Key words: short dental implants, atrophic ridge, crestal bone stress, implant biomechanics, bone augmentation alternative.

Introduction

Short dental implants, defined as those with a Designed Intrabony Length (DIL) of ≤8 mm (2006 SSID Conference), have evolved into a reliable option in implant dentistry (Misch, 2008). Although 7 mm implants have existed for over 30 years, early designs such as those from Nobelpharma during the Brånemark era showed limited success in softer bone (D3/D4), particularly in the posterior maxilla (Ericsson et al., 2000). He later noted that eliminating countersinking improved outcomes, highlighting the importance of surgical technique (Albrektsson and Wennerberg, 2004).¹ Modern advances in implant design, surface treatments, and surgical protocols have significantly improved the predictability of short implants. They now demonstrate survival rates comparable to longer implants, especially in sites with limited vertical bone height (Esposito et al., 2014). Their advantages include reduced need for bone grafting, lower surgical morbidity, shorter treatment time, and cost-effectiveness (Felice et al., 2019).²

Short and ultrashort implants are increasingly used in atrophic jaws, elderly or medically compromised patients, and select adolescent cases (Eriksson et al., 2018). This review highlights their evolution, clinical applications, outcomes, and limitations, underscoring their role as a minimally invasive and effective treatment option in modern implantology.³

History of Short Dental Implants

The concept of short dental implants evolved to address clinical challenges associated with reduced alveolar bone height, aiming to avoid invasive augmentation procedures (Misch, 2008). Although implants measuring 7.0 mm or less have been available since the late 20th century, early adoption was limited due to biomechanical concerns and variable survival rates in poor bone quality (Ericsson et al., 2000).⁴

The scientific history of short implants began with the development of root-form implants by Brånemark and colleagues in the 1960s and 1970s. These implants, commercialized by Nobelpharma, performed well in dense bone types (D1 and D2) (Brånemark et al., 1977), showing survival rates of 93.7% in the mandible and 90.2% in the maxilla. However, significantly reduced success was observed in the posterior maxilla, particularly with shorter implants in softer bone (D3 and D4) (Testori et al., 2004).

In 2006, the State of the Science in Implant Dentistry (SSID) Conference, organized by the Academy of Osseointegration, formally defined short implants as those with a Designed Intrabony Length (DIL) of 8.0 mm or less, a definition supported by historical clinical evidence (Misch, 2008). Implants of 7.0 mm had already been available for over 30 years, with 6.0 mm and 5.0 mm implants introduced in 1997 and 2008 respectively (Annibali et al., 2012).⁴

The importance of surgical technique was emphasized during the 2009 AO Annual Meeting, when Dr. Tomas Albrektsson noted poor outcomes for 7.0 mm Nobelpharma implants in the posterior maxilla. However, a study led by Arun Garg demonstrated that eliminating countersinking improved implant stability and survival significantly, with success rates in the 90% range, underscoring the technique sensitivity of short implant success (Albrektsson and Wennerberg, 2004).⁵

Initially, short implants in the 8–10 mm range were mainly developed by smaller companies such as 7br, MegaGen, Bicon, Jeneric, and BTI (Felice et al., 2019). Over time, major manufacturers including Straumann, Nobel Biocare, and Astra Tech began offering scientifically validated short and ultrashort implants (≤6 mm), demonstrating survival rates comparable to standard-length implants when placed under appropriate conditions (Esposito et al., 2014). Ultrashort dental implants from different manufacturers have been designed to address cases with limited vertical bone height, particularly in the posterior mandible and maxilla (Eriksson et al., 2018). These implants range from 5.0 mm to 8.0 mm, with some as short as 5.0 mm qualifying as “ultrashort.” The Bicon™ implant (6.0 × 5.7 mm) features a unique plateau-root form enhancing bone integration, while Astra OsseoSpeed™ and Straumann® implants (e.g., 4.0 × 6.0 mm, 4.1 × 6.0 mm) utilize surface-treated threaded designs to improve osseointegration and primary stability. OT Medical OT-F³® implants are cylindrical (5.0 × 5.0 mm and 4.1 × 5.0 mm), maximizing bone-to-implant contact in shallow ridges. The Dentaurum® series offers various thread patterns within the 5.0 mm length range, tailored for different bone densities and loading conditions (Chen et al., 2015).⁶ These implants provide a minimally invasive solution in regions where traditional longer implants are risky or unfeasible, avoiding complex procedures like bone grafting or sinus lifts while ensuring long term stability and function (Felice et al., 2019).

Advantages of Short Dental Implants

1. Avoidance of Bone Augmentation Procedures
   Short implants allow placement in sites with limited vertical bone height, thereby eliminating or reducing the need for complex bone grafting or sinus lift surgeries. This leads to less invasive treatment and reduced patient morbidity (Renouard & Nisand, 2006).⁷
2. Reduced Surgical Morbidity and Treatment Time
   Because short implants can be placed without bone augmentation, patients experience shorter surgical procedures, faster recovery, and decreased overall treatment duration (Monje et al., 2014).
3. Cost-Effectiveness
   Avoiding grafting and additional surgeries reduces treatment costs significantly for both patients and practitioners (Bechara et al., 2017).
4. High Success Rates with Modern Designs and Surfaces
   Advancements in implant surface technology (e.g., SLActive) and improved implant designs (plateau root form, wider diameters) have demonstrated survival rates comparable to standard-length implants, even in poor-quality bone (Gallucci et al., 2018).
5. Minimally Invasive Option for Medically Compromised and Elderly Patients
   Short implants offer a safer alternative for patients with systemic health issues or those who cannot tolerate extensive surgical procedures (Monje et al., 2014).⁸
6. Improved Patient Acceptance and Satisfaction
   Reduced surgical complexity and shorter treatment times improve patient comfort and willingness to undergo implant therapy (Rossi et al., 2016).

Disadvantages of Short Dental Implants

1. Biomechanical Challenges and Stress Distribution
   Short implants have a higher crown-to-implant ratio, which can increase stress concentration at the crestal bone. This may lead to marginal bone loss if not managed with proper implant design and prosthetic planning.⁹
2. Technique Sensitivity
   Success with short implants is highly dependent on precise surgical technique, including avoiding excessive insertion torque and countersinking. Poor technique can significantly reduce implant stability and survival.
3. Limited Indications for Single Molar Replacement
   Single short implants in molar regions under immediate loading are generally not recommended due to increased biomechanical loads unless used with splinting or in low bite force patients.¹⁰
4. Potential for Increased Marginal Bone Loss
   Although comparable to longer implants, some studies report slightly higher marginal bone loss during the first-year post-loading (0.5–1.37 mm), which requires monitoring.¹¹
5. Restricted Prosthetic Space
   Short implants require careful prosthetic planning because limited implant length restricts abutment choices and may affect occlusal design.
6. Less Suitable in Very Poor Bone Quality without Adjuncts
   In severely compromised bone (Type IV), short implants may have reduced predictability unless combined with bone augmentation or specialized implant designs.¹²

Indications and Contraindications

Short and ultrashort implants are indicated in cases with limited vertical bone height, avoiding the need for bone grafting. They are useful for edentulous jaws, single or multiple tooth replacements, narrow interdental spaces, adolescent cases (with subcrestal placement), and atrophic anterior maxillae. Absolute contraindications include uncontrolled systemic diseases (e.g., diabetes), recent bisphosphonate use with ONJ, and recent radiation in the implant area. Relative contraindications include heavy smoking, poor oral hygiene, untreated periodontal disease, and systemic conditions needing medical clearance. With advancements in design and surface technology, short implants now offer high success rates in challenging conditions.¹³

Clinical Applications of Short Implants

Short dental implants, generally defined as those with an intraosseous length of ≤8 mm, have significantly expanded the scope of implant dentistry, especially in cases with compromised vertical bone height. Their use avoids the need for extensive bone grafting procedures, thereby reducing surgical morbidity, cost, and treatment duration. Clinical applications of short implants are diverse and include both partially and fully edentulous patients, with favorable long-term outcomes in various anatomical scenarios.¹⁴

1. Atrophic Posterior Maxilla
   One of the most common indications for short implants is the atrophic posterior maxilla, where bone height is often reduced due to maxillary sinus pneumatization. Conventional implants in this region typically require sinus floor elevation, which is invasive and technique-sensitive. Short implants can be used alone or in conjunction with minimally invasive internal sinus lift procedures to restore function effectively without a full lateral window sinus lift. Studies report comparable success rates between short implants and those placed with sinus augmentation, even in cases with residual bone height as low as 4–6 mm.¹⁵
2. Atrophic Posterior Mandible
   In the posterior mandible, the inferior alveolar nerve limits the available bone height. Traditional treatment involves vertical ridge augmentation or nerve lateralization, both associated with higher complication rates. Short implants (6–8 mm) offer a safe and predictable alternative with high survival rates, especially when splinted in fixed prostheses (Renouard & Nisand, 2006). Their use also helps maintain the structural integrity of the mandibular canal.¹⁶
3. Geriatric and Medically Compromised Patients
   Short implants are particularly beneficial for elderly and medically compromised patients, where extensive surgery may pose greater risks. The reduced surgical time, minimal trauma, and lower postoperative complications make them ideal for patients with systemic diseases such as diabetes, osteoporosis, or cardiovascular conditions (Monje et al., 2014). Additionally, their shorter healing periods improve patient compliance and satisfaction.¹⁷
4. Full Arch Rehabilitation
   Short implants are successfully used in full-arch implant-supported prostheses, especially in the “All-on-Four” or “All-on-Six” configurations. In cases where posterior vertical bone is insufficient, tilted or axially placed short implants can provide posterior support, avoiding the need for distal cantilevers or bone grafting (Bechara et al., 2017).
5. Adolescents and Growing Patients
   Historically, dental implants were contraindicated in growing individuals due to concerns over osseointegration and implant ankylosis affecting jaw development. However, short implants placed subcrestally with specific implant designs have shown promising outcomes in adolescents, with studies indicating high survival rates and manageable prosthetic adjustments over time.¹⁸
6. Narrow Ridge Sites and Anterior Esthetic Zone
   In situations where the buccolingual ridge width is insufficient for standard diameter implants, short and narrow implants offer an excellent solution. They are particularly useful in anterior esthetic zones such as congenitally missing maxillary lateral incisors or mandibular incisors, where root proximity or esthetic demands limit implant dimensions.¹⁹
7. Re-treatment and Limited Prosthetic Space
   Short implants are ideal in cases of failed previous implant treatment where vertical space is restricted due to opposing dentition or prosthetic limitations. They also provide a solution in patients unwilling to undergo further surgical augmentation.²⁰

The Brånemark System

In it implant originally featured a turned-surface finish available in 6.5 mm (“7 mm”) and 9.5 mm (“10 mm”) lengths since the 1960s. In 1993, an 8.5 mm (actual 8.0 mm) length was introduced for the 3.75 mm and 4 mm diameter implants. Both 7 mm and 8.5 mm lengths were later offered with wide diameter and NobelSpeedy implants.

The Brånemark System implant with a turned surface finish has been available in 6.5 mm (“7 mm”) and 9.5 mm (“10 mm”) lengths since the 1960s. In 1993, an 8.5 mm (actual 8.0 mm) length was introduced for the 3.75 mm and 4 mm diameter implants. Both the 7 mm and 8.5 mm lengths were also offered in wide-diameter versions and as part of the NobelSpeedy implant line. The design features of the self-tapping Mk III implant, the tapered shapes of the Mk IV and NobelSpeedy implants, and the conical connection abutment interface were integrated to create the NobelParallel CC implant.²¹

Straumann Short Implant System (6 mm)

Straumann introduced 6 mm short implants with the TPS surface in the late 1980s, showing favorable clinical results by the late 1990s. In 1998, the SLA (Sandblasted Large-Grit Acid etched) surface was launched for 6 mm implants, followed by the SLActive surface in 2005. The SLActive surface improves osseointegration speed and bone-to-implant contact, while the SLA surface remains one of the most well documented in the market. Later, the Roxolid alloy (TiZi) was introduced, enhancing implant strength and osseointegration, initially focusing on reduced diameter implants. This alloy is now used across Straumann’s implant range, including SLA and SLActive surfaces.

The 6 mm implants come in Standard (2.8 mm polished collar) and Standard Plus (1.8 mm polished collar) designs, with body diameters of 4.1 mm and 4.8 mm, and neck widths of 4.8 mm (regular) and 6.5 mm (wide). The implant has a solid screw parallel-wall body with 1.25 mm thread pitch and a rounded apex. The tulip-shaped neck improves primary stability, especially in the posterior maxilla. (Fig.1)



The polished collar is positioned at the soft tissue level, reducing crestal bone loss and enhancing peri-implant tissue stability. Since these implants are mostly used in posterior regions, esthetics are less critical, and the polished collar’s benefits outweigh its slight visibility (Figure 1). The tissue level design includes an internal Morse taper conical connection (SynOcta), providing a biological seal and strong mechanical stability, which is especially helpful for short implants by reducing the crown-to-implant ratio.

Short implants are an effective, minimally invasive alternative for atrophic posterior maxilla cases, reducing morbidity, treatment time, and cost compared to sinus floor elevation (SFE). Patient satisfaction is high.²² However, short implants should be splinted when placed as multiple adjacent implants in the posterior maxilla for better outcomes. Single short implants in molar sites are generally not recommended except in rare cases like elderly patients with low bite force.

Straumann short implant system (4mm)

The 4 mm long, solid screw, SLActive soft tissue level implant with a 0.8 mm thread pitch and titanium grade 4 was introduced in 2009, differing from the well-known 6 mm implant. Unlike the 6 mm implant’s 1.25 mm thread pitch, this shorter implant features a finer 0.8 mm pitch. It is available only in Roxolid (Titanium Zirconium alloy) with an SLActive surface and a Standard Plus (SP) 1.8 mm polished collar neck. It comes in three configurations (Figure 2):

• 4.1 mm diameter with 4.8 mm neck (Regular Neck)
• 4.8 mm diameter with 4.8 mm neck (Wide body)
• 4.8 mm diameter with 6.5 mm neck (Wide Neck).

The surgical protocol is similar, with drills and depth gauges marked at 4 mm. Extreme care must be taken to avoid overdrilling both vertically and horizontally, as this risks nerve damage or loss of primary stability. In the atrophic posterior mandible, where alveolar bone is often resorbed, implants are placed in cortical bone. The reduced thread pitch provides very high primary stability, so tapping is strongly recommended to prevent excessive insertion torque, which could compromise osseointegration.²³

Long-Term Performance of Ultrashort Implants in the Posterior Maxilla

Many Studies have shown that the short- and long-term survival rates of ultrashort (5–6 mm) wide plateau root form implants in the posterior maxilla are comparable to those of longer implants. While conventional protocols recommend longer implants that often require extensive bone grafting, recent clinical evidence suggests that ultrashort plateau-type implants can successfully restore maxillary molars without the need for large grafts. This challenges the traditional belief that ultrashort implants provide insufficient bone contact to withstand masticatory forces, particularly in the poorly mineralized maxillary bone.²⁴

In clinical practice, 5mm and 6mm plateau implants have demonstrated reliable long-term outcomes, avoiding the complications and costs associated with extensive grafting. Therefore, the use of ultrashort plateau implants with minimal or no grafting presents a predictable and less invasive alternative to longer implants with large grafts in the posterior maxilla.²⁵

Long-Term Performance of Ultrashort Implants in the Posterior Mandible

Ultrashort implants (≤6 mm) have shown excellent long-term performance in the posterior mandible, where bone density is typically high. Despite earlier concerns, studies have demonstrated that these implants provide stable osseointegration and maintain crestal bone levels for over a decade. Their use reduces the risk of complications such as nerve injury and eliminates the need for bone grafting in many cases. With advances in implant design and surface technology, ultrashort implants now offer a reliable, minimally invasive solution for restoring posterior mandibular teeth, with survival rates comparable to longer implants.²⁶

Limitations of Short Dental Implants

• Reduced Bone Contact-Smaller surface area limits osseointegration and primary stability (Misch et al., 2006).
• Higher Mechanical Complications- Increased crown-to-implant ratio may lead to screw loosening or component fracture (Malchiodi et al., 2014).
• Less Success in Poor Bone Quality-Especially in areas like the posterior maxilla with low bone density (Anitua et al., 2010).
• Limited Clinical Use-Not ideal for bruxism, long-span prostheses, or high occlusal forces (Esposito et al., 2011).
• Risk of Marginal Bone Loss-May show greater bone loss under heavy functional load (Renouard & Nisand, 2006).

Discussion

The development of short dental implants (≤8 mm) marks a significant advancement in implant dentistry, offering solutions for cases with limited vertical bone height without the need for invasive grafting procedures. Initially met with skepticism due to concerns over reduced stability and higher failure rates—especially in poor-quality bone like the posterior maxilla— modern short implants have demonstrated survival rates comparable to standard implants, thanks to advances in design and surface technology.²⁷ Standardization of short implants following the 2006 SSID Conference, along with innovations such as plateau-root forms, SLA/ SLActive surfaces, and high-strength alloys like Roxolid, has enhanced bone-to-implant contact and load distribution. These features improve primary stability, reduce stress on crestal bone, and mitigate crown-to-implant ratio concerns.²⁸

Clinically, short implants are highly beneficial in challenging situations, including atrophic ridges, elderly or medically compromised patients, and full-arch restorations. Their minimally invasive nature reduces surgical time, cost, and patient morbidity. However, success depends on careful case selection, proper surgical technique, implant design, and appropriate loading protocols. Splinting short implants, especially in the posterior maxilla, improves outcomes, while single molar short implants require cautious planning.²⁹ Long-term studies now support the use of short and ultrashort implants (≤6 mm), showing comparable survival rates to longer implants. This challenges traditional views and expands treatment possibilities for anatomically limited cases.³⁰ Short dental implants have transitioned from a less reliable option to a well-supported, effective treatment modality. When used judiciously, they offer predictable, minimally invasive, and cost-effective solutions that enhance both function and patient satisfaction.³¹

Conclusion

Short dental implants have emerged as a viable alternative to conventional implants in cases with reduced vertical bone availability, offering predictable outcomes with minimal surgical morbidity. Advances in implant macro- and micro-design, surface modifications, and improved biomechanical understanding have enhanced their long-term clinical performance. Current evidence indicates comparable survival rates to standard-length implants while reducing the need for complex bone augmentation procedures. Nevertheless, their success is highly dependent on meticulous case selection, prosthetic planning, and controlled loading conditions. As ongoing research further optimizes implant design and protocols, short implants are poised to play an increasingly prominent role in contemporary implant dentistry.

References