Patient orientation as a future topic in oral health rehabilitation

For many years, dental treatments have mostly been evaluated through changes in clinical findings. The survival time of dentures is one of the most important success parameters in prosthetic dental therapies (Lang et al. 2004; Pjetursson et al. 2004a; b; Tan et al. 2004). Other clinical-technical success parameters include a small marginal gap in a restoration, optimal retention of removable dentures (partial dentures) and adequate function in terms of phonation and mastication. At the same time, an assessment of the biological status (pain, caries, periodontitis, tooth loss) can be used to demonstrate oral health and to determine the need for treatment and the effects of dental therapies. These parameters have been examined in numerous clinical studies and allow clinically easily predictable treatment results for most patients (Creugers et al. 2005; Fokkinga et al. 2007; Heydecke and Peters 2002; Kreissl et al. 2007; Priest 1996; Walter et al. 2010 ; Wostmann et al. 2005).

>> However, an improvement in clinical symptoms and functional aspects cannot in principle be equated with treatment success (Celebic et al. 2003; Chamberlain et al. 1984). Despite treatment being assessed as clinically successful, this assessment often does not correlate with the patient's subjective assessment (Marachlioglou et al. 2010). This discrepancy between objective assessment (by practitioners) and subjective assessment (by patients) is based on differences in the criteria used to evaluate the treatment outcome. While practitioners evaluate the success of a treatment using the criteria mentioned above, these are at least partially of secondary importance for patients or are not primarily evaluated but rather based on the consequences of the complex interactions. Functional, psychological and social changes are much more important in patients. This is why we speak of a biopsychosocial (disease) model, which does justice to all relevant aspects from the perspective of both practitioners and patients.
A biopsychosocial understanding of illness takes particular account of the fact that pain is often accompanied by psychosocial impairments (Von Korff et al. 1992). Furthermore, it does justice to the fact that the loss of teeth, one of the central treatment indications in restorative dentistry, is a loss of structure that cannot currently (yet) be completely restored in the sense of restitutio ad integrum. Rather, as with all chronic diseases, a defect will remain (World Health Organization 2001). The treatment is not causal but symptomatic. It aims at comprehensive functional, psychological and social rehabilitation of patients. Against this background, the patient's perspective becomes particularly important when assessing oral health and evaluating therapy results.
Patient-based outcomes
in dentistry
In dentistry, patient orientation usually refers to the inclusion of patient-based outcomes in clinical studies. Two concepts of patient-based target variables can be distinguished in dentistry. Satisfaction is used to evaluate the results of dental therapies or the treatments themselves in relation to patient expectations. The concept of quality of life captures the extent of functional possibilities, psychosocial aspects and pain that are influenced by problems in the oral area.
satisfaction
The area of application for satisfaction measurements primarily comes from quality analysis. Three basic areas can be distinguished (Donabedian 1988). Assessments of the structural requirements of medical care are recorded as structural quality. Process quality is used to evaluate the processes of specific (dental) medical interventions. Results of these interventions are recorded using outcome quality.
Initially, patient satisfaction was primarily assessed in relation to structures of dental treatment (e.g. accessibility of the doctor, opening times, costs and reimbursement, ambience, technical and human quality of the treatment) (Davies and Ware 1981; Hengst and Roghmann 1978; Heydecke 2002a; Ware et al. 1983). More recent studies are increasingly focusing on determining satisfaction with treatment results (Awad and Feine 1998; Heydecke et al. 2008). As quality management in dentistry becomes increasingly important, patients' subjective feelings during dental treatments are increasingly viewed as an indicator of process quality.
A major limitation of the concept of patient satisfaction is the insufficient support of a theoretical definition. Therefore, the concept of quality of life is used far more frequently as a patient-based target in dentistry.
life quality
The concept of quality of life was originally developed in social science welfare and social indicator research (Zapf 1984). In contrast to the very extensive concept of general quality of life, the concept of quality of life in medicine is limited to recording subjective indicators of health (Heydecke 2002b).
The oral health-related quality of life concept most commonly used in dentistry is based on Locker's 1988 model of oral health (Locker 1988). According to the World Health Organization's International Classification of Impairments, Disabilities and Impairments, the model represents a continuous chain from the disease through functional limitations and psychological impairment to social disadvantage (World Health Organization 2001).
The Oral Health Impact Profile (OHIP), developed by Slade and Spencer in 1994, has become established in determining oral health-related quality of life (Slade and Spencer 1994; Slade 1997). The OHIP is based on Locker's conceptual model (Locker 1988). According to this model, the OHIP questions only capture negative aspects of health (higher scores indicate a poorer quality of life). Even if the factorial structure (dimensions) of the OHIP has not been conclusively clarified (John 2007) and there are further conceptual criticisms (Kieffer et al. 2009), the OHIP represents the gold standard in dentistry for determining oral health-related quality of life. The OHIP has been validated and available in at least 20 translations (e.g. John et al. 2002; Larsson et al. 2004; Pires et al. 2006; Szentpetery et al. 2006; Wong et al. 2002; Yamazaki et al. 2007).
Two scientific topic areas are currently relevant in dentistry when it comes to patient-oriented target variables: clinical studies on the impairment caused by illnesses and the effects of therapies are contrasted with methodical studies on measuring instruments for quality of life.
Clinical examinations for oral health
The clinical studies determine the effects of various oral diseases (Table 1) on patients' quality of life, compare disease effects and determine the effects of dental therapies on patient-related outcomes.
Selected studies on these questions will be presented below.
Impact of diseases
and impairments
Dentistry is not “only” concerned with teeth, oral mucosa and tooth-bearing bone, but also with the chewing muscles and jaw joints (Table 1). Diseases that affect the chewing muscles and the jaw joints are summarized under the term craniomandibular dysfunctions (CMD) (Okeson 1996). The main symptoms of CMD are pain in the regions mentioned, limitation of lower jaw mobility and jaw joint noises during lower jaw movements. In the adult general population, painful CMDs represent a significant public health problem with a prevalence of approximately 10 % (LeResche 2001). The pain and functional limitations mean that CMD can be expected to have a strong negative impact on the quality of life of patients.
In a current study, the OHIP was used to compare the oral health-related quality of life of consecutively recruited patients with different diagnoses of CMD (N=416) with people from a random sample of the general population (N=2026) (John et al. 2007b). The patients were examined according to a validated and internationally used diagnostic scheme - the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) (Dworkin and LeResche 1992; John et al. 2006). It was shown that patients with a CMD diagnosis had a significantly more impaired quality of life than was the case in people from the general population. Furthermore, there were different influences of CMD on quality of life depending on the specific diagnosis (Fig. 1).
These differences become particularly evident when determining the specific influence of one or more CMD diagnoses (Reissmann et al. 2007). For this purpose, the OHIP values of people from the general population without a CMD diagnosis were subtracted from the values of CMD patients. The difference in the OHIP sum value that was caused only by the CMD diagnosis was determined. Pain-associated CMD diagnoses (Group I and Group III) led to a greater reduction in quality of life compared to pain-free CMD diagnoses (Group II) (Figure 2). If two CMD diagnoses were present at the same time, the impairment was at the level of a pain-related diagnosis. A third diagnosis did not result in further deterioration in quality of life (Figure 2). The value of almost 40 OHIP points therefore represents the maximum expected impairment of oral health-related quality of life due to CMD (Fig. 2).
Comparison of diseases
Another area of application for instruments to determine oral health-related quality of life is the comparison of the effects of different diseases. It is possible not only to determine the complete impairment of the patient based on total values, but also more differentiated considerations at the level of the quality of life dimensions or the individual Aspects of quality of life possible.
When comparing the answers to the 14 questions of a short version of the OHIP from people in the general population with patients with craniomandibular dysfunctions (CMD) and patients with fear of dental treatment, a significantly reduced quality of life was found in the two patient groups (Schierz et al. 2008). There were hardly any differences in functional limitations and pain between CMD patients and patients with dental fear (Fig. 3).
In contrast, patients with fear of dental treatment had significantly higher scores than patients with CMD, especially in psychosocial aspects (Fig. 3). This approach to the patient's (limited) quality of life allows a more precise assessment and a better understanding of the patient's perspective. This is important for diagnosis and planning individual therapy.
Effects of dental therapies
In addition to the impact of oral diseases on quality of life, special attention is paid to reducing impairments and thus improving patients' quality of life through dental therapies. Several studies have demonstrated an (at least short-term) increase in oral health-related quality of life for therapies with dentures (Heydecke et al. 2003; John et al. 2004; Nickenig et al. 2008).
The improvements in quality of life are sometimes so great that they can also be demonstrated using a single global question about self-assessment of oral health with 5 answer categories (from “poor” to “excellent”) (John et al. 2007a; Reißmann et al. 2006). About a third of the patients in this study experienced an improvement in their self-assessment. But not only is the patient's perceived oral health influenced, it can also lead to an improvement in the patient's self-assessment of their general health (Reissmann et al. 2011b). While 15.4 % patients experienced a deterioration in their self-assessment, 22.2 % reported an improvement. Taking into account normal fluctuations due to external influences and measurement errors, there was a net effect of 6.8 % improvement (p < 0.05). This means that a direct (positive) effect of dentistry on self-perception of general health can be demonstrated. This highlights the importance of dentistry in patients' perceptions of health.
Long-term studies on dental therapy effects have so far been rare. A study of prosthetic patients over a follow-up period of up to two years was also able to demonstrate the medium-term positive effect of prosthetic therapy on the patients' quality of life (Reißmann et al. 2008). Despite some fluctuations during the observation period, the initial therapeutic effect of the dentures was still present after two years (Fig. 4).
A differentiated examination of the therapy effects according to the prosthetic treatments (fixed dentures, removable dentures, complete dentures) revealed significant differences in the extent and period of the detectable changes (Fig. 5). The deterioration in quality of life in patients with complete dentures after six months was a measurement artifact due to the very small number (N=14) of patients in this group. Quality of life was still improved in 62.7 % of all patients at the end of the 2-year period compared to the time point before therapy (p < 0.01). It can be concluded that extensive prosthetic therapies significantly improve oral health-related quality of life over a period of at least two years (Fig. 5).
Methodical studies on
measuring instruments
Comparability of study results
An essential criterion in the evaluation of quality of life measurement instruments was defined by the Medical Outcome Trust as the comparability of alternative forms of assessment (Scientific Advisory Committee of the Medical Outcomes Trust 2002). Only this can ensure that results from different studies in which data were collected using different methods can be compared.
In a current study (Reissmann et al. 2011a) on this question in prosthetic patients using the German version of the OHIP (John et al. 2002; Slade 1997) it was found that the information, which was obtained using various methods (personal interview, Telephone interview, self-completed questionnaire) were almost identical (reliability: ICC=0.90; 95 % confidence interval=0.85-0.95). The proportion of the total variance explained by the survey mode was only 0.5 %. This demonstrated that the survey mode has no significant influence on OHIP values in prosthetic patients.

Determination of treatment effects - retest effects
An essential element in the use of patient-oriented outcome measures is their ability to determine the influence of interventions by determining differences between measurements before and after therapy. These differences are viewed as a measure of the therapy effects. A basic requirement is that both measurements are independent of each other, ie the second measurement is not influenced by the results of the first measurement (e.g. by memory) (McKelvie 1992). Such retest effects would otherwise make it significantly more difficult to determine short-term therapy effects and acute problems and reduce the differences between the different measurement points (Ormel et al. 1989; Pevalin 2000).
A recent study operationalized retest effects as differences in reliability coefficients between different lengths of time between survey points and as the influence of the time intervals between two measurements on the difference in the associated reliability coefficients (John et al. 2008). For this purpose, the OHIP was recorded in 21 patients twice in one day at an interval of 1 to 2 hours and again after 3 to 78 days. The difference in the reliability coefficient for the two measurements on the same day and the coefficient for the measurements on two different days was small (∆rho=0.08; p=0.02). The influence of the time between two measurements on the reliability coefficients was small and not statistically significant (regression coefficient for 1 day: -0.04; 95% CI: -0.29 - 0.21; R2 and adjusted R2 < 0.01). These results demonstrate that repeated measurements of oral health-related quality of life over short periods of time in the face of rapidly changing oral health also lead to a valid determination of change. This significantly expands the area of application of the OHIP.

Determination of treatment effects - response shift
Patients can change their own concepts of quality of life and internal standards during treatment. This change in the basis of determination is referred to as response shift. The clinical significance of this phenomenon could not yet be determined by either the direction of the effect or its extent (Schwartz et al. 2006). An initial study in edentulous patients concluded that response shift led to masking of treatment effects of new complete dentures on patients' oral health-related quality of life (Ring et al. 2005).
A study in a consecutively recruited sample of 126 patients requiring prosthetic treatment determined the response shift of the OHIP (Reißmann et al. 2010). The OHIP was applied immediately before therapy and a few weeks after completion of therapy. When patients assessed their quality of life after treatment, they were asked to assess their quality of life again (retrospectively) before treatment, without having access to the baseline data. The difference in the therapeutic effects determined between prospective and retrospective observation was 6.3 OHIP points (p < 0.001). According to Cohen's definition (Cohen 1988), the effect size can only be considered small. Although it is currently not known whether prospective or retrospective determination of changes in MLQ is more valid, the treatment effects perceived by patients appear to be greater than previously assumed.

Determination of treatment effects - minimal noticeable difference
The assessment of changes in quality of life requires that it is known which change in quality of life is perceived by the patient. This value of the change is referred to as the minimally noticeable difference (Minimal Important Difference; MID). The MID is defined as the smallest change in a target variable that is perceived by the patient as beneficial and which, in the absence of undesirable side effects and excessive costs, leads to a change in patient care (Jaeschke et al. 1989). A review of various instruments for recording patient-related outcome measures found that the MID would correspond to half the standard deviation of the difference (effect size of 0.5) (Norman et al. 2003).
In one study, the MID of the OHIP was determined by agreement with a global change question (John et al. 2009). In addition to the prospective use of the OHIP, patients were asked to provide a comprehensive assessment of the change in quality of life following prosthetic therapy (response categories: “much improved”, “somewhat improved”, “stayed the same”, “somewhat worsened” and “very worsened”). Of 224 patients, 47 stated that they had a “somewhat improved” quality of life after therapy. In this group of patients, a difference in OHIP values and thus an MID of 6 OHIP points (95% confidence interval: 2 - 9) was determined. This value is an important parameter for determining clinical significance in relation to patient-related outcomes.
outlook
Efficiency of dental therapies
With ever increasing cost pressure in the healthcare system, the efficiency of dental interventions is becoming increasingly important. The statutory health insurance (GKV) expenditure on dental and prosthetic care fell from EUR 3.48 billion in 1991 to EUR 2.92 billion in 2008 (National Association of Statutory Health Insurance Dentists - KZBV 2009). In order to use these resources efficiently, dental therapy must also be viewed from the cost-benefit aspect.
Studies on cost-benefit analyzes of dental therapies are rare and mostly relate to prosthetic dentures. In a study on the treatment of edentulous patients with either conventional complete dentures or with implant-supported overdentures, the effective costs for each desired improvement in quality of life were determined over a period of almost 18 years (Heydecke et al. 2005). This enables patients to individually weigh up the costs and benefits and thus make a better-informed treatment decision.
In a review, the aftercare effort for implant-supported fixed dentures was compared with removable partial dentures (Pieger and Heydecke 2008). The study came to the conclusion that removable dentures require more follow-up care and higher follow-up costs.
Cost-benefit analyzes are important for health policy makers and provide information to help patients make informed decisions about dental therapies. This will lead to a greater patient focus in dentistry. Further studies are definitely desirable.

Decision making and patient orientation
Another important topic is the decision-making process. This can be done in various ways during (dental) medical treatments. In the paternalistic model, the patient plays an almost exclusively passive role (Coulter 1999). In the information model, information flows unidirectionally from the dentist to the patient (Charles et al. 1997). The dentist provides the information and the decision is made independently by the patient. Between these two models lies the concept of participatory decision-making (PEF; shared decision-making, SDM), in which patient and practitioner consider the decision together and make it together (Chin 2002; Härter et al. 2005). This strategy represents an optimal compromise between the treatment freedom of the practitioner and the patient's right to co-determination and is currently viewed as the optimum for doctor-patient communication.
A study of the approach to clinical decisions among dentists working in prosthodontics in North America showed that around half (50.8 %) of the dentists surveyed are of the opinion that the decision should be made in an equal discussion between patient and dentist (Koka et al. 2007 ). Almost the entire remainder of those surveyed (43.3 %) placed their own opinion and assessment behind that of the patient. This result is confirmed by an examination of dentists in Sweden. When choosing the therapy, the focus was on aspects such as “the patient's wishes” and “prognosis of the treatment” (Kronstrom et al. 1999a; b). Even if these studies show a very positive picture of patient involvement in dental treatment decisions, they only reflect the dentists' own assessment.
A study in Great Britain into patient perceptions showed a different picture. Of 40 dental patients, the majority of patients preferred equal decision-making (Chapple et al. 2003). In contrast, their own role in decisions was perceived as more passive. Contrary to their own wishes, patients received little or no involvement in the decision-making process. This obvious conflict needs to be resolved in the future.
Further investigations into indication- and setting-specific factors influencing participation preferences should lead to a better understanding of the patient's perspective and to increased patient participation in decision-making. Through more intensive communication between patients and practitioners, patients can become aware of their own responsibility with regard to the therapy results, which can have a positive effect on long-term therapy success (Sadan 2005; 2007). Furthermore, through increased patient involvement, improved therapy adherence (compliance), higher satisfaction with the therapy and the therapy result, and an increase in the patient's level of knowledge are possible (Johnson et al. 2006; Joosten et al. 2008; Loh et al. 2007). Therefore, the decision-making process in the context of patient orientation in oral health rehabilitation represents an important field of research that needs to be intensified.
conclusion
Patient orientation will increasingly become the focus of scientific studies in dentistry. While concepts such as satisfaction and quality of life are currently mostly involved as target variables in clinical studies and as an object of investigation in methodological studies, in the future cost-benefit analyzes of dental therapies and patient participation in diagnostic and therapeutic decisions will increasingly be the subject of research. <<