Evaluation of factors affecting the success rate of orthodontic mini-implants by survival analysis

Table 1 Mini-implants’ success and failure rates, and ORs statistics by host variables n (%)

Variables	Success	Failure	Total	P-value	OR (95%CI)
Gender				0.231
Male	96 (84.96)	17 (15.04)	113
Female	252 (89.36)	30 (10.64)	282		0.762 (0.354, 1.274)
Jaw				0.019
Maxilla	199 (91.71)	18 (8.29)	217
Mandible	149 (83.71)	29 (16.29)	178		2.152 (1.151, 4.021)
R/L side				0.877
Left	117 (88.50)	23 (11.50)	200
Right	171 (87.69)	24 (12.31)	195		1.080 (0.587, 1.986)
Age				0.973
< 20	106 (87.60)	15 (12.40)	121
20-30	204 (88.31)	27 (11.69)	231		0.935 (0.477, 1.834)
> 30	38 (88.37)	5 (11.63)	43		0.930 (0.316, 2.732)
Gingival tissue				< 0.001
AG	165 (94.29)	10 (5.71)	175			0.367 (0.163, 3.204)
MGJ	109 (85.83)	18 (14.17)	127		2.724 (1.212, 6.124)
MM	73 (79.35)	19 (20.65)	92		4.294 (1.903, 9.689)	1.576 (0.775, 3.204)

Fisher’s exact test. R/L: Right/left; AG: Attached gingiva; MGJ: Mucogingival junction; MM: Mucous membrane.

Table 2 Distribution of mini-implants according to gingival tissue type at the placement site in maxilla and mandible n (%)

	Mandible		Maxilla		P-value
	Total	Failed	Total	Failed
Attached gingiva	34 (19.1)	4 (11.8)	141 (65.3)	6 (4.3)
Mucogingival junction	78 (43.8)	11 (14.1)	49 (22.7)	7 (14.3)	< 0.001
Mucous membrane	66 (37.1)	14 (21.2)	26 (12.0)	5 (19.2)

Table 3 Independent comparison of failure rate between maxilla and mandible according to gingival tissue type n (%)

Variables	Success	Failure	Total	P-value	OR (95%CI)
Attached gingiva				0.105
Maxilla	135 (95.74)	6 (4.26)	141
Mandible	30 (88.24)	4 (11.76)	34		3.000 (0.797, 11.293)
Mucogingival junction				1
Maxilla	42 (85.71)	7 (14.29)	49
Mandible	67 (85.90)	11 (14.10)	78		0.985 (0.354, 2.740)
Mucous membrane				1
Maxilla	21 (80.77)	5 (19.23)	26
Mandible	52 (78.79)	14 (21.21)	66		1.131 (0.362, 3.535)

Table 4 Regression analysis of factors affecting the failure rate of min-implants

	Beta	SE	Wald	P-value	Exp (B)	95%CI of Exp (B)
Gender	0.444	0.124	12.744	< 0.001	1.559	1.222-1.989
Jaw	0.107	0.109	0.956	0.358	1.113	0.898-1.378
R/L Side	-0.031	0.107	0.085	0.771	0.969	0.785-1.196
Age	-0.027	0.084	0.101	0.751	0.974	0.826-1.148
Gingival tissue	0.162	0.069	5.512	0.012	1.176	1.027-1.347

Cox proportional hazard model. Wald: Wald statistic; Exp (B): Exponential of Beta; R/L: Right/left.