Impact of implant number, distribution and prosthesis material on loading on implants supporting fixed prostheses.

The purpose of this study is to evaluate axial forces and bending moments (BMs) on implants supporting a complete arch fixed implant supported prosthesis with respect to number and distribution of the implants and type of prosthesis material. Seven oral Brånemark implants with a diameter of 3.75 mm and a length of 13 and 7 mm (short distal implant) were placed in an edentulous composite mandible used as the experimental model. One all-acrylic, one fibre-reinforced acrylic, and one milled titanium framework prosthesis were made. A 50 N vertical load was applied on the extension 10 mm distal from the most posterior implant. Axial forces and BMs were measured by calculating signals from three strain gauges attached to each of the abutments. The load was measured using three different models with varying numbers of supporting implants (3, 4 and 5), three models with different implant distribution conditions (small, medium and large) and three models with different prosthesis materials (titanium, acrylic and fibre-reinforced acrylic). Maximum BMs were highest when prostheses were supported by three implants compared to four and five implants (P < 0.001). The BMs were significantly influenced by the implant distribution, in that the smallest distribution induced the highest BMs (P < 0.001). Maximum BMs were lowest with the titanium prosthesis (P < 0.01). The resultant forces on implants were significantly associated with the implant number and distribution and the prosthesis material.

Early implant failures in patients treated with Brånemark System titanium dental implants: a retrospective study.

Implant failure has been associated with factors such as poor bone quality, insufficient bone volume, implant instability, unfavorable implant loading, and smoking habits. Infections and host responses may also be important factors in dental implant failure. The objectives of the present study were to identify various explanatory factors associated with titanium implant failure. Forty subjects with stage 1 non-osseointegrated titanium dental implants (NOTI) ad modum Brånemark and 40 age- and gender-matched control subjects with successfully osseointegrated titanium implants (SOTI) were studied. Clinical data and gamma G immunoglobulin (IgG) antibody titers were studied. An independent t test revealed that significantly longer implants were placed in subjects with SOTI (P < .05). Statistically significant differences in bone shape and resorption (BSR) scores were found between SOTI and NOTI (P < .05). Logistic regression analysis identified 3 significant explanatory outcome variables: serum antibody avidity scores for Bacteroides forsythus (P < .0001), serum antibody titers to Staphylococcus aureus (P < .001), and the BSR scores (P < .05). Antibody avidity to B forsythus and antibody titer to S aureus were therefore the 2 most important factors associated with early implant failures and with a significant predictive ability. This indicates that immunologic factors are involved in osseointegration.

Tooth- and implant-supported prostheses: a retrospective clinical follow-up up to 8 years.

PURPOSE: The purpose of this study was to evaluate clinical treatment outcome of fixed prostheses in different sizes and with combinations of different numbers of teeth and implants as abutments. MATERIALS AND METHODS: A total of 115 implants were placed in 36 patients, 75 (65%) in the maxilla and 40 (35%) in the mandible. The implants were connected to 85 abutment teeth, 50 in the maxilla and 35 in the mandible. Of the prosthetic restorations, 19 were gold ceramic, 17 were gold acrylic, three were titanium acrylic, one was titanium ceramic, and one was titanium composite. The observation period ranged from 14 months to 8.9 years. The treatments comprised both fixed partial dentures supported by one tooth and one implant as well as complete-arch fixed prostheses supported by a number of teeth and implants. RESULTS: A total of nine implants were lost, three during healing and six after loading. The postloading cumulative implant survival rate was 89.8% after 5 years. Five abutment teeth were lost, and of the 41 prostheses included in the study, only two (5%) were lost during the observation period. Marginal bone loss was registered around 46 implants at the 1-year follow-up examination. During the following observation period, only slight changes in the marginal bone level adjacent to the implants and teeth were registered. The magnitude of technical complications was low. CONCLUSION: This investigation confirms the findings in similar studies that treatments with periodontally healthy teeth and implants splinted together in rigid one-piece superstructures show excellent long-term follow-up results.

Changes in dental conditions during a decade in a middle-aged and older Swedish population.

A questionnaire measuring dental conditions was sent to 2708 individuals aged 55 79 years in Orebro County, who about 10 years earlier had been randomly selected for a similar study. The response rate was 68% (1848 individuals). Of those, 1665 had participated also in the 1989 study. The objectives were to study changes in dental conditions having occurred during a decade and to evaluate whether impairment in dental conditions among the participants had resulted in prosthodontic treatments. Only small changes in dental conditions were registered among those who participated both in 1989 and in 1999. Loss of a single tooth was the most frequently reported change. Ten per cent fewer reported that they had all teeth remaining in 1999 compared with conditions in 1989. The number of subjects wearing removable dentures increased only slightly. Although the reported changes in dental conditions were small, there had been a need for prosthodontic treatment in many of the subjects. Ten percent of the subjects reported that they had received FPD treatment during the past 10 years. To conclude, the present study showed that only small changes in dental conditions had occurred among the participants during a decade. Nevertheless, a substantial increase in the prevalence of prosthodontic appliances, especially of fixed restorations, was noted.

Dentist-related factors influencing the amount of prosthodontic treatment provided.

OBJECTIVES: To evaluate, using multivariate methods, the associations between indicators of the amount of prosthodontic treatment and dentist-related factors. METHODS: Questionnaires were sent to a random sample of 2,059 general dentists, response rate was 76%. Two indicators of prosthodontic activity were used as dependent variables: 1) reported weekly working hours used for prosthodontics and 2) reported numbers of produced single crowns, fixed partial dentures, and removable dentures. Independent variables were 'social and demographic attributes', 'job situation' and 'attitudes of dentists'. Multiple regression analysis was used in models with continuous dependent variables and logistic regression analysis for categorical dependent variables. RESULTS: 'Weekly working hours used for dental care of adults' showed a strong association in all models with the dependent variable 'weekly working hours used for prosthodontics'. Male dentists provided more prosthodontic services than female dentists, even if reporting less time used for prosthodontics. Private practitioners produced more fixed prosthodontics than dentists employed in the public dental health service. Dentists in the public dental health service reported a higher production of removable dentures than private practitioners. CONCLUSION: The results indicate that factors, besides those in the rational clinical model for decision-making, e.g. gender and delivery system, play a role in the provision of prosthodontic services.

Prosthodontic decision making among general dentists in Sweden. III: The choice between fixed partial dentures and single implants.

PURPOSE: The purpose of this study was to describe how dentists evaluated the importance of various items related to a treatment choice between fixed partial dentures (FPD) and single implants, and to analyze if the differences could be explained by dentist-related variables such as social and demographic attributes, job situation, and attitudes. MATERIALS AND METHODS: Questionnaires were sent to a random sample of 2,059 Swedish general dentists, with a response rate of 76%. In the questionnaire, the choice between an FPD and a single-implant restoration in a clinical situation was presented. Fifteen items were constructed and the dentists were asked to mark on visual analogue scales the relative importance he or she gave the different items. The items were analyzed through principal components analysis, where a three-factor solution was obtained; the factors were labeled as "time," "health," and "comfort." The factors were run as dependent variables in multiple regression analyses. RESULTS: The items evaluated as most important were "prognosis for delivered treatment" and "patient's wish." Large individual differences were seen, but the differences between groups of dentists were small. Male dentists considered the "health" and the "comfort" factors to be more important compared to female dentists. The attitudinal variable "patient information" was significantly associated with the "time" factor and, inversely, with the "comfort" factor. CONCLUSION: Differences between individuals were great, but between groups of dentists the differences were only minor. Multivariately, the attitudinal variable "patient information" showed significant associations with the "time" and the "comfort" factors. Dentist-related variables explained little of the variations. The results further indicated a low personal knowledge concerning implant treatments. Psychologic methods might explain more of the individual differences in prosthodontic decision making, but these are not easily used in a questionnaire study.

Humoral immunity host factors in subjects with failing or successful titanium dental implants.

BACKGROUND: Treatment with titanium dental implants is in general successful. However, an unknown number of implants do not integrate and are removed either by exfoliation or at the time of second stage surgery. It would be of importance to identify subjects at risk and predict early implant failure. METHODS: In a retrospective study serum IgG antibody titers and avidity in sera from 40 subjects who had experienced titanium dental implant treatments with non-osseo-integration as the outcome (NOTI) and in sera from 40 age and gender matched control subjects who had received successful titanium dental implants (SOTI) were studied. Serum IgG titers to whole cell Actinomyces viscosus, Bacteroides forsythus, Porphyromonas gingivalis, Staphylococcus aureus, and Streptococcus intermedius sonicated antigen preparations were studied by ELISA. RESULTS: Serum IgG antibody titers to S. aureus were significantly higher in subjects with SOTI than in NOTI (p<0.001) suggesting that higher titers indicate protection against implant failure as a result of S. aureus infection. Statistically significant higher serum IgG antibody avidity to P. gingivalis and B. forsythus were found in subjects with SOTI than in subjects with NOTI (p<0.01 and p<0.001, respectively). Statistical analysis failed to demonstrate antibody titer or avidity differences to the other pathogens studied. The likelihood that SOTI was associated with a high OD reading for S. aureus was 13.1:1 (p<0.001). Whether subjects were edentulous or not, or if they had lost teeth because of periodontitis or caries did not seem to matter. CONCLUSION: Serum IgG antibodies relative to B. forsythus, P. gingivalis and S. aureus may be associated with the outcome of implant procedures and explain why early implant failures occur.

Congruence between self-reported and actually provided prosthodontic services among Swedish dentists.

The purpose of this study, comprising two parts, was to investigate the congruence between answers given by general dentists in questionnaires concerning prosthodontic services and the recorded information on the services actually performed by each dentist. In Part I it is investigated whether questionnaire reports of weekly working hours devoted to prosthodontics can be used as indicators of actual prosthodontic production. Part II deals with the dentists' self-reported numbers of single crowns, fixed partial dentures (FPDs), and removable dentures. These reported services are compared with the services actually provided. Part I: A regression analysis indicates a lacking precision for the individual dentist, indicated by a relatively low explained variance (R2 = 0.20). However, a highly significant association is seen between the two production measures (P = 0.000). Part II: The congruence between stated and actually provided services is higher for single crowns and removable dentures than for FPDs. Bivariate regression models are statistically significant for all three services. In Part II, the reported weekly working hours used for prosthodontics covaries significantly with prosthodontic production, but the association is not as strong as in Part I. Although the precision in both Part I and Part II is low for the individual dentist, the questionnaire measure is found to be useful as an indicator in a population of dentists. It is concluded that the questionnaire data can be used as reasonably valid expressions of prosthodontic activity in population-oriented analyses among general dentists.

General dentists' attitudes toward delegation, information, and patient influence in a prosthodontic context.

PURPOSE: The aim of this study was to investigate attitudes among general dentists in Sweden in relation to gender, age, prosthodontic activity, and dental delivery system (private or public). MATERIALS AND METHODS: Questionnaires were sent to a random sample of 2,059 dentists, and a response rate of 76% (1,567 dentists) was achieved. Among those who responded, 50% were private practitioners and 50% were publicly employed practitioners; 42% were female and 58% were male. The questionnaire contained 10 statements aimed at measuring attitudes. Their dimensionality was analyzed using principal components analysis. The resulting factors were related to delivery system (public or private), gender, age, job satisfaction, and weekly working hours used for prosthodontics in multiple regression models. RESULTS: There was a wide variation in the answers to the statements, indicating great individual differences in opinions among dentists. Several distributions differed with respect to gender and delivery system, but the mean differences between various groups of dentists were small. The most affirmative attitude was shown for delegation of impression taking to auxiliaries (mean 6.7; SD 1.8), and the most negative attitude was shown for close cooperation between dentists (mean 1.8; SD 1.4). The factor analysis gave 3 factors, with a variance explanation of 57%. Regression models for the 3 attitude dimensions ("patient influence," "delegation," and "patient information") showed that female dentists felt more positive about delegation and information than male dentists. The explained variance was very low for all 3 models and varied from 0.01 to 0.05. CONCLUSION: Although the differences in attitudes between various groups of dentists were statistically significant, these differences were small in relation to the large variation in attitudes among individual dentists.

Prosthodontic decision making among general dentists in Sweden. I: The choice between crown therapy and filling.

PURPOSE: The purpose of this study was to analyze dentists' evaluations of factors related to the choice between crown therapy and filling and to possibly explain this by social and demographic attributes, job situation, and dentists' attitudes. MATERIALS AND METHODS: Questionnaires were sent to a random sample of 2,059 Swedish dentists. The response rate was 76%. In the questionnaire the choice between crown therapy and filling in a clinical situation was presented. The dentists were asked to mark their assessments of the relative importance of the different items on 14-item visual analogue scales (VAS). Multiple regressions were run for all 14 items. RESULTS: Large individual variations were seen among the dentists regarding the stated importance of the various items. The items rated as the most important were "patient's wish" and "treatment prognosis," and the items rated as least important were "treatment time required" and "number of visits required for treatment." The differences between groups were small, and for no item exceeded 0.7 step on the 8-grade VAS scale. No data reduction was possible using principal components analysis. CONCLUSION: The study showed great variations among individual dentists. The dentist-related factors explained little of the variance. The results indicated that the questionnaire instrument did not fully capture the real influences on the treatment choice between a filling and an artificial crown.

Prosthodontic decision making among general dentists in Sweden. II: The choice between fixed and removable partial dentures.

PURPOSE: The purpose of this study was to describe how dentists evaluated various items related to a treatment choice between fixed partial dentures (FPD) and removable partial dentures (RPD), and to determine if the differences could be explained by dentist-related variables ("social and demographic attributes," "job situation," and "attitudes"). MATERIALS AND METHODS: Questionnaires were sent to a random sample of 2,059 Swedish general dentists, with a response rate of 76%. In the questionnaire, the choice between FPDs and RPDs in a clinical situation was presented. The dentists were asked to mark on 14-item visual analogue scales the relative importance he or she gave the different items. The items were analyzed through principal components analysis, where a 3-factor solution was obtained; the factors were labeled as "time," "health," and "comfort." The factors were run as dependent variables in multiple regression analyses. RESULTS: Great individual variations were seen, but the differences between groups of dentists were small. The items evaluated as most important were "patient's wish," "condition of possible abutment teeth," and "prognosis for delivered treatment." Male dentists gave significantly greater importance to the "health" factor compared to female dentists. The attitudinal variable "patient information" showed significant associations with all 3 factors in the multivariate models. CONCLUSION: Great individual differences were seen regarding the importance of the various items. In multiple regression models, several independent variables showed significant associations, most interestingly the attitudinal variable "patient information." Low explanatory (R2) values indicate that it is necessary to capture more variables of importance for the prosthodontic decision-making process.

Practice profile differences among Swedish dentists. A questionnaire study with special reference to prosthodontics.

A questionnaire measuring differences in prosthodontic practice profiles was sent to 2100 Swedish dentists working as general practitioners. The response rate was 76%. Among the responders, 58% were men and 42% women. Fifty per cent were private practitioners, the other 50% being publicly employed. The practice profile variables showed a great variation, and several of the distributions differed with regard to sex and dental care system. The working hours per week the time spent on prosthodontics were on average higher for men than for women. Private practitioners more frequently worked in large communities and cities than did dentists working in the Public Dental Health Service. Practically all (98%) of the private practitioners used more than 75% of their clinical time on treating adults, compared with less than half of the dentists in the Public Dental Health Service. Male dentists reported higher percentage figures with regard to clinical time used for dental care of adults and for prosthodontic services than did female dentists. The figures for fixed prosthodontic service rates varied in the same manner. Fixed prosthodontic services were much more common in private practice than in the Public Dental Health Service, in which more removable dentures were made. Even though private practitioners used more time for prosthodontic services, they referred fewer patients to specialists in prosthodontics and consulted a specialist less often than did the dentists in the Public Dental Health Service.

A questionnaire instrument to assess clinical decision-making in prosthodontics among general practitioners.

There are great variations in dentists' choice of treatment. The aim of this study was to evaluate a Patient Paper Case (PPC) technique to investigate such variation, adjusted for prosthodontics. The questionnaire was sent to all 131 general practitioners (GP) in the Public Dental Service in Orebro County and to all 100 GPs in private practice in Skaraborg County, Sweden, with 81% responding. There were three PPC questions, concerning 1) crown therapy or amalgam/composite filling, 2) fixed or removable partial denture, 3) fixed partial denture or single implant restoration. Respondents were asked to assess 13 or 14 items concerning the patient, dental conditions, and own skills. There was great variation in responses. In factor analysis four factors were found to capture between 54% and 60% of the variance of the items. They were interpreted as a time factor, a patient subjective factor, a clinical factor, and finally, for the PPC 1 and 2, a general health factor. The Swedish insurance regulations of single implant therapy, mandatory caries/filling-free, and vital adjacent teeth were reflected in the factor solution of PPC 3. It is concluded that the PPC method is feasible and useful in studies of clinical decision-making in prosthodontics.

Quality of intraoral radiographs used for prosthodontic treatment planning by general dentists in the public dental health service.

The image quality of intraoral radiographs used by general public health dentists in prosthodontic treatment planning was evaluated on 763 radiographs from 72 consecutive cases. It was found that 349 (45.7%) radiographs were without any type error and that 414 radiographs had a total of 577 errors. The most common errors were projection and film density errors. The number of submitted radiographs ranged from 2 to 22. Three prosthodontists evaluated if the radiographs gave "satisfactory" or "not satisfactory" information for approval or not of the proposed treatment. Of the 72 cases did 34 (47%) not meet the criteria for acceptance. For the cases where the prosthodontists found the radiographic documentation "satisfactory", the mean number of periapical radiographs was 10.8, while for cases found "not satisfactory" the mean number was 7.1. This difference was found to be statistically significant (p < 0.01). It was shown that nearly every seventh tooth planned to be used as an abutment was radiographically not properly documented. The poor radiographic quality found in this study and in other similar studies should be taken into serious consideration, especially as prosthodontic treatment accounts for a substantial part of the total costs for dental insurance in Sweden.

Image quality of intraoral radiographs used by general practitioners in prosthodontic treatment planning.

A number of studies have shown a low standard of radiographic image quality in general dental practices. Image quality was evaluated on 1094 radiographs from 100 consecutive cases submitted to a dental insurance office for approval of planned prosthodontic treatment. It was found that only 404 radiographs were without any type of error and that 690 radiographs had a total of 959 errors. The most common errors were projection and film density errors. The number of submitted radiographs ranged from one to 40. Nearly every fourth tooth proposed for treatment was not properly documented. The results also showed that 43 of 100 cases did not meet the criteria for acceptance for assessment of the proposed prosthodontic treatment. This means that they were incompletely documented radiographically so that the treatment plan could not be evaluated. This study suggests that new or additional radiographic documentation ought to be requested frequently before approval of proposed treatment plans.

Some factors influencing the quantity of prosthodontic treatment performed by general practitioners in public dental service.

For general dentists in public dental service, Orebro county, the numbers of artificial crowns, pontics, RPD:s and CRD:s produced in 1989 were studied in relation to some background factors. The dentist-related factors were: gender, time in profession, working time per week, and place of graduation. Factors related to dental clinics were: location of the clinic, general prosthodontic activity at the clinic. Multiple regression analyses were used. Two different patterns were found; one for fixed prosthodontics, another for removable prosthodontics. Prosthodontic activity at the clinic, the male sex, and (inversely) time in profession were significantly associated with high production of artificial crowns and pontics. The regression models for removable prosthodontics showed no significance.