Solid Screw Research Articles

Comparison of two early loading protocols in full arch reconstructions in the edentulous maxilla using the Cresco prosthetic system: a three-arm parallel group randomized-controlled trial

Appraise the feasibility of interchanging conventional components of a fixed dental prosthesis (FDP) with those of Cresco in two different early loading protocols. In five centers patients with an edentulous, fully healed maxilla were recruited to partake in a three-arm blinded randomized-controlled trial (RCT). Each patient received 5/6 implants using a single-stage surgery approach to support a 10/12-unit FDP. The implants used were SLA solid screw two-part implants. In test groups 1 and 2 components from Cresco were used and the implants loaded 10 days or 6-8 weeks post-implant placement. Group 3 received their FDP fabricated with conventional components 6-8 weeks post-implant placement. Patients were followed up 3 years. Of 36 patients, 30 remained after 3 years. The adjusted means and ranges of changes in crestal bone levels were -0.65, -0.5 and -0.4 mm in groups 1, 2 and 3, respectively. The change from baseline was statistically significant in all treatment groups. Adjusting for the difference in implant depth, there was an expected additional change in bone level of -0.29 mm by each 1 mm the implant was placed deeper. There was no significant difference between the 6-8 weeks post-implant placement loading Cresco group vs. the control group or between the two Cresco groups. The vertical placement has more effect on bone loss than the fabrication technique used for the suprastructure and whether the implants were loaded after 10 days vs. 6-8 weeks.

Accuracy of CT-assisted pedicle screw placement after CT-controlled, presurgical guide wire implantation in traumatic and pathological fractures in the thoracic spine.

The aim of this study was to evaluate the accuracy of pedicle screw placement after computed tomography (CT)-assisted positioning of guide wires and subsequent insertion of transpedicular screws in particularly narrow pedicles in the thoracic spine. Transpedicular pedicle screw placement has been commonly used for a number of decades. However, a significant number of malpositioned screws still occur, especially in the thoracic spine, potentially correlating with relevant complications, e.g., neurological deterioration. A retrospective analysis was performed after CT-assisted and -controlled implantation of guide wires into the pedicle. A total of 39 patients underwent dorsal spondylodesis using two different internal fixation systems, i.e., with a cannulated or a solid screw design. The postoperative screw position was evaluated with CT scans in three planes in a total of 254 screws. The number of the screws inserted at each level were as follows (total n=326): T1, n=8; T2, n=26; T3, n=26; T4, n=36; T5, n=50; T6, n=37; T7, n=38; T8, n=32; T9, n=24; T10, n=18; T11, n=10; T12, n=6. Indications for the operative treatment were fractures, tumors, and infectious diseases. A total of 254 screws inserted were evaluated by CT scan in order to determine the screw position inside the pedicle and potential perforation of the pedicle wall. The overall rate of pedicle wall perforation was 7.5%, including 1.2% perforations of the medial wall. A significant correlation between the perforation rate and the type of fixation system in favor of the cannulated system was found (P=0.033). During the study, no revision surgery due to screw misplacement was necessary. None of the treated patients showed neurological deterioration after screw implantation during the presented study. The CT-assisted pedicle screw implantation procedure using guide wires implanted prior to surgery is an accurate, reliable, and safe method for dorsal spondylodesis in the treatment of a variety of spinal instabilities, including fractures, tumors, and infections.

Influence of a multiplicative noise on the threshold of helical dynamo

We study the effect of stochastic velocity fluctuations on the generation of magnetic field by a helical flow made of a mean steady flow plus a fluctuating flow assumed to behave like a Gaussian white noise. We calculate analytically, the threshold shift and the frequency shift induced by fluctuations of small amplitude that are geometrically optimized. It is found that the threshold is lowered, provided the steady part of the flow represented by a solid body screw motion with constant pitch satisfies the condition where m and k, respectively, are the axial and azimuthal wavenumbers of the magnetic field such that m = −k = 1. When there is no mean flow we extend the analysis to fluctuations with a finite correlation time and find that the dynamo threshold is higher than for a steady flow with the same geometry.

Effects of different fixture geometries on the stress distribution in mandibular peri-implant structures: a 3-dimensional finite element analysis

The purpose of this study was to compare 3 different solid screw implant fixture designs of stepped cylindric tapered, straight cylindric nontapered, and cylindric with vertical groove tapered on stress distribution in the posterior mandible at a fixed interimplant distance of 1.0 cm. Three-dimensional finite element analysis was used to compare stress distribution around the endosseous titanium implants using 3 different implant fixture geometries. Two identical dental implants of 3 commercially available fixture designs were embedded in each model with a fixed interimplant distance of 1.0 cm. Loads were applied to each of these fixtures: vertically 70 N, with an inclination of 60 degrees obliquely (buccolingually) 35 N, and horizontally (mesiodistally) 14 N. Tensile and compressive stresses on each simulated mandible were calculated using finite element analysis software. Finally, evaluation of the stress around 3 different implant fixtures was performed. In the vertical and buccolingual directions, the highest tensile stresses (P(max)) and compression stresses (P(min)) mostly occurred around the cylindric with vertical groove tapered fixture design in both cortical and cancellous bone. In mesiodistal direction, the highest P(max) and P(min) values in cortical and cancellous bone mostly occurred around the straight cylindric nontapered fixture design. On the basis of the knowledge of deterioration of osseointegration under undesirable stresses within the surrounding bone, the implant fixture design should be chosen carefully. The results of this study reveal that in a clinical situation of molar edentulism, 2 identical stepped cylindric fixture designs which were embedded at a fixed distance of 1.0 cm were the most desirable choice of stress distribution in the surrounding bone.

Screw loosening in the Dynesys stabilization system: radiographic evidence and effect on outcomes

Dynamic stabilization systems are used to stabilize degenerative lumbar spondylosis. Loosening of the pedicle screws in such nonfusion implants is predictable. This retrospective study evaluated the incidence of screw loosening and its effect on clinical outcomes. Charts, radiographic films, and medical records of 71 consecutive patients who underwent decompression using Dynesys dynamic stabilization for 1- or 2-level lumbar spondylosis were reviewed. Radiographic films were evaluated and compared to detect screw loosening. A visual analog scale (VAS) for back pain and the Oswestry Disability Index (ODI) were used for measuring clinical outcome. Statistical analysis was conducted using the chi-square test and Student t-test. The 71 patients in the study sample had a mean age of 59.2 +/- 11.65 years (range 23-80 years), with slight female predominance (39 women, 32 men). The mean follow-up duration was 16.6 months (range 8-29 months). There were loose screws in 14 of 71 patients (19.7%), for a rate of 4.6% per screw (17 of 368 screws). Most screw loosening occurred in patients >/= 55 years old (13 of 14 patients) although age and sex had no effect on screw loosening (p = 0.233 and 0.109, respectively). Both the loose screw and solid screw groups experienced significant improvement after the surgery in VAS and ODI scores. On the VAS, scores improved from 5.9 +/- 2.99 to 2.1 +/- 2.14 in the loose screw group (p = 0.003), and from 5.7 +/- 3.45 to 2.9 +/- 2.68 in the solid screw group (p < 0.001). For the ODI scale, scores improved from 43.5 +/- 16.78% to 28.0 +/- 18.18% (p = 0.006) in the loose screw group, and from 52.1 +/- 20.92% to 24.6 +/- 19.78% (p < 0.001) in the solid screw group. There were no significant differences between the 2 groups (p = 0.334 for VAS, p = 0.567 for ODI). The preliminary study of this pedicle-based dynamic stabilization device for 1- and 2-level lumbar spondylosis shows radiographic evidence of screw loosening in 19.7% of patients and 4.6% of screws. Nonetheless, the loosening of screws has no adverse effect on clinical improvement.

The effect of thread design on stress distribution in a solid screw implant: a 3D finite element analysis

The biomechanical behavior of implant thread plays an important role on stresses at implant-bone interface. Information about the effect of different thread profiles upon the bone stresses is limited. The purpose of this study was to evaluate the effects of different implant thread designs on stress distribution characteristics at supporting structures. In this study, three-dimensional (3D) finite element (FE) stress-analysis method was used. Four types of 3D mathematical models simulating four different thread-form configurations for a solid screw implant was prepared with supporting bone structure. V-thread (1), buttress (2), reverse buttress (3), and square thread designs were simulated. A 100-N static axial occlusal load was applied to occlusal surface of abutment to calculate the stress distributions. Solidworks/Cosmosworks structural analysis programs were used for FE modeling/analysis. The analysis of the von Mises stress values revealed that maximum stress concentrations were located at loading areas of implant abutments and cervical cortical bone regions for all models. Stress concentration at cortical bone (18.3 MPa) was higher than spongious bone (13.3 MPa), and concentration of first thread (18 MPa) was higher than other threads (13.3 MPa). It was seen that, while the von Mises stress distribution patterns at different implant thread models were similar, the concentration of compressive stresses were different. The present study showed that the use of different thread form designs did not affect the von Mises concentration at supporting bone structure. However, the compressive stress concentrations differ by various thread profiles.

Rigid Stabilization of Partial Incongruous Lisfranc Dislocations: A Cannulated Solid Screw Technique

For several years, there has been much controversy over the optimal form of fixation in the operative treatment of Lisfranc injuries. Both cortical and cannulated screws have been widely used in the treatment of these injuries. The level of technical difficulty and reproducible accuracy of the cannulated screw system has gained much popularity. In comparison, the rigid stability of cortical screws appears more favorable. The authors present a cannulated technique utilizing a single 4.0 mm cortical screw (Synthes USA Paoli, Pa.). In Lisfranc injuries with partial incongruity, this method allows precise screw placement while maintaining rigid solid screw stabilization. The technique is minimally invasive, provides anatomical restoration and allows early return to functional activity.

A Prospective Multicenter 5‐Year Radiographic Evaluation of Crestal Bone Levels Over Time in 596 Dental Implants Placed in 192 Patients

Dental implants have been used to replace missing teeth to provide function and esthetics. One goal of such restorations is to maintain host tissue around the implants. The purpose of this prospective multicenter human clinical trial was to evaluate radiographic marginal bone levels around non-submerged hollow cylindrical and solid-screw implants for 5 years after loading. Patients older than 18 years of age with sufficient native bone to surround a dental implant without imposing on a vital structure were recruited at five sites. Solid-screw or hollow-cylinder implants with a titanium plasma-sprayed implant surface were placed in the anterior maxilla or anterior mandible and restored with fixed restorations. Baseline radiographs were taken at the time of implant placement. Subsequent radiographs were taken at the time of final prosthesis placement, at 6 months after prosthesis placement, and annually from prosthesis placement for 5 years. The results of 596 implants in 192 patients at five international sites revealed that clinically significant remodeling of the marginal bone occurred during the first 6 months after implant placement, with a mean (+/- SD) marginal bone loss of 2.44 +/- 1.20 mm. After that, clinically insignificant mean changes in the bone were observed. Overall, 0.22 +/- 0.42 mm of bone loss occurred between the time of prosthesis placement and 1-year postloading. Between 1-year postloading and the last 5-year recall, 0.18 +/- 0.88 mm bone loss occurred. Because 2.84 +/- 1.63 mm of bone loss occurred between implant placement and the 5-year postloading follow-up, 86% of the total mean bone loss over the course of 5 years was accounted for at the time of prosthesis placement. These same trends occurred if the data were analyzed with regard to implant design (solid screw and hollow cylinder), type of restoration (single and multiple), and length of implant (8 to 10, 12, and 14 to 16 mm). These data demonstrate that, in general, clinically significant marginal bone remodeling occurred between the time of implant placement and final prosthesis placement around one-stage non-submerged titanium implants with a titanium plasma-sprayed surface. Subsequent to that, bone loss observed around implants up to 5 years postloading was minimal. These results suggest that the factors that influence early healing around implants are significantly different from those that affect later marginal bone remodeling.

Histomorphometry and stability analysis of early loaded implants with two different surface conditions in beagle dogs

STATEMENT OF PROBLEMDespite an improved bone reactions of Mg-incorporated implants in the animals, little yet has been carried out by the experimental investigations in functional loading conditions.PURPOSEThis study investigated the clinical and histologic parameters of osseointegrated Mg-incorporated implants in early loading conditions.MATERIAL AND METHODSA total of 36 solid screw implants (diameter 3.75 mm, length 10 mm) were placed in the mandibles of 6 beagle dogs. Test groups included 18 Mg-incorporated implants. Turned titanium implants served as control. Gold crowns were inserted 4 weeks after implant placement and the dogs were immediately put on a food diet. Implants were observed for 10 weeks after loading. Radiographic assessments and stability tests were performed at the time of fixture installation, 2nd stage surgery, 4 weeks after loading, and 10 weeks after loading. Histological observations and morphometrical measurements were also performed.RESULTSOf 36 implants, 33 displayed no discernible mobility, corresponding to successful clinical function. There was no statistically significant difference between test implants and controls in marginal bone levels (P = .46) and RFA values. The mean BIC% in the Mg-implants was 54.5 ± 8.4%. The mean BIC% in the turned implant was 45.3 ± 12.2%. These differences between the Mg-implant and control implant were statistically significant (P = .005).CONCLUSIONSThe anodized, Mg-incorporated implant demonstrated significantly more bone-to-implant contact (BIC) in early loading conditions.CLINICAL IMPLICATIONSThe results of this study in beagle dogs suggest the possibility of achieving predictable stability of early loaded free-standing dental implants with Mg-incorporated surface.

Assessment of different screw augmentation techniques and screw designs in osteoporotic spines

This is an experimental study on human cadaver spines. The objective of this study is to compare the pullout forces between three screw augmentation methods and two different screw designs. Surgical interventions of patients with osteoporosis increase following the epidemiological development. Biomechanically the pedicle provides the strongest screw fixation in healthy bone, whereas in osteoporosis all areas of the vertebra are affected by the disease. This explains the high screw failure rates in those patients. Therefore PMMA augmentation of screws is often mandatory. This study involved investigation of the pullout forces of augmented transpedicular screws in five human lumbar spines (L1-L4). Each spine was treated with four different methods: non-augmented unperforated (solid) screw, perforated screw with vertebroplasty augmentation, solid screw with vertebroplasty augmentation and solid screw with balloon kyphoplasty augmentation. Screws were augmented with Polymethylmethacrylate (PMMA). The pullout forces were measured for each treatment with an Instron testing device. The bone mineral density was measured for each vertebra with Micro-CT. The statistical analysis was performed with a two-sided independent student t test. Forty screws (10 per group and level) were inserted. The vertebroplasty-augmented screws showed a significant higher pullout force (mean 918.5 N, P = 0.001) than control (mean 51 N), the balloon kyphoplasty group did not improve the pullout force significantly (mean 781 N, P > 0.05). However, leakage occurred in some cases treated with perforated screws. All spines showed osteoporosis on Micro-CT. Vertebroplasty-augmented screws, augmentation of perforated screws and balloon kyphoplasty augmented screws show higher pullout resistance than non-augmented screws. Significant higher pullout forces were only reached in the vertebroplasty augmented vertebra. The perforated screw design led to epidural leakage due to the position of the perforation in the screw. The position of the most proximal perforation is critical, depending on screw design and proper insertion depth. Nevertheless, using a properly designed perforated screw will facilitate augmentation and instrumentation in osteoporotic spines.

Comparing the Fixation of a Novel Hollow Screw Versus a Conventional Solid Screw in Human Sacra Under Cyclic Loading

The loosening rates of two monocortical pedicle screw designs (hollow and solid) were compared in a cadaveric sacrum model subjected to cyclic loading. To determine if a hollow screw would be more resistant to loosening than a solid pedicle screw when placed into the pedicles of S1 and tested under stair-cased cyclic loading. Screw loosening is a clinical problem for lumbosacral fusions. No previous literature has evaluated the use of a monocortical hollow screw within the sacrum; however, in other vertebral bodies, results of using this screw have been varied. Seven fresh-frozen cadaveric sacra were thawed and stripped of soft tissues. Solid and hollow screws were inserted contralaterally into the pedicles of S1. A materials testing machine applied alternating flexion and extension bending moments at 1 Hz, to each screw independently, via a standard connecting rod. Flexion moments were applied starting at 0.5 Nm and increased by 0.5 Nm after every 1000 cycles until the screw had visibly failed. Extension moments were maintained at 0.5 Nm. Screw rotation (flexion) relative to the sacrum was recorded using a custom optical tracking system, and analyzed using 2-way repeated measures analyses of variances and post hoc Student-Newman-Keuls tests (alpha = 0.05). Screw rotation tended to gradually increase to six degrees, after which the screw was grossly loose. Overall, the hollow screw required fewer loading cycles (P = 0.004) and less applied moment (P = 0.003) to achieve the same magnitude of screw rotation as the solid screw. To achieve 6 degrees of screw rotation, the number of loading cycles were 6301 +/- 2161 and 11151 +/- 4221 for hollow and solid screws, respectively. The corresponding applied moments were 3.5 +/- 1.0 Nm and 5.8 +/- 2.0 Nm. CONCLUSION.: The novel hollow screw was less resistant to loosening when compared with a conventional solid pedicle screw in this sacral model under cyclic loading.

Missing osteogenic effect of expanded autogenous osteoblast‐like cells in a minipig model of sinus augmentation with simultaneous dental implant installation

With natural bovine bone mineral (BioOss) as carrier, the study aimed at investigating the effect of autogenous osteoblast-like cells on bone regeneration in an orthotopic (maxillary sinus) and an ectopic (muscle) site. Autogenous osteoblast-like cells were isolated from iliac cancellous bone of six minipigs and expanded in an autogenous serum-supplemented osteogenic medium. After confirmation of osteogenicity, the expanded cells were precultivated on BioOss granules for 1 week. Four milliliter of cell-seeded BioOss were used for sinus augmentation of right sinus and a Straumann solid screw (dental) implant was simultaneously installed. The contralateral (control) side was filled with cell-free BioOss. Besides, 2 ml of the corresponding granules were placed in a pouch in the latissimus dorsi muscles bilaterally. Polychrome sequential labeling was performed postoperatively. Specimens were harvested at week 6. Undecalcified sections were evaluated with microradiography, fluorescence microscopy, histology and histomorphometry. In the test side, the coronal part of dental implant demonstrated higher bone-implant contact (BIC) than the apical part (34.88+/-28.86% vs. 16.68+/-13.80%, P=0.039), as well as higher bone density (BD) in the corresponding zone (14.88+/-6.37% vs. 11.10+/-4.54%, P=0.021). However, the test side demonstrated no advantage over control side in either BD (12.25+/-4.22% vs. 8.45+/-11.04%, P=0.473) or BIC (24.15+/-21.97% vs. 22.05+/-19.00%, P=0.270). Rare bone was formed in the muscles in both sides. The expanded autogenous osteoblast-like cells failed to enhance bone formation in the minipig model of sinus augmentation.

Parameters of resonance frequency measurement values: a retrospective study of 385 ITI dental implants

There is no proven clinical tool to evaluate the amount of osseointegration and stability around dental implants. Therefore, the aim of this retrospective clinical study was to evaluate resonance frequency analysis values of 385 ITI solid screw implants. Both at implant placement and after healing, implant stability quotients (ISQs) were determined. For statistical analysis, Pearson's correlation coefficients, Welch's two-sample t-tests and paired samples t-tests were computed at a level of significance of alpha=0.05. ISQ values ranged from 39 to 86 at implant placement and from 35 to 89 after healing, showing a significant increase. The highest ISQ values at both stages were obtained in the posterior mandible (P < or = 0.002). After healing, ISQ values in the anterior mandible were significantly higher than in the anterior maxilla (P=0.005). Implant length had a significant influence on ISQ in the anterior mandible (P=0) at insertion and in the anterior (P=0.005) and posterior mandible (P=0.036) after healing. Implant diameter and ISQ at insertion correlated in the anterior mandible (P=0.037). After healing, a significant influence was found for all regions, except the posterior maxilla (P=0.795). With the exception of the anterior maxilla (P=0.542), ISQ at placement had a significant influence on ISQ after healing. In the anterior maxilla (P=0.002) and in the posterior mandible (P=0.007), healing time significantly influenced ISQ after healing. It appears that only repeated ISQ measurements of a specific implant have some diagnostic benefit, although the parameters influencing the absolute values still remain unclear.

Lead Pig for Use with Screw Cap Vials

A lead pig specifically designed for use with solid screw cap vials is described. The salient features of this design include a compressible polyethylene sleeve, which is housed in the lower section of the pig, and a partially recessed O-ring, which is housed in the upper section of the pig. These features permit both the vial and the cap to be secured independently without the risk of overtightening. Fingertip radiation exposure associated with repetitively opening and closing a screw cap vial containing a sample of (18)F was monitored by use of a fingertip dosimeter. The cumulative fingertip radiation exposure resulting from opening and closing a screw cap vial containing 200 MBq of (18)F-FDG 3 times was 307 muSv without the aid of this lead pig, as compared with 6 muSv when using this device. Use of this lead pig with screw cap vials can significantly reduce fingertip radiation exposure and decrease the likelihood of accidental radioactive contamination of research personnel.

Surface area analysis of dental implants using micro‐computed tomography

In this study, we present and evaluate a micro-computed tomography (micro-CT)-based method for the calculation of the potential bone/implant contact area (p-BICA) on the surface of dental implants. For seven commercially available implants (Ankylos implant, Brånemark System, Frialit CELLplus, Replace((R)) Select Tapered, Straumann Solid screw, XiVE S CELLplus, 3i Osseotite XP Threaded Miniplant, the p-BICA surface is determined by means of three-dimensional X-ray computed-tomography and computer-based data processing. Measurements were repeated two times, and the stability and repeatability of the measurement method were evaluated. Our analysis revealed a p-BICA of 118 mm(2) for the XiVE S CELLplus implant, 134 mm(2) for the Ankylos, 136 mm(2) for the Frialit CELLplus, 138 mm(2) for the Brånemark System, 139 mm(2) for the Replace((R)), 159 mm(2) for the 3i Osseotite XP and 199 mm(2) for the Straumann Solid screw implant. The measurement method proved to be stable and led to reproducible results. The micro- and macrostructure of dental implants define the surface and the p-BICA. Precise determination of this parameter can be achieved by means of the micro-CT-based method as presented in this study. The value of p-BICA lies in the predictability of industrial design before preclinical and clinical testing. Based on this method, dental implant properties become comparable even if geometrical details are not disclosed by the manufacturer.

Quality and quantity of bone following alveolar distraction osteogenesis in the human mandible

The purpose of this prospective study on humans were to evaluate (a) the clinical outcome of alveolar distraction osteogenesis for the correction of vertically deficient edentulous mandibular ridges, (b) the clinical outcome of dental implants placed in the distracted areas, and (c) the quality and quantity of the bone that had formed in the distraction gap. Seven patients presenting vertically deficient edentulous ridges were treated by means of distraction osteogenesis with an intraoral alveolar distractor. Approximately 3 months after consolidation of the distracted segments, 20 ITI solid screw SLA implants were placed in the distracted areas. Three to 4 months later, abutments were connected and prosthetic loading of the implants started. During implant site preparation, bone biopsies were taken at the implant sites with trephine burrs for histologic and histometric analyses. The mean follow-up after the initial prosthetic loading was 18 months (range 12-24 months). The mean bone gain obtained at the end of distraction was 7 mm (range 5-9 mm). The cumulative success rate of implants 2 years after the onset of prosthetic loading was 95%, whereas the survival rate of implants was 100%. The newly formed bone consisted of woven bone reinforced by parallel-fibered bone with bone marrow spaces between the bone trabeculae. The bone area fraction in the distraction region ranged from 21.6% to 57.8% (38.5+/-11.7%). Results from this study showed that (a) distraction osteogenesis is a reliable technique for the correction of vertically deficient edentulous ridges, (b) the regenerated bone withstood the functional demands of implant loading, (c) survival and success rates of implants placed in the distracted areas were consistent with those of implants placed in native bone, and (d) there is sufficient bone volume and maturity in the distracted region for primary stability of the implant.

Implant design and intraosseous stability of immediately placed implants: a human cadaver study

The objective of this study was to explore effects of implant macrodesign and diameter on initial intraosseous stability and interface mechanical properties of immediately placed implants. Mandibular premolars of four fresh-frozen human cadavers were extracted. Ø 4.1/4.8 mm ITI TE, Ø 4.1 and 4.8 mm solid screw synOcta ITI implants were placed into freshly prepared extraction sockets. Resonance frequency analysis was conducted to quantify primary implant stability quotient (ISQ). Installation torque value (ITV) and removal torque value (RTV) of the implants were measured using a custom-made strain-gauged torque wrench connected to a data acquisition system at a sample rate of 10,000 Hz. The vertical defect depth around the collar of each implant was measured directly by an endodontic spreader. The bone-implant contact was determined in digitalized images of periapical radiographs and expressed as percentage bone contact. The ISQ values of the TE implant was higher than the Ø 4.1 mm implant (P<0.01), and comparable with the Ø 4.8 mm implants (P>0.05). ITVs and RTVs of TE and Ø 4.8 mm implants were higher than the Ø 4.1 mm implant, although the differences between groups were statistically insignificant (P>0.05). The vertical defect depths around all types of implants were similar. In the radiographic analyses, percentage bone-implant contact of the TE and Ø 4.8 mm implants were comparable at the marginal bone region and both were higher than that of the Ø 4.1 mm ITI implant. Nonparametric correlations between groups revealed a significant correlation between ITV and RTV (r=0.838; P<0.001), but not between ISQ values and ITVs and RTVs (P>0.05). Immediately placed ITI TE implant leads to initial intraosseous stability and interface mechanical properties comparable with a wide diameter implant.

Mandibular two-implant telescopic overdentures.

To stabilize mandibular overdentures in edentulous patients, various connector types which can be attached to between two and four implants placed in the anterior mandible are possible. Treatment using non-rigid telescopic connectors on two interforaminal implants for overdenture stabilization began in 1989. The objective of this study is to investigate soft- and hard-tissue conditions as well as prosthesis function after a period of 10 years. This also involved an evaluation of correlations between radiographic and clinical parameters. Twenty-three subjects with 46 interforaminal implants (ITI solid screw implants, 12 mm in length, 4.1 mm in diameter; 10.4 years in situ, range, 8-12.8 years) were investigated. Modified plaque index (mPI), sulcus fluid flow rate (SFFR), modified sulcus bleeding index (mBI), probing depth (PD), distance from implant crown margin to the coronal border of the peri-implant mucosa (DIM), attachment level (AL), width of keratinized mucosa (KM), Periotest values (PTVs) and prosthesis function were evaluated. In the radiographic evaluation, the distance between implant shoulder and first crestal bone-implant contact (DIB) in mm and the horizontal bone loss (HBL) in mm were measured. The relatively high mPI scores (mean, 0.82; score, 0 in 44.4%; SD, 0.83) did not result in increased SFFR scores (mean, 12; min, 3, max, 38; SD, 7.43) or higher mBI scores (mean, 0.35; score, 0 in 70.8%; SD, 0.59), which was commensurate with healthy peri-implant mucosa. A mean PD value of 2.15 mm (min, 1 mm; max, 5 mm; SD, 0.96) and a mean DIM value of 0.28 mm (min, 0 mm; max, 2 mm; SD, 0.52) were measured. The implants were stable, showing a mean Periotest value of -1.91 (max, 02, min, -6; SD, 1.76). A mean DIB of 3.19+/-0.95 mm (range, 1.3-5.16 mm) and a mean HBL of 1.6+/-1.52 mm (range, 0.28-8.33 mm) were calculated. A correlation was found between DIB and the parameters SFFR (P=0.060), DIM (P=0.042), AL (P=0.050) and especially PTV (P<0.01), leading to the assumption that these clinical parameters may be useful indicators of peri-implant bone loss. The results of the 10-year follow-up examination show that non-rigid telescopic connectors with two interforaminal implants for overdenture stabilization appear to be an efficient and effective long-term treatment modality in severely resorbed edentulous mandibles. Particularly in geriatric patient treatment this concept may provide advantages in terms of handling, cleaning and long-term satisfaction.

Early bone formation adjacent to rough and turned endosseous implant surfaces. An experimental study in the dog.

To validate a proposed model (Berglundh et al. 2003) and to evaluate the rate and degree of osseointegration at turned (T) and sand blasted and acid etched (SLA) implant surfaces during early phases of healing. The devices used for the study of early healing had a geometry that corresponded to that of a solid screw implant with either a SLA or a T surface configuration. A circumferential trough had been prepared within the thread region (intra-osseous portion) that established a geometrically well-defined wound chamber. Twenty Labrador dogs received totally 160 experimental devices to allow the evaluation of healing between 2 h and 12 weeks. Both ground and decalcified sections were prepared from mesial/distal and buccal/lingual device sites. Histometric and morphometric analyses of the ground sections and morphometric analysis of the tissue components in decalcified sections were performed. The ground sections provided an overview of the various phases of tissue formation, while the decalcified, thin sections enabled a more detailed study of events involved in bone tissue modeling and remodeling for both SLA and T surfaces. The initially empty wound chamber became occupied with a coagulum and a granulation tissue that was replaced by a provisional matrix. The process of bone formation started already during the first week. The newly formed bone present at the lateral border of the cut bony bed appeared to be continuous with the parent bone, but on the SLA surface woven bone was also found at a distance from the parent bone. Parallel-fibered and/or lamellar bone as well as bone marrow replaced this primary bone after 4 weeks. In the SLA chambers, more bone-to-device contact, more initial woven bone and earlier lamellar bone formation was found than in the T chambers. Osseointegration represents a dynamic process both during its establishment and its maintenance. While healing showed similar characteristics with resorptive and appositional events for both SLA and T surfaces, the rate and degree of osseointegration were superior for the SLA compared with the T chambers.

A technique for proximal first metatarsal osteotomy for hallux valgus repair

Multiple surgical procedures and first metatarsal osteotomy techniques have been described for the repair of hallux valgus deformities. Mild deformities can be corrected by soft-tissue procedures alone or with distal osteotomies. Deformities with larger 1-2 intermetatarsal angles require more proximal first metatarsal osteotomies. Commonly described proximal osteotomies include the crescentic (1), long oblique (2, 3), triplanar (4), closing wedge (5), and proximal chevron (6). Although all of these procedures have been reported to have clinical and radiographic success, each has certain technical difficulties. The crescentic osteotomy is susceptible to dorsiflexion (1, 6–9). In addition, screw fixation is not perpendicular to the osteotomy and may be apt to cross into the first metatarsocuneiform joint. Long oblique osteotomies may slide proximally and shorten (8). The triplanar osteotomy is technically difficult and may split the first metatarsal (10). Collapse of the metatarsal fragments leading to loss of height has also been reported (11). Resecting the preferred amount of bone can be difficult with closing wedge osteotomies, and aggressive resection can lead to shortening (5, 12). The proximal chevron and crescentic osteotomies are difficult to fix with screw fixation (6, 13) and have decreased strength as compared with the other aforementioned proximal osteotomies (8, 14). We present a technique for proximal metatarsal osteotomy for repair of significant hallux valgus deformity. This technique is not technically difficult, does not allow shortening, and provides solid screw fixation.