Clinical Sequence for Crowns

Appointment-by-appointment sequence for a single full-coverage crown. Every claim carries an inline source marker. Prep bur detail is deliberately not repeated here — see Molar Crown and Bridge Preparation Tips. For partial-coverage restorations see Clinical Sequence for Onlays and Overlays.

Where the visit boundaries come from

Four of the five vault sources describe this workflow as phases, not appointments: F8 Try in gives 5 phases, DMD2 L2 - Clinical Steps for Indirect Restos gives 7 steps, F5 Principles of tooth prep gives a 7-step workflow plus two flowcharts, DMD2 L1 - Principles of Tooth Prep gives 4 phases. Only Coals 3. Definitive (Reconstructive phase treatment) splits it into numbered visits, and it is the source of the visit boundaries used below. DMD2 L1 - Principles of Tooth Prep is a re-bracketing of the same Fu/Matsubara slides as DMD2 L2 - Clinical Steps for Indirect Restos — treat them as one model, not two.

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Visit 0 — Assessment, treatment planning and consent

Not a crown appointment as such; this is the consult the crown sequence hangs off. Coals 3. Definitive (Reconstructive phase treatment) omits it because it begins from an existing plan.

Is a crown the right answer?

Crowning is a last resort, not a routine

“Crowning is a last resort, not a routine procedure. You should only crown a tooth when it provides a clear advantage to the patient.” (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “Crowning as a Last Resort”)

Note the Fu/Matsubara lectures present crown indications as a six-item checklist with no last-resort framing (Source: DMD2 L1 - Principles of Tooth Prep — “Factors for Crown Consideration”). Newport’s position is the more conservative one.

Indications — destruction of tooth structure, aesthetics, plaque/moisture control, retention, finance, other prosthodontic requirements (e.g. survey crowns for RPDs) (Source: DMD2 L1 - Principles of Tooth Prep — “Factors for Crown Consideration”).

• Extensive loss of structure from large caries; cusp fracture in teeth with large existing restorations (e.g. MOD amalgam) (Source: F5 Principles of tooth prep — “Considerations for a crown”)
• Endodontically treated posterior teeth — “brittle and have lost structure from the access cavity”; full occlusal coverage “crucial to prevent catastrophic fracture” (Source: F5 Principles of tooth prep — “Considerations for a crown”). See Visit 0b.
• Loss of structural integrity such that matrix systems compress the tooth and cannot provide molding support; or inability to establish proper contours/contacts, producing open contacts and food impaction (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “General Principles and Strategic Considerations”)
• Strategic abutment support — a survey crown “acts like a ‘hat’ holding the tooth together as a single unit” (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “General Principles and Strategic Considerations”)

Contraindications

• Crowns “should not be placed solely to adjust occlusion” (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “Crowning as a Last Resort”)
• Root-caries-prone patients — “decay will simply progress underneath the crown margin”; significant in elderly patients with arthritis or tremors preventing effective flossing (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “Root Caries”)
• Poor plaque control — “It may be better to place a large direct restoration and monitor the patient’s hygiene commitment” (Source: F5 Principles of tooth prep — “Considerations for a crown”)
• No ferrule with subgingival fracture below bone level and no margin possible on sound tooth — extraction is the only viable option (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “fractured tooth - unrestorable”)
• Severe parafunction, low strategic value (e.g. non-strategic third molars) (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “General Principles and Strategic Considerations”)

Does a crown strengthen the tooth? The sources disagree

• No — “crowning does not strengthen a tooth—it merely gathers whatever structural weakness exists and holds it together temporarily” (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “Fundamental Principles: Does Crowning Strengthen Teeth?”)
• Yes — “A crown protects the remaining weakened tooth structure from further fracture under occlusal loads” (Source: F5 Principles of tooth prep — “Considerations for a crown”)

Both are defensible if you read “strengthen” as splint together rather than restore original strength — Newport’s own note calls the crown a “full-coverage splint”. The clinically useful version: a crown redistributes load off individual cusps, but it cannot add back what preparation removes.

Restorability

1. Remove all existing restorations first, to visualise the “negative tooth” (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “Essential Diagnostic Steps”)
2. Quantify remaining structure — how much tooth, how many cusps (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “Assessing Restorability”)
3. Transillumination for cracks or fractures in remaining cusps (same)
4. Pulp vitality testing; radiographic assessment of bone levels, root morphology, caries extent (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “Essential Diagnostic Steps”)
5. Decide margin location — margins must be on sound tooth structure, never ending on composite or GIC (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “Assessing Restorability”)
6. Establish strategic value and whether the patient can afford the whole sequence (same)

Decide margins before you cut, not after

A student “prepared a beautiful crown prep but forgot to remove the palatal filling, discovering only during preparation that the palatal margin was 2-3mm subgingival once the GIC was removed” — turning it into “a crown lengthening case unnecessarily.” (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “Case Study: The Missed Palatal Margin”) “Never tell a patient, ‘Oops, sorry, we need surgery to cut your gums to lower the margin.’” (same)

Prognosis bands (Samet & Jotkowitz) — remaining sound coronal tooth structure, where the single most severe criterion sets the class (Source: Classification and prognosis evaluation of individual teeth—A comprehensive approach — “Table 2: An evaluation of pathology and the scale of severity”):

Class	Coronal structure	Bone support	Meaning
A	80–100%	80–100%	Good — easily restored
B	50–80%	50–80%	Fair — no biologic width infringement, adequate ferrule
C	30–50%	30–50%	Questionable — ferrule only at the cost of crown-root ratio
D	<30%	<30%	Compromised, high risk of loss
X	None supragingival	—	Non-salvageable, extract

If a planned abutment grades C or D, “an alternative treatment plan should be considered” (same — “Discussion”).

Ferrule millimetres are not in the crown sources

Why to Crown a Tooth and Examples of Caries_integrated_integrated defines ferrule only qualitatively — “tooth structure above the gum line”, “360-degree encirclement of sound tooth structure”. The numeric requirements live in the RETT lectures; see Visit 0b. Do not read the 0.7 mm intracrevicular depth or 2 mm biologic width figures below as ferrule figures — they are margin-placement figures.

Alternatives to consider first

• Crown lengthening — biological cost “very high”. Interproximal is worst: “You lose supporting bone on both the tooth being treated and the neighboring tooth… sacrificing one tooth for the other.” Palatal has lower cost but is still undesirable (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “Crown Lengthening Considerations”). Cost ≈ $6,000forlengthening+definitiverestorationvs\approx$8,000 extraction + implant, and “many patients prefer the predictability of an implant” (same)
• Orthodontic extrusion — expensive, difficult with multi-rooted teeth, “Not normally indicated for molars” (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “Extrusion (Orthodontic Extrusion)”)
• Gingivectomy where sulcus probing depth >2 mm, to design a 1.5 mm sulcus (Source: F5 Principles of tooth prep — “Margin location”)
• Partial coverage — onlay, 3/4 crown, or a material needing less reduction. Full-crown preparation removes “approximately 70% of the volume of the clinical crown of a posterior tooth”, vs “only about 30% for an occlusal onlay” (Source: F5 Principles of tooth prep — “Conservation of tooth structure”; Edelhoff & Ahlers 2018, cited at DMD2 L1 - Principles of Tooth Prep — “Clinical Research Reference”)
• Sequential, conservative-first planning where finances are limited, with onlays and crowns later “as circumstances and finances permit” (Source: 11 11. The Definitive Phase of Treatment - ClinicalKey.pdf (p.749-856) — “Professional and Patient Considerations”)

Occlusal scheme decision — conformative or reorganised

Conformative — restorations in harmony with existing jaw relations, made to MIP; occlusal contacts on unrestored teeth unaltered. Most cost-effective, least intervention, “easiest and safest… less likely to introduce new problems.” (Source: L5 Clinical Examination of Occlusion — “Principles of the Conformative Approach”) It should be the first option considered (same — “Clinical Recommendations”).

Reorganised — altering the occlusal scheme to an ideal one, made to Centric Relation “because it is a reproducible position independent of tooth contact.” Requires extra stages using provisionals to design and test the new occlusion before the definitive prosthesis. (Source: L5 Clinical Examination of Occlusion — “Principles of the Reorganized Approach”)

Indications for reorganised: increased OVD required; teeth significantly malpositioned; repeated restoration failures in the existing scheme; absence of posterior contacts at the desired vertical dimension; current scheme dysfunctional or parafunctional (same — “Indications for the Reorganized Approach”).

For a single crown with a stable, functional occlusal scheme “a detailed assessment session may not be necessary” (Source: L5 Clinical Examination of Occlusion — “Treatment Planning Principles”).

Consent

• Warn that investigation may reveal the tooth is unrestorable; obtain consent documenting the worst case before dismantling restorations (Source: Why to Crown a Tooth and Examples of Caries_integrated_integrated — “Essential Diagnostic Steps”)
• Pulp necrosis after indirect restoration ≈ 5.02%; periapical pathosis ≈ 3.63% (Source: DMD2 L1 - Principles of Tooth Prep — “Risks of Indirect Restorations”). Chairside version: “about 10% of the teeth will have pulp issues, which means it might need endo” (Source: F8 Try in — “Patient communication”)
• Longer-run figure: “Between 3 and 25% of teeth prepared for full coverage crowns will lose vital pulp functions within 15–20 years, with previously compromised teeth faring worse” (Source: F8 Try in — “ABUTMENT TOOTH”)
• Risk factors for pulp necrosis include temporisation exceeding two weeks, eugenol-free temporary cement, polyether final impressions, GIC permanent cementation (Source: DMD2 L1 - Principles of Tooth Prep — “Risks of Indirect Restorations”)
• Set expectations for the provisional: “not strong and is cemented with temporary cement so it can be removed” (Source: F8 Try in — “Patient communication”)

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Visit 0b — Endodontically treated teeth (scope boundary)

Brief decision layer only. Full protocol: L1 Introduction To RETT, L3 Post and core fabrication techniques, L4 RETT Online.

Posterior ETT — cuspal coverage indicated. ETT with cuspal coverage had “six times greater rate of survival” than those without; ETT with crowns were lost after an average of 87 months vs 50 months without (Source: 35 Chapter 35 Contemporary Restoration of Endodontically Treated Teeth — “SHOULD CROWNS BE PLACED ON ENDODONTICALLY TREATED TEETH?”). Of teeth extracted after initial non-surgical endodontic treatment, 85% had no full coronal coverage (same).

Anterior ETT — crown not routine. “in anterior teeth, coronal coverage crowns did not significantly improve the success of endodontically treated teeth”; crowns are indicated only where the tooth is “structurally weakened by the presence of large and/or multiple coronal restorations” or needs form/colour change not achievable by bleaching, bonding or veneers (same).

Ferrule requirements (Source: L1 Introduction To RETT — “Ferrule Height” / “Ferrule Width” / “Ferrule Location”):

• Minimum height 1.5–2 mm; remaining dentine thickness 1–2 mm
• Requires 4–5 mm of tooth structure coronal to bone crest (2–3 mm biologic width + 1.5–2 mm ferrule)
• Ideal is 360°, but “an incomplete ferrule is a better option than a complete lack of ferrule”; for maxillary incisors the palatal ferrule matters most
• Non-restorable = 0 ferrule remaining (Source: L4 RETT Online — “Ferrule Effect and Mechanical Risk Assessment”)

Textbook corroboration: a 0.5–1.0 mm crown ferrule is ineffective, 1.5–2.0 mm effective; ferrules “are more effective when the crown encompasses relatively parallel prepared tooth structure than when it engages beveled/sloping tooth surfaces”; a crown ferrule beats a core ferrule (Source: 35 Chapter 35 Contemporary Restoration of Endodontically Treated Teeth — “DOES THE USE OF A CERVICAL FERRULE…”).

Decide the crown type before making the post and core

“the first step in the fabrication of a post and core should ideally be preparation of the coronal tooth for the type of definitive restoration that will be placed… Each type of restoration requires different amounts of tooth reduction, and the form of the tooth preparation varies considerably.” (Source: 35 Chapter 35 Contemporary Restoration of Endodontically Treated Teeth — “Coronal Tooth Preparation”)

Note L3 Post and core fabrication techniques — “Coronal Preparation Timing” presents this as genuinely two-sided: prepping first gives better canal visualisation and structure assessment but loses the original radiographic reference points.

Effect on visit count

Core type	Extra visits	Where it happens
Direct (prefabricated post + chairside core)	0	Folded into the start of Visit 2 — post cemented and core built in the same session (Source: L4 RETT Online — “Prefabricated Post Systems”)
Indirect / cast post and core	+1 to +2	Post space prep + post impression + temporary post crown, then a separate cast try-in and cementation visit before the crown impression can be taken (Source: L3 Post and core fabrication techniques — “Workflow by Technique”; L4 RETT Online — “Cast Post and Core Systems”)

Cementation cannot rescue a bad foundation: “It cannot compensate for missing ferrule, inadequate remaining walls, or over-prepared canals.” (Source: L4 RETT Online — “Post Cementation: Roles and Objectives”)

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Visit 1 — Primary impressions and records

1. Preliminary alginate impressions, both arches, for custom special tray fabrication (Source: Coals 3. Definitive (Reconstructive phase treatment) — “Crowns”, Visit 1)
2. Record a putty key — preparation guide and future provisional fabrication (same)
3. Diagnostic wax-up if the tooth needs morphological modification (Source: F8 Try in — “Preparation stage”)
4. Send preliminary impressions to lab for the custom tray (Source: Coals 3. Definitive (Reconstructive phase treatment) — “Crowns”)

Does the primary impression need its own visit?

It depends on whether you are using a custom tray, and no source says this out loud.

• Coals 3. Definitive (Reconstructive phase treatment) gives it a whole visit, because the custom special tray must be lab-made before the prep visit (“Use custom tray, take impression” at Visit 2).
• F8 Try in has no primary impression stage at all — Phase 2 opens directly at “2.1. Tooth Preparation”, and records are handled conditionally inside the prep visit: “Take a new opposing model or putty key if any changes have occurred since the initial records.”
• DMD2 L2 - Clinical Steps for Indirect Restos, DMD2 L1 - Principles of Tooth Prep and F5 Principles of tooth prep list Primary Impression as a distinct stage but never as a distinct appointment.

Practical reading: with a stock tray or an intraoral scan, Visit 1 collapses into Visit 2. With a custom tray it cannot.

Putty index technique (Source: F1.1 Full Gold Crown Preparation Steps — “1. Silicone Putty Index”):

• Purpose: “Gives a useful guide to the original shape of the tooth once preparation has begun”
• Not needed every case — “Mainly when major modifications are required. In conjunction with wax-up”
• Take two. One kept intact for the temporary; one sectioned buccolingually as a reduction guide

Articulator mounting is indicated for more than two single crowns or a bridge, diagnostic wax-up, occlusal assessment, or any case where OVD is being increased. For a single crown it is listed with a question mark — “Mounting may be optional if the patient has stable occlusion and a ‘confirmative’ approach is used.” (Source: L1 Articulators — “Indications for Mounting Models”)

If mounting, a facebow records the maxillary occlusal plane relative to the hinge axis; without it, “changing the OVD on the articulator will result in incorrect tooth reduction (either too much or too little)” (Source: L1 Articulators — “OVD Reduction: Model Mounted Without Facebow”). Full 7-step facebow procedure in L1 Articulators — “Facebow Record Procedure”.

Check mounted models before they go anywhere

“If the mounted models do not look like the patient’s mouth, do not send them to the lab. Remount them immediately.” (Source: L1 Articulators — “Articulator Usage and Best Practices”)

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Visit 2 — Preparation, definitive impression and temporisation

The longest visit. Order below follows F8 Try in — “Day of preparation”, with divergences flagged.

Before the patient arrives

• Decide the material and be able to justify it (Source: F8 Try in — “Preparation stage”)
• Treatment plan approved (same)
• Wax-up + putty key made if modifications are required (same)

2.1 Confirm and anaesthetise

Confirm the plan with the patient; administer LA. Anaesthesia is needed even for endodontically treated teeth — “for patient comfort during soft tissue manipulation (e.g., placing retraction cord)” (Source: F1.1 Full Gold Crown Preparation Steps — “Pre-Operative Steps”).

Take the opposing-arch impression while waiting for the anaesthetic to take effect (same).

2.2 Shade

Shade timing — the sources directly contradict each other

• Before preparation — “Select the shade before preparing and dehydrating the tooth”, with the stated reason “Perform before tooth preparation to avoid dehydration.” (Source: F8 Try in — “Day of preparation”, step 3; “Tips for Shade Taking”)
• After preparation and after the impression — Coals 3. Definitive (Reconstructive phase treatment) — “Crowns” lists shade fifth in Visit 2, three steps after “Prepare tooth”, with no rationale given.
• Not mentioned at all in DMD2 L2 - Clinical Steps for Indirect Restos — “Clinical Procedure Workflow”.

Follow F8. It is the only source that gives a mechanism, and the mechanism is sound — a prepared, air-dried tooth lightens and reads a false shade. W2 Clinical Applications does not take a side on timing, but its instruction to “Assess the shade with the tooth in its natural wet state” points the same way.

Technique (Source: W2 Clinical Applications — “Selection Guidelines” / “Prepare the Tooth” / “Select the Shade”):

1. Natural daylight or daylight-balanced light — avoid fluorescent or incandescent
2. Neutral white or grey background
3. Clean the tooth of stains and debris; assess it wet
4. Use a shade guide matching the restorative material; keep it clean
5. Compare against multiple tabs, and across incisal edge / middle third / cervical area
6. Quick glances only — “to avoid fatiguing the eye’s cone cells” (Source: F8 Try in — “Tips for Shade Taking”)

Guides at OHCWA (Source: W2 Clinical Applications — “Shade Guides at OHCWA”):

Guide	Use
Vita 3D Master – Classic	Indirect restorations: crowns, onlays
3M Composite Shade Guide	(no indication stated in source)
Portrait Shade Guide	Acrylic teeth (dentures)
Vita 3D Master Linear	Five value tabs, then chroma/hue within the value range

The OHCWA slide conflates two VITA systems

“Vita 3D Master - Classic” merges what F8 Try in treats as two separate guides: VITA plan classic (16 shades, hue first — A/B/C/D families, then chroma-value) and Vitapan 3D-Master (value → chroma → hue, more accurate). Quoted verbatim above; be aware when reading the slide.

Record and communicate the shade to the lab, including “any specific characteristics or variations in the tooth colour”; in difficult cases the lab can select the shade (Source: W2 Clinical Applications — “Consult with the Lab (for indirect restorations/dentures etc)”). Communicate in-between shades (e.g. A1.5) and different shades for different thirds (Source: F8 Try in — “Tips for Shade Taking”).

2.3 Update records

New opposing model or putty key if anything has changed since the initial records (Source: F8 Try in — “Day of preparation”, step 2).

2.4 Tooth preparation

Full bur-level technique is in Molar Crown and Bridge Preparation Tips — “Step-by-step molar prep” and “Bur sequence by material”. Visit-level sequence (Source: F1.1 Full Gold Crown Preparation Steps — “Preparation Steps”):

1. Silicone putty index (see Visit 1)
2. Occlusal reduction — depth grooves at the highest points (triangular ridges) and lowest (developmental grooves), following anatomy. Reduce half the occlusal surface and use the other half as a guide. Gross-reduce to ~80% of final depth, leaving the last 0.2 mm for finishing
3. Axial reduction, buccal and lingual, two planes each — gingival two-thirds nearly parallel to the long axis for retention/resistance; occlusal third a second angled plane following natural contour. Path of insertion parallel to the long axis of the tooth, not the clinical crown
4. Interproximal reduction — extend buccal and lingual reductions into the embrasures without touching the adjacent tooth, then favour occlusal reduction when cutting through the marginal ridge. Follow the natural curvature, do not cut a flat slice
5. Margin — placed during axial reduction; follows the scalloped gingival contour, rising over the papilla
6. Evaluate (see 2.5)
7. Finish — fine-grit diamond or carbide, smooth transitions, all line angles rounded
8. Auxiliary retention only if needed — vertical grooves/boxes 1 mm deep, 1 mm above the margin, mid-buccal, parallel to the path of insertion

Reduction must follow occlusal anatomy — a flat reduction “creates thin spots over cusps and thick spots in fossae, concentrating stress” (Source: M1 PFM — “Adequate Tooth Reduction”). Functional cusps need an additional functional cusp bevel (Source: F5 Principles of tooth prep — “Deformation”).

Reduction specifications — OCHWA guidelines

These are the figures to prepare to

Reproduced from the OCHWA Reduction Guidelines taught in DENT4216 (Source: Operative Crown Tips And Reduction Guidelines — “OCHWA Reduction Guidelines”). This is the only complete material × arch × surface table in the vault, and it is the local clinic standard — prefer it over any individual lecture fragment or video figure below.

Metal-ceramic / PFM

Reduction (mm)	Anterior	Posterior
Incisal / occlusal	2	2 functional cusp · 1.5 non-functional cusp
Axial	1.5	1.5
Margin	1.5	1.5

All-ceramic / full-ceramic

Reduction (mm)	Anterior	Posterior
Incisal / occlusal	1.5	2 functional cusp · 1.5 non-functional cusp
Axial	1	1
Margin	1	1

Metal crown (posterior)

Reduction (mm)	Posterior
Occlusal	1.5 functional cusp · 1 non-functional cusp
Axial	1
Margin	0.5–1

Functional vs non-functional cusps (same source) — functional (supporting) cusps are maxillary lingual and mandibular buccal; they maintain vertical dimension and contact opposing fossae/marginal ridges in centric occlusion, so they take the deeper reduction. Non-functional (guiding) cusps are maxillary buccal and mandibular lingual; they guide mandibular movement and protect soft tissues but do not bear heavy occlusal load.

Corroborating lecture figures — these agree with the OCHWA table where they overlap:

• Full gold: functional 1.5 mm, non-functional 1.0 mm, axial 1.0 mm in two planes, chamfer >0.5 mm (Source: F1 FullMetalCrowns — “Preparation Criteria”; F1.1 Full Gold Crown Preparation Steps — “Reduction Amounts”)
• PFM full ceramic coverage: functional 2.0 mm, non-functional 1.5 mm, axial 1.5 mm, shoulder ≥1.5 mm (Source: M2 PFM Prep — “PFM: Full coverage with ceramic”)
• PFM partial ceramic coverage — a case the OCHWA table does not cover: functional 1.5–2.0 mm, non-functional 1.0 mm, axial 1.0 mm metal / 1.5 mm metal-ceramic, chamfer or shoulder 0.5 and 1.5 mm. Metal portion needs 0.5–1.0 mm vs at least 1.5 mm for the porcelain portion (Source: M2 PFM Prep — “PFM: Partial coverage with ceramic” / “General features”)
• Gold needs 1.0–1.5 mm occlusal vs ~2.0 mm for ceramics — “a greater amount of vertical wall height is preserved… crucial for achieving adequate retention and resistance form on teeth that are already clinically short” (Source: F1 FullMetalCrowns — “Advantages”)
• In a deep bite with limited space, a PFM with a metal palatal surface needs only 0.5 mm vs at least 1.0 mm for all-ceramic (Source: M2 PFM Prep — “Contraindications”) — consistent with the 1 mm all-ceramic axial figure above
• Ceramic shoulder design requires a shoulder with at least 1.5 mm reduction; “It cannot be done with a chamfer or feather edge” (Source: M2 PFM Prep — “Margin design”)
• Keep occlusal contacts at least 1.5 mm away from the metal-ceramic junction (Source: M2 PFM Prep — “Fabrication principles”)

The OCHWA table settles a conflict between the prep videos

The all-ceramic figures in Molar Crown and Bridge Preparation Tips are video-sourced and the videos disagree: lithium disilicate axial is given as 1.5–2.0 mm (Source: All Ceramic Crown Prepartion for Lithium Disilicate 4 Kilgore — “Key Dimensions”) but 0.8–1.0 mm (Source: All Ceramic Crown Prep in 5 minutes, The 5x5x5 Technique — “Material Reduction Standards”); margin is 0.6–0.8 mm fillet in the first but ≥1.0 mm modified shoulder in the third (Source: Lower Molar Crown Prep ACC 30 First Person Perspective — “Finish Line Refinement”).

OCHWA’s 1 mm axial and 1 mm margin align with the 5x5x5 and ACC 30 figures. The Kilgore 1.5–2.0 mm axial is the outlier — do not prepare to it.

All-ceramic is one category here — there is no separate zirconia spec

The OCHWA table groups lithium disilicate and zirconia together under “All-ceramic / full-ceramic”, and no DENT4216 or DMD3S1 lecture gives a zirconia-specific reduction figure. Monolithic zirconia tolerates thinner sections than layered ceramic in manufacturers’ own guidance, so confirm with the lab before reducing a zirconia case to the layered-ceramic figures.

Margin designs (Source: F5 Principles of tooth prep — “Margins”; M1 PFM — “Possible Designs”):

Design	Use
Chamfer	The most common. Metal or ceramic crowns. Cut with a round-tipped tapered diamond. Risk: “gutter margin” with unsupported enamel if the bur sinks too deep
Shoulder	Primarily all-ceramic; usable for all materials. Flat-end bur. Internal line angle rounded, not sharp 90° — CAD/CAM milling burs cannot reproduce a sharp internal angle
Bevel	Cast restorations. Allows burnishing; removes unsupported enamel. Not for all-ceramic — produces a thin fragile ceramic edge
Shoulder with bevel	Uncommon. Historically PFM with a metal labial margin. Poor aesthetics, biologic width risk
Feather edge	Contraindicated in most cases — inadequate bulk, indistinct finish line, leads to over-contoured restorations

Taper — ideal total occlusal convergence 6–12°; ideal taper 6°, clinically acceptable 6–20° (Source: F5 Principles of tooth prep — “Key Terminology”; M1 PFM — “Degree of taper”). TOC = 2 × taper. Tapered burs cut ~3° per wall. The shorter the axial walls, the more parallel they must be (Source: F5 Principles of tooth prep — “Grooves and Boxes”).

Margin placement (Source: F6 Soft Tissue Impressions — “Margin placement guidelines” / “Margin location”) — supragingival wherever possible; if subgingival, intracrevicular only, maximum ~0.7 mm:

Sulcus probing depth	Margin
≤1.5 mm	0.5 mm below the gingival crest
>1.5 mm	Half the probing depth
>2 mm	Consider gingivectomy to design a 1.5 mm sulcus

Biologic width = junctional epithelium (0.97 mm) + connective tissue attachment (1.07 mm) ≈ 2–2.25 mm. A margin within 2 mm of crestal bone causes inflammation, then bone loss as biologic width re-establishes (Source: F5 Principles of tooth prep — “Biologic Width” / “Margin location”). Diagnose violation by bone sounding: probe to the bone crest under LA, subtract sulcus depth; <2 mm indicates a problem (Source: F6 Soft Tissue Impressions — “Biologic width”).

Crest type governs how much subgingival extension the tissue tolerates (Source: F6 Soft Tissue Impressions — “Bone sounding”):

Type	Prevalence	Crest to gingival margin	Consequence
Normal	85%	3–4.5 mm	Tolerates ~0.5 mm subgingival; recovers well from cord trauma
Low	13%	>4.5 mm	Fragile attachment, prone to recession after cord damage
High	2%	<3 mm	A subgingival margin “will almost certainly impinge on the biologic width”

2.5 Check the preparation

(Source: F1.1 Full Gold Crown Preparation Steps — “Evaluation of the Preparation”)

• Occlusal clearance — verify with the sectioned putty index across the whole surface; check against the antagonist in centric and excursion
• Undercuts — view from directly above; every part of the margin must be visible. Examine with one eye closed — “If both eyes are open, undercuts may remain undetected” (Source: F5 Principles of tooth prep — “Taper and Undercuts”). On the cast, all margins should be visible at 30 cm (Source: M1 PFM — “Degree of taper”)
• Taper — mesiodistal from buccal/lingual; buccolingual from mesial/distal. Seeing a large amount of axial wall from the occlusal means it is over-tapered
• Margin — explorer or periodontal probe; smooth, continuous, no ledges

2.6 Fabricate the provisional

Provisional before or after the impression?

• Before — “Fabricate the provisional crown before taking the final impression. This ensures the patient can leave with a temporary if the impression needs to be retaken.” (Source: F8 Try in — “Day of preparation”, step 6). DMD2 L2 - Clinical Steps for Indirect Restos — “Provisionalization and Impressions” agrees, without giving a reason.
• After — Coals 3. Definitive (Reconstructive phase treatment) — “Crowns” places fabrication four steps after the impression.

Follow F8/L2. F8 is the only source that argues why, and the argument is practical.

Requirements — a provisional must protect the pulp, maintain periodontal health, provide occlusal compatibility, maintain tooth position, and protect against fracture (Source: F3 Temporizations — “Biologic”). Loss of the temporary risks “supra-eruption of the opposing tooth or tilting… or drifting of adjacent teeth into the prepared space. This movement can prevent the final crown from seating correctly, requiring significant chairside adjustments or a complete remake.” (same — “Biological Factors”)

Materials (Source: F3 Temporizations — “Temporary materials”; M3 Temporization — “MATERIALS”):

Material	Use	Watch
Bis-acryl composite (Luxatemp, Protemp, Structor, Integrity)	Single crowns, direct with matrix or template; short-span bridge	Brittle, difficult to repair, does not bond to polycarbonate
PEMA (Trim, Snap)	Single crowns direct; relining shells; short-term (2–3 weeks)	Weaker than PMMA; unpleasant odour
PMMA (Jet, Polyvicron)	Laboratory/indirect; long-span; “Should not be used directly in the mouth”	Highly exothermic, ~21% polymerisation shrinkage, monomer release toxic to pulp
Light-cured composite (Symphony)	Single unit; inlays/onlays/veneers; repairing open bis-acryl margins	Brittle; needs a transparent template; time-consuming

Direct custom technique — lubricate the prep, apply material to the mould, seat, trim excess, polish (Source: M3 Temporization — “Direct: Custom”). Fit is compromised as “there is no dedicated space for cement” (Source: F3 Temporizations — “Direct Fabrication: Custom Method”).

Preformed polycarbonate technique (Source: M3 Temporization — “Polycarbonate crowns”) — select for morphology and mesiodistal width → adjust height to a passive fit → lubricate the prep with thin petroleum → mix PEMA → place in the shell when it loses its gloss → seat and align → remove marginal excess before the rubbery stage → at the rubbery stage (~2 min) remove and reseat to prevent locking into undercuts → adjust at full set (~5 min) → adjust occlusion.

2.7 Soft tissue management and definitive impression

Preconditions. Achieve gingival health first — inflamed tissue is swollen, bleeds, and recedes after resolution. “achieve gingival health before embarking on definitive impressions 3-4 weeks with provisional restoration” (Source: F6 Soft Tissue Impressions — “Impression timing”).

Displacement methods (Source: F6 Soft Tissue Impressions — “Methods of gingival displacement”):

Class	Methods
Mechanical	Retraction cord (stretches circumferential periodontal fibres 0.3–0.4 mm); copper band
Chemical	Aluminium chloride (Hemadent), aluminium sulfate, potassium sulfate, ferric chloride, ferric sulfate (Astringedent); adrenaline
Combined	Cord + chemical; Expasyl (Kerr) — aluminium chloride with kaolin, expands on setting, left 1–2 min, washed off with water spray
Surgical	Electrosurgery; laser

Surgical displacement cautions

Both carry “Risk of permanent damage — Recession” and should be avoided for thin gingiva. Electrosurgery is contraindicated in patients with any electrical device (pacemakers) and “should not be used around implants” because of heat production. Lasers can be used around implants and existing restorations but cut much more slowly and need protective eyewear. (Source: F6 Soft Tissue Impressions — “Surgical Techniques” / “Electrosurgery” / “Laser”)

Adrenaline “Can cause tachycardia” — use with care in cardiovascular disease, “especially if applied to lacerated tissue” (same — “Chemical displacement: Hemostatic agent”).

Cord packing (Source: F6 Soft Tissue Impressions — “Cord packing technique”):

1. Isolate — free of saliva and blood
2. Cut cord ~1.5× the circumference of the tooth
3. Wet the cord in astringent
4. Form a loop, held taut between thumb and forefinger
5. Begin on the mesial; tack lightly into the distal crevice to hold position
6. Pack with a rotational, tucking motion — not a straight push. Angle the instrument towards the tooth and slightly towards the already-packed cord
7. Do not overpack
8. Leave the ends buccal or lingual, never interproximal
9. Leave in place 3–5 minutes
10. Dry the teeth — do not desiccate
11. Evaluate: all margins visible, no tissue folding over the cord

Single vs double cord (Source: F6 Soft Tissue Impressions — “Single vs. double cord”, Gracis et al. 2001):

	Single	Double
Indication	Shallow sulcus; thin periodontium	Deeper sulcus; where bleeding/fluid control matters
Advantage	Least traumatic; limited recession risk	Excellent lateral displacement; superior fluid control
Disadvantage	Haemorrhage; exudate	Slower, more traumatic; unpredictable in high or low crest patients

Double-cord method: thin cord (000 or 00) placed first, deep and completely below the margin for vertical displacement — stays in during the impression; larger cord (0 or 1) on top for horizontal displacement, left ~5 minutes, removed just before injecting.

Impression technique (Source: F6 Soft Tissue Impressions — “Impression Techniques”):

Variant	Verdict
Dual-phase light body + heavy body	”This is the recommended single-stage technique”
Two-step with putty (cut-out or spacer)	“Good accuracy”
One-step putty wash	”significantly lower accuracy compared to two step impressions”
Monophase	”NOT RECOMMENDED DUE TO LOWER DEFINITION”
Triple tray	”not recommended due to distortion of material” — limited use, e.g. single crown with very limited opening

Both one- and two-stage are “clinically acceptable (marginal gap <120 µm)” (same — “1-stage vs 2-stage”).

Chairside sequence (Source: F6 Soft Tissue Impressions — “Clinical steps” / “Tray removal”):

1. Try in the custom tray; apply tray adhesive 15 minutes prior, extending over the tray edge, and let it dry until tacky
2. Displacement (above)
3. Mix — extrude a little material from a cartridge first to clear blockage and ensure an even mix
4. Load — clinician applies light body on the tooth while the assistant loads medium/heavy body just below the height of the tray. Keep the mixing tip submerged
5. Apply intraorally — remove the second cord / rinse off Expasyl, dry the prep, then inject starting from the hardest area (usually interproximal), on top of the margins, moving in one direction, covering the prep and part of the adjacent teeth
6. Remove the retraction cord immediately (Source: F8 Try in — “Day of preparation”, step 7)
7. Seat the tray — one continuous slow movement, back to front so excess is directed away from the throat. Hold for the full set
8. Remove — upper: loosen on the opposing side. Lower: loosen on the prep side. Anterior: both sides simultaneously

Gagging patients

Special tray with less material; no material on the palate for fixed pros; suction and mirror ready; sit the patient up and lean them forward. “Do not remove once seated even if you think it is unsatisfactory” — explain that the tray cannot come out until fully set. (Source: F6 Soft Tissue Impressions — “Gagging Patients?”)

Inspection — five criteria (Source: F6 Soft Tissue Impressions — “Impression Inspection”):

1. Detailed accurate occlusal surfaces, sharp cusps, tray does not show through
2. Distal surfaces of molars captured — more than half of each molar visible
3. No bubbles, voids, thin walls, shifts or double imprints
4. All gingival margins defined and clear, including at least 3–4 mm of buccal and lingual surface outside the margin
5. Uniform material layer, no separation of light and heavy body

The governing rule

“If you, the clinician, cannot clearly identify the margin on the impression, the lab will not be able to either.” (Source: F6 Soft Tissue Impressions — “Impression Inspection”)

Troubleshooting (Source: F6 Soft Tissue Impressions — “Trouble Shooting”):

Defect	Cause	Fix
Bubbles	Moisture/blood contamination; air incorporated during application	Dry field with good haemostasis; keep the syringe tip submerged
Drag lines	Material set before the tray was seated, or tray moved — “This indicates you are not working fast enough”	Improve workflow; have everything ready
Incomplete set	Removed too soon; latex/sulfur contamination; blocked cartridge giving wrong mix ratio	Time the set; use nitrile gloves; bleed the cartridge

PVS vs polyether (Source: Impression Materials A Comparative Review of Impression Materials Most Commonly Used in Restorative Dentistry; F6 Soft Tissue Impressions — “Impression Materials”):

	PVS	Polyether
Elastic recovery	Best	Second
Tear strength	Moderate — better than hydrocolloid, worse than polyether	Highest — “enables the dentist to get good subgingival detail without tearing”
Hydrophilicity	Intrinsically hydrophobic; surfactants only partly compensate. “A dry field is critical for their use”	Moderately hydrophilic; “moisture does not interfere as much”
Rigidity	Less rigid than polyether	Least flexible; detrimental for full-arch impressions of mobile teeth
Latex inhibition	Yes — platinum catalyst inhibited by sulfur compounds	”not altered or contaminated by latex gloves”
Pouring	Hydrogen byproduct — wait ≥30 min before pouring gypsum unless the product has a scavenger	No byproduct; low contact angle, bubble-free casts

Both remain dimensionally accurate for 1 to 2 weeks. Fixed prosthodontics needs detail reproduction in the 20–70 µm range.

Digital alternative — intraoral scan

Maxillary path: start occlusal on the molar, wait 3–5 clicks → occlusal to the centrals (wiggle at the incisal edges) → occlusal to the opposite last molar → rotate 60–90° to buccal and sweep back → roll to palatal and complete (Source: L2 Introduction to Trios Scanning — “3Shape scan strategy” → “Maxilla”).

Mandibular path: molar occlusal → centrals (wiggle) → opposite last molar → turn lingual, roll 60–90°, use the tip to hold the tongue away → lingual sweep → roll buccal and complete. Lingual is scanned before buccal “to capture it before saliva pools or the tongue moves” (same — “Mandible”).

Subgingival margins are the limit of intraoral scanning

“Scanners cannot ‘see’ through tissue or fluids. If a margin is more than 0.5mm to 1.0mm subgingival, a conventional impression may be more reliable. Subgingival margins remain the greatest challenge for IOS.” (Source: L2 Introduction to Trios Scanning — “subgingival finish line”)

This sits exactly on top of the conventional guidance above, which treats ~0.5 mm subgingival as routinely acceptable and permits up to 0.7 mm. If you have planned an intracrevicular margin, decide conventional vs digital before you prep.

Also: “What you see is what you get” — if you cannot see the prep with the naked eye, neither can the scanner. Review the scan in monochrome, not colour, because colour bleeding obscures the margin. (same — “The detail an image holds”)

Scanning is validated “for restoring up to ten units without extended edentulous spans”; for full arch, conventional is more accurate but digital is far faster (248 s vs 605 s), limited by stitching error (Source: L2 Introduction to Trios Scanning — “Accuracy and precision of 3 intraoral scanners…”; F4 Digital Impressions — “Systematic Review Digital vs. Conventional Impressions”).

2.8 Bite registration and opposing arch

• Alginate impression of the opposing arch, if not already recorded (Source: Coals 3. Definitive (Reconstructive phase treatment) — “Crowns”)
• Bite registration with Regisil (same)

Bite registration appears in only one source

Coals 3. Definitive (Reconstructive phase treatment) is the only vault source that includes an interocclusal record in the crown prep visit. F8 Try in, DMD2 L2 - Clinical Steps for Indirect Restos, F5 Principles of tooth prep and DMD2 L1 - Principles of Tooth Prep do not mention it at all; F8’s nearest equivalent is a conditional opposing-model update, which records the arch but not the relationship. A sequence built only from the lecture material would ship a prep visit with no bite record. Take the bite.

For a conformative case record at MIP: “Respect working time of bite registration material / Do not use a lot of material / Check if the patient is contacting upper and lower teeth” (Source: L1 Articulators — “MIP (Habitual Bite Position) Technique”). For a reorganised case record in CR — leaf gauge, Lucia jig, or deprogrammer (same — “CR Techniques”).

2.9 Cement the provisional

Cement selection (Source: F3 Temporizations — “Types” / “Considerations”) — zinc oxide eugenol (Tempbond) is most commonly used. High-strength cements should be avoided because they cause damage on removal, but are indicated where retention is poor, the provisional is long-span or long-term, or the patient has parafunction. Strength can be reduced by adding petroleum gel (Source: M3 Temporization — “TEMPORARY CEMENTS”).

Eugenol and resin cements

Use a eugenol-free temporary cement if the definitive restoration will be bonded with a resin cement — “Free eugenol acts as a plasticiser of methacrylate resin” (Source: F3 Temporizations — “Considerations”).

Note the evidence is presented differently in the two versions of this lecture: F3 Temporizations — “Eugenol and resin cements” states inhibition as settled; M3 Temporization — “TEMPORARY CEMENTS” hedges — “there are other in vitro studies showing no difference.” Choosing eugenol-free costs nothing, so default to it.

Application (Source: F3 Temporizations — “Application procedure”; M3 Temporization — “Cementation Process”):

1. Mix base and activator
2. Apply a small quantity just short of the margin — a very thin layer to the internal surface
3. Seat and hold firmly, or have the patient bite on a cotton roll
4. Remove excess with an explorer and dental floss at the rubbery/partially set stage; pass floss through the contacts before full set
5. Confirm no cement is left in the gingival sulcus
6. Check and adjust occlusion after cementation — the cement layer may make the crown slightly high

Consider a small amount of Vaseline in the crown’s intaglio to ease later removal (Source: Dental Luting Cements An Updated Comprehensive Review — “4. Provisional Luting Cements”).

2.10 Post-operative instructions

Tell the patient the restoration is temporary and held with weak cement; avoid sticky or hard foods on that side; and when flossing, “pass the floss through the contact point, then pull it out from the side rather than pulling it back up through the contact” (Source: F3 Temporizations — “Patient Instructions”).

2.11 Dispatch to the laboratory

The lab prescription is the least-documented stage in the vault

Across every source searched, the total content on what goes in a crown lab prescription is roughly six statements:

• “Send the impression and complete lab prescription to the dental laboratory for fabrication of the permanent crown” (Source: F8 Try in — “2.0 Phase 2: Preparation and Impression”)
• “bite registration, model, lab slip, shade (if crown)” (Source: Pros Lab Introduction — “Process of Submitting Lab work”)
• “Clearly document and communicate the selected shade to the dental lab. Provide any additional information, such as any specific characteristics or variations in the tooth colour.” (Source: W2 Clinical Applications — “Consult with the Lab (for indirect restorations/dentures etc)”)
• “Communication with dental laboratory” as a bare bullet (Source: M3 Temporization — “Objectives of Provisional Restorations”)
• Articulator mounting “only done on request for complex cases” (Source: Pros Lab Introduction — “Articulators”)

No source states that you should prescribe the restoration material — despite F8 Try in instructing you to decide it before the patient arrives. No source gives a lab-slip field list, turnaround time, or disinfection protocol. Treat this section as a known gap, not a complete checklist.

Digital dispatch (Source: L2 Introduction to Trios Scanning — “Laboratory workflow”):

1. The university uses a shared account — you must put your name and student ID in the scan’s “Notes” field
2. A physical paper slip is still required to trigger production or request export to your library
3. Files go to the lab for 3D printing (models) or milling (crowns/splints), e.g. on the Ivoclar PM7

File formats: STL is the universal CAD/CAM format, monochromatic, used for printing and milling; PLY includes colour data but is less universal; DCM is 3Shape’s proprietary viewer format, useful for discussing preps with tutors (same).

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Laboratory interval

Analog path: wax up → casting → veneering/polishing. Digital path: CAD → milling → sintering → veneering/polishing (Source: F5 Principles of tooth prep — “Clinical procedures” / “Workflow”).

Evaluate the crown on the die — before the patient arrives

Why this happens off the clock

“Detection of fabrication errors (laboratory related) prior to the clinical appointment / Save critical chair time / Anticipation of problems before the clinical appointment / Utilize good lighting and magnification during inspection / Consult with the dental laboratory in case of identified problems” (Source: L4 Try in — “Evaluation of Crown on the Die”)

Do it 1–2 working days before the appointment, so the lab has time to correct (same — “Timing”). Absent from Coals 3. Definitive (Reconstructive phase treatment) entirely.

1. Die and opposing model — poor pouring, overtrimming, fracture, scratches, wear. Over-trimming around proximal surfaces produces over-contoured crowns; over-trimming at the margin produces an under-extended crown margin. Wear on the opposing model suggests artificially high occlusion (Source: L4 Try in — “Assess the Die and Opposing Model”; F8 Try in — “Assess the die and opposing model”)
2. Internal surface — air bubbles, casting nodules or blebs. “Ideally, the casting should touch the die at the margins only.” Because of die spacer, the crown should fit slightly loosely on the die, not with a friction fit (Source: F8 Try in — “Internal surface:”)
3. Overall fit and resistance — looseness, excessive gap, proximal contact areas
4. Marginal integrity — open margins, overhangs, underextensions
5. External surface — contour, shade, surface texture. “Ensure the lab has delivered what was requested.” (Source: F8 Try in — “External surface”)
6. Occlusion on the articulator — centric contacts, eccentric contacts, interferences

Laboratory error checklist (Source: L4 Try in — “Laboratory Error Checklist”):

Error	Cause	Remedy
Tight proximal contacts	Imprecise die location or abrasion of stone contact points	Check for die displacement; identify with articulating paper; grind and polish
Casting blebs on fit surface	Air bubbles trapped during investment	Identify under magnification, remove with a small round bur
Over-extended margins	Poor impression, trimming, or surplus wax/porcelain	Trim from the axial surface and polish; consider returning to lab
Under-extended margins	Poor impression or difficulty identifying the finish line	If obvious, have the crown remade; alternatively retake the impression
Damaged dies	Chipped finish line or abrasion from reseating faulty castings	Determine the cause; if fit fails after adjusting blebs, return to lab
No die spacer	Technician error	Tight fit; crown may not seat or may lift after cementation

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Visit 3 — Try-in and cementation

There is no undo after cementation

“Once a crown or fixed partial denture (FPD) is cemented with permanent cement, there is no quick ‘undo’ button for large modifications. Failure to properly evaluate the restoration before cementation risks debonding, recurrent caries, and patient dissatisfaction.” (Source: L4 Try in — “Trial Insertion of Indirect Restorations”)

3.1 Remove the provisional

Administer LA if required. Attempt to wiggle the temporary off first. If it will not come, apply a gentle rocking motion with gauze and forceps; if the preparation is too parallel, section vertically from buccal to lingual, cutting only as far as the white opaque cement layer (Source: L4 Try in — “Removal of Provisional Restoration”).

Crown removers: back-action, automatic, Richwill (same).

Clean all residual temporary cement with an ultrasonic scaler (same).

Aspiration

“Warn the patient not to move suddenly to avoid aspiration of the uncemented crown; the assistant should hold the crown with a finger or ball burnisher.” (Source: L4 Try in — “Reading”)

Minor divergence — what cleans the preparation

F8 Try in and DMD2 L2 - Clinical Steps for Indirect Restos specify an ultrasonic scaler; Coals 3. Definitive (Reconstructive phase treatment) specifies pumice. Not a conflict worth agonising over — pumice also serves the pre-cementation cleaning step.

3.2 Seat the crown — in this order

The order is not optional

Proximal contact → internal fit → marginal fit. “This sequence must be followed in order to correctly diagnose any fitting issues. A crown cannot seat fully if the proximal contacts are too tight.” (Source: F8 Try in — “Systematic approach”)

Proximal contacts — assess with dental floss; it “should pass through with resistance and a ‘click’”. Shim stock (8 µm) should just pass through. Contacts should sit in the same location as the natural contacts. Mark with articulating paper (20 µm), Accufilm, or Occlude spray and adjust incrementally with a fine diamond — adjust one side at a time, because mobile adjacent teeth affect the opposite contact, and do not create an open contact. An open contact must go back to the lab for material addition. (Source: F8 Try in — “Proximal contacts”; L4 Try in — “Proximal Contacts” / “Reading”)

Internal fit — the restoration must seat completely without interference. Use a disclosing medium (Fit Checker or light-body impression material) or Occlude aerosol, which gives “negative marking (high spots rub off the spray), which is often faster than articulating paper.” Areas where the medium is penetrated or wiped away are high spots; relieve with a diamond bur. (Source: L4 Try in — “Internal Fit” / “Fit Checker Application” / “Reading”)

Fits the model but not the mouth?

Suspect the impression — early removal, distortion, or latex contamination. A new impression is required. (Source: L4 Try in — “Clinical vs. Laboratory Fit Discrepancies”)

Marginal fit — assess in the gingivo-occlusal direction, the occluso-gingival direction, and both simultaneously (Source: L4 Try in — “Directional Assessment”). A gap of 100 microns is the borderline for acceptability (detectable by probe) (same — “Marginal Fit”).

State	Action
Ideal	Proceed
Overextended / overhang	Adjust from the external surface only — “Do not adjust the fitting (internal) surface, as this will compromise the seal”
Underextended	Usually requires a remake
Open margin	Requires a remake

(Source: L4 Try in — “Visual Classification of Margins” / “Adjustment of Overextended Margins”; F8 Try in — “Marginal fit”)

Effects of open margins: sensitivity, dissolution of cement, plaque retention, secondary caries, gingival inflammation (Source: L4 Try in — “Effects of Open Margins”).

3.3 Assess the seated crown — stability → contour → occlusion → aesthetics

Stability — apply force; the restoration “should not rotate or rock.” Instability usually reflects internal surface misfit from impression or fabrication distortion, and “often leads to cementation failure” (Source: L4 Try in — “Stability”).

Contour — must be adjusted and polished before cementation. Undercontoured leads to food impaction and gingival injury; overcontoured leads to plaque retention and gingival inflammation (Source: DMD2 L2 - Clinical Steps for Indirect Restos — “Gingival Health and Appearance”).

Occlusion — the crown must be fully seated before checking (Source: L4 Try in — “Occlusion”).

Shim stock: assess (1) all teeth without the prosthesis, (2) with the prosthesis in place, (3) the crown itself. Posterior — crown and adjacent teeth should all hold shim stock firmly. Anterior — the crown should hold it lightly, consistent with the other anteriors. “If adjacent teeth held shim stock before insertion but no longer do while the restoration holds it, the restoration is too high.” (Source: F8 Try in — “Shim stock assessment”; L4 Try in — “Shim Stock Assessment”)

Shim stock thickness — 8 µm or 8–10 µm

F8 Try in and DMD2 L2 - Clinical Steps for Indirect Restos state 8 µm; L4 Try in heads the section “Use of Shim Stock (8-10 μm)”. Immaterial in practice — use what the clinic stocks — but worth knowing before an exam.

Articulating paper: dark (blue) = centric (CR or MIP); lighter (red) = eccentric (protrusion, lateroprotrusion). Adjust “until the marks on the crown are of similar intensity to those on adjacent teeth.” (Source: L4 Try in — “Articulating Paper Assessment”; F8 Try in — “Articulating paper assessment”)

Adjustment guidelines (Source: L4 Try in — “Occlusal Adjustment Guidelines”):

• Premature contact (centric) — adjust grooves or cusp inclines. Never adjust the tip of a functional cusp
• Interference (eccentric) — adjust cusp inclines; adjust cusp tips “only if absolutely necessary”
• If a cusp tip must be modified to preserve a scheme like canine guidance, consider adjusting the opposing tooth instead
• Major adjustments before cementation; minor adjustments can be completed after (Source: F8 Try in — “Occlusion”)

F8 Try in states the rule more absolutely — "Never the tip of cusp" — where L4 Try in narrows it to the functional cusp. L4 is the later source and the qualified version is the more defensible one.

Criteria for a completed adjustment — well-distributed contacts; posterior: prosthesis and remaining dentition hold shim stock equally; anterior: prosthesis lightly holds shim stock if other anteriors do (Source: DMD2 L2 - Clinical Steps for Indirect Restos — “Criteria for Completed Adjustment”).

Aesthetics and patient approval

Patient approval is a gate, not a courtesy

“Patient approval should be obtained prior to cementation.” (Source: DMD2 L2 - Clinical Steps for Indirect Restos — “Patient Approval”) “Always show the patient the crown in a mirror and get their explicit approval before cementation.” (Source: F8 Try in — “Aesthetics”)

If the patient is uncertain, especially anteriorly, cement with temporary cement so they can “test drive” the aesthetics for a week — far easier than cutting off a permanently cemented crown (same).

Note this step is absent from Coals 3. Definitive (Reconstructive phase treatment), which goes straight from try-in to bonding.

Remedies: too light → stain and glaze; too dark → cut back and reapply ceramic; morphology → modify with diamond burs and Sof-Lex discs, then return to the lab for glazing. A shade too dark, or a tooth too short, requires a remake. (Source: DMD2 L2 - Clinical Steps for Indirect Restos — “Shade and Morphology”; F8 Try in — “Aesthetics”)

Finishing and polishing — metal: rubber polishing wheels and points. Ceramic: composite finishing rubber burs, rubber cup with diamond polishing paste, or send to the lab for reglazing. “Any areas of the ceramic that have been adjusted with a bur must be thoroughly polished… A rough surface will feel uncomfortable and can cause wear on the opposing teeth.” (Source: F8 Try in — “Finishing and polishing”)

3.4 Cementation

Cement selection

Restoration	Cement	Source
Lithium disilicate	Adhesive resin (Variolink Esthetic / Multilink) + Monobond Plus	F7 Cements — “Guidelines”
Feldspathic / leucite-reinforced	Adhesive resin — lower flexural strength, etchable	F2 Ceramics — “Glass-Based Ceramics”
Zirconia	Self-adhesive or MDP-containing (Panavia, SpeedCEM)	F7 Cements — “Guidelines”
PFM / metal-ceramic	All classes indicated; Panavia F 2.0 + Alloy Primer	F7 Cements — “Summary table of what cement to use based on crown type”
Full gold	Water-based cements typically (zinc phosphate)	Dental Luting Cements An Updated Comprehensive Review — “3.1. Zinc Phosphate Cement”
Crown with poor retention	Adhesive resin or self-etch adhesive resin only	F7 Cements — “Summary table…”

Evidence: adhesively cemented lithium disilicate crowns had failure loads of 306.6 N vs 94.7 N for GIC (Source: DMD2 L3 - Biomaterials Dental Cements — “Retention and Failure Loads”). Zirconia-dentine shear bond strength: GI 3.4 MPa, RMGI 9.2 MPa, MDP resin 16.9 MPa (same — “Zirconia-Dentin Complex Bond Strength”).

RMGIC under all-ceramic crowns — unresolved

The 2023 review is categorical: “RMGICs are contraindicated for the fixation of more fragile all-ceramic constructions, as they expand due to water absorption, which can lead to the fracture of the restoration” (Source: Dental Luting Cements An Updated Comprehensive Review — “3.4. Hybrid Ionomer Cements…”). But DMD2 L3 - Biomaterials Dental Cements lists RMGIC as “ideal for cementation of zirconia, PFM, and lithium disilicate restorations”, and F7 Cements — “Resin modified glass ionomer” notes modern products are manufacturer-indicated for both. Unresolved in the vault. When in doubt, follow the restoration manufacturer’s technique card.

Surface treatment — glass-ceramic

1. HF etch the intaglio — often already done by the lab. Concentration 9% per the lectures (Source: F7 Cements — “Glassy ceramic crowns (Lithium disilicate, etc.)”); the 2023 review specifies 10%, but for a hybrid ceramic (Source: Dental Luting Cements An Updated Comprehensive Review — “5. Substrate and Restoration Surface Treatments before Cementation”)
2. Etch time — IPS e.max 20 seconds; IPS Empress 60 seconds (Source: F7 Cements — “Variolink Esthetic LC” → “Phase 2”)
3. Silane (MPS) — bridges the resin and ceramic, raises surface energy and lowers contact angle. Generic: agitate ~20 s then air dry. Monobond Plus specifically: agitate and react for 60 seconds, disperse with a strong air stream, do not rinse (same)

The only clinical HF etch times in the vault are the Variolink ones

The 2023 review gives no etch time at all. The 1% HF for 20 s vs 120 s figures in DMD2 L3 - Biomaterials Dental Cements — “Laboratory and Surface Preparation” are surface-morphology research data at a different concentration, not a clinical instruction. Do not synthesise a single number — follow the manufacturer’s card for the ceramic in front of you.

Surface treatment — zirconia

• Airborne particle abrasion at ~1 bar to increase surface roughness. “Care must be taken to avoid excessive pressure, which can create microcracks and weaken the zirconia.” (Source: F7 Cements — “Zirconia crowns”)
• No silane — zirconia has no glass phase to etch. Use a 10-MDP containing cement instead (Source: F7 Cements — “Guidelines”; DMD2 L3 - Biomaterials Dental Cements — “Clinical Guidelines and Summary”)

Do not transfer the 100 µm / 2 bar figure to zirconia

“Sandblasting (2 bar, Al₂O₃, 100 µm)” in the Variolink protocol is the indirect composite roughening step (Source: F7 Cements — “Variolink Esthetic LC” → “Phase 2”). No source in the vault gives a particle size for zirconia — only the ~1 bar pressure ceiling.

Decontamination after try-in

After try-in the intaglio is contaminated with saliva, blood or try-in paste, which “lowers the surface energy and prevents the cement from properly wetting and bonding” (Source: F7 Cements — “Cleaning and Surface Contamination”).

• Both lithium disilicate and zirconia: Ivoclean or Katana Cleaner — rub on, wash off, dry (Source: F7 Cements — “Guidelines”)
• Phosphoric acid is an alternative for glassy ceramics but the literature is mixed — it may over-etch. “Universal cleaners (e.g., Ivoclean) are generally the more predictable option.” (same — “Cleaning and Surface Contamination”)
• For zirconia, airborne particle abrasion gives “the best outcome to restore previous uncontaminated surface bond strengths”, followed by HF acid or intaglio cleaners (same — “What about zirconia?”)

Variolink Esthetic LC protocol (Source: F7 Cements — “Variolink Esthetic LC”, Phases 1–5):

Phase 1 — try-in: apply try-in paste → seat and assess colour and fit → remove and clean paste from restoration and tooth → isolate (rubber dam).

Phase 2 — restoration, extra-oral (complete this before touching the tooth, to avoid contaminating the etched surface): wash intaglio → air dry → optional Ivoclean, rub/wash/dry → condition (HF per material above; composite: sandblast 2 bar/100 µm Al₂O₃) → Monobond Plus, react 60 s → disperse with air, do not rinse.

Phase 3 — tooth, intra-oral: rinse and air dry → optional Total Etch 15–30 s → rinse thoroughly and air dry → Adhese Universal → scrub 20 s → air-thin, avoid pooling → light cure 10 s.

Phase 4 — cementation: apply cement to the pre-treated intaglio → seat fully (patient bites on a cotton roll) → tack cure 2 s → remove excess with a plastic instrument buccally and lingually → interproximally, assistant holds the crown down while you pass floss through and pull it out to the side, never back up occlusally → apply Liquid Strip glycerin gel around all margins to defeat the oxygen inhibition layer → final cure 10 s per surface through the Liquid Strip.

Phase 5 — finishing: rinse off Liquid Strip → polish margins → Fluor Protector S → final bitewing radiograph to check for residual interproximal cement, which must be removed.

Panavia F 2.0 — zirconia (Source: F7 Cements — “PANAVIA F 2.0 for Zirconia”):

1. Mix ED PRIMER II A & B, apply to the tooth, wait 30 seconds (this initiates the cement set — do not apply cement to the tooth first)
2. Gently air dry
3. Dispense equal amounts of paste A & B; mix 20 seconds
4. Apply the mixed paste inside the sandblasted crown, not on the tooth
5. Remove excess — partially light cure 2–3 s first for easier clean-up
6. Cure the margins: light cure 20 s per surface (halogen/LED) or 5 s per surface (plasma arc/fast halogen); or self-cure by applying OXYGUARD II to the margins and waiting 3 minutes

Panavia F 2.0 — metal / PFM — identical, with one addition: after the lab sandblasts, apply Alloy Primer to the intaglio before step 1 (Source: F7 Cements — “PANAVIA F 2.0 for Metal crowns/PFM crowns”).

RelyX Unicem 2 Automix (Source: F7 Cements — “Instructions for use of rely-x”) — self-adhesive, dual cure, ~6 min set, no etching or bonding required:

1. Clean the tooth, rinse, dry with 2–3 bursts of air — do not overdry
2. After cleaning and pretreating the intaglio, dispense into the crown using the thick tip (the thin tip is for post spaces)
3. Seat → tack cure → remove all excess → final cure

Caveat: demineralisation is less aggressive than phosphoric acid, so the enamel bond may be weaker — a selective enamel etch may be beneficial (same).

Always take a post-cementation bitewing

“Always take a bitewing radiograph after cementation to check for subgingival cement remnants.” (Source: DMD2 L3 - Biomaterials Dental Cements — “Clinical Guidelines and Summary”)

And, governing everything above: “Always follow manufacturer-specific technique cards.” (same)

3.5 Post-cementation

• Re-check occlusion and make minor adjustments (Source: Coals 3. Definitive (Reconstructive phase treatment) — “Crowns”)
• Advise on crown care and oral hygiene (same)

Occlusion checked before or after cementation?

Coals 3. Definitive (Reconstructive phase treatment) checks occlusion only after cementation. Both lecture sources require major occlusal adjustment before cementation, permitting only minor adjustment afterwards (Source: F8 Try in — “Occlusion”; L4 Try in — “Occlusion”). Follow the lectures — adjust properly at try-in, then verify after cementing.

Occlusal adjustment procedure (Source: W2 Clinical Applications — “Adjusting Occlusion”):

1. Select articulating paper by thickness and colour — blue for centric, red for excursive. Use Miller’s forceps
2. Dry the teeth. “tap tap together” for centric; “Grind from side to side, and slide teeth forward” for excursions
3. Analyse the marks — heavier contacts leave darker, larger marks
4. Identify high spots — “typically the larger and darker marks”
5. Check the pattern — “Normal occlusion should show multiple small, even marks. If you see one or two large, dark spots, these are likely high spots”
6. Adjust with a fine diamond, a small amount at a time; re-dry and re-mark after every adjustment
7. Verify uniform contact bilaterally in centric, and no heavy contact in lateral or protrusive excursion
8. Polish the adjusted areas — discs, Enhance bur

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Visit 4 — Post-operative review (1–2 weeks)

Do not skip this — the patient was numb when you cemented

“Book a review appointment for the patient, typically 1-2 weeks after cementation. … The review is essential for re-evaluating the patient’s occlusion. The patient may have been numb during the insertion appointment and unable to provide accurate feedback.” (Source: F8 Try in — “5.0 Phase 5: Post-Operative Review”)

Restated: “Numb patients have unreliable proprioception; schedule a review appointment in 1–2 weeks for fine-tuning.” (Source: L4 Try in — “Occlusal Adjustment Guidelines”)

1. Re-evaluate occlusion (Source: F8 Try in — “5.0 Phase 5: Post-Operative Review”)
2. Final adjustments “to the occlusion, shape, or height of the tooth to ensure comfort and proper function” (same)
3. Check function and health of the surrounding tissues (Source: F5 Principles of tooth prep — “Workflow”)

Coals 3 has no review visit for crowns — this is a gap in that source, not a difference of opinion

Coals 3. Definitive (Reconstructive phase treatment) ends the crown sequence at Visit 3. It does schedule reviews for other prostheses (complete dentures get “Visit 7: review appointment”), so the omission is not a stylistic convention of that document. All four lecture sources mandate a crown review, and the numb-patient rationale applies with equal force.

Maintenance advice is undocumented in the vault

Coals 3. Definitive (Reconstructive phase treatment) says to “advise the patient on crown care and oral hygiene” but never says what that advice is. No source specifies flossing technique around definitive crown margins, night guard provision for bruxers, or a recall interval. The provisional-phase instructions in Visit 2.10 do not transfer — they exist because the temporary is weakly cemented.

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Source notes

• DMD2 L1 - Principles of Tooth Prep and DMD2 L2 - Clinical Steps for Indirect Restos are one model, not two — both are Dr Cheryl Fu presenting Dr Matsubara’s slides; L1’s four phases are L2’s seven steps re-bracketed. Treating them as independent corroboration overweights that lineage.
• The DMD3S1 MIR notes largely restate the DMD2S2 F-series. F6 Soft Tissue Impressions ↔ L3 Impressions and Soft Tissue Management are near-verbatim duplicates; F8 Try in ↔ L4 Try in overlap heavily, with L4 adding the laboratory error checklist and the consolidated systematic approach. F3 Temporizations ↔ M3 Temporization and F5 Principles of tooth prep ↔ M1 PFM are the same content from two lecturers.
• F8 Try in’s # Clinical sequence heading is a false lead — it contains shade-selection content, not a sequence. F8’s actual chairside sequence lives under “Preparation stage” → “Day of preparation” and “Systematic approach”.
• M1 PFM repeats several headings three times from slide de-duplication; facts are stated once above.
• Coals 3. Definitive (Reconstructive phase treatment) is informally written, with typos (“bit registration”, “marings”, “pumic”, “Permenant”) and an invalid callout type. It self-scopes its product list: “The materials aren’t static, they can vary in the real-world, these are OCHWA specific.”
• W2 Clinical Applications has no frontmatter block, and its “OHCWA” heading transposes the acronym. Content is sound; metadata needs repair.
• Operative Crown Tips And Reduction Guidelines is typed Procedure + Summary, which understates it. Its tips section is class-derived, but the reduction table is explicitly headed “OCHWA Reduction Guidelines” — a transcription of the clinic’s own standard, not a synthesis of other notes. It is cited here as the authority for reduction depths. Worth retyping and adding a Jurisdiction: UWA property.
• No fixed-prosthodontics textbook exists in the vault — no Shillingburg, Rosenstiel or Wassell, and all 78 McCracken chapter files are empty stubs. Prep geometry and gingival retraction have no textbook backing here; the lectures and the OCHWA guidelines are the only authority for those sections.