L8 Resin Bonded Bridges

Resin-Bonded Bridges and Implant Considerations in Young Patients

Front Matter¹²³⁴

We are learning on Noongar land

The University of Western Australia

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Developmental Changes and Growth⁶

[F] [020Y]

[mm]: orthogonal / 30.0

• 20
• 30
• 40
• 50

Maxillary Growth and Tooth Movement⁷⁸⁹

1. Maxilla grows down and forward

2. Resorption of labial bone over maxillary anterior teeth

3. Teeth extrude and upright

Adult Growth Changes¹⁰¹¹

3. Teeth extrude and upright

Fig. 4-25 — Growth changes in adults

• A: Changes in a male from age 37 (black) to age 77 (red). Note that both the maxilla and mandible grew forward, and the nose grew considerably.
• B: Growth changes in a woman between age 34 (black) and 83 (red). Note that both jaws grew forward and somewhat downward, and that the nasal structure enlarged.

From Behrents RG: A treatise on the continuum of growth in the aging craniofacial skeleton. Ann Arbor, 1984. University

Risks of Implants in the Growing Anterior Maxilla¹²¹³

• Infraocclusion → shorter incisally + long apically
• Blue colouring of labial gingiva
• Collapse of labial soft tissue coverage
• Recession exposing abutment / implant
• Lack of papilla especially D
• Protrusion relative to natural teeth

In the anterior maxilla of a young adult, risk of unpredictable + unaesthetic side effects in the long term due to the ankylotic unit.

Thilander, Eur J Orthod 2001;23:715-

Jemt, CID+RR 2005;7:200-

Timing Guidelines for Implants in Young Patients¹⁴

Koch et al 1996 — Consensus conference on oral implants in young patients

• Mandible: 5–6 years old
• Maxilla:
  • A fixed chronological age cannot be recommended
  • Use prostheses that won’t affect growth
  • When growth is complete
  • Can’t predict when, but can tell when:
    • Longitudinal body height measurement
    • Hand-wrist radiograph
    • Serial (12-month) cephalometric radiographs

Treatment Planning and RBB Overview

Least Invasive Treatment Philosophy¹⁵¹⁶¹⁷

Treatment of choice is the least invasive option that satisfies the aesthetic and functional objectives

Think lifelong

Radiographic Assessment of the Maxilla¹⁸

CT Maxilla — Series: 07/06/2023 8:35:16 AM; Series: CT #602; Image: 1/3. Panel A. R, W 3600, C 680.

Data acquired on 7/06/2023 8:31:55 AM at Envision Medical Imaging.

• Input Images — Number / Slice Thickness [mm]: 160 / 0.40
• Reconstruction Increment [mm] / Kernel: n.a. / Ur69u
• Panorama — Distance / Slice Thickness [mm]: 2.0 / 3.00
• Paraxial — Orientation / Length / Distance / Slice thickness [mm]: orthogonal / 30.0 / 2.0 / 1.00

RBB Versus Implant Comparison¹⁹²⁰

	RBB	IMPLANT
Prognosis
Aesthetics
Procedures
Treatment time
Cost
Growth
What next?

The three levels of surgical wisdom:

1. Good surgeon — how to operate
2. Better surgeon — when to operate
3. Best surgeon — when not to operate

Options for Replacing Teeth²¹

3 ways to replace teeth:

• No treatment
• Space closure
• Autotransplant
• Removable
• Implant
• Bridgework — tooth supported (RBB)

Indications and Limitations of RBBs

RBB²²

• Treatment of choice in some situations
  • lower incisors
  • maxillary laterals
  • occasionally other teeth with risk
• Posterior RBBs
  • low success
  • aesthetic problem in mandible

RBB Materials and Bonding

Assessment of Tooth Substrate²³

Need enamel to bond and seal.

Alloy Choice and Properties

Alloy Choice: Non-Precious²⁴

What this means

• Ni-Cr
• CrCo
• NP2 non-Be
• Rexillium = Be-containing Ni-Cr

Properties

• Rigid → good for RBB
• Less accurate to cast; polishing challenging
• Grey oxide layer = bonding
• Possible Ni sensitivity

Surface Treatment of the Metal Framework

Root Canals²⁵

• Air abrade (sandblast) 50 µm Al2O3 + ultrasonic
  • Roughens
  • Increases surface area
  • Cleans
  • Improves wetting

Root Filling

• Historically → biomarra
• Electrolytic etch → micromechanical
• Silanization/siloating via Silcoater or Rocatec → chemical bond to alloy
  • 0.5 micron layer of SiOx-C (hybrid silica) added (this is already in porcelain)
  • Then silane coupling agent
  • Then unfilled resin

Resin Cement Selection^26272829

Resin Cement: Panavia³⁰

• Silanated quartz
• Methacrylate resins (not BISGMA)
• MDP
  • Phosphate ester / adhesive functional monomer
  • Chemical bond via metal oxide

Opaque Panavia and Try-In Technique³¹³²

Always Opaque Panavia³³

• Avoid grey show-through
• Can try in with opaque paste (no catalyst)

Metal-Resin-Enamel Bond Complex

Resultant Metal-Resin-Enamel Complex³⁴

• Overall strong bond = 40 MPa

Components

• Tooth–tooth: cohesive

• Tooth–resin: adhesive, weak

• Resin–resin: cohesive, weakest — failure is cohesive

• Resin–metal: adhesive, stronger — high bond (2–3x tooth–resin)

• Metal–metal: cohesive

• No need to improve on resin–metal interface

• Need to improve tensile strength of cement

This is the reason for tooth preparation — want R+R to decrease tensile forces on resin.

Tooth Preparation and Retraction³⁵³⁶³⁷

Preparation³⁸

• Precise mesial and distal grooves

  • Mechanical retention
  • Decrease tensile forces on resin cement

• Retraction

  • Often electrosurge
  • 2 cords

• Overall strong bond = 40 MPa

Components

• Tooth–tooth: cohesive

• Tooth–resin: adhesive, weak

• Resin–resin: cohesive, weakest — failure is cohesive

• Resin–metal: adhesive, stronger — high bond (2–3x tooth–resin)

• Metal–metal: cohesive

• No need to improve on resin–metal interface

• Need to improve tensile strength of cement

This is the reason for tooth preparation — want R+R to decrease tensile forces on resin.

• Precise mesial and distal grooves
  • Mechanical retention
  • Decrease tensile forces on resin cement
• Retraction
  • Often electrosurge
  • 2 cords

Margin Configurations and Clinical Images

Margin Designs³⁹

Margin configurations

(a) (b) (c) (d) (e)

Clinical Case Images^40414243

Close-up intraoral images showing two adjacent maxillary posterior teeth with endodontically treated roots and bonded ceramic or composite restorations over the coronal aspects. The restorations cover the incisal edges and include visible composite buildups at the incisal edges, likely for structural reinforcement. The surrounding gingival tissue appears healthy. One image shows a front view of the teeth while the other shows a side or angled perspective.

Dental crown fitting on molar and premolar teeth

Dental implant fixture: Left micro-CT image showing internal threaded implants; Right clinical view of dental alveolus with bone defect location.

Bur Selection and Provisional Restorations

Bur⁴⁴

• Thin tapered fissure TC
• Sharp = NEW

(Halas p 82 Section 7 Fig. H23L)

• TH 23L 314 010

Provisional^{45464748495051}

• Cavit grooves
• RPD / Suspension bridge

Cases:

• Maxillary laterals
  • Mandibular incisors
    • Occasionally other teeth (with risk)
• Diastemas?
• Enamel
• Occlusion on pontic to be avoided
• Space for retainer
• Cantilever
  • may reduce stress on cement
  • certainly avoids caries when one side debonds
• Prepare tooth – low TS of cement
• Sand-blasted non-precious alloy
• Opaque Panavia

Ceramic Materials and Crown Techniques

Crown Impression Techniques Overview⁵²

• Metal-ceramic (PFM)
• Etchable ceramic
• Non-etchable ceramic

Glass Ceramics and Etching⁵³

• Silica based
• HF selectively dissolves glass
• Silane
• etc

Lithium Disilicate Ceramic

Pre-etch^{54555657585960}

[img]Lithium disilicate ceramic surface before etching[/img]

Lithium Disilicate Indications⁶¹⁶²⁶³

• Veneers (≥ 0.3 mm)
• Inlays and onlays
• Occlusal veneers, partial crowns
• Minimally invasive crowns (≥ 1 mm)
• Implant superstructures
• Hybrid abutment solutions
• Three-unit bridges up to the second premolar as the terminal abutment

https://www.ivoclar.com/en_us/products/metal-free-ceramics/ips-e.max-lithium-disilicate

Lithium Disilicate Limitations for RBBs⁶⁴⁶⁵

• Not indicated for RBB due to connector fracture risk
• But if connector size…bulky
  • 3 mm vertical
  • 2 mm horizontal

Zirconia Bonding and Clinical Outcomes

Bonding to Zirconium Oxide⁶⁶⁶⁷

• Metal-ceramic (PFM)
• Etchable ceramic
• Non-etchable ceramic

Zirconium oxide

• Can’t etch non-silica based ceramic
• No glass! (HF dissolves glass)
• Try:
  • Silica coat
  • “Hot bond” etchable glass
  • APC

APC Concept for Zirconia^68697071

Zirconium oxide (Y-TZP)

APC Concept⁷²

Blatz et al., Compendium 37 (2016):9:611-

• A = Air-particle abrasion aluminum oxide (50 µm, 1–2 bar)

• P = Zirconia primer (MDP)

• C = Composite resin

• Adhesive phosphate monomer = MDP can be in the primer or adhesive

• Eg. Panavia 21 (MDP)

• Rocatec Plus 50 micron particles (silica-coated alumina) under pressure of 2 bar

• Use of phosphate-containing primer, ideally Clearfil Ceramic Primer (higher MDP content compared to the rest of the products); if not, Monobond Plus

• Panavia

Long-Term Outcomes of Zirconia Cantilever RBBs

Zirconium oxide (Y-TZP)

Kern et al., J of Dent 65 (2017):51-

• Ten-year outcome of zirconia ceramic cantilever RBBs
• 108 bridges in 87 pts
• Mean observation 92 mo = 7.6 yrs
• 8 bridges lost to follow up
• 6 debonded (but were recemented)
• No connector failures
• Conclude “10 year survival rate of 98.2%“

Key Technical Points⁷³

• Attention to:
  • 30 mm² SA, sound enamel
  • 0.7 mm retainer (occlusion needs to allow)
  • 3 mm high × 2 mm wide minimum connector
  • Air abraded with alumina → cleaned with alcohol
  • Panavia 21, etc.

Cantilever Design and Occlusal Assessment⁷⁴

Cantilevered⁷⁵

Mesial cantilever → tip out of occlusion

• Assessment of occlusion
  • Contact in MIP but no excursive contacts
  • Retainer space to be gained (cut teeth) or is available
  • Engineer to situation:
    • Bruxers also need tooth replacements!
    • Class II div II also need tooth replacements!
    • Research often challenges dogma

Historical Outcomes of Two-Abutment RBBs^76777879

• Berekally 1993, ADJ, Adelaide, Australia
  • 2 abutments +/- prep
  • Extremely high failure rates implies technique sensitive — NOT that they do not work
  • Survival ~60% at 5 years, many debonded VERY early

27 yo, RBB placed at 29 yo

• Probster 1997, IJP, Mainz, Germany

• 2 abutments +/- prep

• Survival: 76% at 5 years, 60% at 10 years

• Gerry Barrack 1993, IJP, NYU, USA

• Authors resin-bonded cast restorations from private practice

• 11 year prospective

• 127 restorations, 455 units (ranging 1–10 units)

• Success = no debond

• 92.9% over 11 years, but 100% in the latter 9 years (since 1983)

No failures since 1983 when adopted:

• Grooves + rests + incorporating existing restorations
• Panavia
• Non-precious alloy sandblasted

Barrack, Bretz, IJP 1993;6(5):428-

Footnotes

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