# Retrospective Study Regarding Orthodontic Retention Complications in Clinical Practice
## 2 Material and Method  
The Rustogi Modification of the Navy Plaque Index (RMNPI) [21] has been proved a very high precision in determining the dental hygiene status because of the detailed examination of the vestibular and oral surfaces of the teeth, divided into nine areas, 18 in total. The score is 0 if the bacterial plaque is not present; if BP exists, the score of the affected area is denoted by 1. The index per tooth = sum of all areas marked with 1. The third molars are not in the calculation. The index value is determined by dividing the sum of the indices calculated for every present tooth by the number of teeth. The value of RMNPI could be between 0 and 1, 0 signifying excellent dental hygiene, and 1 a lack of hygiene. Turesky Modified Quigley-Hein Plaque Index (TMQHPI) is very sensitive to changes in dental hygiene [22]. To determine this index all the present teeth except the third molars are taken into account. The presence of bacterial plaque is determined by the examination of the vestibular and oral surfaces of the teeth, so the maximum number of investigated surfaces will be 56. The amount of bacterial plaque (BP) will be quantified as follows: 0 = absence of BP; 1 = BP as a discontinuous line at the gingival margin; 2 = BP as a continuous line less than 1 mm width at the cervical level; 3 = continuous BP greater than 1 mm in width but not reaching 1/3 of the surface; 4 = BP covering between 1/3 and 2/3 of the surface; 5 = BP surpassing more than 2/3 of the surface [22]. The average TMQHPI will be the total number of points for each tooth/total number of examined areas Index interpretation: <0-1--excellent hygiene; <1-2--good hygiene; <2-3--moderate hygiene; <3-4--poor hygiene; <4-5--absent hygiene. We chose to use these two indices in determining the dental plaque because they are easy to evaluate, and their accuracy is high [21,22]. The recessions were determined on all the teeth included in retention systems as the shortest distance from the cementoenamel junction to the deepest curvature of the gingival margin by using a standard periodontal probe. Our study included a group of 116 patients aged between 18.3 and 27.6 years, with a mean age of 23.8. The patients were from our town, Targu Mures, and its surroundings. The inclusion criteria were as follows:  
* the absence of gingival recessions before the orthodontic treatment;
* fixed orthodontic appliance placed for at least one year;
* patients who wearing a fixed or mobile restraint device at the time of the examination;
* fixed retentions performed with multistranded wires. The balanced study group consisted of 45 men (38.79% of the total) and 71 women (61.21% of the total). The selected patients were asked to complete an 11-question questionnaire regarding their oral health status (Appendix A). The questionnaire aims to investigate the oral hygiene habits, to collect information about the retention type and the compliance of the patients wearing them. The questionnaire was designed according to our clinical experience and theoretical knowledge. After the patient filled up the questionnaire, we performed the clinical examination using the dental mirrors, the Williams periodontal probes, and the plaque-revealing tablets. During the clinical examination the following indices were determined:  
* the Quigley-Hein plate index modified by [PERSON]
* the Navy plaque index was modified by [PERSON]. For determining the RMNPI we used the following strategy: the gumline areas were divided into subgroups A, B, C, and the interproximal tooth areas were assigned to subgroups D, F.  
Based on a comprehensive study of the state-of-the-art power analysis research [23, 24, 25] and the supposed data distribution on other similar research (verified after we have already obtained the data) we established 100 as a minimal sample size. Finally, we have performed the study on a sample of 116 in case some data fail to pass the quality assessments (missing data, for instance).