Alf Eliasson

A Retrospective Analysis of Early and Delayed Loading of Full-Arch Mandibular Prostheses Using Three Different Implant Systems: Clinical Results with Up to 5 Years of Loading

BACKGROUND Early loading of implant-supported prostheses in the edentulous mandible is widely accepted, but do the clinical results replicate those of delayed loading? PURPOSE The aim of this study was to evaluate clinical outcome and patient satisfaction with early or delayed loading in patients treated with fixed prostheses, using three different implant systems. MATERIALS AND METHODS One hundred and nine consecutively treated patients received 490 implants supporting fixed prostheses; 82 patients with Brånemark System implants (Nobel Biocare AB, Göteborg, Sweden), 16 with Astra Tech implants (Astra Tech AB Dental Implant system, Mölndal, Sweden), and 11 with ITI MonoType implants (ITI Dental Implant System, Institute Straumann AG, Waldenburg, Switzerland). Prostheses were placed within 2 to 3 weeks in 55 patients; 54 patients underwent a two-stage procedure. Data were collected from patient records and radiographs; 83 patients attended a clinical examination and received a questionnaire. RESULTS All patients had fixed prostheses at follow-up with a mean observation time of 3.5 years. Cumulative survival rates (CSRs) were 92.5% of prostheses and 94.4% of implants for early loading, and 98.0 and 97.9% for delayed loading. The mean radiographic bone loss after the first year was small, and at 5 years less than 0.2 mm for both groups. With early loading, significantly more prostheses (p < .05) needed adjustment or replacement. CONCLUSION Statistically significantly more prostheses needed adjustment or replacement in the early group. The present study suggested lower CSRs for prostheses and implants in the early loading group after 5 years; the difference was not statistically significant. Larger study samples are needed to verify statistically small differences between treatment techniques.

The accuracy of an implant impression technique using digitally coded healing abutments.

BACKGROUND A healing abutment (Encode) provided with digitally coded information on length and diameter on the top was launched in 2007. So far, no study has evaluated working cast fabrication using impressions of the coded abutments and analogue placement using a robot technique. PURPOSE To compare the accuracy of implant analogue placement in working casts using a robot technique and an impression of Encode healing abutments, with the traditional technique. MATERIALS AND METHODS One acrylic master model was fabricated, provided with two groups of three implant analogues. Encode healing abutments were mounted on the test side and conventional pickup impression copings were inserted on the control side. Fifteen impressions were made with a vinylpolysiloxane material. Implant analogues were placed by a robot on the test side. The center point of each implant analogue fitting surface was measured with a laser measuring machine in the x-, y-, and z-axis, as were also the angular direction of the center axis and the position of the antirotational hex. Two-way analysis of variance was performed using SPSS 17.0; the statistical significance was set at p < .05. RESULTS Mean center point deviation for the test and control side was 37.4 µm versus 18.5 µm (p = .001) in the x-axis, 47.3 µm versus 13.9 µm (p < .001) in the y-axis, and 35.0 µm versus 15.1 µm (p < .013) in the z-axis. Mean angle error was 0.41 degrees for the test and 0.14 degrees for the control side (p < .001). Mean rotation of the hexagon was 2.88 degrees for the test side and 1.82 degrees for controls (p < .001). CONCLUSIONS Both conventional and robot technique presented low levels of displacement of the implant analogues in all casts. The test technique was less precise, but the difference in accuracy was small, and both techniques are precise enough for single crowns and short-span, implant-supported fixed partial prostheses.

Marginal and internal fit of cobalt-chromium fixed dental prostheses generated from digital and conventional impressions

Objectives. Digital impressions are increasingly used and have the potential to avoid the problem of inaccurate impressions. Only a few studies to verify the accuracy of digital impressions have been performed. The purpose of this study was to compare the marginal and internal fit of 3-unit tooth supported fixed dental prostheses (FDPs) fabricated from digital and conventional impressions. Methods. Ten FDPs were produced from digital impressions using the iTero system and 10 FDPs were produced using vinyl polysiloxane (VPS) impression material. A triple-scan protocol and CAD software were used for measuring and calculating discrepancies of the FDPs at 3 standard areas: mean internal discrepancy, absolute marginal gap, and cervical area discrepancy. The Mann-Whitney U test was used for analyzing the results. Results. For conventional and digital impressions, respectively, FDPs had an absolute marginal gap of 147 μm and 142 μm, cervical area discrepancy of 69 μm and 44 μm, and mean internal discrepancy of 117 μm and 93 μm. The differences were statistically significant in the cervical and internal areas (P < 0.001). Significance. The results indicated that the digital impression technique is more exact and can generate 3-unit FDPs with a significantly closer fit compared to the VPS technique.

Implant-Supported Single Crowns Replacing Congenitally Missing Maxillary Lateral Incisors : A 5-Year Follow-Up

BACKGROUND Knowledge of the long-term survival of single implants in cases of congenitally missing lateral incisors in the maxilla is limited. PURPOSE This retrospective study aimed to evaluate the 5-year survival of implants and implant-supported crowns (ISCs) and to assess the functional and aesthetic outcomes from the professional and patient perspectives. MATERIALS AND METHODS From a total of 46 patients with congenitally missing upper lateral incisors, 36 patients treated with 54 Brånemark® (Nobel Biocare AB, Göteborg, Sweden) implants and ISCs participated in the study. A clinical examination, California Dental Association (CDA) evaluation, and patient questionnaire were used to rate and compare the objective and subjective evaluations of the ISCs. RESULTS The survival of implants and ISCs was 100%. The CDA ratings were satisfactory for all ISCs, with 70% being rated excellent. The patient rating was also high for the overall satisfaction item, with 21 being completely satisfied and 14 fairly satisfied. However, 12 patients wished for the replacement of their ISCs. Logistic regression analysis indicated that a less optimal embrasure fill was the most discriminating factor though not statistically significant (p = .082). CONCLUSIONS One-third of the patients wished for the replacement of their ISCs. Soft tissue adaptation seems to be an important factor for overall satisfaction.

Additively Manufactured Titanium and Cobalt-Chromium Implant Frameworks : Fit and Effect' of Ceramic Veneering

PURPOSE The purpose of this study was to evaluate the fit of additively manufactured cobalt-chromium and titanium and CNC-milled titanium frameworks before and after ceramic veneering. MATERIALS AND METHODS Ten stone casts simulating an edentulous maxilla provided with six abutment analogs were produced. For each stone cast, one additively manufactured cobalt-chromium framework (AM CoCr) and one titanium framework (AM Ti) were fabricated. The fit was analyzed with a coordinate measuring machine in three dimensions (x, y, and z axes) using best-fit virtual matching of center point coordinates, before and after ceramic veneering. CNC-milled titanium frameworks (CNC Ti) and earlier results from CNC-milled cobalt-chromium frameworks (CNC CoCr) were used for comparison. RESULTS All frameworks presented minor misfit before and after veneering in the horizontal plane (x- and y-axes) between 2.9 and 13.5 μm and in the vertical plane (z-axis) between 1.6 and 5.4 μm. Ceramic veneering affected the fit of all groups of frameworks. Both AM Ti and AM CoCr presented significantly smaller distortion in the vertical plane compared with the CNC-milled frameworks. CONCLUSION Implant-supported frameworks can be produced in either Ti or CoCr using either CNC milling or additive manufacturing with a fit well within the range of 20 μm in the horizontal plane and 10 μm in the vertical plane. The fit of frameworks of both materials and production techniques are affected by the ceramic veneering procedure to a small extent.

A retrospective multicenter study comparing metal–ceramic and composite single crowns performed in public general dentistry: 5-year results

Abstract Objective The aim of this study was to evaluate and compare the 5-year survival and complication rate of metal–ceramic (MC) and composite single crowns performed within Public Dental Service, general dentistry, in three Swedish counties and with patients’ gender, tooth position, root canal treatment and the presence of a post-and-core taken into account. Methods Data were collected from dental records of 600 patients who had received either an MC (n = 300) or a composite (n = 300) crown on a premolar or molar tooth in the year 2005 and where 5 years of follow-up data were available. Status at treatment completion and at follow-up was recorded, together with any history of intervention during the follow-up period. Results The 5-year survival rate for MC crowns was higher than for composite crowns (93% versus 70%; p < 0.001). This difference was stable, irrespective of the county, patients’ gender or tooth position. No gender difference in survival rate was seen for MC crowns, while the survival of composite crowns was significantly higher among women than among men (75% versus 65%; p < 0.05). For MC crowns, there was a tendency toward a lower survival rate for endodontically treated teeth without a post-and-core (83%) as compared to those provided with a post-and-core (93%) and to vital teeth (94%). Surviving composite crowns had recordings of significantly more complications than MC crowns (p < 0.001). Conclusion On premolars and molars, MC crowns have a better medium-term prognosis and fewer complications than composite crowns.

Fit of cobalt–chromium implant frameworks before and after ceramic veneering in comparison with CNC-milled titanium frameworks

Computer‐aided design/computer‐aided manufacturing fabrication of implant‐supported frameworks is a standard procedure, and the use of ceramic‐veneered cobalt–chromium alloys is increasing. However, no data are available concerning the precision of fit of these frameworks and the impact on the fit of the veneering procedure. The aim of this study was to evaluate the fit of computer numeric‐controlled‐milled cobalt–chromium and titanium implant frameworks for edentulous maxillas, provided with six implants. An additional aim was to evaluate the effect of ceramic veneering on the fit of the cobalt–chromium frameworks. Ten stone casts simulating an edentulous maxilla provided with six dental implants and abutments were produced. One computer numeric‐controlled‐milled cobalt–chromium framework and one titanium framework were fabricated for each stone cast. Each stone cast and corresponding titanium and cobalt–chromium framework was measured with a coordinate measuring machine in the three‐dimensional (X axis, Y axis, and Z axis) directions. Both milled titanium and cobalt–chromium frameworks presented a good fit in the vertical plane (Z axis), 5.3 µm for titanium frameworks and 4.6 µm for the cobalt–chromium frameworks. The titanium frameworks showed a statistically significant smaller mean degree of misfit in the horizontal plane, X (5.0 µm) and Y (2.8 µm) axes as compared with the cobalt–chromium frameworks presenting a mean deviation of 13.5 µm in X axis and 6.3 µm in Y axis (P < 0.001). After ceramic veneering of the cobalt–chromium frameworks, the horizontal distortion significantly decreased from 13.5 to 9.7 µm in X axis (P = 0.007) and from 6.3 to 4.4 µm in Y axis (P = 0.017). The fit of both titanium and cobalt–chromium frameworks was very good. There were small but significant differences in fit between the titanium and cobalt–chromium frameworks, but the difference is of no clinical significance. The ceramic veneering resulted in a minor but significant improvement of the fit for the cobalt–chromium frameworks.