Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48108, USA.
J Adhes Dent. 2010 Feb;12(1):45-54. doi: 10.3290/j.jad.a17533.
The aim was to determine the in vitro fracture resistance of incisors restored with veneers and full ceramic crowns compared to unrestored teeth.
Seventy intact, extracted human maxillary central incisors were randomized and assigned to 7 groups (n = 10). The teeth in group 1 remained intact (control). The teeth in groups 2 to 6 were prepared and IPS Empress restorations were conditioned and bonded using an adhesive luting cement, Variolink II/Syntac (group 2: labial veneer with incisal overlap, group 3: 3/4 veneer with margin in enamel, group 4: 3/4 veneer with margin in dentin, group 5: crown with margin in enamel, group 6: crown with margin in dentin group 7: veneer on worn tooth. After finishing and polishing, specimens were stored in water and thermocycled for 2000 cycles between 5 degrees C and 55 degrees C. The maximal fracture load of the specimens (40-degree inclination) was determined using the universal testing machine (Zwick) at a constant crosshead speed (0.5 mm/min). The statistical analysis was performed using the Kruskal-Wallis test with Bonferroni correction (p < 0.05). Fracture surfaces were qualitatively analyzed by SEM.
All restored teeth with cervical preparation margins in enamel showed a fracture load not significantly different from the intact teeth (control). Restored teeth with cervical preparation margins in dentin showed a significantly lower fracture load. All restorations showed a fracture load far above 400 N, serving as functional reference for anterior teeth. The failures were predominantly cohesive.
For the restoration of tooth strength, defining the finishing lines of veneers and crowns in enamel is recommended. Restorations with finishing lines in dentin resulted in significant loss of strength. Three-quarter veneers with finishing lines in enamel are functionally equal to crowns with the advantage of conserving tooth structure.
旨在比较贴面和全陶瓷冠修复的切牙与未修复牙的体外抗折力。
70 颗完整的、提取的上颌中切牙随机分为 7 组（n = 10）。第 1 组的牙齿保持完整（对照）。第 2 组至第 6 组的牙齿经过预备，并用 IPS Empress 修复体进行处理，并使用粘合性水门汀 Variolink II/Syntac 进行粘结（第 2 组：切缘重叠的唇面贴面，第 3 组：牙釉质边缘的 3/4 贴面，第 4 组：牙本质边缘的 3/4 贴面，第 5 组：牙釉质边缘的冠，第 6 组：牙本质边缘的冠，第 7 组：磨损牙上的贴面。完成和抛光后，将标本在水中储存，并在 5°C 和 55°C 之间进行 2000 次热循环。使用万能试验机（Zwick）以恒定的十字头速度（0.5mm/min）测定标本的最大断裂载荷（40°倾斜）。使用 Kruskal-Wallis 检验和 Bonferroni 校正（p<0.05）进行统计分析。通过 SEM 对断裂面进行定性分析。
所有具有牙釉质颈缘预备的修复牙的断裂载荷与完整牙（对照）无显著差异。具有牙本质颈缘预备的修复牙的断裂载荷明显较低。所有修复体的断裂载荷均远高于 400N，可作为前牙的功能参考。失效主要是内聚性的。
为了恢复牙齿强度，建议在牙釉质中定义贴面和牙冠的修整线。具有牙本质修整线的修复体导致强度显著丧失。具有牙釉质边缘的 3/4 贴面在功能上与具有保留牙体结构优势的牙冠相同。
