While the prosthodontic management of patients with fixed partial dentures, removable partial dentures, and complete dentures represents a routine situation in daily dental practice, a lot of patients have difficulties adapting to the sensation of a foreign body 1. This may be due to the fact that the oral environment is an extremely sensitive region 2 which can be affected by both physical and psychological stressors 1. To give an example for physical impairment as a result of prosthodontic management: wearing removable partial or complete dentures often impairs masticatory function and speech transiently 23. Further physical problems such as soreness of denture-supporting tissues, tooth movement, carious lesions at the abutment teeth 4, and temporomandibular disorders 15 have been documented. Apart from these physical reasons that may potentially cause problems following prosthodontic management, several authors also underline the role of psychological factors in the process of accepting removable dentures and adapting to them 3567.

In general, psychological response to tooth loss and denture wearing may be influenced by the patient's personality and, thus, may sometimes depend less on the technical quality of the dentures 3. For instance, one investigator found somatization to be a factor in general dental practice per se 8, whereas some researchers assumed subjective body complaints to be an indicator of somatization particularly in elderly patients 9. Hence, a clear association between age and irreversible complications during prosthetic rehabilitation has been found 10 and, eventually, many of these patients are referred to specialized dental clinics, such as prosthodontic outpatient clinics at university hospitals.

Another group of patients that is typically referred to special university-based care clinics consists of patients suffering from temporomandibular disorders (TMDs). Although various factors, such as anatomy, trauma, pathophysiology, and psychology have been suggested to be involved in the development of TMD, the etiology has not definitely been clarified so far 11121314. According to the literature, psychosocial factors have become a field of increasing interest. For instance, several studies have clearly indicated that compared to matched controls TMD patients had higher levels of psychological distress, including anxiety, somatization, and depression 151617.

Considering this and the fact that typically both prosthodontic outpatient clinics and TMD/orofacial pain outpatient clinics are university-based care centers, patients in these institutions were not really found to be representative and thus cannot easily be compared with patients from a general dental practice. In particular, the extent of psychological impairment of patients seeking care at a prosthodontic outpatient clinic (POC) was regarded to be more obvious than in those patients that usually turn to their general dental practitioner. Hence, a comparison of patients of two different outpatient clinics appears to be more appropriate for the evaluation. Moreover, given the fact that these outpatient clinics take part in university education programs, potentially beneficial insights resulting from such observational investigation might have a favorable effect on future education plans. Therefore, the purpose of the present prospective observational study was to compare patients of a POC of the Department of Prosthodontics at the University of Duesseldorf with patients seeking care at the TMD/Orofacial Pain Outpatient Clinic (TMD/OFPOC) at the same university. We examined sociodemographic data, self-reported somatic complaints, and psychological impairment. The hypothesis used in this investigation was that groups differ significantly regarding their sociodemographic data and self-reported somatic complaints. Conversely, it was expected that there is no difference between both groups regarding the extent of psychological impairment.

As seen in Table 1, the comparison between patients from the POC and patients from the TMD/OFPOC revealed statistically significant differences with respect to age, gender, the duration of complaints, and the type of referral, whereas the evaluation of further sociodemographic variables, such as education, marital status, and residence, showed no significant differences between both groups (Chi-square; p = n.s. = not significant). Considering the career, patients from the TMD/OFPOC were significantly more ambitious than patients from the POC. To specify only the most relevant groups, 20% of patients from the POC and 43.3% of patients from the TMD/OFPOC were employed, 9.2% and 13.3% were in leading positions, 18.5% and 13.3% were housewives, and 30.8% and 8.3% were pensioners, respectively (Chi-square test; p < 0.05).

In 11 of the 21 items, the analysis of the distribution of somatic complaints revealed the following statistically significant differences (Table 2): patients from the TMD/OFPOC reported more frequently joint sounds in general, an impaired mandibular movement or function (such as opening, yawning, chewing), masticatory muscle discomfort, problems to correctly bring maxillary and mandibular teeth together as well as oral habits like lip biting. Moreover, these patients stated that, immediately prior to the consultation, they did not receive as much extensive prosthodontic rehabilitation as patients from the POC. Finally, patients from the TMD/OFPOC unambiguously expressed the necessity of their complaints to be treated.

Considering psychological impairment due to distress perceived during the past seven days, the comparison of the two clinical groups did not show any differences between both groups (Table 3). In neither a subscale nor in the GSI statistically significant group differences were obtained. To estimate the clinical relevance of the recorded data, the above described reference values were applied (Table 4). In consideration of these reference values, no group specific differences were observed again. Even though data failed to reach the level of statistical significance, on the basis of the present findings, the GSI values of 31.3% of patients from the POC and 30.5% of patients from the TMD/OFPOC were clearly located above the GSI values that were obtained from a normative sample. In 21.9% of patients from the POC and in 22.0% of patients from the TMD/OFPOC, the extent of the determined psychological impairment reached values that were in the range of psychotherapeutic outpatients and, moreover, in 9.4% and in 8.5% values in the range of psychotherapeutic inpatients, respectively (Chi-square; p = n.s. = not significant).

This prospective observational clinical study compared patients from the POC at the University of Duesseldorf with patients from the TMD/OFPOC at the same university regarding sociodemographic data, self-reported somatic complaints, and psychological impairment. As a major finding, the results clearly demonstrated that the degree of psychological impairment was similarly high in both groups. Interestingly, in approximately one third of the evaluated patients of both the POC and the TMD/OFPOC the psychological impairment reached values that were located in the range of psychotherapeutic outpatients and psychotherapeutic inpatients. Indeed, this important finding supports numerous studies which revealed psychological characteristics in TMD patients 1314151617262728. Moreover, these results particularly stress the fact that patients from a POC represent a different group of patients showing a similar pronounced psychological impairment than do TMD patients.

Apart from dentistry, previous investigations have recorded the urban prevalence of psychiatric disorders in general practices. While depressive and anxiety disorders were detected in 15% to 25% of the patients from a general practice 29, surveys which have analyzed the entire prevalence of psychiatric disorders obtained values ranging from 21% to 52% 2530313233. With respect to the portion of psychologically impaired patients, it might be concluded that the present values established in the two university-based care centers are largely comparable to that derived from general practices.

Potential reasons for the magnitude of psychological impairment found in patients from a POC might be due to the reciprocal influences of tooth loss or denture wearing and psychological factors. For instance, some previous investigators suggested that the psychological response to tooth loss and denture wearing may be affected by patients' personality traits, sometimes more than by the technical quality of the dentures 36. Conversely, tooth loss is reported to cause psychological impairment 3 and, moreover, previous investigators have shown that it contributes to a reduced quality of life 34.

The sociodemographic and reported somatic complaints data showed significant differences between the two groups, especially concerning age, gender, and most of the characteristic TMD symptoms. These findings were detected as a result of the sample composition. The unequivocal differentiation of the two groups by means of the reported somatic complaints, underlines the absence of any mixing between the two outpatient clinics. It might have been expected that patients suffering from tooth loss and, consequently, seeking prosthodontic management were on an average older than a group of patients from a TMD/OFPOC. Interestingly, in contrast to the patients from the TMD/OFPOC the prosthodontic outpatients revealed a comparatively balanced gender distribution. Most of these patients sought care at the POC due to apparently somatic reasons such as the improvement of mastication or speech. The reasons differ from those reported by patients from the TMD/OFPOC. Potentially, such motives do not require a greater health awareness 3536 or specific experiences with the health care system 37 as they have been discussed to explain the pronounced female proportion in TMD patients.

Notwithstanding that groups differed with respect to age and gender, the comparison of patients of these two university-based care centers was found suitable for the following reasons: although previously several authors have discussed the interaction between psychological factors and tooth loss and/or subsequent prosthodontic management with removable dentures 3567, to date, little is known of the extent of psychological impairment in patients seeking care for prosthodontic rehabilitation. Consequently, in a first exploratory approach patients collected from a POC should be investigated. Indeed, patients from a university-based care center represent a highly specific sample that may not easily be compared with patients from a general dental practice. However, if sociodemographic data of the patients seeking care at the POC of the Department of Prosthodontics at the University of Duesseldorf are compared with data derived from other German prosthodontic departments, they appear to be representative for these specific German care centers 3438. Regarding an adequate control group for the patients from the POC, a decision was made to investigate patients from a TMD/OFPOC at the same university due to diverse reasons. Firstly, these patients were recruited from a different university-based care center and, thus, represent a likewise highly specific sample. Secondly, many studies have underlined the contribution of psychological factors in the etiology of TMD 1516172728. This is also reflected by the currently highest standard for the diagnosis of TMD (i. e. RDC/TMD) due to the fact that it includes the assessment of specific psychological symptoms such as depression 1839. Therefore, TMD patients represent a group of patients who might be considered as a quite appropriate sample to compare the magnitude of psychological impairment.

The results of the present findings reproduce the typically clinical conditions and the complexity of the clinical reality 40 in German outpatient clinics. Keeping in mind that these clinics take part in university education programs and given the determined huge number of psychologically impaired patients from both the POC and the TMD/OFPOC, one might be in favor of asking to what extent these conditions find an adequate consideration in current dental education plans. In particular, in consideration of the increasing knowledge of the association between TMD and psychological factors, this demand has already been verbalized by different investigators many years ago 414243. Therefore, further investigations are required to substantiate the need of an increased consideration of psychological aspects in future dentistry.

Within the limitations of this study, in approximately one third of the evaluated patients of both the POC and the TMD/OFPOC the psychological impairment reached values similar to those of psychotherapeutic outpatients and psychotherapeutic inpatients. Therefore, the present findings emphasize the need to intensify the integration of psychosomatic aspects into dentistry and, in particular, to add psychological considerations to future German education plans.

(POC): Prosthodontic Outpatient Clinic; (TMD/OFPOC): TMD/Orofacial Pain Outpatient Clinic.

The authors declare that they have no competing interests.

AH, US, and JK conceived the study design, MAO performed the statistical data analysis and wrote the manuscript, JGKH, RAD, SZ, and WHMR participated in the early preparation of the manuscript and contributed to write the revised version of the article. All authors read and approved the final manuscript.