الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
The aim of the present study was to evaluate: The wear characteristics of lithium-silicate crowns
in comparison to monolithic zirconia crowns after one year of function. The quality of the overall
restorations was also evaluated at baseline and after one year according to the modified United States
Public Health Service (USPHS) criteria, including the following outcomes: Color match, sensitivity of
the natural tooth opposing to crown, marginal adaptation, as well as, anatomic form, integrity of the
restoration, secondary caries and retention. The gingival and periodontal response to the tested allceramic crowns was also assessed at baseline and 1 year follow up period.
Methodology A total of twenty-two patients (age range 21-45 Y) requiring full-coverage restorations for
endodontically treated 1st molars opposed by natural antagonistic teeth were selected for the present
study. The patients were divided into two groups according to the crown materials (N=11 patients per
each group): group I (Comparator group) fabricated from monolithic zirconia crowns (STML MZ) and
group II (Intervention group) fabricated from lithium silicate crowns (Obsidian). After cementation of
the crowns and after one year of follow up, vinyl polysiloxane impressions of the crowns and their
antagonist teeth were taken, and replica stone casts were fabricated. For surface roughness quantification
analysis of replica casts, the optical profilometer was used. The replicas (baseline and after one year)
were scanned and digitally superimposed in order to evaluate the wear of the crowns and their
antagonist’s enamel. The quality of the overall restorations was evaluated according to (USPHS) criteria
at the same timeframes as gingival and periodontal health were also evaluated. All data was collected,
checked, revised, tabulated and entered into the computer. Statistical analysis was performed by using test
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Comparison between 2 groups (qualitative data) was performed by using the Chi square test.
Results: Statistically insignificant difference in the surface roughness between the both tested groups
at base line and after 1 year follow up. Concerning the results of enamel wear (vertical loss in mm)
opposing both ceramic crowns after 1 year of cementation, the results showed that the amount of enamel
wear opposing STML monolithic zirconia crowns was (0.0655 ± 0.0116 mm), which was significantly
higher than the amount of enamel wear opposing lithium silicate crowns which was (0.0457± 0.0099
mm) p<0.05. While the result of wear testing of STML monolithic zirconia crowns was (0.0203 ± 0.0049
mm), which was significantly less than the amount of wear of lithium-silicate crowns (0.0310 ± 0.0031
mm) p< 0.05.
Chi test was used to evaluate the parameters of the modified USPHS criteria, the follow up scores in
comparison to baselines of the two groups, revealed insignificant differences.
Conclusions: Within the limitations of the present study, no correlation between the surface
roughness changes and the amount of enamel wear among the two tested groups. Regarding the wear
characteristics of the antagonist enamel, STML monolithic zirconia crowns lead to more enamel wear
than Lithium- silicate crowns. While, STML monolithic zirconia ceramic material itself showed less
amount of wear than Lithium- silicate glass ceramic. The two materials reported no differences in
term of clinical performance, as well as gingival and periodontal response