FPD

    • edentulous space opposing a tooth to be restored

    • replace missing tooth structure

    • esthetic alteration of teeth

    • changing axial contours

  • putty impression is made of the wax-up for an intraoral mock-up

• Mock-Up and Esthetic Prototype

  • esthetic evaluation

  • occlusion and function eval

  • speech analysis

  • set expectations with the pt

• Preparations and Provisional Restorations

  • photographic Documentation

  • shade selection or custom shade match

  • esthetic evaluation, diagnosis, and treatment planning

    • diagnostic wax-up mounted on articulator

    • putty reduction guides

    • putty for provisional restorations based on wax up

    • shell provisional based on wax up

  • once the wax up has been approved, the reduction guides will be fabricated based on the wax up, so that the tooth preps are based on the final restoration

  • tooth preparation is verified with reduction guides to achieve the exact required space for the final rest.

  • at the tooth preparation appointment, it is required to bring a PMMA shell for provisional restorations based on diagnostic wax-up cast

  • entire arch PVS impression is mandatory for anterior cases especially in multiple unit cases; (triple Tray dual arch cannot be used)

  • in cases that are difficult to match shade of a single anterior crown a custom shade match can be done by a lab shade technician for proper selection

• Material Selection

  • codes:

    • all ceramic restorations (PFZ and Lithium disilicate glass): CDT Code D2740

    • metal ceramic restorations (PFM): CDT Code D2752

  • 

  • 

  • can get natural characteristics through layering (PFZ) or through staining (LithDi)

    • esthetic outcome can be better controlled through layering over staining

  • PFZ

    • can be designed to have lingual surface in monolithic zirconia for strength and the layered porcelain for facial for esthetics

    • advantage: less lingual reduction needed and better strength

    • layered zirconia: more translucency, characterization, and better esthetics

    • multilayered zirconia: gradual monolithic block less translucency

  • PFM

    • when there is not enough reduction of the tooth preparation to provide proper space, the PFM restoration will be either over-contoured or the opaque porcelain will show through

    • more facial tooth reduction is required for PFM to provide space for the metal coping, opaque layer, body porcelain and enamel porcelain

    • incisal porcelain must be supported by the coping and should not exceed 2.0mml controlled cut back important to properly support the porcelain and prevent fracture

    • occlusal design PFM anterior teeth may be porcelain or metal

      • margin design for PFM is usually porcelain buccal margin for esthetics and lingual metal collar for strength

      • mandibular anterior teeth may have circumferential metal collar for added strength

Anterior Crown Preparation

Path of Insertion

• the long axis of max anterior teeth= slightly buccal and convergent toward midline

  • poi follows long axis of tooth and is parallel to midline

    • except max canine is slightly lingual and mesial

  • POI is tangent to the buccal middle 1/3 (facial hieght of contour); it does not follow the gingival 1/3 emergence profile nor the incisal 1/3

• buccal 1st plane will follow: POI (buccal middle 1/3); matches lingual wall first plane

• buccal 2nd plane will follow: facial incisal 1/3

Lecture 9_ IOS, Shade Selection & Bite Registration

IOS= intra-oral scanning of prep will be done using an intra-oral scanner

• advantages: more patient acceptability, accuracy, time-saving/speed, fewer appointments, communication with the patient and the lab, access to digital workflows, eliminate the use of impressions materials

• disadvantages: learning curve, cost and access, and limited acceptance by laboratories

Tabletop/ desktops scanners are used to digitalize casts

• have higher accuracy that intraoral scanners; less error from operator and higher precision

Types of Scanning Technology

• confocal: based on focused and defocused images at different depths; as the camera moves around and acquires different perceptions of the object, the software will be able to reconstruct the model (ex: Trios 3, iTero)

• stereophotogrammetry: 3D model is calculated using algorithmic calculations from different images; relies on passive light projects and is cheap to produce

• triangulation: applies calculation of the distance to a single point from two different points to calculate the position of the reference in the image (ex: Medit)

• active wavefront sampling: an off-axis aperture module will go around the camera and create a rotation of the poi, and the information captured by the camera will be recoded

Bite registration

• allows us to transfer the occlusion to the articulator

• the cases where pt is lacking posterior stops need a bite reg taken to verify the mounting to hinge articulator

• trimmed to remove all the details and only leave the cusp tips to ensure it properly sits; should have no tissue details affecting sitting of the material

• is essential in cases of multiple teeth and FPD cases

• bite registration for edentulous or unstable MIP positions will require record bases to take a bite reg and mount the cast

Color in Shade Selection

• visible light gives us the sense of sight; range of 400nm-700nm and sits between ultraviolet and infra-red

• different color will have different wave lengths

• Shade is divided into 3 components based on the Munsell system

  • Hue: colors in the visible spectrum of light (ROYGBIV)

  • Chroma: refers to the degree of saturation (intensity)

  • Value: refers to amount of white, gray, or black (brightness)

• CIE L*a*b* system

  • colors are judged relative to redness or greenness (a*) and yellowness or blueness (b*)

  • vertical dimensions is value (or lightness (L*))

  • 

  • 

  • the behavior of light with the tooth is affected by the tooth structure and architecture or the tissues

  • the restorative material will try to mimic the behavior of light compared to the natural dentition

  • the use of natural light will be inconsistent becuz it can be affected by the time of day, weather, or time of the year

  • metamerism= pairs of colored objects that DO NOT have the same spectral curve but appear to be the same color in a given light condition

  • color perception can vary from person to person and can be affected by red fatigue from gingival tissue, wearing bright lipstick/clothing, or from dehydration of tooth

  • can also have inconsistencies between brands of porcelains and between different batches of the same porcelain

  • When do we do shade selection?

    • before anesthesia

    • before rubber dam

    • two weeks after completion of a bleaching tx

    • after tooth has been cleaned/polished

    • before preparation

  • Shade Guides

    • all empirically derived

    • inconsistencies in manufacturer and custom shade guides due to restoration material being diff from shade guide material; no standardized method for measuring color

    • material specific shad guides can be more reliable than generic shade guides

    • Vitapan Classical Shade guide= industry standard since 1956

      • 

        • tabs arranged in HUE

          • A: red-yellow

          • B: yellow

          • C: grey

          • D: red-yellow-grey

        • CHROMA: arranged in numerical values

    • use area of tooth highest in chroma for hue selection; operator should select hue closest to natural tooth

    • VITA 3D MASTER

      • value oriented shade guide (bc rods more sensitive than cones); value is most important in shade selection

      • had better shade coverage than vitapan classic

      • shade selection order: value —> chroma —> hue

      • 

      • shades in the vita 3d master are named: value —> hue —> chroma (ex: 2M1)

    • a stump shade is essential for all cases made with all-ceramic restorations with an esthetic component

  • Spectrophotometer

    • able to measure color by analyzing the full spectrum of light collected on a given surface

    • works independently of light sources

    • intra-oral spectro. measure the colorspace (CIE lab) and correlate that to conventional shade guides

  • Photography

    • black and white: good for value selection

    • transmitted light: good for opalescence, mamelon design and enamel defects

    • conventional soft light: for surface texture and translucencies

    • crossed polarization: for shade selection, color maps, mamelon design

• custom shade match/selection is an option for complex cases; lab technician will do the shade match by themselves avoiding biases

• REMEMBER:

  • cervical area has more chroma than middle and incisal third

  • surrounding tissue will have an impact on the shade of the tooth

  • value decreases incisally while translucency increases

  • cervical area has slightly lower value due to increased chroma

  • less complex: posterior teeth, slight characterization, and multiple teeth

  • more complex: anterior teeth, highly characterized, single teeth

Materials

• opaque materials will have HIGH value, while translucent will have LOWER value (makes rest. gray-ish)

• staining of monolithic material will lower value

• it is always possible to lower value, so aim for higher value shades when selecting

• surrounding tissues will affect color of restoration

• LAYERING

  • allows application of multiple layers with different optical properties, allows mimicking of nature more precisely

  • PFM, PFZ, Lithium disilicate microlayered

  • **microlayering allows us to achieve highly esthetic and natural-looking restorations, maintainingg the mechanical properties of monolithic lithium disilicate

• STAINING

  • technique mainly used in monolithic rest that consists of “painting” the surface of tooth to give perception of natural optical properties

  • monolithic zirconia ( & multilayered mono zirc), lithium disilicate, leucite reinforced ceramics

Bonding

Lecture 10_Master Cast Fabrication

Items needed for fabrication and mounting casts:

• final impression for master cast fabrication, opposing cast for articulation in MIP, interocclusal record (bite registration)

Dual Arch Impression

• is a triple tray impression; captures the prepped arch, opposing arch and interocclusal record (bite registration) all in one tray

• indicated when stable MIP

• Single posterior unit to no more than two adjacent units

Full Arch Impression

• is a PVS impression of the prepped full arch

• indication:

  • cases of multiple units

  • edentulous arch unstable MIP

  • all anterior cases (sigle or multiple units)

  • all FPD cases (tooth replacement)

  • final restoration will support a future RPD (single of multiple units)

  • implant cases

• bite registration may be necessary

• opposing may be a duplicate of the diagnostic cast, or a new cast of the most recent opposing if treatment changed the initial case

Bite Registration

• for dual arch cases where single prepped tooth doesnt have both adjacent MIP stops

• for cases of multiple units or fixed partial dentures

• for casts unable to be hand articulated into MIP

• for cases of edentulous RPD cases with record bases or unstable occlusion

POUR UPS

• poured by student

  • dual arch OR full arch impressions for CAD/CAM rest (inlay, onlay, monolithic zirconia crowns)

• poured by lab

  • dual arch OR full arch for all cases of PFM,PFZ,Li-Si, Veneers

Master Cast w/ Solid Dies (for CAD/CAM cases)

• 

• dual arch impression for CAD/CAM (or monolithic zirconia crown) taken and poured up with type V die-keen stone- solid dies

  • opposing cast poured up with yellow stone and triple tray is mounted into hinge articulator by student

• OR full arch master cast poured up by student with die-keen stone and mounted on semi-adjustable articulator using bite registration

  • need opposing cast as well for mounting

• these mounted casts are used for scanning the arch with prepped tooth, opposing arch, and bite for digital articulation

• master cast should be free of voids; if not another die-keen should be poured for scanning and used as the solid cast unmounted

• if cast (pt) has missing teeth, either wax up the teeth or use denture mounted teeth on cast prior to scanning

• 

Master Cast w/ Sectioned and Pinned Dies

• all cases of PFM,PFZ,Li-Si, Veneers, CVC, or lithium disilicate

• what to send to lab to get master cast fabricated model back: impression (PVS), clinically current opposing cast (poured by student), and bite registration (if needed)

  • and then tell lab if they should mount it on hinge articulator (not for cases w. more than two units) OR if you will be mounting it on semi-adjustable

• what you get back:

  • dual arch impression and mast cast poured w/ die-keen and opposing cast mounted on hinge articulator by lab

  • 

  • OR full arch impression and master cast poured by lab with type V die-keen stone SECTIONED dies that student will mount with opposing

  • 

  • FIRST pour by lab will be of the MASTER CAST (most accurate) in Type V die stone

    • this master cast will be trimmed so its base is parallel to the occlusal plane and between 11-13mm thick (min of 9mm; measured from gingival margin to base of cast)

    • master cast will also have beveled edge to prevent yellow stone base from locking onto the die-keen cast

  • master cast then gets precise pin holes in base; done by Pindex Machine- a reversed drill press

    • dies can be repeatedly removed and replaced in their exact original position and are stable (antirotational)

    • cross pins are then glued to cast all parallel to eachother using Cyanoacrylate (superglue)

    • antiroational notches on both buccal and lingual sides of the pin are created; grooves should not reach pin and should not have undercuts

  • Super-Sep, a separating medium is applied for removal of master cast from dental stone base; is not applied to sleeves for pins

  • base is made w/ base conformer and type III dental stone (yellow stone)

    • this base is trimmed about 2mm to allow for exposure of pins

  • sectioning of die: pencil lines are drawn and Joe Dandy or saw is used to section die (this is why need that 0.5 separation)

  • (this full arch master cast is sent back to student for mounting)***

• Mounting Master Cast w/ Pinned Dies

  • student will create mechanical retention by making an ‘X’ on the dental stone base to be mounted with mounting plaster (note: pin holes should be covered with baseplate wax as not to get plaster in them)

  • mount that hoe

  • allow core of plaster to fully set before adding more plaster and smoothing everything out

  • 

• Die Trimming & Redlining

  • this is done by student

  • remove pindex die and trim its sides for easy removal and replacing into and out of mounted master cast

  • die is trimmed following root form (approx 3-5mm from root extension captured beyond margin during impression)

  • 

    • this ensure a proper buccal/lingual and mesial/distal emergence profile

    • this influences the axial contours of the wax pattern during margination wax application

    • over-trimmed dies= ditched die; these result in over-contoured restorations

  • redlining: line should be visible, thin, continuous, and regular following the finish line of the prep

    • must use solid cast as reference; die should be dry and free of debris

    • avoid thick red line (“lipstick”) or double line

    • 

  • errors in redlining or trimming of die —> trim another single die or redline and mark it specifically for the lab to use as the margination die for margination waxing

• Die Spacer

  • this step is done by lab technician

  • die spacer composition —> metal-oxide powders, adhesive, volatile organic matrix liquid

  • 4 coats of die spacer are applied on the axial and occlusal surfaces of the pinned die; none goes on margin

    • cyanoacrylate is placed over the redline margin for preservation of marginal finish

  • alternating colors are used for each coat and each coat measures 6um; 4 coats x 6um each= 24 um total of die spacer is required for the thickness of the luting cement

    • glass ionomer luting cements are required to have a film thickness of less than 25um according to ADA

• Lab Final Restoration

  • 

Lecture 11_Lab Prescription and Quality Assurance

• Whats being sent for quality assurance?

  • CAD/CAM cases master cast w/ solid dies fabricated mounted on hinge articulator by student

  • all other cases lab fabricated master cast w/ sectioned and pinned dies and cast mounted with dies trimmed and redlined by student

Prescription Form

• lab prescription form must be filled out by the student to include all necessary information

• STEP 1: restoration type

  • ex: single unit crown, inlay/onlay, FPD, porcelain veneer, other

• STEP 2: restorative material

  • ex: monolithic zirc, composite/ceramic, layered zirc (PFZ), Gold (CVC)

• STEP 3: PFM margin design

  • facial/lingual metal collar or circumferential collar

• STEP 4: PFM contacts

  • indicate material (metal or porcelain) for occlusal and inter-proximal contacts

• STEP 5: RPD abutments only

• STEP 6: FPD pontic design

• STEP 7: Shade

  • fill out shade guide used and include photos on flashdrive if taken or if custom shade match was done

• STEP 8:Additional Instruction

  • any additional notes like marked margination dies or occlusal islands or reduction guides

• STEP 9: Return to USC

  • what do u want back

  • 

• STEP 10: Approval by Supervising Faculty

  • faculty verifies and approves model work and signs

• STEP 11: Quality Assurance Faculty Only

Students Submits the case for lab quality assurance! 🙂

What to include?

• CAD/CAM Restorations Single Unit

  • PVS dual arch impression

  • mounted casts on hinge articulator

  • lab prescription filled out w/ step 10 signed

  • additional: solid die-keen cast

  • 

• Layered Restorations Single Unit

  • PVS dual arch impression

  • mounted pinned cast by lab

  • pinned die (margination die) trimmed and redlined

  • solid casts and single die

  • bite registration if used

  • lab prescription

  • additional: new margination die other than pinned die

  • 

• Anterior Restorations Sigle or Multiple Unit

  • PVS FULL arch impression

  • mounted master pinned cast from lab and most recent opposing cast on semi-adjustable articulator

  • pinned die (margination die) trimmed and redlined

  • solid casts and single die

  • bite registration if used

  • diagnostic wax up cast OR reference cast (approved provisionals) mounted on semi-adjustable articulator

  • reduction guides

  • photographic documentation

  • lab prescription

  • 

Your case may not be approved if:

• preparation erros

  • critical errors in outline, internal, retention, marginal finish

• impression erros

  • inadequate tissue retraction, moisture contamination

• dies and casts errors

  • overtrimmed or undertimmed dies and incorrect redlines

• articulation and bite registration errors

  • cast not mounted in MIP

• prescription errors

  • info missing in Lab Rx

• other errors

  • missing items

Final Restoration Returned to USC

*CAD/CAM cases are fabricated in-house at USC, while all other cases of layered restorations (PFM, PFZ, Li-Si, metal veneers) are sent to external lab

time to try-in that restoration

1. Restoration on Casts

   1. eval rest prior to pt appt

   2. check shade match, proximal contacts (solid cast), margins (untrimmed single die), and occlusion (master cast)

2. Restoration Intra-oral tryin

   1. proximal contacts-drag mylar

   2. margins-properly sealed

      1. clinically acceptable marginal discrepancy is max 120 um

      2. can use Fit Checker to improve the seating and marginal fit of the restoration

   3. occlusions-hold/drag mylar and check reference teeth

      1. Black articulating for MIP and red marks for excursive interference; only adjust red marks that are not covered by black on the restoration

   4. contours-proper contours and embrasures

   5. shade-pt approves and signs an esthetic consent form prior to cementation

***all adjusted surfaces must be polished with the extra-oral ceramic polishing kit; this protects oppsoing teeth from accelerated tooth wear

3. Restoration Cementation

   1. Treatment of the Restoration

      1. air abrade intaglio using aluminum oxide for 10 sec, rinse and dry, and use alcohol to clean internal surface

   2. treatment of the tooth surface

      1. isolate area, clean tooth with pumice, and scrub w/ CHX

      2. apply 20% polyacrylic acid for 10 sec, rinse and dry (do not desiccate)

   3. luting (cementing) restoration

      1. lightly coat intaglio with self-cure resin-modified glass ionomer luting cement (RMGIC)

      2. immediately seat rest w/ dynamic seating and spot check marginal seal with explorer

      3. bite on cotton roll for 4.5 min from seating of rest

   4. clean up and occlusion

      1. remove excess with explorer once cement sets, floss interproximal, remove chord if used

      2. verify occlusion in MIP and excursive mvmnts, adjust if needed

   
   

If your crown falls off… its likely there was not enough retention due to improper wall height and taper.

-in this case we may need to bond the zirconia but remember…