Martin Groten

Determination of the minimum number of marginal gap measurements required for practical in-vitro testing.

STATEMENT OF PROBLEM Gap measurements along margins are frequently used to assess the quality of single crowns. However, the number of gap measurements required for clinically relevant results in laboratory studies is not known. PURPOSE This study estimated the minimum number of gap measurements on margins of single crowns to produce relevant results for gap analysis. METHODS AND MATERIAL Ten all-ceramic crowns were fabricated on a master steel die. Gaps along crown margins were investigated in a scanning electron microscope on the master steel die without cementation and on replica dies after conventional cementation. Measurements were made in 100 microm steps according to 3 gap definitions. The initial number of measurements per crown (n = 230) was reduced to smaller subsets using both systematic and random approaches to determine the impact on the quality of results. RESULTS On the data of gap definition 1, reduction from 230 to about 50 measurements caused less than +/-5 microm variability for arithmetic means. Analysis of standard errors showed slowly increasing values smaller than 3 microm, both indicating no relevant impact on the quality of results. Smaller data sizes yielded accelerated increase of standard errors and divergent variabilities of mean. The minimum of 50 measurements did not depend on gap definition or on cementation condition. CONCLUSION Fifty measurements are required for clinically relevant information about gap size regardless of whether the measurement sites are selected in a systematic or random manner, which is far more than what current in vitro studies use.

Complete rehabilitation of compromised full dentitions with adhesively bonded all-ceramic single-tooth restorations: Long-term outcome in patients with and without amelogenesis imperfecta

OBJECTIVES This clinical follow-up evaluated the long-term outcome of full-mouth rehabilitations with adhesively bonded all-ceramic restorations in patients suffering from amelogenesis imperfecta (AI) or affected by extensive tooth wear including a loss of the vertical dimension of occlusion. MATERIALS AND METHODS Included for evaluation were all patients treated with adhesively bonded monolithic single-tooth restorations made of silicate or lithium disilicate ceramics; allowing a maximum four missing teeth and a facial feldspathic veneering of LDS anterior crowns. After treatment, patients have been enrolled in a recall program for dental check-ups including quality assessment of the restorations. Patients answered the oral health impact profile (OHIP-14) at their last visit. RESULTS Seventeen patients (mean age = 35 ± 18 years) were observed up to 16.5 years (mean: 6.2 ± 3.8 years). 12 out of 450 restorations failed due to core fracture (n = 7), tooth fracture (n = 2), one secondary caries, one chip-off grade 3, and one fixed dental prosthesis due to discomfort. The overall mean survival rate of the single-tooth restorations was estimated 99.4% at 5 and 91.4% at 10 years. The overall mean success rate was estimated 92.6% at 5 and 81.4% at 10 years, mainly due to chip-offs and crack formation (27 out of 31 relative failures). The mean annual failure rates (AFR) range between 1.5 and 2% over the years, but non-AI patients were affected more frequently by early technical complications in the facial veneering of anteriors, resulting in an AFR ranging between 5.2 and 4%. Quality assessment revealed stable color, form and marginal integrity in all patients up to ten years. The distribution of OHIP values is comparable to the representative sample of healthy patients. CONCLUSION Adhesively bonded single-tooth restorations provided a high clinical quality in the long-run. However, while the survival and success were excellent in AI patients, restorations in non-AI patients were affected by a higher complication rate, likely related to a higher risk profile due to a history of bruxism and tooth wear.

Ästhetik und Funktion mit keramischen Veneers

Adhasive, keramische Veneers stellen im Hinblick auf Asthetik, Funktion, Langlebigkeit und Atraumatik eine immer interessanter werdende Behandlungsmethode dar. Sie wird auch in der Literatur immer haufiger erwahnt.

Konventionell zementierte Keramikkronen

Jacketkronen, also metallfreie Vollkeramikkronen, waren die ersten Kronen zur Versorgung von Einzelzahnen mit einem asthetischen Anspruch. Ihre Entwicklung nahm bereits im 19. Jahrhundert ihren Anfang und geht vor allem auf Charles Land, den Pionier der Jacketkrone, zuruck.

Klinik des Keramikinlays

Adhasiv befestigte Keramikrestaurationen zeichnen sich klinisch durch ihre einzigartigen asthetischen Eigenschaften aus. Die dabei verwendeten Keramiken leiten sich von den naturlich vorkommenden Feldspatmineralien ab und lassen sich in Farbe, Transparenz und Transluzenz dem Erscheinungsbild des naturlichen Zahnes weitgehend angleichen. Keine andere Gruppe keramischer oder sonstiger dentaler Werkstoffe vermag das mit der gleichen Vollkommenheit.