Dental Radiography Errors and Digital Imaging (PDF)

Error cause effect correction image Head twist Improper  One side of the image will be Mid sagittal plane /rotation / off adjustment of...

Error cause effect correction image Head twist Improper  One side of the image will be Mid sagittal plane /rotation / off adjustment of magnified & blurred more than perpendicular to center mid sagittal the other in the horizontal the floor plane dimension (not perpendicular to floor) Head Tilting Improper  The mandible appears tilted with Mid sagittal plane adjustment of one condyle higher & larger than perpendicular to mid sagittal the other the floor plane (not perpendicular to floor) Head is positioned Patient’s teeth  The anterior teeth appear blurred Guide the patient too far anterior are positioned and narrowed to bite on the too far forward notch on the bite-block Head is positioned Patient’s teeth  The anterior teeth appear blurred Guide the patient too far posterior are positioned and widened to bite on the too far backward notch on the bite-block Chin is tilted too far Chin is tipped too  The lower incisors appear blurred Frankfort Plane downward low Improper  Exaggerated smile line (curved parallel to the adjustment of upwards) floor Frankfort Plane  V-shaped mandible (not parallel to  The condyles may not be visible the floor) Chin is tilted too far Chin is tipped too  The hard palate and the floor of Frankfort Plane upward high improper the nasal cavity appear parallel to the adjustment of superimposed over the roots of floor Frankfort Plane the maxillary teeth. (not parallel to  The maxillary incisors appear the floor) blurred & magnified.  Reverse smile line (curved downwards)  Square-shaped mandible.  Condylar heads cut-off. Improper chin The mandible is  The nasal fossa and maxillary Position patient support not seated onto sinuses will likely be partially cut on the chin rest the chin rest off the top of the image Improper Tongue Patient did not  Formation of a radiolucent area Ask patient to position place the tongue above the apices of the upper place tongue on against the hard teeth hard palate palate Movement The patient  The part of radiograph being Ask patient to moves anytime exposed at movement time stand steady during exposure appears blurred Step deformity Foreign objects Failure to Obscure areas of interest Remove remove appliances or any metal object Ghost image Opaque shadow Radiopaque artifact resembles the Remove of a Dense Object real counterpart but found on the (jewelry, other side, indistinct (blurred in the anatomy) that horizontal and vertical direction), results when the larger, at higher level object is exposed twice by the x-ray Reversed, Magnified, blurred, on beam the other side, at a higher level Lead Apron artifact Improper Radiopaque cone shaped artifact Proper placement of the over the midline placement of lead apron or lead apron. usage of one Discard thyroid with thyroid collar when collar imaging mandibular arch Improper Posture the back of the White shadow appears in the midline Proper position patient is not (superimposition of the cervical of the patient straight and spine) obscure areas of interest erect Sign Error One side magnified than the other Head twist One condyle at a higher level than Head tilt the other Shortened anterior Head in anterior position Magnified anterior Head in posterior position Lateral condylar cut off Head is positioned too far posterior Exaggerated smile Chin up V shape mandible Chin up Reverse smile line Chin down Square arch Chin down Vertical condyle cut off Chin down / improper chin support Radiolucent shadow over apices Improper tongue position of upper anterior teeth Magnified Shadow / ghost image Metal artifact Large radiopacity in midline Improper patient position Small radiopacity in midline Lead apron - thyroid collar artifact / cone shaped artifact Discontinuity of image resolution Movement Lecture 4 -Digital radiography Thursday, January 11, 2024 6:46 PM lecture4-Di gital Radi... Basically seeing the picture on a computer New Section 1 Page 1  Indirect you have to change the picture from analog to a scannable from to appear on the computer. Direct picture it appears directly on the computer screen The more you transfer the picture from a medium to a medium the quality of the picture decreases so that it why we don’t work indirect digital radiography New Section 1 Page 2 New Section 1 Page 3  The word sensor goes for CCD or CMOS The word Imaging plate goes for PSP There is NO CCD in the market nowadays cause it requires a lot of energy consumption so they stopped producing it PSP is considered a semi direct method of Xray taking. However it is considered direct cause there is no imaging processing and solutions New Section 1 Page 4  The wireless CCD gets affected by any electronic device in the clinic so it is not used now CMOS AND CCD are rigid and have a cable which is a disadvantage The rigidity makes some areas not easy to reach and the cable would increase the susceptibility that the patient would move the sensor while taking a picture Advantages of digital over conventional imaging Dramatic decrease in the radiation dose from the conventional to the digital : 0.4 seconds in conventional for periapical 0.08 seconds in digital for periapical Which is 80 to 90 % decrease in radiation dose And it is related to the brand of the sensor An advantage of using digital radiography is that the Xray images taken are unlimited it is an advantage but don’t compromise this over taking a lot of Xray photos thus increasing the radiation dose Changing contrast and brightness are the best image enhancements of digital radiography Grey is poor contrast This is important in identification of landmarks You can overcome the exposure errors by New Section 1 Page 5  This is important in identification of landmarks You can overcome the exposure errors by modifying the image but this is within limits in digital radiography however it is better to adjust the exposure parameters beforehand for the best image quality Not good and not favorable to use Not good and not favorable to use New Section 1 Page 6  Not good and not favorable to use It would take you more time to confirm that this is a carious lesion as you already have colors in mind of the carious lesion Endodontists love this to identify the apex of the Guetta percha New Section 1 Page 7  Zooming and magnification is a very good image enhancement The edges of the restoration and crowns appear better in here however it is not of significant importance New Section 1 Page 8  Straight or curved rulers are there in softwares Endodontists use curved Implantologists use straight rulers Are Measurements from digital are more accurate than film based measurements ? No it is just easier digital radiography did not solve the accuracy of measurements Digital subtraction softwares are paid software to show you the difference between two pictures. Example bone grafting before and after to see the density of bine grafting if there is bone loss or gain. However it is not used New Section 1 Page 9  Postoperative implant placement Preoperative implant placement 5% cases that can be planned only by using the periapical Xray New Section 1 Page 10  Another advantage is that You can combine all patient data in one place X-rays , photographs , patient history and every single detail. The Initial cost is very high Spatial resolution in SOME types are not so good Inconvenience in CMOS is that it is rigid and in PSP is that it cannot be bent New Section 1 Page 11  Dark room is a hassle Communication is now very important with the patient If I have a team of dentists communication is important We decrease the dose to the patient AM I opening a small clinic or a big running dental center ? New Section 1 Page 12 New Section 1 Page 13  12 points to decide which one do you need Active area of PSP is bigger than CMOS. Size 2 /1.5/1.3 sizes of CMOS have almost the same active area in CMOS. The biggest film size in CMOS has a smaller active are than PSP New Section 1 Page 14  Spatial resolution is better in CMOS and CCD than PSP as the whole category. But in some types of the PSP it could be better. Bottom line CMOS is better Spatial resolution is measured in LP:" Line pair per millimeter" so the more the LP number the better the spatial resolution The normal periapical film gives you 20 LP. So a CMOS with 17 to 22 LP is good. Contrast resolution is measured in bit. 14 bit is 2 to the power of 14 which gives a 17,000 color differences. However your eyes won't get the difference neither the screen so the contrast resolution is not of that importance. So buys a sensor with a higher contrast resolution is not important. Spatial resolution IS MORE IMPORTANT. New Section 1 Page 15  CMOS is faster than PSP however it takes 20 to 45 seconds for the PSP so it is not of a great significance as a point of comparison CMOS is Bulky PSP is thin and a bit flexible so PSP is MORE Convenient New Section 1 Page 16  Covers of PSP are dark and it won't get burnet immediately from a source of light but the more you expose it to light the worse. PSP sleeves are better than the CMOS Standardization is important and we use a film holder. The convenience of film holders for the PSP is better than the CMOS So PSP is better for research and standardization New Section 1 Page 17  We could use one imaging plate of PSP for multiple rooms and use the same computer we will just need a different Xray devices in all rooms so PSP could be more coinvent in multiple operating rooms New Section 1 Page 18  Every operator could buy himself PSP than every operator could buy himself a CMOS as it would be more expensive also if a CMOS gets destroyed by an operate it would cost a lot to buy a new CMOS than PSP Endodontists need a CMOS for faster Xray interpretation so a CMOS is better for him aslo they need to take multiple pictures for master cone and post operative and so on Implantologists need more active area and take less pictures so a psp is better. In Pediatrics a PSP size zero is better for children than the bulky CMOS New Section 1 Page 19  4 occlusal (not used) 2 most common used in periapical and bite wing 0 to 1 for children 0 is smaller in two dimension PSP is Much more expensive than CMOS And it is the main disadvantage of the PSP The plate itself is not expensive but the whole system is very expensive New Section 1 Page 20 New Section 1 Page 21  Panorama can be bot digital and conventional However we only use the digital nowadays There is no PANORAMA AS A PSP The quality of the digital panorama is better than intraoral New Section 1 Page 22 New Section 1 Page 23  Master of Implantology Intra-Oral Radiographic Techniques Dr. Mohamed Khalifa Professor – Oral & Maxillofacial Radiology 2023/2024 Terminology loss of third dimension (depth or Plain (2D imaging modalities) thickness) but there is up and down and mesiodistal Cross-sectional (3D imaging modalities) every picture is a 2D but from different views Terminology Plain (2D imaging modalities) (Superimposition) e.g. periapical, occlusal lat. ceph…… Cross-sectional (3D imaging modalities) (No Superimposition) e.g. CT, CBCT, MRI MRI not used Terminology Conventional (film based) Digital (computer based) Radiographic Techniques Intra-Oral Extra-oral What are the main differences? Intra-Oral bad coverage Resolution Extra-oral bad resolution Coverage Intra-Oral Radiographic Techniques bisecting Periapical parelleling Bitewing not used only part of crown and root appear Occlusal can be used if there is no CBCT gives an idea about buccolingual dimension but it is not reliable bone concavity not appear Intra-Oral Radiographic Techniques Periapical Regarding Bitewing implantology Occlusal ?? What do we have? order acc. to use in implantology Periapical 1 Occlusal 5 2 multiple edentulous Panoramic Lateral cephalometric Conventional tomography CT 4 CBCT 3 You have to compromise Availability Information Dose Cost  Periapical Radiograph 3 - 5 mm of bone appear Periapical radiography describes intra-oral techniques designed to show individual teeth and the tissues around the relation to vital structures apices. Periapical use small area straitforword followup unless complication Merits Limitations  Merits Availability Easiness Cost Radiation dose No metal artifact Resolution highest Spatial resolution sharpness panorama has low spatial resolution Bisecting angle technique pixelated Paralleling technique Ability to identify small adjacent objects as separate objects the smaller the pixels the better the details the better the resolution 2 types of resolution spatial resolution > difference between objects contrast resolution > difference in color Limitations Limited coverage 3 - 4 maximum Lack of third dimension superimposed / bone concavities not shown Distortion size distortion > image bigger than real but same shape, problem in technique shape distortion> elongation or shortening due to film tooth relation they should be parallel and xray perpendicular to them Ideal image density is degree of darkness (blackness) or brightness contrast is difference between black, white, gray Visual characteristics (Proper density and contrast) Geometric characteristics (Sharpness – free of distortion) Covering the needed area Ideal image = least distortion + highest sharpness resolution  show shape and size Shadow casting not real picture when i move away it appears bigger Shadow casting increase distance between light source and object = increase size = decrease resolution  Limitations Distortion different proportions a- shape (shortening – elongation) b- size (magnification) same prportions i need central beam ( the most parallel) so xray should be away from film diverge beam cause size distortion Influencing factors 1. Object-film distance least distance Source – film distance need longest distance 2. 3. Object – film alignment 4. Source - (object-film) alignment 5. Focal spotnot changed Shape distortion Bisected angle Paralleling √√√ Size distortion bisector no space role of isometry film no parallelism tooth shape distortion Bisected angle xray beam xray beam is perpendicular on bisector between tooth an film Paralleling √√√ to get exact copy of picture 1. both objects parallel to each other 2. both objects close to each other space is compromised 3. xray perpendicular on both of them size distortion but it is immposible long cone to minimize divergent beam because of arch and bone, soft tissue, teeth and preserve distance hard palate and film holder to preserve parallelism Paralleling technique Paralleling technique Terminology Paralleling tech. Right angle tech. 90 degree on tooth and film Long cone tech. Paralleling technique  Long cone 16 inch = 40 cm  12 inch 30 cm is used scattering beam hits patient and returns back divergence is from original radiation small distance between xray and film makes divergence and magnification longer cone is better 16 inch = similar object History of paralleling technique Film holders  Film holders angulation adapted automatically no need to use vertical angulation numbers hemostat cannot maintain parallelism or vertical or horizontal angulation Eezee Grip – Snap-A bite ideal fil holder XCP Stabe bite block Hemostat film holder Precision film holder The Ideal film holder Rinn corporation (XCP) X: Extension C: Cone P: Paralleling The only film holder to be used in implantology Rinn corporation (XCP) film is vertical film is horizontal Posterior Anterior Rinn corporation (XCP) Bite-wing Endo-ray What about digital imaging? For digital imaging For digital imaging Paralleling technique minimizes size distortion but do not completely remove it Indications of periapical radiographs Detection of apical infections and pathoses. Detection of dental caries Assessment of the periodontal status; state of periodontal membrane space and lamina dura. After trauma to the teeth and associated alveolar bone. Assessment of the presence and position of unerupted teeth. Assessment of root morphology before extractions. During endodontic treatment. Preoperative assessment and postoperative appraisal of apical surgery. Detailed evaluation of apical pathological lesions within the alveolar bone. Preoperative and post-operative evaluation of implants. For periodic check-up. maxillofacial trauma > CT Bisecting angle technique Rule of Isometry Rule of Isometry Rule of Isometry Bisecting angle technique Bisecting angle technique occlusal plane parallel to floor no metallic object zero position mid sagittal plane perpendicular to floor imaging maxilla = patient raise his head Patient position Film placement Cone adjustment 2-3 mm from occlusal Cone adjustment angle between beam and occlusal plane 1. Vertical angulation 2. Horizontal angulation 3. Point of entry adjust cone acc. to area of interest using lines on face if wrong result in cone cut Vertical Angulation Vertical Angulation Horizontal Angulation angulation between interproximal spaces incorrect = overlaping stand behind cone Point of Entry anterior = tip of nosa canine = behind ala of nose with 1/2 cm molars = ala tragus line cone should cover the film Paralleling Vs. Bisecting angle no shape distortion standardization shape distortion annoy patient tech sensitive gag reflex patient factor limitation in shallow floor of mouth Role of periapical radiography in implantology  Phases (stages) of Implants Stage 1: Surgical Stage 2: Restorative Phase 1 Phase 2 Phase 3 Pre- Intra- Post- operative operative operative Pre-operative assessment Detection Pathological lesions Bone diseases Impacted teeth Remaining roots Bone concavities X vital structures Determination Bone quantity no bucco lingual width occlusal = maximum bl Bone quality Bone quantity Bone height (relationship to vital structures) Bone quantity Mesio-distal length Bone quantity Bucco-lingual width X Bone quality bone marrow spaces wide = black thick trabeculae = high density thin trabecule = spongy bone bone density = dense or spongy can measure relative density accurate density bu DEXA or quantitative CT Bone density X Cortical bone thickness and integrity X Intra-operative assessment  Intra-operative Assessment Assess the estimated length of implant and relation of implant to surrounding vital structures. Guide Pins to determine the Correction of the direction of parallelism of the implants and the the posterior implant. depth to the inferior alveolar nerve.  Post-operative assessment no metal artifact Proper healing Proper healing if u cannot see seration of implant there is a problem in vertical angulation Complications bone loss Complications Complications Complications Complications fracture Follow-up Bite-wing Not used in implantology Occlusal Provides the maximum bucco-lingual dimension Has no role in implantology  Radiology lecture 1 If class II caries is present in the tooth adjacent to an implant, it will affect the success rate of the implant placed. Active periodontal disease will also affect. Most important thing in the implant placement is Planning For proper planning: 1. Oral examination 2. Radiographic examination Oral examination: things to detect that could cause failure in osteointegration  Certain medications the patients take due to medical diseases  Bad oral hygiene  Heavy smokers  Soft tissue thickness  State of the adjacent teeth Radiographic examination: to choose the implant  Detected pathology  Is the bone enough? The location of the sinus? Implantology is divided into two phases: 1. Surgical phase 2. Prosthetic phase In radiology, implantology is divided into three phases: 1. Preoperative phase (most important) 2. Intra operative phase (rarely used) 3. Post operative phase (either we loaded or not with the prosthetic part): to avoid further mistakes Phase 1: Pre-operative implant imaging ‫هل المكان دا صالح للزراعة؟‬ Objectives: I. Detection of pathological lesions  Residual cyst present in an edentulous area: asses the bone capacity  Bone diseases: abnormal bone trabeculae and bone marrow spaces in the given panoramic xray: affecting the osseointegration / quality of bone  Remaining roots: if the patient underwent a bridge years ago and is in pain, and on X-ray examination a remaining root was detected that wasn’t removed  Impacted teeth: common in the canine regions (retained C)  Deep bone concavities Coronal view (frontal view) of the CBCT, buccal cortex and the lingual cortex, an aggressive concavity in the molar region of the mandible named the fossa of the submandibular gland This fossa is within the anatomy, it can be either very shallow or very deep If it is deep, it will limit the implant dimension, needing sufficient bone around the implant Detecting this concavity is important to determine the implant diameter, direction, length.  Undercuts in the anterior maxilla II. Determination  Bone Quantity 1. Available alveolar bone vertical height Vital structures:  Incisive foramen: in the midline of the maxilla  Greater palatine nerve (less important)  Inferior alveolar canal / mental foramen I need to keep a safety margin of 2mm, as it would cause: Numbness Compression while osteotomy could cause pressure on the nerve  Maxillary sinus The patient won’t feel, safety margin could be 0.5 mm Schools of implant placement related to the floor of the sinus: Getting into it is fine, Getting onto the floor intentionally is fine, it would take anchorage from it. Asses / measure the distance between the bone and the sinus, and estimate Is It enough? Or do I need a sinus lift? Or is a short implant fine? Or I won’t get into the sinus? If there are 8mm left, I need to think of: closed sinus lifting to place a 10mm implant? Or should I place a short implant of 7mm? Implant length should be therefore determined upon the bone height.  Floor of the nasal cavity Rarely a problem There is a big distance between the crest and the nasal cavity, unlike the maxillary sinus where: Pneumatization can happen Its location is near the roots of the teeth  Lingual foramen In the midline of the mandible Appears in the periapical xray as a black point within the genial tubercles But it is actually both above and below the genial tubercles Very very dangerous: IAN passes and releases a mental branch, then continues as an incisive branch until it reaches the midline The left and the right incisive branch meets at the lingual foramen Sublingual artery that nutrifies the anterior segment of the mandible: enters the mandible through the lingual foramen. Therefore, if an implant is placed in the L1, and I mistakenly got into the lingual foramen, bleeding will take place in the floor of the mouth that has loose connective tissue, which is invisible and sometimes it would not instantly happen, causing suffocation. A life-threatening condition and the patient could die. Schools: if you hit it and you did not break the lingual wall nothing would happen. Research: overdenture on a single implant in the midline. Problems faced: lingual foramen Therefore, it is important to assess the distance to the vital structure to know the length of the implant to be placed 2 Available alveolar bone mesio-distal length It can be known from the patient’s mouth, or the cast. What appears in the patient’s mouth can be different than what is there in the bone E.g.: the distance between the crowns is smaller than the bone (favorable) E.g.: the distance between the roots of the adjacent teeth is smaller (not favorable) :appears as good space near the crown As a rule, there should be 1.5 - 2 mm from adjacent natural tooth and 3mm from adjacent implant. This is important for the bone blood supply, and therefore the dental papilla. If there is a shorter distance, the blood supply would be less and therefore the papilla could be atrophied MD dimension of the coronal portion is important: for proper crown placement above the implant 3 Available alveolar bone Bucco-lingual width Bone thickness and soft tissue thickness are what appears to be You cannot estimate whether either of them is thick or thin Bone sounding: an obsolete way to determine the thickness, painful and not accurate Now, I can calculate the BL depth/ width using other techniques History: 1mm buccal and 1mm lingual Then: 1.5mm B and 1mm L Anterior: 2mm B and 1mm L (esthetic zone) Recently: Both anterior and posterior: 2mm B and 1mm L Problems are commonly associated with the BL: atrophy and thinning of the bone could take place. because the MD (especially when in molars) I already have roots If I want to place an implant in the lower molar site, the BL is 6mm,, theoretically, I need to place a 3mm implant which is not present, therefore I would need to expand the bone or place a bone graft. Central incisor labio-palatal = 8mm ,, a 5mm implant would be too thick Bone thickness is one of the factors affecting implant placement and not all factors 4 Bone morphology Bone might be wide above, yet below a concavity might be present that makes the available bone less. This might be present in the: mandibular molar region and the anterior maxilla. Eg: from a lateral view, a labial cortex, palatal cortex, a concavity might be present making the bone present insufficient to place an implant. Happens most commonly in the retained B or C, due to the short root of the deciduous teeth therefore the periapical bone is also thin.  Bone Quality includes the assessment of 1. The trabecular bone density  Old classification (1985) Lekholm and Zarb: classified the bone according to the cortical (compact) and the cancellous (spongy) bone Type 1: Compact bone Type 2: cancellous bone is less (not preferable): during osteotomy, heat generation happens, and necrosis could take place due to absence of cancellous bone Type 3: spongy bone is many bone trabeculae and bone marrow spaces are thin Type 4: loose cancellous bone Q. What do I need in implant placement? Both I need cortical bone for primary stability I need cancellous bone for the blood supply and the osseointegration / function I won’t choose the patient, we work for all patients, instead we have certain precautions to be followed when the bone is type 4 compact = cortical bone  Misch classification D1: low cancellous, lower incisiors are thin D4: the worst type, healing period is longer than the mandible. If there are three missing teeth in the mandible, two implants and a bridge can be placed. While in maxilla, three implants is better to be placed. Appears blacken, wide marrow spaces, more trabecules D5: bone graft= immature bone (the only difference) Bone density is measured by CT. CBCT is not reliable to measure bone density due to scattered radiation when xray hits object change its direction ‫االرقام مش حفظ‬ 2. The cortical bone (plate) thickness and integrity Integrity: In a coronal view of the CBCT, lingual cortex, buccal cortex, premolar region has the mental foramen opening, there is no sufficient integral buccal cortical plate. Therefore, during extraction, I should create a buccal cortical plate using a bone grafting membrane or wait for it to heal and then assess, within 3-4 month. Assessment before extraction is preferred. Research: each case should need a bone graft after extraction, according to the financial status of the patient Thickness: a thin cortical bone would increase the chance of bone resorption especially if it was in an esthetic bone, causing exposure to the implant. Phase 2: Intra-operative implant imaging If I want to place more than one implant, I can place guide pins, to check the parallelism between the two implants (I can splint later) and take a periapical radiograph and determine the approach to a vital structure. In reality, I can check the parallelism by inspection and by checking the occlusion too. Because I have different views, unlike the xray I have only one view to check from Preoperative planning is more important: and the crowns of the adjacent teeth can be used as a guide to implant placement. If the roots are divergent, and the space is unpredictable, (more than 2 implants), then I will need a surgical guide to assess the distance to be left from the adjacent teeth and to place an implant. Phase 3: post-operative implant imaging I want to assess the:  Healing: is the bone around the implant sufficient?  Complications: peri-implantitis, therefore bone is resorbed. The implant is mobile: radiolucency around the implant  Fracture of the implant (not common with the newly designed implants) due to bad direction of the implant and high forces or loosening in the screw. It is hard to remove a fractured implant.  Implant in the sinus, foreign body reaction Follow up yearly to asses the bone level Intra oral Radiography: 1. Periapical Radiography Limitations:  Distortion  Shape: changes in one dimension (shortening and elongation) Length is changed while dimension is not  Size: magnification. The xray is divergent, therefore, the size of the object to the photo will be magnified. Techniques of filming  Bisecting angle  Paralleling: we have to use this technique in order to:  Eliminate (due to the use of film holder) the shape distortion  Minimize (due to the presence of a long cone) the magnification This will decrease and never forbid. Helping in the follow up: the same picture over the years The ideal film holder: XCP Presence of rim, bite block, bar connecting between both, helps in adjusting the angulation and avoids all the errors such as shape distortion, cone cut. Magnification calculation using metallic ball if actual size 5 mm and it appears 5.5 mm Magnification = (5.5/5) x 100 = 110% so it is magnified by 10% Cairo University Faculty of Dentistry Role of Radiography in Dental Implantology Prepared by: Dr. Mohamed Khalifa Zayet Professor - Oral & Maxillofacial Radiology Dr. Noha Saleh Abu Taleb Professor - Oral & Maxillofacial Radiology 2024/2025 0 Introduction: Radiographic assessment plays an important role in the evaluation of dental implants during various stages of treatment either in the pre-surgical assessment, intra-operative or post-operatively. Radiographs help the clinician to visualize the alveolar ridges and adjacent structures in all three dimensions and guide the choice of site, number, size and axial orientation of the implants. ► Implant Imaging Phases: 1. Phase 1: Pre-operative implant imaging. 2. Phase 2: Intra-operative implant imaging. 3. Phase 3: Post-operative implant imaging. Phase 1: Pre-operative implant imaging Radiographs help the clinician visualize the alveolar ridges and adjacent structures in all three dimensions and guide the choice of site, number, size, and axial orientation of the implants. Objectives: I. Detection of pathologic conditions, retained root fragments, impacted teeth, residual infection, cystic lesions and any osseous pathology that could compromise the implant outcome. II. Determination of bone quantity and quality and their influence on implant position and orientation. 1  Bone Quantity includes the assessment of: 1. Available alveolar bone vertical height. 2. Available alveolar bone bucco-lingual width. 3. Available alveolar bone mesio-distal length. 4. Bone morphology and contour (bone concavities). 1- Available alveolar bone vertical height: - Measured from the crest of the edentulous ridge to adjacent vital structures such as floor of maxillary sinus, inferior alveolar canal, mental foramen, floor of nasal cavity and incisive foramen. - This measurement help select the implant length which is important for the initial stability and resistance to rotational torque during implant screw tightening. - Implant length should be 10-15 mm ideally 12mm. 2- Available alveolar bone bucco-lingual width: - Measured from the buccal cortical plate to the lingual cortical plate along the alveolar crest. - This measurement aid in selecting the implant diameter and bucco-lingual (axial) inclination, and implant placement to maximal engagement of cortical bone. - For assessment of bone bucco-lingual width, Cross-Sectional image is recommended. - As a general rule there should be at least 2.5 - 3mm bone width greater than the implant diameter (2mm buccul and 1 mm lingual) (e.g for a 4mm implant there should be 7mm bucco-lingual bone). C) 2  3- Available alveolar bone mesio-distal length: - This measurement influences the number of implants that could be inserted in a specific site, also it aids in evaluating the mesio-distal inclination of the implants to ensure tooth - implant or implant - implant parallelism. - As a general rule, there should be 1.5 - 2 mm from adjacent natural tooth and 3mm from adjacent implant. - Mesio-distal length beside bucco-lingual width influences the selection of implant diameter. 4- Bone morphology such as osseous undercuts and ridge concavities should be considered. This is important in determining the axial inclination of the implant to avoid bone perforation during implant insertion. (If mandibular lingual perforation occurs in posterior mandible due to presence of submandibular gland concavity this may lead to injury of the lingual artery leading to life-threatening problems).  Bone Quality includes the assessment of: 1. The trabecular bone density: A greater number of internal trabeculae per unit area is advantageous for osseo-integration. In CT, bone density measurement can be performed, where the densitometric analysis yields a certain number "CT number" measured in Hounsfield units "HU." 2. The cortical bone thickness and integrity: it is best suited to withstand the functional loading forces of dental implants. In general, the thicker the cortical bone, the greater the likelihood of successful osseous integration. 3 # Four types of bone quality indices are described based on subjective evaluation of cortical thickness and trabecular pattern proposed by Leckholm and Zarb1985: Type 1: Homogenous compact bone. Type 2: Thick compact bone surrounds a core of dense trabecular bone. Type 3: Thin compact bone surrounds dense trabecular bone. Type 4: very thin compact bone surrounds low density trabecular bone. # Misch bone density classification according to description and anatomic location: D1 - Dense cortical - Anterior mandible D2 - Porous cortical - Anterior mandible - Coarse trabecular - Posterior mandible - Anterior maxilla D3 - Porous thin cortical - Anterior maxilla - Fine trabecular - Posterior maxilla - Posterior mandible D4 - Fine trabecular - Posterior maxilla D5 - Very soft immature bone - Developing sinus graft non mineralized bone # Radiographic Bone Density, classification of bone quality based on CT number of bone: D1 1250 HU D2 850-1250 HU D3 350-850 HU D4 150-350 HU D5 < 150 HU N.B. as the HU decreases, the bone quality decreases (more porous bone). 4 ► Imaging Techniques:  The ideal imaging technique should have several essential characteristics including: 1. The ability to visualize the implant site in the mesio-distal, bucco- lingual, and superior-inferior dimensions. 2. The ability to visualize the spatial relationship of the implant site to the adjacent vital structures. 3. The ability to allow reliable, accurate measurements of bone quantity and quality. 4. A capacity to evaluate the density of trabecular bone as well as cortical thickness and integrity. 5. A capacity to correlate the imaged site with the clinical site. 6. Reasonable access and cost to the patient. 7. Minimal radiation dose. - However, there is no ideal imaging technique exists that would be suitable for all patients. All imaging modalities have their advantages and limitations. - Imaging techniques for implant assessment include two dimensional (2D) and three dimensional (3D) imaging modalities, the selection of specific imaging technique should be based on the technique best suited to provide the information required by the implant team; the restorative dentist, the surgeon, and the radiologist. - 3D imaging modalities are preferred, however, if not available, usually a combination of 2D radiographs is used to provide the necessary information required in 3D. 5 1. Intraoral Radiography: A) Periapical Radiography: Periapical radiographs, made on a dentate arch, typically are exposed using the paralleling technique. The long cone paralleling technique eliminates distortion and limits magnification to less than 10%. Indications: 1. Evaluate the status the remaining alveolar bone in the horizontal (mesio- distal) dimension and vertical dimension (bone height). 2. Rule out underling dental pathologic conditions. 3. Used for small edentulous spaces (usually in single implant; with abundant available bone). Advantages: 1. Readily available. 2. High image definition (high resolution images). 3. Least cost and radiation exposure. Limitations: 1. Cannot determine the bucco-lingual dimension. 2. Limited capability of depicting the spatial relationship between the vital structures and the proposed implant site as there is limited imaging area due to small film size. 3. Cannot assess bone density: superimposition of cortical and trabecular bone prevents assessment of trabecular bone density. 4. Image elongation, foreshortening and magnification (although this is minimum when using paralleling technique, however, an edentulous alveolar ridge may not have the same long axis as the tooth making the 6  precise parallel film positioning difficult leading to elongation or foreshortening ).  Image magnification can be assessed by a diagnostic template having a known – dimension radiographic marker (5mm ball bearing) at the crestal region of the desired implant location. The magnification factor can be calculated by dividing the diameter of the marker measured on the radiograph by its actual diameter. The measurements obtained from the images (usually in millimeters) are divided by the magnification factor to obtain the actual measurement. B) Occlusal Radiography: Advantages:  Determine the bucco-lingual dimensions of the mandibular bone.  Important in mapping for conventional tomography. Limitations: 1. Although somewhat useful, the occlusal image records only the widest portion of the mandible, which typically is located inferior to the alveolar ridge (i.e. cannot precisely determine the actual crestal bone width especially in severely resorbed ridges with knife-edge). This may give the clinician the impression that more bone is available in the cross-sectional (bucco-lingual) dimension than actually exists. 2. The occlusal technique is not useful in imaging the maxillary arch due to superimposition of anatomic structures superior to the maxillary alveolar ridge. # In general occlusal radiographs are rarely indicated in implant dentistry. 7 2. Lateral Cephalometric Radiography: ★ This projection can provide a cross-sectional view of only the maxillary and mandibular midline. The images of structures not in the midline are superimposed on the contralateral side, complicating the evaluation of other implant sites. Indications: 1. Used in combination with periapical technique for placement of implants near the midline Advantages: 1. It can document the height and labio-lingual width of the alveolar ridge as well as tooth inclinations and the dentoalveolar ridge relationships in the midline of the jaws. 2. Low magnification: lateral cephalometric radiography results in about 7% to 12% image magnification. Limitations: 1. The images of structures not in the midline are superimposed on the contralateral side, complicating the evaluation of other implant sites. 2. Reduced resolution compared to periapical radiographs. 3. Panoramic Radiography: Indications: 1. Used in initial assessment of the crestal alveolar bone height and length as well as the cortical boundaries of the mandibular canal, maxillary sinus and nasal fossae. 8  2. Used for single implant, multiple implants, edentulous, and ridge augmentation cases. Advantages: 1. Demonstration of large imaging area. 2. Assessment of pathologic conditions of the jaws. 3. Initial assessment of the alveolar bone height and length. 4. Readily available and simple. 5. Minimal cost and radiation exposure. Limitations: 1. Linear measurements are not accurate. Image size distortion (magnification) varies significantly among films from different panoramic units and even within different areas of the same film. Magnification can be determined by using ball bearings of known diameter. ★ Vertical magnification: this is relatively constant. The negative vertical angulation of the x-ray beam may cause lingually positioned objects to be projected superiorly on the film:  The lingually positioned inferior alveolar canal will be projected more superiorly underestimating the vertical bone height from the alveolar crest till the superior border of the canal (the bone height required for implant placement).  The mandibular tori will be projected more superiorly resulting in an overestimation of the vertical bone height. ★ Horizontal image magnification: this generally varies from 0.7 to 2.2 times the actual size. The dimensional accuracy in the horizontal plane of 9  panoramic radiographs is highly dependent on the position of the structures of interest relative to the central plane of the image layer. The horizontal dimension of images of structures located facial or lingual to the central plane but still within the image layer tends to be minified or magnified. 2. Errors in patient positioning can further exacerbate measurement error in the horizontal dimension (e.g. improper placement in the mid-sagittal plane leads to increased magnification in one side of the image which compromises appropriate estimation of the bone height). 3. Panoramic radiographs provide a two-dimensional image with no cross- sectional information. 4. Does not demonstrate bone density. 5. The resolution and sharpness of panoramic radiographs are less than those of intraoral films. Digital Radiography: 2D Digital Radiography can provide digital intraoral, digital cephalometric, digital panoramic image and digital conventional tomography. Indications: Same indications as the comparable film based techniques. Advantages: 1. Dose reduction: 2. Image enhancement tools: 3. Linear measurements: 4. Better communications. 10 4. Conventional Tomography:  Conventional Tomography yields a "slice" or selected image layer within the patient. Images of anatomic structures of interest are relatively sharp, and images of structures outside the image layer are blurred beyond recognition by the motion of the x-ray tube and film.  Measurements are directly acquired from the films and subsequently corrected by the magnification factor used. Indications: Conventional tomography is especially convenient in the planning of single implants or multiple implants within a quadrant. Advantages: 1. Tomograms provide cross-sectional images, this enhance visualization of the available bone by providing reliable dimensional measurements at proposed implant sites, including the cross-sectional (bucco-lingual) dimension as well as the vertical dimension. Also, this allows for assessment of lingual concavities in the mandible, which aids in the appropriate prediction the bucco-lingual axis of insertion of the implant. Additionally, cortical thickness can be assessed. 2. Dimensional accuracy: measurements are accurate within about 1 mm Limitations: 1. Less image definition than plain films. 2. Cannot be used to measure bone density. 3. Somewhat limited availability. 4. Greater radiation exposure for multiple implant sites (When large areas are to be investigated, CT scans are preferable as exposure to ionizing radiation is reduced). 11 Digital Radiography: Digital Radiography can provide digital intraoral, digital cephalometric, digital panoramic image and digital conventional tomography. Indications: Same indications as the comparable film based techniques. Advantages: 1. Dose reduction 2. Image enhancement tools 3. Linear measurements 4. Better communications 5. Computed Tomography:  CT allows examining the internal structures of the body free from superimposition.  The CT scanner uses a fan shaped radiation source and detector array arranged in a curvilinear shape.  Images are acquired in the axial plane. The axial images are thin (0.5-2mm).  The image information of these sequential axial images can be manipulated to produce multiple two-dimensional images in various planes (coronal and sagittal mages), using a computer- based process called "Multi Planar reformatting" (MPR) [axial, coronal and sagittal images each is a 2D image but the combination between axial, sagittal and coronal images can provide 3D information about the imaged area].  Also, the image information of these sequential axial images can be manipulated to produce three-dimensional volume rendered images that facilitate the realistic display of volumes (displaying the whole volume of tissues in one image). 12 Indications: - Edentulous patients - Multiple implant insertion - Ridge augmentation Advantages: 1. The Multiplanar reformatted CT permits the production of all possible imaging planes (axial - coronal - sagittal) from a single data acquisition (axial) without patient repositioning. 2. Very high resolution images especially with current generations (Multi- slice CT). 3. No superimposition. 4. Measurements are accurate 5. Estimates internal bone density (in terms of Hounsfield units "HU"). Limitations: 1. Metallic restorations can cause streak image artifacts, this may cast shadows on the proposed implant site resulting in non-diagnostic images. 2. Higher cost and radiation exposure (it has been postulated that the radiation exposure during CT scan of mandible and maxilla is approximately equivalent to 20 panoramic radiographs). 3. The special dental softwares add to the cost of the imaging. 6. Cone Beam Computed Tomography (CBCT): The cone-beam geometry was developed as an alternative to conventional CT to overcome the disadvantages of medical CT in dental imaging especially the high radiation dose. 13 In CBCT, imaging is accomplished by divergent or cone-shaped x-ray beam and a 2D detector area that rotate 360o around the patient to acquire multiple images in one complete scan around the region of interest. The volumetric data set is presented on the computer screen as secondary reconstructed images in three orthogonal planes (axial, sagittal, and coronal). Indications: - Edentulous patients - Single and Multiple implant insertion - Ridge augmentation Advantages: 1- Lower radiation dose when compared with multi-slice CT 2- Interactive software 3- Higher spatial resolution when compared with multi-slice CT Limitations: In fact nowadays CBCT imaging is the most advanced and accurate technique for pre-surgical implant planning. However, the limitation of CBCT relies in: Its contrast resolution is lower than multi-slice CT Its numerical values for bone density are not accurate and cannot be correlated to Hounsfield units of CT Phase 2: Intra-operative implant imaging Objectives 1. Evaluate the surgical site during surgery. 2. Locate a lost implant. 3. Assist in the optimal position and orientation of dental implants. 14 Periapical radiography is the most suitable imaging modality for intra-operative implant assessment Phase 3: Post-operative imaging - A post-prosthetic radiograph should be taken to act as a base-line for future evaluation of the implant fit and bone level. - Single implant: periapical radiographs. Multiple implants: panoramic radiographs. Recall and maintenance imaging: - Follow up radiographs should be taken after 1 year of functional loading and yearly for the first 3 years. - The two aspects that are usually assessed with time after implant placement are the alveolar bone height around the implant and the appearance of the bone changes immediately adjacent and surrounding the implant. As well as occurrence of any complications In summary, diagnostic imaging is an integral part of dental implant therapy for pre-surgical planning, intra-operative assessment, and post-operative assessment by employing a variety of imaging techniques. Cross-sectional imaging is increasingly considered essential for optimal implant placement, especially in the case of complex reconstructions. Good Luck 15  Master of 2 0 Implantology 2 3 Radiation Hazards and Protection Dr. Mohamed Khalifa Prof. – Oral & Maxillofacial Radiology Concepts Procedures  X-ray is a member of the ionizing radiation category. Therefore, it has biological damaging effects These damaging effects could be - Direct or indirect - Acute or chronic - Somatic or genetic - Stochastic or deterministic Biological damage of X-ray Direct Ionization of macro molecules Indirect Free radicals produced by ionization of water Acute or chronic effects Acute: exposure to large amount of radiation in a short duration (Not applicable in dentistry) Chronic: exposure to repeated small amounts of radiation for long duration (Cumulative effect) Somatic or genetic effects Somatic cells → radiation induced cancer Genetic cells → offspring → congenital abnormalities Stochastic or deterministic effects Tissue reactions (Deterministic) Stochastic Tissue reactions (Deterministic) Threshold of radiation above which the reaction will occur definitely ↑ dose→ ↑ severity Early: skin erythema, mucositis Late: osteoradionecrosis Not applicable in dentistry Stochastic There is no threshold May or may not occur ↑dose → ↑ probability (not the severity) No X-ray dose is safe Factors affecting the degree of damage Type and number of broken molecules Radiation intensity Time between exposures Repair capability of the cells The stage of cell reproductive cycle Risk of radiation induced malignancy Type of examination Estimated risk Periapical or bitewing (70 kVp, round collimator, 1 in 1,000,000 D-speed film Periapical or bitewing (70 kVp, rectangular collimator, 1 in 10,000,000 F-speed film Panoramic 1 in 1,000,000 Lateral cephalometric 1 in 5,000,000 Chest (PA) 1 in 1,430.000 CT chest 1 in 3000 CT mandible and maxilla 1 in 80,000 to 1 in 14,300 Craniofacial CBCT 1 in 670,000 to 1 in 18,200  Exposure Dose Produced by radiation source Delivered by individuals  Radiation absorbed dose Gray (Gy), mGy, µGy Dose Equivalent dose Sievert (Sv), mSv, µSv Effective dose Sievert (Sv), mSv, µSv Radiation Protection Radiation Protection 1 2 3 Radiographer General Patient Protection Public Protection Protection Protection of the Patient Concepts Justification Optimization Limitation Justification No practice shall be adopted unless its introduction produces a positive net benefit Intra-oral Panoramic CBCT Optimization All exposures shall be kept As Low As Reasonably Achievable ALARA concept Optimization All exposures shall be kept As Low As Reasonably Practicable According to economic and social conditions ALARP concept Optimization All exposures shall be kept As Low As Diagnostically Achievable Recently ALADA concept Limitation The radiation dose to individuals shall not exceed the limits recommended by ICRP Protection of the patient ALARA: As Low As Reasonably Achievable ALARP: As Low As Reasonably Practicable ALADA: As Low As Diagnostically Achievable Protection of the patient Clinical judgement Equipment Radiographic techniques Clinical judgement No radiographic examination except after detailed history taking and thorough clinical examination Avoid routine X-ray Continuous education for dentists Equipment  Machine  Film  Protective aids Equipment Exposure parameters mA, Exposure time, kVp Equipment Collimator Round vs rectangular collimator Equipment PID Short Long Position indicating device (PID) Short PID Long PID Equipment Filtration Means of filtration (Inherent – added) Added Filter 50-70 kVp 1.5 mm Al > 70 kVp 2.5 mm Al Film Film speed D E E+ F Digital Vs. film-based Intra-oral 80- 90 % less than D-speed films 50 % less than E-speed films Extra-oral Most of current panoramic & extra-oral machines are digital Protective aids Lead apron Thyroid collar Lead apron 0.25 mm thickness Should not be folded Non-leaded protective apron Radiographic techniques Mastering the techniques of projection and processing Decrease the number of retakes Continuous education and training Protection of childbearing age female & pregnant females  Protection of the Radiographer Protection of the dentist (radiographer) Never hold the film inside the patient’s mouth with your finger during exposure Never hold the tube head during exposure Protection of the dentist (radiographer) Distance and angle 150 – 180 cm from tube head 90 - 135º with the primary beam Protection of the dentist (radiographer) Shielding Only in case of not fulfilling the required distance or angle Protection of the dentist (radiographer) Usage of radiation monitoring devices (dosimeters) Dosimeters Film badges Thermoluminescent dosimeters Optically stimulated luminescence dosimeters Personal electronic dosimeters  Protection of the General Public Protection of general public What is meant by general public? Protection of general public Location of the X-ray equipment Thickness and material of separators and walls Warning signs  CBCT & Radiation Dose Radiation Measurements Computed tomography Dose Index (CTDI) Cone Beam Computed tomography Dose Index (CBCTDI) Dose Area Product (DAP)  European Academy of Dentomaxillofacial Radiology (EADMFR) SEDENTEXCT Safety and Efficacy of a New and Emerging Dental X-ray Modality RADIATION PROTECTION N° 172 Implantology CBCT is indicated for cross-sectional imaging prior to implant placement as an alternative to existing cross-sectional techniques where the radiation dose of CBCT is shown to be lower Implantology For cross-sectional imaging prior to implant placement, the advantage of CBCT with adjustable fields of view, compared with MSCT, becomes greater where the region of interest is a localized part of the jaws, as a similar sized field of view can be used Implantology Implantology EAO Clinicians should decide if a patient requires cross- sectional imaging on the basis of the clinical examination, the treatment requirements and on information obtained from conventional radiographs. Implantology EAO The technique chosen should provide the required diagnostic information with the least radiation exposure to the patient Implantology EAO Standard” imaging modalities are combinations of conventional radiographs. Implantology EAO Cross-sectional imaging is applied to those cases where more information is required after appropriate clinical examination and standard radiographic techniques have been performed. Implantology 11 Recommendations  Implantology AAOMR Recommendation 1. Panoramic radiography should be used as the imaging modality of choice in the initial evaluation of the dental implant patient. Recommendation 2. Use intraoral periapical radiography to supplement the preliminary information from panoramic radiography Recommendation 3. Do not use cross-sectional imaging, including CBCT, as an initial diagnostic imaging examination.  Implantology AAOMR Recommendation 4. The radiographic examination of any potential implant site should include cross- sectional imaging orthogonal to the site of interest. This reaffirms the previously stated position of the AAOMR.1 Recommendation 5. CBCT should be considered as the imaging modality of choice for preoperative cross-sectional imaging of potential implant sites.  Implantology AAOMR Recommendation 6. CBCT should be considered when clinical conditions indicate a need for augmentation procedures or site development before placement of dental implants: (1) sinus augmentation, (2) block or particulate bone grafting, (3) ramus or symphysis grafting, (4) assessment of impacted teeth in the field of interest, and (5) evaluation of prior traumatic injury  Implantology AAOMR Recommendation 7. CBCT imaging should be considered if bone reconstruction and augmentation procedures (e.g., ridge preservation or bone grafting) have been performed to treat bone volume deficiencies before implant placement. Recommendation 8. In the absence of clinical signs or symptoms, use intraoral periapical radiography for the postoperative assessment of implants. Panoramic radiographs may be indicated for more extensive implant therapy cases.  Implantology AAOMR Recommendation 9. Use cross-sectional imaging (particularly CBCT) immediately postoperatively only if the patient presents with implant mobility or altered sensation, especially if the fixture is in the posterior mandible. Recommendation 10. Do not use CBCT imaging for periodic review of clinically asymptomatic implants.  Implantology AAOMR Recommendation 11. Cross-sectional imaging, optimally CBCT, should be considered if implant retrieval is anticipated.  Radiographic Follow UP of Dental Implant Hanaa Sayed Mansy BDS, MSc, PhD Lecturer of Oral and Maxillofacial Radiology-Faculty of Dentistry-Cairo and Galala Universities  TABLE OF CONTENTS 01 Radiographic 02 Guide lines for techniques radiographic follow 03 Radiographic 04 Complications of findings dental implant  01 Radiographic Techniques Radiographic Techniques can be used for Radiographic Follow up of Implant Periapical Panorama Bitewing CBCT Occlusal  The best technique for follow up Periapical Advantages Paralleling Disadvantages According to recommendation 8 of American Academy of Oral and Maxillofacial Radiology on criteria for the use of radiology in implantology, periapical X-ray should be used for the postoperative assessment of dental implants.  Multiple implants cases Panorama Advantages Disadvantages Non-linear distortion and low spatial resolution Panoramic radiographs may be indicated for cases with multiple implants.  Limitation of 2D Radiographs Periapical Panorama Clinician should consider the limitation of two-dimensional radiographs as they do not reveal the status of bony structures that lie in the buccal and lingual/palatal aspect of the implants. What about 3D techniques? CBCT According to recommendation 9 and 10 of AAOM, CBCT should not be used for periodic assessment of asymptomatic implants and postoperatively only, in case of altered sensation or implant mobility.  02 Guide Lines for Radiographic Follow Up  Radiographic Follow up Month Year Baseline radiograph a baseline periapical X-ray is extremely important for an early detection and treatment of peri-implantitis. Successful follow up radiographs A symptomatic Radiographic Follow up Week Month Year After 1st 2 weeks 3 Months 1st three 6 weeks 6 Months Years Soft tissue healing Bone healing  03 Radiographic Findings Radiographic Findings Assess bone height  Radiographic Findings Bone resorption Marginal bone loss of 0.9-1.6 mm is around the implant during the first year of restoration and less than 0.2 mm in the following successive years is considered a marker of successful treatment. Radiographic Findings Proximity of the maxillary sinus floor Radiographic Findings Proximity of the neurovascular Successful Survived Failed Implant  Successful Implant Prosthetic Success Long term success Short term success For more than 7 12 months years 1-3 years 3-7 years  Successful Implant Prosthetic Success No mobility No persistent pain No peri-implant No discomfort or radiolucency infection Bone loss less than 0.2 mm per year after the first year of loading Successful Implant Survived Implant Failed Implant  04 Complications of Dental Implant Complications of Dental Implant Failure of osseointegration Complications of Dental Implant Implant fracture Complications of Dental Implant Screw fracture Complications of Dental Implant Loose cover screw Complications of Dental Implant Loose abutment screw Complications of Dental Implant Displaced implant Complications of Dental Implant Bone fenestration Complications of Dental Implant Injury of vital structures Complications of Dental Implant Injury of vital structures Complications of Dental Implant Malposition of implant Complications of Dental Implant Injury of adjacent teeth THANKS!  Dent Clin N Am 52 (2008) 707–730 What is Cone-Beam CT and How Does it Work? William C. Scarfe, BDS, FRACDS, MSa,*, Allan G. Farman, BDS, PhD, DSc, MBAb a Department of Surgical/Hospital Dentistry, University of Louisville School of Dentistry, Room 222G, 501 South Preston Street, Louisville, KY 40292, USA b Department of Surgical/Hospital Dentistry, University of Louisville School of Dentistry, Room 222C, 501 South Preston Street, Louisville, KY 40292, USA Imaging is an important diagnostic adjunct to the clinical assessment of the dental patient. The introduction of panoramic radiography in the 1960s and its widespread adoption throughout the 1970s and 1980s heralded major progress in dental radiology, providing clinicians with a single com- prehensive image of jaws and maxillofacial structures. However, intraoral and extraoral procedures, used individually or in combination, suffer from the same inherent limitations of all planar two-dimensional (2D) projec- tions: magnification, distortion, superimposition, and misrepresentation of structures. Numerous efforts have been made toward three-dimensional (3D) radiographic imaging (eg, stereoscopy, tuned aperture CT) and al- though CT has been available, its application in dentistry has been limited because of cost, access, and dose considerations. The introduction of cone-beam computed tomography (CBCT) specifically dedicated to imaging the maxillofacial region heralds a true paradigm shift from a 2D to a 3D ap- proach to data acquisition and image reconstruction. Interest in CBCT from all fields of dentistry is unprecedented because it has created a revolution in maxillofacial imaging, facilitating the transition of dental diagnosis from 2D to 3D images and expanding the role of imaging from diagnosis to image guidance of operative and surgical procedures by way of third-party appli- cations software. * Corresponding author. E-mail address: [email protected] (W.C. Scarfe). 0011-8532/08/$ - see front matter Ó 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.cden.2008.05.005 dental.theclinics.com 708 SCARFE & FARMAN The purpose of this article is to provide an overview of this CBCT technology and an understanding of the influence of technical parameters on image quality and resultant patient radiation exposure. Background CBCT is a recent technology. Imaging is accomplished by using a rotating gantry to which an x-ray source and detector are fixed. A divergent pyrami- dal- or cone-shaped source of ionizing radiation is directed through the middle of the area of interest onto an area x-ray detector on the opposite side. The x-ray source and detector rotate around a rotation fulcrum fixed within the center of the region of interest. During the rotation, multiple (from 150 to more than 600) sequential planar projection images of the field of view (FOV) are acquired in a complete, or sometimes partial, arc. This procedure varies from a traditional medical CT, which uses a fan-shaped x-ray beam in a helical progression to acquire individual image slices of the FOV and then stacks the slices to obtain a 3D representation. Each slice requires a separate scan and separate 2D reconstruction. Because CBCT exposure incorporates the entire FOV, only one rotational sequence of the gantry is necessary to acquire enough data for image reconstruction (Fig. 1). CBCT was initially developed for angiography , but more recent medical applications have included radiotherapy guidance and mam- mography. The cone-beam geometry was developed as an alternative to conventional CT using either fan-beam or spiral-scan geometries, to pro- vide more rapid acquisition of a data set of the entire FOV and it uses a com- paratively less expensive radiation detector. Obvious advantages of such a system, which provides a shorter examination time, include the reduction of image unsharpness caused by the translation of the patient, reduced image distortion due to internal patient movements, and increased x-ray tube efficiency. However, its main disadvantage, especially with larger FOVs, is a limitation in image quality related to noise and contrast resolu- tion because of the detection of large amounts of scattered radiation. It has only been since the late 1990s that computers capable of computa- tional complexity and x-ray tubes capable of continuous exposure have enabled clinical systems to be manufactured that are inexpensive and small enough to be used in the dental office. Two additional factors have converged to make CBCT possible. Development of compact high-quality two-dimensional detector arrays The demands on any x-ray detector in clinical CBCT are hard to fulfill. The detector must be able to record x-ray photons, read off and send the signal to the computer, and be ready for the next acquisition many hundreds of times within a single rotation. Rotation is usually performed within times equivalent to, or less than, panoramic radiography (10–30 seconds), which  CBCT: TECHNICAL FUNDAMENTALS 709 Fig. 1. X-ray beam projection scheme comparing acquisition geometry of conventional or ‘‘fan’’ beam (right) and ‘‘cone’’ beam (left) imaging geometry and resultant image production. In cone-beam geometry (left), multiple basis projections form the projection data from which orthogonal planar images are secondarily reconstructed. In fan beam geometry, primary recon- struction of data produces axial slices from which secondary reconstruction generates orthog- onal images. The amount of scatter generated (sinusoidal lines) and recorded by cone-beam image acquisition is substantially higher, reducing image contrast and increasing image noise. necessitates frame rate image acquisition times of milliseconds. Detectors were initially produced using a configuration of scintillation screens, image intensifiers, and charge-coupled device (CCD) detectors. However, image intensifier systems are large and bulky and FOVs may suffer from peripheral truncation effects (volumetric ‘‘cone cuts’’), having circular entrance areas rather than more appropriate rectangular ones. Furthermore, rotation of the source-to-detector arrangement may influence sensitivity because of the interference between the magnetic field of the earth and those in the image intensifiers. More recently, high-resolution, inexpensive flat-panel detectors have become available. Such flat detectors are composed of a large-area pixel array of hydrogenated amorphous silicon thin-film transis- tors. X rays are detected indirectly by means of a scintillator, such as terbium-activated gadolinium oxysulphide or thallium-doped cesium iodide, which converts X rays into visible light that is subsequently registered in the photo diode array. The configuration of such detectors is less complicated and offers greater dynamic range and reduced peripheral distortion; how- ever, these detectors require a slightly greater radiation exposure. 710 SCARFE & FARMAN Refinement of approximate cone-beam algorithms Reconstructing 3D objects from cone-beam projections is a fairly recent accomplishment. In conventional fan-beam CT, individual axial slices of the object are sequentially reconstructed using a well-known mathematic technique (filtered back projection) and subsequently assembled to construct the volume. However, with 2D x-ray area detectors and cone-beam geometry, a 3D volume must be reconstructed from 2D projection data, which is referred to as ‘‘cone-beam reconstruction.’’ The first and most popular approximate reconstruction scheme for cone-beam projections acquired along a circular trajectory is the algorithm according to Feldkamp and colleagues , referred to as the Feldkamp, Davis, and Kress (FDK) method. This algorithm, used by most research groups and commercial vendors for CBCT with 2D detectors, uses a convolution-back projection method. Although it can be implemented easily with currently available hardware and is a good recon- struction for images at the center or ‘‘midplane’’ of the cone beam, it provides an approximation that causes some unavoidable distortion in the noncentral transverse planes, and resolution degradation in the longitudinal direction. To address this deficiency, several other approaches have been proposed using different algorithms and cone-beam geometries (eg, dual orthogonal circles, helical orbit, orthogonal circle-and-line), and these will no doubt be incorporated into future CBCT designs. Cone-beam CT image production Current cone-beam machines scan patients in three possible positions: (1) sitting, (2) standing, and (3) supine. Equipment that requires the patient to lie supine physically occupies a larger surface area or physical footprint and may not be accessible for patients with physical disabilities. Standing units may not be able to be adjusted to a height to accommodate wheel- chair-bound patients. Seated units are the most comfortable; however, fixed seats may not allow scanning of physically disabled or wheelchair-bound patients. Because scan times are often greater than those required for pan- oramic imaging, perhaps more important than patient orientation is the head restraint mechanism used. Despite patient orientation within the equipment, the principles of image production remain the same. The four components of CBCT image production are (1) acquisition configuration, (2) image detection, (3) image reconstruction, and (4) image display. The image generation and detection specifications of currently avail- able systems (Table 1) reflect proprietary variations in these parameters. Acquisition configuration The geometric configuration and acquisition mechanics for the cone- beam technique are theoretically simple. A single partial or full rotational  CBCT: TECHNICAL FUNDAMENTALS 711 Table 1 Selected CBCT imaging systems. Unit Model(s) Manufacture/distributor Accuitomo 3D Accuitomo - XYZ J. Morita Mfg. Corp., Kyoto, Slice View Tomograph/ Japan Veraviewpacs 3D Galileos d Sirona Dental Systems, Charlotte, North Carolina Hitachi CB MercuRay/CB Hitachi Medical Systems, Tokyo, Japan Throne i-CAT Classic/Next Imaging Sciences International, Generation Hatfield, Pennsylvania ILUMA Ultra Cone Beam IMTEC Imaging, Ardmore, Oklahoma; distributed CT Scanner by KODAK Dental Systems, Carestream Health, Rochester, New York KaVo 3D eXam KaVo Dental Corp., Biberach, Germany KODAK 9000 3D KODAK Dental Systems, Carestream Health, Rochester, New York NewTom 3G/NewTom VG QR, Inc., Verona, Italy/Dent-X Visionary Imaging, Elmsford, New York Picasso Series Trio/Pro/Master E-Woo Technology Co., Ltd./Vatech, Giheung-gu, Korea PreXion 3D TeraRecon Inc., San Mateo, California Promax 3D Planmeca OY, Helsinki, FInland Scanora 3D Dental conebeam SOREDEX, Helsinki, Finland SkyView 3D Panoramic imager My-Ray Dental Imaging, Imola, Italy scan from an x-ray source takes place while a reciprocating area detector moves synchronously with the scan around a fixed fulcrum within the patient’s head. X ray generation During the scan rotation, each projection image is made by sequential, single-image capture of attenuated x-ray beams by the detector. Technically, the easiest method of exposing the patient is to use a constant beam of radiation during the rotation and allow the x-ray detector to sample the attenuated beam in its trajectory. However, continuous radiation emission does not contribute to the formation of the image and results in greater radiation exposure to the patient. Alternately, the x-ray beam may be pulsed to coincide with the detector sampling, which means that actual exposure time is markedly less than scanning time. This technique reduces patient radiation dose considerably. Currently, four units (Accuitomo, CB Mercu- Ray, Iluma Ultra Cone, and PreXion 3D) provide continuous radiation exposure. Pulsed x-ray beam exposure is a major reason for considerable variation in reported cone-beam unit dosimetry. Field of view The dimensions of the FOV or scan volume able to be covered depend primarily on the detector size and shape, the beam projection geometry, 712 SCARFE & FARMAN and the ability to collimate the beam. The shape of the scan volume can be either cylindric or spherical (eg, NewTom 3G). Collimation of the primary x-ray beam limits x-radiation exposure to the region of interest. Field size limitation therefore ensures that an optimal FOV can be selected for each patient, based on disease presentation and the region designated to be im- aged. CBCT systems can be categorized according to the available FOV or selected scan volume height as follows: Localized region: approximately 5 cm or less (eg, dentoalveolar, tempo- romandibular joint) Single arch: 5 cm to 7 cm (eg, maxilla or mandible) Interarch: 7 cm to 10 cm (eg, mandible and superiorly to include the inferior concha) Maxillofacial: 10 cm to 15 cm (eg, mandible and extending to Nasion) Craniofacial: greater than 15 cm (eg, from the lower border of the mandible to the vertex of the head) Extended FOV scanning incorporating the craniofacial region is difficult to incorporate into cone-beam design because of the high cost of large-area detectors. The expansion of scan volume height has been accomplished by one unit (iCAT Extended Field of View model) by the software addition of two rotational scans to produce a single volume with a 22-cm height. An- other novel method for increasing the width of the FOV while using a smaller area detector, thereby reducing manufacturing costs, is to offset the position of the detector, collimate the beam asymmetrically, and scan only half the patient (eg, Scanora 3D, SOREDEX, Helsinki, Finland) (Fig. 2). Fig. 2. Novel method of acquiring an extended FOV using a flat panel detector. (A) Conven- tional geometric arrangement whereby the central ray of the x-ray beam from the focal source is directed through the middle of the object to the center of the flat panel detector. (B) Alternate method of shifting the location of the flat panel imager and collimating the x-ray beam laterally to extend the FOV object. (Courtesy of SOREDEX, Helsinki, Finland; with permission.)  CBCT: TECHNICAL FUNDAMENTALS 713 Scan factors During the scan, single exposures are made at certain degree intervals, providing individual 2D projection images, known as ‘‘basis,’’ ‘‘frame,’’ or ‘‘raw’’ images. These images are similar to lateral and posterior-anterior ‘‘cephalometric’’ radiographic images, each slightly offset from one another. The complete series of images is referred to as the ‘‘projection data.’’ The number of images comprising the projection data throughout the scan is de- termined by the frame rate (number of images acquired per second), the completeness of the trajectory arc, and the speed of the rotation. The num- ber of projection scans comprising a single scan may be fixed (eg, NewTom 3G, Iluma, Galileos, or Promax 3D) or variable (eg, i-CAT, PreXion 3D). More projection data provide more information to reconstruct the image; allow for greater spatial and contrast resolution; increase the signal-to-noise ratio, producing ‘‘smoother’’ images; and reduce metallic artifacts. How- ever, more projection data usually necessitate a longer scan time, a higher patient dose, and longer primary reconstruction time. In accordance with the ‘‘as low as reasonably achievable’’ (ALARA) principle, the number of basis images should be minimized to produce an image of diagnostic quality. Frame rate and speed of rotation. Higher frame rates provide images with fewer artifacts and better image quality. However, the greater number of projections proportionately increases the amount of radiation a patient receives. Detector pixels must be sensitive enough to capture radiation ade- quate to register a high signal-to-noise output and to transmit the voltage to the analog and the digital converter, all within a short arc of exposure. Within the limitations of solid-state detector readout speed and the need of short scanning time in a clinical setting, the total number of available view angles is normally limited to several hundred. Completeness of the trajectory arc. Most CBCT imaging systems use a com- plete circular trajectory or a scan arc of 360 to acquire projection data. This physical requirement is usually necessary to produce projection data adequate for 3D reconstruction using the FDK algorithm (see section on reconstruction). However, it is theoretically possible to reduce the complete- ness of the scanning trajectory and still reconstruct a volumetric data set. This approach potentially reduces the scan time and is mechanically easier to perform. However, images produced by this method may have greater noise and suffer from reconstruction interpolation artifacts. Currently, this technique is used by at least two units (Galileos and Promax 3D). Image detection Current CBCT units can be divided into two groups, based on detector type: an image intensifier tube/charge-coupled device (IIT/CCD) combina- tion or a flat-panel imager. 714 SCARFE & FARMAN The IIT/CCD configuration comprises an x-ray IIT coupled to a CCD by way of a fiber optic coupling. Flat-panel imaging consists of detection of X rays using an ‘‘indirect’’ detector based on a large-area solid-state sensor panel coupled to an x-ray scintillator layer. Flat-panel detector arrays pro- vide a greater dynamic range and greater performance than the II/CCD technology. Image intensifiers may create geometric distortions that must be addressed in the data processing software, whereas flat-panel detectors do not suffer from this problem. This disadvantage could potentially reduce the measurement accuracy of CBCT units using this configuration. II/CCD systems also introduce additional artifacts. CBCT systems that use flat-panel detectors also have limitations in their performance that are related to linearity of response to the radiation spec- trum, uniformity of response throughout the area of the detector, and bad pixels. The effects of these limitations on image quality are most noticeable at lower and higher exposures. To overcome this problem, detectors are linearized piecewise and exposures that cause nonuniformity are identified and calibrated. In addition, pixel-by-pixel standard deviation assessment is used in correcting nonuniformity. Bad pixels are also examined and most often replaced by the average of the neighboring pixels. A reduction in image matrix size is desirable to increase spatial resolution and therefore provide greater image detail. However, detector panels com- prise an array of individual pixels with two components, photodiodes that actually record the image and thin-film transistors that act as collators and carriers of signal information. Therefore, not all of the area of an imager is taken up by the photodiode. In fact, the percentage area of the detector that actually registers information within an individual pixel is referred to as ‘‘fill factor.’’ So although a pixel may have a nominal area, the fill factor may be of the order of 35%. Therefore, smaller pixels capture fewer x-ray photons and result in more image noise. Consequently, CBCT imaging using smaller matrix sizes usually requires greater radiation and higher patient dose exposure. The resolution, and therefore detail, of CBCT imaging is determined by the individual volume elements or voxels produced from the volumetric data set. In CBCT imaging, voxel dimensions primarily depend on the pixel size on the area detector, unlike those in conventional CT, which depend on slice thickness. The resolution of the area detector is submillimeter (range: 0.09 mm to 0.4 mm), which principally determines the size of the voxels. There- fore, CBCT units, in general, provide voxel resolutions that are isotropic (equal in all three dimensions) (Fig. 3). Image reconstruction Once the basis projection frames have been acquired, data must be pro- cessed to create the volumetric data set. This process is called reconstruc- tion. The number of individual projection frames may be from 100 to  CBCT: TECHNICAL FUNDAMENTALS 715 Fig. 3. Comparison of volume data sets obtained isotropically (left) and anisotropically (right). Because CBCT data acquisition depends on the pixel size of the area detector and not on the acquisition of groups of rows with sequential translational motion, the compositional voxels are equal in all three dimensions, rather than columnar with height being different from the width and depth dimensions. more than 600, each with more than one million pixels, with 12 to 16 bits of data assigned to each pixel. The reconstruction of the data is therefore com- putationally complex. To faci