Cons.Lec#9: Diagnostic imaging in interpreting caries

Reference: Oral radiology principles and interpretation, 6thedition, dental caries chapter, written by White and Pharaoh.

80% of dental procedures are built on problems related to caries.

The goal of any professional dentist is the early detection of caries in other words diagnosis of caries early enough to prevent its progression or at least perform the most conservative management to keep the tooth in it’s ideal shape for the best prognosis for longertime.

Dental problems are summarized in the following:

- Dental caries - Periodontal diseases - Congenital dental anomalies - Trauma - Mucosal lesions

Dental caries, periodontal diseases and congenital dental anomalies are the most prevalent problems affecting most people at some point of their life.

In the past it was known that caries is an infectious disease causing tooth destruction. However caries in a contemporary setting is known as a dynamic process having a progression phase which can be stabilized accordingly the disease can be reversed.

*Prevalence of the disease:

50% of six years old children are caries free due to used preventive protocols (fluorosis). On the other hand 20% of the population have 80% of the caries worldwide thus the disease is not widely distributed.

Occlusal caries are more common than interproximal ones due to the fact that fluorosis reacts better with smooth surfaces than pits and fissures ; pinpointing the diagnostic method the dentist going to use i.e. using specific tools for different sites of the tooth.

*Morphology of the lesion:

Caries appears as a small notching on the surface and it goes bigger deep down; subsequently, it’s clinical form is not 1:1 to the actual histologic appearance.

Dental lesions can be classified according to the degree of the activity into the following types:

- Arrested (stable) lesions - Progressive lesions

Note that the degree of activity of the lesion depends mostly on the tooth mineral status and the preventive method used by the patient.

*Diagnostic tools

Each diagnostic tool has it’s specificity and sensitivity.

For example I can’t distinguish Small enamel lesions which look as white chalky spotsfrom radiographic perspective (as one of the diagnostic tools) therefore it’s sensitivity and specificity are low.

Cavitated lesions are clearly evident.

Time needed for white lesions to progress into cavitated lesions and vice versa depends on several factors such as oral hygiene status , diet and age .

Radiographically, Invisible lesions require 12-18 months to become clearly obvious.

Dentinal lesions are the easiest as they are large and apparent.

The major diagnostic tool is careful visual examination in a dry well lit field.

What do we look for in visual examination?

- White chalky lesions - Discoloration - Cavitaion

tactile

Some dental schools disagree with using a probe as a diagnostic tool due to the fact that immature dentists don’t have the ability to estimate the amount of pressure needed to be applied in a way not to create a carious lesion and because when using it on different surfaces you cross contaminates them . Other schools allow the careful use of blunt probes .

The following two tools are sophisticated ones used in laboratories more than clinics.

Caries have low mineral contents and high water content thus have structural and physical abnormalities (abnormal crystal shape) accordingly caries will have different electrical conductivity and different light refraction.

Electrical conductivity measurements. Refraction of light

The upcoming fancy tools work around the same principle but in different techniques.

fiber optic transillumination Digital image fiber optic transillumination Light fluorescence DIAGNOdent: the most commonly used in clinics . Quantitative light induced fluorescence

Radiographs

** Radiographs are categorized into below categories:

- Conventional - Digital - Intra-oral - Extra-oral- Three dimensional

How to choose the appropriate diagnostic tools?

1) Does it cover the current clinical situation with it’s details?2) What are the clinical factors that may affect the sensitivity and specificity of

the tool? 3) Is it easy to be used? Do I need extra training before using it ?4) How much it costs ?

Radiographs:

Is an adjunct tool for diagnosis dental caries.

As mentioned earlier the major diagnostic tool is visual examination in a dry well lit field.

Uses:

1) To detect the presence of caries. 2) To evaluate the site and the size. 3) To determine if the dentist creates a direct or indirect pulp capping.4) To follow up with the therapy.

Types:

- Periapical radiographs ( the one the students use in the endodontic lab)

Showing the apical area only

- Bitewing radiographs : the ideal radiographs for caries detection.

It is an intra-oral radiograph taken when the patient is clenching his teeth showing the maxillary and mandibular teeth in the same radiographic image .

The following image shows a bitewing radiograph.

Bitewing is better because its 5 degrees angled, not like periapical in which you change geometry ( in maxilla you go little upward to take the whole tooth and its surrounding & in mandible you go more downward). When you change geometry you change the place of the lesion & the extent of the lesion (Later on insh’alla we’ll take more about its physics) . But for now Bitewing radiograph is the ideal way for caries detection.

*Interpretation (caries or not caries)

It’s a puzzle, no such tool that give us 100% specificity, accuracy, sensitivity, +ve/-ve prediction values. Its like a piece of puzzle that you sum with the clinical case that have &then you make your decision. : it's like looking at paintings and trying to figure out the implications (who draw it, if there is something differs it from other paintings in the nearby cities) so they start Analyze how this person dresses, hairstyle, hat ….. etc, they found that he have rheumatoid arthritis.

Its like art; enough clues and clinical signs to have this diagnose . its 50/50 chance , when you show 10 dentists a radiograph of small lesion 6 of the them will argue with the others. So we are behind in the detection of small

carious lesion although dentistry started many years ago and many faculties are present now.. so don’t feel sad if you argued about it .

*Histological section of caries helps in detection of caries on radiographs *

*Detection according to location:

-proximal -occlusal - fissure

- recurrent: beneath any restorative work ex. Fillings or crowns

- rampant caries : extensively distributed, really generalized

Ex. Proximal caries; begin under the contact point looks like pyramid in enamel (triangle base outside) and the same thing in dentin (and the apex will be toward the pulp), so if the apparent shape is inversed or highly above the contact point you should put it into consideration we you look at it

*According to size :

>Proximal

-Incipient: no active management, no drill and fill, preventive management only.

Its hard to see it on radiograph not easy forward, take another picture after 6 months

“Caries are darker than enamel & dentine on radiographs; less mineral content and more water content”

-Moderate :

You need to differ between root caries and classII; to know where to start your cavity, overall prognoses, management , if it’s a root caries then pt have gingival rescission .. so many info you gain.

-Advanced: Large goes half way dentine. Moderate and advanced need active management.

-Sever: pt can’t sleep.

> Occlusal caries: (pits and fissures)

It’s the weak spot of radiography, if you detect it on radiography its high moderate to sever. Much easier to detect clinically by nice visual examination and well dried field.

> Facial and lingual caries: wont be seen unless they make enough contrast, they have to be big enough to be seen in a radiograph (because there's buccal & lingual wall that will cover each other)

>Root caries: located on the root.

Small occlusal lesion 6 and extensive

occlusal lesion 6, apart from the small approximal enamel lesion, the enamel cap appears intact.

> Recurrent caries: any caries under a filling, you’ll encounter this a lot because pts think once they have a filling its immune to disease and wont floss and clean.

Root caries lower 7 and

recurrent caries upper 5

Bitewing showing the radiolucency of

residualcaries beneath the

restoration in 5 (arrowed)

>Rampant caries: easy to diagnose (detection) – by definition: generalized caries & very hard to treat (management reasons: *Medical reasons ; diminished salivary flow,

chemotherapy, radiotherapy, transplants, drugs. *Social issues: chronic alcoholics, drugs addicts, bad diet habits, sipping..

We start treatment by phaseI therapy ,stabilize the carious lesion everywhere drill all the caries, quadrant by quadrant ; point of success to know why caries went all this way.

> Pre Eruption Caries: is a very interesting entity– an impacted tooth (unerupting tooth) defected by a caries before eruption, it's not completely isolated from the oral cavity (because if its isolated it won't get caries) there's a small communication with the oral cavity –no S.mutants no caries – its related of dietary intake and how much sugar. Partially or fully impacted teeth in the soft tissue have communication point between the follicle of the tooth and the oral cavity,so it gets the disease before eruption. Very rare.

** 4×4 table, from a clinical prospective:

A specific tooth (surface) either have caries (+ve for disease) or not (-ve for disease)

Your test either; your eye, optical, electrical or radiograph tells you: YES there is caries, or NO you can't judge if there is.

+ve -ve

+ve D+ D-

-ve T+ T-

D+ , T- = True +ve

D-, T- = True –ve

D- ,T+ = False +ve ( you think there is carious lesion and you go with the high speed hand piece all the way in enamel and dentine and find nothing!)

D+ ,T- = False –ve ( you told the pt that he’s fine and everything is good and after 6 months he came with a carious lesion!)

- you have to accept false –ve & false +ve, and we manage it according to the disease, how fatal is it we try to make early detection , is the treatment is expensive on the pt’s health, time , effort.

** Caries are a matter of perspective:

Gondal: a classic researcher on caries diagnose found that the sensitivity=0.5 (true +ve fraction) of bitewing radiographs for a small enamel lesion– BUT the specificity= 0.9 better(true –ve fraction), that when you tell that there is no caries, you can be more confident.

Wensile: found that the difference between digital radiographs and film-based radiographs is not that much.

** Enough demineralization is needed to the carious lesion as carious lesion.

- Emitaters & Detracters:

There are a lot of things that your brain see it NOT just your eyes; that means if you have a good quality radiograph, viewing environment, if there are artifacts, the anatomy and the "emitaters & detracters". Sometimes in bitewings there is overlap, so if there are small lesions on one of the surfaces you won't be able to visualize them - and you will be less confidence about what you can see in the bitewing radiograph.

1.Cervical burn-out:

Root is oval in shape with the thickest part in the center, the thin cervical part between the crown and root appears dark; photons enter it & appear like caries on radiographs, this is called cervical burn out.

How to differentiate between root caries and cervical burn out:

1. Take another radiograph from different angle2. Root caries have gingival rescission; clinical correlation 3. Cervical burn-out is not a lesion so it appears gradual 4. Outer outline of the root is smooth and continues; caries make rough irregular

surface.

The idea about white & black in a radiograph is related to the: Density & Thickness of the structure.

Denser & Thicker more white

- Teeth are oval in shape (in the centre are thick, in the periphery are thin)- CEJ: above there is enamel covering the crown (enamel=dense tissue) below there is

bone around the tooth.

But there is an area that NOT covered by neither the enamel (just cementum) or the bone and the periphery seems thinner the weakest area seen in radiographs seems darker than other (below & above more shinny white) its NOT caries

<<< Diagram illustrating the radiographic

appearance of cervical burn-out. B Bitewing

radiographshowing extensive cervical burn-out of the premolars(arrowed). Compare this with the appearance of

cervicalcaries on distal aspect

upper 6.

2. Mach Bands: Is something you can detect it with your eyes:

-enamel is dense, dentine is not as dense you can't handle this abrupt change between enamel & dentine you can't see the DEJ in a white line (there is must be an gradual grayish change in color)

This is something illusion in your brain. Why it isn't caries? >>> It isn't pyramid shape in enamel . It isn't internal resorption >> because it need a viable cells >> from the pulp >> it starts really deeper into the tooth, but this is very superficial.

3. cusp of carpille: appear white & the surrounding looks relatively black

4. External root resorption: may also look like root caries.

Best of Luck!

Aroob Al-Hyari

Overlapping of obturated canals in the mesial root causes faint mach band along arrows.

Arrows point to a radiolucent line (mach band enhanced by background

density effect) that was diagnosed as a possible vertical root fracture by an

AEGD student.

Distinct, albeit fictitious, radiolucent line (mach band) may be seen at the junction of the crestal

bone margin and roots in posterior teeth.