Performance and Safety of Smooth-Collar (Tissue-Level) Implants: A Case Report and Clinical Literature Review

The aim of the study is to describe a case series of full-arch rehabilitation of atrophic maxillae using smooth/machined collar (tissue-level) implants, including zygomatic and pterygoid implants, without bone grafting. Four consecutive patients with severe maxillary atrophy underwent clinical and radiographic evaluation, including cone-beam computed tomography, followed by implant placement using standardized surgical protocols. Immediate loading was performed when insertion torque exceeded 45-50 Ncm. Case 1 (65-year-old woman) was treated with four zygomatic, one pterygoid, and one conventional implant. Case 2 (58-year-old woman with controlled systemic conditions) underwent full-arch rehabilitation with conventional and pterygoid implants after tooth extraction. Case 3 (58-year-old woman) received a combination of conventional, zygomatic, and pterygoid implants; one implant was not used due to angulation. Case 4 (58-year-old woman) with an edentulous maxilla was treated with zygomatic, pterygoid, and conventional implants. All cases achieved 100% implant survival during follow-up periods ranging from 10 to 13 months. Prosthetic function remained stable in all patients, with no biological or mechanical complications reported. Smooth-collar (tissue-level) implants demonstrated predictable short-term outcomes in the rehabilitation of severely atrophic maxillae, including anatomically challenging regions such as zygomatic and pterygoid areas. Further studies with larger samples and longer follow-up are needed to confirm these findings. A systematic review was also conducted following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines to evaluate the performance and safety of dental implants with a smooth/machined collar (tissue-level), with a particular focus on complex maxillary rehabilitations using zygomatic and pterygoid implants. Searches were performed in PubMed, SciELO, BVS, and Google Scholar for articles published between January 1, 2010, and January 28, 2025. Eligible studies included prospective and retrospective clinical trials, case series, and systematic reviews evaluating implants with a machined collar height > 3 mm in edentulous patients. Key outcomes assessed were implant survival rate, marginal bone loss, biofilm control, and incidence of complications.