Digital Dentistry
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`the target site, from which the techni(cid:173)
`cian is able to &bricate an accurate gyp(cid:173)
`sum positive duplicating the original
`intraoral situation. The advent of high(cid:173)
`ly innovative and accurate irnprcssion(cid:173)
`ing systems based on new technologies
`has cre2tcd a paradigm shift in the con(cid:173)
`c:ept for impression making. These sys(cid:173)
`tcmS arc poised to revolurioni:ze the W2Y
`in which dental professionals already
`arc and will continue making impres(cid:173)
`sions for indirect restorative dentistry.
`
`Dental Impressions Using
`3D Digital Scanners:
`Virtual Becomes Reality
`
`Nathan S. Birnbaum, 005;1 and Heidi B. Aaronson, DMD2
`
`Abstract 1he technologies that have made the use of three-dlmenslonal (3D)
`digital scanners an Integral part of many Industries for decades have been
`Improved and refined for application to dentistry. Since the Introduction of the
`first dental lmpresslonlng digital scanner In the 1980s, development engineers
`at a number of companies have enhanced the technologles and aeated In(cid:173)
`office scanners that are Increasingly US4tfl-friendly and able to produce precisely
`fitting dental restorations. These systems are capable of capturing 30 virtual
`Images of tooth preparations, from which restorations may be fabricated
`directly (le, CAD/CAM systems) or fabricated Indirectly (le, dedicated lmpres-
`slon scanning systems for the aeation of accurate master models). The use of
`these products is Increasing rapidly around the wortd and presents a paradigm
`shift In the way In which dental Impressions are made. Several of the leading
`3D dental digital scanning systems are presented and discussed In this artkle.
`
`FROM BITES TO
`BYTES: A BRIEF HISTORY
`OF IMPRESSIONING
`IN DENTISTRY
`Impression making for restorative den(cid:173)
`tistry is a relatively recent concept in
`the miJlennia-old history of restorative
`dentistry. The earliest physical proof
`or record of prosthetic treatment to re(cid:173)
`place missing teeth goes back to .Etrus(cid:173)
`can times, approximately 700 BC in
`which teeth were carved from ivory
`and bone and affixed to adjacent teeth
`with gold wires. It was not until 1856, when Dr. Charles
`Stent perfected an impression material for use in the &brica(cid:173)
`tion of the device that bears his name for the correction of
`oral deformities, that documentation exists of the use of an
`impression material other than beeswax or plaster of Paris,
`which had inherent problems, respectively, of distortion or
`difficulty of use, for creating an oral prosthesis.1
`The first use of an clastomeric material for capturing
`impressions of tooth preparations, as well as other oral and
`dental conditions, was not until 1937, when Scars intro(cid:173)
`duced agar as an impression material for crown prepara(cid:173)
`tions.2 In the mere 71 years that elastic impression materials
`hne been in we, numerous formulations ha\'e been de\·cl(cid:173)
`opcd, all of which ha\"e exhibited particular shortcomings
`
`THE CONCEPT OF IMPRESSION MAKING
`The most critical step in the process of &bricating precisely
`fitting fixed or rcmoV2ble dental prostheses is the capture of
`an accurate impression of prepared or unprepared teeth, den(cid:173)
`tal implanu, edentulow ridges, or intraoral landmarks or
`defects. Unless a wu or min pattern is made directly on the
`teeth, on the cdentulow ridges, or in the defects, which is a
`time-consuming and gcneraJly impractical dfon, the dentist
`or auxiliary must achieve an exact duplication of the site so
`that a laboratory technician, wually at a remote location, can
`create the restoration on a precise replica of the target site.
`Traditionally, the paradigm for transferring the necc.ssary
`information from the patient's oral ca\'ity to the tcchnici:m's
`laboratory bench has been to obtain an accurate m:gati\'c of
`
`1 Associate Clinical Professor, Department of Prosthodontics and Operative Dentistry, Tufts University School of Dental Medicine,
`Boston, Massachusetts; Private Practice, Wellesley, Massachusetts
`2Private Practice, Wellesley, Massachusetts
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`0001
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`Align EX1015
`Align v. 3Shape
`IPR2022-00145
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`Digital Dentistry
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`in the goal of obtaining precise reproduction of the oral
`structures.
`The reversible hydrocolloid agar and the irreversible hy(cid:173)
`drocolloid alginate exhibit poor dimensional stability be(cid:173)
`cause of the imbibition or loss of water, respectively, when
`sitting in wet or dry conditions, as well as in having low
`tear resistance. The Japanese embargo on the sale of agar to
`the United States during World War II spurred research
`into the development of alternative elastomeric impression
`materials. The polysulflde rubber impression material in(cid:173)
`troduced in the late 1950s, originally developed to seal gaps
`berwccn sectional concrete structurcs,3 overcame some of
`the problems of the hydrocolloids. Nevertheless, polysul(cid:173)
`fidc rubber was messy, possessed objectionable taste and
`odor, had long setting times intraorally, and underwent
`dimensional change after the impression was removed from
`the mouth, as a result of continued polymerization with the
`evaporation of water and shrinkage toward the impression
`tray, leading to dies that were wider and shorter than the
`teeth being impressed.• This problem was overcome some(cid:173)
`what by the we of cwtom trays that allowed for 4 mm of
`uniform space for the material and by pouring up the im(cid:173)
`pn:ssion within 48 hours.3
`The introduction in 1965 of the polyether material Im(cid:173)
`prcgum ... by ESPE, GmbH as the 6m clastomcric impres(cid:173)
`sion material specifically developed for use in dentistry
`afforded the profession a material with relatively fast setting
`rime, excellent flowability, outstanding detail reproduction,
`adequate tear strength, high hydrophilicity, and low shrink~
`age. The material is still in use today in several formula(cid:173)
`tions, although it exhibits problems with objectionable odor
`and taste, high elastic modulus (stiffness) often leading to
`difficulty in removing impressions from the mouth, and the
`requirement to pour up models within 48 hours because of
`absorption of water in very humid conditions, which can
`lead to impression distortion.•
`Condensation cure silicone impression materials subse(cid:173)
`quently were developed, but these also suffered from prob(cid:173)
`lems with dimensional accuracy. The creation of addition
`silicone vinyl polysiloxane impression materials solved the
`issues of dimensional inaccuracy, poor taste and odor, and
`high modulus of elasticity, and offerrd excellent tear strength,
`superior flowabihy, and lack of distortion c,·en if modds
`were not poured quickly. The biggest drawback of the poly(cid:173)
`siloxanc impression materials, howc\'c:r, is that tht:}' arc
`hydrophobic. which cm lt:.id 10 1hc: inahility w cap1urc: fine
`
`detail if problems with hcmostasis and/or moisture control
`occur during impression making.
`In addition to the many problems inherent in the accura(cid:173)
`cy of the elastomcric materials themselves, further distortions
`can occur by mistakes made in the mixing of the materials or
`in the impression-making technique, the we of nonrigid
`impression trays,~ the uansfcr of the impression to the dental
`laboratory (often subjecting the impressions to variable tem(cid:173)
`peratures in everything from delivery vehicles to post office
`sorting rooms to the holds of cargo jets), the need for humid(cid:173)
`ity control in the dencal laboratory to assure accuracy in the
`setting of the gypsum model rmtcrials, etc. Newer technolo(cid:173)
`gies that allow for the use of digical scanners for impression
`making arc indeed a welcome development. Digital imp~
`sion making docs not require patients to sit for as long as
`7 minutes with a tray of often foul-tasting and malodorow
`"goop" in their mouths, requiring that they open uncomfort(cid:173)
`ably wide, often gagging. Further, these devices help calm
`dentists' anxieties about economic and time considerations
`when deciding to remake inadequate impressions.
`Advances in computerization, optics, miniaturization,
`and laser technologies have enabled the capture of dental
`impressions. Three-dimensional (3D) digitizing scanners
`have been in use in dentistry for more than 20 years and
`continue to be developed and improved for obtaining virtu(cid:173)
`al impressions. The stressful, yet critical task of obtaining
`accurate impressions has undergone a paradigm shift.
`The computer-aided design/computer-aided manufacture
`(CAD/CAM) dental systems that arc currently available arc
`able to feed data obtained from accurate digical scans of teeth
`directly into milling systems capable of carving restorations
`out of ceramic or composite resin blocks without the need for
`a physical replica of the prepared, adjacent, and opposing
`teeth. With the development of newer high-strength and cs(cid:173)
`thctic ceramic rcstorati\"c materials, such as zirconia, laborato(cid:173)
`ry techniques have been developed in which master models
`poured from elastic impressions arc digitally scanned to create
`stercolithic models on which the restorations arc made. Even
`with such high-tech improvements, it is evident that such
`second-generation models are not as accurate as stereolithic
`models made directly from data obtained from 3D digital
`scans of the tc:cth provided by dl-<licatcd 3D scmners dl-signt.-d
`for impression making. This article outlines the features of
`rwo CAD/CAM systl·ms and two dl·dka1c:d 3D impression(cid:173)
`ing digital scannl·rs that ha\'c bc:c:n g.,ining in popularity in
`this c1m·r~c:nt fldd of 1cd111nlo!!Y·
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`Digital Dentistry
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`C E R E C l
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`Figure 1 The CEREC 3 imaging unit. As a CAO/CAM system,
`the product also includes a separate, newly upgraded
`milling unit, the MC XL
`
`Figure 2 The CEREC 3 camera. The new software used in
`the system includes a camera crosshair, which makes the
`optical impression easier and more predictable.
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`Figure 3 For dentists preferring a complete chair/systems
`arrangement, the CEREC 3 is now included as part of the
`CEREC (hairline integrated unit.
`
`CAD/CAM SYSTEMS
`CAD/CAM technology has been in use for a half a:nrury. It
`originated in che 1950s with numerically controlled m3·
`chines feeding numbers on paper tape into controllers wired
`to motors positioning work on machine tools. It ad\"anccd
`in the I 960s with the creation of early computer software
`that enabled the design of producrs in the aircraft and aut~
`motive industries. The introduction of CAD/CA.1v1 con·
`ccpts into dental applications was the brainchild of Dr.
`Francois Duret in his thesis written ac the Universicc Oaudt
`Bernard, Faculce d'Odoncologie in Lyon, France in 1973.
`encicled "Emprcince Opcique" (OpcicaJ Impression). He de(cid:173)
`veloped a CAD/CAM device, obtained a patent for it in
`1984,6 and brought it co the Chicago Midwinter Meeting in
`I 989. There, he fabricated a crown in 4 hours as attendees
`watched. In the meantime, in I 980, a Swiss dentist, Dr. Wer(cid:173)
`ner Mormann and an dcctricaJ engineer, Marco Brandestini
`developed the concept for what was to be introduced in
`I 987 by Sirona Dental Systems LLC (Charlotte. NO as the
`first commercially viable CAD/CAM system for the fubric(cid:173)
`tion of dental restorations-CEREC•.
`
`CEREC
`The CEREC• 3 system (Figure l), an acronym for Cha.ir-
`side Economical Restoration of Esthetic Ceramics. was ;a
`bold effort to combine a 3D digital scanner (Figure 2) "ith
`a milling unit to create dental restorations from commer(cid:173)
`cially available blocks of ceramic material in a single ap(cid:173)
`pointment. One-appointment direct dental restorations
`eliminated the need for multiple visits, as well as for tempo-
`rization and all of its inherent problems. The CEREC sys-
`tern uses computer-assisted technologies, including 3D
`digitization, the storage of the data as a digital model. and
`proprietary CEREC 3D software that proposes a rcston·
`tion shape based on biogeneric comparisons to adjacenr
`and opposing teeth, and then enables the dentist to modi~·
`the design of the restoration. After this is accomplished. the
`data is transmitted to a milling machine, the latest version
`of which, CEREC inL,b •Mc XL, is capable of milling 1
`crown in as little as 4 minutes from a block of ceramic or com(cid:173)
`posite marerial. The most current version of the CE REC 3
`acquisition unit is integrated into a total chair/systems unir.
`the CEREC Chairlinc (Figure 3).
`Wirh rhis sysrcm, the imprcssioning process ncccssimcs
`achic\'ing adcquarc visualization of the margins of the worh
`pn:pararion hr proper tissue retraction or croughing and
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`hemostasis. The entire area being impressed needs to b1e
`coated completely with a layer of biocompatible titanium
`dioxide powder to enable the camera to register all of th1e
`tissues. This is true not only for digital scanning, but also
`for conventional dastomeric impressions as well.
`Sc\'Cl'a! image views then arc made from an occlus:ll orien(cid:173)
`tation assuring capture of the tooth or teeth being restored, as
`wdl as of the adjacent and opposing teeth. Next, the prepara(cid:173)
`tion is shown on a touch screen that enables the dentist to
`view the prepared tooth from every angle and to focw on
`magnified areas of the preparation. The "die" is "cut" on th1=
`,inual modd, and the finish line is ddincated by the dentist
`directly on the image of the die on the monitor screen. Then,
`the CAD biogeneric proposal of an idealized restoration i:s
`presented by the system, and the dentist is given the opportu(cid:173)
`nity to make adjustments to the proposed design using a
`number of simple and intuitive on-screen tools (Figure 4).
`After the dentist is satisfied with the proposed rcstora-(cid:173)
`tion, he or she mounts a block ofhomogeneow ceramic oir
`composite material of the desired shade in the milling uni1t
`and proceeds with fabrication of the physical restoration .
`The use of color-coded tools during the design stage of the:
`process co determine the degree of interproximal contac1r
`helps to assure finished restorations that require minimal,
`if any, adjustments before cementation.
`
`E4D Dentist
`D4DTechnologies LLC (Dallas, TX), an acronym for Dream"
`Design, De\'elop, Delh·er, introduced the E4D Dentist ... ,
`CAD/CAM system in early 2008, after an extended period!
`of beta-testing and fine-tuning to assure a quaJity produce. 11:
`consists of a cart containing the design center (computer andl
`monitor) and laser scanner (Figure 5), a separate milling unit,,
`and a job server and router for communication. The scanner1,
`termed the lntraOral Digitizer, has a shorter \'ertical profile:
`than that of the CEREC system, so the patient is not re-·
`quired to open as wide for posterior scans.
`Of significance, the E4D Dentist does not require the:
`use of a reflecting agent, such as titanium dioxide powder,.
`to enable the capture of fine detail on the target site. Other
`CAD/CAM systems create a digital "gypsum" model on
`which the restoration is m:ide. While the E4D Dentist can
`create such models when che scanner is used on eit11er actual
`gypsum models or elascomc:ric impressions, it creates a more
`accurate an<l inlormaciw mode:! whc:n scanning is done with
`the lntraOral Digicizc:r (Figurt' 6 ).
`
`Birnbaum and Aaronson
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`Rgure 4 A screen shot of an onlay restoration proposed by
`the software library. User-friendly tools permit refinement
`of the restoration before milling.
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`Figure 5 The E4D imaging unit. The CAD/CAM system also
`includes a separate milling unit for fabricating restorations.
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`Digital Dent istry
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`The ICfaerything"" (ICE) feature of the system's Denta-
`1.ogic"' software cakes accual piccures of the teeth and gingi\'a
`before treatment and after tooth preparation, as well as an
`ocdusal rc:giscracion. As successi\'e picmres are taken, they are
`wrapped ~tround the 30 model co create the ICE model. The
`30 ICE view makes margin detection simpler co achie\'e
`(Figure 7). The couch screen monitor enables the dentist co
`\'iew the preparation from \'arious angles to assure its accuracy.
`The design system of the E4 D Dentist is capable of auto(cid:173)
`detecting and marking the finish line on the preparation. Af(cid:173)
`ter the dentist appro\'es this landmark, the software uses its
`Aucogenesis .... feature to propose a restoration, chosen from its
`anatomical libraries, for the tooth to be restored (Figure 8).
`
`As with the CEREC system, the operator is pro,·ided \\ith
`a number of highly intuitive tools to modify the resron·
`tion proposal. After the final restoration is approved, the
`d,esign center transmits the data to the milling machine.
`Using blocks of ceramic or composite mounted in the mil·
`ling machine, and with the aid of rotary diamond instru·
`men ts chat can replace themselves when worn or damaged. J
`the dentist can f2bricate the physical restoration.
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`DEDICATED IMPRESSION
`SCANNING SYSTEMS
`Dedicated 30 digital dental impression scanners eliminm
`several time-consuming steps in the dental office, includi~
`
`figure 6 The lntraOral Digitizer, which does not require the use of a re flecting powder to capture images. can be used to scan
`teeth, mc,dels, or elastomeric impressions.
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`tray selection, dispensing and setting of materials, disinfec(cid:173)
`tion, and shipment of impressions to the laboratory. In
`addition, the laboratory sa\'es time by not having to pour
`base and pin models, cut and trim dies, or articulate casts.
`With these systems, the final restorations arc produced in
`the laboratory, but they arc fabricated on models created
`from the data in the digital scans, as opposed to gypsum
`models made from physical impressions. Patient comfort,
`treatment acceptance, and education arc added benefits.
`Digital scans can be stored on computer hard dri\'es indefi(cid:173)
`nitely, whereas con\'cntional models, which may chip or
`break, must be stored physically, which often requires extra
`space in the dental office.
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`iTero
`The iTero"' digital impression system (Cadent, Carlstadt,
`NJ) was introduced in early 2007. following S years of in(cid:173)
`tensive research and beta-testing. Based on the theory of
`.. parallel confocal," the iTero scanner emits a beam of light
`through a small hole, and any surf.ice within a certain dis(cid:173)
`tance will reflect the light back toward the wand. The iTcro
`device projects 100,000 beams of red light, and within one
`third of a second, the reflected light is converted into digital
`dat2. There is no need for the use of a reflecting agent, such
`as titanium dioxide powder, as the laser is able to reflect off
`all oral struaurcs.
`The iTcro system includes a computer, monitor, mouse,
`integrated keyboard, foot pedal, and scanning wand organ(cid:173)
`ized on a well-designed mobile can (Figure 9). Disinfection
`consists of replacing the disposable sleeve on the handhdd
`scanner (Figure 10). The end of the scanner that enters the
`mouth has the tallest vertical profile of the systems reviewed
`in this article (Figure 11), and thus requires wider mouth
`opening by the patient.
`Voice prompts guide the dentist in taking a series of
`scans of the patient's teeth and occlusal registration. The
`images arc captured on the monitor by stepping on the foot
`pedal. The image on the screen is similar to a viewfinder
`on a camera, which allows the dentist to position the cam(cid:173)
`era correctly while looking at the screen. As this is not a
`continuous scan and no powdering is necessary, the dentist
`may remove the scanner from the mouth to dry or rinse
`fluids as nc:ccssary.7 Individual images may be retaken to
`ensure capture of adequate detail. If the preparation must
`be modified, the quadrant needs rn be rescanned after all
`adjustments arc complctc.8
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`Bir nbaum and Aaronson
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`Figure 7 30 ICE view of a prepared tooth derived from the
`ICEverything feature of the Dentalogic software from pre(cid:173)
`and postoperative scans.
`
`Figure 8 The Autogenesis feature of the E40 system pro(cid:173)
`poses a restoration, which can be enhanced by the opera(cid:173)
`tor with simple onscreen tools before milling.
`
`After all scans (at least 21) arc completed, the: dentist
`steps on the foot pedal and, within a few minutes, the digi(cid:173)
`tal model is displayed on the monitor (Figure 12). Using a
`wirc:less mouse, the: dentist can rotate the model on the
`screen to confirm that the preparations are satisfactory be(cid:173)
`fore temporizing the teeth and sending the scans to the lab(cid:173)
`oratory. Voice prompts again are very helpful in assuring
`that such necessities as proper occlusal tooth reduction for
`the intended crown type have been achie\'ed.
`All patient data and laboratory prescriptions arc input in(cid:173)
`to the: computer before the scanning procedure. Digital data
`arc: sc:nt wirelessly to Cadent, where the digital impression is
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`Digital Dentist ry
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`Figure 9 The iTero 30 digital impression system. Scan data of
`preparations are e-mailed wirel~ to Cadent for creation of the
`model, which then is sent to the laboratory for the restoration.
`
`;J
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`(I
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`:n the Massachusetts Institute of Technology. The Lm
`C.O .S. was created at BrontesTechnologies Inc (Lexington.
`MA) and was acquired by 3M ESPE (St. PauJ, MN) in Oc(cid:173)
`tober 2006. The product was launched officially at the Gu(cid:173)
`e.ago Midwinter Meeting in February 2008.
`The method used for capturing 30 impressions im-oh-o
`active wavefront sampling (AWS), which enables a 30-in(cid:173)
`Motion technique. This technique incorpor:ues n:volurion(cid:173)
`ary optical design, image processing algorithms, and real(cid:173)
`time model reconstruction to capture 30 data in a video
`sequence and model the data in real time. Other digital im(cid:173)
`pressioning sC1nners use triangulation and laser approacho.
`which rely on the warping of a laser or light patrern on an
`object to obtain 30 data. In so doing, these methods arr
`relatively slow and have the downside of distortion and
`optical illusion. By usingAWS, however, the LAVA C.O.S.
`captures scanned images quickly (approximacdy twency 3D
`data secs per second, or close to 2,400 data sets per arch) in
`video mode and creates a highly accurate virtual on-scrttn
`model instantaneously. IO
`The La\'a C.O.S. unic consists of a mobile cart (Figure 13)
`containing a computer, a couch screen monitor, and a son·
`ning wand (Figure 14), which has a 13.2-mm wide tip and I ··
`weighs 14 oz (about che size of a large power toothbrush).
`The end of the scanner that enters the mouth is the smallest
`I .,.
`of che systems re\'iewcd in this anicle. The camera at the tip
`of the wand (Figure 15) contains 192 light-emitting diodo I ~~
`(LEDs) and 22 lenses. There is no need for a keybw.rd or
`mouse, as the monitor displays a keyboard for aJI data in· I ·,
`
`j :~
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`put. Disinfection im·ol\'es a simple wipe down of the mon-
`itor with an intermediate-level surface disinfectant designcJ 1 •
`for use on nonporous surfaces and replacement of the pl2r I ·
`tic sheath on the wand.
`Whereas the Cadent iTero does not require any powdcr(cid:173)
`i ng and the CEREC requires hea\'y powdering, the u,·l
`C.O.S. requires only enough powdering to allow the sCll\·
`ncr to loCJte reference poincs. Therefore a \'Cry light dusting
`of powder is required, and is produced using the powdering
`gun prm·ided with the unit.
`Following preparation of the tooth and gingi\'al rc.-trac·
`cion (if necessary), the entire arch is dried thoroughly anJ
`lightly dusted with powder. The dentist begins scanning b~·
`pressing either a lnmon on the sCJnning wand or the sun
`key on the: touch scn:cn monitor. A pulsing blue lighc cm·
`an.Hes from che wand head as a black and white video of Ult"
`1n·ch ap1w,irs inscam.111cously on the monitor. Scaning on
`
`1
`
`Figure 10 iTero's handheld digital scanner does not require
`the use of a titanium dioxide reflecting agent to capture
`digital images of hard and soft tissues.
`
`refined and a hard plastic model is milled. Cadent chen
`returns che model to che local dental laboratory, which
`complecc:s the f1nal rc:sroracion.9
`
`Lava C.O.S.
`The La\'a"' Chairside Oral SCinnc:r (C.O.S.) wa.-. born m11 of
`che research of Professor Doug Han and Dr. Janos Roh.ily
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`Birnbaum and Aaronson
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`Figure 12 Typical screen shot of a prepared arch, which may
`be viewed at any angle using the wireless mouse.
`
`Figure 13 The Lava Chairside Oral Scanner (C.O.S.). Note the
`absence of a keyboard because data entry and laboratory
`prescriptions are done onscreen.
`
`rl Figure 11 iTero's scanner is used intraorally to capture Indi(cid:173)
`vidual 3D images as the dentist follows voice prompts to
`assure accurate scanning and occlusal clearance.
`
`· the ocdusal surface of any posterior tooth, the dentist guides
`the w:md forward over the occlusal surfaces of the sextant
`,. being scanned, and then ror2tes the wand so that the bucal
`surfuccs arc captured.
`The wand then is mo\'ed posteriorly, capturing all the
`_; buccal surfaces with some O\'c:rlap of the occlusaJ. After he or
`she reaches the most posterior tooth, the dentist begins scan(cid:173)
`-r- ning the lingual surfaces of all the tc:cth in the sextant. The
`• "stripe scanning" is completed when the dentist returns to
`scanning the occlusal of the starting tooth, ic:, "closing the
`loop." If any sudden movement occurs, the image automati(cid:173)
`.,..
`., cally pauses and the dentist can continue by returning to any
`surf.lee that has been previously scanned. The software: rec-
`ognizes data that is already in the computer and resumes
`scanning without the need for pressing any buttons. Ad(cid:173)
`ditionally, the software can distinguish between surfaces that
`a.re intended to be scanned (ic:, teeth and attached gingiva)
`and extraneous data (ic:, tongue, checks, etc).
`As the teeth arc scanned, they turn bright white on the
`·· monitor, and any areas that remain in red nc:cd to be scanned
`for more detail. To help the dentist maintain the wand at a
`proper distance from the tc:cth, a target appears on the mon(cid:173)
`itor to indicate whether the wand is too close or too far away
`from the tcc:th. With the help of these on-screen guides, the
`dentist can modify the continuous scan without pausing,
`·· withdrawing the wand, or restarting the scan.
`After scanning the preparation and adjacent teeth, the
`dentist pauses the scan and evaluates the result on the mon(cid:173)
`itor. He or she is able to rotate and magnify the view on the
`screen, and also switch from the 3D image to a 2D view of
`the exact images captured by the camera during the scan. A
`
`;,
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`0008
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`

`Digital Dentistry
`
`Figure 14 The Lava C.O.S. camera has the smallest wand of
`any of the reviewed systems, making access to all parts of
`the oral cavity easier to achieve.
`
`Figure 15 The tip of the wand contains 192 LEDs and 22
`lens systems and captures impression and occlusal registra(cid:173)
`tion data in video mode.
`
`Figure 16 Typical screen shot of a prepared tooth. In addi(cid:173)
`tion to the image shown, the dentist and laboratory techni(cid:173)
`cian can view it in stone cast mode or with 3D glasses.
`
`third option aJlows the dentist to view these images while
`wearing 3D glasses.
`After the dentist confirms that all necessary derails were
`captured on the scan of the preparation (Figure J 6), a quick
`scan of the rest of the arch is obtained, which takes approx(cid:173)
`imately 2 minutes. If there are holes in the scan in areas
`where data is critical, such as cusp tips or contact points, it
`is not necessary to redo the entire scan. Rather, the dentist
`simply scans that specific area and the software patches the
`hole. The software uses reference points on the scanned
`images to integrate the new data with that of the previow
`scans; therefore, it is crucial to have some overlap when
`sc:inning new data.
`After the opposing arch is scanned, the patient is in(cid:173)
`structed to close into maximal intercuspaJ position. The
`buccal surfaces of the teeth on one side of the mouth are
`powdered, and a 15-sccond scan of the occluding teeth is
`captured. The maxillary and mandibular scans then arc di(cid:173)
`gitaJly aniculated on the screen.
`After aJI the scans have been reviewed for accuracy, the
`dentist uses the touch screen monitor to complete an on(cid:173)
`screen laboratory prescription. The data is sent wirdcssly to
`the laboratory technician, who then wes customized soft(cid:173)
`ware to cut the die and mark the margin digitally. 3M ESPE
`receives the digital file where it is ditched vinuaJly, and the
`data is articulated seamlessly with the operative, opposing,
`and bite scans. At the model manufacturing fucilicy, a sterc(cid:173)
`olithography model is generated, and is sent to the labora(cid:173)
`tory (along with a Lava coping if the restoration is to be a
`Lava crown), where the technician creates the final restora(cid:173)
`tion. Despite the name of the system, it is not dedicated
`only to the creation of Lava crowns, as all types of finish
`lines may be reproduced on the stereolithography dies,
`allowing for any type of crown to be manufaccured by the
`dental laboratory.
`
`LEARNING CURVE
`All of the 3D digital impressioning systems reviewed in this
`article have the potential to produce restorations with im(cid:173)
`proved marginal flt over that of traditional dastomeric im(cid:173)
`pressions, based on the fact that the master die is created
`from digital data obtained from the tooth preparation,
`rather than from a second- or third-~cneration impression
`or model. The success or the CEREC system over the past
`2 l years in convincing many demists worldwide to engage
`in new rcchnologic:s bodes well for the rucurc of all or the
`
`0009
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`

`

`systems that have been and will continue to be developed.
`One of the factors that prevent dentists from .. taking off the
`blinders" and attempting to introduc:c new techniques and
`instruments into their dental practices is the fear that the
`learning curve is too great and that .. you can't teach an old
`dog new tricks."
`Recent research adv:anccd by Nol!'man Doidgc11 shows
`that ncuroplasticity in the brain exists throughout the hu(cid:173)
`man lifespan and that the ccrebr.al concx is capable of con(cid:173)
`stantly undergoing improvements in cognitive functioning.
`This means that any wk that requires highly focused atten(cid:173)
`tion or the mastery of new skills helps to improve the mind,
`especially memory. Admittedly, learning to use any of the
`digital scanners discussed in this article means acquiring
`new skills and mastering new techniques, which will take
`some time and patience. The bottom line, however, is that
`the end result of developing the ability to use these new
`technologies will empower dentists tc> learn more about the
`dentistry they perform and enable 1thcm to provide their
`patients with well-fitting restorations.
`
`THE ECONOMICS
`The cost of all the systems presented, ranging from just over
`$20,000 to well o,'Cr $100,000, may appear prohibitive for
`many, if not most, small dental pr.actices. Nevertheless,
`when all of the attendant costs of traditional impression(cid:173)
`making arc taken into account, including the frequent need
`to remake impressions or c,·cn remake restorations as a
`result of the shoncomings of the older techniques and ma(cid:173)
`terials. and considering the improved quality of restorations
`made possible by the newer digital systems, the 3D digital
`imprcssioning systems become more appealing. The lease
`programs offered through most CAD/CAM system manu(cid:173)
`facrurcrs have brought using this technology into the realm
`of profitability for practices producing more than 14 indi(cid:173)
`rect restorations a month.
`Notwithstanding the ethical dilemma of dentists' pro·
`viding indirect ceramic restorations when simpler and less
`expensive composite restorations arc: achievable simply to
`justify the )case expenses of an cxpensi\·c digital system, the
`use of new and better technology to improve the quality of
`dentistry is an ad\'antage that well-educated patients arc
`becoming incrc:a!iingly more: willing to accept, e,·cn at a
`higher cost. The: tel'hnology oOD digital imprc:ssion sc:tn·
`ning has ad\'ancc:<l to a l<.·\'d at which it can no longer be
`ignored. Virtual has b<.'come a rl".tliry.
`
`Birnbaum and Aaronson
`
`A