ARTICLE DISCUSSION

  A comparative study between the effect of reverse curve of spee archwires and anterior bite turbos in the treatment of deep overbite cases: A randomized clinical trial

Ekram M. Al-Zoubia; Kazem S. Al-Nimrib

 

What did the authors aim to do in this study?

The primary purpose of this study was to compare the two different methods of deep overbite treatment, a) Using 0.016 x 0.022 Niti lower reverse curve of spee archwire [LRCA], b) Using metal anterior bite turbos [ABTs].

 

How did the authors evaluate?

The study was conducted on forty eight patients with deep overbite malocclusion and they were randomly allocated into two groups. The first group (GROUP I) was treated with LRCA, while the second group (GROUP II) was treated with ABTs bonded to the palatal surface of the upper central incisors. Both the groups were followed up monthly until an average overbite was achieved. Two cephalograms were taken for each patient, at post-alignment stage (T1) and post-leveling stage (T2). The authors assessed the effect of both the treatment methods by studying the changes in the inclination of lower incisors and angular and vertical changes of lower incisors, premolars & molars which was the primary outcome. The secondary outcomes they analysed were the assessment of saggital and vertical changes, to measure the change in the inclination of upper incisors and the vertical changes of upper posterior and anterior teeth, and to compare the treatment duration between the two treatment modalities. 

To analyze the primary outcomes, Thirty six hard tissue and dental landmarks were identified and angular measurements were obtained on each cephalogram. To measure the linear dental changes in the mandibular and maxillary teeth, a horizontal reference line(HRL) was determined at T1(drawn from Sella, 7° below the SN line) and a perpendicular line to the HRL passing through Sella formed the vertical reference line (VRL). 

To measure the changes in the mandibular dentition, T1 & T2 lateral cephalometric radiographs were superimposed on the corpus axis at protuberance menti (Pm). The change in the position of the lower incisor tip horizontally was determined by drawing perpendicular lines from the lower incisor tips at T1 & T2 to HRL; the linear distance between these two lines measured at the HRL determined the anterioposterior change in the position of the lower incisors. To determine the change in the vertical position of the lower posterior teeth and lower incisor edge, perpendicular lines from each cusp tip at T1 & T2 were drawn to VRL and the linear distance between the two lines was measured at the VRL. The true vertical movement of the lower incisors was determined by measuring the length of the post-alignment (T1) incisor, then this length was multiplied by 0.66 to determine the position of Point I along the long axis of the tooth, two-thirds of its length from the incisal edge. This measurement was then carried out using a transfer line with the same length on the T1 lateral cephalogram and the point was then relocated on the T2 lateral cephalogram. Then the perpendicular lines from these points were drawn to the VRL and the linear distance between the two lines was measured at the VRL to determine the true lower incisor vertical change. 

While analysing the secondary outcomes, the maxillary dental changes, T1 & T2 lateral cephalograms were superimposed according to the Bolton template of maxillary superimposition by using the anterior palatal contour. The same was used to determine the change of the vertical and horizontal position of the upper incisor tip and to determine the change in the vertical position of the upper first molar and premolars. The anterior lower facial height ratio (LFH) was measured as the distance between the anterior nasal spine and menton, divided by the distance between nasion and menton.

Paired t-test and one sample t-test were used to determine the significance of the treatment changes within each group. Independent t-tests were used to determine differences in the cephalometric measurements between the two groups.

 

What did the authors find?

By the end of T2 stage, the lower incisors were found to be more proclined in Group I. Both lower second molars and the lower first molars were found to be tipped more distally, while the lower first premolars were found to have tipped more mesially in Group I. All the cusps of both the lower molars showed more extrusion in Group II, except for the mesial cusp of lower second molars. The duration of overbite correction was shorter using the ABTs by 1.7 months.

 

What did the authors conclude?

·      Both 0.016 x 0.022 NiTi LRCA and ABTs were effective in deep overbite correction.

·      Lower incisors in cases treated with 0.016 x 0.022 NiTi RCA demonstrated more proclination than cases treated with ABTs.

·      1 mm of absolute intrusion of the lower incisor was noted in cases treated with 0.016 x 0.022 NiTi RCA compared to 0.28 mm in cases treated with ABTs.

·      Lower first and second molars showed significant distal tipping when the overbite was corrected using 0.016 x 0.022 NiTi RCA.

·      Greater lower posterior tooth extrusion and a greater increase in the lower facial height ratio were noted in cases treated with ABTs than cases treated with 0.016 x 0.022 NiTi RCA.

·     The duration of the overbite correction stage of treatment was shorter when ABTs were used to treat cases with deep overbite.