Stappert Christian F J, Abe Pia, Kurths Volker, Gerds Thomas, Strub Jörg R
Department of Periodontology and Implant Dentistry, Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA.
J Adhes Dent. 2008 Feb;10(1):41-8.
To evaluate preparation designs of compromised cusps and whether or not they influence masticatory fatigue, fracture resistance, and marginal discrepancy of ceramic partial-coverage restorations (PCRs) luted on mandibular molars.
Sixty-four caries-free molars were equally divided into four groups. Control group NP received no preparation (NP). Group B-IN received a basic inlay (IN) preparation with buccal (B) cusp conservation and occlusal reduction of both lingual cusps. Group B-ON was prepared in the same way, except buccal cusps were prepared with an angle of 45 degrees to the occlusal plane (buccal onlay). Group B-OV preparation was similar to group B-ON, but buccal cusps received a further shoulder preparation on the buccal aspect (buccal overlap). Forty-eight all-ceramic IPS e.max Press PCRs were fabricated and luted adhesively. Specimens underwent mouth-motion fatigue (1.2 million cycles, 1.6 Hz, 49 N) and 5500 thermal cycles (5 degrees C/55 degrees C). Fracture patterns were observed. Surviving specimens were loaded until fracture. Marginal discrepancies were examined.
Only one specimen of group B-ON fractured during fatigue. Median fracture loads (N) [IQR = x(.25) - x(.75)]: group NP = 1604 N [1182-1851 N], group B-IN = 1307 N [1262-1587N], group B-ON = 1396 N [817-1750N], group B-OV = 1205 N [1096-1542N]. No significant differences in fracture resistance were found between restored molars and unprepared teeth (p _ 0.18). Different preparation designs showed no significant influence on PCR fracture resistance. Mouth-motion fatigue caused a significanty decrease of marginal accuracy in groups B-IN (p = 0.009) and B-ON (p = 0.008). Marginal discrepancy values of groups B-IN and B-OV were significantly different after fatigue (p = 0.045).
Ceramic coverage of compromised cusps did not demonstrate an increase of fracture resistance after fatigue when compared to less invasive partial-coverage restorations. However, enhanced exposure of restoration margins to occlusal wear could result in more extensive marginal discrepancies.
评估患牙牙尖的预备设计以及它们是否会影响下颌磨牙上粘结的陶瓷部分覆盖修复体（PCR）的咀嚼疲劳、抗折性和边缘差异。
64颗无龋磨牙平均分为四组。对照组NP未做预备（NP）。B-IN组进行基本嵌体（IN）预备，保留颊尖，降低两个舌尖的咬合面。B-ON组以相同方式预备，不同之处在于颊尖预备成与咬合平面呈45度角（颊面高嵌体）。B-OV组预备与B-ON组相似，但颊尖在颊侧进一步做肩台预备（颊侧覆盖）。制作48个全瓷IPS e.max Press PCR并粘结。标本进行口动疲劳试验（120万次循环，1.6Hz，49N）和5500次热循环（5℃/55℃）。观察折裂模式。对存活标本加载直至折裂。检查边缘差异。
B-ON组仅有1个标本在疲劳试验中折裂。中位抗折载荷（N）[四分位间距 = x(0.25) - x(0.75)]：NP组 = 1604N [1182 - 1851N]，B-IN组 = 1307N [1262 - 1587N]，B-ON组 = 1396N [817 - 1750N]，B-OV组 = 1205N [1096 - 1542N]。修复后的磨牙与未预备的牙齿在抗折性上无显著差异（p ≥ 0.18）。不同的预备设计对PCR的抗折性无显著影响。口动疲劳导致B-IN组（p = 0.009）和B-ON组（p = 0.008）的边缘精度显著降低。疲劳试验后，B-IN组和B-OV组的边缘差异值有显著差异（p = 0.045）。
与侵入性较小的部分覆盖修复体相比，患牙牙尖的陶瓷覆盖在疲劳后并未显示出抗折性增加。然而，修复体边缘暴露于咬合磨损的增加可能导致更广泛的边缘差异。
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