Measuring microhardness of laser exposed tooth surface

In principle it is possible to homogenize the enamel surface by melting structural elements with the continuous wave CO2 laser. Using the precision instrument NEOPHOT 2 (Carl Zeiss JENA) the microhardness of extracted laserexposed premolares were tested so as to clarify the functional strain capasity and the mechanical characteristics of laserexposed regions of enamel surfaces. The proven higher hardness in the centre of the laserinduced fusing zones (in comparison with adjacent enamel) objectify an attainable refining of the enamel surface that probably causes an increase in the caries-preventive resistance.     

Reliability of a 3D surface laser scanner for orthodontic applications.

A device for recreating three-dimensional (3D) objects on a computer is the surface laser scanner. By triangulating distances between the reflecting laser beam and the scanned surface, the surface laser scanner can detect not only an object's length and width but also its depth. The scanner's ease of use has opened various possibilities in laboratory research and clinical investigation. We assessed the reliability of generating 3D object reconstructions using the Minolta Vivid700 3D surface laser scanner (Minolta USA, Ramsey, NJ). Accuracy and reproducibility were tested on a geometrical calibrated cylinder, a dental study model, and a plaster facial model. Tests were conducted at varying distances between the object and the scanner. It was found that (1) in the calibrated cylinder tests, spatial distance measurement was accurate to 0.5 mm (+/- 0.1 mm) in the vertical dimension and 0.3 mm (+/- 0.3 mm) in the horizontal dimension; (2) in the study model test, molar width was accurate to 0.2 mm (+/- 0.1 mm, P >.05), and palatal vault depth could be measured to 0.7 mm (+/- 0.2 mm, P > 0.05); and (3) for the facial model, an accuracy of 1.9 +/- 0.8 mm was obtained. The findings suggest that the surface laser scanner has great research potential because of its accuracy and ease of use. Treatment changes, growth, surgical simulations, and many other orthodontic applications can be approached 3-dimensionally with this device.     

基于激光扫描的面部软组织三维模型准确性评估

目的 评估基于激光扫描所建立的面部软组织三维模型和软组织测量标志点的准确性.方法 在一受试者的面部进行标志点标记,直接测量各标记点间的距离,之后使用Minolta Vivid 9i三维激光扫描仪进行面部扫描合成三维图像后,应用软件测量标记点间距离,对比两种方法的差异.另选择10名成年女性,在激光扫描前预先标记左右耳屏中点为固定标志点,再选取面部其余测量标志点22个.直接测量耳屏点与测量标志点间的距离,之后测量三维成像后耳屏点与测量标志点间距离,对比两者的差异.所有数据进行配对t检验.结果 基于激光扫描所建立的面部软组织三维模型的准确度为（0.72±0.51）mm.其中水平向、垂直向和前后向的准确度分别为（0.70±0.41）mm、（0.73±0.47）mm和（0.72±0.54）mm.59％的软组织测量标志点具有较高的准确性.结论 基于激光扫描的面部软组织三维模型具有较好的准确性.     

The influence of PDL principal fibers in a 3-dimensional analysis of orthodontic tooth movement.

The effects of mechanical loads on the tooth-alveolus complex are of particular concern in orthodontics. The concepts of center of resistance (CRes) and center of rotation (CRot) are used to characterize tooth responses to orthodontic loads. The mechanical environment (stresses and strains) associated with orthodontic tooth movement is a unique model in bone adaptation physiology. Numerous finite element models of varying complexity have been developed to calculate tooth movements and stress distributions within the alveolar bone and the periodontal ligament (PDL). In general, the PDL has been idealized as a homogeneous isotropic material. For this project, a 3-dimensional tooth/PDL/mandible/finite element model was developed in which, for the first time in such an analysis, the PDL's principal-fiber structure was also incorporated. Parametric analyses showed that the fiber orientation and the mechanical properties do not exert much influence on the locations of the CRes and the CRot and on the stress patterns within the bone and the PDL matrix. However, the absence of principal fibers produces not only different stress magnitudes, but also differences in stress patterns. Furthermore, the no-fiber-associated CRes and CRot are considerably separated from the cluster of fiber-influenced centers. It was concluded that it may be more realistic to incorporate "generic" principal fibers into finite element models than not to include them at all, despite the lack of reliable information about fibers.     

三维激光扫描测量外鼻形态的可靠性研究

目的 :验证三维激光扫描测量系统测量外鼻形态的技术可靠性。方法 :取 11个石膏鼻模型为研究对象 ,通过三维激光扫描测量系统获取外鼻的三维数字化模型 ,利用相关测量软件对其进行形态测量 ,并以手工测量得到的测量结果为对照组进行统计学分析。结果 :激光三维扫描测量结果与手工测量结果高度相关。结论 :三维激光扫描测量系统进行鼻形态测量结果完全可靠 ,测量误差符合人体测量学的要求。     

基于激光扫描的面部软组织三维模型的重叠和分析方法的建立

目的：确定同一个体正畸治疗前后面部软组织三维模型的重叠方法,并建立一个可以客观评估面部软组织形态和大小改变的分析方法。方法对一受试者进行6次面部激光扫描,分别为受试者额头区域预先标记一矩形标记物,并在面部预先标记7个标志点。口内配戴一前庭盾活动矫治器。去除标记物,保留标志点,口内不配戴前庭盾。去除标记物,保留标志点,口内配戴前庭盾。去除标记物和标志点,口内不配戴前庭盾。去除标记物和标志点,口内配戴前庭盾。使用Rapidform XOV软件进行点重叠和额部区域重叠。再对重叠图像进行截面分析。结果3次点重叠的结果具有可重复性,且与区域重叠相比,点重叠更好的反映了戴入前庭盾后面部的变化。图像总体对比法和截面分析法分别定性和定量的显示了面部软组织的变化。结论建议使用点重叠的方法对比正畸治疗前后面部软组织的变化。图像总体对比法和截面分析法各具特点,均可反映面部的变化。     

Defining a natural tooth color space based on a 3-dimensional shade system

STATEMENT OF PROBLEM: The natural tooth color space reported by a manufacturer may not represent the comprehensive spectrum of natural teeth for all population groups. PURPOSE: The purpose of this study was to define a natural tooth color space within the Greater Buffalo, New York population and to compare that to the color space determined by a manufacturer. MATERIAL AND METHODS: Nine hundred and thirty-three maxillary central incisors (501 patients) were measured with a shade-taking device (Vita Easyshade). For each tooth, L*, a*, b* values, chroma, hue, and the closest shade (Vita 3D-Master) were recorded. A linear regression analysis was performed to determine how well the manufacturer's values predict actual values for L*, a*, and b*. Color differences (DeltaE*) between the Buffalo population and the closest shade were also calculated. A 1-sample t test was used to determine whether the color differences seen in the sample were statistically different from the perceptibility threshold, DeltaE*=3.7 (alpha=.05). RESULTS: All 3 attributes of the Buffalo population displayed a broader range than those from the shade guide. However, the regression analysis revealed a significantly positive relationship between the L*, a*, and b* values of the 2 methods (P<.001). The 1-sample t test revealed a significant DeltaE* (mean DeltaE*=6.15) difference from the perceptibility threshold of DeltaE*=3.7 (P<.001). CONCLUSIONS: Color differences between the Buffalo population and the shade guide were frequently above published perceptibility thresholds, but within the range of acceptability. The Buffalo population tooth color space encompassed the manufacturer's color space.     

基于激光扫描的面部软组织三维模型三种重叠方法的对比

目的 对比面部软组织三维模型重叠的3种重叠方法.方法 选择22例正畸治疗前后的成人患者,在正畸治疗前后拍摄头颅侧位片并同期进行面部软组织激光扫描.测量鼻尖点(Pn)、鼻下点(Sn)、上唇缘点(Ls)、下唇缘点(Li)、下唇凹点(B')和颏前点(Pos)在头颅侧位片上的变化.使用Rapidform XOV和XOR软件进行点重叠、额部区域重叠和软件自动重叠,以额点、软组织鼻根点和鼻尖点确定正中矢状向平面,分别测量不同方法重叠后Pn、Sn、Ls、Li、B'和Pos点的变化量.并以头颅侧位片的结果为标准,对比3种重叠方法的差异.进而,对比使用3种重叠方法后面部10个区域最大变化值的差异.结果 使用头颅测量片测得的Pn、Sn、Ls、Li、B'和Pos点正畸治疗前后的变化值,与软组织三维模型的测量值间无显著差异.点重叠、区域重叠和自动重叠后面部10个区域的最大变化值也均无显著差异.结论 对于成人而言,点重叠、额部区域重叠和软件自动重叠这3种软组织重叠方法没有显著差异.     

A three-dimensional evaluation of a laser scanner and a touch-probe scanner

STATEMENT OF PROBLEM: The fit of a dental restoration depends on quality throughout the entire manufacturing process. There is difficulty in assessing the surface topography of an object with a complex form, such as teeth, since there is no exact reference form. PURPOSE: The purpose of this study was to determine the repeatability and relative accuracy of 2 dental surface digitization devices. A computer-aided design (CAD) technique was used for evaluation to calculate and present the deviations 3-dimensionally. MATERIAL AND METHODS: Ten dies of teeth prepared for complete crowns were fabricated in presintered yttria-stabilized tetragonal zirconia (Y-TZP). The surfaces were digitized 3 times each with an optical or mechanical digitizer. The number of points in the point clouds from each reading were calculated and used as the CAD reference model (CRM). Alignments were performed by registration software that works by minimizing a distance criterion. In color-difference maps, the distribution of the discrepancies between the surfaces in the CRM and the 3-dimensional surface models was identified and located. RESULTS: The repeatability of both scanners was within 10 microm, based on SD and absolute mean values. The qualitative evaluation resulted in an even distribution of the deviations in the optical digitizer, whereas the dominating part of the surfaces in the mechanical digitizer showed no deviations. The relative accuracy of the 2 surface digitization devices was within +/- 6 microm, based on median values. CONCLUSION: The repeatability of the optical digitizer was comparable with the mechanical digitization device, and the relative accuracy was similar.     

Preliminary 3-dimensional surface texture measurement and early loading results with a microtextured implant surface

PURPOSE: This investigation was conducted to obtain preliminary roughness data on a microtextured implant surface and to determine its ability to sustain a 1-stage surgical procedure and early full occlusal loading of single-tooth restorations in humans. MATERIALS AND METHODS: Three-dimensional (3D) vertical scanning interferometry was conducted on samples of the test surface (MTX) and 2 control surfaces (Osseotite and sandblasted/acid-etched [SLA]). Test implants were also placed in vivo, restored with fully occluding single-tooth restorations (n = 27) after 2 months of nonsubmerged healing, and clinically monitored for 48 months of follow-up. RESULTS: Microtexture was relatively uniform on the test surface and more random and irregular on the control surfaces. MTX and Osseotite were similar in some roughness parameters, but the MTX surface had a greater number of micropits that were spaced closer together (Stylus Y lambda q) and with higher slope values (Stylus Y delta q). Cumulative life table results were 100% for all MTX implants placed in maxillary and mandibular jaw locations, and no discernible marginal bone changes were observed. Overall implant success was 100% after 4 years of clinical functioning. DISCUSSION: The findings of this study appear promising but should be considered preliminary, because of the limitations in the number of locations measured on each product sample and the small number of implants clinically studied. CONCLUSION: Within the scope of the present study, MTX implants exhibited a uniform micropitted surface, as well as 100% survival and 100% clinical success after nonsubmerged placement, early loading with single-tooth restorations at 2 months, and 48 months of clinical functioning. (More than 50 references.)     

Reliability of measuring facial morphology with a 3-dimensional laser scanning system.

INTRODUCTION: The purpose of this prospective clinical trial was to evaluate the reliability of a 3-dimensional facial scanning technique for the measurement of facial morphology. METHODS: A field study was conducted in 2 comprehensive schools in the South Wales region of the United Kingdom. Forty subjects, mean age 11 years 3 months, were analyzed for soft tissue changes at baseline (T1), within 3 minutes (T2), and 3 days later (T3) by using 2 commercially available Minolta Vivid 900 (Osaka, Japan) laser-scanning devices assembled as a stereo pair. Left and right images were merged to form the whole face, and these images were superimposed to assess the errors at T1 and T2, and T1 and T3. RESULTS: The results showed that premerged left and right mean shell deviations were 0.38 +/- 0.14 mm for scans at T1, 0.31 +/- 0.09 mm at T2, and 0.34 +/- 0.12 mm at T3. The mean differences of the merged composite face were 0.31 +/- 0.08 mm between T1 and T2, and 0.40 +/- 0.11 mm between T1 and T3. Paired t tests showed no significant difference between these groups (P > .05). Shell deviation facial maps of the merged scans showed that 90% of the created composite facial scans were within an error of 0.85 mm. CONCLUSIONS: Capturing the soft tissue morphology of the face with this technique is clinically reproducible within 3 minutes and 3 days of the initial records.     

三维点激光扫描仪的扫描可靠性研究

目的全面评价Roland LPX-1200三维点激光扫描仪的扫描可靠性，为临床研究提供参考。方法规则加工的仿牙齿样模具，使用Roland LPX 1200点激光扫描仪获得其数字化模型，通过比较不同起始位置的扫描结果，评价扫描仪的扫描可重复性；选择长，宽，高三维方向上65项测量项目，比较数字化模型测量与实物测量之间的差异，评价其扫描准确性。结果连续扫描以及改变扫描初始位置引起的扫描随机误差在0．02mm以内；数字化模型测量与实物测量之间的差值均数为0．0012±0．05mm，P〈0．05。结论扫描仪具有良好的可靠性，能满足正畸临床对模型测量精度的要求。     

Measuring tooth mobility with a no-contact vibration device

Background and Objective:  Mechanical parameters obtained from the frequency response at tooth vibration informs of various periodontal tissue conditions. An electromagnetic vibration device was investigated for measuring tooth mobility using mechanical parameters obtained from the frequency response characteristics of an experimental tooth model. This electromagnetic vibration device was able to assess the overall condition of periodontal tissue associated with the alteration of each parameter. In this study, reliability and effects of bottom thicknesses of simulated periodontal ligament relative to mechanical parameters were analysed.
Material and Methods:  Measurement of tooth vibration was performed by an electromagnetic vibration device on experimental tooth models with different bottom thicknesses of simulated periodontal ligament. Using an electromagnetic vibration device, the mechanical parameters resonant frequency, elastic modulus and coefficient of viscosity were calculated from the frequency response characteristics derived from tooth vibration by an electromagnetic force. Variation of those parameters was investigated under four different experimental conditions and the implications of the results were discussed.
Results:  An electromagnetic vibration device clearly detected three mechanical parameters in all experimental conditions. The resonant frequency and the elastic modulus decreased with increasing bottom thickness. However, no significant difference in the coefficient of viscosity was observed among the experimental conditions.
Conclusion:  Assessment of tooth mobility using mechanical parameters of an electromagnetic vibration device reproduced fine details of various simulated periodontal ligament conditions. Variation in the parameters resonant frequency, elastic modulus and coefficient of viscosity might be useful in evaluating changes of components in periodontal tissues.     

低强度激光促进正畸牙移动的Meta分析和系统评价

目的：评价低强度激光治疗（low?level laser therapy ,LLLT）促进正畸牙移动的有效性及相关风险。方法依据Cochrane Handbook的规范化要求,检索1980年-2014年Medline、PubMed等数据库,运用Review Manager 5.1软件进行Meta分析。结果共纳入6个国家6篇随机对照试验,3篇不完全随机对照试验,211名患者。偏倚风险评价显示5个研究为中度偏倚风险,4个研究为高度偏倚风险。Meta分析结果显示：与对照组相比,LLLT组治疗后7 d,正畸牙移动速度显著增加（MD=0.19,95%CI 0.02?0.37,P=0.03）,该优势持续到治疗后2个月（MD=1.08,95%CI 0.16?2.01,P=0.02）;相对于高能量密度（20或25 J/cm2）的LLLT治疗,低能量密度（2.5,5或8 J/cm2）的LLLT治疗更为有效。结论低能量密度（2.5、5或8 J/cm2）的LLLT能有效促进正畸牙移动,但还需要更多临床随机对照试验支撑。     

Effects of two wattages of low-level laser therapy on orthodontic tooth movement

IntroductionMixed outcomes have been found in animal and clinical studies with regard to the use of low-level laser therapy (LLLT) as a modality to accelerate orthodontic tooth movement (OTM). One major reason for the variable findings is the different methodologies and protocols for laser therapy use.ObjectiveThe aim of this study was to determine whether orthodontically moved molars exposed to two different wattages at the same energy density of LLLT exhibited differences in the amount of tooth movement and molecular and histological changes in the adjacent periodontal areas.MethodsAn orthodontic force was applied to rat upper first molars exposed to 500 mW (EX-500) and 1000 mW (EX-1000) of laser application, with a control group (CT) with no laser application. Gene expression in the periodontal ligament (PDL) and histology of the palatal gingiva of the molars were analyzed.ResultsThere was a statistically significant difference for OTM between EX-500 but not between EX-1000 and CT groups. RANKL and MMP-13 expression levels in the PDL of orthodontically moved molars, however, were increased significantly in laser-exposed groups compared to CT. Early signs of dysplasia were observed in over half of the animals in the EX-1000 group.ConclusionsOur results provide evidence for molecular changes and the potential dysplastic effects of laser on the surrounding soft tissues. Further studies are needed to better identify an optimum laser protocol to maximize the desired effect.