Long-term clinical performance of short 6-mm implants supporting single crowns in the posterior region: A 10-year cohort study

INTRODUCTION

Long-term clinical success of non-splinted, posterior, and short implants still is unclear. This prospective cohort study reports the 10-year follow-up of 6-mm implants supporting single crowns in the posterior region, and patient-reported outcomes.

METHODS

Baseline sample comprised 20 patients treated with 46 screw-retained crowns supported by 6-mm implants with moderately rough implant surface. Participants were recalled for a 10-year clinical follow-up to assess survival rates, biologic and mechanic conditions, quality of life (OHIP-14), and treatment satisfaction. Data were collected with clinical-radiographic exams and analyzed using descriptive and inferential statistics.

RESULTS

Fourteen patients with 35 implant-crown units were examined after 127.6 ± 11.8 months. For the entire cohort period, 7/46 implants were lost (survival estimate: 77.7% at 133 months), and mechanic complications occurred in 14/46 units (survival estimate: 66.4% at 116 months). In the Cox models, "maximum occlusal force" had a significant effect for implant loss (p = 0.038) and for prosthetic screw loosening (p = 0.038); "arch" and "bruxism" were not significant. Peri-implant bone loss was 0.4 ± 0.6 mm at 10 years. For peri-implant bone level, "crown-to-implant ratio" (p < 0.001) and "time" (p = 0.001) were significant. Bone levels differed from baseline to 12, 48, and 120 months. Satisfaction VAS was 94.0 ± 7.9 mm and OHIP-14 was 2.3 ± 2.2.

CONCLUSION

Single screw-retained crowns supported by 6-mm implants have an acceptable long-term clinical performance, with stable peri-implant bone levels after 10 years of function.

Relation between insertion torque and tactile, visual, and rescaled gray value measures of bone quality: a cross-sectional clinical study with short implants

Background

This study assessed the relationship between insertion torque and bone quality evaluated during surgery and in preoperative computed tomographic (CT) images analyzed either visually or by rescaled mean gray values (MGVs). The study also tested the correlation between the clinical and radiographic measures of bone quality.

Methods

The consecutive sample was composed of 45 short implants (4.1 × 6 mm) placed in the posterior region of 20 patients. Intra-surgical tactile bone quality, based on the classification of bone types by Lekholm and Zarb, and insertion torque were recorded during the implant placement. Visual bone quality and normalized MGV were assessed in standardized axial, coronal, and sagittal sections of preoperative CT images. Data were analyzed by ANOVA and Spearman correlation (alpha = 0.05).

Results

Insertion torque was associated with all assessment methods of bone quality (tactile, CT visual, MGV). A moderate correlation was found among all methods of bone quality, except for CT visual assessment and tactile evaluation. MGVs varied as a function of arch, dental region, insertion torque, and bone types.

Conclusions

The results suggest that bone quality measures affect primary stability as recorded by insertion torque, and the assessment methods are consistently related.