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PubMedDate not supplied

Insertion torque and resonance frequency analysis of dental implant systems in an animal model with loaded implants.

PURPOSE: The aim of this study was to compare insertion torque and resonance frequency analysis of different implant systems in an animal model with loaded implants. MATERIALS AND METHODS: Three types of Brånemark implants (machined MkIII, TiUnite MkIII, and MkIV) and 2 types of Straumann implants (sandblasted, large-grit, acid-etched [SLA] and titanium plasma-sprayed [TPS]) were studied. Thirty-two implants of each type (n = 160) were placed in 16 beagle dogs. Maximum insertion torque values were recorded. After a healing period of 8 weeks, the implants were loaded for 3 months; the animals were then sacrificed. At placement, after healing, and at the end of the loading phase, resonance frequency analysis was performed and implant stability quotients (ISQs) were recorded. RESULTS: Higher insertion torque values were seen for the conical MkIV than for the MkIII. No difference was seen between the Brånemark and Straumann implants on the basis of ISQ value at placement. ISQ and insertion torque values were lower for the cylindric Straumann implants than for the self-tapping implants. For all implant systems a significant decrease in median ISQ was observed, with a median decrease ranging from 3 to 6. ISQ values for self-tapping implants remained stable after loading, whereas the ISQ values for non-self-tapping cylinders decreased. The maximum insertion torque values for failed and successful implants were not significantly different. Significantly higher ISQ values at placement were seen for successful implants (P =.003). Based on this model for ISQ, a threshold of 65.5 was identified, with a sensitivity of 83% and specificity of 61% for prediction of implant loss. ISQ values at the start of loading were not predictive of implant loss in the loading period. CONCLUSION: Caution should be used when judging implant systems on the basis of resonance frequency analysis and torque measurement.

Animals↗
PubMedDate not supplied

An in vitro load evaluation of a conical implant system with 2 abutment designs and 3 different retaining-screw alloys.

PURPOSE: The aim of this in vitro study was to evaluate the load resistance in a conical implant system by comparing combinations of 2 different abutment head angles and 3 different retaining screw materials. MATERIALS AND METHODS: The retaining screw materials (titanium alloy, gold alloy, and commercially pure titanium) were tested with abutment-head angles of 20 degrees and 45 degrees. Six groups of 10 specimens each were prepared. An oblique (30-degree) compression test was performed in a Lloyd LRX universal testing machine with the abutment attached to a superstructure with a retaining screw. All specimens were loaded until fracture or permanent deformation occurred. The results were evaluated statistically with Wilcoxon signed rank test for variance distribution (P < .05 considered significant). RESULTS: There were statistically significant differences in load resistance between 20-degree and 45-degree abutments. The titanium screws (titanium alloy and commercially pure) in the 45-degree abutment group had almost equal mean values, while the gold alloy had a significantly lower value. In the 20-degree abutment group, significantly higher values were found with commercially pure titanium compared to titanium alloy and gold alloy, but the difference between the values for the gold and titanium alloys was not significant. DISCUSSION: The angulation of the abutment head played the most significant role in determining the amount of load withstood, but the material used for the screw was also relevant. CONCLUSION: A 45-degree abutment can be combined with a retaining screw of any of these materials to create a functional implant system. The test also substantiated that, irrespective of the retaining-screw material, a 20-degree abutment could resist loading forces of at least 900 N.

Alloys↗
PubMedDate not supplied

Clinical outcome of 802 immediately loaded 2-stage submerged implants with a new grit-blasted and acid-etched surface: 12-month follow-up.

PURPOSE: The aim of this study was to evaluate the clinical outcome of delayed or immediately loaded implants of 3 different implant macrodesigns. The hypothesis was that no significant differences in implant success would be observed between immediately and delayed loaded implants. MATERIALS AND METHODS: Between July 2003 and December 2003, 321 patients were consecutively enrolled for this study. Immediate loading was performed in cases where the implant stability quotient (ISQ) values were > 60 (as determined by resonance frequency analysis) and implant insertion torque was > 25 Ncm. In the case of delayed loading, a submerged technique (2-stage) or a single-stage procedure was used. The following variables were statistically analyzed with logistic regression: implant length, implant diameter, implant type, implant site, insertion torque, ISQ, and type of loading (immediate or delayed). RESULTS: Eight hundred two implants were placed. Immediate loading was chosen for 423 implants and delayed loading for 379 implants. All implants were followed up for a minimum of 12 months after prosthetic loading. Only 3 implants were lost, with an overall success rate of 99.6%. No statistically significant differences were found for any variables between the failures in the 2 groups (immediate loading protocol versus delayed loading). Implants with a crestal bone loss greater than 0.2 mm during the first year of observation (69 cases) were evaluated as a group; within this subset, only ISQ value (P < .004), implant length (P < .002), and implant type (P < .049) had a statistically significant effect on crestal bone resorption. CONCLUSIONS: Based upon this study of 802 implants, no significant differences in implant success were observed between the 2 groups.

Acid Etching, Dental↗
PubMedDate not supplied

Multiple single-tooth implant restorations in the posterior jaws: maintenance of marginal bone levels with reference to the implant-abutment microgap.

PURPOSE: The purpose of this study was to measure marginal bone loss from the implant-abutment microgap to the bone crest between multiple freestanding implants functionally loaded for up to 7.5 years in the posterior jaws. MATERIALS AND METHODS: Patients consecutively treated for the replacement of missing posterior teeth were included in the study. Using the implant-abutment interface, which was placed level with the crestal bone as a reference point, standardized follow-up radiographs were obtained to evaluate marginal bone loss. Results were subject to statistical analysis using the Wilcoxon rank sum test and the Wilcoxon signed rank test at the 95% confidence level. Additionally, soft tissue and prosthetic complications were recorded. RESULTS: One hundred seventy-three implants in 54 patients were evaluated. Implants were in function for a mean of 37 months (range, 21 to 91 months). One implant failed, for a survival rate of 99.4%. Overall mean marginal bone loss was 0.65 mm (range, 0.0 to 4.8 mm). For the 80 maxillary and 93 mandibular implants, mean marginal bone loss was 0.56 mm and 0.70 mm, respectively. The frequency of bone loss > or = 1.0 mm was 25.0% in the maxilla and 36.0% in the mandible; 23.1% of maxillary implants and 16.7% of mandibular implants demonstrated no bone loss. No significant differences were observed between men and women or between smokers and nonsmokers. The difference between mesial and distal bone levels was statistically significant (P < .001), with respective means of 0.53 mm and 0.76 mm. Recorded prosthetic complications included cementation failure (17.7%), porcelain fracture (7.2%), and abutment screw loosening (2.2%). CONCLUSIONS: Multiple single-tooth implants placed in the posterior jaws perform extremely well. Furthermore, it is possible to retain bone close to the implant-abutment microgap with certain implant designs.

Adult↗
PubMed2006

Presurgical implant-supported prosthesis: technique for cementation of a definitive prosthesis immediately after surgery.

A fixed prosthesis, supported by implants, was fabricated prior to surgery and cemented with passive fit immediately after placement of 14 implants in the mandible. The prosthesis was constructed before implant surgery on a plaster cast that precisely reproduced the patient's hard and soft tissues. The cast was built using a method that allowed the transfer of hard and soft tissue anatomy from computerized tomograms. A rigid surgical stent, cast in gold, was used to place the implants into prosthetically ideal positions under three-dimensional control. The prosthesis was placed immediately after implant placement, using an occlusion-driven method, which avoided the need for occlusal adjustments to the prosthesis.

Cementation↗
PubMed2006

Immediate versus delayed functional loading of implants in the posterior mandible: a 2-year prospective clinical study of 12 consecutive cases.

The aim of this investigation was to evaluate the clinical success of immediately loaded implants versus implants loaded in a delayed fashion in the posterior mandible. Three implants were placed distal to the canines bilaterally in the edentulous distal mandibular ridges of 12 patients. One side was randomly selected for placement of three implants (delayed loading; control sites) with a progressive thread design for submerged healing, and after 3 months the implants were exposed and loaded with provisional splinted crowns, which were replaced 6 weeks later by the definitive restorations. Three additional implants (immediately loaded; test sites), of the same size were placed in the contralateral side of the mandible. The test implants had abutments placed and were loaded immediately using the same protocol as the control implants. After a mean loading period of 25.3 months, the patients showed normal mean clinical values without significant differences (P < 0.05) for test and control implants, respectively, as follows: Plaque Index: 0.4 versus 0.8; Sulcus Bleeding Index: 0.5 versus 0.3; probing pocket depth: 1.9 mm versus 2.1 mm; width of keratinized mucosa: 2.5 mm versus 3.3 mm; Periotest value: -3.7 versus -3.2. Twenty-nine of the examined sites showed no bone loss. After 2 years of loading in the posterior mandible, test and control implants had the same prognosis.

Bicuspid↗
PubMedDate not supplied

Mastication forces and implant-bearing surface.

This article discusses the shift of emphasis in implantology from the phenomenon of osseointegration of implants to the accurate fabrication of the prosthesis, recognizing the implant/prosthesis unit as an actual replica rather than a replacement of the missing tooth. The study of kinetics with its succession of mandibular cycles is used to discuss the integration of mastication and occlusion. The importance of periimplant ligament in natural teeth is discussed, along with the impact of its absence on implant mobility. The impact of the bone types and the root surface architecture on the implant-bearing surface is presented along with the stress of the mastication forces. All these factors have to be considered in the treatment planning and effectively communicated to the laboratory. The learning objective of this article is to provide updated information in those areas for the reader.

Bite Force↗
PubMed1995

Anterior single-tooth implant restorations.

The application of implant dentistry to the treatment of partial edentulism has necessitated the development of new components and techniques. This article reviews the various systems and techniques used to fabricate successful anterior single-tooth implant restorations. Placement techniques for nonsegmented, screw-retained abutments; segmented, screw-retained abutments; and segmented, cement-retained abutments are illustrated.

Cementation↗
PubMedDate not supplied

A comparison of implant/prosthesis loading with four clinical variables.

A comparative evaluation of torque at the gold screw, abutment screw, and implant was calculated for cuspal inclination, implant inclination, and horizontal and vertical implant offset. The method of comparison was expressed as a percentage of change from a hypothetical standard maxillary implant/prosthesis configuration. These data facilitate rational clinical conclusions that cuspal inclination produces the most torque, followed by maxillary horizontal implant offset, while implant inclination and apical implant offset produce minimal torque. Although these data are not intended as a quantitative analysis, they nonetheless provide a practical guide to diagnosis and treatment planning.

Bite Force↗
PubMedDate not supplied

Inaccurate fit of implant superstructures. Part 1: Stresses generated on the superstructure relative to the size of fit discrepancy.

This laboratory study used a photoelastic-coating technique to investigate the relationship between the magnitude and location of discrepancies of fit and the amount and distribution of surface stresses on an implant superstructure. For the test superstructure involving four abutments and a single fit discrepancy, maximum surface stress was found over the intermediate abutment, regardless of the location of the fit error. The results show a positive relationship between the size of the fit discrepancy and the magnitude of stress on the superstructure for gaps of up to 104 micrometers at an end abutment and 55 micrometers at an intermediate abutment, when the gold screws were tightened at 10-Ncm torque.

Dental Abutments↗
PubMed1995

Hygiene, maintenance, and prosthodontic concerns for the infirm implant patient: clinical report and discussion.

Hygiene techniques and prosthetic maintenance procedures are illustrated for an infirm implant patient who is unable to communicate verbally or in written modes. Potential problems are discussed as they pertain to long-term patients who are in nursing homes, domiciles, or hospital wards. The issue of modifying a prosthesis to enhance the ease of providing oral hygiene care is examined.

Aged↗
PubMed1995

The effects of superstructure fit and loading on individual implant units: Part I. The effects of tightening the gold screws and placement of a superstructure with varying degrees of fit.

This in vitro study investigated forces associated with the assembly of rigidly mounted Nobelpharma implants and a 'passively' fitting cast gold superstructure. The effects of modifying the fit by 10-110 micrometers were also investigated. Measurements were made using linear resistance strain gauges mounted longitudinally on the abutments. Tightening the gold screws produced high compressive strains. These were unevenly distributed, and inconsistent. Tensile strains were produced by gaps as small as 10 micrometers between the superstructure and an abutment while the ability of a torque of 10 N-cm in the gold screw to close the gaps was dependent on their dimensions and locations.

Dental Abutments↗