Anders Örtorp

A 3-year retrospective and clinical follow-up study of zirconia single crowns performed in a private practice

OBJECTIVES All-ceramic crowns have become increasingly used also in the posterior regions, but there are only few studies documenting the clinical outcome of these restorations. The aim was therefore to present the 3-year outcome of zirconia (NobelProcera) single crowns. METHODS All patients treated with porcelain-veneered zirconia single crowns in a private practice during the period October 2004 to November 2005 were included. The patient records were scrutinized for data on the restorations and the supporting teeth. Information was available for 161 patients and 204 crowns. At the 3-year recall appointments, a sample of 18 patients with 25 crowns was clinically examined and interviewed regarding patient satisfaction. RESULTS Most crowns (78%) were placed on premolars and molars. The clinical outcome of the crowns was favourable. No zirconia core fractured and no caries was observed on the abutment teeth. Some types of complication were recorded for 32 (16%) crowns or abutment teeth. The most severe complications, in total 12 restorations (6%), were recorded as failures: abutment tooth was extracted (5), remake of crown due to lost retention (4), veneer fracture (2) and persistent pain (1). The CDA criteria for 25 crowns were rated favourably, and patient satisfaction with the zirconia crowns was in general high. CONCLUSIONS The porcelain-veneered zirconia crowns (NobelProcera) showed good clinical results, were well accepted by the patients, and only few complications were reported over the 3-year follow-up period.

The fit of cobalt–chromium three-unit fixed dental prostheses fabricated with four different techniques: A comparative in vitro study

OBJECTIVES This study sought to evaluate and compare the marginal and internal fit in vitro of three-unit FDPs in Co-Cr made using four fabrication techniques, and to conclude in which area the largest misfit is present. METHODS An epoxy resin master model was produced. The impression was first made with silicone, and master and working models were then produced. A total of 32 three-unit Co-Cr FDPs were fabricated with four different production techniques: conventional lost-wax method (LW), milled wax with lost-wax method (MW), milled Co-Cr (MC), and direct laser metal sintering (DLMS). Each of the four groups consisted of eight FDPs (test groups). The FDPs were cemented on their cast and standardised-sectioned. The cement film thickness of the marginal and internal gaps was measured in a stereomicroscope, digital photos were taken at 12× magnification and then analyzed using measurement software. Statistical analyses were performed with one-way ANOVA and Tukeys test. RESULTS Best fit based on the means (SDs) in μm for all measurement points was in the DLMS group 84 (60) followed by MW 117 (89), LW 133 (89) and MC 166 (135). Significant differences were present between MC and DLMS (p<0.05). The regression analyses presented differences within the parameters: production technique, tooth size, position and measurement point (p < 0.05). SIGNIFICANCE Best fit was found in the DLMS group followed by MW, LW and MC. In all four groups, best fit in both abutments was along the axial walls and in the deepest part of the chamfer preparation. The greatest misfit was present occlusally in all specimens.

A 5-year retrospective study of survival of zirconia single crowns fitted in a private clinical setting

OBJECTIVES The aim of this report was to evaluate the 5-year clinical performance and survival of zirconia (NobelProcera™) single crowns. METHODS All patients treated with porcelain-veneered zirconia single crowns in a private practice during the period October 2004 to November 2005 were included. The records were scrutinized for clinical data. Information was available for 162 patients and 205 crowns. RESULTS Most crowns (78%) were placed on premolars and molars. Out of the 143 crowns that were followed for 5 years, 126 (88%) did not have any complications. Of those with complications, the most common were: extraction of abutment tooth (7; 3%), loss of retention (15; 7%), need of endodontic treatment (9; 4%) and porcelain veneer fracture (6; 3%). No zirconia cores fractured. In total 19 restorations (9%) were recorded as failures: abutment tooth extraction (7), remake of crown due to lost retention (6), veneer fracture (4), persistent pain (1) and caries (1). The 5-year cumulative survival rate (CSR) was 88.8%. CONCLUSIONS According to the present 5-year results zirconia crowns (NobelProcera™) are a promising prosthodontic alternative also in the premolar and molar regions. Out of the 143 crowns followed for 5 years, 126 (88%) did not have any complications. However, 9% of the restorations were judged as failures. Further studies are necessary to evaluate the long-term success.

CNC‐Milled Titanium Frameworks Supported by Implants in the Edentulous Jaw: A 10‐Year Comparative Clinical Study

BACKGROUND No long-term clinical studies covering more than 5 years are available on Computer Numeric Controlled (CNC) milled titanium frameworks. AIM To evaluate and compare the clinical and radiographic performance of implant-supported prostheses provided with CNC titanium frameworks in the edentulous jaw with prostheses with cast gold-alloy frameworks during the first 10 years of function. MATERIAL AND METHODS Altogether, 126 edentulous patients were by random provided with 67 prostheses with titanium frameworks (test) in 23 maxillas and 44 mandibles, and with 62 prostheses with gold-alloy castings (control) in 31 maxillas and 31 mandibles. Clinical and radiographic 10-year data were collected for the groups and statistically compared on patient level. RESULTS The 10-year prosthesis and implant cumulative survival rate was 95.6% compared with 98.3%, and 95.0% compared with 97.9% for test and control groups, respectively (p > .05). No implants were lost after 5 years of follow-up. Smokers lost more implants than nonsmokers after 5 years of follow-up (p < .01). Mean marginal bone loss in the test group was 0.7 mm (SD 0.61) and 0.7 mm (SD 0.85) in the maxilla and mandible, with similar pattern in the control group (p > .05), respectively. One prosthesis was lost in each group due to loss of implants, and one prosthesis failed due to framework fracture in the test group. Two metal fractures were registered in each group. More appointments of maintenance were needed for the prostheses in the maxilla compared with those in the mandible (p < .001). CONCLUSION The frequency of complications was low with similar clinical and radiological performance for both groups during 10 years. CNC-milled titanium frameworks are a viable alternative to gold-alloy castings for restoring patients with implant-supported prostheses in the edentulous jaw.

Early Laser-Welded Titanium Frameworks Supported by Implants in the Edentulous Mandible: A 15-Year Comparative Follow-Up Study

BACKGROUND Comparative long-term knowledge of different framework materials in the edentulous implant patient is not available for 15 years of follow-up. PURPOSE To report and compare a 15-year retrospective data on implant-supported prostheses in the edentulous mandible provided with laser-welded titanium frameworks (test) and gold alloy frameworks (control). MATERIALS AND METHODS Altogether, 155 patients were consecutively treated with abutment-level prostheses with two early generations of fixed laser-welded titanium frameworks (titanium group). Fifty-three selected patients with gold alloy castings formed the control group. Clinical and radiographic 15-year data were collected and compared for the groups. RESULTS All patients who were followed up for 15 years (n = 72) still had a fixed prosthesis in the mandible at the termination of the study. The 15-year original prosthesis cumulative survival rate (CSR) was 89.2 and 100% for titanium and control frameworks (p = .057), respectively (overall CSR 91.7%). The overall 15-year implant CSR was 98.7%. The average 15-year bone loss was 0.59 mm (SD 0.56) and 0.98 mm (SD 0.64) for the test and control groups (p = .027), respectively. Few (1.3%) implants had >3.1-mm accumulated bone loss after 15 years. The most common complications for titanium frameworks were resin or veneer fractures and soft tissue inflammation. Fractures of the titanium metal frame were observed in 15.5% of the patients. More patients had framework fractures in the earliest titanium group (Ti-1 group) compared to the gold alloy group (p = .034). Loose and fractured implant screw components were few (2.4%). CONCLUSION Predictable overall long-term results could be maintained with the present treatment modality. Fractures of the metal frames and remade prostheses were more common in the test group, and the gold alloy frameworks had a tendency to work better when compared with welded titanium frameworks during 15 years. However, on the average, more bone loss was observed for implants supporting gold alloy frameworks.

Laser‐Welded Titanium Frameworks Supported by Implants in the Partially Edentulous Mandible: A 10‐Year Comparative Follow‐Up Study

BACKGROUND Comparative long-term knowledge of different framework materials in the partially edentulous implant patient is not available. PURPOSE To report and compare 10-year data on free-standing implant-supported partial prostheses with laser-welded titanium (test) and conventional gold alloy (control) frameworks. MATERIALS AND METHODS Altogether, 52 partially edentulous patients were consecutively provided with laser-welded prostheses (n = 60) in the partially edentulous lower jaw (test group). A control group of 52 randomly selected patients with gold alloy castings (n = 60) was used for comparison. Clinical and radiographic 10-year data were retrospectively collected and evaluated for both groups. RESULTS The overall 10-year implant cumulative survival rate (CSR) was 93.0% (loaded implants, 96.4%), with a 10-year implant CSR of 91.5 and 94.7% for test and control implants, respectively (p > .05). Out of a total of 22 lost implants, 17 implants (77.3%) were shorter than 10 mm. The overall 10-year prosthesis CSR was 93.7%, with a corresponding 10-year CSR of 88.4 and 100% for test and control groups, respectively (p < .05). Average 10-year bone loss was 0.46 mm (SD 0.47) and 0.69 mm (SD 0.53) for the test and control groups (p < .001), respectively. Only 1% of the implants had >3 mm accumulated bone loss after 10 years. Altogether, 10 of the prostheses in both groups had implant component mechanical problems (8.3%). None of the frameworks or implants fractured, but more fractures of porcelain veneers were observed in the test group (p < .05). CONCLUSION The protocol of implant treatment in the partially edentulous jaw functioned well during 10 years, although prosthodontic maintenance was required. However, laser-welded titanium frameworks presented more problems as compared with gold alloy frameworks. More loaded implants were lost (p < .05), and higher incidence of porcelain chipping was noted in the test group (p < .05). However, bone loss was on an average lower for the test group during the 10 years of follow-up (p < .001).

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.

What is the evidence base for the efficacies of different complete denture impression procedures? A critical review

OBJECTIVES Many procedures used in prosthodontics, including the materials and methods used for complete denture impressions, lack support of good evidence. The aims were to systematically, and critically, review the literature on complete denture impression materials and methods to identify an impression procedure that can be considered expedient for achieving a satisfactory clinical outcome for complete denture wearers. DATA AND SOURCES MEDLINE/PubMed and the Cochrane Library were searched for studies on impression procedures used in the clinical fabrication of complete dentures. The search focused on best available evidence with respect to clinical outcome. STUDY SELECTION PubMed listed 1201 titles for the combination terms of complete denture and impression. Five relevant randomized controlled trials were identified. No review of complete denture impressions was found in the Cochrane Library. RESULTS Two-step procedures for complete denture impressions dominate all textbooks, teaching and specialist practice, despite an absence of convincing evidence of its superiority. No controlled studies supporting the use of border moulding, post-dam, and functional and mucostatic impressions, were identified. Two studies showed that a one-step method using alginate in a stock tray offers a similar clinical result to more complicated, expensive and time-consuming two-step material and technique combinations. CONCLUSIONS There was no support for the frequent textbook statement that the two-step procedure is necessary and superior to the one-step method. While some special clinical situations may benefit from other combinations of materials and techniques, the results suggest that the simple and inexpensive one-step procedure can serve the needs of the majority of edentulous patients. CLINICAL SIGNIFICANCE In spite of the fact that two-step procedures for complete denture impressions dominate textbooks, teaching and specialist practice, the results of this review suggest that a simple and inexpensive one-step procedure can serve the needs of the majority of edentulous patients.

A 5-year retrospective study of cobalt-chromium-based fixed dental prostheses.

PURPOSE The aim of this retrospective study was to evaluate the 5-year clinical outcome for ceramic veneered cobalt-chromium (Co-Cr) fixed dental prostheses (FDPs) fitted in a private clinical setting. MATERIALS AND METHODS All patients treated consecutively with Co-Cr FDPs from January 2000 to November 2005 were included, and complications were registered. Patient records were examined for details on the restorations and abutment teeth. A total of 149 patients with 201 FDPs, 1,135 units, and 743 abutment teeth were recorded. RESULTS Of the 149 patients, 122 (82%) were followed for 5 years. Complications occurred in 34 patients (23%) and 38 FDPs (19%). The most frequent were caries (6.7% of patients, 5% of FDPs, 2.2% of abutments) and cement failure (6.7% of patients, 5% of FDPs, 3.1% of abutments). Cohesive ceramic fractures occurred in only 7 FDPs (3.5% of FDPs, 0.7% of units). No adhesive ceramic fractures were recorded. The 5-year cumulative rates for success and survival were 83.8% and 92.8%, respectively. CONCLUSIONS Co-Cr FDPs appear to be a promising prosthodontic treatment modality, presenting low incidence of complications and a high survival rate during the first 5 years of function. However, long-term randomized controlled studies are necessary to confirm these findings.