外力方向对防护牙托性能影响的有限元分析

目的: 运用有限元分析评估外力方向对牙托缓冲能力的影响。方法: 采集仿真模型锥形束CT（CBCT）影像资料,利用MIMICS软件建立分析模型。运用ABAQUS软件模拟研究在牙托厚度不同的情况下（分别为0、1.5、3、4.5和6 mm）,经不同方向外力（撞击方向与牙长轴交角分别为30°、60°、90°和120°）撞击后,牙体表面的应力变化情况,进而评价牙托的缓冲能力。结果: 在研究实验条件下,当牙托厚度较薄时（1.5 mm和3 mm）,与其他方向相比,牙托缓冲效率在60°交角时最低,在120°交角时最高。而在牙托厚度增加后（4.5 mm和6 mm）,牙托缓冲效率在90°交角时最低,在30°交角时最高。外力方向不同时,牙托的应力缓冲效率随着牙托厚度的增加而提高。结论: 外力方向对防护牙托的缓冲能力有一定影响,但其易受牙托厚度的影响。     

定制牙托膜片切牙区厚度变化的影响因素

佩戴运动牙托可以缓冲外力,降低颌面部损伤的风险.运动牙托种类较多,其中个性化定制运动牙托具有较好的保护作用和较高的舒适度而备受欢迎.个性化定制运动牙托的膜片加热后可发生延展,随后发生厚度变化,尤以切牙区膜片的厚度变化更能影响其保护性能;因此,笔者就影响个性化定制运动牙托膜片切牙区的厚度变化的膜片硬度、膜片形状和膜片表面设计等膜片因素,工作模厚度和工作模摆放角度等工作模因素,加压方法,夹持托盘形状、夹持方式和夹持托盘与工作模底座的距离等夹持因素,加压时间等的研究进展作一综述.     

运动防护牙托在少年儿童中的应用及可替换内衬粘接性能的研究

目的检测内村材料和防护牙托主体粘结后的抗剪切强度；探讨将重衬法应用于替牙期定制类防护牙托的可行性。方法为22例少年儿童制作了防护牙托，其中8例进行了牙弓模型的局部缓冲。对使用者进行了临床观察。为2例无法就位的牙托进行了重衬。对内村材料和防护牙托主体粘接面的抗剪切强度进行了测试及耐水试验。结果22纠患者中做防护牙托前有牙外伤史的为17例（77．3％）。在不同牙列阶段的使用者牙托的固位效果均良好。在使用过程中，有4例曾遭遇嘴部碰撞。但未造成软、硬组织损伤。防护牙托主体和内衬层粘接面的抗剪切强度较强，在37℃水中浸泡10天、20天、30天的试验组与对照组间的差异无显著性。重衬并不影响防护牙托的耐用性。结论重衬法的应用可以延长替牙期防护牙托的使用寿命，有利于在青少年中的推广使用。     

无牙下颌不同厚度黏骨膜能量传递率三维有限元分析

目的：分析在冲击载荷下无牙下颌不同厚度黏骨膜能量缓冲能力的大小。方法：利用无牙下颌标准模型建立三维有限元模型,计算不同黏骨膜厚度时能量传递率的大小。结果：随着黏骨膜厚度的增加（0～5．0mm）,黏骨膜能量传递率由100％降至22．55％。结论：黏骨膜的能量缓冲能力随着其厚度的增加而增大。     

防护牙托的材料和结构对其性能的影响

随着体育事业在我国的迅速发展,参与到各种体育运动中的青少年也不断增加。在通过运动强身健体的同时,不断增加的口颌系统外伤,尤其是牙外伤也成为非常棘手的问题。为了对这些运动外伤进行预防,防护牙托应运而生。但是不同材料、不同结构的防护牙托的效果也不尽相同,本文对此问题进行综述。     

全口义齿形态改变造成的语音失真

本文通过对声波图象的分析,研究了由于全口义齿形态的改变所造成的语音影响。材料和方法:在就诊的无牙颌病人中选择被检对象。选择标准(1)口齿清晰;(2)听力正常;(3)有一定语言水平;(4)能够配合。检查的内容包括:(1)被检者为戴用全口托牙时间较长,已习惯,并能依靠托牙作清晰的发音。此发音即作为对照。(2)不戴托牙的发音。(3)分别戴用不同形态托牙时的发音。托牙的不同形态包括上颌切牙的前后向移位和腭部基托厚度的改变。测试的方     

防护牙托在口颌系统运动损伤预防中的应用现状

随着体育运动事业在各国的发展，参与运动的人们越来越多，口颌系统运动损伤率也随之上升。这种高损伤率不仅意味着社会将付出高额的医疗经费，更严重损害了运动者的生活质量。本文综述了口颌系统运动损伤的现状、原因及防止措施．并通过对防护牙托的原理、种类及其效果的分析．进一步证实了推广使用防护牙托的重要意义。     

上颌无腭杆弓式托牙的制作与应用

<正> 上牙列肯氏Ⅰ类失牙是常见病、多发病。该类失牙修复是临床上一个难点,在一般技术条件下,多以托式托牙修复,存在着异物感强、语言咀嚼功能恢复不良、义齿容易损坏等缺陷,故以弓式托牙修复最为理想,但由于传统的弓式托牙钢架大,几何图形复杂,制作时需要高频铸造机,高性能熔铸材料,并要求熟练的制作技术。我院用国产电弧离心熔铸机制作传统弓式托牙时发现:钢架用钢量大,各     

牙托粉用量简易计算法

<正> 目前全国各医院口腔矫形科,在制作活动托牙充填塑胶时,仍然凭借各人的经验,估计使用牙托粉和造牙粉的用量。缺乏科学性。在充胶时,一旦发现牙托粉用量不足,则需要重新配制,费时费料;牙托粉用量过多,又造成不必要的浪费。有些书刊杂志上也曾发表过有关牙托粉、造牙粉充填用量计算法,基于计算方法复杂,多数技工人员不愿采用。我们通过临床数百次试验、计算,试订出简易计算法。一、重量计算法:制作活动托牙,在充胶之前必需制作蜡型,根据用蜡量的多少,可以推算出牙托粉的用量。     

全口托牙的远期效果——57例患者的回顾性研究

本文对57例要求重新制作全口托牙的患者,对其托牙配戴时使用情况的长期效果,进行了回顾性研究。从四个方面对患者的旧托牙进行评价:①患者对旧托牙的主观评价;②临床检查;③主观评价与客观检查的对比;④患者对新托牙的主观评价。调查中发现,患者对托牙的主观评价与临床客观检查结果不相符为主要特点。另外,基托反复折裂是患者要求重新制作托牙的原因之一,笔者认为在制作修复体之前,采取调磨牙尖,用冠、嵌体等恢复牙列的(牙合)曲线.或制作覆盖托牙,可以避免或减少这类修复体的折裂。     

运动牙套的缓冲及能量吸收特性分析

目的:利用冲击试验测试不同厚度和材料的运动牙套缓冲及能量吸收特性.方法 :按照运动牙套的厚度和材料,将牙套分为5 组,每组6个试件.采用钟摆与力锤结合装置(摆锤)对牙套及牙列模型施加冲击能量,通过改变摆锤的释放高度而改变冲击能量的大小.应用力传感器与激光测振仪分别与数据采集和信号分析仪连接,获得锤头的人射速度、反弹速度...     

Experimental comparative study of various mouthguards

Abstract— The aim of this study was to evaluate the mechanical and physical properties of several standard size commercially available mouthguards. For the purpose of objective testing, a special study model, which the various gum shield devices could be fitted onto, was developed to record tooth deflection caused by impact forces induced by a pendulum ram impact testing machine. The data measured on teeth provided with various gum shield devices were correlated with those of unprotected teeth; this enabled the individual cushioning effects of the respective devices and their specific force conduction to be evaluated. Using mouthguards considerably diminishes the deflection of the teeth subjected to stress in comparison with the row of unprotected teeth. In addition, force is transmitted to the adjacent teeth all the way to the distal regions of the row of teeth. The individual cushioning effects are directly correlated to the thickness of the material; the force distribution is determined by the rigidity of the gum shield device. The devices examined showed considerable differences with regard to force distribution and dimensioning. The study showed that this was due to the thickness of the materials, the manufacturing process and the composition of the materials of the devices examined. In comparison to laboratory-produced devices of similar material thickness, the devices that were designed to be fitted by the user achieved significantly poorer results as regards both cushioning properties and dissipation of exerted forces.     

Experimental comparative study of various mouthguards

The aim of this study was to evaluate the mechanical and physical properties of several standard size commercially available mouthguards. For the purpose of objective testing, a special study model, which the various gum shield devices could be fitted onto, was developed to record tooth deflection caused by impact forces induced by a pendulum ram impact testing machine. The data measured on teeth provided with various gum shield devices were correlated with those of unprotected teeth; this enabled the individual cushioning effects of the respective devices and their specific force conduction to be evaluated. Using mouthguards considerably diminishes the deflection of the teeth subjected to stress in comparison with the row of unprotected teeth. In addition, force is transmitted to the adjacent teeth all the way to the distal regions of the row of teeth. The individual cushioning effects are directly correlated to the thickness of the material; the force distribution is determined by the rigidity of the gum shield device. The devices examined showed considerable differences with regard to force distribution and dimensioning. The study showed that this was due to the thickness of the materials, the manufacturing process and the composition of the materials of the devices examined. In comparison to laboratory-produced devices of similar material thickness, the devices that were designed to be fitted by the user achieved significantly poorer results as regards both cushioning properties and dissipation of exerted forces.     

The ability of mouthguards to protect veneered teeth: A 3D finite element analysis

Background/Aims

Professional and amateur athletes might have veneer restorations. The aim of this study was to investigate the protective effect of mouthguards on veneered anterior restorations.

Methods

A nonlinear dynamic analysis was performed to simulate conditions during an impact with or without a custom-made mouthguard. Using a computer-aided design (CAD) software, a slice of a human maxilla was designed containing an upper right central incisor. The model was composed of mucosa, cortical bone, trabecular bone, periodontal ligament, dentin, enamel, and pulp tissue. The enamel was prepared (feather design), restored with an indirect veneer (1.0 mm thickness), and duplicated to simulate both conditions with or without a mouthguard (4 mm thickness). Both models were subdivided into finite elements using the computer-aided engineering (CAE) software. Frictionless contacts were used, and an impact was simulated in which a rigid sphere hit the model at 1 m s⁻¹. Fixation was defined at the base of the bone. The elastic modulus of the veneer was assessed by using five different restorative materials (resin composite, hybrid ceramic, zirconia-reinforced lithium silicate, lithium disilicate, and zirconia). Von Mises stress, minimal principal stress, and maximum principal stress (in MPa) were obtained and plotted for visual comparison.

Results

Von-Mises results showed higher stress concentrations in the veneer's cervical labial region for models without a mouthguard. Observing the quantitative results for each model, the highest compressive (709 MPa) and tensile (58 MPa) stresses occurred in the situation without a mouthguard with a zirconia veneer, while the lowest occurred in resin composite veneer with a mouthguard (8 and 5 MPa). The mouthguard was able to reduce the stresses in the tooth structure and it also reduced the risk of fracture in all conditions.

Conclusions

Mouthguards were beneficial in reducing the effects of dental trauma regardless of the restorative material used to manufacture the indirect veneer, since they act by dampening the generated stresses during the trauma event. Equal impact stresses on a mouthguard will lead to higher stresses in veneered teeth with more rigid restorative materials leading to a less protective effect.     

Are all mouthguards the same and safe to use? Part 2. The influence of anterior occlusion against a direct impact on maxillary incisors

Abstract –  The purpose of this study was to clarify the influence anterior occlusion, of mouthguards, has on protecting against a direct collision to the maxillary anterior teeth. In other words, the support mandibular dentition has when wearing a mouthguard. Two types of mouthguards were used for this study, one with an appropriate anterior occlusion or a mouthguard with positive anterior occlusion (MGAO+) and another which was a single-layer mouthguard lacking the same occlusion or a mouthguard with negative anterior occlusion (MGAO−) but with the same thickness on the buccal side. The instruments used for testing were a pendulum-type impact device with two interchangeable impact objects (a steel ball and a baseball), with a plastic jaw model having artificial teeth. Four testing conditions were observed: one with the jaw open without a mouthguard (Open NoMG), the second with the jaw clenching (loaded with 30 kg weight) without a mouthguard (Clench. NoMG), the third with the jaw clenching with MGAO− (Clench. MGAO−) and the last with the jaw clenching with MGAO+ (Clench. MGAO+). The results are as follows: both types of mouthguards showed the effects in reducing the distortion of the teeth. However, the effect was significantly obvious (steel ball = about 57% shock absorption ability, baseball = about 26%) in the mouthguard with anterior occlusion or support by lower dentition through mouthguard (Clench. MGAO+) than Clench. MGAO−. Thus, the influence of anterior occlusion of mouthguards or the support of mandibular dentition through wearing a mouthguard (MGAO+) is indispensable in reducing the impact force and tooth distortion. The results of this research should further contribute to the establishment of guidelines for safer mouthguards.     

Differences in the thickness of mouthguards fabricated from ethylene vinyl acetate copolymer sheets with differently arranged v‐shaped grooves: part 2 – effect of shape on the working model

The aim of this study was to evaluate the change in thickness of a working model mouthguard sheet due to different shape. Mouthguards were fabricated with ethylene vinyl acetate (EVA) sheets (4.0 mm thick) using a vacuum‐forming machine. Two shapes of the sheet were compared: normal sheet or v‐shaped groove 10–40 mm from the anterior end. Additionally, two shapes of the working model were compared; the basal plane was vertical to the tooth axis of the maxillary central incisor (condition A), and the occlusal plane was parallel to the basal plane (condition B). Sheets were heated until they sagged 15 mm below the clamp. Postmolding thickness was determined for the incisal portion (incisal edge and labial surface) and molar portion (cusp and buccal surface). Differences in the change in thickness due to the shape of the sheets and model were analyzed using two‐way anova followed by a Bonferroni's multiple comparison tests. The thickness of the mouthguard sheet with v‐shaped grooves was more than that of the normal sheet at all measuring points under condition A and condition B (P < 0.01). The thickness of condition B was less than that of condition A, there the incisal portion in the normal sheet and the incisal edge in the sheet with v‐shaped grooves (P < 0.01). The present results suggested that thickness after molding was secured by the use of the sheet with v‐shaped grooves. In particular, the model with the undercut on the labial surface may be clinically useful.     

Influence of pre-laminated material on shock absorption ability in specially designed mouthguard with hard insert and space

Purpose

We have developed a new type of laminated mouthguard, the Hard & Space mouthguard, which incorporates a hard material insert and a space to prevent contact between the mouthguard and the buccal surfaces of the teeth. The purpose of this study was to investigate the effect of this new design on shock absorption.

Methods

Three types of mouthguard (a conventional laminated EVA mouthguard and two 3-layer type “Hard & Space” mouthguards made of 1.8-mm or 3.0-mm thick pre-laminated material (Konbiplast) and EVA with a 1.0-mm space) were impacted. Shock absorption was measured by means of a pendulum type steel ball impact testing machine at impact distances of 10, 20, and 30 cm and a dental study model with strain gauges attached to the lingual surfaces and an accelerometer fixed to the maxilla.

Results

Distortion of the impacted tooth and acceleration of the model were significantly reduced by all types of mouthguard at all 3 impact distances. The effect of the mouthguard was remarkable in terms of tooth distortion: both thicknesses of Hard & Space mouthguard showed more than 90% shock absorption, compared with only approximately 55–78% with an EVA mouthguard. Furthermore, shock absorption with the thicker 3.0-mm Hard & Space mouthguard reached more than 95% at the highest impact power.

Conclusion

Within the limitations of this laboratory study, Hard & Space mouthguards showed significantly greater buffer capacity than a conventional EVA mouthguard in terms of tooth distortion at the 3 impact powers tested.     

Fabricating a better mouthguard. Part I: Factors influencing mouthguard thinning

Abstract –  There is some concern regarding the amount of material thinning that occurs during the fabrication of custom-fabricated mouthguards. It is unclear if this thinning is merely a consequence of the fabrication process or related to other factors such as jaw size. Thus, the purpose of this study was to evaluate the contribution that various dimensional characteristics of the dental arch and the height of the stone model would have on mouthguard thinning. Fifteen subjects participated in this investigation. Alginate impressions from each subject were used to produce three replicas of the maxillary dentition with only the height of the base varying amongst them. The total height of the three models were 20, 25, and 30 mm. A single mouthguard was produced using each of the stone models. The material thickness of the mouthguard was assessed at the labial and occlusal surfaces. Additionally, the dimensions of the stone models were documented. Pearson product moment correlation coefficients were calculated to determine the linear relationship between material thickness and (i) the height of the stone models, (ii) the arch length and (iii) the area covered by the stone model. Statistical tests performed using the mean thickness values collected from the incisors and canines revealed a high negative correlation between the height of the stone model and material thickness ( r  = −0.82). In addition, a low to moderate positive linear correlation was noted between arch length and occlusal thickness at the molars ( r  = 0.57) and between the area of the stone model with the occlusal thickness ( r  = 0.49). The results of the present study indicate that the height of the model used to fabricate custom mouthguards should be kept as low as possible but still allow for the production of a properly fitting mouthguard.     

Forces transmitted through EVA mouthguard materials of different types and thickness

Previous studies into sporting mouthguards have been mainly attitudinal or epidemiological. The aim of the present study was to build an impact rig to measure the impact absorbed by mouthguard materials of various thicknesses. The acceleration of the pendulum of the rig was measured and used to calculate the force transmitted to the materials.
Impact tests were also performed on three commercially available mouthguard materials. Tests showed that the force transmitted through mouthguard materials was inversely related to the material thickness.
Mouthguard construction techniques with ethylene vinyl acetate (EVA) plastics should be monitored to avoid occlusal thinning especially on the incisal edges. Thinning results in reduction in the protection offered by the mouthguard.     

EVA mouthguards: how thick should they be?

Abstract – A major consideration in the performance of mouthguards is their ability to absorb energy and reduce transmitted forces when impacted. This is especially important to participants in contact sports such as hockey or football. The thickness of mouthguard materials is directly related to energy absorption and inversely related to transmitted forces when impacted. However, wearer comfort is also an important factor in their use. Thicker mouthguards are not user‐friendly. While thickness of material over incisal edges and cusps of teeth is critical, just how thick should a mouthguard be and especially in these two areas? Transmitted forces through different thicknesses of the most commonly used mouthguard material, ethylene vinyl acetate (EVA) (Shore A Hardness of 80) were compared when impacted with identical forces which were capable of damaging the oro‐facial complex. The constant impact force used in the tests was produced by a pendulum and had an energy of 4.4 joules and a velocity of 3 meters per second. Improvements in energy absorption and reductions in transmitted forces were observed with increasing thickness. However, these improvements lessened when the mouthguard material thickness was greater than 4 mm. The results show that the optimal thickness for EVA mouthguard material with a Shore A Hardness of 80 is around 4 mm. Increased thickness, while improving performance marginally, results in less wearer comfort and acceptance.