Reasons for poor durability of resin-dentin bonds

说明(申请人提供)：牙齿着色树脂修复体耐久性差的一个主要原因是牙本质基质中的胶原酶在树脂粘结过程中暴露并被激活(Pashley等人，2004年；Tay等人，2006年b；Nishitani等人，2006年；Mazzoni等人，2006年)。这会导致胶原纤维逐渐但持续地降解，这些纤维将这些填充物固定在下面矿化的牙本质上。最近发现，洗必泰(CHX)是一种有效的抗菌剂，也具有强大的抗基质金属蛋白酶-2、-8和-9活性(Gendron等人，1999)，这促使我们确定CHX是否可以稳定树脂粘结的胶原并增加树脂-牙本质粘结的耐久性，从而节省频繁更换粘结修复体的成本。我们的体外成功(Pashley等人，2004年；Nishitani等人，2006年，Carrilho等人，2007a，Breschi等人，2009a)使用CHX来增加树脂-牙本质键的持久性使我们证明CHX在提高体内键的稳定性方面取得了成功(Heering等人，2005年；Carrilho等人，2007b；Brackett等人，2007年)。这些结果刺激了这项拨款申请，以更深入地挖掘MMPs CHX抑制的机制。我们注意到，CHX含有双胍基团，这些基团形成了酸性加成盐，阳离子电荷分散在双胍的五个相邻的仲胺氮原子上。这些化合物的功能类似于季铵化合物，季铵化合物也形成也具有抗菌作用的聚阳离子。我们最近发现了几种含季铵盐的单体对胶原酶具有抑制作用。这一结果可能会导致粘合剂配方的范式转变。通过在粘合剂混合物中加入能够抑制MMPs的“治疗性单体”，我们可能能够延长所有粘接树脂修复体的使用范围。在实现这一目标之前，我们需要对这类新型粘合剂单体进行评估。虽然它们抑制细菌胶原酶，但它们会抑制真正的MMPs吗？我们将使用可溶性荧光素标记的胶原蛋白来测试一些抗胶原溶解单体抑制可溶性牙本质基质金属蛋白酶活性的能力。然后，我们将测试它们使用相同的可溶性胶原底物抑制基质结合MMPs的能力。最后，我们将确定“AC”监视器是否能够抑制牙本质基质本身作为底物的结合MMPs的活性。我们还将确定“AC”单体是否可以防止牙本质基质机械性能的下降，这种情况通常会随着时间的推移而发生。最后，我们将学习如何将这些“AC”单体与粘附性共聚单体混合在一起，而不降低它们的转化率、润湿牙本质的能力或降低它们的初始(24小时)粘结强度。一旦我们证明我们可以产生高粘结强度，我们将使用疲劳寿命研究和初始与1年界面断裂韧性研究来测试使用对照共聚单体与混合“AC”单体的共聚单体制成的树脂-牙本质粘结的耐久性。如果这项工作的结果是成功的，我们将寻求更多的支持来进行这些最好的“AC”单体的临床试验，以实现我们的目标，提供更持久的树脂-牙本质结合。 公共卫生意义：我们成功地将洗必泰(CHX)局部应用于酸蚀牙本质，以抑制牙本质MMPs，并在体外和体内保持树脂-牙本质结合的完整性，这是非常令人满意的。洗必泰含有赋予分子阳离子电荷的强碱性双胍基团。季铵化合物(QAC)含有类似的阳离子电荷，它们的抗菌性能决定了它的抗菌活性和抗基质金属蛋白酶的活性。我们已经发现了一些含有QAC的单体可以抑制胶原酶。如果我们能将它们结合到粘接树脂中，我们就可能在粘结过程中永久抑制牙本质基质金属蛋白酶，这种基质金属蛋白被认为会破坏树脂与牙本质的结合。这类新的基质金属蛋白酶抑制剂是一个令人兴奋的新发现，具有深刻的临床潜力。它们在胶粘剂树脂中的成功应用可能会节省目前用于更换齿色树脂复合材料的数十亿美元。

DESCRIPTION (provided by applicant): A major reason for the poor durability of tooth-colored resin restorations is that collagenolytic MMPs in the dentin matrix are uncovered and activated during resin bonding procedures (Pashley et al., 2004; Tay et al., 2006b; Nishitani et al., 2006; Mazzoni et al., 2006). This results in gradual but continuous degradation of collagen fibrils that anchor these fillings to underlying mineralized dentin. The recent discovery that chlorhexidine (CHX), a potent antimicrobial agent, also has potent anti-MMP -2, -8 and -9 activity (Gendron et al., 1999), led us to determine if CHX can stabilize resin-bonded collagen and increase the durability of resin- dentin bonds thereby saving the cost of frequent replacement of bonded restorations. Our in vitro success (Pashley et al., 2004; Nishitani et al., 2006, Carrilho et al., 2007a, Breschi et al., 2009a) using CHX to increase the durability of resin-dentin bonds led us to demonstrate CHX's success in increasing the stability of bonds in vivo (Hebling et al., 2005; Carrilho et al., 2007b; Brackett et al., 2007). These results have stimulated this grant application to delve more deeply into the mechanisms responsible for CHX inhibition of MMPs. We noted that CHX contains biguanide groups that form acidic addition salts with a cationic charge delocated over the five neighboring secondary amine nitrogen atoms of the biguanides. These function similarly to quaternary ammonium compounds that also form polycations that are also antibacterial. We have recently discovered several quaternary ammonium-containing monomers that can inhibit Clostridium collagenase. This result may cause a paradigm shift in adhesive formulations. By incorporating "therapeutic monomers" capable of inhibiting MMPs in adhesive blends, we may be able to extend the service of all adhesive resin restorations. Before this goal can be realized, we need to evaluate this new class of adhesive monomers. Although they inhibit bacterial collagenase, will they inhibit true MMPs? We will test the ability of a number of anticollagenolytic ("AC") monomers for their ability to inhibit soluble dentin MMP activity using soluble fluorescein-labeled collagen. Then we will test their ability to inhibit matrix-bound MMPs using the same soluble collagen substrate. Finally, we will determine if the "AC" monitors can inhibit bound-MMPs activity on the dentin matrix itself, as a substrate. We will also determine if "AC" monomers prevent the decrease in mechanical properties of dentin matrices that normally occur over time. Finally, we will learn how to blend these "AC" monomers with adhesive comonomers without reducing their degree of conversion, ability to wet dentin, or lowering their initial (24 hr) bond strength. Once we have proven that we can produce high bond strengths, we will test the durability of resin-dentin bonds made with control comonomers versus comonomers mixed with "AC" monomers using fatigue lifetime studies and initial versus 1 yr interfacial fracture toughness studies. If the results of this work are successful, we will then seek additional support for clinical trials of the best of these "AC" monomers, in our goal to provide more durable resin-dentin bonds. PUBLIC HEALTH RELEVANCE: Our successful use of topical chlorhexidine (CHX) application to acid-etched dentin to inhibit dentin MMPs and maintain the integrity of resin-dentin bonds in vitro and in vivo has been very gratifying. Chlorhexidine contains strongly basic biguanide groups that impart cationic charges to the molecules. Quaternary ammonium compounds (QAC) contain similar cationic charges that are responsible for their antibacterial properties that are responsible both for its antimicrobial activity and for its anti-MMP activity. We have discovered a number of QAC-containing monomers that inhibit collagenases. If we can incorporate them into adhesive resins, we may be able to permanently inhibit dentin MMPs that are thought to degrade resin-dentin bonds, while we are bonding. This new class of MMP-inhibitors is an exciting new discovery with profound clinical potential. Their successful use in adhesive resins could potentially save billions of dollars currently spent on the replacement of tooth-colored resin composites.