OVERVIEW - Kravitz Orthodontics

1 337 VOLUME XLVIII NUMBER 6 2014 JCO, technology, orthodontists can more accu-rately and efficiently fabricate clear aligners, cus-tom braces, indirect-bonding trays, and laboratory appliances without the unpleasant experience of conventional advent of intraoral digital scanners coin-cided with the development of computer-aided design and manufacturing (CAD/CAM) technol-ogy and the 1984 introduction of chairside eco-nomical restoration of esthetic ceramics (CEREC).1 In 2001, Cadent introduced the OrthoCAD* sys-tem for the production of 3D digital models, vir-The replacement of alginate and polyvinyl silox-ane (PVS) impressions with intraoral digital scanners represents a paradigm shift in orthodon-tics. First introduced as an outsourced technology for storage of three-dimensional electronic study models, the digital scanner has evolved into an in-office tool with a variety of applications.

2 Using NEAL D. Kravitz , DMD, MSCHRISTIAN GROTH, DDS, MSPERRY E. JONES, DDS, MAGDJOHN W. GRAHAM, DDS, MDW. RONALD REDMOND, DDS, MSIntraoral Digital ScannersOVERVIEW(Editor s Note: In this regular column, JCO pro-vides an OVERVIEW of a clinical topic of interest to orthodontists. Contributions and suggestions for future subjects are welcome.)Dr. Graham Dr. Redmond Dr. Jones Dr. Groth Dr. Kravitz Dr. Kravitz is a Contributing Editor of the Journal of Clinical Orthodontics ; an adjunct faculty member, Department of Orthodontics , Washington Hospital Center, Washington, DC; and in the private practice of Orthodontics at 25055 Riding Plaza, Suite 110, South Riding, VA 20152; e-mail: Dr. Groth is in the private practice of Orthodontics in Birmingham, MI. Dr.

3 Jones is an Associate Professor, Department of Oral and Maxillofacial Surgery and Department of General Practice, and Director, Department of Continuing Education, School of Dentistry, Virginia Commonwealth University, Richmond, VA. Dr. Graham is a Contributing Editor of the Journal of Clinical Orthodontics and an Adjunct Associate Professor for Clinical Orthodontics , Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, and Department of Orthodontics , University of Rochester School of Medicine and Dentistry, Rochester, NY; he is in the private practice of Orthodontics in Litchfield Park, AZ, and Salt Lake City. Dr. Redmond is Technology Editor of the Journal of Clinical Orthodontics and in the private practice of Orthodontics in Laguna Niguel, CA.

4 *Trademark of Align Technology, San Jose, CA; II CorreCtIon sImplIfIedIntroducing PowerScope an innovative appliance delivering easy Class II correction like you ve never seen before. Quick wire-to-wire installation Fixed one-piece design requires no lab setup or patient compliance Internal NiTi spring delivers 260 grams of force for continuous activation during treatment Patient-friendly design maximizes comfortTo learn more, talk to your American Orthodontics salesrepresentative or visit 2014 AmericAn Orthodontics cOrpOrAtiOn | +1 920 457 5051 | 2014 JCO, Inc. May not be distributed without permission. 2014 OVERVIEW tual setups, and indirect-bonding trays. A patient s stone models or PVS impressions were mailed to the OrthoCAD scanning center, where they were processed into a digital file that was downloaded to the doctor s office network.

5 In 2006, Cadent developed the in-office iTero* digital impression system, which by 2008 was capable of full-arch intraoral scanning (Fig. 1); in late 2009, Cadent launched the iOC* system for iTero users. Align Technology purchased Cadent in 2011, allowing clinicians with iOC to begin submitting 3D digital scans in place of physical impressions for the fab-rication of Invisalign October 2012, 3M ESPE introduced the True Definition** scanner, enabling orthodontists to submit digital scans for Incognito** custom lingual braces. Six months later, Ormco released the Lythos** digital impression system for its Insignia** and Clearguide** appliance systems. In January 2014, after much demand for further interoperability between manufacturers, the True Definition scanner qualified for Invisalign case submission, so that True Definition scans could now be used for Invisalign submission and iTero scans for the Incognito appliance the growing popularity of intraoral digital scanners, questions remain regarding their applications and the differences among manufac-turers.

6 This article will review the use of intraoral digital scanners in the orthodontic office, includ-ing an in-depth examination of the iTero, True Definition, and Lythos of Digital ScanningAlginate and PVS impressions have been associated with problems such as pulls, tears, bubbles, voids, tray-to-tooth contact, separation from the impression tray, temperature sensitivity, limited working time, material shrinkage, inac-curate pouring, model overtrimming, and breakage during shipment2 (Fig. 2). Impression taking also heightens anxiety and discomfort for patients of all ages, particularly those with sensitive gag reflexes. In vitro studies have shown that full-arch digital scans are as accurate as conventional im-pressions,3 without these the orthodontist, advantages of digital scanning include improved diagnosis and treatment planning, increased case acceptance, faster records submission to laboratories and insurance providers, fewer retakes, reduced chairtime, standardization of office procedures, reduced storage require-ments, faster laboratory return, improved appliance accuracy, enhanced workflow, lower inventory expense, and reduced treatment times.

7 Benefits to the patient include an improved case presentation and a better orthodontic experience with more comfort and less anxiety, reduced chairtime, and easier refabrication of lost or broken appliances, as well as potentially reduced treatment TechnologyDigital intraoral scanners are considered Class I medical electrical devices, designed and constructed in accordance with the standards of ANSI/IEC 60601-1. Every scanner has three major components: a wireless mobile workstation to sup-port data entry; a computer monitor to enter pre-scriptions, approve scans, and review digital files; and a handheld camera wand to collect the scan data in the patient s mouth. To gather surface data points, energy from either laser light or white light is pro-*Trademark of Align Technology, San Jose, CA; **Trademark of 3M Unitek, Monrovia, CA; **Trademark of Ormco, Orange, CA; 1 iTero intraoral digital scanner in XLVIII NUMBER 6 Kravitz , Groth, Jones, Graham, and Redmond precision optical measurements determine the distance measurement, the differential measure-ment is unaffected by changes in tooth colors and in-motion video uses an HD video camera with trinocular imaging three tiny video cameras at the lens to capture three precise views of the tooth (Fig.)

8 3D). A complementary metal-oxide semiconductor (CMOS) sensor behind the cameras converts the light energy into electri-cal signals. The distances between two data points jected from the wand onto an object and reflected back to a sensor or camera within the wand. Based on algorithms, tens or hundreds of thousands of measurements are taken per inch, resulting in a 3D representation of the object s technology used by the wand to capture surface data determines the measurement speed, resolution, and accuracy of the scanner. Four types of imaging technology are currently employed:Triangulation, used in CEREC,4 measures the angles and distances from known points with projected laser light (Fig. 3A). The distance be-tween the laser source and the sensor is known, as is the angle between the laser and the sensor.

9 As light reflects off the object, the system determines the angle of reflection, and therefore the distance from the laser source to the object s surface, according to the Pythagorean theorem. To provide uniform and predictable light dispersion, this technology requires a thin coating of opaque pow-der to be applied to the target confocal imaging projects laser light through a filtering pinhole to the target tissue (Fig. 3B). The sensor is placed at the confocal (in-focus) imaging plane relative to the target, and a small aperture in front of the sensor blocks any light from above or below the plane of focus. Only focused light reflecting off the target tissue will reenter the filter and reach the sensor for process-ing; out-of-focus light (bad data) is eliminated, thus maximizing the accuracy of the scan.

10 A par-allel confocal system tomographically slices the object and stitches together thousands of slices of data to create a complete picture a process re-ferred to as point-and-stitch reconstruction .Accordion fringe interferometry (AFI) uses two light sources to project three patterns of light, called fringe patterns , onto the teeth and tissue (Fig. 3C).5 As a fringe pattern hits the surface, it distorts and takes on a new pattern, based on the unique curvature of the object. This distortion in the fringe pattern is referred to as fringe curva-ture . Surface data points of the fringe curvature are recorded by a high-definition (HD) video camera that is offset from the projector by about 30 . Because the differences among the three Fig. 2 Problems seen with conventional 2014 OVERVIEWare simultaneously calculated from two perspec-tives to determine the 3D data, which are captured in a video sequence and modeled in real time.