The objective of this systematic review was to assess tooth wear against ceramic crowns in posterior region in vitro and in vivo. An electronic PubMed search was conducted to identify studies on tooth wear against cer...The objective of this systematic review was to assess tooth wear against ceramic crowns in posterior region in vitro and in vivo. An electronic PubMed search was conducted to identify studies on tooth wear against ceramic crowns in posterior region. The selected studies were analyzed in regard to type of crowns, natural antagonist, measuring protocol and outcome. From a yield of 1 000 titles, 43 articles were selected for full-text analysis; finally, no in vitro and only five in vivo studies met the inclusion criteria. As there is heterogeneity in design, used measuring method, ceramics and analysis-form, a meta-analysis was not possible. Results of these studies are very controversial which makes a scientifically valid comparison impossible. This review indicated that some all-ceramic crowns are as wear friendly as metal-ceramic crowns. Up to now, it has been impossible to associate tooth wear with any specific causal agent. The role of ceramic surface treatment that might be responsible for the changing in rate of tooth wear seems undetermined as yet through clinical trials. The literature reveals that studies on this topic are subject to a substantial amount of bias. Therefore, additional clinical studies, properly designed to diminish bias, are warranted.展开更多
Aim: To describe the presence, frequency of attrition in permanent dentition of human skulls from two ancient archeological locations. Aims: To determine the rate of attrition using a specific quantitative and qualita...Aim: To describe the presence, frequency of attrition in permanent dentition of human skulls from two ancient archeological locations. Aims: To determine the rate of attrition using a specific quantitative and qualitative method. Methods: Twenty one human skulls from two ancient archeological necropolises (Vendenis and Municipium Dardanorum DD) were included in the analysis of samples for this study. A total of 498 teeth were present in all human skulls. The skulls (with their accompanying teeth) were then divided into groups according to locality of origin, age and sex. Macroscopic (observational) analysis of the teeth relied on inspection and exploration of the teeth in their totality. The classification system that was used to rate tooth wear was Tooth Wear Index (TWI). Statistical analysis used: Chitest for small samples was used to evaluate the observations obtained from the study. Multiple Logistic Regression Analysis was not performed due to the small number of teeth and the content of zero values in respective age groups. Results: The results show that out of total 498 teeth, 89.35% had attrition and 10.65% had no attrition or Grade 0 TWI. 21.48% were Grade 1, 28.71% Grade 2, 26.90% Grade 3, 7.42% Grade 4 and 4.81% Grade 5. Conclusions: Grade 2 and higher rate of attrition, was predominantly present in first permanent molars.展开更多
Profile shift is a highly effective technique for optimizing the performance of spur gear transmission systems.However,tooth surface wear is inevitable during gear meshing due to inadequate lubrication and long-term o...Profile shift is a highly effective technique for optimizing the performance of spur gear transmission systems.However,tooth surface wear is inevitable during gear meshing due to inadequate lubrication and long-term operation.Both profile shift and tooth surface wear(TSW)can impact the meshing characteristics by altering the involute tooth profile.In this study,a tooth stiffness model of spur gears that incorporates profile shift,TSW,tooth deformation,tooth contact deformation,fillet-foundation deformation,and gear body structure coupling is established.This model efficiently and accurately determines the time-varying mesh stiffness(TVMS).Additionally,an improved wear depth prediction method for spur gears is developed,which takes into consideration the mutually prime teeth numbers and more accurately reflects actual gear meshing conditions.Results show that consideration of the mutual prime of teeth numbers will have a certain impact on the TSW process.Furthermore,the finite element method(FEM)is employed to accurately verify the values of TVMS and load sharing ratio(LSR)of profile-shifted gears and worn gears.This study quantitatively analyzes the effect of profile shift on the surface wear process,which suggests that gear profile shift can partially alleviate the negative effects of TSW.The contribution of this study provides valuable insights into the design and maintenance of spur gear systems.展开更多
Background: Tooth surface loss (TSL) is a progressive process arising from erosion, abrasion, attrition or abfraction. It can affect individuals of any age group: children, young adult, adults or the elderly and can c...Background: Tooth surface loss (TSL) is a progressive process arising from erosion, abrasion, attrition or abfraction. It can affect individuals of any age group: children, young adult, adults or the elderly and can compromise the health of individual tooth or the entire dentition leading to poor quality of life of the affected person. Objective: To evaluate the pattern of TSL among dental patients in a Nigerian Teaching Hospital and to assess the impact of TSL on their quality of life. Subjects and Methods: The study was a cross-sectional study among patients with TSL in a Nigerian Teaching Hospital. The Oral Health Impact Profile-14 (OHIP-14) questionnaire was used to obtain information on the impact of TSL on the quality of life of the participants. Data collected were analysed using IBM SPSS version 20. Chi-square test was used to assess association between types of TSL and quality of life of the patients. Level of significance was set at p ≤ 0.05. Results: One hundred and twenty-five patients (Males = 72;Females = 53) with tooth wear lesions participated in the study. The most common type of tooth surface loss was attrition (40%) followed by abrasion (23.2%). The highest impact of TSL on the quality of life was painful sensation strongly affecting 39 (31.2%) patients. This was followed by problem with chewing. There was no statistically significant relationship between patients’ quality of life and types of tooth surface loss. Conclusion: The most common negative impact of TSL on patient quality of life was painful sensation.展开更多
The aim of this study was to evaluate the effect of chewing simulation on wear of artificial enamel abraded against zirconia-based crowns. Fifteen crown preparations were scanned for the manufacturing of crowns using ...The aim of this study was to evaluate the effect of chewing simulation on wear of artificial enamel abraded against zirconia-based crowns. Fifteen crown preparations were scanned for the manufacturing of crowns using computer-aided-design/computer-aided-machining technique (CAD/CAM), according to the following (n = 5): Polished (PM) and glazed (GM) monolithic zirconia (1.5 mm uniform thickness), and Bilayer (BL - 0.8 mm zirconia coping, 0.7 mm porcelain veneer) crowns. The samples were cemented and chewing simulation (2.5 million cycles/0-80N/artificial saliva/37°C) was performed with steatite indenters (6 mm diameter) as antagonists. Assuming the uniformity of the unaged samples, antagonists were scanned using a surface profilometer and the material loss volume was calculated. Roughness of the crowns’ occlusal surface was also analyzed using the profilometer. Scanning electron microscopy was used to characterize the abraded surface. One-way ANOVA and Tukey test (p = 0.05) were employed for analysis of wear results. A significant difference was observed among the groups (p 3 ± 0.015) than those abraded against monolithic zirconia, polished (PM - 0.167 mm3 ± 0.02) and glazed (0.101 mm3 ± 0.03), which were similar to each other. Veneering porcelain results in more pronounced wear of the artificial enamel than monolithic zirconia. However, mastication against monolithic Y-TZP also imposes wear to the opposing teeth.展开更多
A numerical simulation model is proposed to predict the wear depth of gears,where Archard's wear equation and a nonlinear dynamic model are combined to establish a wear calculation model under dynamic conditions.T...A numerical simulation model is proposed to predict the wear depth of gears,where Archard's wear equation and a nonlinear dynamic model are combined to establish a wear calculation model under dynamic conditions.The dynamic meshing force,determined by the non-linear dynamic model,and the sliding coefficient are used by Archard's wear equation to calculate the surface wear.Then the dynamic meshing force and sliding coefficient would be recalculated according to the surface wear state.After repeated iterations,the simulation results show that the peak and fluctuation of the meshing force increase first,then decrease,and eventually maintain stability during the process of wear.As for the distribution of wear depth,its fluctuation also increases first and then declines.Finally,the distribution of wear depth becomes V-shaped.Comparing the trends of the two factors,it is clear that the meshing force and wear depth are closely related.Moreover,the wear rate maintains a higher constant value first and then declines to a lower constant value.展开更多
On the basis of theoretical analyses and calculations of high speed continuous impact force and tool notch surface temperature acted upon by burr and serrated chip edge, a notch wear model of low stress value and temp...On the basis of theoretical analyses and calculations of high speed continuous impact force and tool notch surface temperature acted upon by burr and serrated chip edge, a notch wear model of low stress value and temperature impact fatigue was established. Saw-tooth-shaped burr and fin-shaped chip edge continuously impacts the rake face and flank face at high speed and high fre-quency, which results in a V-shaped notch wear. An experiment was done to validate that the saw-tooth-shaped burr does affect the notch wear. This model can be utilized to solve reasonably many problems that cannot be explained by any other theoretical assumptions.展开更多
盾构滚刀磨损方面的研究主要集中于盘形滚刀,对扁齿滚刀的磨损特性认识较少。为明确中风化砂岩地层掘进时扁齿滚刀的磨损规律,通过现场测量南京地铁6号线金陵石化—十月广场(简称金十区间)扁齿滚刀磨损数据,分析中风化砂岩地层扁齿滚刀...盾构滚刀磨损方面的研究主要集中于盘形滚刀,对扁齿滚刀的磨损特性认识较少。为明确中风化砂岩地层掘进时扁齿滚刀的磨损规律,通过现场测量南京地铁6号线金陵石化—十月广场(简称金十区间)扁齿滚刀磨损数据,分析中风化砂岩地层扁齿滚刀的磨损规律和主要控制参数,并对后续换刀点的磨损情况进行预测和检验。结果表明:扁齿滚刀的磨损量具有非连续特性,该参数无法识别出中等磨损状态;扁齿滚刀磨损量和旋转半径、切割距离之间并非单调关系,扁齿滚刀的磨损系数波动很大,不宜用于磨损量预测;采用破岩体积参数能较好地预测扁齿滚刀的磨损情况,在中风化砂岩地层掘进时,扁齿滚刀的有效破岩寿命约为700~1000 m ^(3),显著高于该地层中盘形滚刀的使用寿命。展开更多
文摘The objective of this systematic review was to assess tooth wear against ceramic crowns in posterior region in vitro and in vivo. An electronic PubMed search was conducted to identify studies on tooth wear against ceramic crowns in posterior region. The selected studies were analyzed in regard to type of crowns, natural antagonist, measuring protocol and outcome. From a yield of 1 000 titles, 43 articles were selected for full-text analysis; finally, no in vitro and only five in vivo studies met the inclusion criteria. As there is heterogeneity in design, used measuring method, ceramics and analysis-form, a meta-analysis was not possible. Results of these studies are very controversial which makes a scientifically valid comparison impossible. This review indicated that some all-ceramic crowns are as wear friendly as metal-ceramic crowns. Up to now, it has been impossible to associate tooth wear with any specific causal agent. The role of ceramic surface treatment that might be responsible for the changing in rate of tooth wear seems undetermined as yet through clinical trials. The literature reveals that studies on this topic are subject to a substantial amount of bias. Therefore, additional clinical studies, properly designed to diminish bias, are warranted.
文摘Aim: To describe the presence, frequency of attrition in permanent dentition of human skulls from two ancient archeological locations. Aims: To determine the rate of attrition using a specific quantitative and qualitative method. Methods: Twenty one human skulls from two ancient archeological necropolises (Vendenis and Municipium Dardanorum DD) were included in the analysis of samples for this study. A total of 498 teeth were present in all human skulls. The skulls (with their accompanying teeth) were then divided into groups according to locality of origin, age and sex. Macroscopic (observational) analysis of the teeth relied on inspection and exploration of the teeth in their totality. The classification system that was used to rate tooth wear was Tooth Wear Index (TWI). Statistical analysis used: Chitest for small samples was used to evaluate the observations obtained from the study. Multiple Logistic Regression Analysis was not performed due to the small number of teeth and the content of zero values in respective age groups. Results: The results show that out of total 498 teeth, 89.35% had attrition and 10.65% had no attrition or Grade 0 TWI. 21.48% were Grade 1, 28.71% Grade 2, 26.90% Grade 3, 7.42% Grade 4 and 4.81% Grade 5. Conclusions: Grade 2 and higher rate of attrition, was predominantly present in first permanent molars.
基金Supported by National Natural Science Foundation of China (Grant No.52275061)。
文摘Profile shift is a highly effective technique for optimizing the performance of spur gear transmission systems.However,tooth surface wear is inevitable during gear meshing due to inadequate lubrication and long-term operation.Both profile shift and tooth surface wear(TSW)can impact the meshing characteristics by altering the involute tooth profile.In this study,a tooth stiffness model of spur gears that incorporates profile shift,TSW,tooth deformation,tooth contact deformation,fillet-foundation deformation,and gear body structure coupling is established.This model efficiently and accurately determines the time-varying mesh stiffness(TVMS).Additionally,an improved wear depth prediction method for spur gears is developed,which takes into consideration the mutually prime teeth numbers and more accurately reflects actual gear meshing conditions.Results show that consideration of the mutual prime of teeth numbers will have a certain impact on the TSW process.Furthermore,the finite element method(FEM)is employed to accurately verify the values of TVMS and load sharing ratio(LSR)of profile-shifted gears and worn gears.This study quantitatively analyzes the effect of profile shift on the surface wear process,which suggests that gear profile shift can partially alleviate the negative effects of TSW.The contribution of this study provides valuable insights into the design and maintenance of spur gear systems.
文摘Background: Tooth surface loss (TSL) is a progressive process arising from erosion, abrasion, attrition or abfraction. It can affect individuals of any age group: children, young adult, adults or the elderly and can compromise the health of individual tooth or the entire dentition leading to poor quality of life of the affected person. Objective: To evaluate the pattern of TSL among dental patients in a Nigerian Teaching Hospital and to assess the impact of TSL on their quality of life. Subjects and Methods: The study was a cross-sectional study among patients with TSL in a Nigerian Teaching Hospital. The Oral Health Impact Profile-14 (OHIP-14) questionnaire was used to obtain information on the impact of TSL on the quality of life of the participants. Data collected were analysed using IBM SPSS version 20. Chi-square test was used to assess association between types of TSL and quality of life of the patients. Level of significance was set at p ≤ 0.05. Results: One hundred and twenty-five patients (Males = 72;Females = 53) with tooth wear lesions participated in the study. The most common type of tooth surface loss was attrition (40%) followed by abrasion (23.2%). The highest impact of TSL on the quality of life was painful sensation strongly affecting 39 (31.2%) patients. This was followed by problem with chewing. There was no statistically significant relationship between patients’ quality of life and types of tooth surface loss. Conclusion: The most common negative impact of TSL on patient quality of life was painful sensation.
文摘The aim of this study was to evaluate the effect of chewing simulation on wear of artificial enamel abraded against zirconia-based crowns. Fifteen crown preparations were scanned for the manufacturing of crowns using computer-aided-design/computer-aided-machining technique (CAD/CAM), according to the following (n = 5): Polished (PM) and glazed (GM) monolithic zirconia (1.5 mm uniform thickness), and Bilayer (BL - 0.8 mm zirconia coping, 0.7 mm porcelain veneer) crowns. The samples were cemented and chewing simulation (2.5 million cycles/0-80N/artificial saliva/37°C) was performed with steatite indenters (6 mm diameter) as antagonists. Assuming the uniformity of the unaged samples, antagonists were scanned using a surface profilometer and the material loss volume was calculated. Roughness of the crowns’ occlusal surface was also analyzed using the profilometer. Scanning electron microscopy was used to characterize the abraded surface. One-way ANOVA and Tukey test (p = 0.05) were employed for analysis of wear results. A significant difference was observed among the groups (p 3 ± 0.015) than those abraded against monolithic zirconia, polished (PM - 0.167 mm3 ± 0.02) and glazed (0.101 mm3 ± 0.03), which were similar to each other. Veneering porcelain results in more pronounced wear of the artificial enamel than monolithic zirconia. However, mastication against monolithic Y-TZP also imposes wear to the opposing teeth.
基金Supported by the National Natural Science Foundation of China(51475044)
文摘A numerical simulation model is proposed to predict the wear depth of gears,where Archard's wear equation and a nonlinear dynamic model are combined to establish a wear calculation model under dynamic conditions.The dynamic meshing force,determined by the non-linear dynamic model,and the sliding coefficient are used by Archard's wear equation to calculate the surface wear.Then the dynamic meshing force and sliding coefficient would be recalculated according to the surface wear state.After repeated iterations,the simulation results show that the peak and fluctuation of the meshing force increase first,then decrease,and eventually maintain stability during the process of wear.As for the distribution of wear depth,its fluctuation also increases first and then declines.Finally,the distribution of wear depth becomes V-shaped.Comparing the trends of the two factors,it is clear that the meshing force and wear depth are closely related.Moreover,the wear rate maintains a higher constant value first and then declines to a lower constant value.
文摘On the basis of theoretical analyses and calculations of high speed continuous impact force and tool notch surface temperature acted upon by burr and serrated chip edge, a notch wear model of low stress value and temperature impact fatigue was established. Saw-tooth-shaped burr and fin-shaped chip edge continuously impacts the rake face and flank face at high speed and high fre-quency, which results in a V-shaped notch wear. An experiment was done to validate that the saw-tooth-shaped burr does affect the notch wear. This model can be utilized to solve reasonably many problems that cannot be explained by any other theoretical assumptions.
文摘盾构滚刀磨损方面的研究主要集中于盘形滚刀,对扁齿滚刀的磨损特性认识较少。为明确中风化砂岩地层掘进时扁齿滚刀的磨损规律,通过现场测量南京地铁6号线金陵石化—十月广场(简称金十区间)扁齿滚刀磨损数据,分析中风化砂岩地层扁齿滚刀的磨损规律和主要控制参数,并对后续换刀点的磨损情况进行预测和检验。结果表明:扁齿滚刀的磨损量具有非连续特性,该参数无法识别出中等磨损状态;扁齿滚刀磨损量和旋转半径、切割距离之间并非单调关系,扁齿滚刀的磨损系数波动很大,不宜用于磨损量预测;采用破岩体积参数能较好地预测扁齿滚刀的磨损情况,在中风化砂岩地层掘进时,扁齿滚刀的有效破岩寿命约为700~1000 m ^(3),显著高于该地层中盘形滚刀的使用寿命。
