An In Vitro Analysis of Wear Resistance of Commercially Available Acrylic Denture Teeth

Posterior denture teeth wear faster than the anterior teeth, causing occlusal prematurities and loss of vertical dimension of occlusion. The loss of vertical dimension of occlusion lays more stress on the anterior alveolar ridge, which in turn increases the rate of residual ridge resorption and causes loss of alveolar ridge height in the anterior segment and compromises esthetics. Hence it is important for the clinician to choose acrylic resin teeth with high wear resistance. The objective of the study is to investigate and compare the wear resistance of three different commercially available acrylic resin denture teeth. 60 specimens were tested for wear resistance in terms of loss of weight and loss in volume on a wear and friction monitor for 5,000 cycle wear periods (total of 10,000 cycles) under a 0.20 kg load. Statistical analysis used: The findings were analyzed using one way analysis of variance (ANOVA) and Tukey HSD test. Comparison of weight loss and volume loss between Surana ultradent, Premadent and Dentek showed highly significant difference, Surana ultraddent having better wear resistance. Surana ultradent acrylic resin denture had highest wear resistance amongst the three groups of tested samples.     

铸造牙间卡用于可摘局部义齿修复

目的:改善铸造可摘局部义齿固位体的美观性,减轻颊侧固位体的异物感。方法:在两基牙间的颊、龈外展隙内设置牙间卡(发夹卡)。结果:固位体金属外露少、隐蔽性好,美观明显改善,同时,体积小,无异物感。对34例不同牙缺失患者的使用,经1~2年观察,修复体固位良好,基牙未见松动和移位。结论:铸造牙间卡在美观、制作和异物感等方面明显优于常规铸造冠外固位体。     

Early Designs for the Occlusal Anatomy of Posterior Denture Teeth: Part III

Part III of this series of articles, like Part II, reviews the pioneering efforts in the 19th century to improve the quality of artificial teeth. The focus of this article, unlike that of Part II, is specifically modifications in the design of the occlusal anatomy of the 19th century denture teeth, along with the theories of mandibular movement that inspired those modifications. This article concludes the introductory phase of this project, which seeks to unravel the confusing history of the development of (posterior) denture teeth.     

Failure Modes with Point Loading of Three Commercially Available Denture Teeth

Purpose: A common problem associated with implant-supported prostheses is the fracture of denture teeth. This study was designed to compare the fracture modes of three denture teeth by compressive load at a 30° off-axis angle.
Material and Methods: Three denture teeth (Vident Duostat, Ivoclar Vivadent, and Dentsply Trubyte) processed to two denture base processing systems [injection-molded (IM) SR-Ivocap system and compression-molded (CM) denture base resin] were evaluated. Each specimen was processed to a metal framework. Ultimate failure strength of each system when point loaded at a 30° off-axis angle was recorded, along with a visual inspection of each specimen.
Results: The average load fracture for each group was (in N): Vident CM 1106.97 ± 223.20, Vident IM 1168.18 ± 322.52, Dentsply CM 1098.08 ± 286.32, Dentsply IM 1023.80 ± 282.45, Ivoclar CM 1616.98 ± 204.87, and Ivoclar IM 1373.54 ± 282.58. There was a significant difference between the groups and the Ivoclar CM group. The Ivoclar CM group had the highest average load force, and the Dentsply IM group had the lowest average load force. On average, the teeth within the groups fractured at a higher compression force than the average maximum occlusal force in natural dentition. Dentsply and Vident denture teeth fractured more horizontally, and the Ivoclar denture teeth fractured more vertically within the groups. There was no significant difference among the groups between the IM and CM processing methods.
Conclusions: In the present in vitro study, all specimens were able to withstand 30° off-axis loading with the exception of one specimen. With these results, this would indicate that these denture teeth are able to withstand normal occlusal forces.     

A Simplified Guide for Arranging 30° Pilkington Turner Posterior Denture Teeth in a Balanced Occlusion

A simple technique is presented for achieving balanced occlusion when setting 30 degrees Pilkington-Turner teeth. This technique involves the rotation of the mandibular posterior teeth around three axes: the vertical axis, to align the grooves and embrasures with the lateral path of the movement of the cusps; the mesio-distal axis, to achieve the Curve of Wilson; and the bucco-lingual axis, resulting in the Curve of Spee.     

Comparison of Stress Dissipation Pattern Underneath Complete Denture with Various Posterior Teeth form: An In Vitro Study

To evaluate the pattern of stress dissipation underneath the complete denture with various angled posterior teeth in both maxillary and mandibular arch. A 3D finite element models of residual ridge, mucosa, denture base in the coronal section were created from the dentures obtained from a patient, which were scanned and modeled. The coronal portion of the teeth was altered to stimulate the cuspal inclination of 0°, 20° and 33°, thus making the models. Special area of interest in bone, denture were selected to record the stresses. An vertical static load of 100N was applied through the mandibular model to the maxillary model. von Mises stresses developed in all the models were interpreted. Statistical analysis for comparison of stress values with different variables (0°–20°, 0°–33°, and 20°–33°) in various predefined areas of coronal section model was done using Student’s t test (paired). Stress of greater magnitude were observed with cuspal teeth i.e. 33° and 20°, where as 0° showed slightly less magnitude of stresses.     

Nasal Width as a Guide for the Selection of Maxillary Complete Denture Anterior Teeth in Four Racial Groups

PURPOSE: Selecting artificial teeth for edentulous patients is difficult when pre-extraction records are not available. Various guidelines have been suggested for determining the width of the maxillary anterior denture teeth. This study was undertaken to evaluate the use of the nasal width as a guide for the selection of proper width maxillary anterior denture teeth in four racial groups of the Brazilian population. MATERIALS AND METHODS: One hundred and sixty subjects (40 Whites, 40 Mulattos, 40 Blacks, and 40 Asians) were selected. Using a sliding caliper, the nasal width and the intercanine distance were measured. The Pearson product-moment correlation coefficient was used to determine the relationship between the above measurements. A prediction was made of the percentage of subjects of the White, Mulatto, Black, and Asian populations in which the selection error due to the clinical application of the method of the nasal width would be within 0 to 2 mm, within 2 to 4 mm, and greater than 4 mm. RESULTS: The four racial groups showed a weak correlation between the intercanine distance and the nasal width. In 39.7% of the White, 55.7% of the Mulatto, 81.9% of the Black, and 48.2% of the Asian populations, errors greater than 4 mm would be present with the use of the nasal width. CONCLUSIONS: The correlation found between the intercanine distance and the nasal width was not high enough to be used as a predictive factor. The relationship between natural tooth width and artificial tooth width as predicted by the nasal width showed that the nasal width method is not accurate for all the studied groups.     

粘结剂与核材料微漏的体外研究

目的 :讨论常用的粘结材料与核材料对修复体边缘微漏的影响。方法 :选用 4 5颗大小相似的完好前磨牙 ,随机分为 9个实验组。对离体牙进行标准的铸造金属全冠及固定尺寸的Ⅱ类洞牙体预备后 ,分别用 3种不同的核材料 (树脂、银汞、铸造合金 )充填窝洞。常规方法铸冠 ,用 3种不同的粘结材料 (锌汀、聚羧酸、玻璃离子 )进行粘固。温度循环、染色、包埋后 ,片切标本 ,镜下观察冠边缘及核下微漏。结果 :银汞核与树脂核下微漏小于铸造核 (P<0 .0 5 ) ,玻璃离子粘结剂抗微漏性能优于聚羧酸和锌汀 (P <0 .0 5 )。结论 :本实验提示 :玻璃离子抗微漏性能优于锌汀与聚羧酸。树脂核在预先对粘结面处理后 ,其抗微漏性能与银汞核近似 ,优于铸造合金核。粘结剂的选择对微漏有影响     

正畸结合固定修复前牙重度磨耗的临床研究

目的探讨正畸助萌技术结合固定修复对前牙重度磨耗者进行[牙合]重建的临床效果。方法对前牙重度磨耗的患者，采用正畸助萌技术伸长磨牙，适度增加[牙合]间距离，以便恢复前牙解剖形态，行前牙烤瓷固定修复。结果验重建后，牙列形态与咬合获得恢复，咀嚼功能良好。随访6～24个月无复发。结论正畸助萌结合固定修复是一种用于前牙重度磨耗[牙合]重建的有效方法，既可改善咀嚼功能和美观，又可保存后牙的牙体组织。     

In Vitro Effectiveness of a Terpenic Denture Cleanser on Old Biofilm Surfaces

Purpose

To assess the effects of terpenic denture cleanser on denture biofilm removal using scanning electron microscopy (SEM).

Materials and Methods

The internal surface biofilm of four maxillary dentures was elucidated with Caristop‐revelador Dual Tone, and 40 blue‐stained specimens (0.6 cm × 0.4 cm × 2 mm) were obtained. These specimens were randomly assigned to one of the following four groups of 10 specimens each: control, Eci Clean, Fitty Dent, and terpenic denture cleanser. The period of immersion in each solution was 12 hours. Biofilm removal was evaluated using SEM, and morphologically varying areas of the SEM images were quantified with Imaris software. The data were analyzed using Kolmogorov‐Smirnov, t‐tests, ANOVA, and Tamhane's tests (p = 0.05).

Results

Data revealed that terpenic denture cleanser removed significantly more biofilm than any other treatment examined in this study. The t‐tests revealed significant differences in the clean area that resulted from the use of the terpenic cleanser compared with the clean area that resulted from the use of Eci Clean (p = 0.013). Fitty Dent was the least effective and left dirty acrylic resin. The average areas with few removed layers were 59.3%, 43.3%, and 9.5% in Fitty Dent, Eci Clean, and terpenic cleanser groups, respectively. Tamhane's tests indicated that the Eci Clean and Fitty Dent groups were significantly different from the 0.5% terpenic cleanser group (p = 0.008).

Conclusion

The terpenic denture cleanser was effective in removing denture biofilm.     

Wear of three dental composites under different testing conditions

Although a great effort has been made to date with research on in vitro wear simulation testing, it is difficult to identify the relationship between the results of in vitro testing and in vivo observations. An intensive study into wear mechanisms is necessary for wear testing simulation. The objective of this research was to study the wear behaviour of three selected dental composites under different wear conditions to provide a more rational explanation for their wear mechanisms. Two typical wear conditions, two- and three-body wear, were conducted on the composites. The results showed that the wear losses had different rankings between two wear conditions. It is therefore unreliable to predict the clinical performance merely by wear loss ranking from in vitro wear testing. Further analysis on the wear surfaces indicated that three dental composites experienced different wear mechanisms under different wear conditions. It is concluded that in vitro analysis of wear mechanisms may lead to a better understanding of in vivo failure patterns. Similar wear mechanisms should be the premise for any correlation between the results of in vitro and in vivo studies.     

人工牙排列位置对下颌全口义齿固位及支持组织的影响

采用ＣＴ－数字化仪－ＣＡＤ系统建立了下颌无牙颌骨及其义齿的３个三维有限元模型，探讨在Ｈｅ力，口周肌力作用下，下颌人工牙排列位置对义齿固位和支持组织应力分布的影响，并测量了１０例口周肌动力及传统型全口义 工牙排列位置的差异。结果表明；Ｈｅ力作用下，人工牙排列干剩余牙槽嵴顶及水平偏离槽嵴顶舌，颊侧３ｍｍ，对牙骨应力分布无明显影响，但后牙位于下颌骨外斜嵴区对支持组织有利；正中Ｈｅ时，磨牙排列于牙槽嵴顶颊     

聚乳酸复合物预成乳牙根管桩的体外降解性研究

目的:评估聚乳酸/羟基磷灰石(PLA/HA)复合物的体外降解性。方法:本实验参照我国医疗器械生物学评价标准,将PLA/HA和PLA两种材料分别浸泡到磷酸盐缓冲液(PBS液)和蒸馏水中,分别在不同的时间点对试件进行一系列体外实验评价PLA/HA的体外降解性。结果:肉眼观察试件颜色逐渐变白且出现微裂纹;SEM显示:随降解时间延长,HA颗粒逐渐变小,PLA出现孔隙且大小不一;PLA/HA和PLA分子量逐渐较小;弹性模量和弯曲强度均有所衰减;PLA/HA和PLA中降解液的pH值均逐渐降低,且PLA比PLA/HA要下降的快。结论:PLA/HA具有一定的降解性能,在观察的10个月内,其力学强度能够维持乳牙的咬合力。