The aim of this study was to evaluate a digital procedure to extract periodontal-related patient records from private practices and to analyse the extracted data to support a practice-based research network.
The average patient age across all 9 practices was 55.76 years, which was older than the average in other previous long-term retrospective studies, such as Carnevale et al., 2007a, 2007b with 53 years, Eickholz et al., 2008 with 46.6 years, and König et al., 2002 with 46 years [15-18].
In regard to the supportive periodontal treatment (SPT), the average number of visits per patient was found to be 2.71 over the recorded time. The number of days between the visits varied from 111 days (practice 1) to 755 days (practice 6). The calculated average number of days between visits for all the practices was 307.22 days. Therefore, for all the practices, an average patient visited only once a year. The reasons for this comparable low grade of recall may be multifactorial. One factor could be financial, because health insurance companies in Germany only pay for an extensive subgingival instrumentation once every two years. It is up to the individual patient to pay out of pocket for any further periodontal examination advised by the dentist. Nevertheless, with the introduction of periodontal risk assessment by Lang and Ramseier, intervals can be performed according to this scheme . According to this scheme, the recall interval can be recommended between one and four times a year on an individual basis .
The data showed an increased BOP when the patient attended the first visit and a decreased BOP after periodontal therapy, which is in accordance with previous literature ; .
Furthermore, the data revealed a significant improvement of PDs between the first and last visit, which showed that periodontal treatment was effective in the practices. This effect of periodontal therapy is also indicated in prior scientific literature [22-24]. Thus, this evidence from university settings was confirmed by the present practice-based data.
It was also demonstrated that there was a correlation between BOP and PD. Lower PD values could be found with lower inflammation, which is represented by a lower BOP. This correlation was also found in previous university studies . Regarding the process of PD change, all practices showed significant reductions of PD from the first visit to the last visit, except for practices 3 and 8. There may be different reasons for an increase in PD during periodontal therapy in these practices. However, these factors can only be speculated due to the design of this study. Practice 8 is the practice with the longest recorded data set, and a mild deepening of the pocket depth over the years of SPT was also shown in another study . In this study, after 8 years of SPT, the mean PD increased from 2.9 mm to 3.6 mm after active treatment. In addition, statistical calculations also included values in the healthy range. Thus, PDs of 1 mm might evolve to 3 mm PD without any practical relevance.
It was found that the gingival recessions increased after the therapy relative to the first visit. Subgingival instrumentation often leads to tissue tightening and shrinkage, which is associated with recession formation . Therefore, the measured gingival levels might be higher before therapy compared to after therapy, which is supported by a prior university study .
Molars with furcation involvement in the maxillary could be found in 18.89% of cases at the first visit and 22.02% at the last visit, whereas molars in the mandible could only be found in 12.83% at the first visit and 15.15% at the last visit. This is in line with research by Svärdström and Wennström (1996), which described that molars in the maxilla more frequently showed a furcation than molars of the mandibular . Regarding tooth mobility, a negative correlation was found between mobility and number of visits. Giargia & Lindhe (1997) described in a review that a reduction of periodontal inflammation also resulted in reduced mobility, which was confirmed by the results of this study .
Wisdom teeth in all quadrants showed the highest percentage of tooth loss, followed by the remaining molars and the premolars. Tooth loss in the maxilla was found more often than in the mandibular. Similar findings are published in the scientific literature [30-32].
The main limitations of this study lie in the lack of precise information regarding the performed periodontal therapy. In this context, no further statement could be made regarding the periodontal risk factors and the periodontal diagnosis of the patients. The complexity of periodontal therapy, if subgingival instrumentation was performed with or without any additional surgical procedures, cannot be seen from our data. Furthermore, any adjuvant antibiotic therapy also remains unknown . Beyond that, in some practices, the initial therapy and the supportive periodontal therapy might not be coordinated by the dentist but by dental nurses or dental hygienists. Depending on the level of specialization and experience, a wide variety of treatment outcomes can be expected. Pressure applied when probing the tooth pocket or the probing instrument itself are only a few of the factors that can have an influence of the measurement outcome [34, 35]. Moreover, due to the program's features, only periodontal parameters are collected by default. Plaque indices are possible, but are used by the practices in very different ways (e.g. Quigley Hein Index or Approximal Plaque Index according to Lange). Therefore, the extracted dataset contained no information on plaque.
The collected data reflect the dental treatment situation in Germany. Accordingly, the results may only be comparable to other non-industrialized countries.
The examinations carried out within the framework of the study were not carried out by a single dentist, but by a total of 9 different dentists. On one hand, the participating dentists were not calibrated and did not follow a standardized treatment protocol. However, as strength of the study, all participating practices had a special education in periodontology, as they were all former or active postgraduate students of a master’s degree course in periodontology . The results might be different when data are collected from general dental practices with no specific interest in periodontology or by a single examiner.
Furthermore, the main population is in a special range of age (55.76 years). Should further practices participate in future studies, this will result in an even more representative number with regard to the average age of patients requiring periodontal treatment.
Future projects should try to improve the amount and quality of data recording. The software program should record, in addition to the periodontal data, general health issues and more specific data regarding the therapy (e.g., antibiotics, regenerative treatments, etc.). One fundamental principle of this method should be to not interfere with the daily routine of the practitioner, as dental practices are dependent on economical and efficient processes . The results of this study were mostly positive regarding the applied procedure. Participating practices 1, 2, 3 and 5 found the procedure to be unproblematic, logical, simple and fast.
Furthermore, the lack of standardization in comparison to studies from a research facility must be compensated for by a high number of participating practices. Therefore, the practice-based research network should be extended to improve the data quality and to obtain a representative idea of the periodontal care situation.