Standard dental implants require sufficient bone and spacing, which may not be available in all patients. To address these limitations, narrow diameter implants (≤3.5 mm) have been introduced as a less invasive alternative, especially useful for medically compromised patients or those avoiding bone grafts. However, narrow implants made of pure titanium have shown long-term biological and technical concerns.
The introduction of titanium-zirconium (TiZr) alloy has improved mechanical strength, and several studies have demonstrated favorable outcomes with narrow TiZr implants. Yet, evidence remains limited regarding their exclusive use in high-load posterior (molar) regions. Prior studies report conflicting failure rates, potentially linked to prosthetic design and occlusal forces, but lack quantitative analysis of bite forces or prosthetic angles.
Emergence angle, prosthetic platform width, and implant-abutment connection may all influence implant stability and peri-implant tissue health. A newly introduced TorcFit™ connection may offer better stress distribution and torque resistance, but its clinical relevance-especially in narrow implants used for molars-remains untested.
Aged ≥ 18 years.
Require replacement of single missing molar tooth with dental implant in fully healed sites.
Controlled oral hygiene (full-mouth plaque and bleeding scores ≤ 25% at baseline).
Intact adjacent teeth and opposing dentition.
Localized/generalized periodontitis.
Any medical condition that may contraindicate implant treatment (Bornstein et al., 2009).
Bone metabolic disease and/or taking medications that affect bone metabolism.
Long term use of non-steroidal anti-inflammatory medications.
Parallel
Dental implant treatment (narrow implants)
Procedure/SurgeryReplacement of a missing molar tooth with a narrow dental implant
Dental implant treatment (standard implants)
Procedure/SurgeryReplacement of a missing molar tooth with a standard dental implant
Peri-implant mucosal recession rate
The peri-implant mucosal margin will be assessed by measuring the clinical crown height and recorded as yes/no
Emergence angle of implant restorations
Emergence angle of implant restorations will be measured on radiographs by recording the angle between the implant long axis and a line tangent to implant restorations
Implant success/survival rate
Implant success/survival rate will be assessed clinically after one year of implant restoration and annually up to three years. A successful implant is the one that will meet the criteria proposed by the European Federation of Periodontology (Albrektsson and Isidor, 1994), while a survived implant is the one that will remain in function but without meeting the success criteria. An implant is considered failed when it will be removed.
Changes in peri-implant marginal bone level
Changes in peri-implant marginal bone level will be assessed standardized periapical radiographs.
Implant stability measurements
Implant stability measurements will be recorded using an electronic handheld device (Osstell Beacon, W\&H, Göteborg, Sweden). The device uses the resonance frequency analysis (RFA) to measure the implant stiffness in implant stability quotient (ISQ) units (Sennerby and Meredith, 1998, Sennerby and Meredith, 2008). The ISQ scale ranges from 0 to 100 with values higher than 65 ISQ indicating a satisfactory implant stability (Atieh et al., 2012, Atieh et al., 2014, Sennerby and Meredith, 2008).
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