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PURPOSE: A more precise and up-to-date definition of prosthetic dentistry is warranted. The aim of the present review is to present a new core definition of the discipline on the basis of a discussion of existing definitions. MATERIALS AND METHODS: Clinical textbooks in prosthetic dentistry and dental implantology, as well as medical and dental glossaries were reviewed. RESULTS: Two main categories of definitions of prosthetic dentistry were identified: first, definitions that emphasized the technologic aspects of the discipline, i.e., the fabrication of prostheses; and second, definitions that incorporated some reference to the objectives or aims of prosthetic treatment, i.e., the restoration of one or more aspects of oral function. Slightly more than half of the citations contained such aim-related references, and this aspect tended to be most pronounced in recent publications. CONCLUSION: The following definition is ventured: prosthodontics is the discipline of dentistry concerned with the consequences of congenital absence or acquired loss of oral tissues and with the methods for and assessment whether more good than harm is done by inserting artificial devices made from alloplastic materials.

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Research has shown that lifestyle intervention has a promising effect in patients with coronary heart disease, but little is known about the practice of such intervention. To explore this issue a questionnaire was sent to all departments of internal medicine in Norway (N = 67). 58 hospitals responded. The results showed that most hospitals offered physical training (49 hospitals) and dietary intervention programmes (51 hospitals) to patients with coronary heart disease, but only six hospitals offered a smoking cessation programme. The hospitals expressed a desire to expand the existing programmes (especially dietary intervention) and establish new ones (in particular smoking cessation), but claimed that lack of personnel and funds limited their activity. Only a few hospitals record in the medical journal that a patient has been informed about the significance of changes in lifestyle.

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An in vitro test method is described simulating the in vivo fate of a denture adhesive, i.e., destruction of the adhesive, dilution, and dissolution, by measuring the bond strength for the adhesive placed between acrylic resin plates. Between each measurement, the adhesive was exposed to isotonic saline. The bond strength for two ointment denture adhesives, Super Corega and Fixodent, was measured and the results were compared with those obtained for one of them in a previous in vivo test. The test method described for denture adhesives seems useful to depict the fate of a denture adhesive in clinical use.

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Case histories of patients referred to a university clinic for evaluation/treatment with implants were studied, regarding recommended and actually performed treatment. Patient reactions after treatment with conventional methods were also recorded. Three main groups attended: 1) Elderly, unsatisfied complete denture wearers. 2) Patients with few remaining teeth and an aversion against removable dentures. 3) Young patients with single teeth missing in an otherwise healthy dentition. Fifty-seven per cent of edentulous patients were recommended correction/replacement of their conventional full denture. Three out of four followed the recommendation. For jaws with a severely reduced dentition conventional prosthetic alternatives were advocated in 80 per cent of the cases. Corresponding treatment was carried out in 57 per cent of the cases, prosthetic appliances differing substantially from the suggested alternative in 26 per cent, and 17 per cent received no prosthetic treatment. Only few jaws required single tooth replacements. Every second patient who had this complete denture corrected or remade, considered implant therapy then superfluous. All complicated cases with extensive tooth loss were treated to the patients satisfaction, without using implant support, provided the treatment was referred to a colleague with specialist training. Forty per cent of similar cases remitted to their general practitioner did not receive any prosthetic treatment at all.

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The microbiological properties of four tissue conditioners, one soft liner, and one acrylic resin were studied. The tissue conditioners showed no or negligible antimicrobial effects toward salivary microorganisms by two different in vitro tests. In in vitro adhesion experiments, more Streptococcus mutans and Candida albicans adhered to the tissue conditioners and the soft liner in comparison with conventional acrylic resin used for denture-base fabrication. No difference in bacterial adhesion was found among the tissue conditioners. The microbial colonization of two tissue conditioners lined on maxillary dentures in three volunteers was followed for 14 days. No difference among the materials was found, but a tendency for subject-dependence in plaque formation on the materials was noted.

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The characteristics of the masseter reflex evoked by tapping a maxillary incisor were compared with the reflex pattern evoked by tapping a corresponding denture tooth after insertion of an immediate denture. Up to three inhibitory phases (I-1, I-2 and I-3), followed by excitation, were found on an averaged EMG. The tapping force threshold for the early inhibitory phase was lower than for the late phases. The pattern of the reflex was generally the same before and after insertion of the denture, but the threshold values increased. After insertion of the denture, the threshold for I-1 increased from 1 +/- 0.3N to 2.2 +/- 0.4N, the threshold for I-2 increased from 2.4 +/- 0.8N to 3.8 +/- 0.9N, and the threshold for I-3 increased from 5.1 +/- 0.6N to 8.3 +/- 0.9N. The latency period for I-1 also increased from 12.3 +/- 0.5 ms to 13.1 +/- 0.3 ms after insertion of the denture. After relining, the threshold for evoking I-1 decreased from 2.7 +/- 1.2N to 1.2 +/- 0.6N. It was assumed that the mechanoreceptors situated in the mucosa under the denture base could take over the functional role of the periodontal mechanoreceptors for evoking the masseter reflex during tapping, and that these afferents probably had connections to the same interneurones.

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Parotid salivary flow rates in response to chewing or citric acid stimulation were studied in two patients who had their last maxillary teeth extracted and immediately replaced with complete dentures. The patients were monitored 6 months from the last week before extraction. Parotid salivary flow rate in response to chewing was increased after insertion of the denture. For one of the patients a particularly high output from the parotid gland was found 2 weeks after treatment. Throughout the experiment, parotid salivary flow was higher on the chewing side than on the contralateral side. At the end of the experimental period the dentures were relined. Salivary flow measured immediately after relining was lower than prior to this procedure. An increased salivary response was also observed during citric acid stimulation after transition from the dentate to the denture wearing state. This increase was more marked if the patients had their dentures in situ when the gustatory provocations were performed. It is concluded that parotid salivation increases during masticatory and gustatory stimulation in patients subjected to total extraction and immediate complete denture treatment, and that the presence of a complete denture per se appears to act as an additional mechanical stimulus in the salivary reflexes.

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This presentation discusses a new approach to preprosthetic orthodontic treatment of adult patients with missing anterior teeth. The basic idea is: Prosthodontic appliances with high and lasting esthetic qualities are difficult to obtain in the anterior region. Our alternative is to close anterior gaps by orthodontic treatment, if necessary combined with recontouring of individual crowns by means of grinding and/or light-cure resin buildup. Spaces needing prosthetic closure are transferred to more posterior regions of the dental arch, usually in the premolar region. Different aspects of this new approach has been presented and discussed. The material is derived from a clinical study currently in progress at the departments of orthodontics and prosthetics at The Dental Faculty in Oslo.

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Twenty patients with complete dentures in both jaws gave up their maxillary ones for experimental purposes for 4 weeks while new dentures were made. The experimental dentures were reduced palatally to a new U-shaped border situated approximately 10 mm from the dental arch. Denture retention, defined as the ability of a denture to remain seated on the supporting tissues under various conditions, was measured as resistance towards cranially directed tilting loads, using a miniature bite force recorder. Dislodgement-provoking loads were applied to the first bicuspid on both sides and to the central incisors. The retention measurements were performed before and immediately after reduction of the palatal coverage and, finally, after 4 weeks. Interview questions were posed concerning the subjects' experience of denture retention and some other aspects of oral comfort. The interviews were carried out before reduction of the palatal coverage and after 2 and 4 weeks. The results of the experimental dislodgement tests suggested that the ability to withstand tilting loads was insignificantly altered by reduction of the palatal coverage. This finding was in agreement with responses indicating that retention during meals remained unchanged. However, several individuals reported that denture retention between meals was impaired. Three denture wearers reported that reduction of the palatal coverage influenced their sense of taste positively, and one reported that an occasional gagging tendency had disappeared. At the end of the experiment the participants were given the choice of a new conventional denture or a new denture without palatal coverage.(ABSTRACT TRUNCATED AT 250 WORDS)

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The influence of complete maxillary denture design on retention was studied under clinical conditions simulating chewing. Five persons with an edentulous maxilla and a natural dentition of at least 10 teeth in the mandible participated. Retention was measured with a miniature bite force sensor. The occlusal load required to provoke denture dislodgement was recorded. The general principles of denture design were as follows: the bicuspids and molars were set on top of the residual ridge; the thickness of the denture borders was determined functionally; and the palate was covered to the vibration line, without attempts at border compressions. The details that were changed to evaluate their influence on denture retention were as follows: the point of attack of the dislodgement-provoking load alternated between three distinct pits, situated 2 mm apart in the buccopalatal direction on the occlusal surface of the first right bicuspid; the vestibular denture border on the left side was reduced stepwise to 75%, 50%, and 25% of its original thickness; and the distal extension of the palatal denture border was shortened stepwise (2 + 2 mm, as measured in the midline). Measurements pertaining to one specific problem were carried out within a period of 2 h. The results confirmed the concepts that lingualized occlusal contact, functionally determined filling in of the vestibular sulcus, and full palatal coverage to the vibration line all have a positive influence on the retention of complete maxillary dentures.

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The influence of free tongue, lip, and cheek function on the retention of complete maxillary dentures was investigated for five experienced denture wearers. Test dentures were designed with full palatal coverage and functionally determined filling in of the vestibular sulcus. The front teeth were arranged primarily to meet cosmetic demands--that is, anterior to the top of the residual alveolar ridge. Retention was measured as resistance to dislodgement-provoking loads applied vertically to the incisive edge of the central incisors, using a miniature bite force recorder. All the participants were able to load their front teeth with 35 N or more without loss of retention. None of them experienced denture dislodgement provided the tongue, lips, and cheeks wee allowed to act freely. If the peripheral soft tissues were separated from the vestibular denture flange, no obvious effect on denture retention could be detected. Physically preventing the tongue from pressing against the posterior part of the denture reduced the retention significantly. Measurements of anterior loads tolerated after stepwise reductions of the denture extension indicated that the tongue acted primarily by pressure against the tuber regions. Tongue pressure against the central parts of the palate and lip or cheek pressure against the vestibular flange seemed to be of less importance.

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Complete maxillary dentures were tested for their ability to remain in place when subjected to unilateral occlusal loads. The test material comprised five persons, each supplied with three identical dentures. The denture design was based on the principles of 1) functionally determined filling-in of the vestibular sulcus, 2) palatal coverage to the vibration line without post dam, 3) aesthetically governed positioning of the front teeth, and 4) positioning of the lateral teeth in the plane connecting the top of the residual ridge with the central part of the occlusal surface of the antagonizing natural teeth. Resistance to unilateral occlusal loads was measured by means of a miniature bite force sensor. In the pooled material, an average load of 70 N was tolerated before the dentures were dislodged. For a given participant/denture combination, the resistance against dislodgment varied considerably when tested on different days. Marked differences were also found among three identical dentures in one person. The tolerance against unilateral occlusal loads could feasibly be quantified. However, the influence of specific clinical and/or technological factors on denture retention during function should be studied only if strict definitions as to the test conditions are given. These conditions must include the time, person, and denture tested.

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Streptococcus mutans from saliva of one test person were isolated on mitis/salivarius agar containing bacitracin and extra sucrose, and subcultured in vitro on trypticase soy broth with numerous transfers. Freshly isolated organisms and bacteria from selected subcultures were studied in adhesion tests using glass or dental zinc phosphate cement as substrate. Different bacterial isolates were used in separate experiments. Three different techniques were used; two based on radioactivity assays of adhering 3H-thymidine-labelled bacteria, and one based on visual counting. With all three techniques freshly isolated S. mutans adhered in significant numbers. It was consistently found that their ability to adhere decreased with the number of in vitro transfers. The results support the view that growth condition is an important factor governing the adhesive properties of oral bacteria.

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Freshly isolated strains of Streptococcus mutans from saliva of two test subjects were tested for adhesion to various dental gold alloys and one brand of luting cement. The materials were covered with pellicle derived from one or the other of the two subjects. In "crossover" experiments it was consistently found that S. mutans adhered in greater numbers to pellicles of homologous origin. This preference for the homologous pellicle appeared to vary among the materials tested as substrates; also, the total number of organisms adhering varied among the materials. Moreover, different isolates varied in their affinity for the materials and showed a varying degree of dependence on homologous pellicle for adherence. In vitro plaque formation of mixed oral flora on pellicle-coated dental casting gold alloy were also more abundant on homologous pellicles as compared with heterologous ones. The results support the view that biologically specific mechanisms contribute to the adhesion of bacteria to dental restorative materials, and to the build-up of a bacterial plaque on these materials.

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Test specimens of zinc phosphate, polycarboxylate, zinc oxide-EBA, silico-phosphate and resin cements were carried in the mouth for 2 hours. The bacteria adhering to the cement specimens were quantified after culture on selective and non-selective, solid media. Significantly fewer bacteria could be recovered from the EBA cement than from the other cement types. All cement specimens, as well as samples from tooth surfaces, showed selective enrichment of Actinomyces viscosus compared with the proportion of this organism in saliva. The silicophosphate and particularly the polycarboxylate cement were poor substrates for the adhesion of Streptococcus mutans. Scanning electron micrographs revealed heavy accumulations of coccoid and filamentous organisms on zinc phosphate cement surfaces. Fewer bacteria, mainly cocci, were seen on the polycarboxylate and silico-phosphate cements, whereas the micrographs of the EBA and resin cement surfaces were difficult to interpret.

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A sensitive, in vitro method has been developed for the study of bacterial adsorption to dental crown and bridge cements. The method employs heavily radiolabelled cells which adhere to the wall in wells made from the cements. Loss of radioactivity from the bacterial suspension during incubation is used to measure the degree of bacterial adherence to the materials. Strains of Streptococcus sanguis and Streptococcus mutans adhered in greater numbers than a strain of Streptococcus salivarius to both a zinc phosphate cement and a zinc carboxylate cement. The zinc phosphate cement supported adherence to a greater degree than did the zinc carboxylate cement. Pretreatment of the cement surfaces with human saliva tended to reduce bacterial adherence. Pretreatment of the bacteria with saliva slightly enhanced sorption of S. sanguis and S. salivarius, but tended to impair sorption of S. mutans to both types of cements. When both bacteria and cements had been pretreated with saliva, a strong inhibition of the adherence of S. mutans was observed.

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In vitro cytotoxicity of freshly prepared temporary crown and bridge materials was studied using mouse fibroblasts prelabelled with 3H-thymidine grown in shake flask cultures. Cytotoxicity was measured as (1) lack of cell multiplication, (2) stainability with Trypan blue and (3) release of 3H-labelled material to the culture medium. All the materials tested (zinc oxide-eugenol cement (ZOE), Scutan and Sevriton) were cytotoxic in this system, ZOE most strongly. This finding favours the view that the in vitro cytotoxicity of dental materials should not be used alone as a screening test for their biological compatibility under clinical conditions since clinical experience and previous in vivo findings have established that ZOE is biologically well tolerated by the dental tissues.

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The ability of a common dental plaque bacterium, Streptococcus sanguis, to adhere to dental crown and bridge cements in vitro was investigated. Cylindrical blocks of five different commercial brands of cement, with and without acquired pellicles, were indubated with buffer suspensions of S. sanguis for 1 h. Attached bacteria were counted under the microscope. S. sanguis had particularly high affinity for uncoated resin cement. In contrast, the carboxylate cement tested was a poor substrate for the adherence of this bacterium. The other cement types (zinc phosphate, zinc oxide and silico-phosphate) had intermediary qualities as adhering surfaces. The presence of an acquired pellicle, obtained by pretreatment with saliva, influenced the initial adherence of bacteria to cement in vitro. On the resin cement a salivary pellicle strongly suppressed the bacterial adhesion. For the zinc phosphate, zinc oxide and silico-phosphate cements a pellicle slightly enhanced the attachment of S. sanguis. On the carboxylate cement only few organisms attached also after pretreatment with saliva.

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