Materials & methods : Study of implants (3)|palmerah.implantgigi.com

Mucositis was determined using either the “strict” criteria, IMI ≥1, as an indication for mucositis or the “relaxed” criteria, IMI ≥2, as an indication of mucositis. We defined peri‐implantitis as the combination of mucositis and MBL ≥1.0 mm, at least 1 year after installation.

2.1 Statistical analysis

CBL and MBL are scale variables and have been summarized by calculating the mean and median as central tendency statistics and the standard deviation, range and percentiles, as dispersion statistics. Linear mixed models were used in order to evaluate CBL as the main outcome variable as a function of time as well as the other explanatory variables. The results from the final model (Table 1) allowed us to test three null hypotheses (H₀): 1) Mean crestal bone level is equal at start, 2) Mean crestal bone level over time (profile) is equal, and 3) No interaction between bone level and time exist. See supplementary text in online Journal of Periodontology for further details and for patient level analysis.

Table 1. Explanatory variables having a statistically significant effect on mean crestal bone level over time

		P value
Level	Variable	Difference at start(*)	Main effect(†)	Significant interaction with time(‡)
Patient	Autoimmune	0.21	0.04	No
	Smoking	0.92	<0.01	Yes
	Bisphosphonate	0.04	0.045	No
Implant	Location	<0.01(§)	<0.01	Yes
	Diameter	<0.01	<0.01	Yes
	Implant design	<0.01(‖)	<0.01	No
	Immediate loading	<0.01	<0.01	No
	Bone defect	<0.01	<0.01	yes

NB: The numbers in the column “Difference at start” are the P values testing the null hypothesis (H0) which states that bone level is equal at the start (actually at stage 2 = 3 months) for different categories within a variable. The P values in the “Main effect” column indicate whether bone levels over time are different between categories of a variable (i.e.: differences in mean bone loss over the time points recorded). The column “Significant interaction with time” refers to a comparison of slopes between categories of a given variable.
^*H₀: Mean crestal bone level is equal at start.
^†H₀: Mean crestal bone level over time (profile) is equal.
^‡H₀: There is no interaction between bone loss and time (the rate of bone loss is constant over time).
^§The difference between posterior maxilla and posterior mandible is non‐significant.
^‖The difference between standard and standard plus, and between bone level and tapered is non‐significant.

In order to calculate the prevalence of mucositis and peri‐implantitis at the implant level, mucositis (as either IMI ≥1 or IMI ≥2) and MBL ≥1 mm were cross‐tabulated at 2 to 3 years, 4 to 5 years, 6 to 7 years, and 8 to 10 years.

The statistical analysis was performed with SPSS and with R software. The significance level was set to 0.01.

Materials & methods : Study of implants (3)

2.1 Statistical analysis

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