Cavo surface margin in various restorations / dental implant courses by Indian dental academy

CAVO SURFACE MARGIN IN VARIOUS RESTORATIONS Preparing a tooth to receive a restorative material is a comprehensive endeavor. As routine or mundane as it may seem, many factors affect the appropriate tooth preparation design for a given tooth. These factors must be considered for each restorative procedure contemplated, the end result being that no two preparations are the same.

The cavo surface angle is the angle of tooth structure formed by the junction of a prepared (cut) wall and the external surface of the tooth. The actual junction is referred to as cavosurface margin.

This seminar highlights on Cavosurface designs of various restorations like amalgam , composite, direct filling gold , glass ionomer restoration, ceramic restoration and cast restorations.

It also highlights on types and design features of occlusal and gingival bevels, types and design features of facial and lingual flares, bevels and flares in inlay restoration (primary flare and secondary flare- Its functions and indications ),bevels and flares in onlay restoration, tooth preparation for cast restoration with surface extensions and circumferential tie constituents for extracoronal preparations.

Proper tooth preparation is accomplished through systematic procedures based on definite physical and mechanical principles. Moreover, the physical properties and capabilities of the different restorative materials must be appreciated. All of these are determining factors in understanding proper tooth preparation.

Without this background knowledge, plus additional information concerning the mechanics of cutting and patient management, the exercise of proper judgment for efficient and proper tooth preparation cannot be achieved .If the principles of tooth preparation are followed, the success of any restoration is greatly achieved

CARIOLOGY- ETIOLOGY, CLASSIFICATION, HISTOPATHOLOGY AND CLINICAL FEATURES

TEETH ARE TOOLS that have evolved to ensure survival of species. Caries is a biosocial disease rooted in the technology and economy of our society. Dental caries is unique not only in terms of pathological mechanism; other aspects, social and economic, are also worthy of note. The uniqueness of dental caries makes it a fascinating study from a scientific standpoint.

Dental caries is defined as an infectious, microbial disease affecting the hard parts of the tooth exposed to the oral cavity, resulting in decalcification of inorganic constituents and dissolution of organic components.

This seminar highlights on classification, etiology-early theories and current concepts, clinical features, the concept of caries as a specific microbial infection, properties of cariogenic plaque, concept of critical pH, stephan curve, the role of saliva, nutrition, trace elements and demographic factors on dental caries.

It also explains morphological and chemical events of dental caries, histopathology of enamel and dentinal caries, electron microscopic studies of carious enamel and mechanism of enamel caries and cementum caries at chemical level.

Caries, because of its uniqueness as a disease, its ubiquitous nature, and its stubborn resistance to resolution remains as one of man’s most common oldest and singly costliest ailment. The total health handicap due to dental caries is staggering. In western countries there has been a dramatic decline in caries over the past decade. But in the economically developing countries caries prevalence is increasing as dietary habits of industrialized nations are adapted. For this reason, it is important that the subject of dental caries is given as broad a readership as possible. Recognition of the enormity of the problem should spur effects to reduce the ravages, the pain and the cost of this disease.

PATHOPHYSIOLOGY OF PAIN Word pain is derived from a Greek word “Poine” which mean penalty or punishment Pain is a protective mechanism that occurs when tissues are being damaged. It causes the individual to remove the painful stimulus. It is probably the most fundamental and primitive sensation, distributed more or less all over the body.

According to International Association for the Study of Pain (IASP) pain is defined as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”.

The different components of pain are sensory, emotional, autonomic and motor.

Pain can be felt as superficial or deep pain, referred pain, projected pain, intractable pain and psychogenic pain. There are two theories of referred pain –convergence projection theory and convergence facilitation theory. Pain on a broad scale is divided into Fast pain or acute pain, slow pain or chronic pain and Transient pain.

Pain receptors are free, afferent nerve endings of myelinated A-δ and unmyelinated Cfibres that encode the occurrence, intensity duration and location of noxious stimuli and signal pain sensation. Pain receptors are of three types- mechano sensitive, thermo sensitive, chemo sensitive.

Hyperalgesia is a decrease in pain threshold in an area of inflammation, such that even trivial stimuli cause pain.

Allodynia – Pain from stimuli that are normally not painful This seminar highlights on peripheral and central mechanisms contributing to allodynia & hyperalgesia and various theories explaining mechanism of pain transmission (Specificity theory, Pattern (Central summation) theory, Sensory interaction theory and Gate control theory).

Differential Diagnosis of dental pain PULPAL PAIN Hyperactive pulpalgia, Dentinal hypersensitivity, Hyperemia, Acute pulpagia-Incipient, Moderate, Advanced, Chronic pulpalgia and Barodontalgia.

PERIRADICULAR PAIN Acute apical periodontitis, Acute apical abscess, Periodontal lesion pain, Gingival abscess, Periodontal abscess and Pericoronitis.

The diagnosis and management of pain are foundation skills in clinical dentistry.

Although the subject of pain is of considerable significance to all health providers, the simple reality is that many patients consider pain and dentistry to be synonymous. This association is even stronger between dental pulp and pain – to many patients it comes as no surprise that the dental pulp is innervated by pain receptors. So the knowledge about the pain mechanisms of the pulpo – dentin complex helps the clinician to make more accurate diagnosis and to design more effective pain control plans for their patients.

MANAGEMENT OF PERFORATION Root canal treatment, like other procedures of dentistry is sometimes associated with unwanted or unforeseen circumstances; these are collectively termed procedural accidents. One such procedural accident is perforation.

Perforation is considered as one of the main causes of endodontic failures. Perforation occurs accidentally during the mechanical aspect of endodontic treatment or during subsequent preparation for a post or results from mis orientation or searching for a canal.

The main complication that arises from perforation is the potential for secondary inflammatory periodontal involvement and loss of attachment, eventually causing tooth loss.

Definition An endodontic perforation may be defined as “An artificial opening in a tooth or its root, created by boring, piercing, cutting or pathologic resorption, which results in a communication between the pulp canal and the periodontal tissues�.

Perforations can be classified into coronal, midroot and apical level and can be identified by direct observation, paper points , radiographs, apex locator. Perforations can be repaired by three modalities: non-surgical, micro surgical and combined approach.

The four dimensions of perforation are size, level, location and time. The materials used to repair are grouped into: hemostatics, barrier materials (resorbable and non-resorbable) and restoratives.

Non-surgical The internal matrix concept in conjunction with the microscope is an efficient and effective technique for treating accessible perforation of 1mm or greater in diameter nonsurgically.This technique involves the placement of biocompatible material into the

perforation site to control hemostasis and prevent overfills acting as an internal matrix similar for a class II cavity preparation.

Indications for surgery Large perforations, Nonsurgical inaccessibility, Resorption defects, Failure of healing after nonsurgical repair, Large overfills of the defect intracoronally.

Intracoronal/surgical approach A combined approach involves repairing the defect intracoronally, then reflecting a surgical flap to remove the inevitable over extension of the repair material from the periodontal space.

In the case of failing furcation repairs; bicuspidisation, hemisection, intentional replantation, or root amputation may be considered depending on the level of crestal bone, crown-to-root ratio, and degree of root divergence.

All perforations adversely affect prognosis, some doom the tooth to extraction.

So knowledge of the etiologic factors involved in procedural accidents is essential for their prevention. In addition, methods of Recognition and treatment as well the effects of such accidents on prognosis must be learned.

Most problems can be avoided by adhering to the basic principles of diagnosis, treatment planning, access preparation, cleaning and shaping, obturation and post space preparation.

CLEANING & SHAPING OF ROOT CANAL SYSTEM WITH HAND INSTRUMENTS Cleaning and shaping are the basics of endodontic therapy. Most obturation problems are really problems of cleaning and shaping. Even simple canals that are poorly shaped are difficult to obturate properly, whereas extremely complex root canal systems can be obturated properly if the shaping has been accomplished skillfully. Over the years, there has been a gradual change in the ideal configuration of a prepared root canal. At onetime, the suggested shape was round and tapered, almost parallel. After Schilder’s classic description of “cleaning and shaping,” the more accepted shape for the finished canal has become a gradually increasing taper, with the smallest diameter at the apical constricture, terminating larger at the coronal orifice Cleaning; refers to the removal of all contents of the root canal system before and during shaping: organic substrates, microflora, bacterial byproducts, food, caries, denticles, pulp stones, dense collagen, previous root canal filling material, and dentinal filings resulting from root canal preparation.

Shaping; During this process, instrumentation must give the system a form that will ensure tissue removal and a shape that will enhance total filling of the root canal system in three dimensions. Inadequate shaping causes inadequate obturation.

Shaping enlarges the canal’s diameter and smoothes the walls as it removes crevices, fissures, and irregularities from the system. Cleaning is a combined chemical and mechanical process, while shaping is purely a mechanical one.

This seminar highlights on pulpectomy, various irrigants used for cleaning and their importance, precurving, anticurvature filing, different motions (filing, reaming, watch-winding, turn and pull) and methods of cleaning and shaping with hand instruments (step-back, modified step-back, step-down, modified crown-down, doubleflared, crown-down pressureless, canal master technique ) with emphasis on balanced force concept.

NON SURGICAL ENDODONTIC RETREATMENT

Despite new materials, innovative techniques and a plethora of novel devices, the continuing growth and trend towards more complex forms of endodontics has been accompanied by an increasing need to manage endodontic failures. Such failures pose many, varied challenges which, if successfully overcome, can be both professionally rewarding and a real practice builder.

Rationale for retreatment •

Endodontic failures can be attributable to inadequacies in cleaning, shaping, and Obturation, iatrogenic events, (or) reinfection of the root canal system when the coronal seal is lost after completion of root canal treatment.

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The rationale for nonsurgical retreatment is to remove the root canal space as a source of irritation to the attachment apparatus.

Non-Surgical Versus Surgical Retreatment "When failure has occurred after root canal treatment, surgical retreatment should not be chosen as the first treatment option until the possibility of non-surgical retreatment has been ruled out.

This seminar highlights on different modalities of Coronal disassembly, identification of missed canals, removal of various obturation materials, techniques of post removal, broken instrument removal, methods to overcome blocks, ledges and apical transportations and managing endodontic perforations.

Surgical retreatment encompasses a number of procedures, referred to synonymously as: · periapical curettage/periradicular curettage · apicectomy/root end resection/apical resection · root-end filling/retrograde filling · surgical repair · root resection/root amputation · hemisection/bicuspidization.

With a continuing improvement in oral health and a change in patient attitude, it is no longer acceptable to extract teeth simply because of periapical disease and endodontic failure. Advances in scientific knowledge and technical skills have helped improve the prognosis of treatment, but it may not always lead to the desired healing response in clinical practice.

If initial treatment is unsuccessful, practitioners are increasingly expected to possess the necessary knowledge and skills to perform ever more technically demanding procedures to save teeth. The focus on evidence-based treatment has resulted in secondary care providers, such as local oral surgery units, no longer being willing unquestioningly to accept failing endodontic cases for surgery, prior to an attempt having been made to retreat by non-surgical means

IMPRESSION MATERIALS AND TECHNIQUE FOR INDIRECT RESTORATION

Dental impression is a negative record of the tissues of mouth. Impression materials are used to record the surface topography and detail of hard and soft tissues, and thereby produce a mold for making a replica (cast) of those structures.

Hydrocolloids and synthetic elastomers are among the materials most commonly used to make impressions of the various areas of the dental arch.

The accuracy of fit and functional efficiency of the restoration depends on how well the cast replicates the natural oral tissue, hence it is of great importance that inaccuracies are minimized at this stage otherwise, they will be carried through and possibly compounded later on.

The indirect technique for fabricating cast restorations is the most common technique now in use. This is due to the vast improvement in impression materials in the past thirty years. So the clinician must be aware of new materials available in the market and ensure appropriate technique for obtaining accurate casts.