0 Bitewing TechniqueThe following slides describe techniquesused in taking bitewing films.In navigating through the slides, you should click onthe left mouse button when you see the mouseholding an x-ray tubehead or you are done reading aslide. Hitting “Enter” or “Page Down” will also work.To go back to the previous slide, hit “backspace” or“page up”.
Patient PreparationPrior to starting to take films, the patient must bepositioned properly. Seat the patient and ask themto remove their glasses and any removable partialdentures or orthodontic appliances. Adjust theheadrest to support the head while taking films.Raise or lower the chair to a comfortable height forthe operator. Place the lead apron and thyroid collaron the patient. You are now ready to begin takingfilms.It is a good idea to inform the patient about thenumber of films you will be taking so they knowwhat to expect, especially when doing a full-mouthseries.
Bitewing FilmThis film gets its name from the tab (“wing”) that thepatient bites on to hold the film in place. Thebitewing film is used for the detection ofinterproximal caries and the condition of the alveolarbone. This film shows the crowns of both themaxillary and mandibular teeth and a portion of theroots.A premolar film and molar film are normally taken oneach side for a total of four posterior bitewing films.
Head PositionThe head is normally positioned so that the maxillaryarch is parallel to the floor and the midsagittal plane(MSP) is perpendicular to the floor. This is a definiterequirement when using bitewing tabs to hold the film inposition; it is not as important when using the RinnBitewing Instrument. MSP head supported by headrest
Bitewing Film Placement TabsThe traditional method of bitewing placement uses tabs. Thetab in the photo below left is attached to a sleeve throughwhich the film is inserted. The disadvantage to this type oftab is that the film can move forward or backward as thepatient closes. The preferred type of tab, below right, sticksto the white side of the film and does not allow the film tomove during closure.
Bitewing Film Placement Bitewing InstrumentThe Rinn Bitewing Instrument pictured below isfrequently used instead of tabs. The instrumentfacilitates placement and the ring insures correctalignment of the PID.
Rinn Bitewing Instrument Instrument set-upThe prongs on the bar are aligned with the holes inthe biteblock and the two are attached. The ring isplaced on the bar so that it is centered on thebiteblock.
Rinn Bitewing InstrumentBefore placing the film in the biteblock, the filmshould be bent gently around a finger (whiteside down, long axis in line with finger).
Rinn Bitewing InstrumentPlace the film, white side facing ring, under onetab, centered front to back, and then gently placethe opposite edge of the film under the other tab.The film may curve slightly away from the ring. Thelocation of the identifying dot on the film is notimportant.
Rinn Bitewing InstrumentMake sure the all-white side of the film is visiblethrough the ring (White-in-sight). You are now readyto place the film in the mouth. This set-up works forboth sides of the mouth (Instrument does not needto be changed).
Bitewing Technique Film Position (Same for tabs or Rinn BW instrument)The premolar bitewing film is approximately centered onthe 2nd premolar; the front edge of the film should be atleast in the middle of the canine. The molar film iscentered on the 2nd molar if the third molars are present.The long axis of the film is horizontal.The position of the film dot doesn’t matter; it will bebeyond the crowns of the teeth on the film. long axis premolar molar (3rds)
Bitewing Technique Film PositionIf the third molars are not erupted into the mouth, it is notnecessary to position the film to cover the third molarregion. It is better to move the film slightly forward,centered on the contact between the first and secondmolars. This gives you duplicate information in the secondpremolar/first molar areas, which may aide in making adiagnosis in these areas. molar (no 3rds)
Bitewing Technique Film PlacementIt is important to always start with the premolar bitewing.This allows apprehensive patients or those with activegag reflexes to somewhat get used to the film beforeproceeding to the more posterior molar film. Both filmson one side should normally be completed beforemoving to the other side. However, if a patient hasproblems with gagging on the premolar film, Irecommend immediately going to the other side andtaking the premolar film. Once the two premolar films aretaken, you can attempt to take the molar films.
Vertical Angulation (with tabs)When the film is positioned in the mouth, the upperportion of the film is angled approximately +20° as itcontacts the palate. In the mandible, the film is upright(0° angle). The average between these two angles is+10°. This +10° is the vertical angulation selectedwhen using bitewing tabs. +20º 0º
Vertical Angulation (with tabs)Adjust tubehead so that the 10° mark is opposite theposition guide. The 10° setting may be above or below thezero mark, depending on which way the tubehead isrotated around the supporting yoke (see photos middleand right below). The PID must be angled downward forall positive angulations; if it is angled upward it is anegative angulation. 10° position guide
Make sure the maxillary arch is parallel to the floor and themidsagittal plane is perpendicular to the floor beforealigning the tubehead. In the photo below left the PID isangled downward at 10 degrees as recommended, but thepatient’s head is tipped to the side. Rotating this samepicture (below right) to position the maxillary arch parallelto the floor (dotted line) shows that the true angle of thePID is upward in relation to the film. This will give adistorted image. +10°
Vertical Angulation (with instrument)When using the Rinn BW instrument, align the PIDwith the ring. This automatically aligns the x-raybeam with the correct vertical angulation, no matterhow the head is positioned.
Horizontal Angulation (with tabs)The horizontal angulation is adjusted so that a lineconnecting the front and back edge of the PID (yellow linebelow) is parallel with a line connecting the buccal surfacesof the premolars and molars (green line below). The x-rayswill then pass straight through the contact areas between theteeth. The front edge of the PID should be ¼” anterior to thefront edge of the film to keep the beam centered on the film. correct incorrect
Horizontal Angulation (with instrument)When using the Rinn BW instrument, align the PIDwith the ring. This automatically aligns the x-ray beamwith the correct horizontal angulation, assuming thefilm was positioned properly in the mouth. (Seefollowing slide).
The film should be equidistant from the teeth in an anterior-posterior direction (the distance from the front edge of thefilm to the lingual surface of the teeth should be the same asthe distance from the back edge of the film to the lingualsurface of the teeth). The film should be positioned in thismanner for both the premolar and molar radiographs. Thishelps to avoid overlap (see “Errors”). correct incorrect incorrect
When aligning the PID, have the patient “smile big” with theirteeth together; this allows you to see the buccal surface ofthe posterior teeth when using tabs. When using the Rinninstrument, this helps you make sure the patient is bitingcompletely, not just tightening their lips around theinstrument. The center of the x-ray beam (dotted line) shouldbe directed at the occlusal plane; this centers the beam topto bottom.
Where teeth are missing, it is often necessary to use acotton roll to help support the tab or instrument. Positionthe film in the mouth and then slide the cotton roll into theedentulous area. Make sure the cotton roll does not reston top of the occlusal surface of the teeth that arepresent. cotton roll
In the film at left, a cotton roll wasnot used and the tab and filmdropped down into the edentulousarea, resulting in a tipped film.In the film at left, a cotton roll wasused, keeping the tab and longaxis of the film parallel with theocclusal plane.
0Another thing to consider when there are edentulous areasis to position the bitewing tab forward or backward on thefilm so that the tab comes in maximum contact with theteeth that are present. In the premolar placement below, thetab was moved forward for maximum contact with themandibular premolars. For the molar film, the tab would bemoved toward the back end of the film to contact the 2ndmolar.
The film may be angled in the mouth tofacilitate anterior placement when usingthe tabs. As long as the horizontalangulation is aligned properly, the teeth willnot be overlapped. When using tabs, make sure the film clears the palatal gingiva as the patient closes to keep the film from being pushed down into the mandible.
0If lingual tori are present, the film must be placed lingual tothe torus (both with tabs and the instrument). When usingtabs, it is often helpful to attach another tab to the oneattached to the film; this lengthens the portion you hold onto, making it easier to position the film more toward thetongue and lingual to the torus. film torus extra tab extra length tab on film
Bitewing Films 0Premolar Bitewing: covers Molar Bitewing: coversboth premolars, first molars molars. In this patient,and at least a portion of with no third molars, thesecond molars. film was positioned too far posteriorly.
Bitewing FilmsIf third molars are not erupted into the mouth, the molarfilm should be positioned more anteriorly, as seen above.Make sure ¼” of film extends posterior to second molarso that the distal aspect of both upper and lower secondmolars, including the bone, can be seen.
Bitewing FilmsIn some patients, one film may cover all posterior teethif the third molars are not present. This can often bedetermined during film placement or by looking atprevious films. If you’re not sure, take both premolarand molar films.
Bitewing FilmsIf the first premolars are missing (often seenwith orthodontic patients) and the third molarsare not present, one bitewing per side isenough.
Bitewing FilmsIf it is determined that bitewing films are needed ona patient that is completely edentulous in one arch,a complete denture may be left in the mouth to helpsupport the bitewing tab or bitewing instrument. Themaxillary complete denture is used in the filmabove.
Vertical BitewingFor the routine bitewing film, the long axis of the film ishorizontal (side-to-side). In patients with advancedperiodontal involvement, the bone loss may be soextensive that it does not show up on the normalbitewing. For these patients, some dentists prefer to havethe bitewing film positioned with the long axis placedvertically (up-and-down). This is called a vertical bitewing. long axis
Vertical BitewingTwo bitewings (premolar and molar) are normally taken oneach side posteriorly, just as with regular bitewings, for a totalof four posterior films.If indicated, vertical bitewings can also be taken in theanterior region. A total of three anterior films would be used:one centered on the midline to show the incisors and one oneach side to image the canine regions. right right right incisor left left left molar premolar canine canine premolar molar
Vertical BitewingVertical bitewing films can be taken using tabs or abitewing instrument, just as with regular bitewings.The vertical angulation is +10° with tabs; the PID isaligned with the ring when using the instrument.The horizontal angulation is determined in the samemanner as it is with regular bitewings. The object isto open the contacts between the teeth on the film.
Bitewing Technique ErrorsThe following slides identify some of the mostcommon errors seen when using the bitewingtechnique.
OverlapIf the horizontal angulation is not aligned correctly, so thatthe x-rays pass through the teeth contacts at an angle, thecontact areas will be overlapped (see arrows on filmbelow).Overlap is the superimposition of part of one tooth withpart of the adjacent tooth (dotted circles below left). Thered arrow represents the direction of the x-ray beam; thex-ray beam should be perpendicular to the dotted linebelow. (See discussion of horizontal angulation on earlierslide).
OverlapSometimes overlap is unavoidable due to the malpositionof some teeth. One or more teeth may be more buccal orlingual than the adjacent teeth, resulting in crowding andchanging the angle of contact between these teeth. Thearrow in the film below points to an example of this typeof overlap.If the majority of contacts are open on a film, with only afew areas overlapped, this would not be considered anerror.
Improper Film PlacementImproper film placement is a common error seen inthe bitewing technique. In the premolar film belowleft, the film was placed too far back, cutting off themesial of the first premolar. In the molar bitewing,below right, the film was not back far enough,cutting off the distal aspect of the third molars.
Improper Film PlacementIf the top edge of the film contacts the palatal gingivalledge, the film may be pushed down into the floor ofthe mouth as the patient closes. This results in abitewing that looks more like a periapical film, asseen in the two films below. This is more likely tohappen when using tabs.
Cone CuttingIf the x-ray tubehead is not positioned properly, the x-raybeam may not cover the entire film. This is known asconecutting, which results in a clear (white) area on the filmwhere the silver halide crystals were not exposed to x-rays(see films below). In the diagram below right, the dottedcircle represents where the x-ray beam should have beenpositioned; the solid circle shows the actual position of the x-ray beam (too posterior).
Patient MovementIf the patient moves or opens the mouth slightlyduring exposure, a blurred or distorted image mayresult. The film below was produced when thepatient opened the mouth partway through theexposure. It looks similar to a double exposure.
Reversed Film 0If the tab is placed on the colored side of the film or thefilm is placed in the bitewing instrument with thecolored portion facing the ring, the lead foil in the filmpacket will be between the teeth and the film. Thisresults in the pattern stamped on the lead foilappearing on the film (see small dark squares on rightside of film below). The film will also be lighter than theother films taken at the same time.
Unnecessary FilmsThe patient below has no second or third molars onthe right side. The premolar film is all that is neededon this patient. The patient received uneccessaryexposure by taking the molar film. M PM
Unnecessary FilmsThis patient had a complete upper denture and alower partial denture which replace all the molars onthe left side. This film showing only denture teethshould obviously not have been taken.
Full Mouth SeriesThe paralleling and bisecting angle techniques are used totake periapical films and have nothing to do with thebitewing technique. When taking a full mouth series on apatient with a full compliment of teeth, four bitewing filmsare normally taken. These are combined with 15periapicals (# 1 films used anteriorly) when using theparalleling technique or 14 periapicals (# 2 films usedanteriorly) when using the bisecting angle technique.Paralleling full mouth series of periapicals + 4 bitewings =19 filmsBisecting angle full mouth series of periapicals + 4bitewings = 18 films