The Use of a Screw Sealer in Implant Abutment Fixation

EMANUEL ADRIAN BRATU1, LAURA CRISTINA RUSU2*, OLIMPIU LADISLAU KARANCSI1*, SORIN GHEORGHE MIHALI3 1 Victor Babes University of Medicine and Pharmacy, Faculty of Dentistry, Department of Implant Supported Restorations, 2 Eftimie Murgu Sq., 300041 Timisoara, Romania 2 Victor Babes University of Medicine and Pharmacy, Faculty of Dentistry, Department of Oral Patholog, 2 Eftimie Murgu Sq., 300041, Timisoara, Romania 3Vasie Goldis West University, Faculty of Dentistry, Department of Prosthodontics, 94-96 Revolutiei Blvd., 310025, Arad, Romania

For many years, implant-abutment connections were the subject of evolution. They evolved from external to internal and then to conical connections, with the idea of maintaining better soft tissue and bone conditions. Another goal was to have a very good adaptation to the implant body in order to prevent micromovement and microleakege [1]. Still today we have many studies wich show bacteria to be present even inside conical connection implants [2,3] and the use of clorhexidine is not eficient in decontaminating [4][5][6]. Even with modern implant connections, micromovement is still present, but the most important problem is immediate loading [7]. It has been demonstrated that implants need a initial insertion torque of about minimum 25-30 Ncm in order to be loaded immediately, but some components have to be tightend at the same amount of force. This can lead to implant movement in the bone. Also it has been proved that a one abutment one time procedure may reduce bacterial contamination of implants [4]. The present study is about a substance used in industr y for screw loosening prevention. Loctite 243 is a dimethacrilate ester combined with maleic acid, used in automotive industry for preventing screw loosenings and comes in the form of a blue liquid [8]. This is a in vitro study with several types of implants that shows that the use of this fluid enhances the stability of the connection and can prevent bacterial leakage, allowing the components to be tightend at a torque inferior to 20 Ncm, but offering a removal torque and a stability to the components equal or exceeding a tightening of 30 Ncm.

Materials and methods
For this study 2 implant systems with different connection types were used. MIS SEVEN with internal hex, standard platform diameter 3.75mm, length 11.5, and MIS C1 standard platform, diameter 3.75mm, length 11.5mm with conical connection. We used different connections in order to prove the eficciency of the material for all implant systems.
The aim of the study was to verify the effect of LOCTITE 243 used on a titanium interface between abutment screw/multi unit abutment and implant body.
Pairs of each implant type were inserted into plastic mandibles, wich were kept at 37 degrees Celsius, * email: laura.rusu@umft.ro, Phone+40728700049; email: olilk@umft.ro, Phone: +40740203222 This torque level was selected in order to simulate the possibility of immediate loading and osteointegration. It allows the fixation of the abutments with the torque recommended by the producer. One of each implant type recieved a multiunit abutment fixated with a torque wrench according to the manufacturer protocol (20Ncm) without any material inside, and another recieved a multiunit abutment screw immersed in LOCTITE 243 solution up to the last tread and immediately fixated with a torque wrench with a force of 15 Ncm. It is important to note, that there should be no excess of Loctite 243 coming out of the implant, and if so, it has to be immediately removed. Applying it only on the screw treads assures in most cases that no excess is observed. All implants were rinsed with saline solution and dryed out for 10 sec using compressed air before abutment fixation in order to simulate clinical conditions. The same protocol was used with a standard straight abutment for cement retained restorations.
According to the manufacturer protocol of Loctite, the screws of the abutments were untouched for 24 h. This is the setting time for Loctite on all materials tested before.
After this, a comparison was made for the reverse torque of the abutment screws fixated with and without Loctite 243.The measurements were taken with the use of the W&H Implantmed device (W&H Austria), using a angled handpiece and the original screwdrivers from each system. The Implantmed has a display wich can show the exact removal torque. We began with the same values of the insertion torque , increasing it by one NCM step by step, until the screw started to move.

Results and discussions
Removal torque of the abutment screw increased after 24 h with the use of Loctite 243 in all types of connections.
The removal torque of the components in internal hex implants (MIS Seven)fixated with Loctite 243 increased with 10 Ncm at a level of 25 Ncm, compared to the fixation torque of 15 Ncm. In the C1 Conical connection implants the increase was higher, reaching 30 Ncm. The components fixated without Loctite had the same removal torque as the fixation torque. Allowing the material to set is important, so no movement of the screws is recommended for 24h, and also the material is not to be exposed to air longer than 5 min, because it starts to set. These data are indicated in the sheets of the producer of Loctite. As implant component screws are made out of titanium and are very small we can equal them to the steel components of the industry with the smallest gaps. For the clinical use, it is important to assure that the interior of the implant shoud be clean and dry. This can be achived by the use of alcohol 96 grd, saline solution and airspray. Also it is better to fixate the multi unit abutment during the surgical time or after the use of a healing screw for at least 3 weeks. Fixation of the abutment at implant uncovery is the worst option because it is hard to keep out the blood from entering the interior of the implant, and then to dry it out as the flap is not elevated like in the surgical phase.
After 24 hours every implant wich recieved abutments fixated with LOCTITE 243 presented a higher value of the removal torque on the abutment screw. This shows that, if left untouched for 24 h, Loctite is able to generate a higher removal torque. On the other side, the removal torque was not to big to generate forces that could eventually be of danger to the implant abutment interface.
Also, a very thin layer of Loctite was present at the implant platform, showing perfect closure of the small spaces on this interface. Inside the implant, Loctite filled all voids generated by the anatomy of the connection.
The authors have a 15 year clinical experience using this material in the same protocol.
Recently, several articles [9][10][11][12][13] report of the benefits of using threadlockers in prevention of screw loosening and bacterial infiltration. Some other articles report the influence of the implant abutment interface in aspects of bacterial microlikage[14-21] and the benefits of using sealing agents [22,23].

Conclusions
Loctite 243 proved to be a efficient material in fixating and sealing out spaces between implant components. Because bacterial infiltration is documented even in conical connection implants [13], and a Poly anhidre ester showed antibacterial activity [24] we can assume that a good dosage of Loctite 243 (dimethacrilate ester combined with maleic acid) can eliminate bacterial colonization for all implant types. This is a important fact for the clinical use, and further in vivo studies have to be made in order to prove this fact [22, 23,25], and to prove that there is no inflammation of the soft tissues coming in contact with small amounts of Loctite.