Randmorphologie, Dichtigkeit und Passung von Gussobjekten aus dem Phantomkurs der Zahnerhaltungskunde des Jahres 1999 im Vergleich zu professionell gefertigten Restaurationen - eine Studie zur Qualitätssicherung der Lehre -

Clinical background: The durability of cast restorations fixed with zinc phosphate cement is determined by marginal fit and closeness. Aim: This investigation compares the fit quality of inlays and partial crowns produced by students and by professionals. Material and method: The student test group (tg) consists of 30 randomly chosen multisurfaced inlays (tg1) and partial crowns (tg2), which were prepared in the phantomhead. The professional control group (cg) manufactured 9 Inlays (cg1) and partial crowns (cg2) under the same conditions. All restorations were conventionally cemented with zinc phosphate cement and analysed by dye penetration exposure, quantitative margin analysis using a scanning electron microscope (SEM) and the internal fit using a light microscope. Statistics: Examination on normal distribution, t-test. Results: a) SEM: The fraction of a marginal discrepancy <50µm was highly significant (p=0,001) for cg1+2 than for tg1+2. Discrepancies between 50-100µm were significant (p=0,002) and highly significant (p=0,001) for cg1 and cg2 respectively. The test group showed discrepancies over 100µm of approximately 40% for tg1 and over 50% for tg2. The discrepancies of cg1+2 were highly significant lower (p=0,001). b) Internal fit: The absolute marginal discrepancy is 113µm (tg1), 129µm (tg2), 45µm (cg1) and 54µm (cg2). The marginal gaps were in all groups under 60µm. The internal gap values did not reveal differences between the groups. c) The dye penetration level is between 2 and 4 in all groups. Conclusion: Due to the poor performance of the test group, student dental makings should not be used for patients needs.