Hee Moon Kyung

Critical factors for the success of orthodontic mini-implants: A systematic review

INTRODUCTION This systematic review was undertaken to discuss factors that affect mini-implants as direct and indirect orthodontic anchorage. METHODS The data were collected from electronic databases (Medline [Entrez PubMed], Embase, Web of Science, Cochrane Library, and All Evidence Based Medicine Reviews). Randomized clinical trials, prospective and retrospective clinical studies, and clinical trials concerning the properties, affective factors, and requirements of mini-implants were considered. The titles and abstracts that appeared to fulfill the initial selection criteria were collected by consensus, and the original articles were retrieved and evaluated with a methodologic checklist. A hand search of key orthodontic journals was performed to identify recent unindexed literature. RESULTS The search strategy resulted in 596 articles. By screening titles and abstracts, 126 articles were identified. After the exclusion criteria were applied, 16 articles remained. The analyzed results of the literature were divided into 2 topics: placement-related and loading-related factors. CONCLUSIONS Mini-implants are effective as anchorage, and their success depends on proper initial mechanical stability and loading quality and quantity.

Mechanical properties of self-drilling orthodontic micro-implants with different diameters

OBJECTIVE The hypothesis to be tested is that peak-insertion torque of self-drilling micro-implants of an appropriate diameter correlates with peak-removal torque mechanically. MATERIALS AND METHODS A total of 360 self-drilling micro-implants composed of five different types were used. They (24 of each group) were inserted in three types of artificial bone with the use of a driving torque tester at a speed of 15 rpm. Insertion torque was measured during the placement, while the removal torque was measured within 3 days after insertion. RESULTS Most of the micro-implants in type A sheared before they were completely inserted in 40-pounds per cubic foot bone. The implants in other types were successfully inserted without implant breakage and bone fracture in all bone densities. There was a statistically significant correlation between insertion torque and removal torque (r > or = 0.43543, P = .0001). There were significant differences in insertion and removal torque among the diameters of implants and bone densities with an increasing tendency. The torque loss rates reduced as the diameter of the implant and bone density increased. CONCLUSIONS Micro-implants with a diameter of less than 1.3 mm are unsuitable for insertion into a bone with a density greater than 40 pounds per cubic foot mechanically when one is using a self-drilling technique.

Central cyclooxygenase inhibitors reduced IL-1β-induced hyperalgesia in temporomandibular joint of freely moving rats

&NA; Microinjection of formalin (5%, 50 μl) into a temporomandibular joint (TMJ) causes noxious behavioral responses in freely moving rats. In the present study, we investigated the role of central cyclooxygenase (COX) pathways in IL‐1β‐induced hyperalgesia with formalin‐induced TMJ pain model. Intra‐articular injection of 100 pg or 1 ng of IL‐1β significantly facilitated formalin‐induced behavior by 130 or 174% in the number of scratches. Intracisternal administration of 100 pg or 1 ng of IL‐1β also significantly increased formalin‐induced behavior by 166 or 82% in the number of scratches. IL‐1β‐induced hyperalgesia was blocked by pretreatment with IL‐1 receptor antagonist. Intracisternal pretreatment with SC‐560, a selective COX‐1 inhibitor, or NS‐398, a selective COX‐2 inhibitor, abolished intra‐articular administration of IL‐1β‐induced hyperalgesic response. Intracisternal pretreatment with NS‐398, a selective COX‐2 inhibitor, abolished the intracisternal administration of IL‐1β‐induced hyperalgesic response, while pretreatment with SC‐560, a selective COX‐1 inhibitor, did not change IL‐1β‐induced hyperalgesic responses. On the other hand, pretreatment with acetaminophen, a tentative COX‐3 inhibitor, also abolished both intra‐articular and intracisternal administration of IL‐1β‐induced hyperalgesic responses. These results indicate that central COX‐2 plays important role in the central administration of IL‐1β‐induced hyperalgesia and that central COX‐1/2 pathways mediate peripheral administration of IL‐1β‐induced hyperalgesia in the TMJ. Central COX‐3 inhibitor seems to play an important role in the nociceptive process associated with both peripheral and central administration of IL‐1β‐induced hyperalgesia in TMJ. It is concluded that central acting of COX‐3 inhibitors may be of therapeutic value in the treatment of inflammatory pain in TMJ.

Monitoring of Bone Temperature during Osseous Preparation for Orthodontic Micro-Screw Implants: Effect of Motor Speed and Ressure

The temperature at the surface of the bony recipient site during drilling for orthodontic micro-implant placement was monitored using infrared thermography. The primary objective was to identify proper drilling conditions to allow efficient drilling without raising the bone temperature above the threshold temperature of 44oC to 47oC. Bovine ribs were selected to provide cortical bone of a similar quality to the human mandible. Four drilling conditions combining 2 motor speeds (600 and 1200 rpm) and 2 pressure loads (500 g and 1000 g) were established based on clinical practice. Much care was taken to duplicate an oral environment, although no irrigation was used to allow the infrared radiation to transmit without being hindered by cooling water. Thermal images were recorded using a Thermovision 900 system (Amega, Danderryd, Sweden). The results showed that the temperature rise relys significantly on the drilling speed and pressure. When both the drilling speed and the pressure were low, the cortical bone could not be cut. However, increasing either the speed or the pressure resulted in a temperature increase. Drill speed of 600 rpm at the pressure load 1000g produced more or less the same temperature, 40- 45 o C, as when the drill speed was increased to 1200 rpm while keeping the load at 500g. Yet, a temperature as high as 62.4 o C was recorded when combining the high motor speed and high pressure. Most of the temperature rise took place during the initial 5-10 seconds of drilling, indicating that intermittent irrigation at an interval of 5 seconds or less would be of particular importance to minimize possible thermal trauma.

Low doses of cannabinoids enhance the antinociceptive effects of intracisternally administered mGluRs groups II and III agonists in formalin-induced TMJ nociception in rats

Abstract This study provides the first demonstration that central cannabinoids modulate the antinociceptive actions of metabotropic glutamate receptors (mGluRs) on formalin‐induced temporomandibular joint (TMJ) nociception. Noxious scratching behavior induced by formalin injection in the TMJ was used as a model of pain. Intracisternal injection of 30 μg of WIN 55,212‐2, a non‐subtype selective cannabinoid receptor agonist, attenuated the number of scratches by 75% as compared with the vehicle‐treated group, whereas vehicle alone or 3 or 10 μg of WIN 55,212‐2 had no effect. To explore the postulated interaction between central cannabinoid receptors and mGluRs, effects of combined administration of sub‐analgesic doses of WIN 55,212‐2 and group II or III mGluR agonists were tested. Group II or III mGluRs agonists were administered intracisternally 10 min after intracisternal administration of WIN 55,212‐2. Neither 100 nmol APDC, a group II mGluRs agonist, nor L‐AP4, a group III mGluR agonist, altered nociceptive behavior when given alone but significantly inhibited the formalin‐induced nociceptive behavior in the presence of a sub‐threshold dose (3 μg) of WIN 55,212‐2. The ED50 value of APDC or L‐AP4 was significantly reduced upon co‐treatment with WIN 55,212‐2 than in the vehicle‐treated group, highlighting the important therapeutic potential of the combined administration of group II or III mGluR agonists with cannabinoids to effectively treat inflammatory pain associated with the TMJ. Potentiating effects of group II or III mGluRs agonists will likely permit the administration of cannabinoids at doses that do not achieve significant accumulation to produce undesirable motor dysfunction.

Comparison of stainless steel and titanium alloy orthodontic miniscrew implants: A mechanical and histologic analysis

INTRODUCTION The detailed mechanical and histologic properties of stainless steel miniscrew implants used for temporary orthodontic anchorage have not been assessed. Thus, the purpose of this study was to compare them with identically sized titanium alloy miniscrew implants. METHODS Forty-eight stainless steel and 48 titanium alloy miniscrew implants were inserted into the tibias of 12 rabbits. Insertion torque and primary stability were recorded. One hundred grams of tensile force was applied between half of the implants in each group, resulting in 4 subgroups of 24 specimens each. Fluorochrome labeling was administered at weeks 4 and 5. When the rabbits were euthanized at 6 weeks, stability and removal torque were measured in half (ie, 12 specimens) of each of the 4 subgroups. Microdamage burden and bone-to-implant contact ratio were quantified in the other 12 specimens in each subgroup. Mixed model analysis of variance was used for statistical analysis. RESULTS All implants were stable at insertion and after 6 weeks. The only significant difference was the higher (9%) insertion torque for stainless steel. No significant differences were found between stainless steel and titanium alloy miniscrew implants in microdamage burden and bone-to-implant contact regardless of loading status. CONCLUSIONS Stainless steel and titanium alloy miniscrew implants provide the same mechanical stability and similar histologic responses, suggesting that both are suitable for immediate orthodontic clinical loads.

Clinical Applications of Orthodontic Microimplant Anchorage in Craniofacial Patients

Microimplant anchors, also known as temporary anchorage devices, mini- and micro-screws, have been used to enhance orthodontic anchorage for difficult tooth movements. Here, the authors describe how microimplants can be used to help treat craniofacial patients by supporting distraction osteogenesis procedures, maxillary protraction procedures, cleft segment expansion and stabilization, and tooth movement into narrow alveolar cleft sites. While most craniofacial patients are treated without microimplants, it would be worthwhile to identify which cases could benefit from microimplant anchorage. As an adjunct to orthodontic treatment, the microimplant offers a potential method for solving troublesome orthodontic and surgical problems such as guiding distraction procedures with orthodontics when primary teeth are exfoliating, addressing residual maxillary cants after vertical distraction osteogenesis of a ramus, stabilizing an edentulous premaxilla, and moving teeth into atrophic alveolar ridges. These cases are presented to open a dialogue on their possible uses in craniofacial patients.

Incorporation of silver nanoparticles on the surface of orthodontic microimplants to achieve antimicrobial properties

Objective Microbial aggregation around dental implants can lead to loss/loosening of the implants. This study was aimed at surface treating titanium microimplants with silver nanoparticles (AgNPs) to achieve antibacterial properties. Methods AgNP-modified titanium microimplants (Ti-nAg) were prepared using two methods. The first method involved coating the microimplants with regular AgNPs (Ti-AgNP) and the second involved coating them with a AgNP-coated biopolymer (Ti-BP-AgNP). The topologies, microstructures, and chemical compositions of the surfaces of the Ti-nAg were characterized by scanning electron microscopy (SEM) equipped with energy-dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). Disk diffusion tests using Streptococcus mutans, Streptococcus sanguinis, and Aggregatibacter actinomycetemcomitans were performed to test the antibacterial activity of the Ti-nAg microimplants. Results SEM revealed that only a meager amount of AgNPs was sparsely deposited on the Ti-AgNP surface with the first method, while a layer of AgNP-coated biopolymer extended along the Ti-BP-AgNP surface in the second method. The diameters of the coated nanoparticles were in the range of 10 to 30 nm. EDS revealed 1.05 atomic % of Ag on the surface of the Ti-AgNP and an astounding 21.2 atomic % on the surface of the Ti-BP-AgNP. XPS confirmed the metallic state of silver on the Ti-BP-AgNP surface. After 24 hours of incubation, clear zones of inhibition were seen around the Ti-BP-AgNP microimplants in all three test bacterial culture plates, whereas no antibacterial effect was observed with the Ti-AgNP microimplants. Conclusions Titanium microimplants modified with Ti-BP-AgNP exhibit excellent antibacterial properties, making them a promising implantable biomaterial.

Laser-treated stainless steel mini-screw implants: 3D surface roughness, bone-implant contact, and fracture resistance analysis

BACKGROUND/OBJECTIVES This study investigated the biomechanical properties and bone-implant intersurface response of machined and laser surface-treated stainless steel (SS) mini-screw implants (MSIs). MATERIAL AND METHODS Forty-eight 1.3mm in diameter and 6mm long SS MSIs were divided into two groups. The control (machined surface) group received no surface treatment; the laser-treated group received Nd-YAG laser surface treatment. Half in each group was used for examining surface roughness (Sa and Sq), surface texture, and facture resistance. The remaining MSIs were placed in the maxilla of six skeletally mature male beagle dogs in a randomized split-mouth design. A pair with the same surface treatment was placed on the same side and immediately loaded with 200 g nickel-titanium coil springs for 8 weeks. After killing, the bone-implant contact (BIC) for each MSI was calculated using micro computed tomography. Analysis of variance model and two-sample t test were used for statistical analysis with a significance level of P <0.05. RESULTS The mean values of Sa and Sq were significantly higher in the laser-treated group compared with the machined group (P <0.05). There were no significant differences in fracture resistance and BIC between the two groups. LIMITATION animal study CONCLUSIONS/IMPLICATIONS Laser treatment increased surface roughness without compromising fracture resistance. Despite increasing surface roughness, laser treatment did not improve BIC. Overall, it appears that medical grade SS has the potential to be substituted for titanium alloy MSIs.

Microdamage generation by tapered and cylindrical mini-screw implants after pilot drilling

OBJECTIVE To investigate the relationship between mini-screw implant (MSI) diameter (1.6 vs 2.0 mm) and shape (tapered vs cylindrical) and the amount of microdamage generated during insertion. MATERIALS AND METHODS Thirty-six cylindrical and 36 tapered MSIs, 6 mm long, were used in this study. Half of each shape was 1.6 mm in diameter, while the other half was 2.0 mm. After pilot drilling, four and five MSIs were inserted, respectively, into fresh cadaveric maxillae and mandibles of dogs. Bone blocks containing the MSIs were sectioned and ground parallel to the MSI axis. Epifluorescent microscopy was used to measure overall cortical thickness, crack length, and crack number adjacent to the MSI. Crack density and total microdamage burden per surface length were calculated. Three-way analysis of variance (ANOVA) was used to test the effects of jaw, and MSI shape and diameter. Pairwise comparisons were made to control the overall significance level at 5%. RESULTS The larger (2.0 vs 1.6 mm) cylindrical MSIs increased the numbers, lengths, and densities of microcracks, and the total microdamage burden. The same diameter cylindrical and tapered MSIs generated a similar number of cracks and crack lengths. More total microdamage burden was created by the 2.0-mm cylindrical than the 2.0-mm tapered MSIs. Although higher crack densities were produced by the insertion of 1.6-mm tapered MSIs, there was no difference in total microdamage burden induced by 1.6-mm tapered and 1.6-mm cylindrical MSIs. CONCLUSIONS Pilot drilling is effective in reducing microdamage during insertion of tapered MSIs. To prevent excessive microdamage, large diameter and cylindrical MSIs should be avoided.