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Permanent Maxillary Central Incisor

In our day-to-day conversation with friends and colleagues the teeth that we most commonly notice are the Permanent Maxillary Central incisor. Permanent Maxillary Central Incisors are the most prominent teeth among all the anterior teeth because of their position in the dental arch and greater mesiodistal dimension. The mesial surfaces of both the right and the left maxillary central incisor are in contact with each other. Like other incisors, the maxillary central incisor crown is wedge shape and has a single conical root.

Development and Eruption of Permanent Maxillary Central Incisor

The first time you will be able to see developing permanent maxillary central Incisors on a radiograph when the baby is 3-4 months old (initiation of calcification). The complete crown formation (enamel completion) occurs by the age of 4-5 years. The tooth emerges into the oral cavity by the age of 7-8 years by replacing the deciduous maxillary central incisor. The root of the permanent maxillary central incisor is completed by the age of 10 years. One tip to remember the root completion is the addition of 2-3 years into the age of eruption.

Labial Aspect of Permanent Maxillary Central Incisor

The incisor surface of the newly erupted maxillary central incisor contains three rounded protuberances called mamelons. These mamelons are lost later by the normal process of attrition. The crown has a smooth convex labial surface with faint developmental depressions. The developmental depression on the labial surface is mesial developmental depression, distal developmental depression, and imbrication lines. The mesial outline of the crown is straight and it forms a ninety-degree angle with the incisal ridge. The distal outline of the crown is convex and it forms a more rounded angle with the incisal ridge. The cervical line or the cementoenamel junction (CEJ) has a semicircular outline with curvature towards the root apex. The root of the maxillary central incisor is cone shape with a blunt root apex.

Palatal Aspect

The crown of the Permanent maxillary central incisor from the palatal aspect is rather irregular. The incisal and the middle portion of the crown are concave because of the presence of lingual fossa. The Palatal fossa sometimes referred to as the lingual fossa is surrounded by the incisal ridge, mesially and distally by the mesial and the distal marginal ridges, and in the cervical area by the cingulum. The cervical portion of the crown is convex because of the presence of the cingulum. The root is conical and narrower on the palatal aspect because of this convergence of the root in cross-section the root appears triangular.

Mesial Aspect of Permanent Maxillary Central Incisor

The maxillary central incisor from the mesial aspect appears wedge or triangular shape. The base of the triangle is towards the cervical portion of the crown while the apex is towards the incisal ridge. The incisal ridge of the tooth is in line with the apex of the root. The labial outline of the crown is slightly convex. The Palatal outline of the crown is convex in the region of the cingulum and concave at the marginal ridge. The curvature of the cervical line (cementoenamel junction) is towards the incisal aspect. The Maxillary central incisor has the greatest curvature of the cervical line on the mesial aspect than any other tooth. The root from the mesial aspect is smooth and conical with a blunt root apex.

Distal Aspect

The crown appears thicker from the distal aspect and it is because of the position of the crown over the root base to adapt to the curvature of the maxillary dental arch. This feature is more prominent in the maxillary lateral incisor. The curvature of the cementoenamel junction (CEJ) is towards the incisal ridge. The curvature of the cementoenamel junction is less if you compare it with the curvature of the cervical line present on the mesial surface of the tooth. Sometimes a developmental depression is present on the distal surface of the root.

Incisal Aspect of Permanent Maxillary Central Incisor

The incisal aspect of the tooth is broader mesiodistally on the labial aspect. The incisal and the middle portion of the crown labially is flat while the cervical portion of the tooth on the labial aspect is more convex. The crown tapers towards the lingual aspect and the cingulum makes the cervical portion of the crown lingually. Overall the crown from the incisal aspect has a triangular outline and the labiolingual dimensions are greater than the mesiodistal dimensions.

Variation and Anomalies

Sometimes the mesial and the distal marginal ridges and cingulum are more well developed and form a variation called ‘Shovel Shape Incisor’. Sometimes the size of the crown is larger than normal. A rare anomaly associated with this tooth is the small root.

Lecture of Permanent Maxillary Central Incisor

Permanent Maxillary Central Incisor on Models

June 13, 2021
Glass Ionomer Cement: Dental Cement

The glass ionomer cement (GIC) is available since the early 1970s and it is one of the most popular dental cement to date. It is derived from polycarboxylate and silicate cement. It contains the powder of the silicate cement and liquid of the polycarboxylate cement.

Dispensing and Composition of Glass Ionomer Cement

The GIC is available in two forms one is in the powder and liquid bottles and the second and the popular form is in the capsules. The encapsulated cement are popular these days because it offers various advantages as compared to powder and liquid bottles. In the capsule form, the proportion of the powder and liquid is already set by the manufacturer, mixing is quick and clean, less wastage of material, and reduction in the porosity in the final set material.

Powder of this cement comprises sodium alumino-silicate glass. In addition to the sodium aluminosilicate glass which is the main active ingredient the powder of the GIC also contains 20% Calcium fluoride (CaF) and other minor additives. The liquid contains an aqueous solution of the polyacrylic acid which is a weak acid as compared to phosphoric acid used in the silicate cement. Sometimes, alternative acids such as an aqueous solution of maleic acid are used in some products. The liquid of the GIC also contains tartaric acid which controls the setting characteristics of this cement.

The sodium alumino-silicate glass releases fluoride from the glass ionomer cement matrix and the fluoride release is associated with a reduction in the dental caries susceptibility of the adjacent tooth structure.

Setting reaction

The Sodium alumino-silicate glass which is the main active ingredient of the powder on mixing with the aqueous solution of polyacrylic acid forms cross-linked polyalkenoate salt. After placement of the glass ionomer cement, the material should be protected from the moisture using commercial varnish or Vaseline during the initial few hours otherwise the properties of the cement will be adversely affected.

After setting the cement matrix can release fluoride into the oral environment. The glass ionomer cement matrix also has the ability of fluoride absorption from the surrounding environment when the fluoride concentration is high for example after tooth brushing with a fluoride toothpaste or after use of fluoridated mouthwash. This process of fluoride release and fluoride absorption back into the glass ionomer cement matrix is referred to as the fluoride recharge mechanism.

Properties

The glass ionomer cement forms a chemical bond with the tooth structure and it offers a reasonable match with the natural tooth structure. The glass ionomer cement is a biocompatible dental material with very few adverse reactions. Acid used in this cement (Polyacrylic acid) is a weak acid as compared to phosphoric acid and the acid chains are large and immobile. Therefore, this cement produces only a short and mild pulpal inflammatory reaction.

The thermal diffusivity value of the glass ionomer cement is closer to that of dentin. The GIC has a thermal insulating effect and helps to protect the dental pulp from the thermal insults. Fluoride ions released by this cement matrix replaces the hydroxyl ions present in the hydroxyapatite structure and form fluorapatite which is more resistant to acid attack. There is recharge or top-up of fluoride in the cement matrix when the concentration of fluoride ions is high in the adjacent environment for example after the use of mouth wash or after brushing teeth with the fluoridated toothpaste.

Clinical applications or Uses

The glass ionomer cement is used to restore cavities where there is less stress for example in class 3 or class 5 cavities. It is a brittle material therefore it is not recommended to use it for restoring the incisal edges or restoring high stress-bearing areas. It is also use to restore cavities prepared with the hand instruments (Atraumatic restorative treatment). Glass ionomer is a material of choice for restoration of the deciduous teeth. This cement is used beneath composite resin or amalgam restorations. The GIC is also used for the cementation of fixed prostheses such as crown and bridges. The cement is also used for the cementation of orthodontic bands.

Types

The glass ionomer cement is mainly classified into three types.

Type 1: The type 1 is mainly used for cementation purposes for example cementation of the crown, bridges, and orthodontic bands.

Type 2: The type 2 is used for restorative purposes.

Type 3: The type 3 is used for lining and base applications.

Modified form of this cement is also known as Cermets and resin-modified glass ionomer cement (RMGIC). We will share the details about these two modifications in our upcoming blog.

Glass Ionomer Cement | Video Explanation

October 15, 2020
Silicate Cement: A rapid review of the most popular traditional cement

The two dental types of cement that have revolutionized dentistry in the past are the zinc polycarboxylate cement and silicate cement. Polycarboxylate cement is the first dental cement that forms a chemical bond with the tooth structure and silicate cement is the first cement that releases fluoride. These two dental types of cement result in the development of modern commonly used dental cement such as the Glass ionomer dental cement having beneficial properties of both the dental cement.

Dispensing form and Composition of Silicate cement

The silicate cement is also referred to as Silicophosphate cement in the literature. The cement was supplied as powder and liquid. The powder of the dental cement mainly comprises aluminosilicate glass powder which contains fluoride and liquid comprise of an aqueous solution of phosphoric acid.

Properties

The main disadvantage of using silicate dental cement is high solubility. This high solubility leads to loss of anatomical details of the restoration, degradation of cement margins, and discoloration of the restoration. Due to this high solubility of the this cement, the mean survival time of this dental cement is around four years. However, in patients maintaining optimal oral hygiene with minimal consumption of acidic foods and drinks the restoration may survive for twenty years or more. After the placement of cement into the cavity it is important to protect the cement from moisture as the contamination of cement with moisture further increases the solubility of this dental cement. It is a translucent material and before the introduction of glass ionomer cement and resin composite, it is a material of choice for esthetic restorations. Moreover, it has acidic Ph during the setting of the cement therefore to protect the vitality of the dental pulp lining is essential. The silicate cement has poor mechanical properties therefore it is used in cavities where is there is low stress such as class 3 cavities. One of the most important properties of silicate cement is the fluoride release. The material can release fluoride over a long period. Therefore, the incidence of dental caries around the silicate cement restorations is very low. The silicate cement is highly hygroscopic (absorbs moisture from the atmosphere) and it would adversely affect the setting time of the dental cement.

Clinical Applications

The silicate dental cement was used as tooth-colored filling material. After the advent of contemporary restorative materials such as glass ionomer cement and composite resin, the use of silicate dental cement declined markedly.

Silicate Cement | Dental Cement

October 8, 2020
Excessive salivation: An easy and instant guide
Excessive salivation is an uncommon complaint as compared to other complaints that are associated with salivary glands such as dry mouth, salivary gland obstruction, and bacterial infections, and inflammation. Excessive salivation can be a transient or a chronic problem depending on the etiology. In the medical and dental literature, the terms that are used to describe excessive salivation is sialorrhoea, hypersalivation, and ptyalism. The patients with excessive saliva usually present with the complaint of difficulty in swallowing and dribbling of the saliva.

Causes of Excessive Saliva

The excessive salivation is either due to increase formation of saliva by the salivary glands or due to a decrease in the clearance of saliva from the oral cavity due to compromised swallowing reflex. When the symptoms of excessive salivation are due to reduce clearance of saliva from the oral cavity it is referred to as false hypersalivation or false sialorrhoea.

Therefore, the causes of excessive salivation are broadly classified into two types:
1. Hypersecretion
2. Neuromuscular dysfunction or compromised swallowing
Hypersecretion

The hypersecretion of saliva is also referred to as true sialorrhoea. Numerous factors that may produce excess saliva such as wearing of an intraoral dental prosthesis or device such as dentures, orthodontic retainers or other orthodontic appliance for the first time, infected or ulcerated lesions of the oral cavity, early pregnancy, teething, drugs such as pilocarpine, mercury poisoning, and rabies.

Neuromuscular dysfunction or compromised swallowing

The salivary secretion is optimal but there is a problem in clearance or swallowing of saliva. This is also referred to as false sialorrhoea. Factors that produce neuromuscular dysfunction are carcinoma of the oral cavity, cerebral palsy, Parkinson’s disease, and cancerous or non-cancerous obstructions within the pharynx or esophagus. One of the physiological reasons that are sometimes misinterpreted by the parents as excessive salivation is in infants due to their developing swallowing reflex that results in the drooling of saliva.

Diagnosis of Excessive Saliva

The diagnosis of excessive salivation is usually based on the patient’s past medical history and intraoral examination. Sometimes confirmation of the excessive salivation is required. Excessive salivary secretion can be confirmed with a test called sialometry which demonstrates the salivary flow per minute.

Management of Excessive Saliva

For the management of any disease including excessive salivation it is important to address or eliminate the causative factor. Treatment of excessive salivation is also according to the underlying cause. Anticholinergic drugs are sometimes prescribed to suppress the salivary flow but these drugs may produce the symptoms of dry mouth and results in other complications such as dental caries and microbial infections.

In rare cases, through surgery, the opening of the major salivary ducts is redirected into the pharynx. Reassurance and patient and patient’s attendant education is important for every patient especially those with false sialorrhoea such as in infants.

Excessive Saliva
October 1, 2020
Dry mouth: Simple, informative, and evidence-based guide

Have you ever felt the dryness of mouth during the period of anxiety or stress for example during the period of your school examination? Dry mouth is also referred in the medical literature as xerostomia. Xerostomia is the most common salivary gland problem. It is estimated that dry mouth affects one in four individuals at some point in their life.
Dry mouth makes daily functions difficult such as speaking, eating, and swallowing.

Clinical features of Dry Mouth

There is dryness of oral tissues and soreness. The changes in the mucosa of the tongue are more prominent and characterized by the presence of red and atrophic appearance with prominent lobules and fissures on the surface of the tongue. Their loss of protective function that is associated with salivary flow leads to dental caries, fungal infections, and ascending bacterial sialadenitis. Patients with reduced salivary flow also report difficulty in speaking, mastication, swallowing, and difficulty in controlling dentures.

Causes of Dry Mouth

Medications are among the most common cause of dry mouth. Medications that cause dry mouth are anticholinergic drugs, tricyclic antidepressants, antihistamines, antihypertensive agents, cytotoxic drugs, and diuretics.
Radiation therapy uses to treat the head and neck cancers results in irreversible damage to the salivary glands. Systemic diseases and syndromes such as diabetes, acquired immune deficiency syndrome, ectodermal dysplasia, and Sjögren syndrome are associated with varying degrees of oral dryness. Dehydration because of high temperature and humidity or because of the use of diuretics also produces dry mouth. Psychogenic state, anxiety, and depression cause dry mouth due to an increase in sympathetic activity. In some patients, during the anxious state, there is abundant or excess saliva but the patient complains of dry mouth. Certain physiological states also produce dry mouth such as pregnancy.

Complications associated with Xerostomia

Due to reducing the salivary flow a plethora of adverse effects and complications develop in the dry mouth patients. These complications include more susceptibility to microbial infections such as dental caries, fungal infections, ascending bacterial infection and inflammation of the salivary gland, and halitosis or bad breath due to reduce the clearance of food by the saliva and increase microbial growth in the oral cavity.

Diagnosis of dry mouth

The diagnosis of dry mouth is based on the history of the patient and intraoral examination. Sialometry is performed to measure the salivary flow rate. The normal salivary flow rate is 0.1 ml/min. The salivary gland biopsy is performed to diagnose salivary gland neoplasia and Sjögren syndrome.

Treatment of Dry mouth

The dry mouth treatment is according to the cause and there no single management plan for patients with dry mouth. The following paragraphs will only outline the general management of a patient with dry mouth.
The dose of the drugs that produce xerostomia should be modified or some alternative drug should be used. The change in dosage of the drug or any alternative drug should be used in consultation with the patient general medical practitioner. The alcohol and tobacco should be avoided as they worsen the symptoms of xerostomia and also injurious to health. The chewing gums stimulate the salivary flow but the sorbitol containing chewing gums should be used as these are less cariogenic as compared to sucrose-containing chewing gums. The cholinergic drugs such as pilocarpine are prescribed to stimulate the saliva formation. These drugs are also referred to as sialogogues or the salivary gland stimulants but these drugs are only effective when there is residual healthy salivary tissue. Partial relief may be obtained by the administration of artificial saliva especially after radiation therapy. These artificial salivary substitutes are available over the counter. These available salivary substitutes lack the protective proteins that are present in the natural saliva.
In patients with dry mouth, the maintenance of Oral hygiene is essential to prevent dental decay and other bacterial and fungal infections. For maintenance of oral hygiene products with strong flavors and with alcohol should be avoided as these products may further irritate the oral mucous membrane. Similarly, sugar-containing products should be avoided as these products increase the susceptibility of dry mouth patients to dental caries.

Home remedies for dry mouth

Dry foods should be avoided as these worsen the symptoms of xerostomia. Water can be sipped throughout the day. Protect the lips with a lubricant such as petroleum jelly. Avoid hot and humid environments and consider placing a humidifier in the office or at home. Avoid caffeine-containing drinks that contain caffeine because of its diuretic effect. It is also important to avoid over the counter medications such as antihistamines as they worsen the symptoms of existing xerostomia.

Dry Mouth| Dry Mouth Causes and Management

September 18, 2020
Polycarboxylate cement: An exclusive guide for students
The polycarboxylate cement is also known as zinc polycarboxylate dental cement was the first dental cement that exhibits the property of chemical bonding with the enamel and dentin. Before polycarboxylate, the dental cement such as zinc oxide eugenol cement and zinc phosphate cement form the mechanical bond with the tooth structure.

Dispensing form and Composition of Zinc Polycarboxylate cement

The polycarboxylate dental cement is supplied as a powder and liquid bottles. The powder of the zinc polycarboxylate dental cement comprises zinc oxide powder which is the key ingredient. The powder also contains a smaller amount of magnesia, tin oxide, bismuth oxide, and alumina. The powder of the zinc polycarboxylate cement in some modified forms contain fluoride salts such as stannous fluoride. The amount of fluoride release from these modified polycarboxylate cement is insignificant as compared to the glass ionomer cement. The liquid of the dental cement comprises an aqueous solution of polyacrylic acid.

The setting reaction

The setting reaction of the zinc polycarboxylate dental cement is an acid-base reaction that is between zinc oxide present in the powder and polycarboxylic acid present in the liquid. The reaction results in the formation of a matrix in which the polyacid chains are cross-linked with zinc ions.

The biocompatibility of the cement is fairly good. This cement is non-injurious to the dental pulp and it forms chemical adhesion with the structure of the tooth. It is used in patients with a history of post-operative sensitivity. This cement is non-injurious to the dental pulp because for two reasons polyacrylic acid is a weak acid as compared to phosphoric acid present in the zinc phosphate cement, secondly, the polyacid chains are too large to penetrate the open dentinal tubules.

Clinical Applications Polycarboxylate cement

The following are the uses of zinc polycarboxylate dental cement.
1. It is used for the cementation of crown, bridges, and inlays.
2. It is also used as a cavity base material under metallic restorations such as dental amalgam to protect the vitality of the dental pulp. The zinc polycarboxylate dental cement is not used in the deep cavities as a base material and alternative cavity lining materials are used such as Calcium hydroxide cement. Although Polycarboxylate cement is more biocompatible as compared to zinc phosphate cement because of its weak acidic property but it forms a rubbery consistency during setting. The cement adheres to the stainless steel dental instruments making handling during placement and cleaning of instruments after placement of this dental cement more difficult.
3. Another use of the zinc polycarboxylate cement is for the cementation of orthodontic bands and the cementation of orthodontic appliances. Now it is less commonly utilized for orthodontic band cementation as new materials with better mechanical properties together with preventive and therapeutic benefits are available such as glass ionomer dental cement (GIC) and resin-modified glass ionomer cement (RMGIC).
The Zinc polycarboxylate dental cement is not used for restorative purposes because the cement is opaque and as a result has poor esthetic property, high solubility, and poor mechanical properties.

Ploycarboxylate Cement | Cements in Dentistry
August 25, 2020
Zinc Phosphate cement: An overview

Zinc phosphate dental cement is one of the oldest dental cement. It is historically used for restorative applications along with the silicate cement. Although new dental materials are now available, this dental cement is still used for restorative applications.

Dispensing form and Composition of Zinc Phosphate cement

The zinc phosphate dental cement is supplied in powder and liquid bottles. The cement is also available in capsules in which the powder and liquid are Pre-portioned. The powder component of the dental cement comprises zinc oxide and magnesium oxide. While the liquid component comprises phosphoric acid and water.

The setting reaction

The setting reaction is an acid-base reaction. The reaction occurs primarily between zinc oxide, which is the main ingredient of the powder and phosphoric acid, which is the main component of the liquid bottle. This setting reaction results in insoluble zinc phosphate, which is the set form of dental cement.

The initial setting time of the cement is around 5 minutes. The setting time depends upon numerous factors such as temperature, humidity, and particle size of the dental cement powder. The smaller particle size of the dental cement results in a faster setting of the dental cement.

Properties

Zinc phosphate cement forms a weak bond with the tooth structure because it does not form a chemical bond with the tooth structure. The bonding of cement is by mechanical means similar to zinc oxide eugenol dental cement. The thermal conductivity of cement is low. Therefore it is used as a cavity base under metallic restoration such as dental amalgam to protect the vitality of the dental pulp. This cement does not have excellent esthetic properties as the cement is opaque because of the unreacted zinc oxide particles. The new materials, such as composite-based and glass ionomer cement, are now used for luting applications because of ease of use and better mechanical and esthetic properties. In contrast to other dental cement such as glass ionomer cement and zinc oxide eugenol cement, the zinc cement does not have any antimicrobial or therapeutic properties.

Clinical Applications

The zinc phosphate cement is used as a cavity liner and base material and has moderate durability. It has traditionally been used as a luting material for crown and bridge cementation. The esthetic properties, as already described, are not excellent, especially when the crown margins are visible. This cement is sometimes used as a temporary filling material.

Adverse Reactions

The systemic adverse effects are infrequent with the use of zinc phosphate cement. Local adverse reactions include cytotoxic reactions within the dental pulp. For example, after cementation of the prosthesis in young patients using this cement, it produces cytotoxic reactions due to initial acidic pH during the setting of cement that may lead to pulp necrosis. The young patients are more likely to experience pulp damage because of the open dentinal tubules compared to older patients in which the dentinal tubules become sclerotic.

Zinc Phosphate Cement | Dental Cement

August 15, 2020
Zinc oxide eugenol cement

The traditional odor of dental surgeries in the past is due to the use of eugenol or oil of cloves and eugenol containing dental materials such as Zinc oxide eugenol cement, zinc oxide eugenol impression paste. The eugenol has a strong odor and has bactericidal and pain releveling properties. In this blog, we will provide detailed insight of this dental cement. This cement is also referred to in the literature as Zoe dental cement. Among numerous dental materials, the Zoe Dental cement is classified as a temporary or intermediate restorative material.

Dispensing and Composition

The zinc oxide eugenol cement is dispensed in two forms one is the Powder and liquid form and the second is in the two paste forms. In this cement the powder contains Zinc oxide which is the main active ingredient, another ingredient in the powder is zinc acetate which acts as an accelerator during a setting reaction. In the liquid eugenol is the main active ingredient. Olive oil is present in smaller quantities to control the viscosity of the liquid.

The two paste system has an advantage over the powder liquid formulations because they are easier to proportion and mix the material especially when the two pastes are available in auto mix dispenser form. The active ingredients of the two paste system are similar to the powder liquid formulations. Water is an important factor in the setting of zinc oxide eugenol. Moisture also accelerates it.

Setting Reaction of Zinc Oxide Eugenol Cement

The setting reaction is between zinc oxide and the eugenol that are the two main ingredients of this dental cement. Initially, during the setting reaction, there is the hydrolysis of a zinc oxide powder to zinc hydroxide. The zinc hydroxide than react with the eugenol to form eugenol gel that solidifies in 6 to 10 minutes. The final setting of the zinc oxide eugenol cement occurs within 12 to 24 hours after the placement of the dental cement. The presence of resin, quartz, calcium phosphate, and zinc acetate accelerate the setting of zinc oxide eugenol cement. The external factors that accelerate the setting of this dental cement are moisture, temperature, and humidity.

Properties

The compressive strength of ZOE cement is lower than zinc phosphate cement. The reinforced or modified ZOE cement have higher compressive strength as compared to unreinforced ZOE cement. The eugenol leaches out from the set zinc oxide eugenol cement and lessens the pain and inflammation within the dental pulp (obtundent effect). The released unreacted eugenol present in the dental cement matrix is also bactericidal. However, the leaching of the eugenol from ZOE cement results in the ingress of water into the material and disintegrates this dental cement. The zinc oxide eugenol cement interferes with the setting and also causes discoloration of resin-based restorative materials. Therefore, the dental cement should not be used when the final restoration is resin-based.

Uses of Zinc Oxide Eugenol Cement

It is used as a cavity base and lining material in deep cavities, for temporary cementation of crown and bridges, temporary filling material, and for periodontal dressing after periodontal surgery.

Modifications

Some modifications of the zinc oxide eugenol cement are developed to improve the strength and to reduce the solubility of this dental cement. It is an example in which the eugenol is replaced by carboxylic acid. Replacement of part of eugenol liquid with orthoethoxybenzoic acid (EBA). Other modifications include reinforced cement in which the alumina is added in the powder and replacement of 20-40% powder with the polymer.

Adverse Reactions

This dental cement if placed in the deep cavities may result in the necrosis of the dental pulp. It should be handled with gloves as the eugenol present in the dental cement may cause angular cheilitis, allergic perioral eczema, and contact stomatitis.

Zinc Oxide Eugenol Cement | Dental Cements

Zinc oxide eugenol cement

August 4, 2020
Dental Material: An Easy Guide
If you are a general or a specialist dental practitioner, dental student, or dental researcher it is of paramount importance that you should know about the materials that you are authorized to use in the clinical, laboratory, and research settings. In this blog, we will discuss briefly dental biomaterials, the classification of dental materials, and the ideal properties of dental material.

The dental material science involves the study of materials composition, physical, chemical, and biological properties and how these dental materials interact with the oral environment in which these materials are placed.

In other words, dental material science covers a broad range of terminologies, microstructure, and properties of these materials that can be used to predict and describe the performance of the dental materials.

Classification of Dental Materials

There are several ways in which dental materials are classified. One of the wide classifications of dental materials is:
1. Preventive dental materials
2. Restorative dental materials
3. Auxiliary dental materials
Preventive dental materials

The preventive dental materials include pit and fissure sealants, restorative materials (compomers, glass ionomer cement), toothpaste, gels, mouthwashes, liners, and bases. Some of these dental materials physically prevent the occurrence or progress of the dental disease by modifying the anatomy of favorable sites for microbial growth such as deep pit and fissures. While other materials release therapeutic or preventive agents such as fluoride or chlorhexidine that prevent and inhibit the progress of the disease.

Restorative dental materials

The restorative dental materials are used to replace or repair the missing dental hard or soft tissues. These materials include dental cement, dental amalgam, resin-based composites, compomers, ceramics, metal ceramics, cast metals, and denture base polymers. A restorative material can be used for a temporary or provisional purpose (Temporary dental cement such as zinc oxide eugenol cement, temporary crown and bridge polymers) and permanent or long term application (dental cement, inlays, onlays, crown, bridges, dentures, and orthodontic appliances).

The dental restorative materials are further classified as direct and indirect restorative materials. The direct restorative materials are manipulated in the dental clinic for their final application and include dental Amalgam and dental cement. The indirect restorative materials are prepared for their final application into a dental laboratory by a dental technologist or a technician. The indirect restorative materials include porcelain fused to metal restorations used for crown and bridge construction, metal alloys, and polymers that are used for the construction of complete and partial dentures.

Auxiliary dental materials

These materials are used for the fabrication of dental prosthesis or dental appliances. Some of these materials are entirely used in the dental laboratory while some of the materials they link the dental clinic and the dental laboratory. The dental auxiliary materials include dental impression materials, dental stone, dental plaster, dental waxes, acrylic resin, and finishing and polishing materials. Some of these auxiliary materials may not become part of the final restoration or prosthesis examples of these are dental impression materials, dental stone, and polishing materials.

The classification of dental materials is not very straight forward as in some cases a preventive dental material can also serve as a restorative dental material, for example, Glass ionomer cement. Similarly, dental polymeric materials have uses both as restorative material and auxiliary material.

Ideal Properties of Dental Materials

The ideal dental material should have the following properties.
1. Biocompatibility: The ideal dental material should be biocompatible it means that the material should perform its desired function without eliciting an immune response.
2. Bonding: The material should form a permanent bond with the adjacent natural tissues such as tissues of tooth, bone, or soft tissues.
3. Esthetics: The dental material should match the natural appearance of the replaced tissue such as tooth or oral soft tissues
4. Chemistry and Structure: Exhibit properties similar to those of the tissues that are being replaced hard tissues of the tooth or oral soft tissues.
5. Repair or Regeneration: The ideal dental material should be capable of initiating tissue repair or regeneration of the missing or damaged tissues.
An ideal dental material that exhibits all these properties do not exist as any of these has the properties closer to the structure of the tooth and the other soft and hard tissues of the oral cavity. The material scientists are trying to develop newer materials that exhibit these ideal or closer to these ideal properties.

Introduction and Classification of Dental Materials
July 31, 2020
Periodontal Ligaments: An Easy Guide for learners
Learners always found these crisscrossing fibers difficult to understand. In this informative blog, we will explain these periodontal ligament fibers in an easy to understand manner, without excluding important details.

Periodontal ligaments (PDL) are one of the important components of the periodontium (the investing and supporting tissues of the human tooth). Besides periodontal ligaments, other components that invest and support the human tooth are cementum, alveolar bone, and part of the gingiva that is facing towards the teeth.

The periodontal ligaments are the dense soft connective tissue. Most of the periodontal ligament fibers are present between cementum and the bone lining the tooth socket. The periodontal ligaments (PDL) are derived from the dental follicular cells. The periodontal ligaments with cementum and alveolar bone form a specialized fibrous joint that is known as gomphosis.

Functions Performed by the Periodontal ligaments

The periodontal ligament fibers perform the following main functions.

The PDL fibers support the tooth in the socket and keep the gingival tissues in their proper relationship with teeth and the alveolar bone.

The Periodontal ligament fibers act as a shock absorber and therefore, they withstand and absorb the impact of masticatory forces.

There are cells in the periodontal ligament space and those cells form bone, cementum, and periodontal ligaments. Besides these cells, there are stem cells that can differentiate into different cell families according to the requirement.

Cells in the Periodontal ligament space

The following cells are present within the PDL space.

Fibroblasts

These are the principal cells of the periodontal ligament. The fibroblasts they achieve remodeling (synthesis and degradation) of the collagen fibers. Increase expression of matrix metalloproteinases by these cells aggressively destroy collagen fibers during periodontal disease.

Epithelial Cells

These cells in the periodontal ligament space are the remnants of Hertwig epithelial root sheath cells (HERS) known as the rest cells of malassez. These cells are present close to cementum in the form of clusters or strands. The epithelial rest cells of malassez have a role in the repair and regeneration of the periodontium.

Undifferentiated cells

These cells are located around the blood vessels (perivascular cells). These cells are the source of new cells for the PDL space as after the deletion of old cells by programmed cell death (apoptosis) there is a requirement of new cells. These undifferentiated cells can differentiate into various cell types present in the PDL space.

Bone and Cementum Cells

Besides these cells, other cells that are present in the periodontal ligament space are bone and cementum cells. The cementum cells are the cementoblasts and the cementoclasts and bone cells that are present are osteoblasts and osteoclasts. Besides these cells, there are also defense cells that are present and those include mast cells, macrophages, and eosinophils.

Periodontal Ligament fiber bundles

The periodontal ligament fiber bundles mainly comprise of type 1 and Type 3 collagen fibers. These collagen fibers are arranged in fiber bundles. Besides these other fibers that are present in small amounts are Elastin, Oxytalan, and Elaunin fibers.

The PDL ligament fiber bundles are arranged into two groups.

Principal fiber bundles (originate from cementum and insert into alveolar bone).

Gingival Ligaments (originate either from cementum or alveolar bone and inserts into gingiva).

Principal Fiber Bundles

The principal fiber bundles are arranged into five groups.

Alveolar crest fibers

The alveolar crest fibers originate from the cementum just below the cementoenamel junction (CEJ) and insert at the crest of the alveolar bone socket.

Horizontal fibers

The horizontal group of fibers presents below the alveolar crest group and they originate from the cementum and at a right angle to the long axis of the tooth inserts into the alveolar bone.

Oblique group

The oblique group of fibers originates from the cementum and in an oblique direction inserts into the alveolar bone lining the socket coronally. The oblique group of fibers is more in number as compared to other principal fiber groups.

Apical Group

These fibers are present at the base of the socket. The apical group of PDL fibers originates from the cementum around the apex of the root and inserts into the adjacent alveolar bone.

Interradicular group

These group of fibers they originate from the interradicular cementum present at the furcation areas of the root and inserts into the interradicular septum of the alveolar bone. The interradicular fibers are only present in the multi-rooted teeth.

These all principal fiber groups are embedded in each end into cementum and another end into the alveolar bone. The embedded portion of these PDL fiber bundles is referred to as Sharpey’s fibers. These Sharpey’s fibers in the acellular cementum are fully mineralized while in the cellular cementum and the alveolar bone these fiber bundles are only mineralized at their periphery.

Figure 1 The orientation and names of the Principal fibers (follow the color and numbers) of the PDL.

Alveolar crest fibers

Horizontal fibers

Oblique group

Apical Group

Interradicular group

Transseptal group (part of Gingival fiber group)

Gingival ligaments

The gingival ligaments are arranged into five groups.

Dentogingival group

The dentogingival group of fibers they originate from the cervical cementum (near cementoenamel junction) and inserts into the connective tissue of the free gingiva. Among the gingival group of fibers, these are the most frequent fiber bundles.

Alveologingival group

These fibers originate from the crest of the alveolar bone and inserts into lamina propria of the free gingiva.

Circular group

This fiber group forms a band around the neck of the tooth. Together with the gingival group of fibers, these fibers bind the gingiva to the neck of the tooth.

Dentoperiosteal Group

These group of fibers they originate from the cementum slightly below the dentogingival fibers and inserts into the outer cortical plate of the alveolar bone.

Transseptal Fibers

These fibers originate from cementum just below the cementoenamel junction (CEJ) passes over the alveolar crest and inserts into the cementum of an adjacent tooth. These fibers are also known as interdental ligaments as they connect all the teeth in the dental arch.

The turnover time (formation of new fibers and replacement of old fibers) of transseptal fibers is low as compared to other fiber groups. Therefore, the prolonged retention period is required after orthodontic treatment. Post retention relapse is associated with these fibers.

Figure 2 The orientation and names of the Gingival fibers of the PDL (follow the color and numbers). Transseptal group of fibers is in figure 1

Dentogingival group

Alveologingival group

Circular group

Dentoperiosteal Group

Blood Supply of the Periodontal ligaments

The PDL has a rich blood supply and is supplied by the superior and inferior alveolar arteries. The branches of these arteries enter the periodontal ligament space as perforating arteries. The blood supply is more in the PDL space of the posterior teeth as compared to the anterior teeth.

Nerve Supply of the Periodontal ligaments

Nerve fibers enter into the PDL space from the apical region towards the gingival margin. Few nerve fibers enter form the later walls of the tooth socket. Most of the nerve ending in the PDL space are the free nerve endings.
Periodontal Ligaments
July 12, 2020