Evaluation of Enamel Wear caused By Various Ceramic Materials and Gold

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Evaluation of Enamel Wear caused By Various
Ceramic Materials and Gold

• Asmaa Elmaria DDS, MS
• Gary R. Goldstein, DDS
• T.V. Vijayaraghavan, PhD
• Raquel Z. Legeros, Ph.D
• NYU Kriser Dental Center

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Enamel Wear

• Occlusal contact - wear
• Enamel against enamel 25-40 µm per/year
• Enamel against Restorative materials
• Ceramic gt Composite gt Gold
• Restorative material wear
• Gold gt composites gt Glazed ceramics
• Lambrecht P, Braem M, Vuylsteke- wauters M,
  Vanherle G. Quantitative in vivo wear of human
  enamel. J Dent. Res. 1989 681752-54.

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Enamel Wear -Factors

• Smoother surface ? wears less
• Rougher surface ? greater wear
• Harder surface ? greater wear
• Bite and Chewing forces
• Para-functional habits
• pH, enamel character morphology

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Prior studies

• Jacobi Shillinburg, Monasky and Taylor, Hudson
  et al.
• abrasive nature of porcelain
• Krejci et al.
• rate of enamel wear function surface finish,
  hardness
• Krejci et al.
• Polishing of pressed glass ceramic led to less
  wear than glazing.
• Klausner et al.
• Ra values same for polished/glazed
• Raimondo et al.
• auto-glazed better vs. polished

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Clinical factors

• Occlusal adjustments a norm!
• Requires re-glazing
• Time, cost Inconvenience
• Alternative?
• Polishing

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Polishing as an alternative

• Avoid repeated firing
• Avoid devitrification ? loss of translucency
• Less time consuming
• Convenient

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Objective

• The purpose of this study was to evaluate enamel
  wear caused by a gold alloy and three ceramic
  substrates in the glazed and polished conditions.

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Null hypotheses to be tested

• Enamel wear caused by a glazed substrate is
  similar to that caused by a glazed surface that
  has been adjusted and polished.
• Enamel wear caused by glazed or polished surface
  (after adjustment) is not dependent on the type
  of ceramic.
• Enamel wear caused by a gold substrate is similar
  to any of the ceramic substrates in both surface
  conditions.

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Materials and Methods

• Natural Enamel cusps, Ceramics, Gold
• 10 samples/condition/material
• Linear wear excursions (10,000 cycles)
• Track length 6 mm
• Surface roughness (Ra)- Before and after

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Restorative Materials
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Materials and Methods
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Materials and Methods

• Measurement of enamel wear
• From trace of enamel cusp profile
• Qualitative wear (SEM)

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Materials and Methods
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Results

• t-Test, pooled variance, 2 tail plt0.05
• One-way ANOVA,followed by Scheffe test p0.05
• SE Micrographs

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Multiple comparisonsEnamel height loss


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Surface roughness, Ra (mm) Before and after wear
(N10 per group), Student's t-Test, significant
differences based on p 0.05
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Gold Alloy
Left low magnification (35X),the track created
by the enamel cusp at 10,000 cycles. Right
higher magnification(350X) showing polishing
lines and smoother track region. Ra 0.09- 0.29
µm-before after wear)
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Finesse- polished condition
(35X). The track region has been outlined
(continuous line) and reveals continuous grooves.
The background reveals a pitted appearance with
dark isolated regions indicated by arrows
(background), suggesting removal of some
micro-structural constituent . (Ra 0.37-0.44 µm
- -before after wear)
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IPS-Empress- polished condition
The track region is visible and reveals a
smoother surface than the surrounding background.
Polishing marks can be seen in the background
region. Debris is visible as bright white
discontinuous regions. (35 X) (Ra 0.15-0.28 µm
-before after wear)
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IPS-Empress- glazed condition
Left low magnification (35X) Right Higher
magnification (500X) (Ra 0.46-0.64 µm - -before
after wear)
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Discussion

• Polishing produced a smoother surface only in two
  materials
• Grit size- polishing material
• Grain or crystal size, phases hardness
  substrate, glazing Pressure and Temperature,
• Leucite content? increased hardness
• IPS-Empress and Finesse
• Smoothness and roughness
• (polishing and wear)
• Kingery WD Introduction to Ceramics, John Wiley
  and Sons, Inc., 1960, 597-599.

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Discussion

• Adjustment Polishing
• Gross minor wear
• Removal of glaze
• Traditional porcelain would require re-glazing
  unglazed porc.- significant ? modulus of rupture
• Newer generation porcelain greater than normal
  adjustment may be possible- then polishing
• Density, processing mode, homogeneity, leucite
  crystalline additions

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Mean Roughness Value

• Roughness and polishing
• Ra value in this study was below 1µm
• Roughness and wear
• Smooth - higher wear !
• Rough lower wear !

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Conclusion

• Ranking of enamel cusp height loss
• Gold lt PFIN ltPALC ltGALC ltPEMP ltGFIN ltGEMP
• Ranking of mean Ra values
• Gold lt PEMPltGALCltPALCltPFINltGEMPltGFIN

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Conclusions

• Gold caused significantly less enamel wear than
  ceramic substrates
• Glazed surfaces exhibited significantly more
  enamel wear than polished surfaces
• Finesse caused the least enamel wear among all
  the ceramic materials, and was not significantly
  different than Gold
• Empress caused the greatest wear

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Thank you