alessandroagnini
`andreaagnini
`CO-AUTHOR
`chrstancoachman
`
`}DIGITALDENTAL
`&- REVOLUTION THE LEARNING CURVE
`
`Align Ex. 1014
`Align Ex. 1014
`U.S. Patent No. 9,962,244
`U.S. Patent No. 9,962,244
`
`0001
`
`0001
`
`

`

`
`
`
`
`~
`
`alessandroagnini
`andreaagnini
`
`TVGITAL DENTAL REVOLUTION
`
`THE LERANING CURVE
`
`
`
`
`Milan, Berlin, Chicago, Tokyo, London,
`Paris, Barcelona, Beijing, Istanbul,
`Moscow, New Delhi, Prague,
`So Paulo, Seoul, and Warsaw
`
`0002
`
`c
`
`0002
`
`

`

`
`
`e
`
`Copyright © 2015 by Quintessenza Edizioni S.rl.
`Via Ciro Menotti, 65 — 20017 Rho (MI)Italy
`Tel +39,02,.93180821 - Fax number +39.02.93186159
`
`
`Email: info@quintessenzaedizioni it
`www. quintessenzaedizioni.com
`
`ISBN:
`
`978-88-7492-017-4
`
`All rights reserved. This book or any part thereof may not be reproduced, stored in a retrieval system, or transmitted
`in any form or by any means, electronic, mechanical, photocopying, or otherwise, without prior written permission of
`the publisher.
`
`Printed in Italy
`
`0003
`
`0003
`
`

`

`
`
`| TABLE OF CONTENTS
`
`
`
`
`
`CHAPTER
`
`sa Diagnosis
`
`CHAPTER
`
`4 New Technologies...2
`
`introduction ..3
`Tradition vs innovation:
`What has changed? ...6
`Traditional protocol work flow ...7
`Technical work flow with
`CAD/CAMtechnology...8
`Material selection and treatment plan
`sequencing ...12
`Zirconia ...20
`Zirconialiterature review ...22
`
`and Communication ...40
`Smile analysis and esthetic designs ...42
`Initiating smile analysis: Evaluating facial and
`orofacial esthetics...43
`Evaluating oral esthetics ...44
`Dentogingival esthetics ...44
`Digital Smile Design approach...45
`DSD protocol:
`- Esthetic diagnosis ...47
`- Communication...47
`- Feedback...48
`
`~ Patient management...48
`- Education ...49
`
`DSD work flow ...49
`
`DSDconcept goals ...53
`Smile design test drive ...57
`
`DSD Connect...83
`
`The four DSD views ...84
`Conclusion...85
`References...87
`
`Mechanical properties of zirconia
`ceramics ...23
`
`CAD/CAM technology for fabrication of zirconia
`abutments and frameworks for crowns and fixed
`dental prostheses...23
`
`Considerations for using zirconia as a restorative
`material ...24
`
`Considerationsforfixed implant restoration
`designs...32
`Zirconia abutments...33
`Recommended clinical protocols ...34
`
`References ...36
`
`XV
`
`0004
`
`0004
`
`

`

`
`TABLE OF CONTENTS|
`
`CHAPTER
`
`CHAPTER
`
`Gr Digital Impression me| The Learning Curve ...120
`
`Digital impressionsin theliterature .,.97
`
`The digital workflow ...100
`
`The Zfx intraoral scanner ...101
`
`Learning curve ,..122
`
`Knife-edge preparation: A possibility with new
`materials? ...132
`
`Highlights of the system .,.102
`
`Zirconia and new technologies ...134
`
`Important areas ...107
`
`Areas of less importance ...107
`
`STEP 1. Target area definition ...107
`
`STEP 2. General scan ...107
`
`STEP 3, Checking and finishing phase .,.107
`
`Conclusion ...114
`
`References ...116
`
`New customized abutmentdesign: Zirconia inside
`laminate (ZIL) ...138
`
`Is it possible to apply ZIL in the anterior
`dentition? ...142
`
`Soft tissue displacement: Indications, purpose,
`and techniques ...151
`
`Impression objectives ...155
`
`Implants and digital impressions ...155
`
`Surgical procedure ...158
`
`Tooth extraction ...159
`
`Implant placement ...160
`
`Trabecular Metal Material ...160
`
`Gap management...161
`
`Provisional restoration fabrication ...162
`
`Connective tissue graft augmentation ...163
`
`Bone graft augmentation ...165
`
`Digital impression taking ...167
`
`Technical workflow ...167
`
`Protocolfor overbuilding
`of the socket site ...174
`
`CAD/CAM implant abutments:
`The true advantage ...186
`
`Titanium or zirconia abutments:
`Whatis the rationale? ...188
`
`References ,..193
`
`0005
`
`XV
`
`0005
`
`

`

` | TABLE OF CONTENTS
`
`
`CHAPTER
`CHAPTER
`
`
`
`Yire New Digital
`
`Possibilities ...254
`
`Monolithic zirconia: Why and when...259
`Zfx Zirconium Effect 2.0 Multilayer ..,262
`Combiningclinical experience: Monolithic
`zirconia crowns and digital impressionsfor a
`predictable restorative alternative ...263
`
`Preliminary healing time ...266
`
`Monolithic zirconia and intraoral scanner:
`Predictable for complex rehabilitations? ...270
`
`Cementation: Finalization of the prosthetic
`rehabilitation ...286
`
`New implant materials ...287
`
`Trabecular Metal implantrationale ...292
`
`Definitive prosthetic phase..,.296
`
`References...302
`
`
`
`Treating Complex Cases
`with New Technologies and
`Materials ...198
`
`Treatment planning in complex cases ...205
`Patient complaint and history ...207
`Preliminary tests and treatment ...207
`
`Diagnosis and treatment pian ...208
`
`Surgical phase ...210
`
`Immediate provisionalrestoration ...214
`
`Definitive restoration workflow ...212
`
`Advantages of three-dimenstonal
`dental imaging ...220
`
`Surgical phase ...224
`
`Prosthetic phase ...227
`
`Definitive restoration: The role of digital
`dentistry ...229
`
`Scanning strategy:
`A critical step for success ...234
`
`Passivefit ...248
`
`References ...250
`
`XVI
`
`
`
`0006
`
`0006
`
`

`

`
`TABLE OF CONTENTS|
`
`CHAPTER
`
`CHAPTER
`
`bd Lithium Disilicate ...306
`
`Lithium disilicate: Literature review ...307
`
`Digital systems ...308
`
`Clinical applications ...310
`
`Cementation operational protocol ...316
`
`Implant abutment: Selection criteria ...323
`
`References ...342
`
`The Immediate Digital
`Future ...344
`
`The future of digital dentistry: New technolagy
`and dental team: Partners in success...345
`
`The digital challenge: Saving the patient's time
`without losing quality in the definitive
`restoration ...347
`
`Digital and implant dentistry: Standard of
`patient care ...355
`
`The three-step protocol:
`- Appointment 7: Implant surgery
`and scanning ...356
`
`- Appointment 2: Re-entry ...356
`
`- Appointment 3: Delivery ...358
`
`Fully digital restorative work flow ...370
`
`The digital articulator ...376
`
`Digital provisional restoration .,.379
`
`Future is now: The importance of keeping the
`dental team up-to-date ...387
`
`PMMA: A new restorative solution ...396
`
`Conclusions: Anticipating the future ...396
`
`References ...398
`
`XVI
`
`0007
`
`0007
`
`

`

`
`inaccuracies. CHAPTER
`
`TRE DIGITAL
`IMPRESSION
`
`Every year in the US, 400,000
`impressions are made: 907 did
`hot have the margin recorded
`completely; therefore, there are
`360,000 crowns with margin
`
`Gordon Christensen
`
`
`
`0008
`
`0008
`
`

`

`_—
`
`
`THE DIGITAL IMPRESSION |
`| HAPTER 3
`
`
`
`
`
`for fabrication of
`technology (DDT)
`Digital dental
`dental
`restorations,
`including computer-aided de-
`sign/computer-assisted manufacture
`(CAD/CAN),
`has been in development since the 1980s."
`Its
`rapid expansion and incorporation into the field of
`dentistry has been documented since the beginning
`of 1990s.1*
`Currently present on the market are several diag-
`nostic digital software programs, for example, the
`Digital Smile Design (DSD) created and designed
`by Christian Coachman and Livio Yoshinaga, digital
`tools to check functional parameters and define tooth
`shades, which in this era of esthetics are becoming
`more important every day; digital articulators and
`digital customized abutments; and computer-guided
`surgery that can be combined with a three-dimen-
`sional (3D) computed tomography (CT) evaluation to
`provide a wealthofinformation to the surgeon before
`and after procedures. In the last few years, several
`software programs for digital impressions have been
`developed, playing an important role in the transi-
`tion from conventional fixed prosthodontics to DDT
`
`because they represent one of the very last steps to-
`ward fully digital prosthetic fabrication, which is the
`goal of modern dentistry. The intraoral impression,
`indeed, is the first means of communication between
`clinician and technician.*
`Digital dental
`impression devices have been intro-
`duced to the profession, potentially eliminating the
`need for taking conventional impressions for crowns
`and fixed prostheses. The direct acquisition systems,
`which have been continually improved, are less in-
`yasive, quicker, and more precise than conventional
`methods. Moreover,
`traditional protocols
`require
`manycritical steps that can be skipped when taking
`a digital impression.
`In fact,
`this technique can reduce chair time for
`procedures such astray selection, cast setting time,
`disinfection, and transportation to the laboratory.
`In
`addition,
`the digital
`images can be easily stored.
`These emerging new digital concepts are creating
`a growing interest among dentists, causing them to
`think about the pessibility of changing their impres-
`sion techniques.*°
`
`89
`
`0009
`
`0009
`
`

`

`
`I CHAPTER 3
`
`
`
`Fig 1. The digital dental
`revolution. The goal of modern
`dentistry is to create a completely
`digital work flow.
`
`Some clinicians face the dilemmaof wanting to keep
`up with the technologic advancesin the profession
`while feeling unsure about embracing the digital im-
`pression technique and the related in-office milling
`of restorations (Fig 1).
`
`in 1987 as Cerec (Sirona), thefirst commercial CAD/
`CAMsystem for dental restorations.2”
`Since that time, research and development sectors
`at many companies have improved their technology
`and created in-office intraoral scannersthat are in-
`
`
`
`ie Benefits of the digital impression have been pre-_creasingly user-friendly and produce preciselyfitting
`
`sented as:
`
`Improved patient acceptance
`1.
`2. Reduced distortion of impression materials
`3.
`3D preview of the preparation
`4, Potential cost reduction and time effectiveness*
`
`Digital impressionsfor implant rehabilitations (Fig 2)
`would allow for:
`
`1. Virtual assessment of the implant prosthetic
`space
`
`2. Evaluation of depth of restorative margin
`3. Configuration of the emergence profile before
`proceeding with laboratory steps®
`Digital
`impressions have been used successfully
`for a number of years in orthodontics with soft-
`ware such as iOC/OrthoCAD (Cadent}, OrthoPiex
`(Denisply}, SureSmile (Orametrix), and RapidForm
`(EMS). The introduction of the first digital
`intraoral
`scannerfor restorative dentistry was in the 1980s
`by a Swiss dentist, Dr Werner Mérmann, and an
`Italian electrical engineer, Marco Brandestini, who
`developed the conceptfor what would be introduced
`
`ra
`
`
`
`
`
`90
`
`0010
`
`dental restorations. These systems are capable of
`capturing 3D virtual images of tooth preparations;
`from such images, restorations may be directly fab-
`ricated (using CAD/CAM systems), or they can be
`used to create accurate master casts for fabrication
`
`laboratory.’ Today
`of the restorations in a dental
`there are 11 intraoral scanning devices for restor-
`ative dentistry available worldwide; four are made
`in the United States; twoin Israel; two in Germany;
`and one eachin Italy; Switzerland; and Denmark.
`Generally speaking, such scanners try to overcome
`the problems and disadvantages of the traditional
`impression fabrication process, suchasinstability of
`the impression, pouring of plaster, laceration of the
`margins, and geometric and dimensional discrepan-
`cy between the cast and the impression,
`The main benefits of the use of these devices are
`
`precise casts/models, creation of 3D archives
`and surgery simulation, and a simplified process.
`Existing devices are driven by several noncontact
`optical technologies, such as confocal microscopy,
`optical coherence tomography, photogrammetry,
`active and passive stereovision and triangulation,
`interferometry, and phase-shift principles. Basically,
`all of these devices combine some of the cited im-
`
`aging techniques to minimize the sourcesof distur-
`bancerelated to scanning inside an oral cavity, eg,
`optical features of the target surfaces (translucency
`and the different reflectivity of the target materials
`such as teeth, gingiva, preparations, and com-
`posites), moisture, and random movements. Also,
`several types of structured light sources andoptical
`components are used.®
`Commercially available digital systems for the den-
`tal office are commonly divided into two categories:
`digital impression systems and chairside CAD/CAM
`systems, Both types must be able to accurately re-
`cord the intraoral condition on a computer datafile
`with a scanner or camera.
`
`0010
`
`

`

` THE DIGITAL IMPRESSION|
`
`
`
`Fig 2. Detail of the position of the lens of
`the intraoral scanner during scanning for a
`provisionalrestoration.*
`
`Figs 3 te 5,Lava, iTero, and TRIOS are
`some of the most common examples of
`digital impression systems.
`
`Fig 6. Gerec AC is one of the two available
`chairside CAD/CAM systems.
`
`It ig what the system accomplishes after recording
`the datafile that distinguishes them:
`¢
`Digital
`impression systems are designed to
`electronically transmit the recorded datafile to
`the dental laboratory for restoration fabrication.
`Once dental laboratories have downloaded the
`file, they can have casts processedfrom it. Any
`conventional
`laboratory process can be used
`to fabricate the restoration once the laboratory
`receives the processed casts. Alternatively, the
`dental laboratory can use the transmitted data
`file in a CAD program to create a full-contour
`restoration or coping that can be refined on the
`processed casts. Some of the most common
`examples of digital impression systems are the
`Lava Chairside Oral Scanner(C.0.S.; 3M Espe),
`the iTero system (Cadent, the Zfx system (Zt),
`and TRIOS (3Shape). This expedites the overall
`work flow, resulting in delivery of the definitive
`restoration in a shorter time span compared
`with the traditional approach (Figs 3 to 5).
`The Cerec Acquisition Center (AC; Sirona) and
`E4D Dentist system (E4D Technologies) are the
`
`—
`
`two available chairside CAD/CAM systems. They
`can complete all three steps of the imaging,
`design, and milling process in the dental office
`to fabricate full-contour restorations within the
`time span of a single appointment. Both of them
`have manufacturer-specific software programs
`that permit the production of single-toath ce-
`ramic or composite inlays, onlays, veneers, and
`crowns. They also offer the option to be used as
`purely digital impression systems. The choice to
`adopt one method or the other depends on the
`organization of the dental office and ihe type of
`initial investmentthatIs intended.
`
`91
`
`0011
`
`0011
`
`

`

`
`
`| CHAPTER 3
`
`
`
`
`
`Figs 7 and 8. Taking a good
`impression is one of the most
`crucial steps of the clinical
`work flow.
`
`=
`
`in fixed prosthodontics, an accurate and precise
`impression is one of the main requirements for
`obtaining a proper and long-lasting restoration.'°
`When discussing digital
`impression taking com-
`pared with the conventional approach, an argu-
`mentis always madethatthelatter is more precise
`and that there is a mandatory and time-consuming
`learning curve involved in learning to use the new
`digital tools.
`However,
`it is important to note that ihe conven-
`tional technique also presents manydifficulties and
`involves a learning curve to avoid all the pitfalls."
`In fact, a recentliterature survey conducted in the
`UK showed that many impressions judged to be
`“acceptable” by dental laboratory technicians are
`not; according to Storey and Coward, 44.2% of
`the intraoral recordings would not be satisfactory
`due to the presenceof imperfections at the level
`of the prosthetic preparations.'? Careful evaluation
`of the traditional impression work flow reveals that
`the many steps involved are sources of possible
`inaccuracies and how it is, once again, critical to
`have a protocol to follow step by step in orderto
`help the operator reduce mistakes" (Figs 7 and 8):
`The clinician should ensure that the impression
`includesall the necessary information, is clearly
`
`is
`readable, provides details of the preparation,
`free of bubbles and tears, and covers all of the
`elements involved,
`
`In a study by Sametet al,'* an assessment was
`made of 193 impressions sent to 11 different
`laboratories. Factors such as the material, the
`technique, the type of impression tray, and ihe
`number of elements prepared were recorded,
`and then the quality of the impression technique
`for the construction of
`fixed prostheses was
`assessed, describing the frequency of clinical
`errors and analyzing the correlations between
`the factors involved (Tables 1 and 2).
`The results can be summarized as follows:
`
`Lack of precision
`e
`e Removal of material from the tray
`e
`Putty exposure in two-stage Impressions
`Taking an impression is,
`in fact, probably the
`most critical step in the process of creating res-
`torations thatfit.
`
`A perfect impression should:
`e
`Provide an exact duplication of the clinical
`situation
`
`e
`
`*
`
`Include a complete, void-free, and accurate
`reproduction of the margins
`Be correct on thefirst attempt
`
`92
`
`0012
`
`0012
`
`

`

`
`
`
`
`THE DIGITAL IMPRESSION |
`
`STOMA
`te OLmNTel(9
`
`resin
`
`Underuseof light-body material and appearance
`of a gap.
`
`Place an adequate quantity of materialin critical areas,
`
`Localized on thelingual
`and buccal surfaces
`Store the productat the indicated ternperatures to
`High environment temperature and premature
`preserve theviscosity and hardening characteristics.
`light curing.
`Use an individual tray.
`
`Localized on the mesial
`Low hydraulic pressure for the flow and adaptation
`and distal surfaces
`Use a combination putty/light-body technique or a
`of the materialto the proximal surfaces.
`two-phasetechnique.
`Incorrect manual mixing of the material with air
`trapping.
`
`Repeat manual mixing.
`
`Maintenanceof the dispensertips or syringes
`dispensed in.
`
`
`impression materials to increase the working time.
`
`
`
`
`
`
`
`Multiple, randomly
`distriouted
`
`Incorrect automatic dispensing(tip notin the
`material}.
`Contamination by moisture, chernicals, or
`crevicularfluids,
`
`Use the double-cord technique to improve the
`Localized in the
`displacement and absorption of moisture.
`sulcular area
`Rinse thoraughly and dry.
`Inadequate hemostasis.
`incorrect technical delivery of the light-body
`material: the start and end points of the material do
`not meet.
`
`Complete delivery of the light-body material 360
`degrees around the abutment.
`
`Localized on the
`preparation margins
`
`Errorin setting times:lack of integration of light-
`body material in some areas.
`
`Use siow-setting materials in complex cases; cool
`
`Table 1. Causes and so
`utions for common defects (voids) that could be found during conventional impression taking
`
`;
`
`
`
`Asta]THK
`
`Prevent movernentofthe tray during the impression.
`Movement/sliding of the tray before complete
`Increase the separation of the material before relining
`Protrusion/projection of
`hardening of the material,
`the impression.
`material (from the surface
`Incorrect repositioning of the tray during relining
`of the impression to the
`Use an custom tray or carefully select a standard tray.
`hollow areas contact
`in the putty wash of the two-phase technique or
`Try in the tray and determine howto correctly insert it
`inappropriate size or shapeof the selected tray.
`between the impresston
`before proceeding with the impression.
`Inaccurate insertionof or excessive thrust onthetray,
`tray and dental elements/
`Askthe patient to keep the mouth open during the
`preparations.
`Patient grinding with the tray between the arches,
`impression.
`Removal of the material before complete
`Use a custom tray.
`hardening.
`Use a combination putty/light-body or two-phase
`Accentuated undercuts.
`technique,
`With silicone impressions, do notdirectly touch the
`Inadequate displacementof the gingival margin
`material with the gloves
`(intrasulcular area tootight).
`Contamination
`Use a high-tear-strength material.
`Use of a material with low tearresistance.
`Correctly displace the soft tissue.
`
`Lacerations/tears
`
`Delaminations
`
`Lack of coordination of the curing time between
`the high- and low-viscosity materials.
`Contamination between the delaminated layers.
`High ambient temperature.
`
`Followthe recommendations of the manufacturer
`regarding processing times:
`Perform maneuvers for control of hemostasis and
`retraction; prevent contamination between heavy-
`and light-bodylayers.
`Cool the impression material.
`
`Table 2. Causes and solutions for other commondefects found in conventional impressions
`
`0013
`
`0013
`
`

`

`! CHAPTER 3
`
`
`
`
`
`
`
`{
`
`away from the preparation area, distortions, de-
`fects caused by blood orsaliva, exposure of the
`tray, incomplete setting of impression material,
`poor bond between the tray and wash material,
`and discrepancies on the cast (Figs 9 to 11).
`Also, whatis dane after a conventional impression
`is taken might be a cause of inaccuracies; inade-
`quate disinfection may affect surface quality, detail
`reproduction, and dimensional Stability.
`In
`fact,
`before casting and/or providing the impression to
`the dental
`technician, the office must have spe-
`cific protocols for disinfection. The manufacturer's
`instructions should be consulted to determine
`which disinfection products will not damage the
`impression, Unfortunately,
`studies have found
`that the percentage ofclinicians who perform this
`procedure with care is low. In some countries, this
`figure is as low as 57%,but the factors that prevent
`compliance with guidelines are not understood."
`
`¢
`
`The various clinical decisions made during the
`protocol are essential for the accuracy of the
`impression, such as:
`* The choice of tray and adhesivein relation to
`the material used helps to prevent detach-
`ment of the material from the tray:
`in fact,
`even removal from the oral cavity may cause
`problems of deformation.
`The quality of the impression material cho-
`sen can greatly affect the surface of the
`hardenedplaster.
`Prior to casting, it is necessary to eliminate
`the anatomical undercuts, allowing easy de-
`tachmentof the cast without deformation of
`the impression.
`The most commonclinical errors can be identi-
`fled as incomplete reproduction of the intraoral
`situation, voids and tearing at the preparation
`margins, wash material displaced or washed
`
`*
`
`Figs 9 to 11. Problems
`can occur and sometimes
`cannotbe resolved, such
`as incomplete hardening
`of the material, exposure
`of the tray, an improper
`mixture of light- and
`heavy-body material, or
`absolute inaccuracy of
`details.
`
`Figs 12 to 14, Poor bond
`betweenthe tray and wash
`material, lack of impression
`details, and inappropriate
`methodsof storing and
`transporting are causes of
`lack of accuracy in thefinal
`conventional impression.
`
`0014
`
`
`
`0014
`
`

`

`THE DIGITAL IMPRESSION |
`
`
`
`
`room temperature
`Storing the impression at
`avoids deformations. A low storage temperature,
`for example, prolongs the setting reactions and
`changes the viscosity of the material, affecting
`the surface quality (detail reproduction) and di-
`mensional stability.
`It is always recommended to rinse the polyether
`impressions with water and dry them before
`sending them to the laboratory, avoid putting
`them in a bag along with alginate impressions,
`and store them away from direct sunlight to pre-
`vent a reduction in the impression quality.
`Transporting the impression to a commercial
`dental laboratory subjects an impression to sig-
`nificant variations in temperature. A temperature
`variation from 4°C to 40°C has been shown to
`result in a 1- to 18-mm dimensional change.”
`Moreover, during the time between securing an
`impression and the pouring stone cast, the am-
`bient temperature, the surface wettability, and
`disinfection procedures may result in additional
`distortion.'®"°
`Cast production is another step that might lead
`to uncontrolled expansion of the cast, bubbles,
`and fractures. It is obvious that if these imper-
`fections were located on critical areas, such as
`the preparation margins and the axial and oc-
`clusal surfaces of the abutments, the restoration
`would notfit properly. There are, in the tradition-
`al approach, different
`impression techniques
`
`classified according to the timing with which the
`materials are used and the consistency of the
`materials themselves.
`It is important that the dentist has an in-depth
`and detailed knowledge of the various tech-
`niques order to move toward the most suitable
`one for the clinical situation at hand (Figs 16
`
`and 17).
`
`Figs 15 and 16. Exampies of
`inaccuraciesin the production of
`the plaster cast include voids in the
`plaster cast, giving the appearance
`of a golf bali, and voids at the finish
`line and on the incisal edges of the
`abutment.
`
`
`
`0015
`
`0015
`
`

`

`4
`
`
`
`
`
`| OHAPTER 3
`
`Figs 17 to 19.Final
`polyether impression to
`restore a case with ceramic
`veneers.
`
`_
`
`the impression is
`the main roles of
`One of
`to record the details of
`the preparations and
`neighboring structures in their entirety, eg, over-
`preparation in case of shoulderfinish lines and
`to record the architecture of the gingival tissues
`(Figs 17 to 21). That is why taking an accurate
`and detailed final impression is a crucial step in
`creating a successful prosthetic rehabilitation.
`Having a protocol for taking impressions is man-
`datory and should consider the following:
`1. Ensure healthy soft tissue at the level of the
`prosthetic abutment.
`2. Ensure adequate retraction of the marginal
`soft tissue with mechanical and/or chemical
`
`If chemical agents are used,
`procedures.
`rinse and dry thoroughly.
`3. Choose an appropriate tray and viscosity of
`wash materials as well as proper working
`times (regular or quick) according to the im-
`pression technique and indications.
`4, Use a properly fitting, rigid, and sturdy im-
`pressiontray.
`5, Thoroughly apply tray adhesive andletit dry
`appropriately (for at least 15 minutes) before
`taking the impression.
`
`10.
`
`tt.
`
`12.
`
`13.
`
`14.
`
`96
`
`0016
`
`Ensure uniform and homogenous mixing of
`material (le, using automatic mixers).
`Fill tray sufficiently with impression material
`without trapping air bubbles,
`Use gloves that do not inhibit the setting of
`the impression material.
`Have separate timers to check the working
`time (2 to 2.5 minutes) and the hardening
`time (5 to 6 minutes).
`Avoid air entrapment during intraoral syring-
`ing of the wash material by immersing thetip
`in the material.
`
`Apply controlled vertical pressure upon seat-
`ing the tray to avoid contact between teeth/
`tissue and the bottom of the tray with a verti-
`cal movement.
`
`Movethelight-body materialinto the gingival
`sulcus with a puff of air and coverall of the
`abutments with the light-body material, start-
`ing with the nonvital tooth preparations and
`implant abutments.
`Avoid any movements that could shift the
`position of the tray and lead to distortions.
`Stay within the working time of the tray and
`wash materials.
`
`
`
`0016
`
`

`

`
`
`THE DIGITAL IMPRESSION |
`
`
`
`
`
`Figs 20 and 21. Final
`polyether impression for a
`complex periodontal case
`involving prepared teeth
`and implants.
`
`Fig 22.Digital
`impressions are as
`sensitive to blood and
`moisture astraditional
`impressions; therefore, soft
`tissues must be healthy.
`
`15.
`
`16.
`
`17,
`
`18.
`
`19,
`
`20.
`
`21.
`
`22,
`
`Use the correct protocol to remove the tray
`from the mouth, depending on where the
`abutments are located.
`
`When removing the tray from the mouth,
`avoid unilateral rotation.
`
`Verify that, on all surfaces, the tray does not
`show through the impression material, which
`would indicate that the tray came in contact
`with the hard or soft tissues and there will be
`
`an inaccuracyin that area.
`Make sure thatthe tray is not exposed, which
`would mean that the tray is in contact with
`the tooth structures or soft tissues and the
`information recorded would not be accurate.
`
`Check for proper blending between the tray
`and wash materials as well as a proper bond
`
`to the tray.
`Disinfect
`the impression according to the
`manufacturer's instructions for use,
`After disinfection, rinse the impression with
`water and dryit before sending it to the lab,
`Exact brand of impression material and dis-
`infection protocol must be communicated to
`the dental laboratory,
`
`Digital impressions in the
`literature
`All digital impression systems and chairside CAD/
`CAMsystemsrely on the ability to accurately re-
`cord the intraoral data file, and there are a couple
`of principles that are common to all the cameras
`that significantly influence the outcome;
`1. Digital impressions are as sensitive to mois-
`ture contamination as traditional impression
`
`materials. Blood and saliva obscure the sur-
`
`face of the tooth and dentogingival margins
`from the camera and prevent an accurate
`recording. At best,
`the camera records
`the moisture as a false surface contour; at
`worst, no data is recorded where moisture
`has collected. In either situation, an accurate
`restoration cannot be fabricated.
`
`. A second principle is that inadequate man-
`agement and retraction of soft tissues may
`prevent visualization of the marginal areas,
`resulting in an inaccurate recording with the
`camera. As desirable as it may be to scan
`through soft tissues, this is not possible with
`current systems. Digital cameras can only re-
`cord data thatis directly visible to the camera
`lens!(Fig 22).
`
`
`
`97
`
`0017
`
`0017
`
`

`

`
`
`
`| CHAPTER 3
`
`
`
`Fig 23. Clinical situation of
`central and lateral incisor
`preparations immediately
`before digital impression
`taking. Note the presence
`of fine powder on the scan
`area to bring uniformity to
`the differing reflectivity of the
`surfaces.
`
`Figs 24 and 25. Scannable
`impression coping in place
`on the study cast(Fig 24) and
`virtual model (Fig 25) from
`a digital impression (iTero).
`Reprinted from Lee and
`Gallucci** with permission.
`
`98
`
`Several studies investigated the efficiency and accu-
`racy of the digita! impression in tooth-supportedfixed
`prostheses.2'2 Recently more standardized and
`randomized studies have been published, for exam-
`ple, one by Syrek et al?* evaluating ceramic crowns
`produced from a totally digital process, which re-
`vealed that the crowns from intraoral scans featured
`significantly improved marginal fit and interoroximal
`contact area compared with crownsfabricated from
`a silicone impression, while both groups performed
`equally well with regard to occlusion.
`
`at Bologna
`In 2011, Monaco and colleagues
`Universityperformed clinical trials to test the ac-
`curacy of single all-ceramic zirconia crowns result-
`ing from a digital
`intraoral
`impression with active
`wavefront sampling technology by measuring the
`marginal and internal fits of the crowns and found
`that the single crowns obtained from the digital work
`flow presented enough accuracy to be used as an
`alternative to the traditional one.
`
`In 2013, Almeida ¢ Silva et al?* published a compar-
`ative analysis of four-unit zirconia fixed dental pros-
`theses based on digital and conventional techniques,
`revealing that while both groups showed clinically
`acceptable marginal fit, frameworks fabricated from
`
`
`
`0018
`
`
`
`a)
`
`
`
`a Cigital impression demonstrated better internal fit
`compared with those fabricated from a conventional
`impression,
`More specifically, reviewing each retainer face, the
`digital impression showed better marginal andinter-
`nalfit at the premolar mesial and molardistal faces.
`As for the efficiency, accuracy, and clinical viability
`of digital impressions for implant restorations, there
`have not been any standardized and randomized
`clinical studies. In this specific context, validation of
`DDT is paramount to understanding the impact of
`this new technology in terms of modifying well-es-
`tablished traditional protocols.
`During the last decades,
`implant dentistry has be-
`come fully integrated into prosthetic patient treat-
`ment and dental reconstruction. The dental implant
`industry has started to develop tools thatfacilitate the
`use ofintraoral scanners to makedigital impressions
`of cental implants.
`Despite the deformation of impression materials’
`anc the cast,*”*8 the work flow for conventional im-
`pression taking for implant restorations has proven
`itself in clinical practice .2*
`The introduction of scannable impression copings,
`however, now enables the useof intraoral scanners
`as an alternative to conventional impression taking,
`Del Corso et al®? shawed in an in vitro study that
`intraoral scans could be a valid alternative to ana-
`logue impression taking. A recent clinical study by
`Karl et al®* showed that the intraoral digitization of
`dental
`implants appears to be at least as precise
`as conventional impression taking and master cast
`fabrication using prefabricated transfer components
`and laboratory analogs.
`In their 2013 publication, Lee and Gallucci* evaluat-
`ed theefficiency, difficulty, and operator’s preference
`
`
`
`
`
`0018
`
`

`

`
`
`
`
`THE DIGITAL IMPRESSION |
`
`impressions compared with conventional
`imoressions for single implant restorations. An in-
`teresting aspect of this study was that participants
`were dental students with no previous exposure to
`conventional or digital
`implant
`impression taking.
`This homogenous group allowed investigation of
`the efficiency of these impression techniques in an
`objective and nonbiased manner.
`This is of particular importance since results from a
`different study population including experienced cli-
`nicians may have beendifficult to interpret. Moreover,
`a conventional (closed tray impression) protocol was
`used, which is less accurate but easier to learn than
`the open-tray impression (Figs 24 and 25). The con-
`clusions of this study were that digital impressions
`resulted in a more efficient technique