Effect of Postsurgical Systemic Doxycycline After Regenerative Periodontal Therapy

Patients From April 2007 until February 2009 all patients undergoing periodontal treatment at the Department of Periodontology, Center of Dental, Oral, and Maxillofacial Medicine (Carolinum), Johann Wolfgang Goethe-University Frankfurt/Main and the Section of Periodontology, Department of Conservative Dentistry, Clinic for Oral, Dental and Maxillofacial Diseases, University Hospital Heidelberg are screened for this study. Patients and methods of this study have been described in detail before. Thus only a brief description is provided.

The trial is approved by the Institutional Review Boards for Human Studies of the Medical Faculties of the Johann Wolfgang Goethe-University Frankfurt/Main (159/06) and the University of Heidelberg (ABmu-179/2006) as well as the German Federal Drug Authority (Bundesamt für Arzneimittel und Medizinprodukte). All participating individuals are informed on risks, benefit and the procedures of the study. All give written informed consent. The study is registered under the EudraCT-Nr. 2006-001367-36 and under the number NCT01030666.

Clinical measurements The following clinical parameters are assessed at six sites per tooth (mesiobuccal, midbuccal, distobuccal, distolingual, midlingual, mesiolingual) at baseline, 12, and 24 months after surgery: Gingival Index (GI), Plaque Index (PI), PD and CAL-V to the nearest 0.5 mm using a straight manual periodontal probe (PCPUNC 15, Hu Friedy, Chicago, IL, USA). As reference for the CAL-V measurements, the cemento-enamel junction (CEJ) is used. If the CEJ is destroyed by a restoration the restoration margin (RM) serves as reference.

Radiographic examination Standardized radiographs are obtained of test teeth by modified film holders (VIP 2 Positioning, UpRad Corp., Fort Lauderdale, FL, USA). These are done routinely in the clinical setting, after antiinfective and immediately before surgical treatment. Intraoral size 0 and 2 dental films (Insight, Eastman Kodak Co., Rochester, NY, USA) are exposed using an x-ray source (Heliodent DS, Sirona, Bensheim, Germany) with 7 mA and 60 kVp and developed under standardized conditions (XR24pro, Dürr Dental GmbH, Bietigheim-Bissingen, Germany).

Radiographic evaluation All radiographs are evaluated by one examiner (LR) who is blinded to the clinical results and to the time point the particular radiographs had been taken. All radiographs are digitalized using a computer program (SIDEXIS nextGeneration 1.51, Sirona, Bensheim, Germany) and a flatbed scanner (Microtek ScanMaker 4, Microtek, Hsinchu, Taiwan) with 600 dpi resolution and 8 bit grey values. The image files are stored as TIFF files and analyzed using the above mentioned computer program (SIDEXIS nextGeneration 1.51, Sirona, Bensheim, Germany) and a 19' flat Screen (Totoku CCL 192 plus, Totoku Electric, Ueda, Japan).

For evaluation the analyzing tool of the program (SIDEXIS nextGeneration 1.51, Sirona, Bensheim, Germany) is used. The image files are opened and magnified by using the function "zoom" once. Then the distances CEJ/RM to alveolar crest (AC), CEJ/RM to bony defect (DB), and the depth of the infrabony component (INFRA) are measured. The definition of these radiographic landmarks has been published in detail before.

Microbiological examination Immediately before and 14±2 days after surgery subgingival plaque samples are taken from the test sites of and analyzed by a commercially available real-time PCR test (Meridol Paro Diagnostik, GABA GmbH, Lörrach, Germany) for Aggregatibacter actinomycetemcomitans (A.a.), Porphyromonas gingivalis (P.g.), Tannerella forsythia (T.f.), Treponema denticola (T.d.), Fusobacterium nucleatum (F.n.), and Prevotella intermedia (P.i.). The detection limit of this test is 10².

Periodontal Surgery Infrabony defects reported in this analysis are treated by application of EMD (Emdogain®, Institut Straumann AG, Basel, Switzerland). Before closure of the defect intrasurgical parameters are measured.

Postsurgical Care

All patients take a postsurgical medication once a day for 7 days after regenerative periodontal therapy:

• Test: 200 mg doxycycline
• Control: 200 mg placebo. Doxycycline and placebo are packaged identically and stored in sealed envelopes that were marked with the randomization code. Patients receive doxycycline or placebo after regenerative surgery is accomplished. Patient and clinician are blinded. Block randomization by smoking status (current smoking: smokers/former and never smoking: non smokers) is provided by the manufacturer of the doxycycline (August Wolff GmbH \& Co. Arzneimittel, Bielefeld, Germany).

Further, all patients are advised to rinse with a 0.12 % chlorhexidine gluconate solution (ParoEx, Butler, Kriftel, Germany) for 2 minutes bd for 5 to 7 weeks after surgery. During this time, all patients have to refrain from individual mechanical plaque control and thus are seen every other week for control and gentle cleaning of the teeth. In addition, 400 mg ibuprofen qd is prescribed for patient's comfort if necessary. If soft tissue dehiscence is noted the patient is advised to use a 1 % chlorhexidine gluconate gel (Chlorhexamed 1% Gel, GlaxoSmithKline, Bühl, Germany) twice daily. Sutures are retained as long as they maintained closure.18 Seven to 8 days after surgery wound healing is classified according to the Early Wound-Healing Index (EWI).

Statistical analysis Sample size calculation is based on an observed standard deviation for CAL-V gain (1.6 mm) in a study comparing regenerative therapy with and without antibiotics. To detect a mean difference of 1.0 mm with a test power of 80% and a type 1 error alpha < 0.05 a minimal sample size of 84 patients has to be recruited, 42 for each group. Thus, it is decided to recruit a total of 90 patients.

The patient is defined as statistical unit. CAL-V gain at 6 months is used as primary and bony fill at 12 months as secondary outcome variables. All other parameters are control variables. Baseline patient characteristics are described as means±SD (age, PCR) or frequencies/percentages (sex, smoking). All clinical parameters are calculated as means±SD (PI, GI, PD, CAL-V, INFRA).

After controlling for normal distribution CAL-V gain and PD reduction for the 2 test groups (DOXY/PLAC) are compared using an independent t test. Intragroup comparisons (baseline/12/24 months) are calculated using the paired t test. Inter and intragroup comparisons for radiographic bone, PI and GI are calculated using Mann Whitney U and Wilcoxon test, respectively. To explore the impact of subgingival microflora on the primary and secondary outcome variables we compare CAL-V gain (independent t test) 6 months and bony fill (Mann Whitney U) 12 months after therapy according to presence/absence of the tested periodontal pathogens.

A multiple regression model is calculated for the dependent variable bony fill with the independent variables baseline clinical parameters (CAL-V, PD, GI, PI), postsurgical medication (DOXY/PLAC), defect parameters (INFRA, % 1, 2, 3wall component), baseline A. actinomycetemcomitans, age, sex, centre, smoking, EHI. Sex, centre, and smoking habits are defined by indicator variables. All patients that are recruited and treated according to the study protocol are considered for analysis (intent to treat: ITT). If a patient left the study before finishing all re-examinations the respective data of the last re-examination are entered into the analysis (last observation carried forward: LOCF). Statistical analysis is performed using a PC program (SystatTM for Windows Version 10, Systat Inc. Evanston, IL, USA).