Working reference protocols from Dr. Boris Zusin, DDS, FAGD, MBA, MS, Diplomate, American Board of Dental Sleep Medicine (ABDSM), for colleagues who refer to or co-treat with our practice. Each protocol states when to use it, the steps, the cautions, and an evidence summary, with sources.
For clinicians only. This page is reference information for licensed healthcare professionals. It is not patient advice and does not replace your clinical judgment or the manufacturer's instructions for use.
Restorative
Managing sensitivity after crown preparation: IDS vs. desensitizer vs. calcium hydroxide
Scope: Selecting a dentin-sealing strategy for a vital abutment, based on the planned luting strategy.
Conventionally or self-adhesively cemented crowns where comfort is the main goal: glutaraldehyde/HEMA (Gluma-type) desensitizer.
Long interim period before delivery: a desensitizer (glutaraldehyde/HEMA preferred because it does not impair resin-cement bond).
Protocol
Control etiology first: treat active periodontal disease, correct traumatic hygiene, and verify provisional margins and occlusion.
If IDS: isolate, apply the dentin bonding agent to freshly cut dentin immediately after preparation, add a flowable resin coat when using simplified/universal adhesives, light-cure, and protect through the provisional phase. At delivery, refresh the surface (remove the oxygen-inhibited layer and contamination) before luting.
If desensitizer: apply 5% glutaraldehyde / 35% HEMA to the cut dentin per manufacturer dwell time, gently dry to a glossy non-pooled surface, then provisionalize.
If calcium hydroxide: apply a suspension to the dentin surface before provisionalization; it performs equivalently to the dentin primer for sensitivity in the 30-month crown-preparation RCT.
Seal the provisional (well-adapted margins; avoid washout of provisional cement) and verify occlusion; leakage under a poor provisional is a leading avoidable cause of persistent sensitivity.
Reassess at 1 and 2–4 weeks. Escalate per the pulpal status protocol if symptoms linger, are spontaneous, or worsen.
Cautions and limits
IDS advantage for sensitivity is confined to approximately the first week (RR 0.41, 95% CI 0.27–0.60); no significant difference at 1 and 6 months. The decision should rest on the luting strategy, not on sensitivity prevention alone.
Calcium hydroxide: 6.4% of treated abutments in the 30-month RCT lost vitality to irreversible pulpitis, consistent with reported pulp-death rates after crowning; this is not specific to the material.
Much IDS bond-strength and survival evidence is in vitro or from small RCTs.
When the crown will be adhesively cemented, the resin luting system itself seals tubules; a separate desensitizer may be unnecessary.
Evidence summary
In a 36-patient split-mouth RCT (30-month follow-up), calcium hydroxide and a glutaraldehyde/HEMA dentin primer both significantly reduced sensitivity of crown abutments, with larger reduction at 7 days than immediately and no difference between agents. A 2026 meta-analysis of vital teeth prepared for fixed prostheses found glutaraldehyde/HEMA reduces hypersensitivity without significantly altering cement bond strength (MD 0.42; 95% CI −0.32 to 1.15). A pooled IDS review reported higher restoration survival (96.4–100% vs 81.8–96.7%) and fewer complications than no sealing, and reduced early postoperative sensitivity.
Glutaraldehyde/HEMA desensitizer under an IDS adhesive: bond-strength compatibility
Scope: Whether and how a glutaraldehyde/HEMA desensitizer can be combined with immediate dentin sealing without compromising resin-cement bond.
Use when
IDS protocols where additional desensitizing, antibacterial, and collagen-stabilizing effect is wanted.
Luting with self-adhesive cement or a modern universal / self-etch adhesive system.
Protocol
Apply the glutaraldehyde/HEMA agent as a thin layer on fresh dentin; observe the recommended dwell time.
Gently air-dry or blot to a glossy, non-pooled surface so no excess resin film remains.
Place the IDS adhesive over it (filled bonding resin ± flowable resin) and light-cure it separately. Do not rely on the desensitizer alone as the bonding substrate.
Match products: confirm compatibility of the desensitizer with the adhesive and the final luting cement.
Cautions and limits
Excess unpolymerized desensitizer residue can block interaction of some self-etching luting systems with dentin and reduce bond strength (reported with a self-etch primer cement).
One conventional cement (Panavia 21) showed the lowest bond strength with Gluma pretreatment and a significant decline after thermocycling: avoid that combination.
A desensitizer meta-analysis found heterogeneous effects by agent; HEMA/glutaraldehyde products are variable.
Recommendation rests on in-vitro and review-level data; clinical bond durability with this sequence has not been isolated in an RCT.
Evidence summary
A 2026 systematic review of vital teeth prepared for fixed prostheses found no significant difference in bond strength with Gluma across cement types. With universal adhesives in self-etch mode, glutaraldehyde-based desensitizers applied first increased microtensile bond strength and stabilized the interface over 1 year of aging. Pretreatment with Gluma significantly increased shear bond strength of a self-adhesive cement, including after aging. Glutaraldehyde cross-links collagen, reducing degradation of the hybrid layer over 6 months.
Reversible vs. irreversible pulpitis after crown preparation: bedside discrimination and escalation
Scope: Working through post-preparation sensitivity in a recently prepped vital tooth with an intact provisional.
Use when
Patient reports sensitivity between preparation and cementation.
Pain pattern has changed (lingering, spontaneous, nocturnal, or biting pain).
Protocol
History: onset and trajectory; spontaneous/unprovoked pain; duration after cold/heat; night pain; NSAID response; pain on biting.
Cold test (most accurate sensibility test: sensitivity about 87%, specificity about 84%) plus EPT. A brief response that resolves in seconds favors reversible pulpitis; lingering response (>30 s), spontaneous or analgesic-resistant pain favors irreversible pulpitis.
Local factors: percussion and bite tenderness; provisional fit, margins, and occlusion (premature contact); exposed cervical dentin or recession.
Imaging: periapical radiograph first-line (periapical radiolucency, PDL widening, defective provisional margin). Reserve small-FOV CBCT for inconclusive findings or suspected fracture/anatomy, per ADA/AAOMR recommendations.
If reversible: refit or re-cement a well-adapted provisional, apply a dentin sealer, adjust high contacts, and reassess.
Escalate: no response to cold/EPT, lingering or spontaneous pain, percussion pain with periapical lucency, or swelling/fever → endodontic referral. Facial swelling, fever, trismus, or floor-of-mouth involvement → urgent referral.
Cautions and limits
Symptoms correlate imperfectly with histology; diagnosis rests on the whole clinical picture.
Brief stimulus-evoked pain is expected after preparation (hydrodynamic mechanism) and typically settles over days to a few weeks.
Pulpotomy has been reported as an alternative to pulpectomy for symptomatic irreversible pulpitis in mature teeth in retrospective data; case selection matters.
Evidence summary
Post-preparation sensitivity follows the hydrodynamic mechanism through exposed dentinal tubules and is usually reversible. Cold testing and EPT performed best among pulp tests in a meta-analysis, and a national practice-based research network study supports the use of preoperative clinical findings to identify pulp status. The ICOP classification provides diagnostic criteria for pulpitis-related orofacial pain.
Derotation of round teeth with clear aligners: attachments, IPR timing, and staging
Scope: Planning rotation of canines and premolars with aligners.
Use when
Rotated canines/premolars in aligner cases, where rotation is the least predictable movement.
Protocol
Attachments: prefer manufacturer-optimized rotation attachments where available (lower mandibular canine rotation efficacy 81.5% weekly / 76.5% biweekly vs 63.1% with vertical rectangular on biweekly). For conventional composite attachments consider oblique or horizontal crescent over vertical rectangular (maxillary canines >10°: about 55% vertical, 62% horizontal, 65% oblique; overall ANOVA p=0.09).
Staging: keep per-aligner activation small; a finite-element model of a rotated lower second premolar supported no more than about 1.2° per step for round teeth (3° produced non-physiologic PDL stress).
IPR: stage IPR to coincide with the rotation steps rather than front-loading all of it, preserving an interproximal contact to act as the rotational pivot.
Execution: verify IPR with a gauge (burs/motor-driven preferred over hand strips on canines); consider partial alignment before stripping tight contacts.
Overcorrection and refinement: plan overcorrection and a refinement phase; canine derotation is typically expressed at about 50–75%.
Cautions and limits
Concurrent IPR improved canine rotation accuracy from about 36% to 43% in one synthesis, but the original prospective study (53 canines, mean accuracy 35.8%) found no significant difference among attachments-only, IPR-only, and neither groups.
A 461-tooth retrospective study found derotation predictability governed by planned rotation magnitude, available space, direction, elastics, and crown ratio, not by attachment type.
Dual (buccal + lingual) attachments improve the couple but increase PDL strain in FEA.
Executed IPR consistently falls short of planned, especially on lower canines; about 40% of prescribed IPR sites occur in refinement plans.
Evidence summary
No system has demonstrated superiority for rotation, extrusion, or torque in head-to-head trials; predictability depends on movement type, auxiliaries, and planning. Evidence on IPR timing is minimal and rests on one prospective study, retrospective cohorts, FEA, and reviews.
Interproximal reduction: per-surface and per-arch limits, finishing, and enamel protection
Scope: Planning and executing IPR within conventional enamel-thickness limits.
Use when
Space creation for crowding, rotation, or contact reshaping in aligner or fixed treatment.
Protocol
Plan from the digital setup; stay within about 50% of local proximal enamel thickness (guideline, not a validated threshold).
Commonly cited maxima per surface: upper incisors 0.3 mm, lower incisors 0.2 mm, canines 0.3 mm, premolars 0.3 mm, molars 0.4 mm. Older protocols differ (Sheridan: about 0.25 mm anterior, up to 0.8 mm per posterior surface; Tuverson: 0.3 mm per lower incisor surface, 0.4 mm canines).
Per-arch capacity at 50% across the buccal segments: about 6.8 mm maxilla, 6.0 mm mandible (mesial of first molar to first molar); anterior segment about 2–3 mm. Median prescribed in initial Invisalign plans is about 1.1 mm per patient, concentrated in the mandibular anterior.
Use a measuring gauge and protective wire; favor the thicker distal enamel; avoid small or hypersensitive teeth.
Polish sequentially to below 0.2 µm roughness (oscillating metallic strips gave the smoothest finish in vitro).
Apply fluoride varnish or another remineralizing agent; CPP-ACP, calcium-silicate products, and resin infiltration have in-vitro benefit.
Cautions and limits
Surface layer (aprismatic, mineral-rich) is removed; roughness above about 0.2 µm increases plaque retention.
Caries evidence is mixed and largely in vitro; periodontal effects arise indirectly via plaque retention. A CBCT study found no significant effect of IPR on interradicular bone volume.
Over-reduction creates irreversible furrows and dentin hypersensitivity.
Evidence summary
Reported limits derive from minimal-enamel-thickness reference data. Evidence on caries outcomes is largely in vitro with mixed results; IPR within about 50% of enamel thickness has not been shown to compromise periodontal health.
Closing open gingival embrasures (black triangles): IPR with space closure vs. direct composite
Scope: Selecting and executing conservative closure of an open gingival embrasure in a periodontally healthy patient.
Use when
IPR + orthodontic space closure: triangular crowns or diverging roots with intact interdental bone.
Direct composite: orthodontics undesired and defect driven by tooth form / contact position rather than root divergence; also to complete fill after IPR and space closure.
Protocol
Control etiology and inflammation first; treat periodontitis and correct traumatic interdental hygiene.
Measure BC–CP (anesthetize, sound to the crest with a rubber stop). Plan the apical-most contact at about 4–5 mm from the crest (papilla present in 98% of cases at ≤5 mm, 56% at 6 mm, 27% at 7 mm).
IPR route: reduce about 0.5–0.75 mm per involved mesial surface with a medium diamond strip to flatten the triangular proximal surface; close the space orthodontically; consider root paralleling when roots diverge.
Composite route: diagnostic wax-up and silicone index; isolation (rubber dam, or retraction cord with Teflon tape) to expose the subgingival contact area; 37% phosphoric acid etch on sound enamel (15–30 s), adhesive, incremental build-up lowering and lengthening the contact; consider a sectional matrix system to control proximal contour and contact position.
Use papilla compression as a guide: mild blanching acceptable, avoid sustained ischemia or trauma.
Narrow the tooth visually (move labial line angles inward; open labial embrasures) and polish; verify the emergence profile is flossable.
Cautions and limits
Esthetic ceiling: contact extended more than about 1.5 mm beyond normal, or width-to-length ratio of 0.87 or greater, looks unnatural.
Papilla lost to crestal bone destruction cannot be resurrected by IPR or resin: consider regenerative or soft-tissue augmentation or prosthetic masking after periodontal control.
Proximal composite build-ups are less durable than full coverage but conservative, reversible, and repairable (4-year clinical evaluation of direct composite additions for space closure supports their use).
Finish stripped surfaces to below 0.2 µm roughness and apply remineralizing agents, as with any IPR.
Evidence summary
Recommendations derive mainly from review articles, a case report with commentary, and a 4-year clinical evaluation of direct composite build-ups; there is no head-to-head randomized comparison of IPR with space closure vs direct composite for black triangles.
Direct composite diastema closure: preventing a black triangle
Scope: Technique for closing a midline or anterior diastema with direct composite so the new contact is carried apically and the papilla is supported, rather than leaving an open gingival embrasure.
Use when
Periodontally healthy patient with a diastema where the papilla is intact and the restorations will be bonded to sound enamel.
Contact point can be lengthened apically to within about 5 mm of the bone crest.
Protocol
Confirm periodontal health. Measure or estimate the distance from the planned contact to the alveolar crest and aim to bring the contact within about 5 mm (papilla fills the space nearly always at 5 mm or less; predictability falls as the distance increases).
Plan proportions with a diagnostic wax-up and silicone index; check width-to-length so the closed space does not over-widen the incisors.
Gain cervical access: rubber dam or retraction displaces the gingiva so composite can be placed in the zone the tissue occupied. Some clinicians prefer cotton-roll isolation to keep the papilla visible; in either case the margin should sit slightly below the gingival crest.
Matrix: contour a clear polyester strip so its gingival edge extends below the free gingival margin. Protect the adjacent tooth with Teflon tape. Avoid wedges; they lift the matrix and leave an open cervical space under the contact.
Build from the gingival and palatal aspects first, using the index or an injection template, to create a smooth convex emergence profile; then close facially. A thick putty or light-body PVS index that acts as a physical stop limits overfilling and protects tooth width.
Lengthen the contact apically with the cervical increment; mild papilla blanching is an acceptable guide, sustained ischemia is not.
Use a nanofilled or supra-nano composite in the emergence and layering zone for contour hold and polish; flowable composite is acceptable with an injection technique, with interproximal isolation so it does not polymerize onto neighboring teeth.
If full closure would over-widen the incisors, open the facial embrasures and keep the flat reflective surface narrow (optical narrowing) while still extending the contact cervically.
Finish and polish the proximal and cervical surfaces with descending-grit strips and silicone polishers; confirm the emergence is smooth and flossable.
Cautions and limits
If the contact-to-crest distance remains above about 5 mm, a black triangle may persist despite perfect technique; counsel the patient beforehand.
Wedged, flat-profile matrices are the classic cause of an iatrogenic cervical gap.
Overcontoured or rough subgingival composite promotes plaque retention and papilla inflammation.
Rubber dam vs. cotton-roll isolation is a clinician preference with no head-to-head data.
Evidence summary
Evidence is mainly case reports, technique descriptions and short-term clinical evaluations (up to 4 years) of direct diastema closure; no randomized comparison of matrix or isolation methods for black triangle prevention.
Diastema: diagnosis and choosing a closure approach
Scope: Etiology-based work-up and selection among orthodontic, restorative, frenal and periodontal/prosthetic management of a midline or anterior diastema (space of 0.5 mm or more, most often between the maxillary central incisors).
Use when
Any patient presenting with anterior spacing, before choosing between orthodontics, bonding, veneers or surgery.
Mixed-dentition patients: most midline diastemas are a normal developmental (“ugly duckling”) stage.
Protocol
History, clinical and radiographic exam. Record diastema size, crown length-to-width proportions, occlusion and anterior guidance, wear, oral habits, and the labial frenum attachment.
Identify the cause: frenum attachment, tooth-size or arch discrepancy, habits, pathologic migration, missing or undersized lateral incisors, or periodontal disease. The cause determines the treatment.
Perform tooth-size (Bolton) analysis. Generalized spacing or an interarch discrepancy usually means orthodontics and/or recontouring rather than bonding alone.
Mixed dentition: defer active treatment and reassess after canine eruption unless the diastema is very large.
Control active disease (periodontitis, gingival inflammation) before any closure.
Select the approach. Orthodontics (fixed, sectional or aligners): tooth/arch discrepancy, generalized spacing, tilted incisors, larger or multiple spaces; plan retention. Direct composite: small to moderate space, good enamel, minimally invasive single visit. Veneers (sectional or full): when shape or color must change as well; sectional veneers preserve more enamel. Frenectomy: only when an abnormal frenum contributes, ideally combined with orthodontics and performed after orthodontic closure. Periodontal/prosthetic: recession, inadequate keratinized tissue, pathologic migration; may need grafting and a resin-bonded bridge.
Plan with a smile analysis and diagnostic wax-up or mock-up to set ideal proportions and avoid over-contouring and black triangles.
For a space larger than roughly 2–3 mm, or when closure alone would make the teeth disproportionately wide, close part of the space orthodontically first, then finish with restorative recontouring.
Direct composite: shade selection, isolation, minimal or no enamel preparation, incremental layering bonded to mesial and distal enamel, careful emergence-profile contouring, finishing and polishing. See the protocol on preventing a black triangle during diastema closure.
Retain: relapse is a recognized problem, especially at the midline; provide retention after orthodontic closure.
Cautions and limits
Frenectomy alone is unpredictable; closure is far more reliable with concomitant orthodontics.
Orthodontic movement is usually deferred until the permanent canines erupt (earlier only for very large diastemas).
Composite closure is technique-sensitive; shade mismatch and chipping can occur but are generally repairable.
Closing the full space restoratively can produce disproportionately wide teeth or a black triangle; plan proportions first.
Evidence summary
Support is mainly reviews, clinical reports, case series and short-term clinical evaluations (up to 4 years) of direct composite and sectional veneer closure, plus a frenectomy outcome study; no randomized comparison of orthodontic, restorative and surgical strategies.
Last updated 2026-10-10.
Sources
Diastema — Boushell LW, Journal of Esthetic and Restorative Dentistry (2009)
Retention after orthodontic closure of a midline diastema
Scope: Retainer selection, wear schedule and relapse-risk management after orthodontic closure of a maxillary midline diastema.
Use when
Any orthodontic closure of a maxillary midline diastema; this is one of the most relapse-prone corrections.
Protocol
Address the cause before or during closure; residual etiology drives relapse (for example, an abnormal frenum, a missing or small lateral, or a habit).
Assess relapse risk at the outset: larger pretreatment diastema and a positive family history are the strongest predictors; a large space warrants more aggressive, permanent retention.
Avoid leaving residual incisor proclination (the post-treatment change most associated with reopening) and finish with good interincisal contact.
First choice: a bonded wire on the palatal surfaces of the maxillary central incisors, which provides compliance-independent, indefinite retention. In a long-term series these lasted a mean of about 17 years with roughly 2% yearly breakage and no measurable periodontal harm to the central incisors.
Optional adjunct: a vacuum-formed (or Hawley) removable retainer in addition to the bonded wire for added security. If used alone, prescribe full-time wear for about 4–6 months, then night-time wear long-term.
If an abnormal frenum is genuinely implicated, perform frenectomy after orthodontic closure, not before. Fiberotomy or excision of compressed interdental tissue is sometimes added; supra-alveolar fiber remodeling continues beyond 4–6 months, so retain for more than 12 months.
Recall periodically to check the bonded wire for debonding or breakage and for unwanted movement such as torque change or the “X-effect,” which is more frequent with maxillary bonded retainers.
Consent: document that retention is effectively lifelong and that relapse can occur even with good compliance.
Cautions and limits
Reported relapse approaches about 49% when any measurable reopening is counted; patients should hear this before treatment.
Retainers worn only 1–2 years carry long-term relapse risk.
An unnoticed debonded wire is a common route to relapse; the patient needs to report it promptly.
Do not rely on a single retainer type: no high-quality evidence defines the ideal type or duration.
Evidence summary
Minimal. Recommendations draw on diastema-specific follow-up studies and case series (bonded retainer longevity, relapse incidence, predictors), a Cochrane review that found no clear stability difference between full-time and part-time removable wear, and survey data on practice patterns. There is no randomized comparison of retention regimens specifically for diastema closure.
Scope: Hierarchical esthetic diagnosis from face to smile frame to individual teeth and gingiva, with standardized records, before any esthetic or restorative treatment is planned.
Use when
Planning veneers, bonding, diastema closure, crown lengthening, orthodontics or any smile makeover.
Establishing a reproducible baseline for pre/post comparison.
Protocol
Records. Capture a reproducible photo and video series: full face at rest and smiling, close-up smile frame, and retracted intraoral views, ideally with a millimeter reference on the gingiva. Dynamic video lets you capture the fullest smile frame by frame; it shows more gingival display than a static posed image.
Macroesthetics (face). Assess facial symmetry, vertical proportions, facial and dental midlines, interpupillary line as the horizontal reference, profile, lip fullness and nasolabial angle. Reference any occlusal cant or midline deviation to these landmarks. Plan face first: set central incisor position and length relative to the face and lips, then work outward.
Miniesthetics (smile frame). Evaluate: tooth display at rest (about 1–4 mm of central incisor; more in younger women, less in older men); smile line and gingival display (excessive display is generally judged unattractive); smile arc (incisal curve parallel to the lower lip is most attractive, inverted least); buccal corridors (minimal preferred); smile index and side-to-side symmetry; incisal edge position relative to the lower lip, verified with “f” and “v” sounds.
Microesthetics (teeth and gingiva). Central incisor width-to-length ratio (roughly 75–80%; ratios above about 85% look short and square); tooth-to-tooth proportions (lateral about two-thirds of the central width, canine about four-fifths of the lateral; the golden proportion is generally not preferred); gingival margin levels (centrals level with canines, laterals about 1 mm more coronal), zenith positions, papilla height, symmetry, color, recession and black triangles; tooth shape, color, alignment, contacts, embrasures and surface texture.
Note interactions: closing a diastema widens teeth and raises the width-to-length ratio, which may call for crown lengthening or a combined approach.
Document with a standardized instrument (for example the Smile Esthetic Index, the Dental Esthetic Screening Index, or a pictorial smile chart) so pre- and post-treatment findings are comparable.
Use a digital smile design or mock-up to preview the facially driven plan with the patient before irreversible steps.
Cautions and limits
Numeric norms are population averages from perception studies; individual and patient-preferred results vary, and professional and lay preferences differ.
Posed static photos understate dynamic gingival display and smile asymmetry.
Evaluate the smile with the patient, not only on images: confirm what they perceive as the concern.
Evidence summary
Mostly perception studies, observational studies, reviews and opinion pieces; numeric ranges vary between studies and populations. Digital smile design accuracy studies are recent and small.
Measuring tooth and gingival display at rest and in smile
Scope: Standardized capture and measurement of maxillary incisor display at rest and gingival display at full smile, with reference values and differential diagnosis when display is abnormal.
Use when
Setting incisal edge position and length before restorative or orthodontic treatment.
Evaluating a gummy smile or a lack of tooth display, and choosing between orthodontics, crown lengthening, lip repositioning, botulinum toxin or orthognathic surgery.
Protocol
Capture dynamically. Use standardized video rather than only posed photographs, then select the maximal-display frame. Posed smiles underestimate lip dynamics; spontaneous smiles show more gingiva.
Position: natural head position, camera lens at the level of the maxillary incisal edge, with a calibrated reference (for example facial-reference glasses with known-distance targets) to set the scale.
Record three positions: (1) lips in repose (patient says “Emma” and lets the lips part slightly) for minimum tooth display; (2) maximum display (patient shows the gums and smiles fully, with eye-squint, to obtain the Duchenne smile) for maximum lip dynamics; (3) a social smile.
Measure vertically: incisal edge to lower border of the upper lip at rest; free gingival margin of the central incisor to the lower border of the upper lip at full smile. Use digital calipers on calibrated images or directly in the mouth.
Compare with reference values. At rest, central incisor display is about 1–4 mm (about 3 mm in a younger woman; 1 mm or less in an older man; none is common with incisal wear). At full smile, about 1–2 mm of gingiva is typical; 3–4 mm or more is generally classed as a gummy smile, but tolerance varies (clinicians accept less than laypeople).
Classify lip form at rest (straight 0–3 mm, moderate more than 3–6 mm, high more than 6 mm, by the height difference between the most superior vermilion and the commissure vermilion) and smile line (high, average, low).
Use the canine tip relative to the upper lip at rest as an additional landmark; it is less variable than the central incisor.
If display is abnormal, separate causes using clinical and cephalometric variables (upper lip length and elevation, interlabial gap, anterior maxillary height, occlusal plane angle): soft tissue (short or hyperactive lip), skeletal (vertical maxillary excess) or dentogingival (altered passive eruption). Direct treatment accordingly.
Record the measurements and frames in the chart for pre/post comparison.
Cautions and limits
Values are reference ranges, not targets: display depends on lip length, curvature, tone, age and sex.
Display declines with age; maximal incisor display in smile or speech is similar from the teens through the 30s and falls significantly after about 40.
Sex differences in display reflect lip dynamics and facial proportion; the width-to-length ratio of the central incisor does not differ by sex, though absolute tooth size is somewhat larger in men.
A single static photograph can mislead: confirm findings on video.
Evidence summary
Reference values derive from cross-sectional and observational studies, a meta-analysis of incisor dimensions, and clinical protocols from expert authors; populations and methods differ, so ranges vary between studies.
Scope: Diagnosing the cause of excessive gingival display (more than about 3–4 mm of gingiva on smile) and selecting treatment accordingly.
Use when
Patient presents with excessive gingival display, or a smile analysis shows gingival display beyond the patient's or clinician's tolerance.
Planning anterior restorative or orthodontic treatment where gingival display affects the result.
Protocol
Measure display at rest and in smile on video (see the protocol on measuring tooth and gingival display). Record upper lip length and mobility, passive eruption status (CEJ-to-bone distance on sounding), incisor position and wear, and maxillary vertical height.
Identify the cause or causes. The most common presentation is a hypermobile upper lip combined with altered passive eruption (about 45% of patients in one series), so look for coexisting causes.
Altered passive eruption: esthetic crown lengthening (gingivectomy, or apically positioned flap with osseous resection when the bone crest is near the CEJ). Preserve about 3 mm from CEJ to bone for supracrestal attachment; allow 3.5–4 mm in thin phenotypes to offset rebound.
Hypermobile upper lip: botulinum toxin A as the first non-surgical option (targets such as the levator labii superioris alaeque nasi, levator labii superioris, zygomaticus minor, or the “Yonsei point”; reported doses of roughly 1.25–7.5 U per side; display reduced by about 2.5 mm, peak effect at 2–4 weeks, lasting about 12–24 weeks, so maintenance is needed). Lip repositioning surgery lasts longer. Four-point injection schemes have outperformed two-point schemes.
Short or hypotonic lip: lip lift for a truly short lip; hyaluronic acid lip augmentation for volume and contour.
Dentoalveolar extrusion or incisor supraeruption (often Class II division 2 or worn teeth): orthodontic intrusion, often with miniscrews. Prefer an ortho-restorative approach over crown lengthening for worn, supraerupted teeth.
Vertical maxillary excess: Le Fort I impaction is definitive for severe cases. Lip repositioning is a less invasive option for mild (about 2–4 mm) to moderate (about 4–8 mm) excess.
Multifactorial or severe, surgery declined: combination therapy (crown lengthening, botulinum toxin and hyaluronic acid lip augmentation). One 18-month case series reported display falling from 4–9 mm to about 1.5 mm.
Select by severity, number of causes, the invasiveness the patient will accept, and the durability required. Use minimally invasive options (toxin, hyaluronic acid, orthodontic intrusion) for milder cases and orthognathic surgery for true skeletal excess.
Gummy smile: match the treatment to the cause.
Cautions and limits
Botulinum toxin is not indicated when the sole cause is altered passive eruption, gingival thickening or incisor supraeruption; display above about 5 mm may not reach the cosmetic threshold with toxin alone.
Lip repositioning shows partial relapse (about 25% by 12 months or later); pre-operative toxin, spacers or combined crown lengthening may improve stability.
Using one technique for every patient fails; the cause determines the treatment.
Orthodontic intrusion with miniscrews is supported mainly by finite-element and review data; plan root and anchorage safety.
Tolerance varies: orthodontists tend to find more than 2 mm of display unattractive while laypeople often accept up to about 4 mm.
Evidence summary
Botulinum toxin has the strongest support (randomized trials, systematic reviews and meta-analysis). Crown lengthening and lip repositioning are supported by reviews and a clinical study showing improved smile attractiveness. Combination therapy rests on a recent case series; orthodontic intrusion rests on a systematic review and finite-element data. There is no head-to-head randomized comparison of all options.
Esthetic crown lengthening for altered passive eruption: technique and biologic width
Scope: Diagnosis, subtype-based technique selection, open-flap surgical sequence and biologic width targets for esthetic crown lengthening in altered passive eruption (APE).
Use when
Excessive gingival display with short clinical crowns where APE is the cause (see the protocol on gummy smile by etiology).
A healthy, non-inflamed periodontium after phase I therapy.
Protocol
Diagnose and subtype. Use transgingival bone sounding to find the crest-to-CEJ relationship, and assess keratinized tissue width, incisal edge position, CEJ location and lip line at rest and in smile. Type 1 has wide keratinized tissue and Type 2 normal; subgroup A has the crest about 1.5 mm apical to the CEJ and subgroup B has the crest at the CEJ.
Select the technique. Type 1A: gingivectomy alone. Type 1B (the most common): flap with ostectomy. Type 2A: apically positioned flap. Type 2B: apically positioned flap with osseous resection. Flapless surgery gave comparable 12-month results with less postoperative pain and swelling, but is technique-sensitive, limits visualization of bone removal and is unsuitable for Type 2B.
Prepare. Complete phase I therapy (scaling, hygiene instruction) and resolve inflammation about one week before surgery. Plan the new margin from a facially driven wax-up or digital smile design, with a central incisor width-to-length ratio of about 75–85% and planned zenith positions. Make a surgical guide; CBCT-based double-guide workflows can transfer both the gingivectomy line and the bone level.
Anesthesia and marking. Infiltrate buccally and palatally; use the guide or a periodontal probe to mark bleeding points for the new margin.
Internal bevel incision. Make a scalloped submarginal incision with a #15c blade, following CEJ anatomy from mesial to distal line angles and preserving the papillae. Extend as needed (often premolar to premolar).
Sulcular incision and collar removal. Free and excise the marginal gingival collar.
Flap. Elevate a full-thickness mucoperiosteal flap buccally to expose the CEJ and crest, without releasing beyond the mucogingival junction.
Ostectomy. Where the crest is less than about 3 mm from the CEJ, remove bone with a round bur, chisels or piezo under irrigation to reach the target crest-to-CEJ distance. Limit resection to the buccal aspect and preserve interproximal bone.
Osteoplasty. Recontour thick or irregular buccal bone to a festooned architecture matching the planned scallop.
Reposition and suture. Replace the flap with the margin about 3 mm coronal to the new crest; close with interrupted or vertical mattress sutures (for example 5-0 polypropylene).
After care. Chlorhexidine rinse, suture removal at about 7 days, and reviews at 6 weeks and again at 3–12 months for maturation.
Biologic width targets. Classic mean dimensions are sulcus 0.69 mm, junctional epithelium 0.97 mm and connective tissue attachment 1.07 mm (about 2.04 mm attachment, about 2.73 mm supra-osseous soft tissue). Commonly cited targets are about 3 mm from crest to CEJ or restorative margin; some protocols leave 2–2.5 mm of crest-to-CEJ distance and aim for about 3 mm of supracrestal attachment. These targets differ between protocols; do not average them.
Individualize. Biologic width varies widely between patients (reported 2.67–5.00 mm), so measure the patient's own supra-osseous gingiva by bone sounding.
Plan for rebound. Thick phenotypes show more coronal regrowth; consider about 3.5–4 mm of bone reduction and be prepared for secondary refinement. Some creep (about 0.4–0.45 mm) is expected over 12 months even with correct technique.
Cautions and limits
Over-resection in the esthetic zone risks black triangles, flattened papillae and long clinical crowns; keep ostectomy buccal and preserve interproximal bone.
Operating on an inflamed periodontium, or leaving less than about 3 mm of crest-to-margin tissue in a thick phenotype, predicts rebound.
Gingivectomy alone is appropriate only when the crest is at least about 1.5 mm apical to the CEJ (Type 1A).
Numeric biologic width targets are not uniform across the literature.
Evidence summary
Support includes randomized trials of flap and flapless approaches, guided planning and diode laser use, prospective and 12-month stability studies, a systematic review of adjacent-site effects and narrative reviews; most trials are small. Two cited conference-poster abstracts in the source dossier were not included here because they had no verifiable titles.
Gingival margin rebound and stability after esthetic crown lengthening
Scope: Predicting and managing coronal rebound of the gingival margin after esthetic crown lengthening (ECL), including timing of definitive restorations and long-term stability.
Use when
Planning bone resection and flap position for ECL (see the protocol on technique and biologic width).
Deciding when to take final margin measurements or place definitive restorations after ECL.
Counseling patients on expected margin position and thick versus thin phenotype.
Protocol
Set the margin-to-crest distance. The main controllable determinant of rebound is the post-surgical distance from gingival margin to alveolar crest (GM-AC). Suture the flap with the margin about 3 mm coronal to the crest.
Know the expected rebound by GM-AC (6-month data): 1 mm or less, about 1.3–1.4 mm; 2 mm or less, about 0.9 mm; 3 mm, about 0.1–0.5 mm; 4 mm or more, net recession of about 0.15–0.26 mm rather than rebound.
Remove bone, not just soft tissue. Base the plan on the restorative and esthetic target plus the patient's own supracrestal tissue dimension. In the sources reviewed, margins were stable from 3 months when at least 3 mm of bone was removed; length gained mainly by soft-tissue excision and apical flap positioning with about 1 mm of bone removal rebounded by roughly 3 mm, and about half of teeth ended shorter than planned.
Adjust for phenotype. Thick, flat phenotypes rebound about twice as much as thin, scalloped ones (about 0.37 mm thin versus 0.70 mm thick at 6 months; about 0.5 mm more at 1 year in one study). Plan greater ostectomy in thick phenotypes rather than a uniform 3 mm cut.
Respect the time course. Most rebound occurs within 3 months and plateaus; change between 3 and 6 months was only about 0.12–0.15 mm. A 12-month study found stable margins at 3, 6 and 12 months. Take final measurements and place definitive restorations after about 3–6 months of maturation.
Consider long-term thickness. In a longitudinal analysis of six randomized trials, gingival thickness of about 1.5 mm or more at 6 months (with at least 1.5 mm of keratinized tissue) was associated with less than 0.5 mm of recession over 10 years; thickening thin sites gave the largest benefit.
Review. Recall at 3 and 6 months to confirm margin position before restorative work, and again at 12 months.
Cautions and limits
One randomized comparison of conventional versus digital planning found no correlation between margin stability and gingival thickness, so phenotype effects are not uniform across studies.
Early margin stabilization approaches (such as the GingivalStat technique in the first 15 days) rest on a small case series; evidence on the first two postoperative weeks is limited.
Margin position established correctly appeared stable for more than 15 years in one long-term series, but it is a single-author series.
Do not place definitive margins on a margin that is still maturing.
Evidence summary
Evidence comes from prospective clinical studies, a systematic review of pre-restorative crown lengthening, a 12-month clinical study, a long-term (over 15 years) series, a pooled analysis of six randomized trials on thickness, and a small case series. Magnitudes vary across studies, and the numeric figures above are quoted as reported in them.
Timing of definitive restorations after crown lengthening
Scope: How long to wait, and how to manage provisionals, before final preparation and definitive restorations after crown lengthening surgery.
Use when
Any crown lengthening followed by indirect restorations (crowns or veneers), especially in the esthetic zone.
Protocol
Identify how the length was gained. Waiting time depends on whether crown length came from adequate bone removal or mainly from soft-tissue resection and apical flap positioning.
Soft-tissue-only gingivectomy: about 6 weeks before definitive restoration.
Open-flap ostectomy and osteoplasty with adequate bone removal: wait at least 3 months; the free gingival margin is stable from about 3 months when bone was removed to match the restorative target plus the preoperative supracrestal tissue dimension.
Esthetically critical zone or several anterior teeth: allow 3–6 months for soft-tissue maturation, biologic width re-formation and final architecture.
Length gained mainly by soft-tissue resection or with inadequate ostectomy: expect prolonged rebound; delay final preparation to 9–12 months and confirm stability first.
Manage the interim with provisionals. Option A, early preparation (about 3 weeks): keep provisional margins at the presurgical level for the first 3 weeks, then prepare at or near gingival level with a knife-edge margin using the healed margin as a guide, and reline the provisional; definitive restoration still follows soft-tissue stabilization. Option B, delayed preparation: keep provisional margins at the presurgical level until stability is confirmed at 9–12 months, then complete final preparation and delivery.
Confirm before the final impression. Verify that the margin has reached the planned position, ideally within about 0.5 mm of the mock-up or planned level.
Do not place a margin into immature tissue. A shallow or absent sulcus in proliferating tissue invades the biologic width.
Cautions and limits
Time alone does not guarantee stability; the flap-to-crest position at suturing (about 3 mm) governs the result.
Rebound time course in one randomized study: about 60% of coronal migration in the first month, about 80% by 3 months, about 90% by 6 months, with minimal change from 6 to 12 months.
Early preparation protocols come mainly from a review article and expert guideline; they are not tested head-to-head against waiting.
Multiple adjacent teeth and thick phenotypes favor the longer end of the range.
Evidence summary
Moderate to limited. Support includes a randomized trial comparing one- and two-stage crown lengthening (final restorations at 6–9 months with margins within 0.5 mm of plan in 80% of patients), a randomized time-course study, prospective stability data, and review and guideline articles. The specific interim provisional schedules rest on narrative reviews and expert guidance.
Provisional restoration margin management during crown lengthening healing
Scope: Managing provisional margins, contacts and relining after crown lengthening so the provisional does not impinge on the re-forming supracrestal attachment.
Use when
Crown lengthening in teeth that will receive crowns or veneers and need a provisional during healing.
Choosing between intra-operative, early (3-week) and delayed abutment preparation (see the protocol on timing of definitive restorations).
Protocol
General rule. Keep provisional margins at or coronal to the presurgical gingival level and at least 1 mm away from the soft tissue during healing. Never place them into the immature sulcus; refine them progressively as the tissue matures.
Option 1, intra-operative preparation and relining. Prepare the abutments during surgery after ostectomy and osteoplasty, with knife-edge margins, and reline the provisional at suturing. Hold prosthetic margins at least 1 mm from the gingival level and monitor them; modify the provisional as often as the expected rebound dictates (flap position at suturing and biotype). Deliver the final prosthesis once soft-tissue stability is observed.
Option 2, early (3-week) preparation and relining. Leave the presurgical provisional untouched for 3 weeks while initial healing and connective-tissue reattachment occur (about 1 mm of peri-dental bone resorbs). At 3 weeks probing depth is zero and sulcus and papillae are still absent, so future subgingival tooth structure is still supragingival: prepare at or near gingival level with a knife-edge margin, guided by the healed soft-tissue margin, and reline a new provisional at the same level. Reported advantages: less aggressive preparation, no biologic-width interference, easy supragingival relining without retraction cord, and soft-tissue conditioning during peak regrowth.
Option 3, delayed preparation. Hold the provisional margins at the presurgical level until soft-tissue stability (9–12 months), then complete final preparation and the definitive prosthesis. This best avoids interfering with healing but prolongs the interim phase.
Manage the interdental aspect. After early preparation, modify the provisional only interproximally. Set the contact point initially about 3 mm from the interdental soft tissue and shift it coronally about 1 mm at a time as the papilla fills in, increasing interproximal convergence progressively to encourage papillary growth. Take the final impression only when the papillae show no further growth relative to the last contact position.
Margin depth in the healed sulcus. With a sulcus of 1.5 mm or less, the margin may sit about 0.5 mm subgingivally; with a deeper sulcus, place it at roughly half the sulcus depth. Maintain at least 3 mm between the restorative margin and the alveolar crest.
Staged option when keratinized tissue is sufficient. Perform a gingivectomy to the anticipated margins and place a provisional at the same visit. After about 6 weeks of soft-tissue healing, perform ostectomy in a second stage using the provisional margins as the guide, and proceed to the definitive restoration about 3 months later. This avoids exposed roots, crown margins and open embrasures during healing.
Cautions and limits
Placing a margin into immature tissue with a shallow or absent sulcus violates the biologic width because the tissue is still proliferating.
The temporary violation of supracrestal tissue in the staged option is acceptable only because the re-establishment response is delayed; ostectomy must follow.
The three sequencing protocols are described in narrative review and guideline articles; they have not been compared head-to-head in a trial.
Evidence summary
Moderate to limited. Based on a comprehensive narrative review, a periodontal-restorative interface review and a staged crown lengthening classification and guideline article; no randomized comparison of the provisional management protocols.
Managing biologic width violation by an existing restoration
Scope: Diagnosing and correcting encroachment of a restoration margin on the supracrestal tissue attachment, and replacing the restoration with a correct margin.
Use when
Persistent gingival inflammation, bleeding on probing, deeper probing depths, recession or an interproximal intrabony defect adjacent to a subgingival restoration margin.
Protocol
Diagnose. Encroachment occurs when the margin extends into the junctional epithelium and connective-tissue attachment, leaving less than about 3 mm between margin and alveolar crest. The tissue response varies with phenotype: chronic inflammation in thick phenotypes, recession or bone loss in thin ones. Confirm with probing depths, margin-to-crest measurement (bone sounding) and radiographs.
Separate violation from plaque retention. Overhangs and overcontoured margins act as plaque traps, and with meticulous plaque control some subgingival margins remain healthy. Much permanent damage (recession) stems from preparation and impression trauma rather than nominal margin position. Remove the overhang or defective restoration, control inflammation, and reassess before committing to surgery.
Initial therapy. Remove the defective restoration or provisionalize with a supragingival or well-contoured margin, and scale. Crown lengthening is done only on a non-inflamed periodontium.
Choose a method by esthetics, crown-root ratio, root anatomy, defect depth and location, keratinized tissue and restorative endpoint.
Surgical crown lengthening (apically positioned flap with ostectomy) is the standard definitive approach: osseous resection re-creates at least 3 mm between new margin and crest. Drawbacks: attachment and bone loss on the treated and adjacent teeth, longer clinical crowns, black triangles and an altered crown-root ratio, which matters most in the esthetic zone.
Orthodontic extrusion moves the tooth coronally to bring sound margin above the crest without sacrificing adjacent bone, and is preferable in the anterior esthetic zone. Trade-offs: longer treatment, higher cost, more visits and relapse tendency (circumferential supracrestal fibrotomy may be needed). Extrusion reduces only the intrabony root length, so it is more favorable to the crown-root ratio than surgical lengthening.
Controlled surgical extrusion (minimally traumatic coronal repositioning) gives rapid lengthening when orthodontic extrusion is impractical.
Deep margin elevation for shallow-depth interproximal subgingival margins: an adhesive composite step raises the margin to an equigingival or supragingival level without osseous surgery. It depends on rubber dam isolation and does not substitute for crown lengthening when the margin lies within the attachment itself; poorly executed deep subgingival composite can itself provoke inflammation.
Replace the restoration. Once tissue is healthy, place the margin by sulcus depth: sulcus 1.5 mm or less, about 0.5 mm subgingival; deeper sulcus, about half the sulcus depth; always keep at least 3 mm from the alveolar crest. Prefer supragingival or minimally subgingival margins (0.5 mm or less) where esthetics permit. Eliminate overhangs and overcontour, keep the interface smooth, and enroll the patient in plaque control and periodontal maintenance.
Consider extraction when correction would excessively compromise adjacent teeth (anterior sextant) or the tooth has an unfavorable crown-root ratio, furcation involvement or inadequate ferrule after resection; replacement by implant or prosthesis may then be more rational.
Cautions and limits
Deep margin elevation is not appropriate when the margin is inside the attachment zone.
Crown lengthening removes support from adjacent teeth; in the anterior sextant this can cause recession and black triangles.
Evidence for deep margin elevation is partly survey-based and recent; long-term controlled data are limited.
A 0.5 mm subgingival margin does not interfere with the supracrestal attachment; deeper margins do carry greater inflammation and attachment-loss risk.
Evidence summary
Moderate to limited. Based on reviews of the periodontal-restorative interface, a systematic review and meta-analysis of crown lengthening effects on adjacent sites, randomized trials of margin designs and gingivectomy versus crown lengthening, an observational study of controlled surgical extrusion, an in vitro crown-root ratio study, and recent clinical and survey data on deep margin elevation. One conference-poster abstract in the source list was omitted because it had no verifiable title.
Orthodontic extrusion (forced eruption) to restore biologic width
Scope: Rate, force, fiberotomy decision and retention for orthodontic extrusion used to relocate restorative margins supragingivally or to develop tissue.
Use when
Biologic width violation, inadequate ferrule, subgingival or subcrestal fracture or caries, particularly in the esthetic zone where resective surgery would cause recession or black triangles.
Periodontal infrabony or papillary defects and implant site development (slow extrusion without fiberotomy).
Protocol
Select candidates. Confirm adequate residual root length and a favorable final crown-root ratio. Contraindications: active inflammation, ankylosis, hypercementosis, vertical root fracture and root proximity. If residual root length or crown-root ratio would be unfavorable, consider extraction and replacement.
Know the biology. Extrusion reduces only the intrabony root length and keeps crown length constant, so it preserves the crown-root ratio better than surgical lengthening (which shortens both) and keeps the gingival architecture intact. It moves plaque coronally rather than apically, so it can be used in a reduced periodontium.
Choose the goal, which sets rate and fiberotomy. To bring bone and gingiva with the tooth (implant site development, infrabony or papillary defects): slow extrusion with light force and no fiberotomy. To lengthen the clinical crown while leaving margin and bone behind (biologic width restoration or ferrule): faster extrusion with repeated circumferential supracrestal fiberotomy (CSF) to prevent the marginal tissues following the tooth.
Force and appliance. Use light, continuous extrusive force to limit root resorption, ankylosis and unwanted intrusion of anchor teeth. Fixed appliances (brackets and archwire on anchor teeth with elastics or NiTi wire) are preferred over removable ones, which depend on compliance. Multibracket extrusion is effective and, unlike surgical or magnetic extrusion, does not require prior root canal treatment of the target tooth.
Representative sequence. Control inflammation first (supragingival provisional for about 6 weeks); bond passive brackets to anchor teeth; apply a NiTi wire for about 3 months while reducing the provisional incisally or palatally to allow eruption; perform supracrestal fiberotomy to release Sharpey fibers; then hold with a passive wire for retention before removal.
Retain. Relapse is the major complication, driven by the elasticity and slow remodeling of stretched supra-alveolar fibers, which continues beyond 4–6 months. Plan retention of at least 12 months, or at least as long as the active extrusion time, before the definitive restoration.
Fiberotomy. CSF reduced relapse in a long-term prospective study (most for rotational relapse, in the maxillary anterior) without clinically significant increase in sulcus depth or loss of attached gingiva, but systematic-review-level evidence for CSF is weak, and repeated CSF can occasionally provoke osseous resorption of adjacent bone. It does not replace mechanical retention.
Expect trade-offs. Compared with surgical crown lengthening: longer treatment, more visits, higher cost, and relapse that may need repeat fiberotomy.
Cautions and limits
Excess force risks root resorption, ankylosis, or intrusion of anchor teeth.
A clinical study of forced extrusion of extensively damaged teeth reported about 94% survival over a mean of about 3.3 years, with relapse the dominant complication.
Evidence is mainly reviews, case series and small clinical studies; the CSF data are largely from a single long-term prospective study.
The slow-versus-fast and fiberotomy rules come from guidelines and narrative reviews rather than head-to-head trials.
Evidence summary
Moderate to limited. Support is from guideline and narrative reviews, a systematic review, a case series and a clinical study with health economic follow-up, an in vitro crown-root ratio study, a long-term prospective study of fiberotomy, and a systematic review that rated adjunct support (including CSF) as weak.
Choosing between orthodontic extrusion and surgical crown lengthening
Scope: Comparing orthodontic extrusion with surgical crown lengthening on periodontal outcome, crown-root ratio, esthetics, survival and cost to select an approach for teeth with biologic width violation or insufficient ferrule.
Use when
Selecting a method to gain supragingival tooth structure before restoring a tooth with a subgingival or subcrestal margin (see the protocols on orthodontic extrusion and biologic width violation).
Protocol
Favor orthodontic extrusion for anterior esthetic-zone teeth, subcrestal or subgingival defects where preserving bone and gingival symmetry is paramount, and cases needing a better crown-root ratio.
Favor surgical crown lengthening for posterior or non-esthetic sites, when rapid single-stage correction is preferred, when adjacent bone can tolerate resection, and when patient compliance or treatment duration makes orthodontics impractical.
Weigh periodontal effects. Extrusion preserves or augments supporting bone, directs plaque coronally (so it can be used in a reduced periodontium even with imperfect hygiene), tends to reduce pocket depth and widen attached gingiva, and affects adjacent teeth little. Surgical lengthening requires osseous reduction; a systematic review found attachment effects on the treated and on adjacent and non-adjacent teeth, with recession and black triangles possible.
Weigh crown-root ratio. Extrusion reduces only intrabony root length; surgical lengthening lengthens the clinical crown and reduces bony support. In one in vitro study the effective crown-root ratio was about 22% lower with extrusion at 2 mm and about 30% lower at 4 mm, compared with surgical lengthening.
Weigh esthetics. Extrusion maintains gingival architecture; surgical lengthening disturbs marginal contour and is disadvantageous in the esthetic zone.
Weigh burden and cost. Extrusion takes longer, needs more visits, costs more and has a relapse tendency requiring repeated fiberotomy. Surgical lengthening is a single, faster, generally cheaper procedure. These are qualitative judgments, not formal cost-effectiveness analyses.
Consider extraction when either approach would leave an inadequate ferrule or an unfavorable final crown-root ratio.
Cautions and limits
No randomized trial directly comparing restoration survival between the two techniques was found; the evidence is case series, narrative reviews, in vitro data and one health-economic study.
Extrusion survival figure: about 94% over a mean of about 3.3 years in one clinical study of extensively damaged teeth, with relapse the dominant complication; there is no matched comparative survival figure for surgical lengthening.
Extrusion is not free of attachment consequences: in a canine experiment, circumferential fiberotomy during extrusion did not fully prevent coronal migration of the attachment and was associated with gingival recession and connective tissue attachment loss.
Formal health-economic comparison data are largely absent.
Evidence summary
Minimal. No head-to-head randomized comparison of survival or cost. Evidence consists of narrative and systematic reviews, case series, an in vitro crown-root ratio study, a health-economic analysis of extrusion alone, and an animal experiment.
Ferrule requirements for endodontically treated anterior teeth
Scope: Dimensions of an adequate ferrule, what to do with a partial ferrule, and how to regain a ferrule before restoring an endodontically treated anterior tooth.
Use when
Planning a crown, post and core or endocrown on an endodontically treated tooth with limited coronal structure.
Protocol
Target a complete 360° ferrule of sound tooth structure apical to the core: height at least 1.5–2.0 mm and axial dentin thickness at least 1.0 mm. A meta-analysis found that a ferrule height of 2 mm or more raised fracture resistance by a mean of about 165 N, and one premolar in vitro study found resistance fell about 37% going from a 2 mm ferrule to none.
Thickness. Residual dentin of at least 1.0 mm is the practical floor; in vitro work on incisors showed resistance increasing with thickness, highest at 1.5 mm or more.
Wall form. Keep ferrule walls roughly parallel and preserve coronal wall height of at least 3 mm above the gingival margin where possible; this further improves survival independent of the ferrule.
If a complete ferrule is not achievable, an incomplete ferrule is still protective. In a systematic review of 19 in vitro studies a partial ferrule significantly increased fracture resistance compared with none; two or more opposing residual walls were most beneficial.
Do not rely on the post or core to compensate. An adequate ferrule lowers the biomechanical impact of the post and core system, cement and crown material. In anterior teeth, 2 mm ferrules withstood higher loads regardless of core type, and fiber-reinforced composite cores increased resistance and reduced catastrophic, non-repairable fractures. Posts mainly improve prognosis when substantial structure is missing (fewer than two walls, no ferrule); with an adequate ferrule and two or more walls, a post adds little.
When insufficient coronal structure remains, re-establish a ferrule before the definitive restoration rather than accepting a ferrule-free preparation, which carries a high failure rate. In the anterior esthetic zone, orthodontic extrusion is preferred over surgical crown lengthening to gain ferrule height while preserving bone and gingival architecture.
If neither method is feasible, a poor outcome is likely and extraction and replacement should be weighed.
Cautions and limits
A circumferential ferrule improved success of fiber-post-restored teeth in a direct meta-analysis (relative risk about 1.28), but the pooled indirect survival analysis was not statistically significant; evidence quality is moderate.
Numeric thresholds come mainly from in vitro fracture-resistance studies and systematic reviews of them; clinical trial support is more limited.
In the finite-element and fracture studies reviewed, a ferrule shifted peak stress deeper in the root and favored shallower, more repairable fracture patterns; failure mode matters as much as load.
Evidence summary
Moderate. Based on systematic reviews and meta-analyses (including one 2026 review of ferrule dimensions and one on circumferential ferrules with fiber posts), a systematic review of in vitro studies on incomplete ferrules, a classic literature review, and in vitro fracture and finite-element studies on premolars and anterior teeth.
Recording centric relation: sequence, techniques and materials
Scope: Sequence for recording centric relation (CR) for mounting casts, with technique categories, recording materials and reproducibility evidence.
Use when
Mounting casts for diagnosis or full-arch restorative, prosthodontic or splint therapy where a repeatable condylar reference position is needed.
Protocol
Definition. CR is the maxillomandibular relationship, independent of tooth contact, in which the condyles articulate in the anterior-superior position against the posterior slopes of the articular eminences, with the mandible restricted to pure rotation. It is a repeatable reference position for mounting casts.
Reduce splinting and deprogram. Address inflammation and muscle splinting, and deprogram the proprioceptive memory of maximal intercuspation: anterior jig (Lucia jig), leaf gauge, anterior deprogrammer, cotton rolls over the molars, or a period of biting to fatigue the elevators.
Position the patient reclined about 120° to favor condylar seating and relaxation.
Seat the condyles. Either operator-guided (bimanual manipulation, chin-point guidance, power centric) or patient-determined (Gothic arch tracing, swallowing, free closure after deprogramming). Operator-guided methods are criticized for force variability and a protective protrusive reflex if too much force is used; patient-determined methods are less likely to exceed physiologic limits.
Verify repeatability. The mandible should return to the same position on repeated hinge closures (for example, the lower incisors meeting the same jig indentations) before recording.
Record at a slightly opened vertical dimension without tooth contact, using a rigid material, then mount with a facebow transfer. Polyvinyl siloxane and polyether performed best for reproducibility and are preferred over wax for the definitive record; unrefined wax wafers with bimanual manipulation still showed strong precision and efficiency.
Digital options. Jaw-tracking devices record multiple closures against an anterior plateau; patient-reported comfort was comparable to bimanual manipulation, though conventional recording was faster.
Choose by familiarity. A best-evidence consensus found chin-point guidance, bimanual manipulation, power centric, Gothic arch tracing, leaf gauge and anterior deprogramming devices comparable in precision, with clinician experience the critical variable.
Cautions and limits
Different CR records reproduce slightly different condylar positions (median spatial differences about 0.48–0.79 mm between methods), though repeat-record variability was similar across techniques.
One digital study found higher reproducibility with a frontal deprogrammer and Gothic arch device (about 0.12 mm) than with bimanual manipulation and leaf gauge (about 0.21–0.23 mm); this is a preliminary report.
In edentulous patients, Gothic arch recordings had the best reproducibility but needed more chair time.
A systematic review found no high-level evidence that CR is a diagnostic or therapeutic gold standard; treat it as a technically useful, repeatable reference position rather than a validated physiologic ideal.
Evidence summary
Moderate to limited. Based on a best-evidence consensus statement, a biologic-perspective review, randomized and cross-over trials on muscle activity and splint recording, observational reproducibility studies, MRI work on condylar position, and preliminary digital studies.
Determining and verifying occlusal vertical dimension (OVD)
Scope: Combining methods to determine OVD for full-mouth or complete denture rehabilitation, and verifying it before definitive restorations.
Use when
Planning complete mouth rehabilitation, complete dentures, or any treatment that increases or restores OVD.
Protocol
Accept that there is no gold standard. Combine converging methods rather than relying on one measurement. The habitual rest position is unstable (posture, fatigue, central regulation) and itself adapts after OVD changes. Interocclusal distance averages about 3 mm but ranges from about 1 to 9 mm in healthy patients.
Rest position minus freeway space. Establish the habitual rest position, then subtract about 2–4 mm (commonly 3 mm). Most widely used, limited by rest-position instability.
Phonetics. Sibilant (“s”) sounds produce a minimum gap of about 1 mm in the premolar region (closest speaking space); “m” sounds help establish rest position; there should be no tooth contact in speech.
Facial esthetics and proportions. Assess lower facial third harmony, lip competence and tooth display.
Other aids. Swallowing (determines OVD and CR functionally), pre-extraction records (photographs, profile tracings, prior casts, a well-adapted existing denture), and restorative space requirements (material thickness, anterior guidance, tooth display, minimizing preparation and avoiding endodontics). Anthropometric and cephalometric methods (for example finger length correlations) have been proposed; routine use of orthodontic cephalometric norms is discouraged as unreliable.
Evaluate before committing. A 2025 systematic review concluded that increasing OVD should be preceded by an evaluation phase using interim or transitional restorations, or a removable appliance, to confirm functional and esthetic tolerance before irreversible treatment. Transitional bonding (direct composite or CAD/CAM) is a reversible way to trial a new OVD.
Verification criteria. Adequate freeway space at rest, sufficient interocclusal space for the prosthesis, no tooth contact during speech, patient acceptance and comfort, and an esthetically acceptable profile.
Record and transfer. Use an anterior deprogrammer to stabilize the mandible and record the intended OVD at the CR position, then facebow transfer and articulator mounting at the determined OVD with CR records.
Choose the horizontal reference. For complete mouth rehabilitation, a consensus recommends restoring partially and completely dentate patients in CR-coincident centric occlusion, since most patients do not have coincident CO and MIP and the discrepancy is associated with occlusal instability and TMD. CR is the recommended reference when posterior support is lost and no stable MIP exists.
Digital option. Intraoral and facial scans, CBCT and jaw-motion or electronic facebow tracking can be integrated in a virtual patient to determine OVD and CR, deliver a therapeutic position, and double-check it before irreversible preparation.
Cautions and limits
A consensus statement found the stomatognathic system tolerates alteration of OVD well in healthy patients, and that OVD can be restored successfully with proper diagnosis and planning, but biologic variability undercuts any single formula.
No clinical evidence was found that abraded teeth in bruxers continuously erupt to compensate; unopposed teeth do over-erupt. Lost OVD in generalized wear is generally recoverable, and space often exists where occlusal contact has been maintained.
Evidence is mainly consensus statements, reviews, case reports and technical reports; the finger-length correlation and digital workflow data are limited.
Evidence summary
Moderate to limited. Based on an American College of Prosthodontists best-evidence consensus statement, systematic and narrative reviews on OVD in complete dentures and on the evaluation phase, a randomized trial on finger-length correlation, technical reports and case reports on digital workflows.
