Dental Ed Ceramic Onlays - Contemporary Guidelines for Clinical Success 16-06-2026

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#FIXEDPROS

Presented by A/Prof. Taiseer A Sulaiman

Heat

• normal pulp at about 34-35°
• increase in 7 degrees to 42 is enough to cause irreversible pulpitis
• in vitro study JPD Nilsson 2023
  • 15% necrosis or irreversible pulpitis from an increase in 5.5 degrees
• Int ENdod G S P CHEUNG 2005
  • 81.2% survival rate after 15 years of PFM with preop vital teeth
  • with a main mechanism of failure being endodontic reason (loss of vitality)
• Int J Prosthodont Walton 2023
  • 85% 26 year survival rate
  • biologic fators accounted for majority of failures

**Gold

• 95% survival rate, most researched material

Ceramic

• sharp line angles create oblique tensile stress, which is unfavourable for ceramics
• rounded angles create compressive stress, which is very favourable for ceramics
• Without resistance features with risk of marginal wear, 7/10 debonded,w hereas with resistance features only 1/10 debonded
• no debonded was observed after 5 years testing with no cusp cap in cusps that were of 2mm height

Glass phase ceramics (old)

• feldspathic porcelain
  • mode of failure is fracture or debonding
  • low flexural strenght is its main weakness

Lithium disilicate

• emax
  • flex and fracture similar to enamel/dentine, elastic modulus quite similar
  • better in strength than enamel
  • pressed and CAD/CAM are similar in outcomes using contemporary machines
• method of preparation
  • 5% HF acid for 20s
  • ultrasonic bathing to clean surface
  • silanization
  • apply adhesive
  • resin cement
• JPD Sulaiman 2019
  • emax is very good for partial coverage, with a low fracture rate of 0.99% for monolithic onlays

Zirconia

• tetragonal bonds (strength)
• cubic bonds (transparency/aesthetics)
• 3Y ceramic 85:15
• 5Y ceramic 50:50
• 4Y ceramic 75:25
• review fracture strength using 0.5 and 1.2mm thickness, 3Y displays the best strength overall with an ideal thickness of about 1.2mm to be similar to enamel, therefore 3Y zirconia is best indicated using contemporary research
• zirconia may go through a phase of transofrmation toughening which can help to reduce its fracture rates
• recommended occ reduction
  • 3Y 1mm
  • 4Y 1.2mm
  • 5Y 1.5mm
• zirconia bonding protocol
  • air abrasion
  • clean and dry
  • ceramic primer (silanization) 3 mins
  • zirconia cleaner
  • adhesive dual cure cement

Bonding

• in modern age, we want to rely on bonding itself, therefore we use an adhesive rather than a self adhesive, dual cure is the best for this
• for adequate bonding to occur, we need about 10J /cm2
  • when testing light cure machines, they are testing in optimum conditions and land at 20s
  • however when you look at going through materials, there isnt enough energy transferred, also depends on what one you use
• contemporary recommendation
  • 40-60 seconds per surface with air flow to promote cooling and short breaks between each surface (few seconds), more intense curing units may cause more heat therefore the unit itself is not so important