Stappert Christian F J, Ozden Ummuhan, Gerds Thomas, Strub Jorg R
Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 100100, USA.
J Prosthet Dent. 2005 Aug;94(2):132-9. doi: 10.1016/j.prosdent.2005.05.023.
Laminate veneers are widely used in the management of unesthetic anterior teeth. However, limited information is available regarding the influence of preparation design on longevity of ceramic veneers.
This study evaluated the influence of preparation design on longevity and failure load of ceramic veneers bonded to human maxillary central incisors after cyclic loading and thermal cycling in a dual-axis masticatory simulator.
Sixty-four caries-free maxillary central incisors were divided into 4 groups (n = 16). The control group remained unprepared (NP). For Group WP, a window preparation was made. Specimens in Group IOP were prepared with an incisal overlap of 2 mm without palatal chamfer. For Group CVP, specimens were prepared with a complete-veneer design of 3-mm incisal reduction and 2-mm palatal extension. Forty-eight IPS Empress 1 ceramic veneers were bonded adhesively with dual-polymerizing composite (Variolink II). All specimens were subjected to cyclic mechanical loading (1.2 million cycles, cycle frequency 1.3 Hz, invariable palatal load 49 N) and thermal cycling (5 degrees C-55 degrees C, dwell time 60 seconds, 5500 cycles) in a masticatory simulator. Failure was defined by bulk fracture of a specimen. Subcritical crack patterns were observed. Surviving specimens were loaded in a universal testing machine until fracture. The failure-load values (N) (1.5 mm/min crosshead speed) were automatically recorded by controlling software. Statistical analysis of data was performed by Kruskal-Wallis analysis of variance (alpha = .05) and pairwise Wilcoxon rank sum tests (alpha = .05).
Three specimens from group NP, 1 specimen each from the WP and CVP groups, and 2 specimens from group IOP fractured during fatigue. After 1.2 million cycles, the highest crack rates were observed for complete veneers and originated in the palatal concavity extending to the facial surface. The median (interquartile range = x .25 - x .75 ) failure loads (N) were as follows: NP 713.3 (404.4-777.1), WP 549.5 (477.5-597.7), IOP 695.3 (400.0-804.6), and CVP 519.2 (406.1-732.9). No significant differences in longevity and failure load were demonstrated between natural teeth and teeth restored with ceramic veneers ( P = .555).
Maxillary teeth restored with the 3 types of IPS Empress 1 veneers showed fracture resistance similar to that of unprepared incisors ( P = .555).
层压贴面广泛应用于前牙美观修复。然而，关于预备设计对陶瓷贴面使用寿命的影响，现有信息有限。
本研究评估在双轴咀嚼模拟器中进行循环加载和热循环后，预备设计对粘结于人类上颌中切牙的陶瓷贴面使用寿命和破坏载荷的影响。
64颗无龋上颌中切牙分为4组（每组n = 16）。对照组不做预备（NP）。WP组进行开窗预备。IOP组制备切端重叠2mm且无腭侧肩台的试件。CVP组制备切端磨除3mm、腭侧延伸2mm的全贴面设计试件。48颗IPS Empress 1陶瓷贴面用双固化复合树脂（Variolink II）粘结。所有试件在咀嚼模拟器中进行循环机械加载（120万次循环，循环频率1.3Hz，恒定腭侧载荷49N）和热循环（5℃ - 55℃，停留时间60秒，5500次循环）。试件整体断裂定义为失败。观察亚临界裂纹模式。对存活的试件在万能试验机上加载直至断裂。控制软件自动记录破坏载荷值（N）（十字头速度1.5mm/min）。采用Kruskal - Wallis方差分析（α = 0.05）和两两Wilcoxon秩和检验（α = 0.05）对数据进行统计分析。
NP组有3个试件、WP组和CVP组各有1个试件、IOP组有2个试件在疲劳试验中发生断裂。120万次循环后，全贴面的裂纹发生率最高，裂纹起始于腭侧凹面并延伸至唇面。中位（四分位间距 = x.25 - x.75）破坏载荷（N）如下：NP组713.3（404.4 - 777.1），WP组549.5（477.5 - 597.7），IOP组695.3（400.0 - 804.6），CVP组519.2（406.1 - 732.9）。天然牙与陶瓷贴面修复牙在使用寿命和破坏载荷方面无显著差异（P = 0.555）。
用3种IPS Empress 1贴面修复的上颌牙显示出与未预备切牙相似的抗折性（P = 0.555）。
