Radiology

Bitewing film quality: A clinical comparison ofthe loop vs. holder techniquesSuwadee Kositbowornchai, DDS, Dr med dentWipsuda Phadannorg, DDS=/Montira Permpoonsinsook, DDS^/BanditThinkhamrop, PhD^

Objective: To compare in vivo bitewing film quality using the holder versus the paper loop technique.Method and materials: Four bitewing films were taken from the right and left premolar and molar regionsof 45 dental students using both the bitewing holder and paper loop techniques. A total of 360 films weretaken and assessed by an experienced practitioner not apprised of the bitewing technique used. Of inter-est were: (1) the number of overlaps and the percentage of teeth showing the aiveolar crest: ¡2) proper filmpositioning: and (3) the percentage of cone cutting. A Poisson regression using generalized estimatingequations (GEEsj was used to estimate the difference in overlap between the two techniques. For properpositioning and cone cutting, icgistic regressions using GEEs were used. Results: The average number ofhorizontal overlaps for the loop and holder techniques at the right premolar, right molar, left premolar, andleft molar were 1.64, 2.11, 2,16.2.78. and 1.64,2.00,2.00,2.18, respectively. The loop technique was1.11 times more likely fo cause overlapping than the holdertechnique. The highest percentage of teethshowing the alveolar crest by the loop technique was 97.8% in the mandibular second premolar and Prstmolar. With respect to film positioning, the loop technique was 1.12 times more likely to cause improperpositioning than the holder technique. Bofh fechniques demonstrated minimal cone cutting (1 in the loopversus 0 in the holder). Condusion: The quality of bitewing fiims taken by the ioop and holder techniqueswas not significantly different. (Quintessence Int 2004:35:321-325)

Key words: bitewing, coverage, holder, loop, mefhod, overlap, protfimal, technique

CLiNiCAL RELEVANCE: Practitioners should know thatthe quality of bitewing film depends on radiographer's skillmore than techniques used.

Bitewing radiographs are particularly valuable in de-tecting interproximal caries in posterior teeth.' ^

They are also useful for evaluating the periodontal con-dition because they reveal the level of the alveolar crestclearly. Bitewing radiographs have heen adopted forindividual diagnosis and screening. According to thedisease, lesion activity cati be monitored by comparingradiographs taken at intervals,^ just as Stephen et aP

•Associate Professor. Department of Oral Diagnosis, Faculty of Dentistry,

E<hon Kaen University, Ktion Kaen. T>iailanü.

'Deparirrent of Oral Diagnosis, Faculty oí Dentistry, Kt»n Kaen University,

Khon Kaen, Ttiaiiand.

^Department ot Biostalistics and Demography, Faculty of Public Health,

Kfion Kaen University, Thailand.

Reprint requests: Dr Suwadee Kositbowo.nchai, Department of OralD S O ' Í S F . c . ^ of Demlsf:y, Khon Kaen Universrty. KoCn Kaen 40002Thailand. E-mail: suwadee@mail.kkuac.1h

found 93*0 of radiographs taken during follow-up werebiteiving radiographs. Standardization of the hitewingradiograph protocol would aid in its effective use.

The quality of bitewings affects interpretation andsubsequent treatment. The most common error affect-ing interpretation of hitewing radiographs is overlap-ping at the interproximal surfaces of adjacent teeth dueto incorrect horizontal angulation.^" Sewerin* studiedthe number and distribution of proximal overlaps andfound only lg -o of the proximal surfaces studied didnot have overlaps, Rimmer and Pitts* reported thatmesial surfaces were overlapped more than distal ones.Lerwik and Cowley- studied the quality of hitewingradiographs in Norwegian children hetween the ages of9 and 11 years and found that caries of the enamelcould not he confirmed on 200.0 of approximal sur-faces, as 50% had been incorrectly placed in themouth. Nysether and Hansen'" showed only 4.6% ful-filled the criteria for correct bitewing radiographs.

The diagnostic value of hitewing radiographs is de-pendent on the quality oí radiography, which in tum is atechnique-sensitive procedure." Good qualitj' bitewingradiography requires procedures that reduce overlaps.poor film placement, and cone cutting.'^'^

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• Kositbowornchai et ai

Two major methods of bitewing radiography are theloop and holder techniques. The loop technique is theconventional method wherein quality depends primar-ily on the radiographer's experience. The bitewingholder technique was adopted to reduce the need forrepeated exposures by preventing both horizontal andvertical angulation errors. The use of film holders wassuggested to reduce the error caused by beam align-ment," Beyer-Olsen and Eggen'' found that the holdertechnique gave higher reproducibiliiy than the looptechnique. However, Harrison and Richardson'^ ob-served that the use of a film holding device in childrendid not improve quality of bitewing radiographs or di-agnostic yield. The purpose of the present study was tocompare the in vivo diagnostic potential achieved bythe conventional freehand bitewing technique usingthe paper loop versus the holder technique. The threetypes of errors were: fl) overlapping of teeth; (2)proper positioning of the film; and (5j cone cutting.

METHOD AND MATERIALS

Patient selection

Dental students at Khon Kaen University receivingtheir complimentary annual checkups were referredfor bitewing radiographs. Forty-five of them met theinclusion criteria for the current study:

1, Having posterior permanent teeth including one ca-nine, two premolars, and at least two molars in eachquadrant and symmetrical arch,

2, The tooth surface had no interproximal restoration,crown, fixed partial denture, or any orthodontic ap-pliances,

3, The tooth surfaces had proximal contact and nodiastema.

The Ethics Committee at Khon Kaen University ap-proved the study in conformity with the HelsinkiDeclaration,

Radiographic procedure

Radiographs were taken on two occasions, 6 monthsapart. The second occasion was a caries-status check.At the first visit, each subject was randomly assigned apair of bitewings (premoiar and molar) using the paperloop on one side and the holder on the other (RinnBiteWing Instrument, Rinn), Six months later, themethod used for each side was reversed. The radiogra-pher had 3 years' experience as a general dental practi-tioner. After taking each image, the radiographer wasnot allowed to check the quality of the radiograph.

The radiograph machine used was a GX-70M(Asahi Roentgen) operating at 70 kVp 10 mA with anopen-ended, lead-lined cone. The exposure time was0,45 seconds for the premolar region and 0,67 secondsfor the molar region. The tube-to-film distance was 20cm, Kodak Ultra-speed D film size No, 2 (EastmanKodak) was used and processed by an automaticprocessor (Level 360SL, Flat, Kobe-Shi) at 24''C for 4minutes,

Radiographic evaluation

A general dental practitioner (with 7 years experience)evaluated the 360 bitewing radiographs, not knowingwhich radiographie method was used. An illuminatedview box with a magnifier was provided. The standardviewing criteria used for assessing the quality of tbebitewing radiographs were;

1, Proximal surface overlaps were counted when thehorizontal distance between two points on the ex-ternal surfaces of overlapped tooth surfaces wasfound. Six sites of premolar and four sites of molarfilm were assessed for overlaps, and averages werecalculated. The eorrect vertical angulation was de-termined by counting tbe number of teeth for whichtbe alveolar crest sbowed at least 5 mm, measuringfrom the cementoenamel junction,

2, The proper positioning of the film required^: (a)premolar bitewing radiograpbs tbat ineluded thedistal surfaces of the canine to the mesial surfacesof the first molar; (b) molar bitewing radiographsthat included the distal surfaces of the second pre-molar to the distal surfaces of the second molar.The number of films which met these criteria weredeemed properly positioned films,

3, Cone cutting was defined as a clear unexposed areawhere the radiation beam did not completely coverthe film. The occurrence of all these errors wasrecorded.

Statistical analysis

The number of horizontal overlaps occurring becauseof the two techniques were compared using Poissonregression using generalized estimating equations(GEEs), The proper vertical angulation was presentedas the percentage of teeth showing the alveolar crest.The eomparisons of proper film positioning and conecutting between the fwo techniques were evaluatedusing a logistic regression and GEEs,

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Kositbowornchai et al

u 90

g 70• | 60£ 505 403 30£ 30° 10Z 0

• Loop, maxillary• Holder, maxillary BR• Loop, mandiQjIar K i• Holder, mandibular ^ H

47 47

37 Baa B

1 — « ^ ^ J _ ^First Second

premolar premolar

ea

K

n—M^MFirst

molar

Fig 1 Distribiition of teetti associated with clearly seen alveolarcrests in premolar film. For each group (loop, maxillary, fiolder.maxiilary; loop, mandibular; and holder, mandibular), n = go.

TABLE 1 Mean number of overlaps of right and leftpremolar and molar bitewing films by technique

Mean overlaps per tilm (minimum/maximum)

Area

flight premolarflight molarLeft premolarLeft molar

Bitewing loop

1.6(0/4)2.1 (0/4)2.1 (0/5)2.7 (0/4)

Bitewing holder

1.6(0/4)2.0 (0/4)2.0 (0/4)2.2 (1/4)

1 90-

1 60ñ 50'1 401 30•5 200 10

0

• Loop, maxillary• Holder, maxillary• Loop, mandiDular• Holder, manditiular

46

m^ 1Second

premolar

SOBO

- ^First

molar

8777H

35 ^ ^ 1

Secondmolar

Fig 2 Distribution of teeth associated with clearly seen alveolarcrests in molar film. For each group (loop, maxillary; holder, maxil-lary; loop, mandibular, and holder, mandibular), n = 90.

TABLE 2 Number of proper film positions

Area

Right premolarRight molarLett premolarLett molarTotal

Loop technique

Proper

12

35

7

36

90

Improper

33

10

38

g

90

Holder technique

Proper

15

40

6

34

95

Improper

30

5

39

11

85

RESULTS

The mean number of overlaps in each area of bothtechniques, minima and maxima, arc shown in Table1. The average number of horizontal overlaps per filmin the loop and holder techniques at the right premo-lar, right molar, left premolar, and left molar were 1.6.2.1, 2-2. and 2.8 and 1-6, 2.0. 2-0, and 2.2. respectively-The differences benveen means were compared, andthe loop technique was found 1-11 times more likelyto show overlapping than the bolder technique (gS 'oconfidence interval [CI]: 0-96 to 1.28; P = -153).

Figures 1 and 2 show the distribution of teethclearly associated with the alveolar crest seen in tbepremolar and molar films, respectively. In both tech-niques, the alveolar crest of the mandibular teeth wasseen more clearly than that for the maxillary teeth, andthe distribution of teeth sbowing tbe alveolar crest wassimilar in botb. In tbe premolar films from tbe holdertechnique, 41-l''.ó of the maxillary first premolar re-vealed the alveolar crest. In the molar films done withthe holder technique, the mandibuiar second premo-lars sbowed the alveoiar crest in only 26.70/0 of cases-

Table 2 sbows tbe number of proper film positionsin each area of investigation. Tbe distribution patternfor the number of properly positioned films was notsignificantly different between techniques- The bite-

wing radiographs of the molar area were better posi-tioned than tbe premolar. By comparison, the looptecbnique was 1.12 times more likely to be improperlypositioned tban the holder technique (QS o CI; 0.74 to1-96: P = .598)-

Tbere was minimal cone cutting induced by eitbertecbnique: the loop technique gave one cone-cutting

e, while none was produced by the holder technique.

DISCUSSION

The current study was designed to assess the value ofthe holder technique as an aid in improving bitewingfilm quality in clinical practice.

Tbe proximal surface overlap is an important factorin evaluafing bitewing film quality because it affects di-agnosis and treatment. A survey'" of the tj'pes and fre-quencies of errors on bitewing films revealed 10.0%were overlaps, while 42.7''.o were incorrect position,and 4.5flo were cone cutting- Jensen et al' surveyed 25dental pracfitioners in New York and found the per-centage of unreadable proximal surfaces caused byoverlap or distortion ranged between 6.3 and 59-5 inthe permanent dentifion and between 12-5 and 24.9 intbe primary. No difference in overlap between tbebitewing loop and holder tecbniques was obser\'ed.

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• Kosifbowoíochai étal

Sewerin^ reported the bitewing loop gave the same fre-quency of overlap as tbe Kwik-Bite film holder. Pitts etal" compared three different bitewing tecbniques invitro and found that a prototype film holder and beam-directing device produced the least overlap. Potter etal" studied the alignment reproducibility of the tbreebitewing techniques and found Ihe loop technique hadlarger mean horizontal errors than the Kwik-Bite andRinn XCP film positioning devices (P = ,0001).

An interpretative concern, where overlap occurs,is the presence of proximal radiopaque material. Sub-jects with proximal restoration, however, were ex-cluded to eliminate interpretive problems.

Reports of the level of the alveolar crest affectingbitewing film quality are rare. In the current study, adistribution pattern of tfie alveolar crest on bitewingfilms derived from eitber tbe loop or holder tech-niques, on premolar or molar films, was shown. Fewerteeth showed the alveolar crest on the anterior part ofthe film: first premolars on premolar films and secondpremolars on molar films. Regardless of the method,and with respect to anatomic structure, the films weremostly placed in the posterior position. More of thealveolar crest of mandibular teeth was revealed thanof maxillary teeth regardless of technique, except themandibular second premolars when using the holdertechnique for a molar film reflecting the negative verti-cal angulation used. Negative vertical angulation inthe loop technique is influenced by film placementand the radiographer's skill. When employing theholder technique, biting on tbe bite block can causenegative vertical angulation.

Tbe proper position of the film in the current studywas considered the standard position.'-" In clinicalpractice, however, some patients' dental arch andanatomic structures may interfere with film place-ment'^ Moreover, the clinician may not mind if thefilm does not perfectly cover all the teetb, btit that itcovers the tooth/teeth of interest. It was found theloop technique was often out of position, perhaps dueto the paper tab being softer than the bite block of theholder and movement during insertion into themouth. Notwithstanding, the soft paper tab causes lessdiscomfort to patients.

Cone cutting is another frequent error; it reducesinformation on the film, as the central radiographdoes not cover the film. The amount of cone cuttingdepends on the skill and experience of the practi-tioner. Since the holder technique requires equipmentthat uses an external ring to direct the beam of tbecentral ray, cone cutting is reduced. However, if apractitioner does not properly prepare the holder, thiserror could occur. In the current study, cone cuttingrarely occurred.

This study confirms the bitewing holder manufac-turer's claim of improved film placement and elimina-tion of cone cutting so practitioners, once concernedover diagnostic image quality, may use tbe holdertechnique without loss of quality.

When selecting a method for clinical practice, sev-eral factors should be considered, such as quality offilm, reproducibility, least possible x-ray exposure, lowcost, least discomfort to the patient, and speed. Mostbitewing holder techniques have received a positiverecommendation for clinical use." ' *" Zulqarnain andAlmas'^ suggested using the bitewing film holder tominimize the error or x-ray beam angulation. Shroutet al ' concluded that the film holder would be usefulfor reproducibility particularly when x-ray beam filmalignment errors are less tban 2.5 degrees. The bite-wing holder yields better reproducibility than thebitewing loop.'^'^^ In contrast, Harrison and Rich-ardson'^ showed the film holder technique did not al-ways improve the diagnostic yield, and the holder fre-quently was not well tolerated by patients. Thebitewing holder was useful for newly trained radiogra-phers and young dental students for reducing repeatsand exposure to x-rays. Moystad and Larheim™ foundno difference between the use of the two kinds ofbitewing holders by inexperienced students; however,tbey did not compare radiograph quality. Although theholder technique has received a positive endorsement,there are various kinds of construction that affectusage.

In the current study, the bitewing loop techniqueperformed by an experienced practifioner yielded nosignificant difference in film quality over the holdertechnique. The holder was more precise, but it had thedisadvantages of needing sterilization, causing patientdiscomfort, and higher cost. Since an experienced ra-diographer using either method can produce radio-graphs of acceptable quality, improving bitewing filmquality shotild be emphasized in training practitionersand their auxiliaries. In clinical practice, radiographsshowing only minor errors are acceptable if a techni-cally better radiograph is not likely to improve the ob-servahle information and the radiation dose to the pa-tient is a concern. However, the holder technique willlikely become routine clinical practice for digital radi-ography because of its suitability for holding sensors inthe mouth.

CONCLUSION

Bitewing film quality produced hy the loop techniquewas not significantly different from that produced bythe holder technique (P > .05).

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ACKNOWLEDGMENTS

The authors would like to Ihank ih¿ Faciili> of Denlistry. Khon KaenUniversiij. Tlwiland, who supported the sitidy. They also thank MrBryan Roderick Hamman of the Facullj of Medicine for Unguisticassistance.

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