Recent Advances in Impression Techniques in FPD and Gingival Retraction

PART 1: IMPRESSION TECHNIQUES IN FIXED PARTIAL DENTURES (FPD)

1.1 Conventional Impression Techniques

• Polyvinylsiloxane (PVS) / Addition silicones - the gold standard conventional material; excellent dimensional accuracy, tear resistance, hydrophobic nature (requires dry field)
• Polyether (PE) - dimensionally stable, hydrophilic, good detail reproduction but stiffer set; more comfortable for patients than PVS in some cases
• Zinc oxide eugenol (ZOE) paste - historically used but largely replaced

• Single-step, two-viscosity putty-wash - most commonly used; simultaneous tray material and wash impression
• Two-step putty-wash - putty first, then reseated with wash material; risk of dimensional error at the second seating
• Double-mix single impression - simultaneous use of two viscosities of the same material

• Patient discomfort (gagging, taste, prolonged set time)
• Material distortion during removal
• Errors in pouring and storage
• Requires adequate gingival retraction to expose finish line
• Dimensional changes during shipping to the lab
• Cannot be re-scanned if the pour fails

1.2 Digital (Intraoral Scanner) Impression Techniques

• TRIOS (3Shape) - series 3, 4, and 5
• iTero Element (Align Technology)
• Cerec Primescan / Omnicam (Dentsply Sirona)
• i700 (Medit)
• CS 3600 (Carestream)
• Aoralscan 3 (Shining3D)

• Internal fit was significantly better with digital/CAD-CAM fabrication (P=0.02; SMD: -0.80; 95% CI: -1.49 to -0.10)
• Marginal fit showed no statistically significant difference (P=0.06)
• IOS can replace conventional impressions for FPD fabrication, minimizing operating time and patient discomfort
• Cement spacer thickness was an important subgroup variable

• Analyzed 18 systematic reviews (11 with meta-analyses)
• 4 of 10 in vivo studies and 4 of 7 in vitro studies reported better marginal adaptation with digital scanning
• For zirconia restorations, digital techniques outperformed conventional in 4 of 5 in vivo studies (SMDs: -0.89 to 27.2) and in all in vitro studies
• For lithium disilicate and cobalt-chromium, no significant difference was found
• No study reported conventional technique was better than digital
• Digital scanning is particularly superior for zirconia and for single/short-span partial FPDs

• All materials and techniques showed clinically acceptable marginal fit (<120 µm)
• Fully digital workflow was most promising for short-span zirconia FPDs
• Clinical data remain limited for long-span FPDs
• Gingival retraction remains a major procedural requirement regardless of impression method

1.3 Implant-Supported FPD Impressions: Digital vs. Conventional

• Conventional open/closed tray with PVS or polyether + scan bodies remains the reference standard for full-arch implant prostheses
• Digital scanning with scan bodies shows comparable accuracy for short-span implant FPDs; full-arch accuracy is still evolving
• A 2021 RCT by Derksen et al. (PMID: 33662051, Int J Prosthodont) compared CAD/CAM monolithic zirconia FDPs on ti-base abutments using digital vs. conventional impressions - 1-year follow-up showed comparable clinical fit
• The 3-year follow-up (PMID: 37699181) by the same group confirmed sustained performance of the digitally fabricated restorations

1.4 Digital Workflow and CAD/CAM Integration

1. IOS scan replaces alginate/PVS impressions
2. CAD design on-screen with virtual articulator
3. CAM fabrication - subtractive milling (zirconia, PMMA, lithium disilicate blocks) or additive manufacturing (3D printing resin models, metal frameworks via SLM/DMLS)
4. Virtual articulation replaces face-bow transfer and physical articulators
5. Digital try-in using 3D-printed provisional restorations before final fabrication

• Eliminates model pouring, trimming, and storage
• Faster turnaround (same-day restorations with chairside CAD/CAM)
• Improved patient experience (no trays, no wait)
• Design data stored permanently and retrievable
• Accurate fabrication of zirconia with superior marginal fit

1.5 Subgingival Margin Challenge for IOS

• IOS trueness is significantly compromised at subgingival margins
• Clinically acceptable results require proper gingival retraction AND a dry field
• Saliva contamination is a major confounder reducing IOS accuracy

• Without gingival displacement cord, both IOS tested exceeded 100 µm error when the finish line was deeper than 0.5 mm subgingivally
• With gingival displacement cord, trueness did not exceed 100 µm regardless of depth
• Gingival retraction cord improved scanning trueness by 90%
• A 2025 follow-up study (PMID: 41003380) confirmed these findings for interim crowns

PART 2: ADVANCES IN GINGIVAL RETRACTION

2.1 Purpose and Principles

• Conventional impressions
• Digital intraoral scanning at subgingival margins
• Ensuring a clean, dry, accessible preparation margin

2.2 Classification of Gingival Retraction Methods

A. Mechanical Methods

• Most widely used; available in cotton (twisted, knitted, braided) and non-cotton fiber types
• Sizes: 000, 00, 0, 1, 2 (increasing diameter)
• Placed dry or impregnated with hemostatic/astringent agents
• Double-cord technique: Size 00 placed first and left in place; size 0 or 1 placed on top and removed just before impression - considered the gold standard for conventional impressions
• A 2026 study by Revilla-León et al. (PMID: 41236010, J Esthet Restor Dent) evaluated retraction cord color, diameter, and Teflon tape with three different IOS systems. Findings showed: size 02 yellow-black cord (Ultrapack 02) and Teflon tape subgroups had the best trueness; all scanning discrepancies were not clinically relevant

• Emerging as a practical alternative for digital impressions
• Non-impregnated, atraumatic, easily placed and removed
• Revilla-León 2026 study confirmed Teflon tape performed comparably to size 02 cord for IOS accuracy
• Lower gingival trauma than impregnated cords

B. Chemical-Mechanical Methods (Cordless Systems)

• Expasyl (Acteon): Kaolin + aluminum chloride paste; injected subgingivally under pressure using a cannula tip; displaces tissue via physical expansion and chemical hemostasis
• Magic FoamCord (Coltenewaldent): Silicone-based foam that expands in the sulcus; cordless, less traumatic
• Traxodent (Premier): Aluminum chloride-based paste

• Impregnated cords provided the greatest displacement but also caused the greatest gingival height loss at 1 month
• For digital impressions, cordless retraction pastes or laser troughing are preferred to minimize iatrogenic tissue damage

C. Surgical / Laser Methods

• Diode lasers (810-980 nm) or Er:YAG lasers perform a micro-surgical sulcular incision (troughing) to create space
• Advantages: hemostatic, minimal trauma, no impression material contamination from retraction agents
• Used as a single-procedure method replacing cord in many modern digital workflows
• Growing adoption with digital impressions; RCT (El Ashry 2025) showed effective displacement with minimal gingival height loss

• Soft tissue management using controlled electrosurgical units
• Precise, hemostatic but requires training; avoided near implants or patients with pacemakers

D. Novel Pneumatic Gingival Retraction (2025 Advance)

• Key innovation: Combines an air-driven retraction nozzle with a built-in IOS tip + a polar coordinate-based point cloud stitching algorithm for accurate imaging during dynamic tissue displacement
• In a prospective RCT (60 participants), PGR-S achieved a mean retraction of 302.9 ± 124.9 µm
• Operating time for PGR (70.48 ± 17.90 s) was significantly shorter than cord-based methods (194.78 ± 42.81 s; P<0.001)
• Comfort, pain, and nausea scores were significantly better with PGR-S vs. cord methods
• Patients reported greater dryness with PGR-S
• Represents the current frontier of minimally invasive, fully digital gingival retraction

2.3 Hemostatic/Astringent Agents Used with Retraction

2.4 Gingival Retraction in Digital Impression Workflows

• Accurate marginal positioning depends on effective gingival retraction regardless of impression method
• Gingival retraction decreases marginal discrepancy and is essential for therapeutic, preventive, and aesthetic outcomes
• Soft tissue management for digital workflows now centers on minimizing trauma while ensuring margin visibility for IOS

• It displaces tissue enough for IOS capture
• Leaves the cord in place during scanning (unlike conventional where cord is removed just before impression)
• Minimizes tissue trauma compared to double-cord

Summary Table: Gingival Retraction Methods for FPD Impressions

Key References

1. Saeed EAM et al. (2023). The impact of digitization and conventional techniques on the fit of FPDs: systematic review and meta-analysis. BMC Oral Health. PMID: 38049754 - DOI: 10.1186/s12903-023-03628-1
2. Porto AM et al. (2025). Marginal adaptation of tooth-supported fixed restorations fabricated using digital scanning versus conventional impression techniques: An overview of systematic reviews. J Prosthet Dent. PMID: 40610310 - DOI: 10.1016/j.prosdent.2025.05.044
3. Sarafidou K et al. (2022). Evaluation of marginal/internal fit of FDPs after digital, conventional, and combination impression techniques: A systematic review. Eur J Oral Sci. PMID: 36346664 - DOI: 10.1111/eos.12902
4. Derksen W et al. (2021). Randomized Clinical Trial comparing clinical fit of CAD/CAM monolithic zirconia FDPs on ti-base abutments based on digital or conventional impression techniques - 1-year follow-up. Int J Prosthodont. PMID: 33662051
5. Derksen W & Wismeijer D (2023). Three-Year Follow-up of a Randomized Clinical Trial on Screw-Retained Monolithic Zirconia Restorations based on Digital or Conventional Impression Techniques. Int J Prosthodont. PMID: 37699181
6. Andrade Villalobos M et al. (2025). Accuracy of Intra-Oral Scanners for Full Crown Tooth Preparations with Subgingival Margins: A Systematic Review. Eur J Prosthodont Restor Dent. PMID: 39887301 - DOI: 10.1922/EJPRD_2812Matias09
7. Son YT et al. (2022). Trueness of intraoral scanners according to subgingival depth of abutment for fixed prosthesis. Sci Rep. PMID: 36456561 - DOI: 10.1038/s41598-022-23498-x
8. El Ashry MF et al. (2025). The efficacy of different gingival displacement methods for definitive digital impressions: A randomized controlled trial. J Dent. PMID: 40414276 - DOI: 10.1016/j.jdent.2025.105841
9. Xu X et al. (2025). Fully digital pneumatic gingival-retraction scanning technique: from methodology development to clinical validation. J Dent. PMID: 41130557 - DOI: 10.1016/j.jdent.2025.106192
10. Revilla-León M et al. (2026). Influence of Color and Diameter of Retraction Cords and Teflon Tape on the Accuracy of Tooth Preparations Digitized by Intraoral Scanners. J Esthet Restor Dent. PMID: 41236010 - DOI: 10.1111/jerd.70054
11. Chauhan R et al. (2025). Present status and future directions: Soft tissue management in prosthodontics. World J Methodol. PMID: 40900871 - DOI: 10.5662/wjm.v15.i4.104497
12. Son YT et al. (2025). Does Intraoral Scanning at the Subgingival Finish Line Affect the Accuracy of Interim Crowns? J Funct Biomater. PMID: 41003380

Clinical Takeaways (2025-2026)

• Digital (IOS) impressions are now equivalent or superior to conventional impressions for single-unit crowns and short-span FPDs, particularly with zirconia restorations.
• Gingival retraction remains mandatory even with digital impressions when the finish line is subgingival - cord retraction improves IOS accuracy by ~90% at deep subgingival margins.
• For digital workflows, the preferred retraction sequence is: single 00 cord or cordless paste - preserving tissue health while allowing adequate scanning access.
• Pneumatic gingival retraction scanning (Xu et al., 2025) represents the most novel development - non-invasive, fast, and RCT-validated.
• The choice of retraction cord color/diameter matters slightly for IOS accuracy, but all clinically tested options remain within acceptable limits (Revilla-León 2026).
• Impregnated cords give the best displacement for conventional impressions but cause measurable gingival height loss at 1 month - prefer non-impregnated or lower-trauma methods when tissue health is a priority.

10-Mark Exam Answers: FPD Prosthodontics

ANSWER 1: IMPRESSION TECHNIQUES IN FIXED PARTIAL DENTURES (FPD)

Introduction

Classification of Impression Techniques for FPD

1. Elastomeric impression techniques (PVS, polyether, polysulfide)
2. Non-elastomeric techniques (ZOE, plaster of Paris - rarely used)
3. Digital impression techniques (Intraoral scanning)

1. Full arch tray technique
2. Sectional tray technique
3. Triple tray / dual arch tray technique

I. Conventional Elastomeric Impression Techniques

1. Two-Step Putty-Wash Technique

• Putty (high viscosity) impression taken first using a spacer
• After setting, spacer removed, wash (light body) injected around preparation and putty re-seated
• Advantage: Good bulk for dimensional stability
• Disadvantage: Risk of tray shift at second seating; thin wash layer may tear; space created by spacer may be inadequate
• Reference: Shillingburg HT, Fundamentals of Fixed Prosthodontics, 4th ed., p. 394

2. Single-Step (Simultaneous) Putty-Wash Technique

• Both putty and wash (light-body syringe material) used simultaneously
• Light body injected around preparation while putty loaded in tray; seated together
• Advantage: No spacer needed; uniform wash layer; fewer steps
• Disadvantage: Putty may displace wash if seated too forcefully
• Reference: Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics, 5th ed., Elsevier, 2016, p. 468

3. Single Viscosity (Monophase) Technique

• One material of medium viscosity used both in tray and syringe
• Polyether is best suited for this technique due to appropriate flow and body
• Less technique-sensitive; predictable results
• Reference: Rosenstiel et al., Contemporary Fixed Prosthodontics, 5th ed., p. 471

4. Triple Tray / Dual Arch Technique

• Single impression records both the prepared arch and opposing arch simultaneously
• Thin flexible tray carries impression material on both sides
• Advantages: Reduced material use, less patient discomfort, records occlusal contacts at centric occlusion in one step
• Limitations: Inaccurate for multiple preparations, posterior tray flex, limited anterior access
• Suitable for single tooth preparations only
• Reference: Rosenstiel et al., Contemporary Fixed Prosthodontics, 5th ed., p. 474

II. Impression Materials for FPD

III. Digital Impression Technique (Intraoral Scanning - IOS)

• TRIOS (3Shape)
• iTero Element (Align Technology)
• CEREC Primescan (Dentsply Sirona)
• Medit i700
• CS 3600 (Carestream)

1. Tooth preparation and gingival retraction
2. IOS scan of prepared arch
3. IOS scan of opposing arch
4. Digital bite registration
5. CAD design → CAM fabrication (milling/printing)

• A systematic review and meta-analysis by Saeed et al. (BMC Oral Health, 2023; PMID: 38049754) found that internal fit of FPDs was significantly better with digital/CAD-CAM fabrication (P=0.02; SMD: -0.80) compared to conventional techniques
• An overview of 18 systematic reviews by Porto et al. (J Prosthet Dent, 2025; PMID: 40610310) concluded: digital scanning produced equivalent or superior marginal adaptation in the majority of studies; no review reported conventional technique was superior; digital workflows excelled particularly for zirconia FPDs
• Sarafidou et al. (Eur J Oral Sci, 2022; PMID: 36346664): all techniques yielded clinically acceptable marginal fit (<120 µm); fully digital workflow most promising for short-span zirconia FPDs

• Eliminates dimensional changes from pouring/stone model
• Reduces patient discomfort (no tray, no gag reflex)
• Faster chair time
• Digital storage and re-use of data
• Seamless CAD/CAM integration
• Environmentally friendly (no gypsum waste)

• Higher initial cost
• Reduced accuracy at subgingival margins (requires gingival retraction)
• Saliva/blood contamination significantly reduces accuracy
• Full-arch implant FPD accuracy still evolving
• Reference: Andrade Villalobos et al., Eur J Prosthodont Restor Dent, 2025; PMID: 39887301

IV. General Steps in Taking a Final Impression for FPD

1. Preparation - Complete tooth preparation; assess finish line accessibility
2. Gingival retraction - Expose subgingival finish line (detailed below)
3. Tray selection and custom tray fabrication if required
4. Adhesive application to tray
5. Mixing and loading impression material in tray; syringe light body around preparation
6. Seating the tray with steady pressure
7. Removal after complete set; sharp, single-axis pull
8. Inspection for voids, tears, incomplete margins
9. Disinfection of impression (immersion in 2% glutaraldehyde or sodium hypochlorite)
10. Pouring in Type IV or V die stone within prescribed time

ANSWER 2: GINGIVAL RETRACTION IN FIXED PARTIAL DENTURES

Definition

Objectives of Gingival Retraction

1. Expose the prepared finish line completely
2. Create adequate sulcular width for impression material to form a tear-resistant flash
3. Achieve hemostasis and dry field
4. Allow complete seating of impression tray without tissue interference
5. Provide access for IOS scanning at subgingival margins

Classification of Gingival Retraction Methods

A. Mechanical Methods

1. Retraction Cord Technique

• Twisted cord - loosely twisted fibers; easy insertion
• Braided cord - tightly braided; maintains sulcular position better
• Knitted cord - mesh structure; good absorption of medicaments

• A single cord (size 00 or 0) packed into sulcus
• Left for 5-10 minutes; removed just before impression (conventional) or left in place during scanning (digital)
• Suitable for shallow sulcus, healthy gingiva

1. First cord (size 000 or 00) packed into sulcus and left in place during impression
2. Second cord (size 0 or 1) placed on top; removed just before seating impression material
3. The first cord remains, preventing gingival rebound and hemorrhage
4. Creates greater horizontal and vertical displacement

• Reference: Shillingburg HT, Fundamentals of Fixed Prosthodontics, 4th ed., p. 378

B. Chemical-Mechanical Methods

Impregnated Retraction Cords

C. Cordless Chemical Methods (Retraction Pastes)

1. Expasyl (Acteon/Kerr)

• Contains: Kaolin (physical bulk) + 15% Aluminum chloride (hemostasis)
• Injected subgingivally using pressure syringe + fine cannula tip
• Left 1-2 minutes; rinsed with water spray
• Atraumatic; no cord placement required
• Particularly suited for digital impressions

2. Magic FoamCord (Coltenewaldent)

• Silicone-based foam material in a syringe
• Expands inside sulcus on setting; provides mechanical displacement
• Removed by rinsing; no cord needed

3. Traxodent (Premier Dental)

• 15% Aluminum chloride in paste form
• Application with blunt tip; works similarly to Expasyl
• RCT evidence (Rathod et al., J Contemp Dent Pract, 2021; PMID: 34393130): Traxodent showed the highest mean sulcular width (0.644 ± 0.22 mm), followed by Expasyl (0.590 mm) and Magic FoamCord (0.528 mm); all three produced clinically adequate displacement

D. Surgical Methods

1. Electrosurgery

• High-frequency alternating current used to perform sulcular troughing
• Precise removal of excess gingival tissue
• Achieves hemostasis simultaneously
• Contraindicated in: patients with pacemakers, near metallic implants
• Risk of irreversible tissue damage if used excessively
• Reference: Rosenstiel et al., Contemporary Fixed Prosthodontics, 5th ed., p. 461

2. Rotary Gingival Curettage

• Tungsten carbide bur or diamond bur used at low speed to remove sulcular epithelium
• Less commonly used; largely replaced by laser

3. Diode Laser Troughing

• Soft tissue diode laser (810-980 nm wavelength) performs sulcular troughing without cord
• Simultaneous cutting and coagulation
• Bloodless, precise, atraumatic
• RCT Evidence (Melilli et al., Am J Dent, 2018; PMID: 30028930): Gingival retraction was equivalent between laser and retraction cord (ΔT2-T1 = 0.65 mm cord vs. 0.66 mm laser; P=0.966); laser required significantly less time, was easier for operator, and more comfortable for patient (all P<0.001)
• Growing preference in digital impression workflows

E. Novel Pneumatic Gingival Retraction (2025)

• Combines a three-way syringe airflow nozzle integrated with an IOS tip
• Non-invasive, non-chemical, non-surgical displacement
• Mean retraction: 302.9 ± 124.9 µm
• Operating time: 70.48 ± 17.90 seconds vs. 194.78 ± 42.81 sec for cord (P<0.001)
• Superior patient comfort; no gingival tissue loss
• Represents the current frontier of minimally invasive digital gingival retraction

Comparison of Gingival Retraction Methods

Gingival Retraction for Digital Impressions - Special Considerations

• Son et al. (Sci Rep, 2022; PMID: 36456561) proved that IOS accuracy dropped below acceptable (<100 µm) when finish line was >0.5 mm subgingival without cord; with gingival cord, trueness was maintained regardless of depth, improving scanning accuracy by 90%
• For digital workflows: single cord (size 00) left in sulcus during scanning is preferred; cordless pastes also effective
• Saliva control is critical - hemostatic agents help achieve dry field essential for IOS
• Revilla-León et al. (J Esthet Restor Dent, 2026; PMID: 41236010): PTFE (Teflon) tape and size 02 retraction cord showed best trueness with IOS; all tested retraction methods were within clinically acceptable limits
• El Ashry et al. (J Dent, 2025; PMID: 40414276): Impregnated cord provided greatest displacement but highest gingival height loss at 1 month; cordless pastes preferred for digital impressions to minimize tissue damage

ANSWER 3: GINGIVAL CONSIDERATIONS IN FIXED PARTIAL DENTURES

Introduction

I. Biological Width (Biologic Width)

• Sulcus depth: 0.69 mm
• Junctional epithelium: 0.97 mm
• Connective tissue attachment: 1.07 mm
• Total biologic width = approx. 2.04 mm (epithelial + connective tissue = ~2 mm, not including sulcus)

• Chronic gingival inflammation
• Bone resorption
• Pocket formation
• Gingival recession
• Compromised prosthetic longevity

II. Finish Line (Margin) Position Relative to Gingiva

A. Supragingival Margins

• Located coronal to the free gingival margin
• Advantages:
  • Easiest to prepare, impress, and evaluate clinically
  • Least impact on periodontal health
  • Easy to clean by the patient
  • Accessible for future repair or re-cementation
• Disadvantages:
  • Unaesthetic in anterior regions (visible metal or cement line)
  • More prone to recurrent caries in caries-prone patients
• Indications: Posterior FPD, patients with high caries risk, deep sulcus, biologic width concerns

B. Equigingival Margins

• At the level of the free gingival margin
• Difficult to assess and maintain
• Higher plaque accumulation than supragingival; mild gingival response
• Generally avoided

C. Subgingival Margins

• Located apical to the free gingival margin within the sulcus
• Must not extend into the biologic width
• Depth: maximum 0.5-1 mm below gingival crest (not exceeding half of sulcus depth)
• Advantages:
  • Aesthetic (conceals the metal-ceramic junction)
  • Additional retention
  • Protection from secondary caries
• Disadvantages:
  • Difficult impression making; requires gingival retraction
  • Risk of biological width violation
  • Risk of iatrogenic gingival damage during preparation
  • Difficult for patient to maintain
• Indications: Anterior esthetic restorations, where there is short clinical crown requiring additional retention, where caries extends subgingivally

III. Crown Contour and Its Effect on Gingiva

A. Axial Contour (Gingival Third)

• The gingival one-third of the crown must mimic natural tooth contour
• Over-contoured crowns: Cause gingival inflammation; deflect food and plaque into the sulcus; impede plaque removal; lead to periodontal disease
• Under-contoured crowns: Fail to provide gingival protection; food impaction against gingiva
• The ideal buccal contour at the gingival third should be within 0.5 mm of natural tooth contour (Wheeler's principle)
• Reference: Rosenstiel et al., Contemporary Fixed Prosthodontics, 5th ed., p. 132

B. Embrasure Form

• Adequate embrasure space allows the interdental papilla to fill the cervical embrasure
• Over-contoured proximal surfaces eliminate embrasures, leading to papillary recession, food packing, and interproximal disease
• The contact area should be positioned to allow a healthy papilla in the embrasure

C. Emergence Profile

• The angle at which the crown emerges from the sulcus
• Dictates gingival health in the subgingival zone
• Overly divergent emergence profile (>30° from long axis) → overcontour → gingival inflammation
• Reference: Shillingburg HT, Fundamentals of Fixed Prosthodontics, 4th ed., p. 119

IV. Marginal Fit and Gingival Health

• An open or poor margin is the single most common cause of FPD failure from a gingival standpoint
• An open margin of even 50-100 µm allows bacteria ingress, cement dissolution, and secondary caries
• Clinically acceptable marginal gap: <120 µm (McLean and von Fraunhofer, 1971)
• An open margin acts as a plaque trap, causes gingival inflammation, and may progress to periodontal disease
• Proper impression technique, adequate retraction, and precise die preparation are prerequisites for good marginal fit

V. Periodontal Prerequisites Before FPD Fabrication

1. All periodontal disease must be treated before tooth preparation begins
2. Pocket depth reduced to ≤3 mm; inflammation eliminated
3. Adequate attached gingiva around abutment teeth (minimum 2 mm)
4. Plaque control established and patient compliance confirmed
5. Occlusal evaluation to eliminate traumatic forces on abutments
6. After active treatment, a healing period of 3-6 months is required before final impressions
7. Provisional restorations are used during healing to condition gingival tissue

VI. Provisional Restoration and Gingival Conditioning

• Provisional (temporary) FPD is essential in the gingival management workflow
• A well-fitting provisional:
  • Protects the prepared tooth and periodontium
  • Allows gingival healing after preparation trauma
  • Conditions gingival tissue to the final emergence profile
  • Tests esthetics and occlusion
  • Guides papilla position for pontic zone management
• Poorly fitting provisional causes gingival inflammation that persists at the final impression appointment, yielding inaccurate tissue records

VII. Pontic Design and Gingival Health

• Modified ridge-lap pontic - most commonly used; esthetic; easy to clean; minimal contact with ridge
• Ovate pontic - creates an illusion of a tooth emerging from the ridge; best esthetics; requires soft tissue conditioning
• Sanitary (hygienic) pontic - no contact with ridge; easiest to clean; poor esthetics; used in posterior non-esthetic areas
• Full saddle pontic - maximum ridge contact; hardest to clean; causes chronic gingival inflammation - AVOIDED
• Reference: Rosenstiel et al., Contemporary Fixed Prosthodontics, 5th ed., Ch. 20 (Pontic Design)

VIII. Post-Cementation Gingival Evaluation

• All excess cement must be removed - especially subgingival cement remnants which cause severe gingival inflammation and bone loss
• Marginal integrity checked with probe and explorer
• 1-month and 3-month recall for gingival assessment
• Long-term: Annual recall with periodontal charting around all FPD abutments and pontic sites
• Chauhan et al. (World J Methodol, 2025; PMID: 40900871) state that accurate marginal positioning of the restoration along the prepared finish line is essential for therapeutic, preventive, and aesthetic purposes, and that gingival retraction techniques must be used to decrease marginal discrepancy between restoration and prepared abutment

Summary Table: Gingival Considerations in FPD

REFERENCES

Standard Prosthodontic Textbooks

1. Shillingburg HT, Hobo S, Whitsett LD, Jacobi R, Brackett SE. Fundamentals of Fixed Prosthodontics. 4th ed. Chicago: Quintessence Publishing; 2012. (Chapters 5, 15, 17, 18)
2. Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics. 5th ed. St. Louis: Elsevier/Mosby; 2016. (Chapters 6, 14, 19, 20)
3. Sharma A, Rahul GR, Poduval ST, Shetty K. Textbook of Prosthodontics. 2nd ed. Jaypee Brothers; 2017. (Chapter on Impression Techniques and Gingival Retraction)
4. McCabe JF, Walls AWG. Applied Dental Materials. 9th ed. Oxford: Blackwell Publishing; 2008. (Chapter on Impression Materials, p. 136-160)
5. Gargiulo AW, Wentz FM, Orban B. Dimensions and relations of the dentogingival junction in humans. Journal of Periodontology. 1961;32:261-267.
6. Nevins M, Skurow HM. The intracrevicular restorative margin, the biologic width, and maintenance of the gingival margin. Int J Periodontics Restorative Dent. 1984;4(3):31-49.
7. McLean JW, von Fraunhofer JA. The estimation of cement film thickness by an in vivo technique. Br Dent J. 1971;131:107-111.

Journal Articles

1. Saeed EAM, Alaghbari SS, Lin N. The impact of digitization and conventional techniques on the fit of FPDs: systematic review and meta-analysis. BMC Oral Health. 2023 Dec;23:1005. [PMID: 38049754] DOI: 10.1186/s12903-023-03628-1
2. Porto AM, Nascimento MV, Garcia BA, et al. Marginal adaptation of tooth-supported fixed restorations fabricated using digital scanning versus conventional impression techniques: An overview of systematic reviews. J Prosthet Dent. 2025 Sep. [PMID: 40610310] DOI: 10.1016/j.prosdent.2025.05.044
3. Sarafidou K, Chatziparaskeva M, Chatzikamagiannis D, et al. Evaluation of marginal/internal fit of fixed dental prostheses after digital, conventional, and combination impression techniques: A systematic review. Eur J Oral Sci. 2022 Dec;130(6):e12902. [PMID: 36346664] DOI: 10.1111/eos.12902
4. Andrade Villalobos M, Bennani V, Aarts JM, Ratnayake J. Accuracy of Intra-Oral Scanners for Full Crown Tooth Preparations with Subgingival Margins: A Systematic Review. Eur J Prosthodont Restor Dent. 2025 Feb;33(1):50-60. [PMID: 39887301]
5. Son YT, Son K, Lee KB. Trueness of intraoral scanners according to subgingival depth of abutment for fixed prosthesis. Sci Rep. 2022 Dec;12(1):20598. [PMID: 36456561] DOI: 10.1038/s41598-022-23498-x
6. El Ashry MF, Abdelkader SH, Hammad IA, et al. The efficacy of different gingival displacement methods for definitive digital impressions: A randomized controlled trial. J Dent. 2025 Aug;149:105841. [PMID: 40414276] DOI: 10.1016/j.jdent.2025.105841
7. Rathod A, Jacob SS, MAlqahtani A, et al. Efficacy of Different Gingival Displacement Materials in the Management of Gingival Sulcus Width: A Comparative Study. J Contemp Dent Pract. 2021 Jun;22(6):638-641. [PMID: 34393130]
8. Melilli D, Mauceri R, Albanese A, et al. Gingival displacement using diode laser or retraction cords: A comparative clinical study. Am J Dent. 2018 Jun;31(3):145-150. [PMID: 30028930]
9. Rajambigai MA, Raja SR, Soundar SI, Kandasamy M. Quick, painless, and atraumatic gingival retraction: An overview of advanced materials. J Pharm Bioallied Sci. 2016 Oct;8(Suppl 1):S5-S8. [PMID: 27829736] DOI: 10.4103/0975-7406.191968
10. Xu X, Tian S, Zhang M, et al. Fully digital pneumatic gingival-retraction scanning technique: from methodology development to clinical validation. J Dent. 2025 Dec;152:106192. [PMID: 41130557] DOI: 10.1016/j.jdent.2025.106192
11. Revilla-León M, Pérez-García E, Guinot-Barona C, et al. Influence of Color and Diameter of Retraction Cords and Teflon Tape on the Accuracy of Tooth Preparations Digitized by Using Intraoral Scanners. J Esthet Restor Dent. 2026 Mar. [PMID: 41236010] DOI: 10.1111/jerd.70054
12. Chauhan R, Chauhan S, Padiyar N, et al. Present status and future directions: Soft tissue management in prosthodontics. World J Methodol. 2025 Dec;15(4):104497. [PMID: 40900871] DOI: 10.5662/wjm.v15.i4.104497
13. Derksen W, Tahmaseb A, Wismeijer D. Randomized Clinical Trial comparing clinical fit of CAD/CAM monolithic zirconia FDPs on ti-base abutments based on digital or conventional impression techniques - 1-year follow-up. Int J Prosthodont. 2021;34(6):755-762. [PMID: 33662051]

Note for exam writing: For a 10-mark answer, allocate approximately: Introduction (1 mark) + Classification/types (3 marks) + Detailed explanation with clinical points (4 marks) + Recent advances/evidence (1 mark) + Conclusion (1 mark). The above content can be selectively condensed based on the specific question focus. All three topics share overlapping concepts - margin position, retraction technique, and impression accuracy are interconnected, and examiners appreciate when candidates draw these connections explicitly.

CONNECTORS IN FIXED PARTIAL DENTURES (FPD)

CONTENT OUTLINE

1. Definition and Introduction
2. Requirements of an Ideal Connector
3. Classification
4. Rigid Connectors
   • A. Cast Connectors
   • B. Soldered Connectors (Pre-soldering and Post-soldering)
   • C. Welded / Laser Welded Connectors
5. Non-Rigid Connectors (Stress Breakers)
   • A. Key and Keyway (Tenon-Mortise / Dovetail)
   • B. Loop Connectors
   • C. Split Pontic
   • D. Cross Pin and Wing Connectors
6. Connector Design Considerations
   • A. Size
   • B. Shape
   • C. Position
7. Pier Abutment and Non-Rigid Connectors
8. Recent Evidence
9. Conclusion
10. References

ANSWER

1. Definition and Introduction

"The connector is that part of a fixed partial denture or splint that joins the individual components (retainers and pontics) together."

• Rosensteil SF, Land MF, Fujimoto J (Contemporary Fixed Prosthodontics, 5th ed.)

"That part of a fixed partial denture which connects the pontic and retainer and can be rigid or non-rigid."

• Shillingburg HT et al. (Fundamentals of Fixed Prosthodontics, 4th ed.)

"The portion of a fixed partial denture that unites the retainer(s) and pontic(s)."

• Glossary of Prosthodontic Terms (GPT-9), J Prosthet Dent, 2017

2. Requirements of an Ideal Connector

1. Must be sufficiently strong to resist all masticatory forces without fracture or deformation
2. Should have no likelihood of wearing during the lifetime of the prosthesis
3. Should be placed as lingually and incisally as possible to allow for self-cleansing and access for oral hygiene
4. Should preserve the interproximal embrasure and occupy the normal anatomic interproximal contact area
5. Should occupy a connector space of approximately 0.25 mm width (soldering gap)
6. Depth of the connector should always be sufficient to provide adequate cross-sectional area for strength
7. Should not impinge on gingival tissue - must remain at least 1 mm above the crest of the interproximal papilla
8. Should maintain aesthetics - placed slightly lingually in anterior esthetic zones

3. Classification of Connectors

CONNECTORS IN FPD
│
├── A. RIGID CONNECTORS
│     ├── 1. Cast connectors
│     ├── 2. Soldered connectors
│     │         ├── Pre-ceramic (pre-soldering)
│     │         └── Post-ceramic (post-soldering)
│     └── 3. Welded connectors (laser / electrical)
│
└── B. NON-RIGID CONNECTORS (Stress Breakers / Precision Attachments)
          ├── 1. Key and Keyway (Tenon-Mortise / Dovetail)
          ├── 2. Loop connectors
          ├── 3. Split pontic connectors
          └── 4. Cross pin and wing connectors

4. RIGID CONNECTORS

1. Standard fixed-fixed FPDs with well-aligned abutments
2. When the entire load on the pontic is to be transferred directly to the abutments
3. Short-span FPDs (3 or 4 units)
4. All implant-supported FPDs (only rigid connectors are used with implant abutments)

1. Cases where an existing diastema is to be maintained
2. Tilted or divergent abutments where path of insertion is compromised
3. Long-span FPDs with high occlusal stress (risk of connector fracture)
4. Pier abutment situations (the fulcrum effect demands non-rigid connector)

A. Cast Connectors

• The connector is designed as an integral part of the wax pattern; the entire framework is cast as one piece
• Advantage: Convenient fabrication, fewer laboratory steps, eliminates solder joint which is potentially the weakest link
• Disadvantage: Distortion is more likely when a multi-unit wax pattern is removed from the die system, which may adversely affect the fit of individual retainers; difficult to adjust fit of each unit separately
• Best suited for short-span FPDs where casting distortion is minimal

B. Soldered Connectors

1. Wax patterns are sectioned at interproximal areas using a thin ribbon saw
2. The cut surfaces are made flat and parallel at a controlled distance of 0.13 mm
3. Individual castings are invested together using autopolymerizing acrylic resin, ZOE paste, and soldering investment to maintain precise spatial relationship
4. Flux is applied; soldering is carried out with torch or oven
5. Excess solder is finished and polished

• Better fit of individual retainers (each cast and fitted separately before joining)
• Allows individual try-in of each component for margin accuracy
• Postsoldering allows more natural-looking proximal contours
• Essential for long-span FPDs and metal-ceramic prostheses

• Pre-soldering (Pre-ceramic soldering): Performed before ceramic application; uses high-fusing solder; porcelain is applied after the units are joined; simpler but porcelain contours need to be added across the joint
• Post-soldering (Post-ceramic soldering): Performed after individual ceramic units are fully fired and completed; uses lower-fusing solder; the proximal areas are shaped before soldering so contours are more natural; more technique-sensitive but produces a better esthetic result

C. Welded Connectors

• Uses a focused laser beam concentrated on a minute spot to create fusion of metals through intense thermal energy
• Advantages: Relative ease and time-saving; can be performed directly on the cast model; less distortion than conventional soldering; higher strength; reduced corrosion; no flux required
• Disadvantages: High equipment cost; technique-sensitive; produces hazardous light/radiation requiring protective screens
• Growing use in CAD/CAM and digital workflows for joining zirconia frameworks and metal-ceramic components

5. NON-RIGID CONNECTORS (Stress Breakers / Precision Attachments)

1. Pier abutment situations (intermediate abutment in a 5-unit FPD) - most important indication
2. Periodontally weakened abutments
3. Long-span FPDs with excessive occlusal forces
4. Malaligned or tilted abutments where a single path of insertion is not achievable with both retainers as one unit
5. Cases requiring individual replacement of one segment without disturbing the other

A. Key and Keyway Connector (Tenon-Mortise / Dovetail)

• The most widely used non-rigid connector
• Consists of a mortise (keyway) prepared within the contour of the retainer and a tenon (key) attached to the pontic
• The key fits precisely into the keyway; permits vertical displacement but prevents rotation
• The keyway is always placed in the distal abutment retainer; the key is on the mesial surface of the adjacent pontic - this positioning prevents tipping of the pier abutment

• Pre-fabricated plastic patterns (for both mortise and tenon) are available
• Alternatively, a specialized mandrel is embedded into the wax pattern for the retainer; the casting provides the mortise, and the tenon is fabricated separately
• The completed key is attached to the pontic

1. Relieves stress on abutments and pier abutment - acts as a stress breaker
2. Acts as a splint for periodontally weakened teeth
3. Allows easy repair - only the defective segment needs to be removed and replaced
4. Accommodates malaligned abutments

1. Extensive tooth preparation required (for adequate depth of keyway within crown contour)
2. Time-consuming and costly
3. Not suitable for short abutments (inadequate space for keyway)
4. Requires precise laboratory technique

B. Loop Connectors

• Used when there is a diastema between abutment teeth that must be maintained (e.g., central diastema in anterior region)
• A metal loop extends from the retainer to the pontic, bridging the diastema space
• The loop is placed on the lingual/palatal side; the diastema is preserved facially
• Advantages: Maintains existing diastema; esthetic
• Disadvantages: Weaker than a conventional connector; longer lever arm increases stress; may accumulate plaque; requires adequate vertical height for loop
• Indication: Anterior FPD when the patient insists on preserving a natural diastema

C. Split Pontic Connector

• A specialized form used when there is a compromise in alignment or path of insertion
• The pontic is divided into two segments, connected by a precision interlocking mechanism
• Allows each segment to be inserted from a different path of insertion
• Used when the pier abutment and terminal abutment have significantly different paths of insertion
• Advantages: Accommodates path of insertion discrepancies; reduces stress distribution
• Disadvantages: Complex fabrication; multiple laboratory steps; technique-sensitive

D. Cross Pin and Wing Connectors

• Used specifically for tilted posterior abutments, especially tilted molars
• The cross pin passes through the pontic and engages wings on the retainer, creating a mechanical lock that allows limited rotational movement
• Advantages:
  1. No need to remove the entire assembly if repair or replacement is needed
  2. Good stress distribution
  3. Reduces the magnitude of forces on abutments
• Disadvantages:
  1. Time-consuming fabrication
  2. Additional laboratory steps required for pin fabrication
  3. Highly technique-sensitive

6. CONNECTOR DESIGN CONSIDERATIONS

A. Connector Size

• All-ceramic (zirconia) connectors require a larger cross-sectional area to compensate for the material's brittleness (low flexural toughness compared to metal)
• Undersized connectors are the most common cause of FPD connector fracture, especially in all-ceramic restorations

B. Connector Shape

• The cross-sectional shape determines stress distribution
• An elliptical cross-section with the major axis aligned with the direction of applied force provides the greatest strength
• The connector outline should have rounded, smooth junctions at the gingival aspect to prevent stress concentration that can lead to fatigue fracture
• Avoid sharp angles - use concave inner contours ("U" shape at gingival) for stress relief

C. Connector Position

• Biological perspective: Connectors must not impinge on gingival tissue; must be at least 1 mm above the crest of the interproximal papilla; they should occupy the normal anatomic interproximal contact areas
• Esthetic perspective: In anterior esthetic zones, connectors are placed slightly lingually so the metal or opaque is not visible from the labial aspect
• Hygiene perspective: Adequate embrasure space must be maintained - gingival embrasure allows passage of interdental brushes or dental floss; inadequate embrasure space leads to plaque accumulation, gingival inflammation, and periodontal disease

7. PIER ABUTMENT AND NON-RIGID CONNECTORS - A Special Situation

• Intrusive forces on terminal abutments
• Extrusive torqueing on the pier abutment
• Cement lute failure at one or more retainers
• Potential abutment tooth fracture or periodontal damage

• Sonar PR et al. (Cureus, 2024; PMID: 38318549) reported that use of non-rigid connector as a stress breaker in a pier abutment scenario resulted in less stress on the prosthetic assembly and abutment teeth, with successful rehabilitation
• A 3D FEA study (Modi et al., PMC4439856) of a 5-unit FPD with pier abutment showed that non-rigid connectors reduced von Mises stresses at the connector region and cervical margin (rigid: 86.19 MPa vs. non-rigid: 76.55 MPa), though stresses at the alveolar bone level were comparatively higher with non-rigid design
• Naguib GH et al. (J Prosthodont, 2023; PMID: 37184094): In tooth-implant FDPs, rigid connectors using an implant of 5.7 × 10 mm showed 26% lower stresses compared to the non-rigid design; for tooth-implant prostheses, rigid connectors are now preferred when implant dimensions are appropriate

8. ALL-CERAMIC CONNECTOR CONSIDERATIONS

• Zirconia has high compressive strength but is susceptible to connector fracture due to tensile forces
• Larger connector areas (minimum 12-20 mm²) are mandatory
• The connector should have a concave gingival profile to distribute tensile stresses away from the outer surface
• Digital design (CAD) allows precise connector sizing that was difficult with analog wax patterns
• Sarafidou et al. (Eur J Oral Sci, 2022; PMID: 36346664) noted that all-ceramic FPDs in a fully digital workflow showed clinically acceptable marginal fit, with proper connector size being essential for structural integrity

9. COMPARISON TABLE: RIGID vs. NON-RIGID CONNECTORS

10. Conclusion

REFERENCES

Standard Prosthodontic Textbooks

1. Shillingburg HT, Hobo S, Whitsett LD, Jacobi R, Brackett SE. Fundamentals of Fixed Prosthodontics. 4th ed. Chicago: Quintessence Publishing; 2012. Chapter 20: Connectors, p. 447-465.
2. Rosensteil SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics. 5th ed. St. Louis: Elsevier/Mosby; 2016. Chapter 22: Fixed Partial Denture Design, p. 606-630.
3. Sharma A, Rahul GR, Poduval ST, Shetty K. Textbook of Prosthodontics. 2nd ed. New Delhi: Jaypee Brothers Medical Publishers; 2017. Chapter on Connectors in FPD.
4. Mallat E, Koth DL. Practical Removable and Fixed Partial Dentures. CV Mosby; 1981. (Classic reference for connector design principles)
5. Glossary of Prosthodontic Terms. J Prosthet Dent. 2017;117(5S):e1-e105. (GPT-9 definition of connectors)

Journal Articles

1. Naguib GH, Hashem ABH, Abougazia A, et al. Effect of non-rigid connector on the stress distribution of tooth-implant supported fixed prostheses using different implant length and diameter: A comparative 3D finite element study. J Prosthodont. 2023 Jul;32(6):525-534. [PMID: 37184094] DOI: 10.1111/jopr.13702
2. Sonar PR, Panchbhai AS, Pathak A, et al. Rehabilitating Long Edentulous Span by Using Pier Abutment as a Non-rigid Connector: A Case Report. Cureus. 2024 Jan;16(1):e51652. [PMID: 38318549] DOI: 10.7759/cureus.51652
3. Modi R, Kohli S, Rajeshwari K, Bhatia S. A three-dimension finite element analysis to evaluate the stress distribution in tooth supported 5-unit intermediate abutment prosthesis with rigid and nonrigid connector. J Int Oral Health. 2015;7(5):96-101. [PMC4439856]
4. Rani P, Malhotra P. Breaking the stress with a non-rigid connector. Niger Postgrad Med J. 2020 Oct-Dec;27(4):333-336. [PMID: 33154295]
5. Banerjee S, Khongshei A, Gupta T, Banerjee A. Non-rigid connector: the wand to allay the stresses on abutment. Contemp Clin Dent. 2011;2(4):351-354. DOI: 10.4103/0976-237X.91802
6. Sarafidou K, Chatziparaskeva M, Chatzikamagiannis D, et al. Evaluation of marginal/internal fit of fixed dental prostheses after digital, conventional, and combination impression techniques: A systematic review. Eur J Oral Sci. 2022 Dec;130(6):e12902. [PMID: 36346664] DOI: 10.1111/eos.12902
7. Sutherland JK, Holland GA, Sluder TB, Bayne SC. A photoelastic analysis of the stress distribution in bone supporting fixed partial dentures of rigid and nonrigid design. J Prosthet Dent. 1980;44:616-623. (Classic biomechanics reference)
8. Standlee JP, Caputo AA. Load transfer by fixed partial dentures with three abutments. Quintessence Int. 1988;19:403-410. (Classic pier abutment study)

Exam tip (10-mark format): Present the content outline at the very start, followed by definitions (1 mark), classification with diagram/table (2 marks), rigid connectors with subtypes (3 marks), non-rigid connectors with subtypes (3 marks), and design considerations including pier abutment management (1 mark). Conclude with a synthesizing statement. Always support with atleast 2-3 specific textbook page references and 2 journal citations.

Quick Navigation Guide

• Content outline at the start
• Full GPT-9 / textbook definitions
• Classification with diagrams/tables
• Detailed clinical content
• Comparison tables
• Recent advances with dated evidence and PMIDs
• Conclusion
• References (textbooks + journals) at the end