Conical Connection or Internal Hex?

Introduction

Dental implant designs have evolved significantly, focusing on enhancing long-term stability and reducing complications. Among the most widely used internal implant-abutment connections are conical connections and internal hex connections. Understanding their impact on marginal bone loss (MBL), clinical outcomes, and prosthetic complications is essential for optimizing treatment success.

This analysis examines the latest peer-reviewed research on the performance of these two connection types, highlighting key findings from randomized clinical trials (RCTs) and systematic reviews.

Marginal Bone Loss (MBL)

Short-Term Findings

Several studies have evaluated the influence of implant-abutment connection design on early marginal bone loss.

A 12-month randomized pilot study by Galindo-Moreno et al. (2021) reported significant differences in MBL between conical and internal hex connections:

• Conical connections: -0.25 (0.12) mm

• Internal hex connections: -0.70 (0.43) mm

These findings suggest that conical connections may better preserve marginal bone in the short term (Galindo-Moreno et al., 2021).

However, a larger randomized clinical trial by Esposito et al. (2017) found no statistically significant difference in MBL after one year:

• Conical connections: 0.56 ± 0.53 mm

• Internal hex connections: 0.60 ± 0.62 mm (P = 0.745)

This suggests that both connection types perform similarly in terms of MBL over a one-year period (Esposito et al., 2017).

Long-Term Findings

A 60-month follow-up study by Sanda et al. (2019) demonstrated significantly less MBL in the conical connection group:

• Conical connections: 0.96 ± 1.02 mm

• Internal hex connections: 1.30 ± 1.15 mm

These results indicate that, over time, conical connections may be more effective at preserving marginal bone (Sanda et al., 2019).

Clinical Outcomes

Survival Rates

Both conical and internal hex connections exhibit high survival rates. A five-year study by Sanda et al. (2019) reported a 100% survival rate for both connection types, suggesting that implant longevity is not significantly impacted by connection design.

Complications

A three-year follow-up study by Siqueira et al. (2021) found no significant differences between conical and internal hex connections regarding:

• Radiographic marginal bone loss

• Gingival bleeding on probing

• Implant or prosthesis-related complications

These findings indicate that both connection types perform similarly in terms of clinical complications (Siqueira et al., 2021).

Meta-Analysis Findings

A systematic review and meta-analysis by Rodrigues et al. (2023) compared internal conical connections (ICC) with internal non-conical connections (INCC). The analysis revealed:

• Marginal bone loss: ICC showed significantly lower bone loss compared to INCC (Standardized Mean Difference: -0.80 mm; p = 0.004)

• Prosthetic complications: ICC had a lower risk of prosthetic complications (Risk Ratio: 0.16; p = 0.01)

• Implant survival rates: No significant difference was found (Risk Ratio: 0.54; p = 0.10)

• Biological complications: Both connection types showed similar rates (Risk Ratio: 0.90; p = 0.82)

These findings suggest that ICC may offer advantages in terms of lower MBL and reduced prosthetic complications (Rodrigues et al., 2023).

Conclusion

Current research indicates that both conical and internal hex connection implants perform well in clinical settings. However, meta-analysis data suggest that conical connections may offer advantages in terms of lower marginal bone loss and reduced prosthetic complications.

The choice between the two connection types should be based on the specific clinical situation, practitioner preference, and individual patient needs. While conical connections may be preferred due to better peri-implant bone preservation and lower prosthetic complication rates, further long-term studies are needed to determine their superiority in various clinical scenarios.

Sources

1. Esposito M, Salina S, Rigotti F, et al. A comparison of two implants with conical vs internal hex connections: 1-year post-loading results from a multicentre, randomised controlled trial. Eur J Oral Implantol. 2017;10(2):161-168. https://pubmed.ncbi.nlm.nih.gov/28555206
2. Galindo-Moreno P, Concha-Jeronimo A, Lopez-Chaichio L, et al. Marginal Bone Loss around Implants with Internal Hexagonal and Internal Conical Connections: A 12-Month Randomized Pilot Study. Int J Environ Res Public Health. 2021;18(21):11585. https://pmc.ncbi.nlm.nih.gov/articles/PMC8621760/
3. Rodrigues VVM, et al. Is the clinical performance of internal conical connection better than internal non-conical connection for implant-supported restorations? A systematic review with meta-analysis of randomized controlled trials. J Prosthodont. 2023 Apr;32(4):637-648. https://pubmed.ncbi.nlm.nih.gov/36700461/
4. Camps-Font O, et al. Comparison of external, internal flat-to-flat, and conical implant abutment connections for implant-supported prostheses: A systematic review and network meta-analysis of randomized clinical trials. J Prosthet Dent. 2022;128(4):738-748. https://pubmed.ncbi.nlm.nih.gov/34776267/
5. Sanda M, Fueki K, Bari PR, Baba K. Effect of Implant-Abutment Connection Type on Bone Around Dental Implants in Long-Term Observation: Internal Cone Versus Internal Hex. Implant Dent. 2019;28(3):221-224. https://pubmed.ncbi.nlm.nih.gov/31188171/
6. Siqueira RAC, et al. Internal Hexagon vs Conical Implant-Abutment Connections: Evaluation of 3-Year Postloading Outcomes. Int J Prosthodont. 2021;34(1):95-101. https://pubmed.ncbi.nlm.nih.gov/33270835/