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To evaluate presumptive differences in osseointegration at implants installed in healed sites or extraction sockets, supporting either crowns or bridges that were functionally loaded or left unloaded. In six dogs, the mesial roots of the first mandibular molars were treated endodontically. Bilaterally, the teeth were hemisected, and the distal roots extracted. First and second mandibular premolars were extracted as well. After 3 months, the mandibular third and fourth distal roots were extracted after endodontic treatment of the mesial roots. Four implants were installed bilaterally, two in the healed sites corresponding to the second premolar and first molar regions, and two into the extraction sockets. Cobalt-chrome single crowns were prepared and installed in the two most anterior implants, and bridges at the two most posterior implants, bilaterally. A 3-unit bridge was applied to the premolars in the upper jaw only at the loaded sites. All prostheses had a flat occlusal surface and contacts in centric occlusion only at the loaded sites. Three months later, biopsies were retrieved for histological analysis. Higher levels of osseointegration and bone density were observed at the unloaded sites, both at implants installed in healed and post-extraction sites. However, only at implants installed in the post-extraction sites and supporting single crowns, the difference in bone-to-Implant contact was statistically significant. In implant installation immediately following extraction or delayed after three months, osseointegration and bone density were not affected by occlusal contact schemes.

Frameworks made of carbon fibre-reinforced composites (CFRC) seem to be a viable alternative to traditional metal frameworks in implant prosthodontics. CFRC provide stiffness, rigidity and optimal biocompatibility. The aim of the present prospective study was to compare carbon fibre frameworks versus metal frameworks used to rigidly splint implants in full-arch immediate loading rehabilitations. Forty-two patients (test group) were rehabilitated with full-arch immediate loading rehabilitations of the upper jaw (total: 170 implants) following the Columbus Bridge Protocol with four to six implants with distal tilted implants. All patients were treated with resin screw-retained full-arch prostheses endowed with carbon fibre frameworks. The mean follow-up was 22 months (range: 18-24). Differences in the absolute change of bone resorption over time between the two implant sides (mesial and distal) were assessed performing a Mann-Whitney U-test. The outcomes were statistically compared with those of patients rehabilitated following the same protocol but using metal frameworks (control group: 34 patients with 163 implants - data reported in Tealdo, Menini, Bevilacqua, Pera, Pesce, Signori, Pera, Int J Prosthodont, 27, 2014, 207). Ten implants failed in the control group (6·1%); none failed in the test group (P = 0·002). A statistically significant difference in the absolute change of bone resorption around the implants was found between the two groups (P = 0·004), with greater mean peri-implant bone resorption in the control group (1 mm) compared to the test group (0·8 mm). Carbon fibre frameworks may be considered as a viable alternative to the metal ones and showed less marginal bone loss around implants and a greater implant survival rate during the observation period.

Implant-supported fixed partial denture with cantilever extension can transfer the excessive load to the bone around implants and stress/strain concentration potentially leading to bone resorption. This study investigated the effects of implant configurations supporting three-unit fixed partial denture (FPD) on the stress and strain distribution in the peri-implant bone by combining clinically measured time-dependent loading data and finite element (FE) analysis. A 3-dimensional mandibular model was constructed based on computed tomography (CT) images. Four different configurations of implants supporting 3-unit FPDs, namely three implant-supported FPD, conventional three-unit bridge FPD, distal cantilever FPD and mesial cantilever FPD, were modelled. The FPDs were virtually inserted to the molar area in the mandibular FE models. The FPDs were loaded according to time-dependent in vivo-measured 3-dimensional loading data during chewing. The von Mises stress (VMS) and equivalent strain (EQS) in peri-implant bone regions were evaluated as mechanical stimuli. During the chewing cycles, the regions near implant necks and bottom apexes experienced high VMS and EQS than the middle regions in all implant-supported FPD configurations. Higher VMS and EQS values were also observed at the implant neck region adjacent to the cantilever extension in the cantilevered configurations. The patient-specific dynamic loading data and CT-based reconstruction of full 3D mandibular allowed us to model the biomechanical responses more realistically. The results provided data for clinical assessment of implant configuration to improve longevity and reliability of the implant-supported FPD restoration.

The aim of this study was to investigate the usage of tooth autotransplantation in dental clinics which offer the treatment and evaluate its practicality. Participating dentists were requested to provide information on transplantations they had undertaken from 1 January 1990 to 31 December 2010. A total of 614 teeth from 552 patients (37 dentists) ranging in age from 17 to 79 (mean age: 44·1) were examined. Cumulative survival rate and mean survival time were calculated using the Kaplan-Meier method, and log rank test was used for analysis of factors. The mean number of autotransplantation patients per clinic per year was 1·4. Upper third molars constituted 36·8% of donor teeth, while 37·1% were lower third molars. The lower first molar region was the most common recipient site at 32·6%, followed by the lower second molar region (28·0%). Prosthodontic treatment of transplanted teeth involved coverage with a single crown (72·5%) and abutment of bridge (18·9%). A total of 102 transplanted teeth were lost owing to complications such as attachment loss (54·9%) and root resorption (25·7%). The cumulative survival rate in cases where donor teeth had complete root formation was 90·1% at 5 years, 70·5% at 10 years and 55·6% at 15 years. The mean survival time was 165·6 months. Older age was a significant risk factor (P < 0·05) for survival. In cases where suitable donor teeth are available, autotransplantation of teeth may be a plausible treatment option for dealing with missing teeth in dental clinics.

The aim of this study was to examine the confidence, barriers and attitudes towards the replacement of missing teeth by general dental practitioners (GDPs). The perceived impact of the recently introduced National Health Service (NHS) contract on the provision of prosthodontic treatments was also considered. Pre-piloted postal questionnaires were mailed to 500 GDPs in Wales. Open- and closed-ended questions were utilised to establish confidence, adequacy of training and attitudes towards treatments for replacing missing teeth. Two hundred and seventeen completed questionnaires were received (response rate = 43.4%). Many respondents described themselves as 'confident' or 'very confident' in the provision of removable partial dentures (RPDs) (acrylic = 100%, metal based = 99.5%), cantilever resin-bonded bridges (94.4%) and conventional bridgework (98.6%). GDPs were 'not confident' providing fixed-fixed resin-bonded bridges (21.1%) or implants (81.4%). Financial barriers were identified to the provision of prosthodontic treatments, including comments such as "the new [National Health Service] contract does limit the treatments available". Privately funded patients were more likely to be offered a fixed bridge or implant replacement of a missing upper first molar, whereas non-privately funded patients were more likely to be offered no treatment (P < 0.01). Most respondents reported confidence at providing more routine forms of prosthodontic care such as RPDs and bridges. It appears that funding arrangements may have an impact on treatments offered to replace missing teeth, particularly under the current NHS contract.

Lower rigidly connected long span bridges supported by natural abutments or implants sometimes become loose, come off, or fracture after a period of usage. Many reasons have been discussed for these failures. However, few researchers have shown the influence of mandibular elastic deformation on the abutments, although this influence is likely to produce a distortion force between the abutment and prosthesis. Therefore, this study measured the elastic deformation of the human mandibular arch during clenching on pivots by using charge-coupled device (CCD) cameras and an image analysing system. When the subjects clenched on the canines (unilaterally or bilaterally) or bilateral second molars, no mandibular deformation was found; whereas when the subjects clenched on the unilateral second molars, the mandibular arch on the non-pivot side moved upward and inward and the straight line distances between the right and left measurement points decreased by 0.2 mm. The magnitude of deformation is smaller than the depressible limit of periodontal membrane. This suggests that the influence of mandibular deformation on the connected prosthesis is negligible in the case of the natural root supported long span bridge but should probably be considered in the case of the implant supported bridge.

Even if implant therapy is very common nowadays, treatment with conventional fixed bridge prosthesis still has indications and cannot be forgotten. Because of improved dental health more teeth can be preserved and more fixed prostheses are prepared also for the elderly. The aim of this study was to discuss the future of treatment need in fixed metal ceramic bridge prostheses based on the analysis of distribution of pontics in dentition in four different age groups during the years 1984-1996. Data were collected from the patient files. The numbers of upper lateral incisors, upper first premolars and lower first molars were analysed in years 1984-1987, 1988-1992 and 1993-1996 between and within age groups of under 34, 35-49, 50-64 years and over 65 years. As a conclusion, in the future the treatment need for fixed bridge prostheses will be highest among patients over 50 years and their most replaced teeth are, besides lower first molars, the upper first premolars.

Rochette described the perforated cast metal bonded design for splinting periodontally compromised teeth. The design was later used for replacing missing teeth. The main causes of failure of the perforated (Rochette) type design were attributed to inappropriate case selection and erosion of the composite from perforations. The aim of this study was to analyse the effect of stress magnitude and direction on failure of perforated resin bonded bridges (RBBs). The objective was to compare stress magnitudes in this design with those reported on the non-perforated RBBs. Photoelastic modelling materials were selected to represent the relative stiffnesses of a posterior mandibular and an anterior maxillary perforated (Rochette) type design. The sizes of the models were scaled to x 2.5 in order to enhance visual analysis of the stress patterns. Stress magnitudes were quantified from isochromatic fringes and stress directions were evaluated from stress trajectories. These revealed a high-stress concentration around the perforations, particularly for those at the proximo-lingual/palatal (connector) areas. This experimental study revealed that the main reason for failure of Rochette designs is deformation at the perforations.

Masticatory function is an important aspect of oral health, and oral rehabilitation should aim to maintain or restore adequate function. The present qualitative review is the joint effort of a group of clinicians and researchers with experiences ranging from basic and clinical oral neuroscience to management of patients with dental implants. The aim is to provide a short summary for the clinician of the many aspects related to masticatory function (including quality of life) and rehabilitation with dental implants. While there are many reviews on the tissue responses to dental implants and technical aspects, the functional aspects have received relatively little focus.

In 1984 an oral health survey of Hong Kong adults aged 35-44 years revealed that 15% of subjects presented with metal shell crown restorations, often as components of fixed-bridge reconstructions. The aim of this study was to describe the patterns and means of use of shell crowns, and to describe the patterns of tooth loss in patients who presented with such restorations, attending for treatment at the dental teaching hospital in Hong Kong over a 2-year period. A total of 1563 such patients attended. The records, which included radiographs, of 165 of these patients aged 35 years and above, obtained by means of a systematic sampling frame, were studied by one trained examiner. On initial presentation each patient was found to have a mean of 4.0 shell crowns, 77% of these being components of bridge restorations. The bridges involved a mean of only 3.9 units (retainers and pontics). The tooth type most commonly replaced by a bridge of this type was the first molar. It was concluded that most shell crowns used in this patient group are abutment retainers for predominantly short-span bridge restorations.

summary Aspiration of teeth and dental restorations is a recognized, yet an infrequent happening in the literature. Main reasons of aspiration are maxillofacial trauma, dental treatment procedures or ethanol intoxication and dementia. The present case of a 2-unit bridge aspiration is however, not related with any trauma, dental procedure or systemic disease. A 37-year-old male patient had aspirated his bridge while sleeping and the bridge remained unidentified for 1 year despite the radiographic controls. He was then referred to the Chest Diseases Department of School of Medicine, Ege University and the radio-opaque object in the right intermediate bronchus was diagnosed to be an aspirated dental prosthesis. Subsequent to the failure of the rigid bronchoscopy, the patient was referred to the Thoracic Surgery Department and had to be operated for retrieval of the foreign body.

Porcelain fused to metal provides better aesthetics in fixed partial dentures than veneers with gold-resin that were used formerly. The aim of our study was to evaluate complications and primary failures of fixed metal ceramic bridge prostheses made by dental students. We studied 61 patients (32 women, 29 men, mean age 49 years, range 28-73 years) treated during years 1990-1993. Data were collected from the patient files. Altogether 82 bridges were made (mean 4.1 units, range 2-6), 221 abutments (mean 2.7, range 2-6) and 136 pontics (mean 1.6, range 1-4). Forty-seven cast cores were used in 29 bridges (mean 0.4 cores, range 1-3) and semiprecious attachments as an extra attachment in two bridges. Seven teeth were extracted due to complication and/or failure during endodontic treatment and root canal perforation during preparation. In two cases the abutment tooth was fractured by removing the old crown. Four unsuccessful bridges were remade and in seven cases the firing of porcelain was renewed. The study concludes that most common failures of fixed metal ceramic bridges made by dental students occur during root canal preparation of abutment teeth.

summary The relationship between bridge failure and the periodontal ligament area of their abutments was studied in 156 dental bridges constructed for 132 patients. Of the bridges constructed at the College of Dentistry, King Saud University, 26.9% did not meet the published criteria of Ante's Law while 50.0% of those made in general dental practice did not meet the same criteria. However, radiographic evaluation of abutment teeth in 56 failed bridges revealed that there were only two cases with evidence of overloading the abutments.

In order to determine the feasibility of constructing fixed partial dentures using glass-ceramic materials, the flexural strength and marginal fit of three experimental glass ceramic materials, and DICOR as control, were studied. The flexural strength ranged from 105.8 MPa to 129.5 MPa. Ceramic and alumina addition provided significant strength as tested by ANOVA and multiple range tests (P < 0.05). The range for the cemented bridge margins was from 48.9 microns to 80.4 microns. The tested ceramics had no statistically significant differences in margin openings for the same sites (P < 0.05). However, the openings on the mesial side of the premolar abutment and the distal end of the molar abutment of the fixed partial denture did have statistically significant differences (P < 0.01). Appropriate addition of alumina led to an increase in bending strength. The alumina stabilizes and strengthens the glass-ceramic material by incorporation into the silicone network.

In this investigation 156 dental bridges, constructed for 132 individuals, were evaluated. The bridges inserted at the College of Dentistry, King Saud University (KSU), Saudi Arabia, were compared with those placed in general dental practice. The results revealed that the rate of bridge failure averaged 35.5%. This was made up from failure of bridges inserted at KSU at (15.4%) and those in general dental practice (46.2%). The major reasons for failure revealed by this study were periodontal disease (36.6%) and secondary caries (23.2%). The average lifespan for the bridges was 6.1 years with 4.5 years for the unfailed bridges. The most commonly used material for bridges was metal-ceramics. The most commonly used pontic design was the modified ridge lap (50.8%), but the saddle type accounted for the greatest percentage of failures (59.6%).

summary The purpose of this study was to assess longitudinally the success of partial and full crown abutment pairs in the same bridges. Fifty patients with a mean age of 45 years (range 22–70 years) were examined during spring 1981 (1–5 year follow-up), 33 of whom were examined a second time during spring 1990 (10–15 year follow-up). The status of the partial crowns, full crowns, and their abutment teeth was assessed using standardized questions, and clinical and radiographic examinations. At the first follow-up examination, all partial and full crowns, and consequently all bridges, were still in use. Before the second follow-up examination one of the full crown abutments had become badly decayed, and the bridge, including the partial crown, had been removed. The failure rate was 0.2% per year for the full crown as a unit, and consequently 0.2% per year for the bridge as a unit.

SUMMARY In order to evaluate the possibility of using endosseal implants (ITI Dental Implant System®) and implant-retained prostheses for 65-year-old patients from a medium-sized Finnish city, 431 such patients were examined by means of panoramic radiographs. The population represents 61% of the total age group in the city (born in 1923). The possibility to construct a prosthesis, anchored on implants, was evaluated in three different groups. It was shown that in group I (edentulous maxilla and mandible, 256 patients) all male and 97% of female subjects could have been treated with implant-retained over- dentures in the lower jaw. Corresponding figures in the upper jaw were 62% for males and 59% for females. In patients with edentulous maxilla and dentulous or partially edentulous mandible (group II, 84 subjects) implant-retained overdenture in the maxilla could have been possible in 52% of male and 43% of female participants. In subjects with own teeth left in both jaws (group III, 91 participants) some kind of implant-retained bridge or single implants could have been constructed in 70% in maxilla and in 92% in mandible.

Summary The aim of this study was to collect information about the mean working time needed to accomplish the clinical procedures in applying an adhesive bridge, and to gain an insight into the factors that influence the working time. The study was carried out as part of a clinical trial. One hundred and fifty-one patients needing one adhesive bridge were selected for this study and divided between five operators. Clinical procedures were carried out following a written protocol. The statistical method consisted of an ANOVA after log-transformation of the working times. The total mean working time needed to accomplish the clinical procedures for adhesive bridges was 60·7 min (s.d.±16·5 min). The mean working time increased by 30% where the abutment teeth were restored with class II or class III restorations. No influence was found related to: (1) type of bridge (i.e. macromechanical versus micromechanical), (2) type of luting resin and (3) location of the bridge. A significant effect on the working times was found for: (1) operator, (2) tooth preparation and (3) occlusal adjustments. With increasing experience of the operator the median working time decreased by up to 35%. The data from this study are considered as useful basic information for efficient planning in the dental practice and for a further cost-benefit analysis.

Summary In this long-term clinical study, the condition of extensive fixed bridges was investigated 10 years after cementation. From the records of the Swedish Insurance System (Gothenburg branch) the individuals were randomly selected. All restorative treatment had been performed by private general practitioners. The investigation comprised a total of 238 bridges making 1606 units, 944 abutment and 662 pontics. Seven bridges had been removed and in a further nine cases the bridge had been separated and units removed. Loose retainers were detected at thirty (3%) abutments. In 14.5% of the surfaces a deficiency in marginal adaptation was found. An open margin seemed to be the most serious defect and was often related to caries in contact with the margin of the crown. Caries and fillings in relation to the margin were detected in 8.1% of the surfaces. Porcelain bonded to gold restorations were significantly more often overcontoured in the interproximal space compared with acrylic resin veneer gold bridges. In the investigation the caries status has been also thoroughly reported. Abutment teeth, presumed to be vital, had a prevalence of 10% radiographically visible periapical lesions. Finally, 93.3% of the bridges cemented 10 years prior to the investigation were still in function without any parts being removed.

Patients treated in private practice and patients treated at the Department of Prosthetic Dentistry of the Faculty of Odontology in Gothenburg with fixed bridgework were questioned about their experience of their bridges. The interview was carried out with questionnaires and in some cases by telephone. The results were similar in both groups, and the patients were satisfied with the treatment.

Based on data from patient records from a random sample of Dutch general practices, a study was made of the bridge distribution pattern in different patient groups. Patient variables such as age, sex and insurance type were analysed. More women had a bridge inserted than men. However, there appeared to be no difference in the average quantity of bridges in men or women. The abutment teeth most frequently used were the cuspids in the maxilla and the second premolars and second molars in the mandible. Fourteen percent of the bridges consisted of five or more units, 14% were free-end bridges, 13% did not meet Ante's law and 16% had one or more non-vital abutment teeth.

Summary A four-unit principal model bridge was used. The stresses in the porcelain part of an anchor crown were analysed. When the middle of the span was loaded tensile stresses appeared in the outer surface of the porcelain and compressive ones in the interface. Greater stresses were found when the anchor crown was loaded itself. They were not critical, however, when the gold thickness was > 3 mm.

Summary This report constitutes a long-term study of 100 saddle-bridges applied by the author during the years 1958–1973. The aim of the investigation has been to assess the prognosis for this form of therapy. The probability that a saddle-bridge will still be functioning completely, without repair, after 5 years is 93 %, and after 10 years (as also after 12 years) 83%. Only 12% of the appliances had been removed 12 years after the application. The risk of defects is about the same during the first 5-year period after the application as it is during the second and the third 5-year periods. A comparison between saddle-bridges applied before and after 1965 shows no demonstrable difference as regards the 5-year prognosis in spite of modifications with respect to range of indication and therapy. The causes of the defects have been divided into biological and technical. During the first 5-year period technical defects appear to be in the majority, whereas during the later stages, biological defects predominate. Background factors such as sex, the age of the patient, length of saddle, localization in the jaw do not prove to have any appreciable importance for the prognosis. There is, on the other hand, a significantly better prognosis when the opposing jaw is furnished with the patient's own teeth and/or fixed bridges than with a removable denture. The author points out that from the result of the study, the saddle-bridge has such a good long-term prognosis that its range of application for fixed constructions should be considerably extended.

Ninety-nine people who were fitted with partial dentures in 1959 were invited to take part in an investigation 13 years later. A questionnaire was answered by fifty-eight, which means a frequency of 81% if allowance is made for an explainable loss. Of the sixty-eight partial dentures in these fifty-eight patients, twenty-three were still being used, fourteen patients had had their original partial dentures replaced by new ones and three by a fixed bridge, while seven had been replaced by complete dentures. Twenty-one were no longer used and had not been replaced. Of the fifty-four patients who originally had a complete upper denture and a partial lower denture, thirty were still available. Following an invitation to take part in a clinical review, twenty-seven (90%) co-operated. Most of the patients were in need of treatment (for caries, periodontitis and/or prosthetic treatment). The periodontal injuries were rarely serious. A correlation was found between good oral hygiene and good results of treatment.

A recently described method for studying occlusal forces in prosthetically restored dentitions (Lundgren & Laurell, 1984) was applied in a standardized programme to elucidate the occlusal force pattern and the functional capability of a dentition during chewing and biting. The method is based on the use of strain gauge transducers mounted into preformed matrices evenly distributed over the tooth-arch. The programme was tested in a subject prosthetically restored with a fixed bridge of cross-arch design in the upper jaw, and with unsplinted teeth in the lower jaw. It involved chewing of (a) peanuts, (b) roast beef with potato salad, biting with maximal strength in habitual occlusion and biting over one limited contact area at a time. The magnitude of the occlusal forces developed during chewing and swallowing was well below all biting forces. The magnitude of the total force acting over the entire dentition when biting at maximal strength in habitual occlusion did not seem to be limited by reactions from the teeth or the periodontal tissues but, seemingly, by the capability of the jaw-closing muscles themselves. The magnitude of the local bite force over one limited contact area at a time was much smaller than that which the jaw-closing muscles were able to develop. This indicated that feedback mechanisms in the periodontal tissues and/or the temporo-mandibular joints were limiting factors for these forces. The programme will be applied to studies of dentitions supplied with prosthetic constructions of various design and with different distribution of periodontal support.

This report constitutes a long-term study of 100 saddle-bridges applied by the author during the years 1958-1973. The aim of the investigation has been to assess the prognosis for this form of therapy. The probability that a saddle-bridge will still be functioning completely, without repair, after 5 years is 93%, and after 10 years (as also after 12 years) 83%. Only 12% of the appliances had been removed 12 years after the application. The risk of defects is about the same during the first 5-year period after the application as it is during the second and the third 5-year periods. A comparison between saddle-bridges applied before and after 1965 shows no demonstrable difference as regards the 5-year prognosis in spite of modifications with respect to range of indication and therapy. The causes of the defects have been divided into biological and technical. During the first 5-year period technical defects appear to be in the majority, whereas during the later stages, biological defects predominate. Background factors such as sex, the age of the patient, length of saddle, localization in the jaw do not prove to have any appreciable importance for the prognosis. There is, on the other hand, a significantly better prognosis when the opposing jaw is furnished with the patient's own teeth and/or fixed bridges than with a removable denture. The author points out that from the result of the study, the saddle-bridge has such a good long-term prognosis that its range of application for fixed constructions should be considerably extended.

A two-dimensional finite element model of a mandibular quadrant was used to examine differences in magnitude of the principal stresses from the placement of three- and four-unit bridges. The area of interest spanned the first premolar to the second molar. Loading conditions were (i) vertical and distributed and (ii) 30 degrees to the vertical and concentrated. The principal stresses were calculated and compared for: (i) the first molar removed with the remaining bone either cancellous or cancellous surrounded by a cortical shell; (ii) as in (i) but with the second premolar and first molar removed; (iii) a three-unit bridge spanning the second premolar to the second molar; and (iv) a four-unit bridge spanning the first premolar to the second molar. Each tooth was supported by periodontal ligaments, cortical and cancellous bone with each assigned the appropriate physical constants. Removal of the first molar resulted in considerable variation of the stresses especially when the cortical shell was replaced by cancellous bone. Because of the lower modulus of cancellous bone and its lower load-bearing capabilities the stresses were three to ten times lower and more uniform within the cancellous bone. Generally, the addition of a bridge resulted in lower and better distributed sigma min stresses. The bridge also resulted in higher tensile stresses distal to the abutment teeth which theoretically could result in bone deposition. No significant differences in magnitude were observed between the three- and four-unit bridge. From a stress standpoint the bridges resulted in more uniform stress distribution around the abutments and an increase in the tensile stress distal to the abutments. Such findings support the placement of a fixed bridge to maintain bone in an edentulous area.

Summary The extent and directions of movements of spring bridge abutments were studied on acrylic casts with resilient steep and shallow palates and containing human molar and premolar abutments with compressible ‘periodontal ligaments’. Bridges with rigid bars and ‘flexible’ standard, long and short lengths were cast in Type IV gold, and soldered to Type III gold retainers which were pinned to the abutments. The pontic on each bar was depressed a standard 0.2 mm, and the movement of the abutments registered on a dial gauge resting against the mesio-buccal corner of each retainer. The combination of bar length and palatal contour causing least movement of an abutment was the shortest bar to the molar abutment in the shallow palate model; indeed all bars on this model deflected the molar abutment less than similar bars on the steep palate model. Differences in palatal contours did not affect the extent of movements of the premolar abutments which were comparable to molar movements in the steep palate model. Abutment teeth moved mesio-buccally when the pontic was depressed, and the elbow of the bar usually moved off the palate indicating the fulcrum was positioned along the anterior section of the bar.

The pattern of axially (perpendicular to the occlusal plane) directed occlusal forces developed during light tooth tapping in habitual occlusion, chewing, swallowing and maximal biting was studied in twelve subjects whose dentitions were periodontally treated and prosthetically restored with cross-arch bridges with unilateral posterior two-unit cantilevers. The measuring devices consisted of four strain-gauge transducers uniformly and bilaterally mounted in pontics of maxillary bridges to represent the posterior (end abutment and distal cantilever respectively) and anterior regions. Thus, the forces could be studied locally in various parts of the dentition simultaneously as well as totally over the entire dentition. The results demonstrated that the distal cantilever unit, on average, was subjected to forces about or less than half of those over the contralateral end abutment unit irrespective of the activity studied. Furthermore, the cantilever forces either equalled or were even significantly smaller than those of the anterior regions. All subjects preferred the end abutment side as the chewing side. When the cantilever side was used as the chewing side, which occurred most infrequently, the bolus was usually located in the anterior region. The mean total chewing force (about 50 N) was only about half of that found in a previous study of subjects supplied with cross-arch bridges with bilateral end abutments (Lundgren & Laurell, 1985). Furthermore, on average only 26% of the voluntary muscular capacity was used during chewing, compared with 37% in the 'bilateral end abutment group' referred to. The reasons for the comparably small forces over the distal cantilever unit and the lower muscular utilization during chewing in cross-bridges with unilateral posterior two-unit cantilevers as well as the implications of the findings for the dimension of such bridge constructions are discussed.

Summary The general and specific satisfaction of patients treated with a jawbone-anchored bridge was compared with their pretreatment satisfaction with dentures (condition 1, n=31). Patients who asked for information on the osseointegration method but did not apply for treatment (condition 2, n=32), and a group of patients that did not ask for information (condition 3, n=10) were also questioned on their satisfaction with dentures. The results indicated that condition 1 subjects were both socially and physically substantially more satisfied with their bridge than with their earlier dentures. On all satisfaction measures condition 3 subjects indicated more satisfaction with dentures than either condition 1 or condition 2 subjects. There were no significant differences between the three groups on several personality characteristics (neuroticism, test-taking attitudes, internal/external control). Condition 3 subjects were less extrovert (socially oriented) than the other subjects. Condition 1 subjects made several suggestions towards improvement of the pre- and post-operation phase, concerning the amount of pain involved and the cleaning of the bridge, etc.

In this article the results are presented of an evaluation of crowns and bridges in a general practice. The study includes 601 solitary crowns, 213 crowns on bridge abutments and 103 crowns on RPD abutments. In total eighty-four bridges were examined. All these restorations were constructed during a period of 11.5 years. By means of the Kaplan-Meier method a prognosis is given of the life span of the different solitary crown-types over periods between 1 and 11 years. The total amount of failures and follow-up treatments on bridge and RPD abutments was very small. The authors also examined whether the bridges were constructed according Ante's law. A follow-up of this study in other Dutch general practices in combination with experimental clinical trials is under way.

Summary 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.

A questionnaire was sent to all 189 edentulous patients with denture adaptation problems who were treated with fixed prostheses on osseointegrated oral implants during the period 1965-1978. One hundred and fifty-two patients (80%) responded. Practically all had adapted well to the prostheses and were most satisfied with the rehabilitated oral function, including chewing ability. Four out of five patients regarded the bridge as part of their own body instead of a foreign object, and 90% would not hesitate to have the treatment performed again, if necessary. Parallel with the improved oral function the patients reported a definite reduction of psychosocial problems associated with their previous oral invalidity, and increased security and self-esteem.

summary The design and application of spring cantilever and direct cantilever bridgework is evaluated in relation to developments in new materials and the significance of the health of the periodontal tissues. Cantilever bridgework is not advanced as a preferred alternative to conventional fixed bridgework but as a means of meeting certain clinical situations which preclude the use of abutment supports at both ends of a bridge. Lack of success in cantilever bridgework can frequently be attributed to the abuse of design rather than failure of the underlying cantilever principle.