Self-threading Pins Research Articles

External Unilateral Fixator of Own Design for the Treatment of Selected Mandibular Fractures in Horses

Most of the mandibular fractures occur as a result of accidents, kicks, or falls. The treatment of fractures located in the incisor region is quite successful with the use of the wiring method. Fractures that occur within the body of the mandible are more complicated. Some of them are open and infected and involve the cheek teeth, which makes treatment quite challenging. In these cases, using bone plates mounted directly on the bone would constitute poor technique. External skeletal fixators can be a good alternative for treatment of complicated fractures. In this article we present the construction and the possible use of a unilateral external fixator dedicated for the treatment of mandibular body fractures. The fixator consists of one rod having a diameter of 8 mm and a length of 20 cm, four booms, four connectors, and four self-threading apex pins with a diameter of 6 mm. Stainless steel was used in the production of the fixator. The device has been successfully used for the treatment of open mandible fractures. The stabilizer is light and is small in size, simple to use, and easily assembled and disassembled. It can be adjusted in three planes.

Aesthetic Restoration of Traumatized Anterior Teeth

Abstarct : Traumatic dental injuries occuring in anterior teeth is a frequently seen condition in children and adults. The patients are both affected physically and psychologically due to trauma. The traumatized permanent tooth is characterized both as functional impairments for the patients and as a fundamental aesthetical probleme, especially in young patients. The traumatized teeth are generally treated with fiberpost, composite build-up and crown restoration techniques just after the endodontic treatment. In these kinds of cases, the treatment method alone is not sufficient; the case should be approached in a multidisciplinary manner. By this case report, the treatment of comlicated enamel-dentin crown fracture resulting from pulp expansion due to traume that occured in a 18-years-old male patient was aimed. The fractured parts of teeth were restored with self-threading pins ((Self - Threading pins - TMS (Thread-Mate system)). The around of pins was enclosed with fluent composite. Afterwards, a transparent matrix band was adopted to mesial and distan edges of the teeth and was restored using composite resin (Arabesk, Voco, Germany) by layering technique. Finally, the restoration surfaces were polished with finishing discs (Sof-lex,3M ESPE,USA). The patient was evaluated 6 months later and not any fractures or discoloration were observed aesthetically. The prognisis of crown fractures is firstly depend upon periodontal ligament injury status; secondly the duration in which the pulp is left open depends upon dentin surface width and root-growth phase. The optimum treatment results depend upon urgent evaluation and care.

Changes in dentin after insertion of self-threading titanium pins with 3 methods: A scanning electron microscope pilot study

Statement of Problem. Inserting a self-threading pin can cause dentinal cracks, but it is not known whether dentin bonding agents can penetrate these cracks. Purpose. Part I of this in vitro pilot study was conducted to document the presence of dentinal cracks after the placement of self-threading pins with 3 methods. Part II was conducted to observe changes in dentin when a dentin bonding agent was applied before insertion of the self-threading pins. Material and Methods. The crowns of 14 noncarious third molars were sectioned horizontally 2 mm above the cemento-enamel junction, and the occlusal portions were discarded. The teeth were put into a nontransparent bag and divided randomly into 2 groups. Group 1 consisted of 12 teeth. In each tooth, 4 pinholes were prepared with a handpiece at normal rotation speed (30,000 rpm). Self-threading pins were placed into 3 of the pinholes in each tooth: 1 manually, 1 by handpiece at 7000 rpm, and 1 by handpiece at 30,000 rpm. The fourth pinhole was left empty and served as the control. All group 1 teeth were sectioned vertically through the pins, dental hard tissue, and control pin holes. The examination surface of each specimen in group 1 was polished, and the smear layer was removed with Calcinase and NaOCl solutions. After dehydration in ascending grades of alcohol, specimens were coated with a 10- to 15-nm-thick layer of gold and examined with a scanning electron microscope. In the remaining 2 teeth (group 2), a dentin bonding agent was introduced into the pinholes prior to pin placement. Two pins were placed manually and 2 by handpiece at 30,000 rpm. After pin placement, sectioning, cleaning, and dehydration, the specimens were examined with a scanning electron microscope, and x-ray mapping was performed to determine the presence of titanium, silicon, and calcium. Results. Craze lines in dentin were associated with 54.5% of pins placed manually and 54.5% of pins placed with a handpiece at reduced speed (7000 rpm). Dentinal cracks were associated with 50% of pins placed with a handpiece at standard speed and with 16.7% of the control pinholes. X-ray mapping analysis revealed the presence of the dentin bonding agent between the pin and dentin wall. The dentin bonding agent was not found in the dentinal cracks except at the crack orifice. Summary. Within the limitations of this pilot study, the method of pin insertion had no direct bearing on the presence of dentinal cracks. The dentin bonding agent tested did not fill the entire space of dentinal cracks but did occlude their orifices and fill the spaces between pin surface and dentin walls in the pin preparation. (J Prosthet Dent 2002;87:182-8.)

Cortex distraction forces caused by the insertion of external fixator pins.

Insertion of a bicortical threaded external fixator pin can cause bone damage. An unexpected crack can propagate along the bone when the pin touches the far cortex. The objective of this study was to investigate whether drilling and inserting bicortical pins into the shafts of long bones can cause large distraction forces to be generated between the cortices. Two flat samples of bone or bone substitute (Tufnol) were mounted parallel at each end of a specially designed force measurement column. Three common pin designs were inserted into the samples: tapered, self-threading and self-drilling, and self-threading pins. The axial thrust and the cortex distraction force between the two samples were measured as the pins were inserted. High distraction forces were measured between the cortices for all pin designs, typically 700 to 1,000 Newtons. The clinical significance of these findings is that the insertion of bicortical pins of the designs tested may generate a large distraction force between the cortices. This may drive a fracture apart or propagate an undisplaced fracture. Therefore, care must be taken to ensure that bicortical pins are inserted in locations free of local defects.

The performance of bonded vs. pin-retained complex amalgam restorations: A five-year clinical evaluation

The authors compared the clinical performance of complex amalgam restorations, replacing at least one cusp--retained either mechanically with self-threading pins or bonded--with a filled, 4-methacryloxyethyl trimellitate anhydride, or 4-META-based resin designed for amalgam bonding. The authors placed 60 amalgam restorations (28 pin-retained and 32 bonded), each restoration replacing at least one cusp. They used self-threading stainless steel pins in the pin-retained group and a filled, 4-META-based bonding resin in the bonded group. For both groups, the authors left in place any retention form remaining after removal of an old restoration but did not enhance it. At four years, six restorations had failed. At five years, of the 40 restorations available for evaluation, three had failed, for a total of nine failed restorations; seven of those were pin-retained and two were bonded. Using the Fisher exact test to compare the groups at five years, the authors found no significant difference in failure rate, marginal adaptation, marginal discoloration, secondary caries, tooth sensitivity or tooth vitality. At five years, there was no difference in the performance of pin-retained amalgam restorations and bonded amalgam restorations. This study will be continued for at least a sixth year. Bonding with a filled, 4-META-based bonding resin appears to be a satisfactory method of retaining large amalgam restorations replacing cusps.

A new instrument for placement of self-threading retention pins

A new instrument for placement of self-threading retention pins

Ultrasonic removal of dentine pins.

Replacement of pin-retained amalgam restorations is complicated by the loss of prime pin sites and remaining pin sites posing anatomical problems. Self-threading dentine pins can be removed with an ultrasonic handpiece, and the pin site reused with a large pin. Retention of replacement pins is similar to original pins. Pin removal after experimental placement takes a considerable time (< 15 min), but pin removal from extracted pin-restored teeth is much quicker (mean of 45 s). The reuse of primary pin sites allows uncomplicated replacement of pin-retained amalgams, and is a useful clinical technique.

In vitro evaluation of dynamic fluid displacement in dentinal tubules activated on pin placement

The use of cemented, friction-lock, and self-threading pins for improving retention has been essential for treatment in restorative dentistry, with the self-threading pin considered to be the most retentive. Cavity varnish has been suggested to prevent microleakage around pins. This study investigated the insertion of a self-threading pin when the pinhole was filled with a liquid dye. The results showed that pinholes filled with dye before pin placement had measurable dye displacement. Pinholes without pins displayed no measurable dye displacement through the dentin; this was also true when the dye fluid was removed before the pin placement. However, the dye in pinholes was displaced toward the path of least resistance, and fluid in a pinhole can contribute to crazing of the dentin during placement.

A drilling technique to improve the retention of self-threading pins

This study determined the effect of a modification of the drilling technique on the retention of self-threading pins. The drilling technique in two stages significantly increased the retention of self-threading pins.

Fracture resistance of composite and amalgam cores retained by pins coated with new adhesive resins

This study determined the effects of coating pins with either Panavia EX or with 4-META (Cover-Up) materials on the fracture resistance of pin-retained amalgam and composite cores. Gold-plated stainless steel (TMS) and titanium (Filpin) self-threading pins were used. Findings of this study corroborated the findings of several other studies that the use of pins reduces the fracture resistance of restorations. However, coating the pins with adhesion promoters such as Panavia EX and 4-META materials has been found to be effective in improving the fracture resistance. Cross-preference was observed between TMS and Filpin pins; that is, Panavia material coating was more effective with TMS pins, while 4-META was more effective with Filpin pins.

Pulpal response to threaded pin and retentive slot techniques: A pilot investigation

This investigation compared pulpal response to threaded pin techniques with response to retentive slot techniques. The teeth were restored with composite resin. Twenty-four teeth were assigned to three treatment groups in one Macaca mulatta monkey. Ten teeth (group 1) received 32 TMS 0.021-inch self-threading pins. Ten teeth (group II) received circumferential slot retention 1 mm deep, 0.5 mm inside the dentinoenamel junction. Four teeth (group III) served as controls. Groups I and II were restored with composite resin. Fourteen days later, the teeth were removed, demineralized, serially sectioned, and stained with hematoxylin and eosin. Chi-square analysis indicated more pulp inflammation when self-threading pins were used ( p < 0.5). Pins placed within 0.5 mm of the pulp elicited severe inflammatory responses, and those placed further than 1 mm had minimal effect. Little correlation existed between remaining dentin thickness and adverse pulp response when slot retention was used.

Pinhole preparation for self-threading pins

The force required to remove self-threading retention pins from dentin when the holes were drilled with two different methods was determined. The two methods employed to drill the holes were (1) using a conventional slow-speed contra-angle handpiece and (2) using a 10-to-1 gear reduction contra-angle handpiece attached to a conventional slow-speed handpiece. Also determined were the number of drills broken in the process of drilling the holes. Results demonstrated no difference in the retention of pins placed in holes drilled using these two methods. Two drills were broken in the process of drilling well over 100 holes, and both breaks occurred with the gear-reduced handpiece. Either of the two methods tested is acceptable, but we recommended using a conventional slow-speed contra-angle handpiece because of the ease of producing the holes.

Retention of threaded pins in amalgam

The force required to remove three self-threading retention pins from amalgam and the pin length for optimum retention was determined. Link series TMS Minuta, TMS Minikin, and TMS Minim pins were tested; Minim pins were tested at various lengths. The amalgam materials used were representative of a high-copper admixture type and a ternary spherical-type alloy. Results demonstrate that the Minim pin of 2 to 2.5 mm length is the optimum pin for retention in high-copper type amalgam. Minuta and Minikin pins are removed with only a small amount of force and should be used only when clinical prudence requires a small pin; and when used, the strongest possible amalgam should be selected.

The retention of self-threading pins embedded invisible light-cured composites

Tensile force was applied to self-threading dentine pins embedded in cylinders of lightcured composite and the failure force determined. Failures were similar to those found in autopolymerized composite, and depended upon both the fracture toughness of the composite and the pin thread geometry. In addition, shadowing of the curing light by the pin reduced the effectiveness of the pins. Most effective retention was obtained when pins with a wide pitch thread were used in combination with the toughest composites.

Retention of self-threading pins with reduced stress from insertion

Retention of self-threading pins with reduced stress from insertion

The retention of self-threading pins embedded in various restorative materials.

Abstract The retention of restorative materials by dentine pins has been investigated using specimens in which pins were embedded to a clinically realistic depth in a volume of material which corresponded to that for a posterior restoration. One week after preparation a tensile force was applied to the pin, and the failure value and failure mode recorded. Two commercial pins of identical size but contrasting thread geometries and a range of amalgam and composite products were selected. Specimens containing pins with a broad pitch thread failed primarily by fracture through the material at force levels above those for specimens containing pins with a conventional close-pitch tread. These failed by the pin pulling out. A strong correlation was found between the failure force for the former specimens and the fracture toughness (K IC ) of the embedding material. For one product the fracture toughness was sufficient to resist the applied force and tensile failure of the pin took place as an alternative failure mechanism.

Photoelastic analysis of stress induced from insertion of self-threading retentive pins

W hen teeth have lost significant amounts of their original structure, it is common to use pins as auxiliary support for the restorative material. Three basic systems are used for the retention of auxiliary pins: (1) cement (threaded or nonthreaded pins are luted into a prepared channel that is slightly larger in diameter than the pin); (2) friction (nonthreaded, tapered pins are forced into a channel that is slightly smaller than the pin); and (3) threads (threaded pins are twisted into a channel that is prepared slightly smaller in diameter than the pin).’ Of the three systems, self-threading pins are used most frequently because of their *excellent retentive properties.2 However, teeth may be damaged as a result of their use; cracking and crazing of dentin has been observed in association with insertion of self-threading retentive pins in extracted teeth.3 Two-dimensional photoelastic models have been used to observe stresses associated with the placement of various kinds of loads on the three types of retentive pin systems and to investigate stress concentrations associated with pin-retained amalgam restorations.4a 5 A photoelastic study that specifically evaluated the self-threading self-shearing retentive pin has shown the presence of high stress zones in the lateral and most apical portions of the pin channel; the apical zone exhibits the most stress.6 It is important to minimize the stresses induced during placement of pins because of the relatively small amount of tooth structure between the pulp and the external tooth surface. It is particularly important that the high stress zone be minimized to reduce the potential risk of fracture and resultant pulpal involvement or tooth failure, The goal of effective pin placement should be adequate retention with elimination of the high stress zone.

Comparative stress effects of vented and nonvented self-threading retentive pins

Longitudinally vented self-threading pins do not demonstrate a significant improvement in the complete seating of the pins or a decrease of dentinal crazing. The link series technique does demonstrate a significant improvement in the complete seating of pins and in the prevention of misalignment of the pins with the channels.

Clinically significant factors in dowel design

When a method of intracoronal reinforcement is selected, many factors must be weighed. The hazards include (1) the induced stresses and the risk of fracture during placement of the dowel, (2) the probability of root perforation during post space preparation, (3) the wedging action of tapered dowels, and (4) the incidence of fracture with self-threading pins in devitalized teeth. The amount of tooth structure that remains after endodontic therapy and post space preparation is paramount. Endodontic and restorative treatment must be aimed at preserving tooth structure to provide strength and resistance to fracture of the pulpless tooth. To fabricate a large-diameter dowel with a strength that greatly exceeds that of the endodontically treated root decreases the prognosis for clinical success.

Self-threading pin penetration into dentin

A laboratory study has shown that the first-half of self-shearing 2-in-1 self-threading pins, sizes 0.031 inch and 0.024 inch, fail to reach full channel depth when placed with either a hand wrench or an Auto Klutch handpiece. The average discrepancy of penetration is about 0.75 mm. This discrepancy in seating results in a significant excess pin length extending into the tooth preparation, which compromises the strength characteristics of the amalgam restoration.