Chapter 84 Digitally Assisted Implant Surgery










C H A P T E R 8 4
Digitally Assisted
Implant Surgery
Daniel H. Etienne, Raymond R. Derycke, Perry R. Klokkevold
CHAPTER OUTLINE
Digitally Assisted Implant Surgery
Conclusion
The surgical procedures for the placement of implants have more or
less remained the same since the introduction of osseointegrated
dental implants. Briefly, implant placement surgery involves the
elevation of a full-thickness flap to expose bone; a sequential series
of drills with increasing diameters is used with profuse irrigation to
prepare a precise implant site osteotomy in the bone (see Chapter
78). The site is prepared, and the implant is positioned in a manner
that avoids important anatomic structures, such as the inferior
alveolar nerve, sinus cavities, and teeth. The ultimate goal is to
position the implant for optimal functional support of the planned
prosthetic tooth replacement(s) with proper emergence and natural
aesthetics.
Clinicians determine implant positions based on presurgical
4481

diagnostic imaging, study models, and the use of a diagnostic wax-
up of the planned tooth replacement(s). The final position of the
implant(s) results from the surgeon's interpretation of diagnostic
information and his or her ability to translate that information to
the patient at the time of surgery. A conventional surgical “guide”
is typically an acrylic stent, fabricated by a laboratory technician,
that is positioned in the mouth and used to direct drills through
openings in proposed tooth sites. It may or may not have precise
guide channels for implant positioning. The clinician uses the guide
along with his or her interpretation of diagnostic information,
clinical experience, and surgical skills to place the implant(s). The
use of a conventional surgical guide has several limitations and
potential sources of error, including inaccuracies in the stent during
fabrication, movement of the stent during surgery, and variations in
the clinician's use of the stent, which can lead to imprecise implant
positioning.
Advances in implant surgical technology include simulation
software, computer-generated surgical guides, and real-time digital
tracking or guidance.
• Implant planning or simulation software is used
preoperatively with the patient's scan data to
“simulate” implant placement into a virtual
patient. The software allows the clinician to view a
three-dimensional (3D) computer image of the
patient's jaw created from the computed
tomography (CT) or cone beam CT (CBCT) scan
data.
46
• Computer-generated surgical guides with drill
sleeves are produced using various techniques
from the presurgical “virtual” implant placement
data. These guides are used to place implants
more accurately based on the “planned”
locations.
18,28,38
4482

• Digitally assisted implant surgery or real-time
micro positioning implant surgery (RTMIS) uses
simultaneous tracking and “guidance” of the
implant instrumentation to follow the planned
treatment accurately during surgery.
10
Computer
imaging from scan data is observed interactively
with implant placement instrumentation during
the surgical procedure.
This chapter provides an overview of the terminology, technical
requirements, and limitations of digitally assisted implant surgery.
Digitally Assisted Implant Surgery
Real-Time Micro Positioning Implant
Surgery: Overview
RTMIS is the most sophisticated and perhaps the most promising of
these technologies because it has the greatest potential to reduce
surgical time, minimize surgical invasiveness, and result in a more
precise translation of implant planning to the actual surgical
procedure.
6,22,45
However, as with many newer technologies,
conflicting reports regarding its accuracy exist.
24,42
The
computerized surgical and prosthetic chain of treatment requires
precision at many levels.
33
Uses and Requirements
Computerized navigation surgery evolved from early applications
in neurosurgical procedures and continues to evolve today with
applications in many surgical specialties.
36,39
Clearly, the principal
advantage of using a computer to assist surgery is the precision it
offers. Moreover, real-time safety control is obtained with multiple
imaging sources facilitating a minimally invasive approach to
surgical procedures. As in medicine, 3D imaging is used in
dentistry to facilitate presurgical planning and to guide the surgical
4483

procedure. In the case of implant surgery, this allows precise
implant positioning while avoiding injury to nearby important
anatomic structures. Computers have been used to enhance dental
implant surgery in a variety of ways, from simple imaging software
used to visualize implant positions in a 3D virtual patient to more
complex, simultaneous image monitoring and instrument
navigation used to perform the surgery.
10,19
As an example, the aerospace industry uses computer assembling
software with augmented reality and real-time stock management
to reduce complete assembly time of an Airbus A350 aircraft by
30%.
20,21
Similarly, in dentistry, the goals of computer-assisted
implant placement are to reduce surgical time, enhance precision,
and facilitate prosthetic treatment by combining real-time surgical
navigation with computer-aided design (CAD) and computer-aided
manufacturing (CAM).
The European Commission (EC) has established a Global Medical
Device Nomenclature and an internationally agreed-on
classification system for medical devices with four classes from low
risk to high risk. The Food and Drug Administration (FDA) in the
United States has a Unique Device Identification for the registration
of medical devices with three classes from low to middle and high
risks.
• Class 1 medical devices are deemed low risk and
are therefore subject to the least regulatory
control. They do not need to be evaluated by a
certified body. In dentistry, a computer-generated
surgical guide is considered a class 1 medical
device. Regulation committees do not categorize it
as an assisting device.
• Class 2 medical devices are a higher risk than
class 1. The EC class 2 is subdivided into class 2A
and class 2B, where 2A is an assisting device
without automation and 2B is a device with
automatic assisting. Real-time micro positioning
4484

(RTM) device is a class 2 FDA or class 2A EC. In
contrast to a class 1 medical device, a class 2 or 2A
medical device must show innovation and
improvement of a clinician's decision making and
offer new evidence of benefit to the patient.
The use of RTMIS requires an accurate alignment (identification
and registration) of the patient anatomy with the patient's
volumetric data obtained from radiographic imaging (CT scan,
CBCT data) and through a tracking system with a 3D contact probe
or ultrasound 3D mapping (Fig. 84.1). The system allows matching
between imaging and real patient positions, and it permits tracking
of the precise movements of the surgical instrumentation (e.g.,
handpiece, drills) in relation to the actual patient. Various
modalities have been developed to acquire and register image data
and to coordinate and track movements.
6
FIG. 84.1 Dental implant real-time navigation system
(Open Pilot System, Stereovision Haptitude) with
4485

infrared stereovision cameras and a monitor display
showing the three-dimensional ultrasonic
reconstruction of a mandible with the planed implant
position in a coronal and a panoramic view. On the
panoramic view, a two-dimensional x-ray film is
overlaid on the ultrasonic image. (Courtesy Haptitude.)
Sequence of Steps
The clinical sequence of steps (Fig. 84.2) required for conventional
RTMIS is as follows:
FIG. 84.2 Assisting data chain with real-time micro positioning
implant surgery. The basic setup for a navigation system consists of
stereovision cameras with several tools: (1) infrared receptor allows
real-time patient tracking; (2) the contra-angle probe and the
ultrasound probe have markers that are tracked in real time by the
cameras; (3) ultrasound three-dimensional (3D) mapping shows bone
surface and adjacent root morphology; (4) computer-aided design and
computer-aided manufacturing (CAD/CAM) registered with ultrasound
and computed tomography (CT) scan; and (5) extraoral scanning for
matching other 3D imaging.
4486

1. Data acquisition. The patient is scanned for image data
acquisition with fiducial (artificial) radiographic markers
(e.g., stent with markers or intentionally placed pins or
screws into jaw) or anatomic (natural) markers such as teeth
or bony landmarks. If fiducial markers are placed in a stent,
the patient must have the stent in place when scanned.
2. Identification. The anatomic or fiducial markers are identified
with a probe tracked by the system. If markers were
incorporated into a radiographic stent, the stent will again
be placed in the mouth, and the markers will be identified
by hand with a probe tracked by the stereovision system.
3. Registration. After identification of the predetermined
markers, the software indicates the best localization or
“match” on the arch between the image data and the
patient. An invalidated registration may be caused by an
improper initialization or CT scan data.
4. Navigation. Ultimately, the operator is able to visualize
surgical instrument navigation (movement). The drilling
instruments are guided to a target point of impact with a 3D
spatial orientation.
5. Accuracy. Sustained accuracy procedures are critical during
surgery and should prove the reliability of the system's
overall accuracy. This sustained accuracy procedure is
completed by contacting the handpiece or drill on selected
teeth while visualizing markers, which can be viewed by the
stereovision system.
6. Feedback. Variations from the ideal position can be restricted
by the software through inactivation of the drill (stop-and-
go action) or by an audible or visual cue.
Key Fact
Real-time micro positioning implant surgery requires an accurate
alignment of the patient's anatomy with the patient's volumetric
data from radiographic imaging (computed tomography scan, cone
beam computed tomography data). A tracking system with a three-
4487

dimensional contact probe or ultrasound three-dimensional
mapping is used for identification and registration.
Data Acquisition and Registration
CT scans and CBCT scans are widely used for 3D imaging of
patients (see Chapter 76). Factors that must be considered when
deciding to use a CT scan include radiation exposure, limitations in
accuracy, and the possibility of diffracted images as a result of
metallic restorations. The evolution of scanner technology (spiral
CT scan, CBCT scan) has made it possible to reduce the radiation
dose to the level of a conventional panoramic radiograph while
maintaining adequate diagnostic quality for preoperative implant
planning.
11,15
Radiographically identifiable markers are important for RTMIS
just as they are for implant planning with conventional diagnostic
methods. However, unlike conventional planning, in which
orientation and simulation of implant positions are related to the
planned prosthetic crown positions, RTM markers must relate the
image data to the actual patient's anatomy. In other words, the
position of the surgical instrumentation (and ultimately the drills
and the implant) must be related to the scan image data of the
patient's jaw morphology and the image data must be precisely
aligned with the actual patient's anatomy. Thus, it is critically
important to scan the patient with markers that are identified in the
scan and correlated with the patient. Correlation between the scan
and the patient's markers is called registration. This process is a
statistical matching from point to point, point to surface, or surface
to surface. CBCT scans present less diffraction with metal, and
registration is easier than with CT scans.
A 3D localization of the template is made with different methods
of registration. The operator contacts the marker on the template
with an instrument that is seen by the system camera. RTM data are
obtained when these markers are attached to the patient.
The operator needs to validate whether the template and the
patient are correlated in a true position because deviations may
result due to mathematic formulations of the data in the registration
process. This critical step is used to control the accuracy of the
4488

patient's position. In the absence of a template, anatomic markers
such as teeth or specific bony landmarks and/or artificial markers
(fiducial) such as small tacks or screws that are secured in the bone
can be used. The operator checks the accuracy with a pointer
instrument that has its own markers used to touch different sites of
the mouth. The precision is visualized by localization of the images
on the screen and the real position of the instrument in the patient's
mouth.
Key Fact
The orientation of surgical instrumentation (i.e., drills) must be
related to the scan image data of the patient's jaw morphology, and
the image data must be precisely aligned with the actual patient's
anatomy. The critically important correlation between scan data
and the actual patient is called registration. Markers in the scan are
matched with markers in the patient by using a point-to-point,
point-to-surface, or surface-to-surface method.
Navigation and Positional Tracking
Numerous commercial products exist for navigation or positional
tracking, but few meet the computer-aided surgery (CAS)
requirements in terms of accuracy
8,48
(approximately 0.1 mm at a
distance of 1 m
4
), reliability, and clinical usability. The “real-time”
navigational technology is based on global positioning system
technology.
41
Some of the technologies used in medical CAS to track
movement include mechanical, magnetic, and optical tracking
systems.
Mechanical tracking systems use a six-axis coding robot with a
passive arm. The system is very reliable and highly accurate but has
limitations when more than one instrument or patient marker needs
to be located. Thus mechanical tracking is less desirable for implant
CAS, which requires the use of several different instruments and
multiple markers.
Magnetic tracking systems use a magnetic source and a field
receiver. The system loses accuracy in the presence of magnetic
field interference. Relative inaccuracies result from changes in the
4489

magnetic field, which may be caused by any metallic mass that may
be present, such as a drill motor (with or without activation).
3,4
Thus
the obligatory presence of drill motors in the operating room
during implant surgery makes magnetic trackers impractical for
implant CAS.
Optical tracking systems are recognized for their dependability and
accuracy. Positioning is made by intersecting the vision plane
between two or three cameras to locate markers with stereovision.
A passive system absorbs and processes ambient light, whereas an
active system interprets reflected light.
Active markers with infrared light–emitting diodes (IREDs) have
been widely used with superb accuracy but are sensitive to
reflections and interference with the line of sight between the IRED
markers and the cameras.
25,31
Although variations in optical
localizers are adequate for medical applications,
1,12
they need to be
improved for use in dental implant surgery. This is particularly
problematic with the typical seating arrangement of surgeon and
assistant (i.e., the direct line of sight to the cameras may be
interrupted by the operators). A stereovision with natural-light
cameras is a less expensive alternative compared with IREDs.
However, natural-light systems are more sensitive to surrounding
light, background, and the shape of markers. In comparison,
infrared cameras are less sensitive to these light variations.
With optical tracking devices, the surrounding light in the
operating room is important, and the choice of an infrared tracking
device is more relevant. Patients' motion will be tracked efficiently
if the marker is stable during surgery. In case of loose teeth or
unstable markers, cortical bone screws should be used.
External Viewer, Augmented Reality, and
Three-Dimensional Projection Screens
Once registration between the data and the actual patient has been
established, the instrumentation can be coordinated with the
system and observed by the surgeon or operator (Figs. 84.3 and
84.4). Instrument movement relative to the image data (and through
registration to the patient) may be viewed on an external monitor,
visually projected in the surgeon's field of vision (resulting in a
4490

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C H A P T E R 8 4Digitally AssistedImplant SurgeryDaniel H. Etienne, Raymond R. Derycke, Perry R. KlokkevoldCHAPTER OUTLINEDigitally Assisted Implant SurgeryConclusionThe surgical procedures for the placement of implants have more orless remained the same since the introduction of osseointegrateddental implants. Briefly, implant placement surgery involves theelevation of a full-thickness flap to expose bone; a sequential seriesof drills with increasing diameters is used with profuse irrigation toprepare a precise implant site osteotomy in the bone (see Chapter78). The site is prepared, and the implant is positioned in a mannerthat avoids important anatomic structures, such as the inferioralveolar nerve, sinus cavities, and teeth. The ultimate goal is toposition the implant for optimal functional support of the plannedprosthetic tooth replacement(s) with proper emergence and naturalaesthetics.Clinicians determine implant positions based on presurgical4481 diagnostic imaging, study models, and the use of a diagnostic wax-up of the planned tooth replacement(s). The final position of theimplant(s) results from the surgeon's interpretation of diagnosticinformation and his or her ability to translate that information tothe patient at the time of surgery. A conventional surgical “guide”is typically an acrylic stent, fabricated by a laboratory technician,that is positioned in the mouth and used to direct drills throughopenings in proposed tooth sites. It may or may not have preciseguide channels for implant positioning. The clinician uses the guidealong with his or her interpretation of diagnostic information,clinical experience, and surgical skills to place the implant(s). Theuse of a conventional surgical guide has several limitations andpotential sources of error, including inaccuracies in the stent duringfabrication, movement of the stent during surgery, and variations inthe clinician's use of the stent, which can lead to imprecise implantpositioning.Advances in implant surgical technology include simulationsoftware, computer-generated surgical guides, and real-time digitaltracking or guidance.• Implant planning or simulation software is usedpreoperatively with the patient's scan data to“simulate” implant placement into a virtualpatient. The software allows the clinician to view athree-dimensional (3D) computer image of thepatient's jaw created from the computedtomography (CT) or cone beam CT (CBCT) scandata.46• Computer-generated surgical guides with drillsleeves are produced using various techniquesfrom the presurgical “virtual” implant placementdata. These guides are used to place implantsmore accurately based on the “planned”locations.18,28,384482 • Digitally assisted implant surgery or real-timemicro positioning implant surgery (RTMIS) usessimultaneous tracking and “guidance” of theimplant instrumentation to follow the plannedtreatment accurately during surgery.10 Computerimaging from scan data is observed interactivelywith implant placement instrumentation duringthe surgical procedure.This chapter provides an overview of the terminology, technicalrequirements, and limitations of digitally assisted implant surgery.Digitally Assisted Implant SurgeryReal-Time Micro Positioning ImplantSurgery: OverviewRTMIS is the most sophisticated and perhaps the most promising ofthese technologies because it has the greatest potential to reducesurgical time, minimize surgical invasiveness, and result in a moreprecise translation of implant planning to the actual surgicalprocedure.6,22,45 However, as with many newer technologies,conflicting reports regarding its accuracy exist.24,42 Thecomputerized surgical and prosthetic chain of treatment requiresprecision at many levels.33Uses and RequirementsComputerized navigation surgery evolved from early applicationsin neurosurgical procedures and continues to evolve today withapplications in many surgical specialties.36,39 Clearly, the principaladvantage of using a computer to assist surgery is the precision itoffers. Moreover, real-time safety control is obtained with multipleimaging sources facilitating a minimally invasive approach tosurgical procedures. As in medicine, 3D imaging is used indentistry to facilitate presurgical planning and to guide the surgical4483 procedure. In the case of implant surgery, this allows preciseimplant positioning while avoiding injury to nearby importantanatomic structures. Computers have been used to enhance dentalimplant surgery in a variety of ways, from simple imaging softwareused to visualize implant positions in a 3D virtual patient to morecomplex, simultaneous image monitoring and instrumentnavigation used to perform the surgery.10,19As an example, the aerospace industry uses computer assemblingsoftware with augmented reality and real-time stock managementto reduce complete assembly time of an Airbus A350 aircraft by30%.20,21 Similarly, in dentistry, the goals of computer-assistedimplant placement are to reduce surgical time, enhance precision,and facilitate prosthetic treatment by combining real-time surgicalnavigation with computer-aided design (CAD) and computer-aidedmanufacturing (CAM).The European Commission (EC) has established a Global MedicalDevice Nomenclature and an internationally agreed-onclassification system for medical devices with four classes from lowrisk to high risk. The Food and Drug Administration (FDA) in theUnited States has a Unique Device Identification for the registrationof medical devices with three classes from low to middle and highrisks.• Class 1 medical devices are deemed low risk andare therefore subject to the least regulatorycontrol. They do not need to be evaluated by acertified body. In dentistry, a computer-generatedsurgical guide is considered a class 1 medicaldevice. Regulation committees do not categorize itas an assisting device.• Class 2 medical devices are a higher risk thanclass 1. The EC class 2 is subdivided into class 2Aand class 2B, where 2A is an assisting devicewithout automation and 2B is a device withautomatic assisting. Real-time micro positioning4484 (RTM) device is a class 2 FDA or class 2A EC. Incontrast to a class 1 medical device, a class 2 or 2Amedical device must show innovation andimprovement of a clinician's decision making andoffer new evidence of benefit to the patient.The use of RTMIS requires an accurate alignment (identificationand registration) of the patient anatomy with the patient'svolumetric data obtained from radiographic imaging (CT scan,CBCT data) and through a tracking system with a 3D contact probeor ultrasound 3D mapping (Fig. 84.1). The system allows matchingbetween imaging and real patient positions, and it permits trackingof the precise movements of the surgical instrumentation (e.g.,handpiece, drills) in relation to the actual patient. Variousmodalities have been developed to acquire and register image dataand to coordinate and track movements.6FIG. 84.1 Dental implant real-time navigation system(Open Pilot System, Stereovision Haptitude) with4485 infrared stereovision cameras and a monitor displayshowing the three-dimensional ultrasonicreconstruction of a mandible with the planed implantposition in a coronal and a panoramic view. On thepanoramic view, a two-dimensional x-ray film isoverlaid on the ultrasonic image. (Courtesy Haptitude.)Sequence of StepsThe clinical sequence of steps (Fig. 84.2) required for conventionalRTMIS is as follows:FIG. 84.2 Assisting data chain with real-time micro positioningimplant surgery. The basic setup for a navigation system consists ofstereovision cameras with several tools: (1) infrared receptor allowsreal-time patient tracking; (2) the contra-angle probe and theultrasound probe have markers that are tracked in real time by thecameras; (3) ultrasound three-dimensional (3D) mapping shows bonesurface and adjacent root morphology; (4) computer-aided design andcomputer-aided manufacturing (CAD/CAM) registered with ultrasoundand computed tomography (CT) scan; and (5) extraoral scanning formatching other 3D imaging.4486 1. Data acquisition. The patient is scanned for image dataacquisition with fiducial (artificial) radiographic markers(e.g., stent with markers or intentionally placed pins orscrews into jaw) or anatomic (natural) markers such as teethor bony landmarks. If fiducial markers are placed in a stent,the patient must have the stent in place when scanned.2. Identification. The anatomic or fiducial markers are identifiedwith a probe tracked by the system. If markers wereincorporated into a radiographic stent, the stent will againbe placed in the mouth, and the markers will be identifiedby hand with a probe tracked by the stereovision system.3. Registration. After identification of the predeterminedmarkers, the software indicates the best localization or“match” on the arch between the image data and thepatient. An invalidated registration may be caused by animproper initialization or CT scan data.4. Navigation. Ultimately, the operator is able to visualizesurgical instrument navigation (movement). The drillinginstruments are guided to a target point of impact with a 3Dspatial orientation.5. Accuracy. Sustained accuracy procedures are critical duringsurgery and should prove the reliability of the system'soverall accuracy. This sustained accuracy procedure iscompleted by contacting the handpiece or drill on selectedteeth while visualizing markers, which can be viewed by thestereovision system.6. Feedback. Variations from the ideal position can be restrictedby the software through inactivation of the drill (stop-and-go action) or by an audible or visual cue. Key FactReal-time micro positioning implant surgery requires an accuratealignment of the patient's anatomy with the patient's volumetricdata from radiographic imaging (computed tomography scan, conebeam computed tomography data). A tracking system with a three-4487 dimensional contact probe or ultrasound three-dimensionalmapping is used for identification and registration.Data Acquisition and RegistrationCT scans and CBCT scans are widely used for 3D imaging ofpatients (see Chapter 76). Factors that must be considered whendeciding to use a CT scan include radiation exposure, limitations inaccuracy, and the possibility of diffracted images as a result ofmetallic restorations. The evolution of scanner technology (spiralCT scan, CBCT scan) has made it possible to reduce the radiationdose to the level of a conventional panoramic radiograph whilemaintaining adequate diagnostic quality for preoperative implantplanning.11,15Radiographically identifiable markers are important for RTMISjust as they are for implant planning with conventional diagnosticmethods. However, unlike conventional planning, in whichorientation and simulation of implant positions are related to theplanned prosthetic crown positions, RTM markers must relate theimage data to the actual patient's anatomy. In other words, theposition of the surgical instrumentation (and ultimately the drillsand the implant) must be related to the scan image data of thepatient's jaw morphology and the image data must be preciselyaligned with the actual patient's anatomy. Thus, it is criticallyimportant to scan the patient with markers that are identified in thescan and correlated with the patient. Correlation between the scanand the patient's markers is called registration. This process is astatistical matching from point to point, point to surface, or surfaceto surface. CBCT scans present less diffraction with metal, andregistration is easier than with CT scans.A 3D localization of the template is made with different methodsof registration. The operator contacts the marker on the templatewith an instrument that is seen by the system camera. RTM data areobtained when these markers are attached to the patient.The operator needs to validate whether the template and thepatient are correlated in a true position because deviations mayresult due to mathematic formulations of the data in the registrationprocess. This critical step is used to control the accuracy of the4488 patient's position. In the absence of a template, anatomic markerssuch as teeth or specific bony landmarks and/or artificial markers(fiducial) such as small tacks or screws that are secured in the bonecan be used. The operator checks the accuracy with a pointerinstrument that has its own markers used to touch different sites ofthe mouth. The precision is visualized by localization of the imageson the screen and the real position of the instrument in the patient'smouth. Key FactThe orientation of surgical instrumentation (i.e., drills) must berelated to the scan image data of the patient's jaw morphology, andthe image data must be precisely aligned with the actual patient'sanatomy. The critically important correlation between scan dataand the actual patient is called registration. Markers in the scan arematched with markers in the patient by using a point-to-point,point-to-surface, or surface-to-surface method.Navigation and Positional TrackingNumerous commercial products exist for navigation or positionaltracking, but few meet the computer-aided surgery (CAS)requirements in terms of accuracy8,48 (approximately 0.1 mm at adistance of 1 m4), reliability, and clinical usability. The “real-time”navigational technology is based on global positioning systemtechnology.41 Some of the technologies used in medical CAS to trackmovement include mechanical, magnetic, and optical trackingsystems.Mechanical tracking systems use a six-axis coding robot with apassive arm. The system is very reliable and highly accurate but haslimitations when more than one instrument or patient marker needsto be located. Thus mechanical tracking is less desirable for implantCAS, which requires the use of several different instruments andmultiple markers.Magnetic tracking systems use a magnetic source and a fieldreceiver. The system loses accuracy in the presence of magneticfield interference. Relative inaccuracies result from changes in the4489 magnetic field, which may be caused by any metallic mass that maybe present, such as a drill motor (with or without activation).3,4 Thusthe obligatory presence of drill motors in the operating roomduring implant surgery makes magnetic trackers impractical forimplant CAS.Optical tracking systems are recognized for their dependability andaccuracy. Positioning is made by intersecting the vision planebetween two or three cameras to locate markers with stereovision.A passive system absorbs and processes ambient light, whereas anactive system interprets reflected light.Active markers with infrared light–emitting diodes (IREDs) havebeen widely used with superb accuracy but are sensitive toreflections and interference with the line of sight between the IREDmarkers and the cameras.25,31 Although variations in opticallocalizers are adequate for medical applications,1,12 they need to beimproved for use in dental implant surgery. This is particularlyproblematic with the typical seating arrangement of surgeon andassistant (i.e., the direct line of sight to the cameras may beinterrupted by the operators). A stereovision with natural-lightcameras is a less expensive alternative compared with IREDs.However, natural-light systems are more sensitive to surroundinglight, background, and the shape of markers. In comparison,infrared cameras are less sensitive to these light variations.With optical tracking devices, the surrounding light in theoperating room is important, and the choice of an infrared trackingdevice is more relevant. Patients' motion will be tracked efficientlyif the marker is stable during surgery. In case of loose teeth orunstable markers, cortical bone screws should be used.External Viewer, Augmented Reality, andThree-Dimensional Projection ScreensOnce registration between the data and the actual patient has beenestablished, the instrumentation can be coordinated with thesystem and observed by the surgeon or operator (Figs. 84.3 and84.4). Instrument movement relative to the image data (and throughregistration to the patient) may be viewed on an external monitor,visually projected in the surgeon's field of vision (resulting in a4490 superimposed visual image seen over the surgical field) by using ahead-mounted projection system or projected on a 3D projectionscreen (Fig. 84.5).47 In this manner, the image on the externalmonitor (see Fig. 84.4), the surgical field, or the 3D projection screen(Fig. 84.6) guides the surgeon to perform the planned procedure.FIG. 84.3 Global setup for surgical navigation. The basic setup for anavigation system consists of stereovision cameras with several tools.The contra-angle probe, the ultrasound probe, and the patient jig needto have markers, which are tracked by the cameras. The occlusal stent,with markers in the standard process and without markers inultrasound registration, used during computed tomography scanacquisition will be recognized in its three dimensions for prostheticplanning.4491 FIG. 84.4 Images of a computer screen and thesurgeon's view of computer-aided implant surgerynavigation simulated with a dry mandible. Duringnavigation, the surgeon concentrates on visual cuesseen on the eye viewer. (Courtesy Haptitude.)4492 FIG. 84.5 Dental implant real-time navigation systemwith infrared stereovision cameras and a three-dimensional monitor display showing thereconstruction of a computed tomography–scannedmandible.FIG. 84.6 Screen views available during surgery. Upper left, Thecomputed tomography (CT) scan reconstruction of the mandible and4493 teeth is observed in yellow. Surface mapping of bone and crownmorphology (dark green/blue) obtained from ultrasound or opticalscanner. The computer compares the data from the three-dimensional(3D) topography to the two-dimensional (2D) x-ray film. Lower left, The2D x-ray film is matched to a 3D topography of the patient's “matrix”with the simulated implant positions in green and red. Upper right, Thetarget and position of the drill and implant are observed. Lower right,Real-time navigation with a combination of superimposed images froma 2D x-ray film, optical scanner, CT scan, and 3D ultrasound scan.(Courtesy Haptitude.)Side viewers display target data in two dimensions and requirethe surgeon to look away from the surgical field. However, see-through viewers display target data transparently in the surgeon'sfield of view and allow the operator to observe the surgical fieldcontinuously. An augmented-reality viewer26 allows the surgeon tosee target data in three dimensions, superimposed over the surgicalsite through projected images in both eyes.49 The augmented-realitymethod allows the operator to adapt to the system more naturallyand therefore more rapidly, but it does not appear to haveadvantages over the use of two-dimensional (2D) side-viewerdevices in terms of accuracy.43 Both systems allow simultaneousviewing of virtual information of the implant (axis and target) and areal vision of the surgical site. Augmented-reality devices are verysensitive to calibration before surgery and require care andmonitoring intraoperatively to prevent misalignment duringsurgery. The relative stability of a headset is critical to maintainingaccuracy.Alternatively, 3D projection screens provide a “real 3D vision”viewed on a specialized monitor (see Fig. 84.5) without the need forviewers (i.e., operator glasses).Two types of 3D projection screens are available, as follows:1. The multiplane device has a screen that provides threesimulated real-time planes. The object is projected in thescreen with a back-field simulated projection. A planewithin the screen surface and the forward plane are at amaximum focus of 10 to 20 cm. This device provides a 3Dview that is extremely dependent on the shape.2. A newer-generation device uses nanolenses on each pixel ofscreen resolution. It provides a natural light-splitting effectsimilar to the effect of a natural eye separating the three4494 basic colors. Consequently, it is perceived as a natural view.A lateral displacement of the operator's head provides 8 to12 simulated views, which together create a natural“volume” effect. No adaptation time is required, andviewing is intuitive.This 3D projection screen technology cannot provide a trueholographic 3D view because of the eye's plane of focus on a flatscreen, but it does provide a 3D “real volumetric view.” The actual3D projected screen technology does not provide enough high-quality texture, but it is overviewed with simple shape symbols(e.g., cross, circle). Another difficulty is introduced by the nonlineardepth scale of the screen, which is perceived by the operator's brainas nonlogical and induces a decrease in intuitive hand localization.In addition to this improvement in 3D vision, a 3D sequence ofimages can be modified for specific applications such as navigation.For example, a 3D sequence of eight views can be modified tofacilitate the observation of a projected view of the object at 90degrees with a minimal head side shift of only 5 degrees. Thesereal-time, 3D front and side views provide intuitive 3D data viewsin spite of the 2D parameters used to visualize them.Technical Principles and LimitationsAn inaccuracy between the two positions is the real error of radiomarkers transformation (eFig. 84.1).17 Markers (not radio markers)in the template are localized with the tracking system, which allowsmeasurement of accuracy between registration and the truedimensions. This does not define range, direction, and level ofdistortion on all parts of the surgical field as a real patient's position(not the template position). To date, no strong test exists to evaluatethis error for RTMIS systems or between a computer-guidedtemplate and a patient's real position during a CT scan.4495 EFIG. 84.1 Sequence of treatment: chain data input and output.Cone Beam Computed Tomography and ComputedTomography Scan LimitationsAccuracy in depth at 1 m is around 0.5 mm, even with an opticallens distortion of 1%.23 If a software treatment is applied at asubpixel level, it will provide a gain of 1/5 of a pixel with anincidence of around 0.1 mm in height and width and around 0.5mm in depth and after treatment a maximal mean of 0.15 mm. Withthese characteristics, a 90-degree change in the axis of vision of thecameras between the data of an initial visit and the surgical timemay lead to a major inaccuracy >1 to 2 mm in depth or on sidepositioning by a leverage effect.The calibration process is temperature-dependant above 25 °C,and could result in several millimeters of deviation. Between longsurgical procedures, the system must be stopped to obtain atemperature decrease, and complementary metal oxidesemiconductors are more tolerant than charge-coupled devices.TrackersThe assembly of trackers on each tool is designed to be recognizedby the system as rigid bodies. An ultrasound probe is the only4496 instrument that should be designed for 360-degree trackingcapability, but the tracker has to be larger than in other systems,except with RTMIS that is CT based.The shape should prevent lack of accuracy in depth in all thebuccal and palatal positions where we do not need a 360-degreetracker, and it can be smaller on the contra angle. Small trackerswith 180-degree efficacy are more convenient in dentalimplantology or maxillofacial surgery with limited interferencefrom operator's hands and arms.Deformations of the rigid body may occur with the plasticframework after 100 sterilization cycles. Sensors placed on thetracker may be silicone, they can be disposable, or they can handle asterilization process if they are protected with a sterile shield. Onedifficulty during CT scan acquisition with a template is to avoid ashift not seen on the images but observed during surgery where adiscrepancy between the real position and the image on the screenis obvious. This is a major level of concern, and with CT-basedsoftware the operator has two solutions: perform the surgery in aclassic way without any guidance, or cancel the surgery and take anew CT scan, hopefully with a template in a proper position.Localization of radio markers, or a touch pad on a fiducial marker(like a LEGO brick8), is operator dependent with infraredstereovision.14,24,27 CT scan statistical variation after registration isestimated to be between 0.5 and 2 mm.A moderate level of concern is with full arch acquisition aftersegmented CBCT. The accuracy of radio markers' templateregistration will be less than with a full arch CT scan. A large spacebetween radiomarkers in the surgical field is a source of inaccuracy.A minor concern is the need to elaborate a special template orshape recognition (seen as a marker), with impacts on chair timeand cost.In orthopedics, computer-guided templates, prepositioned withan RTM system, have been used for the last 20 years. RTM indentistry allows increased control and security by precisepositioning of the template without any soft tissue opening and livecontrol of the template position during surgery.2 If bone fixation ofthe template is needed, the real-time obtained position is verifiedafter placement of lateral screws or the two or three initial implant4497 placements in cases of full arch reconstruction as long as the referralabutment supporting the patient's rigid body (markers) is notlinked in any way to the guide.Registration: A Mathematical ComplexityAfter scan acquisition, the 3D image data of markers or ultrasoundbone surface are identified by software as anatomic geometricelements. Then correlation (registration) between marker andsurface should be done with the tracking device and the trackedtool. The tracking device gives real-time patient and tool positionwith its axis. The patient's and localized marker or surface positionscould be placed into the patient's referral (fiducial). Several deviceshave been used to capture the actual patient's anatomy or fiducialmarker at surgery, including a touch pointer and an ultrasoundprobe. The touch pointer allows the operator to touch specificanatomic points (or fiducial markers), whereas an ultrasoundtracking device records multiple points of reference on a surface. Ahand pointer device is fairly accurate, but if the clinician is notcareful, the tendency is to define points that are not in contact witha real surface, thus creating false mapping. The ultrasound probehas a lower accuracy32 than the touch pointer presenting a maximal(Mx) deviation of 5% of the thickness tissue in the 5 MHz range (i.e.,0.05 mm inaccuracy with 10-mm soft palate tissue), but it has theadvantage of capturing continuous data of bone morphologythrough the mucosa or gingiva.29,40Three registration methods are used to match anatomic points ofthe preoperative image data and the intraoperative patient'sanatomy: (1) point imaging to patient's point, (2) surface to point,and (3) surface to surface. Point-based and line-based methods aredescribed here to illustrate the requirements for adequateregistration.In the point-based method, a few particular points are identifiedin the preoperative image data (anatomic points) or artificial(fiducial) markers and the patient's anatomy. Points must be welldefined and stable so that they can be precisely matched, and thecomputer calculates a transformation equation that minimizes themean distance between matched points to complete the registration.The registration accuracy can be predicted, depending on the4498 distribution of points (e.g., an equilateral tripod gives moreaccurate results than three colinear points).16,35With specific algorithms, a triangle in the preoperative set ofpoints and a triangle in the intraoperative set of points arecomputed, compared, and then registered. An average accuracy isaround 0.5 to 1 mm with an Mx deviation >2 mm with algorithmtype iterative closest point (ICP) modified (most common).Surface-to-surface methods are derived from point-basedmethods. All lines and surfaces measured on image planning (aftersegmentation of anatomic structure of the jawbone in the CT scan)and the points taken on the patient's anatomy by the trackingdevice are known as a set of points. These sets may be dense orsparse; a segmented bone surface may have hundreds or thousandsof points. When the segmented surface is dense, one can assumethat almost all points measured with the tracking device will beidentified as points of the segmented surface. Algorithms have beendeveloped to match preoperative and intraoperative data, but thenumber of possible errors in the identification process increasesdramatically with line-based or curve-based methods.34 Surface tosurface is the most accurate method by far, but it is still a veryoperative- and experience-dependent process.Tracking DeviceIdeally, a practitioner would like <0.3-mm accuracy due toprosthetic requirements. Without guidance, an operator may attain0.5-mm accuracy. RTM with magnetic trackers, ultrasound spacetracking, and an inertial system shows a mean deviation >0.3 mm.The combination computer-guided template and RTM has 0.3-mmaccuracy. Actual stereovision tracking or, in the future, a laserultrafast scanner will show a mean 0.1 mm accuracy on the contra-angle working tip. Nevertheless, laser scanning real-time systemsbased on shape recognition will need at least a frame rate of 15 to20/sec to be compatible with a real-time mode.In dentistry, cameras sensitive to an infrared range of 800 to 900nm are used to cope with the surgical light artifacts or the strongcontrast in light spots. Two cameras are used, and they have to besynchronized. More have around 4.5 µm of pixel size, with anaverage dimension of 1600 × 1200. Importantly, camera4499 specifications have to be adapted for a particular tracking deviceand the environment where the cameras will be used. A deviationof 0.1 to 2 mm may result from improper use.To illustrate these considerations, a distance range of 40 to 90 cmfrom the cameras to the patient's head is required, with the greatestaccuracy in the center field. The field of view must be sufficientlylarge to see most of the markers; if the number of markers isinsufficient, a deviation >2 mm may occur. In addition is the issueof dynamics; for example, rapid capture of a point of reference forregistration with a CT scan or a poor axis of view for cameras willproduce 0.3- to 2-mm inaccuracy. This is due to the speed offrames/second (f/sec). A speed acquisition imaging >40 f/secappears mathematically favorable (the normal speed of the humaneye is 15 f/sec), and algorithms matching CAD frames with othercaptured images perform more favorably in detecting tool positionin a relatively static position.One difficulty with cameras and real-time monitoring is that thepatient and instrument markers have to be seen at the same timewithout being covered by the contra-angle body, depending on thehead position and the surgical site. This situation is avoided whenthe cameras are placed in front of the patient, above the operator'shead, and with the use of a larger camera field.Cameras are accurate in height and width but less in depth,which is limited by the pixel size of the sensors.Clinical Advantages of RTMIS• Improved precision• Noninvasive implant surgery (without or withlimited flap reflection)• Reduced postoperative complications• Perspectives for improved prosthetic treatmentChallenges With RTMIS• Learning curve4500 • Time spent for preparing simulation (if done bythe surgeon)• Time spent for installation (but overall, surgeryis shorter)• CostBenefit of Ultrasound Mapping• Immediate chairside real-time 3D imaging• Data obtained at the same time as the patient'sposition• Absence of registration• Bone surface visualization, sinus floor, rootmorphology• Same accuracy as CBCT <0.3 mmAdvantages and Limitations of Bone UltrasoundMappingThe accuracy of a navigation system depends on the accumulatederrors due to the different components (eTable 84.1). Three-dimensional ultrasound mapping (bone, root) provides 3Dpositioning. The advantage of RTM ultrasound is to collect 3Ddata30 with an ultrasound probe tracked by cameras simultaneouslywhile splinted to the patient's arch. The patient's collected data areobtained from a known (real) position, and we do not needregistration (absence of mathematic errors).eTABLE 84.1Overall Technical Characteristics of One Real-Time Ultrasound-Based MicroPositioning System (Open Pilot System)Specifications Performances CommentsLength of time before initial use 15 min Waiting time needed before theprocedure to set up surgicalmeasurementsVolume of the working space (WS) 0.4m × 0.6m × Depth: minimal distance4501 (Depth × Height × Length = WS) 0.6mWS: maximum tracking depth valueNumber of three-dimensionalmeasures/sec12–30 Avoid speed movementTemperature 15°–35° C(59°–95° F)System internally cooledHumidity resistant <85% withoutcondensationOutside light source impact Not sensitive Exception made for other infraredsourcePrecision of calibrationRoot mean square (RMS)0.10 mm (0.12mm RMS)10,000 points of measure in the field ofviewMarker static statistical accuracy <0.10 mm (0.04mm RMS)60 measures at 75 cmRigid body (referral object) staticstatistical accuracy<0.10 mm (0.04mm RMS)60 measures at 55, 65, 75 cmMarker dynamic statistical accuracy <0.1 mm (0.05mm RMS)At 65 cm, speed <34 mm/secRigid body dynamic accuracy (with6 markers)<0.2 mm (0.05mm RMS)At 65 cm, speed <34 mm/secRigid body static absolute stability(Object A / Pointer)± 0.14 mm 30 measures per 15 mn, for 7 hr of useStatic rigid body differentialmeasure stability (Object A / ObjectB)± 0.06 mm 30 measures per 15 mn, for 7 hr of useLength of time of treatment frame 10 msec With Intel 2.0 GHz processorCaptor resolution 1024 × 768pixelsOptical lens Focal 4.5 mmCleaning method DisposabletissueTrackersComposed with passive spheres 6–9 spheres bytrackerInfrared passive sensorsView of tracking 180–360degreesDepending on complexityTherefore it can be used alone without x-ray download imaging,so global accuracy results only from the stereovision tracking (<0.3mm). Ultrasound mapping is a measuring device (the patient'sfiducial is known, and the tool positioning and axis are known inthe same patient's referral).In other systems, the results of registration are not a measure.They compare the initial position with the final position of a radiotemplate, but you do not know the real position of the initial radiotemplate. We can just appreciate that it is larger or smaller, but wedo not know the change in dimension.The RTM ultrasound accuracy is in the range of a CT scanner(without registration) when using precise monodirectionalultrasound with an Mx of 0.3 mm (identical to CT scan). A 5%4502 deviation through a 10-mm gingival thickness is demonstrated invivo in the medical field. The instrument of localization will retainthe tracking device precision, and the system is comparable to ametrology system, which is a gold standard of precision. When 3Dx-ray films and CAD or CAM are matched with ultrasound, we donot have any impact on the localization tool because the fiducial isalways the known patient's position at the initial recording visit andduring surgery. An RTM ultrasound error is a unique parallel chainof accuracy.The control of a patient's position is possible anytime duringsurgery, and the surgeon can easily verify the match between theactual patient's position and the initial recording time.The advantage is to overlay CT scan, periapical x-ray study,13,44 orCAD or CAM images and their potential errors on 3D ultrasoundmapping without affecting the accuracy of the localization tool thatis linked only to the ultrasound mapping. It can be used for largesurgical fields, and an accuracy of 0.3 mm is obtained for zygomaticmapping and registration. We do not have any information on thedistance between markers and the surgical field. If the operator iswilling to use a computer-guided template, RTM localization can beperformed, and displacement of the guide will be known in realtime.RTM ultrasound images are obtained in one visit, and it ispossible to obtain another data set of 3D bone imaging in 5 minutesif we have a displacement of markers during surgery or a change instrategy due to a quality in bone anatomy.One major limitation is that ultrasound surface mapping7 doesnot provide internal structure images, except root contours and thesinus floor, but a distance from the alveolar crest to the nerve canalcan be measured on 2D x-ray films and evaluated on a 3D mappingimage. Matching a CT scan or CBCT and 3D ultrasound mappingmay sometimes be challenging because the thin cortical alveolarbone may not be seen on x-ray films, and in these situations weneed some expertise to perform the registration process. Theoperator still has the ability to control the accuracy in real time withpointers and a surgical bur.Newer ultrasound by liquid cavitation allows measurements ofthe mandibular canal depth with 0.5-mm accuracy.4503 Ultrasound 3D mapping is technically sensitive and has alearning curve. Newer technologies are emerging in medicine,37such as supersonic ultrasound with a high dynamic frequency forDoppler, bone elastometry, inflammatory tissue applications, andphotoacoustic tomography that combines ultrasound andfemtosecond laser interferometry for bone and soft tissue Doppler-like applications. These newer techniques are expensive, and thesize has to be adapted for dental applications.Ultrasound is also efficient for prosthetic 3D mapping and crowncontouring. The accuracy stays in the limits of the tracking system(mean 0.3 mm).Similar to 3D ultrasound, a periapical x-ray film can be matchedwith 3D surface mapping obtained by a palpor instrument (with itsmarkers) directly on teeth or bone surfaces.System Risk AnalysisThe expected potential of computer-based implant surgery is for aninexperienced operator9 to place an implant with the same accuracyas an experienced surgeon. However, in practice, soft tissue andbone anatomic variations and the prosthetic treatment plan arebetter managed with more experience. Three parameters aredeterminants for FDA assisting device approval: safety, availability,and robustness.SafetyWe have mentioned that one difficulty is to appreciate that we arein the patient's real-time position. This consideration applies to acomputer-guided template, where the operator can visualize thediscrepancy with the ideal position, but the statistical error isunknown. Several studies consider that a comparison between aninitial CT scan with a postoperative CT scan evaluates a trueposition. In fact, we are comparing surface data with other surfacedata carrying the proper inaccuracy of each data set. With a CT scanobtained before surgery with a fixed computer-guided template,the operator can control the template position by RTM, and someother image technologies are applied, such as 3D ultrasound,palpor tracking, and object scanning in 3D in real time. CAD4504 imaging is promising, but the computing time is actually notcompatible with routine daily use. CAD and CAM (STL files) canintegrate an RTMIS chain with specific software and simulatetemporary prosthesis without a need for stone casts if the data onimplant shape are included in the RTM software planning.One alternative is to scan with the markers locked on the patient(software learning the shape and orientations of the markers) withthe prosthesis in place. CAD imaging, however, should be donewith an extraoral scan (and not intraoral) due to the need for moredata points obtained from the skin surface. An accuracy of 0.1 mmcould be expected with these technologies. The main advantagesare a chairtime session lasting around 5 to 10 minutes, avoidance ofx-ray studies, and verification that a template is in a true real-timeposition and a CAD scan will be obtained in occlusion.We can also register before surgery a CT scan with radiomarkerson the template and on the prosthesis. This is operator dependent,and in the case of CT scan artifacts, these images may be replacedby 3D data obtained with a palpor. The most efficient solution forthe final prosthetic framework is still to capture a CAD or CAMimplant in place at the end of the surgery.It appears that at less than 0.5 mm of precision and in totallyblind conditions, the operator should use a computer-guidedtemplate with real-time micro positioning implant surgery(RTMIS). This accuracy is needed when a risk exists of drilldeviation with cortical bone, a narrow ridge, absence of medullarbone, and anatomically challenging proximity.AvailabilityAn integrated digital chain of treatment is a medical system inwhich, after validation, a benefit value is obtained for the patientwith reduced practitioner operative dependence.No chairside or real-time limitation exists with 3D ultrasoundRTMIS because CT images are not mandatory. Bone 3D mappingcan be registered before the surgical session, and CT registration iselaborated automatically by the software. This presurgical time iscomparable to the one with shape recognition (i.e., LEGO shape)placed on a standard template. This solution allows the use of aconventional template for CT with, of course, the necessary time for4505 CT or CBCT capture and data download into the system.Surgeons are performing operations, and they want to minimizethe computing time before and during surgical procedures. Astrong demand for simplification has been expressed by clinicians.This is illustrated in daily practice by 3D ultrasound RTMIS userswho do not match CT scan and 3D ultrasound data but who prefer,as in conventional surgery, to appreciate the distance between thebone crest and the mandibular canal. So it is not mandatory todownload CT data into the system when it is sufficient toappreciate the implant length and a safe distance with themandibular canal. Real-time control of registration is important,and the positioning of a pointer on a tooth surface is rapid and easyto perform.Robustness or Accuracy of the Whole SystemWe have described errors in all segments of the system: CT scan,fiducial x-ray detection, stereovision tracking system (cameras,magnetic captor, inertia system), tracker on contra angle, spreadbetween markers in the surgical field, relative position of patientswith stereovision, change in guide position during surgery, andothers.We have also operator errors: 3D mapping (pointer or 3Dultrasound), detection of markers with the pointer by the operator,image matching (CT scan or CBCT, x-ray film, ultrasound, magneticresonance imaging [IRM]).All these parameters will affect accuracy,5 and they mayaccumulate with some systems. With RTMIS, if images are obtainedduring surgery by ultrasound or palpor 3D mapping, CD scanerrors will not affect the tool position, and the inaccuracy willdepend only on the tracking device. We are dealing with a goldstandard measuring system with a patient marker locked in the jaw,whereas with CT scan-based systems a mathematic transformation isextracted from radiomarker and image registration data.ConclusionPatient and clinician demand exists for a minimally invasiveapproach to implant surgery. RTM implant placement secures4506 implant placement for all operators, but experience is stillimportant for an evaluation of the clinical indication, risk in tissuemanagement, and prosthetic case requirements. The ideal trainingto obtain a required competence with a digital system needs to bedefined, with simplification of all procedures, and it may be anevolution toward a surgical team. With an integration of CAD andCAM prosthetic procedures, laboratory technicians will affect theoverall treatment of patients receiving implants by reducing thetreatment time and eventually the cost as well. Case Scenario 84.1Patient:A 62-year-old South Asian manChief Complaint:“As a computer programmer, I appreciate precision andtechnology. I am interested in safer and more precise methods formy implant placement surgery.”Background Information:Patient is a nonsmoker, has high cholesterol, and does not reportany other systemic conditions. Patient is taking simvastatin andhas regular medical examinations. He reports brushing andflossing twice a day since losing his upper right molars (caries). Heavoided replacement of these teeth until now. Patient seeks a moreprecise way to place his implants without impinging on themaxillary sinus space.Clinical Findings:Examination reveals generalized 2- to 3-mm probing pocket depthwith partial edentulism. He has been missing the maxillary rightmolars (#2 and #3) for a long time. Moderate vertical bone loss isnoted in the edentulous area.CASE-BASEDQUESTIONSSOLUTIONS1. What are theadvantages ofreal-time microAnswer: DExplanation: All of the listed answer choices are the benefits andadvantages of using real-time micro positioning implant surgery. It is4507 positioningimplant surgery?A. Potential toreducesurgicaltimeB. MinimizedsurgicalinvasivenessC. Moreprecisetranslationof implantsurgicalplanning totheprocedureD. All of theabovea more advanced way of incorporating patient data from computedtomography and cone beam computed tomography scans duringimplant surgery. It also allows treatment of challenging cases withmore comfort and confidence.2. Real-time micropositioning (orfiduciary)markers mustaccurately relatethe image data tothe _________.A. PlannedprostheticcrownpositionsB. Actualpatient'sanatomyC. 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