These changes originate either by a direct action of a working environment on oral cavity mucous membranes, or they are a manifestation of general chronic intoxication. A variety of pathological states belong to this group, some of which allow patients to be financially compensated for them, since these diseases are classified as work-related according to present regulations.
1. Damages caused by a dusty environment.
Upon the exposure to soft flour or sugar powder, a heavy plaque is formed at teeth necks, circular caries occurs and marginal inflammations of the gingiva arise. Coal, stone or siliceous powders mixed with saliva of mine or quarry workers, form a kind of an abrasive paste that cause abrasion of teeth occlusal planes and edges. Metal powder originating during machining causes catarrhal and sometimes ulcerous inflammations of gums. Calcitic or cement dust acts both as a mechanical abrasive and chemically: the cheek mucosa coloration, even leukoplakias appear after a long exposure. The chemical or metallurgic industry workers are affected by changes of the hard dental tissues (the tooth enamel gets rough) or by cheek mucosa hyperkeratinosis.
2. Damages caused by general intoxication.
Changes that are a result of a general intoxication with heavy metal salts can also be found inside the oral cavity. Discoloration of the gingiva around teeth necks, caused by lead intoxication, is particularly known to occur at workers in lead foundries and lead paints manufacturing. Intoxication by mercury that is the most commonly used material for fillings in stomatology, appears not only at mercury plants workers but also at people working in dentistry. Mercury penetrates wall plasters and floor chinks at a dentist’s office. Mercury intoxication causes vague problems (trembling of arms and legs, headaches, irritability) that are difficult to explain for a long time. Ulcerous mucosa inflammations are often found after intoxication with zinc or chromium. Arsenic which is a part of devitalization preparations may cause local ulcerous changes of the gingiva if not applied properly; or osteitis if it penetrates through the apical foramen of the tooth root (single-root teeth, too long application of arsenic preparation in a carious cavity). Heavy metals intoxications are usually accompanied by an excessive salivation and taste ailments.
4.4 Manifestations of AIDS on the Oral Cavity Mucosa
Infection by the human immunodeficiency virus (HIV) is associated with several pathological changes of the oral cavity mucosa. An early recognition of these changes represents a significant addition for the general diagnosis of this worldwide disease (AIDS - Acquired Immune Deficiency Syndrome). The group of intra-oral pathological changes, associated with the HIV infection, contains the following diseases:
candidous infections (erythematous, pseudo-membranous or hyperplastic candidiasis)
hairy leukoplakia of the tongue
gingivitis and HIV necrotizing gingivitis
Kaposi sarcoma with a predominant appearance at the palate and gums
Non-Hodgkin lymphoma (at the palate and gingiva)
Besides the above stated clinical picture, a diagnosis of these diseases is also based on immuno-serologic examinations.
5. Prosthetic Dentistry
Prosthetic dentistry deals with replacements of lost teeth or their parts, parts of alveolar ridges and soft tissues of the oral cavity or the face.
Artificial dental replacements are called stomatologic prostheses (dentures). Their significance is both medical and social. The medical importance lays in therapy and prevention. The social importance means a possibility for a patient with affected dentition to re-enter his/her career and a social life.
Dentures should meet requirements of functionality, phonation, esthetic look and health. Dentures can be divided into crown prostheses, teeth prostheses, and fixed or removable ones. Depending on a way of the chewing pressure transmission, prostheses may be divided into dental, dento-mucosal, and mucous.
The teeth to which a prosthesis is fixed, are called abutments. According to their biological factor, these teeth can be divided into three classes. The biological factor of teeth depends on teeth shape, cariousness, periodontal diseases, teeth developmental anomalies and alveolar ridges atrophy.
Teeth losses result in defects of dentition that are classified to three classes according to Voldřich:
I. class A gap, up to four adjacent teeth wide, bounded by the first class pillar teeth.
II. class A shortened dental arch. It is replaced by a dento-mucosal denture. The first class teeth is replaced by dental prostheses.
III. class Defects that do not belong to the above two classes. These are usually replaced with dento-mucosal or mucous prostheses.
Dentures are made according to a model that can be obtained by the direct method, i.e. by modeling a pre-made prosthesis directly inside a mouth, or by the indirect method that includes forming pre-made structure on a situation model. Metal dentures or their parts are made by casting into a mold by the “vanished wax” technique. Resin dentures are formed according to a wax model of a prosthesis inside a flask filled with plaster. After the wax model is melted and drained, a cavity inside the plaster is stuffed with resin paste that polymerizes inside the flask under pressure.
5.1 Types of Dentures: Fixed Dental Prostheses
Fixed dentures transmit chewing pressure by the dental way only. Teeth fitted with those dentures (pillar teeth) are prepared properly, and constructions that attach to these teeth are called pillar constructions. This group contains inlays, crowns, fixed bridges.
Inlays replace a part of a tooth’s lost crown or the whole crown. An onlay replaces the whole occlusal part of a crown. An inlay replaces the occlusal part of a crown either totally or partially, plus one or both proximal parts of it.
Root inlay (superstructure) replaces the whole crown part of a tooth and it is attached to a treated root canal by the root pin.
Crowns replace a part or the whole damaged tooth’s clinical crown that is covered, partially or completely, by a surface jacket which reaches to, or under the marginal gingiva. Crowns are of the following types:
1. Jacket crowns, made of metal, ceramic or resin.
Metal jacket crowns are made by casting from gold, gold-palladium or silver-palladium alloys. A temporary protective band crown can be made for young patients in exceptional cases. These crowns are made of a metal sheet with cast or sheet occlusal surface (for distal teeth), or as a protective metal sheet crown made of two halves for frontal teeth.
Ceramic crowns are the oldest type of jacket crowns that still fit today’s needs well. They are used mostly at the frontal section. The base of ceramic is silicon dioxide, feldspar and kaolin that is being replaced by aluminum oxide these days. Ceramic crowns are much harder than dental tissues or prosthetic metal alloys. For this reason, a pillar tooth periodontium may get damaged by its overloading (a ceramic crown does not abrade), or a non-physiological abrasion of an antagonist tooth may occur.
Resin crowns are the most often used ones for frontal teeth. The material from which these crowns are made is a methylmetacrylate resin. A disadvantage of these crowns is their low mechanical resistance and bad color stability.
2. Veneer crowns are made of metal by casting, in combination with a resin or ceramic that form a veneer. The metal construction covers by its inner casing a treated tooth’s surface. The outer jacket completes the anatomical shape of a tooth from oral and proximal sides, whereas the facet (a part of the outer jacket) completes the crown’s shape from the visible vestibular side.
3. Pin crowns replace the whole clinical crown of a pillar tooth. They are fixed to its root by the root pin.
Fixed bridges replace gaps after one to four teeth of the dental arch that are framed by the first class abutments. If a connecting line between the abutments is straight, the bridges are referred to as linear ones. If connecting lines of the abutments enclose a plane, bridges are marked as planar (anchored to a plane). If the pillar teeth number is higher than number of replaced teeth, we call them splinting bridges. A fixed bridge consists of abutment retainers and the pontic, or so called inserts. The pontic fills the area after missing teeth and it is firmly connected abutment retainers. According to the relationship of a pontic to an alveolar ridge, there are inserts that are not in contact with the mucosa (reverse arch cleansable pontic), and contact inserts. Reverse arch cleansable pontics are used at the lower jaw’s distal parts for high abutments. The mucous surface of an insert has to be at least 3 mm clear of the alveolar ridge mucosa. Contact pontics sit at the alveolar ridge by a small oval surface that has a major part located at the vestibular slope of the alveolar ridge. The occlusal surfaces of pontics are reduced in size by about one third, so that to prevent an overload of abutments during chewing.