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Year : 2017  |  Volume : 14  |  Issue : 1  |  Page : 7-11

Hazards of prosthodontic devices and materials

Department of Prosthodontics, Faculty of Dentistry, Tanta University, Tanta, Egypt

Date of Web Publication14-Mar-2017

Correspondence Address:
Safa'a A Asal
Department of Prosthodontics, Faculty of Dentistry, Tanta University, El-Geish Street, Tanta 31527, El-Gharbia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/tdj.tdj_51_16

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The intent of this review is to highlight the hazards and risks associated with prosthodontic practice and briefly discusses their diagnosis in routine practice with the intention to enhance awareness, and take preventive measures to reduce the risks among professionals.

Keywords: biological hazards, chemical hazards, ergonomic hazards, physical hazards prosthodontics, psychological hazards

How to cite this article:
Asal SA, Abdel Fattah FE. Hazards of prosthodontic devices and materials. Tanta Dent J 2017;14:7-11

How to cite this URL:
Asal SA, Abdel Fattah FE. Hazards of prosthodontic devices and materials. Tanta Dent J [serial online] 2017 [cited 2023 Jan 31];14:7-11. Available from: http://www.tmj.eg.net/text.asp?2017/14/1/7/202055

  Introduction Top

A hazard can be defined as a source of potential damage, harm, or adverse health effects on something or someone at work.

Hazards are generally labeled as one of five types. Physical hazards: are conditions or situations that can cause the body physical harm or intense stress. Chemical hazards: are substances that can cause harm or damage to the body, property, or the environment. Biological hazards: are biological agents that can cause harm to the human body. Psychological hazards: are conditions created during work related stress, or a stressful environment. Ergonomic hazards: are commonly referred to physical occupational conditions that may pose risk of injury to various parts of the musculoskeletal system.

Prosthodontics may be defined as 'the branch of dentistry pertaining to the restoration and maintenance of oral function, comfort, appearance and health of the patient by the restoration of natural teeth and/or the replacement of missing teeth and craniofacial tissues with artificial substitutes'. In other words prosthodontics includes a variety of branches including complete dentures, removable partial dentures (RPDs), or implant assisted prostheses.

There are a lot of debates about the safety of the compositions of widely used materials such as impression materials, resin-based synthetic polymers, cements, alloys, and dental ceramics.

Currently, there are no substantial scientific data, nor robust evidence warning against the continued use of any of these materials. Oral release of compounds from prosthodontic biomaterials remains a major concern with the likelihood of adverse reactions that could result from their intraoral use. There have been also increased concerns regarding the safe clinical application of these materials as their biodegradation in the oral environment may lead to harmful effects. Many signs of the noted reactions were asymptomatic and may even remain unnoticed for a long period of time. A questionnaire survey among prosthodontists indicated adverse patient reactions in one out of 300 patients, or one patient in ˜2 years per prosthodontists [1].

Prosthodontic hazards may affect the patient, the dentist, the dental laboratory technician, or the dental assistant.

Prosthodontic hazards are labeled as:

  • Hazards affecting patients, which may be either:
  • Hazards because of the material composition and manipulation (chemical hazards)
  • Hazards caused by of the dentist (iatrogenic hazards)
  • Hazards affecting dental personnel (occupational hazards).
  • Hazards affecting patients

Chemical hazards

A wide variety of materials such as resin-based synthetic polymers, metals, cements, impression materials, and dental ceramics are used for construction of dental prosthesis. Polymerization of resin-based materials may be initiated by heat, light, or by chemical activators, which initiates the reaction at room or mouth temperature. These resin-based materials contain accelerators such as amines, copolymers, such as butylmethacrylate, plasticizing agents such as dibutylphthalate, and inhibitors such as hydroquinone. In addition, cadmium salts-based coloring agents may also be used. It should be kept in mind that prosthodontic materials are manufactured with the aim of being inert and insoluble. Thus, the amounts of leachable components should be very small, which makes the development of toxic reactions unlikely to occur. Meanwhile, some of the metals used in dental alloys are known to be biologically active or potentially hazardous, such as nickel, cobalt–chromium, cadmium and beryllium. Unexpected adverse reactions to prosthodontic materials may occur as a result of their direct contact with soft tissues [2]. A wide variety of materials have been used in dental implants. Numerous investigations have been performed to assess the biological properties of dental implants. Pure titanium implants do have an inert nature towards the tissues.

Literature has reported some of the adverse reactions associated with prosthodontic treatment such as:

  • Burning mouth syndrome' which is one of the annoying patient complaints which are characterized by diffused or localized burning sensation in the mouth. In fact the burning sensation may result from direct mucosal irritation, intraoral manipulation of resin or because of the presence of residual monomer [3],[4]
  • Contact allergic reactions (type IV reactions) are another adverse reaction associated with prosthodontic treatment [5],[6],[7]. It appears in the form of redness and swelling of the affected mucosa that could be perplexed with the signs of mechanical irritation caused by overextended, poorly-fitting dentures, or poor oral hygiene [8],[9]. It may either be caused by formaldehyde, which is a degradation product of several monomers used in dentistry, residual monomer especially in chemical cured prosthetic appliances [1] or to an ethylene amine activator used in several polymeric materials, including impression materials and temporary crown materials [10]. Hildebrand et al. [11] have concluded that mucosal reactions to metal-based partial dentures are rare, while remote reactions occurred in almost 25% of patients.

Literature has pointed out that allergic reactions to gold-based restorations were more common than to nickel-containing alloys [12]. This finding is in agreement with the findings of a survey of mucosal reactions to more than 1000 prosthetic units [13].

One of the common reasons of allergic reactions may be attributed to the use of the denture cleansers containing persulfate [14]. Symptoms of these allergic reactions are more severe. It takes the form of tissue irritation, tissue damage, rash, hives, gum tenderness, breathing difficulties, and low blood pressure. Other possible reactions as a result of the misuse of denture cleansers include damage to the esophagus, abdominal pain, tissue burn, breathing difficulties, seizures, bleaching of the oral tissues, internal bleeding, and vomiting [14].

Recurrent facial dermatitis was observed with dental work using of epoxy acrylate bisphenol-A glycidildimethacrylate [15].

Root fractures after post and core restorations was documented with different metal combinations and was attributed to the galvanic corrosion. Therefore, it is important not to combine two different alloys for the cast post and core/crown restorations when preparing post retained crowns [16].

Diagnosis of allergy

Whenever, there is an adverse reaction to any prosthetic material or treatment, a number of information should be gathered. Among these are: detailed history of the adverse reaction, its nature, detailed examination of the prosthesis, any medication used by the patient, as well as the salivary flow rate. Thorough investigations should be carried out to achieve an accurate diagnosis of allergy. Oral mucosal tests based on adverse reactions to materials in contact with the hamster-cheek pouch is considered to be a short-term test for prosthodontic materials and is relatively less invasive or traumatic than suturing the material in contact with the mucosa. If a holding device is used, uncertainty exists regarding the position and amount of pressure exerted by the test specimen. Specially designed appliances for testing prosthodontic materials have not received widespread use, probably because of the inherent problems associated with the test or the cost involved [17]. Development of tests for prosthodontic materials should therefore receive greater attention. While skin patch test is of limited value because a distinct difference exists between material reactions intraorally and extraorally, in addition to the irrigating effect of saliva which is difficult to assess [18],[19].

Management of allergy: when diagnosis of the lesion is confirmed to be allergy to residual monomer, researchers recommend reduction of the amount of residual monomer in the dentures by soaking them in water before insertion, and instructing the patient not to wear the newly made dentures overnight, so as to avoid mucosal irritation caused by leachable residual monomer molecules. Nowadays, change to denture base materials which are monomer-free such as light activated resin (Eclipse) [20].

Iatrogenic hazards

Proper handling and maintenance of the health and integrity of the oral tissues is the responsibility of the dentist. A careful and meticulous diagnosis, treatment planning and treatment procedures should be carried out properly. It has been shown that fixed and RPDs that were constructed using the principles generally followed did not harm the oral structures [21]. However, the dentist may be implicated in accidentally producing an oral problem as a result of inadvisable/careless dental therapy which may cause patients to suffer physically, mentally, as well as financially. Such damage caused by the dentist is called an iatrogenic damage/hazard [22].

Some of the documented iatrogenic adverse effects of prosthodontics include:

  • Local mechanical irritation; epulis fissuratum is a reactive lesion arising from excessive and chronic mechanical pressure on the vestibular oral mucosa. It may be due to an overextended denture borders, poor denture fit, or faulty occlusion
  • RPDs may increase the incidence of caries, damage the periodontium, and increase the amount of stress on natural teeth [23]. This may be explained by the fact that the insertion of RPD creates potential for quantitative and qualitative changes of plaque formation on the remaining teeth and thereby increases the risk for development of gingivitis and periodontitis [24]
  • Regarding fixed partial dentures, the use of high-speed cutting instruments, or the utilization of retraction cords during impression making procedure can cause serious and irreversible damage to the attachment complex if performed without regard to fragility of the tissues and the small margin for error that exists [25]
  • Overcontoured crowns and restorations tend to accumulate plaque and possibly prevent the self-cleansing mechanism of the adjacent cheeks, lips, and tongue. The degree and extent of marginal inflammation depends on failure to maintain the proper emergence profile, inability to adequately finish the subgingival crown margins, placement of margins in an area with no attached gingiva, and violation of the biologic width [26]
  • Materials left in inaccessible areas like subgingival regions where remainence of elastomeric impression materials were left behind, thus affecting cell viability. Therefore, due care should be taken to carefully check the subgingival areas before disposing the patient from the clinic
  • There was absolute negligence about force distribution on abutments. The number of teeth replaced far exceeds the potential supportive ability of the abutment teeth as dictated by Ante's law. This will result in destruction of the periodontal structures and premature failure of the fixed partial denture prosthesis
  • Implant materials; much attention was focused on the bone tissue/implant interface and on the ingrowth of bone into the porous implant fixture. According to Branemark, implant failure commonly result from improper surgical procedures, problems related to the loading of the implant, and infection [27].

Hazards affecting dental personnel

Occupational hazard is defined as a risk to a person in his working environment.

According to WHO, the term 'hazard' refers to an inherent property of an agent, or situation having the potential to cause adverse effects when an organism, system, or population is exposed to that agent [28].

Dental work set up poses many risks to its employees. New Zealand studies found over 40% of dental professionals were affected with different occupational hazards, and women dentists experienced double the chances of allergy occurrence [29].

Biological hazards

Bacterial contamination from splatter and aerosol dissemination generated by high-speed instrumentation pose a significant risk for dental personnel [30]. Apart from contamination by microorganism, the composition of aerosol produced during the use of rotary instruments is of concern.

Contaminated impressions (soiled with blood saliva and other infectious material) are another source of infection in prosthodontic practice. When plaster/stone is poured into a contaminated impression, microorganisms from its surface spread into the cast, and this infected cast is ordinary handled in the dental laboratory. The plaster dust from the infected casts gets into the respiratory tract of the laboratory personnel, settles on clothes and environmental surfaces, and remains viable for a considerable time [31]. Other possible sources of infectious contamination are the dental unit waterlines (DUWL), handpieces, saliva ejectors and suctions as well as other devices attached to air and waterlines [32].

Chemical hazards

A variety of materials which are commonly used in dentistry alloys, polymer materials, acrylic resins, ceramics, cements, sealers, etchants, hypochlorite, waxes, and elastomeric impression materials are generally used in clinical prosthodontic practice as well as in the laboratory [33]. Ingredients of these materials do not pose any problem for the patients but may have deleterious effects on the dental laboratory technicians during laboratory procedures such as packing, grinding, and finishing the prostheses. A study reported that 53 of 70 dental technicians were affected by pneumoconiosis, which could be caused by dust from the processing of dental materials [34].

Irreversible hydrocolloid powder contains about 60% diatomaceous earth, which could be inhaled and may prove to be a health risk (carcinogenic) over a long time span [35]. Woody et al. [36] monitored and characterized aerosol particles from two alginates and showed that 10–15% of the particles pose the greatest risk. With daily utilization of irreversible hydrocolloid materials in the dental office, improper handling of these materials could be hazardous to the health of dental personnel.

Even though the ceramic materials are generally inert, inhalation of its dust containing free silica in dental laboratories can lead to silicosis [37].

Regarding the elastomeric impression materials, it is documented that the polyether materials were found to be more toxic than polyvinyl siloxanes [38].

Physical hazards

Physical hazards that are commonly encountered in prosthodontic practice include direct physical trauma, heat and fire injuries to the face, the scalp and particularly the eye. Overall, 4.5% of prosthodontists have percutaneous injuries occurred/year [39]. The grinding tools are generally of high frequency and they can cause direct injury to the face and upper extremities. The effects of vibration on the hand can also result in vibration syndrome [40] or vibration white finger [41],[42].

Prosthodontists and dental laboratory technicians are exposed to noise of different sound levels that are potentially damaging to hearing which include low speed handpieces, high-speed turbine handpieces, ultrasonic instruments, high velocity suction, and cleaners, vibrators and other mixing devices, and model trimmers [43]. These equipments emit sounds, which are very close to the limit of hearing loss [43]. Eye irritations may happen from a variety of laboratory materials. Painful reactions are elicited when methyl methacrylate monomer, or when pumice which contains lime and quartz are accidentally splashed into the eye; in addition pumice can also cause eye abrasion [44].

Ergonomic hazards

Ergonomic hazard is a physical factor within the environment that harms the musculoskeletal system. Prosthodontists are at high risk of neck and back problems due to the limited work area and impaired vision associated with the oral cavity. The symptoms include low back pain, stiffness, and sciatica with neurological features such as tingling, paresthesia, and muscle weakness [45].

Psychosocial hazards

Occupational stress such as coping with patient demands (75%), practice management/staff issues (56%), fear of complaints/litigation (54%) and nonclinical paperwork (54%). These physical and emotional demands may result in physical and mental burnout [46].

  Conclusion Top

  • The use of masks, aspirators, and mechanical removal of as much resin as possible before using rotary instruments may reduce the biological exposures
  • Decontamination of DUWL includes the state of art method of using ozone
  • Incorporation of ozone generating units into the dental treatment unit would be the logical extension of this technology
  • The integration of the use of ozone into a dental unit involves a system of disinfection and sterilization for DUWL into the clinical management and patient arena [47].


Measures to combat stress by relaxation, exercise, meditation, hobbies are also recommended.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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