The ethical approval to conduct this retrospective multicenter practice-based study was
obtained from the Research Ethics Committee at the University of Sharjah (REC-23-09-11-01-F).
The present report will complie with the STROBE guidelines for cohort studies.
Participants selection Patient records at 7 private practices in the UAE will be searched for
the presence of posterior LD CAD-CAM crowns during 2013 to 2016. Inclusion criteria: adult
patient and indication for crown with or without DME. Exclusion criteria: poor oral hygiene
and active periodontal disease. A total of 560 eligible patients will be invited to a
clinical examination.
Clinical Examination The clinical evaluation will be conducted by three calibrated
independent prosthodontists. Patients will be requested to read and sign an informed consent
form to participate in the study. Intraoral photographs, Periapical and bitewing radiographs
will be obtained to assess the emergence profile of the DEM which should ideally reproduce
the normal morphology. Both the crowned tooth and the contralateral tooth were assessed
clinically for the following parameters: pocket depth (PD), BoP, and presence of plaque using
a plaque indicator liquid (Mira-2 Ton Liquid, Hager & Werken; Duisburg, Germany). Bone level
will be assessed by comparing a measurement from the margin of the tooth to the crest of the
bone on bitewing radiographs to corresponding preoperative radiographs.
A comprehensive assessment of the restored teeth will be carried out following the modified
United States Public Health Service (USPHS) criteria. The location of crown margin will be
recorded clinically and radiographically to assess the association between periodontal health
and margin location. The primary outcomes will be the survival rate and time to event. The
secondary outcome will be the success rate. The success is defined as a crown that had
remained unchanged over the observation period, while survival is defined as a crown that was
in situ at the examination visit but might exhibits chipping or have been repaired. Failure
will be scored for the followings: recurrent caries, loss of vitality, tooth fracture, and
crown fracture.
Statistical analysis Descriptive statistics were computed with a statistical software program
(IBM SPSS Statistics, v29; IBM Corp., Armonk, NY, USA). Each complication will be considered
as a statistical event. The statistical testing will be 2-tailed (a=.05). The McNemar
chi-squared and Fisher exact tests will be used to assess the severity of PD, BoP and plaque
deposition. Odds ratios and their 95% confidence intervals will be reported. The Pearson
chi-squared test for differences in proportions will be used to assess the relationship
between the location of margins and the associated condition of the periodontal tissues.
Kaplan-Meier survival analysis will be performed to calculate the overall crown survival and
success probabilities. Cox regression models will be used to evaluate the effect of various
confounding factors on the survival and success rates.