The Relationship between the Implant Angulation and the Labial Soft-Tissue Thickness

 

Statement of the problem:A minimum thickness (1.8 mm) of surrounding bone is needed for a successful placement of implant (1); otherwise, leading to a thin gingival biotype and gingival recession. Implant position and angulation are important and to avoid complications, palatally and apically placement of implants has been suggested (2). The objective of this study was to assess the relationship between the Labial Soft-Tissue Thickness (LSTT) and the angulations of implants.

Materials and methods:32 patients (22 female and 10 male) participated in this retrospective study and had two implants placed in their maxillary arch, between the canines at either maxillary lateral incisor (#7 & 10), or central incisor (# 8 & 9) regions. Overall, 64 implants (20 Astra, 18 Strauman, 12 BHZ, 6 Zimmer, 6 Biomet, and 2 Lifecore implants) were placed. Implant diameters ranged from 3.3 to 4.6 mm. The implant position was determined using the cone beam CT scan (Picasso Duo, VATech). All patients had diagnostic (pre) and post-op cone beam CT scans. Using the cone beam CT scans, the labial bone thickness at the crest and mid-implant level were measured and recorded. The Labial Soft-Tissue Thickness (LSTT) was measured using a Mitutoyo digital caliper at the crest level. The measurements of LSTT were performed approximately 4 months after placement of implants. Implant angulation was classified by the screw position and was recorded as cingulum, incisal, or labial position, based on the screw-access hole on the provisional restoration.

Methods of data analysis:Data for the covering LSTT were gender compared (independent t-test), and for implants with different angulations exposed to descriptive analysis and the one-way analysis of variance (ANOVA). LSTT recordings for 3 implant angulation groups were exposed to the test of homogeneity of variances (Levene statistic) before performing the one-ways ANOVA test. Multiple comparison of labial soft-tissue thicknesses in 3 implant angulation groups were performed using the Post Hoc tests and Bonferroni corrections.    

 

Results:The independent t-test revealed no significant gender difference for the LSTT (2.46±0.88 and 2.43±0.90 mm for female and male patients, respectively).  Considering the screw position, there were 29, 20 and 15 implants with cingulum, incisal, and labial angulations, respectively. The mean LSTT for implants with cingulum, incisal, and labial angulations were 2.98 (0.84), 2.24 (0.51), and 1.71 (0.72) mm, respectively. The one-ways ANOVA test revealed significant differences in labial soft-tissue thicknesses between 3 implant angulation groups (F=16.67, p=0.000). Table 1 shows the multiple comparisons of labial soft-tissue thicknesses in 3 implant angulation groups. There were statistically significant differences between the LSTT of implants with cingulum and incisal as well as cingulum and labial angulations.

Table 1-The multiple comparisons of the labial soft-tissue thicknesses for 3 implant angulation groups.

 

Implant angulation		Mean Diff. (mm)	P value	95% CI
Group I	Group II
Incisal	Labial	0.53	0.105	-0.07-1.14
Cingulum	Labial	1.27	0.000	0.71-1.84
Cingulum	Incisal	0.74	0.002	0.23-1.26

 

Conclusion:Implants with incisal and labial angulations were associated with thinner labial soft-tissue thicknesses and possibly carry a higher risk of developing soft-tissue complications (i.e., gingival recessions).

References:

1-Spray JR, Black CG, Morris HF, Ochi S. The influence of bone thickness on facial marginal bone response: stage 1 placement through stage 2 uncovering. Ann Periodontol. 2000;5:119-28.

2-Fu JH, Lee A, Wang HL. Influence of tissue biotype on implant esthetics. Int J Oral Maxillofac Implants. 2011;26:499-508.