Non-invasive imaging of the crystalline structure within a human tooth

The internal crystalline structure of a human molar tooth has been non-destructively imaged in cross-section using X-ray diffraction computed tomography. Diffraction signals from high-energy X-rays which have large attenuation lengths for hard biomaterials have been collected in a transmission geometry. Coupling this with a computed tomography data acquisition and mathematically reconstructing their spatial origins, diffraction patterns from every voxel within the tooth can be obtained. Using this method we have observed the spatial variations of some key material parameters including nanocrystallite size, organic content, lattice parameters, crystallographic preferred orientation and degree of orientation. We have also made a link between the spatial variations of the unit cell lattice parameters and the chemical make-up of the tooth. In addition, we have determined how the onset of tooth decay occurs through clear amorphization of the hydroxyapatite crystal, and we have been able to map the extent of decay within the tooth. The described method has strong prospects for non-destructive probing of mineralized biomaterials.     

Osteonecrosi dei mascellari associata a bisfosfonati,denosumab e farmaci anti-angiogenetici nei pazienti oncologici e osteoporotici: prevenzione dentale e sicurezza dei trattamenti odontoiatrici

Objectives

Specific protocols are suggested for the dental management of patients taking bisphosphonates, denosumab or antiangiogenic agents so as to reduce the risk of osteonecrosis of the jaw (ONJ).

Materials and methods

The authors, directly involved with the recent publication of the Raccomandazioni clinico-terapeutiche sull’osteonecrosi delle ossa mascellari associata a bisfosfonati e sua prevenzione, endorsed by Società Italiana di Chirurgia Maxillo-Facciale (SICMF) and Società Italiana di Patologia e Medicina Orale (SIPMO), survey and discuss the dental management of patients taking bone modifiers and/or anti-angiogenic agents at risk of ONJ, on the basis of available scientific information.

Results and conclusions

ONJ should be considered the most emerging disease that affects the oral cavity; ONJ is mainly due to bisphosphonates, but it has been also associated with denosumab and anti-angiogenic agents in recent years. Thousands of cases have been reported in the scientific literature so far, with important implications for the National Health Systems. ONJ can heavily impact on patients’ quality of life. In all industrialized nations and in Italy too, guidelines or recommendations for the prevention and treatment of ONJ have been drafted. In the beginning, these documents were centred on the care of cancer patients taking intravenous bisphosphonates, but soon after they were upgraded to include the less-frequent ONJ in non-cancer patients taking bisphosphonates. To reduce the occurrence of ONJ in patients at risk, the role of the dentist is crucial in the effort to eliminate the known local risk factors applying specific dental treatment protocols, wherever indicated, and select the proper timing to deliver such treatments, both in cancer and non-cancer patients.     

牙齿几何外形和模型底座厚度对隐形矫治器厚度的影响

目的研究牙齿几何外形和模型底座厚度对热成型隐形矫治器厚度的影响。方法层析扫描标准上颌模型,形成数字图像,通过数字化三维图像处理,激光快速成型输出底座厚度分别为0、1、2、3、4、5、6、7、8、9、10 mm的树脂模型共11副,在每个树脂模型上通过热压膜成型制作10副矫治器,标记每副矫治器上14个牙位的唇颊面和舌腭面牙冠面轴点,使用千分尺测量牙冠面轴点处矫治器的膜片厚度,比较热压膜成型后不同牙位上隐形矫治器的厚度,分析厚度分布规律。结果底座厚度为0 mm时,隐形矫治器中切牙到第二磨牙唇颊面厚度从0.398 mm均匀递增到0.504 mm,坐标图表现为均匀递增的直线,膜片厚度随牙位变化的直线公式为y=0.019x+0.379,拟合度和相关性良好。尖牙腭面膜片厚度最大,第一磨牙腭面膜片厚度大于第二前磨牙,表现为S形曲线。不同底座厚度的树脂模型上热成型的矫治器唇颊面和舌腭面膜片厚度随牙位变化的规律基本相同。隐形矫治器唇颊面和舌腭面的膜片厚度随模型底座厚度的增加呈递减趋势。结论隐形矫治器唇颊面厚度从前牙到后牙均匀递增;矫治器腭面厚度以尖牙最厚,分布无明显规律。模型底座厚度对隐形矫治器厚度有影响。     

Effect of water contamination on the shear bond strength of self-ligating brackets

PurposeThe aim of the present study is to evaluate the effect of water contamination on the shear bond strength (SBS) and adhesive remnant index (ARI) score of self-ligating brackets.Materials and methodsOne conventional bracket and three different self-ligating brackets were bonded onto 160 bovine permanent mandibular incisors, divided randomly into 8 groups. For each type of bracket, 20 samples were bonded on dry enamel and 20 after water contamination. After 24 h, all specimens were tested for SBS using an Instron Universal Testing Machine, and ARI scores were evaluated.ResultsAll groups showed clinically adequate SBSs. Quick brackets bonded onto dry enamel showed significantly higher SBSs than all other groups tested, whereas the lowest shear strength values were recorded for Step, Quick, and Damon 3MX brackets bonded onto contaminated enamel and for Damon 3MX onto dry enamel. Frequency distribution of ARI Scores showed a prevalence of ARI “2” and “3” for all the groups tested.ConclusionsWater contamination reduces the SBS of self-ligating brackets, but significant differences have been found only for Quick brackets. All groups showed a significant higher frequency of ARI Score of “2” and “3”.