Effect of Implant Macro-Design and Surface Treatment on Insertion Torque and Early Implant Stability Quotient (ISQ)

Background and Rationale Dental implants play a central role in the replacement of missing teeth, and defining the earliest point at which an implant can be safely loaded functionally remains a key unresolved issue in implant dentistry. Minimizing the time to functional and aesthetic rehabilitation may improve patient satisfaction and reduce the likelihood of migration of neighboring teeth into an edentulous site. Consequently, strategies that accelerate osseointegration remain of substantial clinical interest.

Implant stability can be divided into primary stability - mechanical fixation of the implant immediately after placement - and secondary stability, which reflects the transition to biological integration through new bone apposition on the implant surface. Two non-invasive parameters are commonly used to guide decisions about loading protocols: insertion torque value (ITV), measured in Newton centimeters (Ncm), which reflects the mechanical friction between the implant and surrounding bone at placement, and implant stability quotient (ISQ), obtained through resonance frequency analysis (RFA), which indirectly reflects the density and extent of bone-to-implant contact. ITV and ISQ may correlate at the time of implant placement, and both are considered useful indicators for decisions regarding loading timing.

Primary implant stability is influenced by bone density at the implant site, osteotomy preparation technique, and implant macrogeometry. Tapered implant designs, such as the Straumann Bone Level Tapered (BLT) and Megagen BlueDiamond (BD) systems, generally achieve higher insertion torque than cylindrical designs, which is particularly relevant in low-density bone. Although both BLT and BD implants are tapered, they differ in thread depth: the BD design features deeper threads that increase implant surface area and mechanical engagement with bone, which may increase insertion torque.

Secondary stability is influenced by the same local factors as primary stability, as well as by oral hygiene, infection control, mechanical loading protocol, and patient-related biological factors affecting bone metabolism (e.g., overall health, age, smoking status). A further determinant of secondary stability is implant surface treatment, which affects the rate of protein adsorption and osteoblast adhesion and therefore the onset of osseointegration. Additionally, titanium implant surfaces are subject to biological aging through hydrocarbon deposition, which reduces surface hydrophilicity and biological activity and may slow osseointegration. Implant macro-design and surface treatment are among the few variables in implant therapy that remain fully under clinician control.

With early machined implant surfaces, healing times of 3 months (mandible) and 6 months (maxilla) prior to prosthetic loading were historically recommended. The introduction of surface treatments such as sandblasted, large-grit, acid-etched (SLA) surfaces shortened proposed healing times to 6-12 weeks. A limitation of conventional SLA surfaces is their hydrophobicity. SLActive is a chemically modified, hydrophilic variant of the SLA surface: following sandblasting and acid-etching, implants are stored in an isotonic saline solution under nitrogen to prevent hydrocarbon contamination and to preserve a highly hydrophilic titanium oxide surface, which is intended to enhance early biological response and accelerate osseointegration. Clinical and histological studies have reported that SLActive implants outperform conventional SLA surfaces in early bone apposition, bone-to-implant contact, and early ISQ values.

XActive is a low-temperature vacuum plasma surface activation treatment (Plasma X Motion system, MegaGen Implant Co., Ltd.) applied chairside immediately prior to implant placement. Unlike manufacturer-applied hydrophilic treatments such as SLActive, this activation is performed at the point of care rather than during manufacturing, and is intended to reduce implant surface hydrocarbons and increase surface energy, thereby improving surface hydrophilicity and early implant stability. Because plasma activation is applied chairside rather than integrated into the manufacturing process, it can in principle be used with implant systems from any manufacturer, and has been shown in vitro to enhance protein adsorption and osteoblast response.

Separately, the nanostructured calcium-incorporated Xpeed® surface (used on Megagen BlueDiamond implants) has been reported to accelerate early bone formation compared with SLA surfaces in preclinical and early clinical studies, independent of plasma activation.

To date, no human randomized trial has directly compared XActive chairside plasma activation with manufacturer-applied SLActive treatment, nor has any trial investigated the combined effect of implant macro-design (Straumann BLT vs. Megagen BD) and surface treatment/activation status on ITV and early ISQ trajectories. This pilot randomized controlled trial is designed to address this gap by evaluating five implant macro-design and surface treatment combinations placed in healed posterior mandibular bone.

Study Objectives

The primary objectives of this pilot trial are:

To compare insertion torque values (ITV) between two implant macro-designs - Straumann Bone Level Tapered (BLT) and Megagen BlueDiamond (BD) - placed in healed posterior mandibular bone.

To compare early ISQ trajectories (from implant placement through 6 weeks) among five implant macro-design and surface treatment/activation combinations.

To explore the correlation between insertion torque and ISQ values at the time of implant placement.

As a pilot study, to estimate effect sizes and variability to inform the sample size calculation for a future, adequately powered randomized controlled trial.

Null Hypothesis There will be no statistically significant differences in early ISQ trajectories or insertion torque values among the five implant macro-design and surface treatment combinations placed in healed posterior mandibular bone.

Study Design This will be a prospective, randomized, pilot clinical trial with five parallel arms, conducted at a single private dental clinic (Dantų implantologijos centras, Kernavės g. 88, Vilnius, LT-08216, Lithuania). The protocol has been approved by the Vilnius University Regional Bioethics Committee (approval no. 2025/11-1722-1165).

A total of 50 implants will be enrolled, with 10 implants allocated to each of five treatment groups. This sample size is consistent with methodological recommendations for pilot studies, which suggest that small sample sizes are appropriate for feasibility assessment and estimation of variability ahead of a definitively powered trial.

Randomization and Allocation Implants will be randomly allocated to one of five groups (n=10 per group) using a sealed-envelope method. The envelope containing the group assignment will be drawn immediately after osteotomy preparation and immediately prior to implant placement, in order to standardize the timing of randomization relative to the surgical sequence.

Study Groups

Group 1 - BLT SLA XActive: Straumann Bone Level Tapered implant with a conventional SLA surface, activated chairside with the XActive plasma treatment immediately before placement.

Group 2 - BLT SLActive: Straumann Bone Level Tapered implant with the manufacturer-applied hydrophilic SLActive surface (no chairside plasma activation).

Group 3 - BD XpeedActive: Megagen BlueDiamond implant with the nanostructured calcium-incorporated Xpeed® surface, activated chairside with the XActive plasma treatment immediately before placement.

Group 4 - BD Xpeed: Megagen BlueDiamond implant with the standard Xpeed® surface (no plasma activation).

Group 5 - BLT SLA (control): Straumann Bone Level Tapered implant with the conventional SLA surface (no plasma activation).

This design allows comparison of implant macro-design independent of surface treatment (BLT vs. BD, pooling across surface/activation status) and comparison of surface treatment/activation status within each macro-design (activated vs. non-activated in both the BLT and BD systems), as well as a direct comparison of chairside plasma activation (XActive) against manufacturer-integrated hydrophilic treatment (SLActive).

Plasma Activation Procedure For implants assigned to plasma activation, the implant will be retrieved from its sterile container using the handpiece implant driver. The handpiece with the implant attached will be placed in the magnetic holder of the Plasma X Motion device, and the activation cycle will be initiated according to the manufacturer's instructions, completing automatically within approximately 50 seconds. Immediately following completion of the cycle, the magnetic holder will be removed from the device and the implant will be inserted into the prepared osteotomy according to the implant manufacturer's surgical protocol, without delay.

Surgical Procedure Two grams of amoxicillin (Ospamox, Sandoz GmbH, Austria) will be administered as a single preoperative dose; no antibiotics will be prescribed postoperatively. All surgeries will be performed under local anesthesia by the same surgeon to minimize operator variability. A mid-crestal incision will be made and a buccal mucoperiosteal flap elevated. Vertical soft tissue thickness will be measured with a periodontal probe applied to the unelevated lingual flap, after which the lingual flap will be elevated. Osteotomy preparation will follow the standard protocol recommended by the respective implant manufacturer, followed by implant insertion positioned 4 mm apical to the gingival margin. A healing abutment will be placed and sutures applied. Postoperative 0.12% chlorhexidine mouthwash will be prescribed; no postoperative antibiotics will be given.

Statistical Analysis Plan Statistical analysis will be performed using R (v. 4.0.4). Between-group comparisons of quantitative variables for two groups will use Student's t-test or the non-parametric Mann-Whitney U test, as appropriate. Comparisons among more than two groups will use one-way analysis of variance (ANOVA) or the non-parametric Kruskal-Wallis test, as appropriate. Normality of distributions will be assessed using the Shapiro-Wilk test. Paired comparisons (baseline vs. follow-up timepoints within the same implant) will use the paired t-test or Wilcoxon signed-rank test, as appropriate. Associations between insertion torque and ISQ will be assessed using Spearman correlation. Descriptive statistics will include mean, standard deviation, quartiles (Q1, Q3), median, and available number of observations for continuous variables, and absolute counts and percentages for categorical variables. A p-value <0.05 will be considered statistically significant.

Sample Size Justification As a pilot study, the planned enrollment of 10 implants per group (50 implants total) is intended to assess feasibility and estimate effect sizes and variability rather than to achieve definitive statistical power for between-group comparisons, consistent with established pilot study methodology. Data generated by this pilot will be used to perform a formal power analysis to determine the sample size required for a future, adequately powered confirmatory trial.

Significance This trial is intended to provide preliminary data on whether implant macro-design (thread geometry) and surface activation strategy (chairside plasma activation vs. manufacturer-integrated hydrophilic treatment) meaningfully influence early implant stability dynamics in healed, high-quality mandibular bone. Because chairside plasma activation systems such as XActive can, in principle, be applied to implants from any manufacturer, a favorable comparison with proprietary hydrophilic surfaces such as SLActive could have practical implications for clinical protocol selection and implant loading timelines. Findings from this pilot are also intended to inform the design, eligibility criteria, and sample size of a future confirmatory trial, potentially including sites with lower primary stability (e.g., softer bone or immediate implant placement), where surface-treatment effects on ISQ dynamics may be more pronounced.