Narrow Implants Held Up. The Screws Complained.
A retrospective split-mouth comparison of 100 implants found narrow-diameter internal-hex implants matched standard implants for survival and marginal bone over 4.2 years, while also carrying the only recorded technical complications.
Narrow implants held up
Source Paper
Clinical Performance of Narrow Versus Standard Diameter Dental Implants: A Comparative Retrospective Split-Mouth Study
Most of us have a private little calculus for narrow implants. We say “anatomical limitation” out loud and think “please let me avoid a graft, more surgery, and a mesiodistal-space conversation” in our heads. Raz and colleagues, in “Clinical Performance of Narrow Versus Standard Diameter Dental Implants: A Comparative Retrospective Split-Mouth Study,” make that calculation rather less mystical: over a mean 4.2 ± 0.8 years, narrow implants matched standard implants for survival and marginal bone loss, while the only real grumbling came from the screws.
That is a useful result because implant diameter is one of those topics where theory likes to dress up as destiny. Wider implants should distribute load better; narrower ones should therefore make everyone nervous. Sometimes they do. But not always, and not in every site where the ridge has no intention of accommodating textbook optimism.
The Data Anchor
This retrospective analysis included 100 MIS implants with internal hex connections placed in 43 patients: 50 narrow-diameter implants (3.3 mm) and 50 standard-diameter implants (3.75-4.2 mm). The system used MIS LANCE and SEVEN fixtures, all placed in healed extraction sites, and the study only included patients with at least 3 years of follow-up after loading. Mean follow-up landed at 4.2 ± 0.8 years.
The authors did not restrict themselves to one tidy clinical arrangement. They compared implants in homologous split-mouth positions, in different arches, and within the same arch or segment, including both splinted and non-splinted restorations. Marginal bone loss was measured on periapical radiographs. Survival was the primary outcome. Technical complications, sensibly enough, were not treated as an afterthought.
Key Findings
- Survival was identical, and boring in the best possible way. There were no implant failures in either group, which dampens any urge to declare the 3.3 mm implant biologically doomed.
- Bone levels were effectively the same. Mean marginal bone loss was 0.83 mm for narrow implants and 0.87 mm for standard implants, with no statistically significant difference between the groups.
- The anatomy did not produce a hidden ambush. The study also found no significant marginal bone loss difference by jaw, implant location, or splinted versus non-splinted design, which strengthens the sense that diameter alone was not running the show.
- The technical complications all lived on the narrow side. One abutment screw fracture (2%) and two cases of abutment screw loosening (4%) were recorded, and all of them occurred in the narrow-implant group.
- The practical indication remains intact. In cases of limited ridge width or restricted interdental space, the paper supports narrow implants as a way to avoid extra augmentation without obviously sacrificing medium-term biologic performance.
- The caveat is the usual one for retrospective implant papers. This was a 43-patient study with relatively few adverse events, so it is strong enough to calm the diameter panic, but not strong enough to declare prosthetic risk irrelevant.
💡 The Clinical Bottom Line
If you are choosing a narrow implant because the site genuinely asks for one, this paper is reassuring. A 3.3 mm internal-hex implant did not shed more bone or fail more often than a standard-diameter implant in this cohort, which is the sort of information clinicians need when the ridge and the restorative envelope are having one of their regular domestic disagreements.
What it does not let us do is become casual about the prosthetics. The biologic story here is calm; the mechanical story is merely calmer than some feared. Narrow implants may be perfectly respectable citizens, but they still prefer a well-managed occlusal environment and hardware that is not asked to perform miracles after lunch.
Dr Samuel Rosehill is a general dentist with a prosthodontic focus, practising at Ethical Dental in Coffs Harbour, NSW. He holds a BDSc (Hons) from the University of Queensland, an MBA, an MMktg, and an MClinDent in Fixed & Removable Prosthodontics (Distinction) from King’s College London.
Clinical Relevance
When ridge width or interdental space is tight, a 3.3 mm internal-hex implant looks like a defensible option rather than a heroic compromise. This study suggests bone response and survival can match standard-diameter implants over medium-term follow-up, but the prosthetic mechanics still deserve closer attention.
Disclosure: The author has no financial conflicts of interest related to the products or topics discussed in this review. This is an independent summary prepared for educational purposes.
Continue the conversation
This review is also published on Substack, where you can leave comments and join the discussion.
Read on Substack →