The effectiveness of Hawley and vacuum-formed retainer usage protocols on the stability of fixed orthodontic treatment results

Comparisons of gender and age at debonding, molar relationships and ANB° before orthodontic treatment, and changes in arch dimensions with active orthodontic treatment between the groups.

		Group 1	Group 2	Group 3	Group 4	p-value
		N (%), median (min, max) or mean ± SD)	N (%), median (min, max) or mean ± SD)	N (%), median (min, max) or mean ± SD)	N (%), median (min, max) or mean ± SD)	p-value
Gender	Female	12 (100%)	5 (41.7%)	11 (84.6%)	10 (66.7%)	0.009^{^*,^a}
Gender	Male	0 (0%)	7 (58.3%)	2 (15.4%)	5 (33.3%)	0.009^{^*,^a}
Molar relationship	Class I	9 (75%)	9 (75%)	8 (61.5%)	7 (46.7%)	0.198^{^a}
	End-to-end	3 (25%)	2 (16.7%)	3 (23.1%)	8 (53.3%)
	Class II	0 (0%)	1 (8.3%)	2 (15.4%)	0 (0%)
Age (years)		16.15 (14.1, 19.9)	16.1 (14.1, 18)	17 (15.3, 19.1)	17.25 (14, 23)	0.162^{^b}
ANB°		3.15° (0.7°, 4.2°)	4.9° (1.6, 5.7)	3.8 (1, 5.1)	3 (0.9, 7)	0.113^{^b}
Little (mm) (T1-T0)	Maxilla	-7.86 (-14.98,-4.62)	-8.97 (-14.6,-2.9)	-8.05 (-13.14,-3.09)	-8.21 (-16.8, -6.13)	0.885^{^b}
Little (mm) (T1-T0)	Mandible	-6.58±2.43	-6.81±3.08	-8.25±3.40	-7.40±3.08	0.521^{^c}
Intercanine width (mm) (T1-T0)	Maxilla	0.52 (-4.13, 5.33)	0.51 (-4.42,6.98)	1.54 (-1.75, 2.74)	0.78 (-2.45, 4.27)	0.957^{^b}
Intercanine width (mm) (T1-T0)	Mandible	0.44±1.20	1.07±1.67	1.11±1.66	0.97±1.21	0.640^{^c}
Intermolar width (mm) (T1-T0)	Maxilla	0.18 (-2.73, 4.6)	1.73 (-1.5, 4.6)	0.99 (-0.71, 6.32)	0.12 (-1.01, 5.4)	0.175^{^b}
Intermolar width (mm) (T1-T0)	Mandible	-0.01±1.60	1.96±1.65	0.24±1.83	1.32±2.44	0.051^{^c}
Arch length (mm) (T1-T0)	Maxilla	2.08±2.10	1.90±2.65	2.12±3.16	2.31±2.96	0.986^{^c}
Arch length (mm) (T1-T0)	Mandible	2.64±1.89	2.81±4.71	2.14±3.64	3.61±3.26	0.732^{^c}
Overjet (mm) (T1-T0)		-0.73±1.24	-0.63±1.24	-0.27±1.35	-1.03±1.12	0.456^{^c}
Overbite (mm) (T1-T0)		-0.66±1.13	-1.53±1.27	-1.00±1.38	-1.29±1.27	0.372^{^c}

1a chi-square test was applied.

2b Kruskal-Wallis test was applied.

3c One Way Analysis of Variance (ANOVA) was applied.

4* p < 0.05 was accepted as statistically significant.

Table II.

Arch measurements at debonding (T1), after six month full-time retention (T2), measurement changes from T1 to T2, comparisons of the changes between Hawley and vacuum-formed retainer groups.

		HAWLEY (N=26)			P	VACUUM-FORMED RETAINER (N=32)			P	Intergroup comparison P
		T1 Mean ± SD or median (min, max)	T2 Mean ± SD or median (min, max)	T2-T1 Mean ± SD or median (min, max)	P	T1 Mean ± SD or median (min, max)	T2 Mean ± SD or median (min, max)	T2-T1 Mean ± SD or median (min, max)	P
Maxilla	Little (mm)	0 (0,0)	0.44 (0, 2.08)	0.44 (0, 2.08)	<0.001^{^****,^a}	0 (0,0)	0.05 (0, 2.3)	0.05 (0, 2.3)	<0.001^{^****,^a}	0.225^{^c}
	Intercanine width (mm)	36±2.17	36.16±2.14	0.17±0.72	0.253^{^b}	35.07 (31.9, 38.08)	34.94 (31.56, 38.86)	0 (-2.78, 0.78)	0.414^{^a}	0.081^{^c}
	Intermolar width (mm)	51.29 (43.69, 59.20)	51.83 (45.10, 59.28)	0.32 (-0.57, 1.82)	<0.001^{^****,^a}	51.12 (45.75, 58.06)	51.31 (44.82, 58.06)	0 (-1.65, 1.25)	0.679^{^a}	<0.001^{^****,^c}
	Arch Length (mm)	71.83±4.00	71.91±3.96	0.77±0.90	0.663^{^b}	70.00 (62.76, 78.30)	70.18 (62.8, 77.8)	0.01 (-1.8, 3.26)	0.940^{^a}	0.969^{^c}
Mandible	Little (mm)	0 (0,0)	0.46 (0, 2.64)	0.46 (0, 2.64)	<0.001^{^****,^a}	0 (0, 1.36)	0.39 (0, 1.79)	0.37 (0, 1.61)	<0.001^{^****,^a}	0.703^{^c}
	Intercanine width (mm)	27.53±1.76	27.52±1.72	-0.02±0.52	0.884^{^b}	26.85±1.41	27.02±1.42	0.16±0.43	0.039^{^*,^b}	0.156^{^d}
	Intermolar width (mm)	44.64±2.69	44.88±2.62	0.24±0.61	0.057^{^b}	44.76 (38.45, 52.05)	44.62 (38.88, 52.05)	0.04 (-1.11, 1.90)	0.204^{^a}	0.334^{^c}
	Arch Length (mm)	61.93±3.61	61.70±3.83	-0.23±0.90	0.204^{^b}	61.29 (52.88, 66.74)	60.77 (52.88, 66.17)	0.10 (-1.74, 5.79)	0.926^{^a}	0.260^{^c}
Inter-arch	Overjet (mm)	2.27±0.88	2.30±0.73	0.04±0.63	0.776^{^b}	2.16±0.72	2.18±0.72	0.02±0.48	0.825^{^b}	0.910^{^d}
	Overbite (mm)	2.36±0.73	2.59±0.76	0.23±0.56	0.047^{^*,^b}	2.48±0.71	2.79±0.65	0.31±0.49	0.001^{^***,^b}	0.571^{^d}

1a Wilcoxon Signed Rank test was applied.

2b Paired t-test was applied.

3c Mann Whitney-U test was applied.

4d Independent samples t-test was applied.

5* p < 0.05 was accepted as statistically significant.

6*** p = 0.001

7**** p < 0.001

Table III.

Intragroup and intergroup arch measurement changes occurred from debonding (T1) to 12th month (T3), and from sixth (T2) to 12th month (T3 of retention, and their significances.

		Maxilla				Mandible				Inter-arch
		Little (mm) (mean±SD)	Intercanine width (mm) (mean±SD)	Intermolar width (mm) (mean±SD)	Arch length (mm) (mean±SD)	Little (mm) (mean±SD)	Intercanine width (mm) (mean±SD)	Intermolar width (mm) (mean±SD)	Arch Length (mm) (mean±SD)	Overjet (mm) (mean±SD)	Overbite (mm) (mean±SD)
Group 1 (N=12)	T3-T2	0.30±0.27	0.03±0.30	0.01±0.18	0.03±0.43	0.31±0.45	-0.05±0.20	0.04±0.11	0.17±0.84	-0.18±0.49	0.02±0.41
	P	0.172^{^a}	1.000^{^a}	1.000^{^a}	1.000^{^a}	0.212^{^a}	1.000^{^a}	1.000^{^a}	1.000^{^a}	0.482^{^a}	1.000^{^a}
	T3-T1	1.02±0.84	0.91±0.64	0.71±0.61	0.15±0.69	1.10±0.92	-0.14±0.51	0.45±0.58	-0.18±0.95	0.08±0.63	0.35±0.47
	P	<0.001^{^****,^a}	1.000^{^a}	0.001^{^***,^a}	1.000^{^a}	<0.001^{^****,^a}	1.000^{^a}	0.347^{^a}	1.000^{^a}	1.000^{^a}	0.121^{^a}
Group 2 (N=12)	T3-T2	0.41±0.43	-0.38±0.58	0.03±0.46	-0.12±0.5	0.80±0.58	-0.08±0.31	0.08±0.40	-0.25±0.62	-0.10±0.42	0.14±0.39
	P	0.028^{^*,^a}	0.178^{^a}	1.000^{^a}	1.000^{^a}	<0.001^{^****,^a}	1.000^{^a}	1.000^{^a}	0.890^{^a}	1.000^{^a}	0.884^{^a}
	T3-T1	0.81±0.76	-0.17±0.84	0.25±0.73	-0.11±1.05	1.17±0.79	-0.11±0.61	0.09±0.79	-0.30±0.82	-0.36±0.90	0.23±0.58
	P	0.001^{^***,^a}	1.000^{^a}	0.569^{^a}	1.000^{^a}	<0.001^{^****,^a}	1.000^{^a}	1.000^{^a}	1.000^{^a}	0.213^{^a}	0.557^{^a}
Group 3 (N=13)	T3-T2	0.23±0.66	0.39±0.94	0.51±1.00	0.44±0.88	0.27±0.37	-0.17±0.59	0.46±0.95	0.11±0.95	-0.30±0.54	-0.24±0.50
	P	0.371^{^a}	0.134^{^a}	0.010^{^**,^a}	0.024^{^*,^a}	0.287^{^a}	0.409^{^a}	0.027^{^*,^a}	1.000^{^a}	0.048^{^*,^a}	0.172^{^a}
	T3-T1	0.62±0.55	0.21±0.60	0.36±0.71	0.44±1.69	0.91±0.66	0.19±0.76	0.82±1.42	0.60±2.45	-0.32±0.53	0.15±0.60
	P	0.010^{^**,^a}	0.919^{^a}	0.165	0.579	0.001^{^***,^a}	0.805^{^a}	0.011^{^*,^a}	0.519^{^a}	0.289	1.000^{^a}
Group 4 (N=15)	T3-T2	0.34±0.62	0.36±0.71	0.14±0.42	0.00±0.37	0.59±0.77	0.06±0.42	0.34±0.62	-0.05±0.83	0.12±0.29	-0.04±0.45
	P	0.048*^{,^a}	1.000^{^a}	1.000^{^a}	1.000^{^a}	0.001^{^***,^a}	1.000^{^a}	0.120^{^a}	1.000^{^a}	0.936^{^a}	1.000^{^a}
	T3-T1	0.76±0.73	-0.03±0.80	0.18±0.55	0.20±1.09	1.10±0.91	0.07±0.50	0.25±0.86	-0.25±1.38	0.19±0.59	0.22±0.64
	P	0.001^{^***,^a}	1.000^{^a}	0.890^{^a}	1.000^{^a}	<0.001^{^****,^a}	1.000^{^a}	0.945^{^a}	1.000^{^a}	0.852^{^a}	0.453^{^a}
Intergroup comparison (p-value)	T3-T2	0.897^{^b}	0.016^{^,^b} (2-3; p=0.008^{^*})	0.286^{^b}	0.306^{^d}	0.119^{^b}	0.651^{^b}	0.298^{^b}	0.494^{^b}	0.092^{^c}	0.206^{^c}
	T3-T1	0.604^{^c}	0.599^{^c}	0.196^{^c}	0.399^{^b}	0.875^{^c}	0.481^{^c}	0.575^{^b}	0.727^{^b}	0.076^{^b}	0.527^{^b}

1a Repeated measure ANOVA with one fixed factor was used to detect significant differences. Bonferroni adjustment was done for multiple comparisons.

2b Kruskal Wallis test was applied. Dunn’s correction was performed for subgroup analysis, when significant difference was found.

3c One-way ANOVA was used to detect significant differences, with Bonferroni correction.

4d Welch heteroscedastic F-test was applied.

5* p < 0.05 was accepted statistically significant.

6** p = 0.01

7*** p = 0.001

8**** p < 0.001

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DOI: https://doi.org/10.21307/aoj-2021-007 | Journal eISSN: 2207-7480 | Journal ISSN: 2207-7472

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Language: English

Page range: 69 - 78

Published on: Jul 13, 2021

Published by: Australian Society of Orthodontists Inc.

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© 2021 Hande Gorucu-Coskuner, Ezgi Atik, Tülin Taner, published by Australian Society of Orthodontists Inc.
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Volume 37 (2021): Issue 1 (January 2021)