This study was supported by the Minnesota Dental Research Center for Biomaterials and Biomechanics (MDRCBB).

Note: Three dental resin composites were studied using the glass cavities: Z100, Z250 and LS, as listed in Materials List. Among them, LS is known to be a low-shrinkage resin composite with a volumetric shrinkage of around 1.0%, much lower than those of Z250 and Z100 (~2% and ~2.5%, respectively)18-19. The equipment and other materials used in this study are also given in Materials List.
1. Model Cavity Preparation
<ol>
	<li>Cut a long cylindrical glass rod, 10 mm in diameter, into 10-mm long short rods using a low-speed diamond saw.</li>
	<li>Cut a Mesial-Occlusal-Distal (MOD) cavity (Figure&#160;1) measuring 3 mm (width) x&#160;2 mm (depth) in each specimen using an adapted low-speed diamond saw.</li>
	<li>Polish down each cylindrical specimen to create a flat surface perpendicular to the length of the cavity, with dimensions as shown in Figure&#160;1. The flat surface allows precise focusing and image calibration on the restoration. Henceforth, it will be called the observation surface.</li>
	<li>Prepare three specimens for each of the three materials tested: Z100, Z250 and LS; see&#160;Materials table.</li>
</ol>
2. Cavity Filling with Resin Composite
<ol>
	<li>Apply a thin layer of Ceramic Primer with a brush to silanize all the glass cavity surfaces. This allows bonding between the glass surfaces and the resin composites.</li>
	<li>After about 1 min, apply a thin layer of adhesive. Use LS Adhesive system for composite LS and Adper Single Bond Plus for composite Z100 and Z250.</li>
	<li>Cure the adhesive with a curing light and duration (10-20 sec) based on the manufacturer&#8217;s instructions (Materials table).</li>
	<li>Cover all the glass surfaces surrounding the restoration with black tape except the observation surface, as shown in Figure&#160;2. The purpose is to avoid the curing light reaching the resin composite through the surrounding transparent glass, which does not happen in real teeth.</li>
	<li>Bulk-fill the cavity with resin composite and scrape off any excess to flatten all the surfaces.</li>
</ol>
3. Surface Painting
<ol>
	<li>Spray a thin layer of white paint onto the observation surface, which now includes part of the resin composite.</li>
	<li>Sprinkle immediately some black fine charcoal powder onto the paint to create high-contrast speckles. The irregular shapes of the speckles will help the DIC software to identify them and track their movements.</li>
</ol>
4. Sample Mounting, Curing, and Photographing
<ol>
	<li>Referring to Figure&#160;2, place a specimen (E) into the holder (C) and tighten it with a screw (D). Then, place the whole unit at the end of a large horizontal beam.</li>
	<li>Secure a CCD camera and a yellow illumination LED light onto the same beam such that they face the observation surface.</li>
	<li>Using a stand with adjustable clamps, position the curing light such that its tip is about 1 mm above the sample.</li>
	<li>Take a picture of the specimen to provide the reference image prior to curing.</li>
	<li>Cure the resin composite for 20 sec.</li>
	<li>Take another picture at 5 min after curing.</li>
	<li>Place a calibration block at the same position as the observation surface and take a picture. The calibration block contains an array of circular dots with size and spacing precisely known.</li>
</ol>
5. Image Analysis with DIC Software
<ol>
	<li>Import the two pictures taken for each sample, one before and one after curing, into the DIC software.</li>
	<li>Calibrate the dimensions of the images and correct for image distortion using the image of the calibration block. .</li>
	<li>Define the area of interest within the observation surface for analysis.</li>
	<li>Define the size of the square subset windows as 64 x 64 pixels for the first iteration and 32 x 32 pixels for the second iteration20. Define the overlap as 50%.</li>
	<li>Correlate the image taken after curing with the reference image taken before curing to calculate the displacement and strain distributions.</li>
</ol>

<ol>
	<li>Palin, W. M., Fleming, G. J. P., Nathwani, H., Burke, F. J. T., Randall, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+cuspal+deflection+and+microleakage+of+maxillary+premolars+restored+with+novel+low-shrink+dental+composites.">In vitro cuspal deflection and microleakage of maxillary premolars restored with novel low-shrink dental composites.</a> Dental Materials. 21, 324-335 (2005).</li><li>Li, H., Li, J., Yun, X., Liu, X., Fok, A. S. -. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-destructive+examination+of+interfacial+debonding+using+acoustic+emission.">Non-destructive examination of interfacial debonding using acoustic emission.</a> Dental Materials. 27, 964-971 (2011).</li><li>Dijken, J. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+polymerization+shrinkage+kinetics+in+visible-light-cured+materials:+methods+development.">Determination of polymerization shrinkage kinetics in visible-light-cured materials: methods development.</a> Dental materials : official publication of the Academy of Dental Materials. 7, 281-287 (1991).</li><li>Gee, A. J., Davidson, C. L., Smith, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+modified+dilatometer+for+continuous+recording+of+volumetric+polymerization+shrinkage+of+composite+restorative+materials.">A modified dilatometer for continuous recording of volumetric polymerization shrinkage of composite restorative materials.</a> Journal of Dentistry. 9, 36-42 (1981).</li><li>Sakaguchi, R. L., Sasik, C. T., Bunczak, M. A., Douglas, W. 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B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+should+composite+be+layered+to+reduce+shrinkage+stress:+Incremental+or+bulk+filling.">How should composite be layered to reduce shrinkage stress: Incremental or bulk filling.</a> Dental Materials. 24, 1501-1505 (2008).</li><li>Weinmann, W., Thalacker, C., Guggenberger, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Siloranes+in+dental+composites.">Siloranes in dental composites.</a> Dental Materials. 21, 68-74 (2005).</li><li>Silikas, N., Eliades, G., Watts, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+intensity+effects+on+resin-composite+degree+of+conversion+and+shrinkage+strain.">Light intensity effects on resin-composite degree of conversion and shrinkage strain.</a> Dental Materials. 16, 292-296 (2000).</li><li>Yaofeng, S., Pang, J. H. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+of+optimal+subset+size+in+digital+image+correlation+of+speckle+pattern+images.">Study of optimal subset size in digital image correlation of speckle pattern images.</a> Optics and Lasers in Engineering. 45, 967-974 (2007).</li><li>Versluis, A., Tantbirojn, D., Pintado, M. R., DeLong, R., Douglas, W. 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The authors declare that they have no competing financial interests.

The use of glass cavities with the same shape and dimensions for shrinkage strain measurement was to minimize the variation in results due to differences in size, anatomy and material properties of natural human teeth. In addition, the fused silica glass used in this study has a similar Young&#8217;s modulus to enamel, making it a suitable simulant material for natural teeth as far as mechanical behavior is concerned21-22. Although in real tooth restorations, the resin composite is mostly bonded to dentin rath...

Resin composites are widely used in restorative dentistry because of their superior aesthetics and handling properties. However, despite being bonded to the tooth tissues, the polymerization shrinkage of resin composites remains a clinical concern as the shrinkage stress developed may cause debonding at the tooth-restoration interface1-2. Consequently, bacteria can invade and reside in the failed areas and result in secondary caries. On the other hand, if the restoration is well bonded to the tooth, the shrinkage stress may cause cracking in the tooth tissues. Either of these failures will jeopardize the service life of the dental restoration, which will be subjected to a large number of cycles of thermal and mechanical loading.

Measurement of polymerization shrinkage strain and stress has thus become indispensable in the development and evaluation of dental resin composites3-4. Various measuring techniques or methods have been developed5-11 with the main purpose of providing a simple setup for measuring the shrinkage behavior of resin composite materials reliably. While the measurements they provide may be sufficient for comparing the shrinkage behaviors of different materials, they do not help in the understanding of how and where shrinkage stress develops in actual restored teeth. Specifically, a question of great interest is how the cavity walls constrain the shrinkage of composites and leads to the creation of shrinkage stress in dental restorations12. Note that, to create shrinkage stress, part of the shrinkage strain of the resin composite has to be converted into tensile elastic strain. It would therefore be useful if this component of the strain in the restoration can be measured. Recently, the optical full-field strain-measuring technique, Digital Image Correlation (DIC), has been applied to the measurement of free shrinkage of resin composites as well as material flow in dental restorations13-15. The basic idea of DIC is to track and correlate visible patterns on the sample surface from sequential images taken during its deformation whereby the displacement and strain fields over that surface can be determined. Full-field measurement is one of the main advantages of the DIC method, which is especially useful in observing non-uniform deformation and strain patterns13. In this study, DIC was used to uncover the strain patterns in dental resin composite restorations, with the aim of understanding the development of shrinkage stress and identifying potential sites for debonding. This information is not directly available in the works cited above14-15, which only measured the displacement of the restoration due to polymerization shrinkage. The measurement was conducted using models that simulated teeth with mesial-occlusal-distal (MOD) tooth cavities as an attempt to replicate the stress or strain in real dental restorations. Although the use of real teeth is more anatomically representative, the disadvantage of that is the significant inherent differences among teeth in anatomy, mechanical properties, degree of hydration as well as invisible internal defects14 that result in large variations in the results. To overcome such a drawback, some studies have tried to standardize tooth samples by grouping them in terms of the buccal size16 or replaced the teeth altogether with models of a surrogate material17. For example, aluminum models which have a similar Young&#8217;s modulus to enamel (69 and 83 GPa, respectively) have been employed in shrinkage stress measurement, with the level of shrinkage stress being indicated by the cusp deflection17. In this study, silica glass models (cavities) were used instead because the material also has a similar Young&#8217;s modulus (63 GPa) to human enamel and, as it is transparent, any debonding or cracking in the specimens can be readily observed.

<table><tbody><tr><td>Dental composite Z100</td><td>3M ESPE</td><td>N362979</td><td>volume shrinkage ~ 2.5%, Young&#039;s modulus ~ 14 GPa</td></tr><tr><td>Dental composite Z250</td><td>3M ESPE</td><td>N326080</td><td>volume shrinkage ~ 2.0%, Young&#039;s modulus ~ 11 GPa</td></tr><tr><td>Dental composite LS</td><td>3M ESPE</td><td>N240313</td><td>volume shrinkage ~ 1%, Young&#039;s modulus ~ 10 GPa</td></tr><tr><td>Ceramic Primer</td><td>3M ESPE</td><td>N167818</td><td>Rely X</td></tr><tr><td>LS System Adhesive</td><td>3M ESPE</td><td>N391675</td><td>Adhesive for compoiste LS</td></tr><tr><td>Adper Single Bond Plus</td><td>3M ESPE</td><td>501757</td><td>Adhesive for compoiste Z100 and Z250</td></tr><tr><td>Glass rod&amp;nbsp;</td><td>Corning Inc.</td><td>Pyrex 7740 borosilicate</td><td></td></tr><tr><td>Curing light&amp;nbsp;</td><td>3M ESPE</td><td>Elipar S10</td><td></td></tr><tr><td>White paint&amp;nbsp;</td><td>Krylon Product Group</td><td></td><td>Indoor/Outdoor, Flat white</td></tr><tr><td>Charcoal powder&amp;nbsp;</td><td>Sigma Aldrich, Co.</td><td>BCBH6518V</td><td>Fluka activated charcoal</td></tr><tr><td>CCD camera&amp;nbsp;</td><td>Point Grey Research, Inc.</td><td>Point Grey Gras-20S4C-C</td><td></td></tr></tbody></table>

shrinkage of dental composite in simulated cavity measured with digital image correlation

Polymerization shrinkage of dental resin composites can lead to restoration debonding or cracked tooth tissues in composite-restored teeth. In order to understand where and how shrinkage strain and stress develop in such restored teeth, Digital Image Correlation (DIC) was used to provide a comprehensive view of the displacement and strain distributions within model restorations that had undergone polymerization shrinkage.
Specimens with model cavities were made of cylindrical glass rods with both diameter and length being 10 mm. The dimensions of the mesial-occlusal-distal (MOD) cavity prepared in each specimen measured 3 mm and 2 mm in width and depth, respectively. After filling the cavity with resin composite, the surface under observation was sprayed with first a thin layer of white paint and then fine black charcoal powder to create high-contrast speckles. Pictures of that surface were then taken before curing and 5 min after. Finally, the two pictures were correlated using DIC software to calculate the displacement and strain distributions.
The resin composite shrunk vertically towards the bottom of the cavity, with the top center portion of the restoration having the largest downward displacement. At the same time, it shrunk horizontally towards its vertical midline. Shrinkage of the composite stretched the material in the vicinity of the &#8220;tooth-restoration&#8221; interface, resulting in cuspal deflections and high tensile strains around the restoration. Material close to the cavity walls or floor had direct strains mostly in the directions perpendicular to the interfaces. Summation of the two direct strain components showed a relatively uniform distribution around the restoration and its magnitude equaled approximately to the volumetric shrinkage strain of the material.

Three specimens were tested for each material. After each test, the specimen was examined by eyes or, if necessary, using a microscope. No apparent debonding at the &#8220;tooth-restoration&#8221; interface or cracking was found.
The resolution of the pictures was 1,600 x 1,180 pixels with a pixel size of 5.8 mm. With a subset window size of 32 pixels, the spatial resolution of the displacement distributions was around 186 mm.
Figure 3 shows a typic...

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Shrinkage of Dental Composite in Simulated Cavity Measured with Digital Image Correlation

In order to understand the spatial development of polymerization shrinkage stress in dental resin-composite restorations, Digital Image Correlation was used to provide full-field displacement/strain measurement of restored model glass cavities by correlating images of the restoration taken before and after polymerization.

Polymerization shrinkage of dental resin composites can lead to restoration debonding or cracked tooth tissues in composite-restored teeth. In order to ...

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Research

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Medicine

13.4K Views.  University of Minnesota. In order to understand the spatial development of polymerization shrinkage stress in dental resin-composite restorations, Digital Image Correlation was used to provide full-field displacement/strain measurement of restored model glass cavities by correlating images of the restoration taken before and after polymerization.

Video: Shrinkage of Dental Composite in Simulated Cavity Measured with Digital Image Correlation

In situ Compressive Loading and Correlative Noninvasive Imaging of the Bone-periodontal Ligament-tooth Fibrous Joint

This study demonstrates a novel biomechanics testing protocol. The advantage of this protocol includes the use of an in situ loading device coupled to a high resolution X-ray microscope, thus enabling visualization of internal structural elements under simulated physiological loads and wet conditions. Experimental specimens will include intact bone-periodontal ligament (PDL)-tooth fibrous joints. Results will illustrate three important features of the protocol as they can be applied to organ level biomechanics: 1) reactionary force vs. displacement: tooth displacement within the alveolar socket and its reactionary response to loading, 2) three-dimensional (3D) spatial configuration and morphometrics: geometric relationship of the tooth with the alveolar socket, and 3) changes in readouts 1 and 2 due to a change in loading axis, i.e. from concentric to eccentric loads. Efficacy of the proposed protocol will be evaluated by coupling mechanical testing readouts to 3D morphometrics and overall biomechanics of the joint. In addition, this technique will emphasize on the need to equilibrate experimental conditions, specifically reactionary loads prior to acquiring tomograms of fibrous joints. It should be noted that the proposed protocol is limited to testing specimens under ex vivo conditions, and that use of contrast agents to visualize soft tissue mechanical response could lead to erroneous conclusions about tissue and organ-level biomechanics.

In situ Compressive Loading and Correlative Noninvasive Imaging of the Bone-periodontal Ligament-tooth Fibrous Joint

In this study, the use of an in situ loading device coupled with micro-X-ray computed tomography for fibrous joint biomechanics will be discussed. Experimental readouts identifiable with an overall change in joint biomechanics will include: 1) reactionary force vs. displacement, i.e. tooth displacement within the alveolar socket and its reactionary response to loading, 2) three-dimensional (3D) spatial configuration and morphometrics, i.e.&#160;geometric relationship of the tooth with the alveolar socket, and 3) changes in readouts 1 and 2 due to a change in loading axis, i.e. concentric or eccentric loads.

This study demonstrates a novel biomechanics testing protocol. The advantage of this protocol includes the use of an in situ loading device coupled to a ...

Bioengineering

Measuring the Complete-arch Distortion of an Optical Dental Impression

Digital workflows have actively been used to produce dental restorations or oral appliances since dentists started to make digital impressions by acquiring 3D images with an intraoral scanner. Because of the nature of scanning the oral cavity in the patient&#39;s mouth, the intraoral scanner is a handheld device with a small optical window, stitching together small data to complete the entire image. During the complete-arch impression procedure, a deformation of the impression body can occur and affect the fit of the restoration or appliance. In order to measure these distortions, a master specimen was designed and produced with a metal 3D printer. Designed reference geometries allow setting independent coordinate systems for each impression and measure x, y, and z displacements of the cylinder top circle center where the distortion of the impression can be evaluated. In order to evaluate the reliability of this method, the coordinate values of the cylinder are calculated and compared between the original computer-aided design (CAD) data and the reference data acquired with the industrial scanner. The coordinate differences between the two groups were mostly less than 50 &#181;m, but the deviations were high due to the tolerance of 3D printing in the z coordinates of the obliquely designed cylinder on the molar. However, since the printed model sets a new standard, it does not affect the results of the test evaluation. The reproducibility of the reference scanner is 11.0 &#177; 1.8 &#181;m. This test method can be used to identify and improve upon the intrinsic problems of an intraoral scanner or to establish a scanning strategy by measuring the degree of distortion at each part of the complete-arch digital impression.

Here, we present a protocol to measure the degree of distortion at each part of the compete-arch digital impression acquired from an intraoral scanner with 3D-printed metal phantom with standard geometries.

Digital workflows have actively been used to produce dental restorations or oral appliances since dentists started to make digital impressions by ...

Engineering

Accuracy in Dental Medicine, A New Way to Measure Trueness and Precision

Reference scanners are used in dental medicine to verify a lot of procedures. The main interest is to verify impression methods as they serve as a base for dental restorations. The current limitation of many reference scanners is the lack of accuracy scanning large objects like full dental arches, or the limited possibility to assess detailed tooth surfaces. A new reference scanner, based on focus variation scanning technique, was evaluated with regards to highest local and general accuracy. A specific scanning protocol was tested to scan original tooth surface from dental impressions. Also, different model materials were verified. The results showed a high scanning accuracy of the reference scanner with a mean deviation of 5.3 &#177; 1.1 &#181;m for trueness and 1.6 &#177; 0.6 &#181;m for precision in case of full arch scans. Current dental impression methods showed much higher deviations (trueness: 20.4 &#177; 2.2 &#181;m, precision: 12.5 &#177; 2.5 &#181;m) than the internal scanning accuracy of the reference scanner. Smaller objects like single tooth surface can be scanned with an even higher accuracy, enabling the system to assess erosive and abrasive tooth surface loss. The reference scanner can be used to measure differences for a lot of dental research fields. The different magnification levels combined with a high local and general accuracy can be used to assess changes of single teeth or restorations up to full arch changes.

Accuracy is a major demand in dental medicine. To verify accuracy, reference scanners are needed. This article presents a new reference scanner with an adjusted scanning method to acquire a broad variety of dental morphologies with high trueness and precision.

Reference scanners are used in dental medicine to verify a lot of procedures. The main interest is to verify impression methods as they serve as a base ...

Confocal Time Lapse Imaging as an Efficient Method for the Cytocompatibility Evaluation of Dental Composites

It is generally accepted that in vitro cell material interaction is a useful criterion in the evaluation of dental material biocompatibility. The objective of this study was to use 3D CLSM time lapse confocal imaging to assess the in vitro biocompatibility of dental composites. This method provides an accurate and sensitive indication of viable cell rate in contact with dental composite extracts. The ELS extra low shrinkage, a dental composite used for direct restoration, has been taken as example. In vitro assessment was performed on cultured primary human gingival fibroblast cells using Live/Dead staining. Images were obtained with the FV10i confocal biological inverted system and analyzed with the FV10-ASW 3.1 Software. Image analysis showed a very slight cytotoxicity in the presence of the tested composite after 5 hours of time lapse. A slight decrease of cell viability was shown in contact with the tested composite extracts compared to control cells. The findings highlighted the use of 3D CLSM time lapse imaging as a sensitive method to qualitatively and quantitatively evaluate the biocompatibility behavior of dental composites.

The most studied aspect of the biocompatibility of dental composites is their cytotoxicity 3D CLSM time lapse imaging combined with fluorescent signal quantification allows sensitive evaluation of the cell fate over time. Utilizing this method could be an efficient tool to assess the cytocompatibility of dental composites.

It is generally accepted that in vitro cell material interaction is a useful criterion in the evaluation of dental material biocompatibility. The ...

Ratiometric Imaging of Extracellular pH in Dental Biofilms

The pH in bacterial biofilms on teeth is of central importance for dental caries, a disease with a high worldwide prevalence. Nutrients and metabolites are not distributed evenly in dental biofilms. A complex interplay of sorption to and reaction with organic matter in the biofilm reduces the diffusion paths of solutes and creates steep gradients of reactive molecules, including organic acids, across the biofilm. Quantitative fluorescent microscopic methods, such as fluorescence life time imaging or pH ratiometry, can be employed to visualize pH in different microenvironments of dental biofilms. pH ratiometry exploits a pH-dependent shift in the fluorescent emission of pH-sensitive dyes. Calculation of the emission ratio at two different wavelengths allows determining local pH in microscopic images, irrespective of the concentration of the dye. Contrary to microelectrodes the technique allows monitoring both vertical and horizontal pH gradients in real-time without mechanically disturbing the biofilm. However, care must be taken to differentiate accurately between extra- and intracellular compartments of the biofilm. Here, the ratiometric dye, seminaphthorhodafluor-4F 5-(and-6) carboxylic acid (C-SNARF-4) is employed to monitor extracellular pH in in vivo grown dental biofilms of unknown species composition. Upon exposure to glucose the dye is up-concentrated inside all bacterial cells in the biofilms; it is thus used both as a universal bacterial stain and as a marker of extracellular pH. After confocal microscopic image acquisition, the bacterial biomass is removed from all pictures using digital image analysis software, which permits to exclusively calculate extracellular pH. pH ratiometry with the ratiometric dye is well-suited to study extracellular pH in thin biofilms of up to 75 &#181;m thickness, but is limited to the pH range between 4.5 and 7.0.

A pH-sensitive ratiometric dye is used in combination with confocal laser scanning microscopy and digital image analysis to monitor extracellular pH in dental biofilms in real-time.

The pH in bacterial biofilms on teeth is of central importance for dental caries, a disease with a high worldwide prevalence. Nutrients and metabolites ...

Immunology and Infection

Roughness Impact of Piezoelectric Dental Scaler on Two Distinct Flowable Composite Filling Materials

Dental ultrasonic scalers are commonly employed in periodontal treatment; however, their ability to roughen tooth surfaces is a worry since roughness may increase plaque production, a key cause of periodontal disease. This research studied the influence of a piezoelectric ultrasonic scaler on the roughness of two distinct flowable composite filling materials. To do this, 10 disc-shaped samples were generated from each of the two flowable composite materials. After standardized polishing, samples were submerged in water for 24 h before the first surface examination using electron microscopy and profilometry. The ultrasonic scaler was applied to a specified location of each sample for 60 s under water cooling and regulated force. Post-scaler surface parameters were again examined. Following the application of the scaler, both composite materials exhibited a notable increase in surface roughness, as determined by profilometry (p &lt; 0.01). Additionally, the observed surface roughness was also qualitatively visualized with scanning electron microscopy. While initial roughness levels were comparable across the two composites (p = 0.143) after scaler application, no substantial discrepancy in surface texture was noticed between them (p = 0.684). The use of a high-power piezoelectric ultrasonic scaler on routinely used flowable composite restorations might generate considerable surface roughness, possibly leading to increased plaque accumulation. Nevertheless, it might be postulated that nanohybrid flowable composite materials having conventional monomer ingredients may demonstrate comparable surface alterations within the limitations of this experiment.

This methodology allows applying a dental appliance on any specimen at any angle with standardized force and stability. This approach might be extensively used in health sciences to standardize the impacts of dental equipment with hand-holding elements such as micromotors, turbines, and ultrasonic scalers on varied surfaces.

Dental ultrasonic scalers are commonly employed in periodontal treatment; however, their ability to roughen tooth surfaces is a worry since roughness may ...

Behavior

3D Imaging of PDL Collagen Fibers during Orthodontic Tooth Movement in Mandibular Murine Model

Orthodontic tooth movement is a complex biological process of altered soft and hard tissue remodeling as a result of external forces. In order to understand these complex remodeling processes, it is critical to study the tooth and periodontal tissues within their 3D context and therefore minimize any sectioning and tissue artefacts. Mouse models are often utilized in developmental and structural biology, as well as in biomechanics due to their small size, high metabolic rate, genetics and ease of handling. In principle this also makes them excellent models for dental related studies. However, a major impediment is their small tooth size, the molars in particular. This paper is aimed at providing a step by step protocol for generating orthodontic tooth movement and two methods for 3D imaging of the periodontal ligament fibrous component of a mouse mandibular molar. The first method presented is based on a micro-CT setup enabling phase enhancement&#160;imaging of fresh collagen tissues. The second method is a bone clearing method using ethyl cinnamate that enables imaging through the bone without sectioning and preserves endogenous fluorescence. Combining this clearing method with reporter mice like Flk1-Cre;TdTomato provided a first of its kind opportunity to image the 3D vasculature in the PDL and alveolar bone.

We present a protocol for generating orthodontic tooth movement in mice and methods for 3D visualization of the collagen fibers and blood vessels of periodontal ligament without sectioning.

Orthodontic tooth movement is a complex biological process of altered soft and hard tissue remodeling as a result of external forces. In order to ...

Detection and Removal of Tooth-Colored Composite Resin Using the Fluorescence-Aided Identification Technique

The detection and removal of tooth-colored filling materials is a major challenge for every dentist. The Fluorescence-aided Identification Technique (FIT) is a noninvasive tool to facilitate the distinction of composite resin material from sound tooth substance. Compared to conventional illumination, FIT is a very accurate, reliable, and fast diagnostic method. When composite resin is illuminated with a wavelength of approximately 398 &plusmn; 5 nm, certain fluorescent components make the composite resin appear brighter than the tooth structure. Any fluorescence-inducing light source with the appropriate wavelength can be used for this method. Optimally, this technique is used without additional natural or artificial lighting. The application of FIT can be used for diagnostic purposes, for example, dental charts, and additionally for the complete and minimally invasive removal of composite resin restorations, bracket debonding, and trauma splint removal. The assessment of volumetric changes after composite removal can be provided by overlapping pre- and postoperative scans and subsequent calculation using suitable software.

The Fluorescence-aided Identification Technique is a practicable, fast, and reliable approach for the differentiation of composite resin restorations from tooth substance, and facilitates the minimally invasive and complete removal of composite resin restorations and composite bonded trauma splints.

The detection and removal of tooth-colored filling materials is a major challenge for every dentist. The Fluorescence-aided Identification Technique (FIT) ...

Precision of In Vivo Quantitative Tooth Wear Measurement Using Intra-Oral Scans

Quantitative wear measurement is of increasing interest for measuring tooth wear progression. However, most research on quantitative wear measurement has focused on simulated wear or scanned gypsum casts. A 3D Wear Analysis (3DWA) protocol has been developed that analyzes tooth wear in vivo through intra-oral scanners available to dental clinicians. This study investigated the precision of the 3DWA protocol for measuring wear through maximum height loss (mm) and volume change (mm3). Observational prospective wear data from 55 patients were analyzed after 0-1-, 0-3-, and 0-5-year intervals to determine rates of wear, and convenience samples were chosen to test the protocol&#39;s precision on dentitions scanned twice in one sitting and its intra- and inter-rater precision on scans with 0-3- and 0-5-year intervals. Scans were made using intra-oral scanners (IOS) and superimposed using 3D measurement software. T-tests were performed to determine the structural and random error, and trimmed ranges were calculated to interpret the error. For protocol precision, the mean difference was 0.015 mm (-0.002; 0.032, p = 0.076) for height and -0.111 mm3 (-0.250; 0.023, p = 0.101) for volume. The duplicate measurement error was 0.062 mm for height and 0.268 mm3 for volume. The height measurements were precise enough to measure wear after intervals of 0-3 or 0-5 years; however, volume measurements were susceptible to procedural error and operator sensitivity. The 3DWA protocol is precise enough to adequately measure tooth height loss after intervals of a minimum of 3 years or in patients with severe wear progression, but it is not suited to measuring volumetric changes.

Precision of In Vivo Quantitative Tooth Wear Measurement Using Intra-Oral Scans

Quantitative wear measurement is a method of increasing importance in measuring tooth wear progression. We here describe a protocol, its precision, and its intra/inter-rater precision for the acquisition and superimposition of repeated in vivo scanned dentitions in patients with moderate to severe wear, reporting on both height and volume measurements.

Quantitative wear measurement is of increasing interest for measuring tooth wear progression. However, most research on quantitative wear measurement has ...

Semi-Automated Planimetric Quantification of Dental Plaque Using an Intraoral Fluorescence Camera

Dental plaque accumulation is quantified using clinical indices or, otherwise, the planimetric plaque index (PPI),&#160;which measures the relative area of a tooth that is covered by plaque deposits. Compared to clinical indices, the PPI has a higher discriminatory power, but traditional planimetry is a time-consuming analysis, as the plaque-covered and clean tooth areas have to be determined manually for each image using image-processing software. Here, we present a method for the semi-automated planimetric quantification of dental plaque, which allows for the rapid processing of up to 1,000 images simultaneously. The method exploits the enhanced contrast between disclosed plaque, sound tooth surfaces, and soft tissues in fluorescence images acquired with an intraoral camera. Careful execution of the clinical procedures and accurate image acquisition are crucial steps for the successful semi-automated identification of the plaque-covered areas. The method is suitable for planimetry on sound facial and oral tooth surfaces, on most composite resin restorations, and on teeth with orthodontic brackets, but not on metallic restorations. Compared to traditional PPI recordings, semi-automated planimetry considerably reduces the amount of time spent on the analysis, as well as the subjective human input, thus increasing the reproducibility of planimetric measurements.

This study presents a semi-automated digital image analysis procedure for the planimetric quantification of disclosed dental plaque based on images acquired with an intraoral fluorescence camera. The method allows for the rapid and reliable quantification of dental plaque in the research environment.

Dental plaque accumulation is quantified using clinical indices or, otherwise, the planimetric plaque index (PPI),&#160;which measures the relative area ...

Shrinkage of Dental Composite in Simulated Cavity Measured with Digital Image Correlation

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In situ Compressive Loading and Correlative Noninvasive Imaging of the Bone-periodontal Ligament-tooth Fibrous Joint

Measuring the Complete-arch Distortion of an Optical Dental Impression

Accuracy in Dental Medicine, A New Way to Measure Trueness and Precision

Confocal Time Lapse Imaging as an Efficient Method for the Cytocompatibility Evaluation of Dental Composites

Ratiometric Imaging of Extracellular pH in Dental Biofilms

Roughness Impact of Piezoelectric Dental Scaler on Two Distinct Flowable Composite Filling Materials

3D Imaging of PDL Collagen Fibers during Orthodontic Tooth Movement in Mandibular Murine Model

Detection and Removal of Tooth-Colored Composite Resin Using the Fluorescence-Aided Identification Technique

Precision of In Vivo Quantitative Tooth Wear Measurement Using Intra-Oral Scans

Semi-Automated Planimetric Quantification of Dental Plaque Using an Intraoral Fluorescence Camera