Which lower lingual retainer has better periodontal health and stability?

One of the critical and substantial aspect of orthodontic treatment is maintaining the treatment outcomes. There is a higher rate of relapse in the mandibular anterior region and thus requires a long term and fixed retainer to maintain the lower anteriors in position. Various fixed retainer options available for the mandible are lingual bonded retainers with dead soft wires/ stainless steel wires, CAD CAM retainers (Memotain) and connecting pads. But a clear consensus on the best retainer option post-treatment is not available. Also there are very few studies that have correlated the retainers to the periodontal health and stability.

The following article is one such article that has attempted to investigate the effects of different lingual retainers on periodontal health and stability.

“Effects of different lingual retainers on periodontal health and stability”

Adanur-Atmaca R, Çokakoğlu S, Öztürk F. Effects of different lingual retainers on periodontal health and stability. Angle Orthod. 2021 Feb 15. doi: 10.2319/110220-904.1.

What did this paper assess?

This paper evaluated the impact of four different lingual retainers on periodontal health during a 1-year follow-up period and also the stability of treatment outcomes over this period.

What was the protocol?

This was a single-center parallel-design prospective clinical trial with a 1:1 allocation ratio. Before debondoning, the samples were chosen based on the following criteria: (1) non-extraction treatment in the mandible, (2) moderate irregularity before treatment according to Little’s irregularity index, (3) good oral hygiene (absence of visible plaque and redness in the gingiva), and (4) no caries.

Patients were equally randomized to four groups. The study groups were as follows:

  • Group 1: 0.016 3 0.022-in dead-soft wire (Bond-ABraid, Reliance Orthodontic Products, Itasca, Ill, USA)
  • Group 2: 0.0215-in 5-strand stainless steel wire (Pentaflex, GC Orthodontics America Inc, Alsip, Ill, USA)
  • Group 3: 0.014 3 0.014-in computer-aided design/ computer-aided manufacturing (CAD/CAM) nitinol retainer (Memotain, CA-Digital, Mettman, Germany)
  • Group 4: 0.012-in connected bonding pad retainer (Leone SpA, Firenze, Italy)

Random numbers were assigned by the online randomization program to four groups. The numbers were placed in opaque envelopes, and one envelope was selected by each patient.


For the periodontal measurements. plaque, gingival  and calculus  indexes were used. For stability measurements Little’s irregularity index, intercanine width, and arch length measurements

were performed with model analysis software. All measurements were performed at the following time points by the same calibrated investigator (Dr Adanur- Atmaca): debonding session (T0), 3 months (T1), 6 months (T2), 9 months (T3), and 12 months (T4).



What did their results show?

Periodontal measurements – The main plaque index, gingival index and calculus index obtained at T0 was lower than the values obtained at other times. The main effects of the group on the gingival and calculus indices values were statistically significant and the lowest mean value was in group 3.

Stability measurements -  The main effects of group and time on the Little’s irregularity index values found no significant difference between group 1 and group 4, and the highest mean values were obtained in these groups. Similarly, there was no difference between group 2 and group 3, and the lowest mean values were obtained in these groups. The main effect of the group and time interaction on Little’s irregularity index values was statistically significant and the mean values obtained at T0 in group 1 and group 4 were different from the mean values obtained at T2,T3, and T4. The main effects of group, time, and their interactions on mean values of arch length and intercanine width were not statistically significant.


Critical appraisal :

The efforts of the authors to randomise the samples by involving the samples itself is appreciable. At the same time, this was an unblinded trial and the clinician and outcome assessor were both the same person. Thus the reliability of the results is questionable. Also the results were also based on the patient’s ability to maintain the oral hygiene. Considering the design of the retainers, it would have been challenging for the patients of group 4 to maintain oral hygiene as much as their counterparts. Moreover, the follow up protocol of 1 year seems to be very short. Long term evaluation would have been much appreciated. Also patients with moderate irregularity were only considered and thus the periodontal health and stability in a severely irregular arches is still a question.

What we would have liked to know?

Were the patient’s ability and interest in maintaining oral hygiene previously during their treatment period observed and recorded? If yes, were they all equally good enough to be chosen for the trial? What were the difficulties faced by the patients under each group in maintaining oral hygiene?

Conclusion and scope for future studies :

The study showed that the gingival inflammation and calculus accumulation were the least in patients with Memotain retainers. The irregularity in patients with Memotain and stainless steel retainers was less than in the other groups. However, no clinically significant worsening of periodontal health and relapse was seen in any groups after 1 year.

Future studies which assess both the long term effects and the ease of use of the retainers on the periodontal health and stability will give much more clarity on which retainer is to be chosen. Also studies assessing the same on severely irregular arches are required.

Contributors : Dr. Chandnee Shri, Dr. Pamila Rachel.