Dentin Caries

The first stage of dentinal decay begins below the enamel caries before any clinical sign of cavitation. In the first radiographically detectable stage of enamel caries, dentin changes are not visible. The diffusion of acid from the enamel lesion into the dentin causes demineralization of the mineral component but leaves the collagen matrix of the dentin intact. However, once the bacteria enter the enamel, they spread along the dentin-enamel junction to attack dentin over a large area. The lesion is, therefore, conical its broad base at the junction of the enamel and dentin with and apex towards the pulp.  
Dentin infection is facilitated by the dentinal tubules, which form an open path for bacteria, once they have been slightly enlarged by acid attack. After demineralization, the dentin matrix is gradually destroyed by the proteolytic enzymes secreted by the bacteria.   
Streptococci play the main role in attacking enamel, but bacteria on the advancing front of the dentin forms a diverse flora of facultative anaerobes and anaerobes. Commonly isolated species include Lactobacilli, Actinomyces, Bifidobacterium, and Eubacterium, with S. mutans in varying amounts, the latter probably contributing to faster progression. The flora is proteolytic and more dependent on the dentin matrix for nutrients than dietary sugars.   
Decalcified dentin initially retains its normal morphology. Once the bacteria reach the enamel junction, they spread along the tubules, quickly fill them, and spread along all the side branches. Tubules spread from the expanding masses of bacteria and their products, that the softened matrix cannot confine. Subsequently, the walls of the intermediate tubules are destroyed and the collections of bacteria in the adjacent tubules combine to form irregular foci of liquefaction. These, in turn, combine to induce progressively more extensive tissue destruction. Eventually, the dentin is completely destroyed. In some areas, cracks filled with bacteria form at right angles to the general direction of the tubules. Clinically, these cracks can allow the excavation of carious dentin in fragments in a plane parallel to the surface.   
Decay in dentin, therefore, presents areas of demineralization, bacterial penetration, and destruction of dentin. The degree of destruction of dentin is essential for restorative treatment. Even in the area of bacterial penetration, much of the dentin structure is intact and can remineralize. It is, therefore, possible to restore a tooth leaving cavities and bacteria under the restoration, provided that the restoration is of high quality and obtains an adequate adhesive peripheral seal. No bacterial substrate can therefore reach the bacteria, the caries process stops and the dentin can remineralize.   
The dentinal caries is then divided into areas, caries affected and caries infected. Dentin affected by decay is demineralized and its matrix is only partially degraded; part of the tubular structure remains and the number of bacteria is low. On the contrary, the area infected with decay, clinically identifiable as soft, wet, and brown, is largely demineralized, has no intact residual matrix to remineralize, neither tubules nor a large number of bacteria. The area infected with decay cannot remineralize effectively and provides little support for restoration. It usually needs to be removed.   

Protective reactions of dentin and pulpal caries  

The spread of caries in dentin is considerably slowed down by a series of defense reactions mounted by vital dentin and pulp and mediated by odontoblast activity. These reactions are nonspecific and can be caused by other irritants such as friction, erosion, abrasion, and restorative procedures. The dentin changes begin even before the cavity forms in the enamel, but it takes time and is, therefore, more likely to grow prominently under the slowly progressing decay. Dentin is deposited by the original odontoblasts, both as peritubular dentin and pulp. Once the odontoblast dies, defense reactions within the dentin cannot occur, but reactive dentin can form. This is a faster response of odontoblast-like cells which differentiate from pulp cells. are possible as long as the pulp is not devitalized. The changes in dentin start to develop early, but at best, they can only slow the progression of tooth decay. Densely mineralized translucent dentin is also vulnerable to bacterial acid and proteolysis, and once bacteria enter normal dentin, they can invade the reactionary and reparative dentine to reach the pulp.   

Online ADC MCQ Part 1 Written Examination Preparation: Sample Test Paper

This paper has been prepared for the benefit of ADC candidates for practice purpose. Copying for commercial purpose is prohibited. For non-commercial use, contact us.

To take the test, click HERE.

Sequelae of Infection of Dental Pulp

Periapical infection with Streptococci & Staphylococci

Majority of streptococci produce hyaluronidase, an enzyme that dissolves hyaluronic acid which is a universal intercellular cementing substance. It helps in the spread of infection. Usually staphylococci are good producers of hyaluronidase, so there is no spread of infection and the infection becomes localised in the form of abscess in case of staph infection.


Photograph showing Pulpal hyperaemia.While bacteria are still some distance from the pulp,
acid permeating along the dentinal tubules gives rise
to dilation of the blood vessels, oedema and a light
cellular inflammatory infiltrate in the pulp [1]

What is Pulpitis?

Pulpitis is the inflammation of the pulp. It is the most common cause of pain in young persons.


It is of two types.

  1. Reversible

  2. Irreversible

Irreversible pulpitis has been divided into further two types

  1. Acute pulpitis

  2. Chronic pulpitis

Causes of Pulpitis

New Blue Print of ADC Written Examination

The success in examination of Australian Dental Council depends on the rigorous practice. Once you understand the format of the written part 1 examination, the type & pattern of questions, you can easily crack it.

ADC Written Examination Format

The part 1 ADC exam will have 4 sections that will be conducted in 2 days. Two section will be held in one day. There will be a break for rest between two sections. The whole ADC part 1 exam will be conducted in two consecutive days. To make it further clear you can see below in fig 1 in a diagrammatic representation.

adc written exam format
Fig 1. Structure and timings of ADC written examination format.

Each section will have 70 questions of which 56 will be scenario based. Remaining 14 question may vary in type that you will come to know later on in our various courses. There will be five options and you will have to chose one best correct option as your answer. Thus, there will be total 280 questions in ADC part 1 written examination. Out of 280 questions, 40 questions will have no marks which means they will not be scored. The ADC has put them there for calibration and testing purpose. It means 240 questions will be marked or scored and you will be declared pass or fail based on the marks obtained on scored questions. Scored and unscored questions will be unknown to you. This means you should treat all 280 questions as scored questions, as you do not know which question will contribute towards your success. The duration of each section will be of 70 minutes.

Blue Print of Written Exam

The written examination blueprint describes the content covered and the approximate percentage of questions allocated to each content area. The written examination blueprint is shown in table 1 given below.

adc written exam blueprint
Table 2. ADC written exam blue print. (Source: ADC handbook for written examination) Click to see full image.

Passing Requirements of ADC Written Part 1 Examination

To pass the written exam, you must pass in each of four cluster separately. See below to understand the clusters in a better way.

  • Cluster 1: It encompasses professionalism and health promotion aspect.
  • Cluster 2: It is related to the clinical information gathering.
  • Cluster 3: It will check your ability of making diagnosis and management planning.
  • Cluster 4: it will check your ability to perform clinical treatment and its evaluation.

To pass each cluster separately, you need to achieve either “A” or “B” grade. If you get grade “C” or “D” it means you failed the ADC part 1 written exam. The meaning of different grades are as given below

Grade A: Your score was more than 10% above the passing score. You got a clear pass.
Grade B: Your score was within 10% above the passing score. You got a close pass.
Grade C: Your score was within 10% below the passing score. You got a close fail.
Grade D: Your score was more than 10% below the passing score. You got a clear fail.

So, getting a grade C or D means the ultimate result is same for you, as you need to retake the part 1 written exam to be eligible for part 2 practical examination.

The ADC does not set a passing mark and it has a complex mechanism of evaluation that you can see in the written examination hand book if you are interested.

Getting your results

Written examination results are usually available within six weeks of the examination but may take longer. You will be notified when your written examination results are available and how to access your results.

Journey of a Dentist for ADC Exam


This story of a dentist tells about the journey of a dentist for ADC exam and the mental, physical and economic sufferings full family went through after his failure.

Ganesh was a general dental practitioner with a nice practice in a class two city. Isha was a tutor in a Dental college in the same city. The couple had been living a happily married life with their 5 years old son and their parents in a joint family.

ADC Exam: Written & Practical explained


The Australian Dental Council conducts a series of assessment exams for accreditation of the scientific knowledge, technical and clinical skills and ability to make a clinical judgement in relation to patient care of an overseas dentist whose dental graduate degree is not recognised by the Dental Board of Australia.

Once an overseas dentist successfully clears the assessment process, he or she can register with DBA as a GP and can practice Dentistry in Australia.

Australian Dental Council assessment process is a three-stage process. The first is the initial assessment that I have already explained in the episode 1 of our video series. Now, in episode 2 of the video series, I shall explain written as well as practical exams. After going through this video, you will become familiar and confident with every aspect of the exams.

Sample MCQ Paper


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1. ADC Examination: Initial Assessment Process Explained

The ADC examination process along with initial assessment has been explained in this article. You can also watch the video for the same if you are unwilling to read the text.

The dentist who has got his or her bachelor dental degree from a non-Australian institution needs to pass the skill assessment test/examination conducted by the Australian Dental Council and register themselves in Dental Board of Australia to practice as a general dentist in Australia or to get a job in public or private sector.

The ADC test/examination is a screening examination to establish that dentists trained in dental schools which have not been formally reviewed and accredited by the ADC have the necessary knowledge and clinical competence to practice dentistry. 

Following are the steps, an overseas dentist needs to go through to qualify the ADC examination: 

Exopsure Time for Dental Radiography

The exposer time for dental radiography is dependent upon the speed of the film whether its ‘D’ or ‘E’. The exposer time for various areas is given in the table below.

For exact data, you can see the instructions written on the inner side of the carton of the film. The modern microprocessor controlled radiography machines are coming with software that takes care of everything. You need to place the film properly, choose whether the patient is an adult or child, choose the tooth/area desired and shoot the film. You must take care of yourself and your staff for radiation protection. For radiation protection, read the article given below:

Radiography: Radiation Safety



  1. Oral Radiology Principles and Interpretation 5th Ed

Overseas Registration Examination (ORE)

If you do not want to read the text, you can listen this presentation on YouTube at this link Overseas Registration Examination

What is the Overseas Registration Examination (ORE)?

ORE means Overseas Registration Examination. It is an exam that overseas qualified dentists have to pass because their dental bachelor degrees are not recognised by GDC. After passing ORE, a dentist can get registration in GDC and he or she will be allowed to practise dentistry unsupervised in the UK. The ORE tests the clinical skills and knowledge of overseas dentists who  are referred to as a candidate. Candidates are expected to be at equal or above the standard of a ‘just passed’ UK BDS graduate. A candidate should be able to show competence, knowledge and familiarity in the different aspects of dentistry in the exam. 

The ORE has two parts

The​ Part 1 is designed in such a way that it tests candidates’ application of knowledge to clinical practice. ORE part 1 consists of two computer-based exam papers:

Paper A covers clinically applied dental science and clinically applied human disease. Basically it will check your ability to apply your knowledge of non clinical subjects to understand its role in human diseases.

Paper B covers aspects of clinical dentistry, including law, ethics, health and safety. It means paper B will check your ability to treat patients taking care of existing laws of the UK, ethics, and safety. Each paper lasts three hours and is made up of multiple short answer questions. They will contain extended matching questions and single best answer questions. A candidate is expected to be able to show competence, knowledge and familiarity in the different aspects of dentistry.

You need to achieve a minimum 50% marks in each paper to pass the part 1 of ORE. There are a maximum of 200 places available at each examination period. You must pass both papers in order to progress to Part 2. 

Location and Cost of Overseas Registration Examination

The Part 1 exam is held at King’s College London and costs £806. There are currently no confirmed dates for 2021. Your exam results will be sent to you by email. Generally it is declared within 20 working days of the examination. You will be given a percentage mark out of 100 for paper 1 as well as paper 2. Also, you will get an overall pass or fail award. Approximately 40 working days after the examination, the Part 1 Supplier, King’s College London, will provide you with result feedback. Upon passing Part 1, your name will be added to the Part 2 candidate list. You will be allowed four attempts for Part 1. 

Part 2 of ORE 

Part 2 is designed for candidates to demonstrate practical clinical skills. For each examination period, a maximum of 144 candidates are able to undertake the Part 2 exam. The current cost of the examination is £2,929 per candidate, payable at the time of booking. 

Part 2 Examination Dates: 

There are currently no confirmed dates for 2021 part 2.

Four Components of Part 2 of the ORE:

  1. DM,
  2. OSCE,
  3. DTP &
  4. EM 

First component is An operative test on a dental manikin: Candidates are required to perform three procedures over a period of three hours. These procedures primarily involve the preparation and restoration of teeth, but may also include other procedures where appropriate simulation can allow assessment of operative skills. 

Second component is An objective structured clinical examination (OSCE).  This is where candidates visit a series of ‘stations’ which test their clinical skills. These may include history-taking and assessment, communication skills such as an explanation of problems and treatment plans, judgement and decision making, ethics and attitudes, and clinical examination. The series of stations will cover aspects of behavioural sciences, human disease, law, ethics, professionalism, clinical dentistry, restorative dentistry, paediatric dentistry, orthodontics, preventive dentistry, dental public health, comprehensive oral care, oral surgery, oral medicine, oral pathology, oral microbiology, dental radiology and imaging.

Third component is A diagnostic and treatment planning exercise (DTP):  This involves an actor who will provide an appropriate history. You will be provided relevant additional information such as photographs, radiographs, study models or results of other special tests. You will not examine the actor. The exercise may involve any of the above aspects of clinical dentistry I just mentioned.

Fourth component is a practical examination in medical emergencies (ME).  This assessment consists of two parts: First is a structured scenario-based oral and the second is a demonstration of single handed basic life support. This will include cardiopulmonary resuscitation using a resuscitation manikin. You will be allowed four attempts for Part 2. Your exam results will be sent to you by email. The result will be declared within 20 working days of the exam. If you only fail the medical emergencies exercise during the ORE Part 2 , you will be able to re-sit this component only at a future exam. Sitting the ME only exam costs £300. If you pass the ME component at this sitting, you will have passed Part 2 of the ORE. If you fail, you will need to retake the full ORE Part 2 exam, if you are eligible to do so. The ME only exam is held at the same time as the full Part 2 exam. Once you have passed Part 2, you will be able to apply for registration with the GDC.   

Books Recommended for ORE Preparation

  • Oxford Handbook of Applied Dental Science
  • Oxford Handbook of Clinical Dentistry 6
  • Scully’s Medical Problems in Dentistry, 7 e
  • Master Dentistry: Volume 1
  • Master Dentistry: Volume 2
  •  Essentials of Dental Radiography and Radiology-Eric Whaites
  • Vanders Physiology
  • BD Chaurasia for Anatomy



Odontogenic Keratocyst




Image Source: Recurrence of odontogenic keratocysts and possible prognostic factors: Review of 455 patients (

Dentigerous/Follicular Cysts

Dentigerous (Follicular) Cysts are the second most commonly occurring odontogenic cysts after periapical cyst and the most common developmental cysts of the jaws. By definition, a dentigerous cyst is attached to the tooth cervix (enamel-cementum junction) and encloses the crown of the unerupted tooth.

image dentigerous cyst
Photograph: Dentigerous cyst surrounding the crown of right mandibular third molar and going upward in ascending ramus. [1]

Etiology and Pathogenesis of Dentigerous Cyst 

A dentigerous cyst originates from the enamel organ remnant or reduced enamel epithelium. The expansion of the dentigerous cyst is related to epithelial proliferation, release of bone-resorbing factors, and an increase in cyst fluid osmolality. 

Clinical Features of Dentigerous Cyst 

Dentigerous cysts are most commonly seen associated with third molars and maxillary Canines. The peak incidence of dentigerous cysts occurs between twenty to 40 years. Males have more predilection with a ratio of l.6 to 1.  

Dentigerous cysts are generally symptomless. The delayed eruption is the most common indication of dentigerous cyst formation. This cyst can achieve significant size, occasionally causes cortical bone expansion but rarely reaches a size that predisposes the patient to a pathologic fracture. 

Radiographically, a dentigerous cyst manifests as a well-defined, unilocular or sometimes multilocular radiolucency with corticated margins in attached with the crown of an unerupted tooth. The concerned unerupted tooth is mostly displaced. In the mandible the related radiolucency may extend superiorly from the third molar site into the ramus or anteriorly and inferiorly along the body of the mandible. In maxillary dentigerous cysts in the canine region, extension into the maxillary sinus or to the orbital floor may be seen.

image dentigerous cyst
OPG radiograph showing dentigerous cyst associated with right mandibular third extending in to the ramus and ascending body. [2}


The cyst is lined by stratified squamous epithelium. In a noninflamed dentigerous cyst the epithelial lining is nonkeratinized. It remains approximately four to six cell layers thick. Sometimes, numerous mucous cells, ciliated cells, and rarely, sebaceous cells may be found in the lining of the epithelium. The epithelium-connective tissue junction is generally flat. But when secondary inflammation established, epithelial hyperplasia may be noted.

image histopathology of dentigerous cyst
Microscopic structure of Dentigerous cyst [4]

Differential diagnosis

When it is small, it is difficult to differentiate a dentigerous cyst from a large but normal dental follicle. When larger, the differential is essential that of lytic lesions of the jaw and includes:

  1. periapical cyst
  2. aneurysmal bone cyst
  3. ameloblastoma
  4. odontogenic keratocyst
  5. fibrous dysplasia
  6. Stafne cyst


Removal of the associated tooth and enucleation of the soft tissue part is definitive therapy in most cases. When cysts affect significant portions of the mandible, exteriorization or marsupialization of the cyst is done to allow for decompression and subsequent shrinkage of the lesion followed by surgical enucleation. 


  1. J Can Dent Assoc 2012;78:c59

Periapical/Radicular Cyst

A cyst is defined as “an epithelial lined pathologic cavity”. The periapical/radicular cyst is an odontogenic cyst. The classification of the cysts can be seen HERE.t is important to read for ADC Exams or NEET MDS purpose.

Periapical/Radicular cyst

Periapical cysts are inflammatory cysts. Their epithelial lining originates from the odontogenic epithelium of the tooth buds that remains within periodontal ligaments (epithelial rests of Malassez) after completion of tooth maturation. Due to inflammatory response, the epithelial rests of Malassez start proliferating and provide cystic lining.

Dental Amalgam: SAQs for Viva Voce

SAQ 1. A patient arrives at your office and expresses concern about mercury from dental amalgam causing her harm. What will you tell this patient to reassure her about the safety of amalgam? 


You will tell about three facts of dental amalgam fillings:

(1) The mercury that is in an amalgam is not free and never released into the body. It is always tied up chemically in the dental amalgam matrix. The majority of bound mercury never leaves the dental amalgam mass.

Hepatitis B: Treatment & Prevention

Hepatitis B is a potentially life-threatening liver infection caused by the hepatitis B virus (HBV). It can cause chronic infection and puts people at high risk of death from cirrhosis and liver cancer.

In the first part of the article, you have read the epidemiology, mode of transmission of Hepatitis B virus, its sign and symptoms, groups at risk, the relationship of HBV and HIV infection, and how the diagnosis is confirmed. In this part of the article, we shall discuss about its treatment and prevention.

If you want to read a short note on Hepatitis B in Indian context, read it HERE.

You can take a Mock test on Hepatitis B.

Measures to Evaluate a Screening Test

For ADC examination, both prelims and practical viva voce, and NEET MDS,  the various measures of evaluating a screening test must be known to the students.

There are various measures to evaluate a screening test that are as follows:

Hepatitis B: Epidemiology & Clinical Features

Hepatitis B is a potentially life-threatening liver infection caused by the hepatitis B virus (HBV). It can cause chronic infection and puts people at high risk of death from cirrhosis and liver cancer.

In this first part of the article, we shall discuss the epidemiology, mode of transmission of Hepatitis B virus, its sign and symptoms, groups at risk, the relationship of HBV and HIV infection, and how the diagnosis is confirmed. In the second part of the article, you will read about treatment and the prevention of Hepatitis B.

Oral Ulcers: Clinical features, Causes & Treatment

An ulcer is a tissue defect which has penetrated the epithelial-connective tissue border, with its base at a deep level in the submucosa, or even within muscle or periosteum. An ulcer is a deeper breach of the epithelium than an erosion or an excoriation, and involves damage to both epithelium and lamina propria.

Dentin Caries

The first stage of dentinal decay begins below the enamel caries before any clinical sign of cavitation. In the first radiographically detec...

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