Accuracy of different digital scanning techniques and scan bodies for complete-arch implant-supported prostheses.

STATEMENT OF PROBLEM: The effect of various scan bodies and scanning techniques on the accuracy and scan time for completely edentulous patients is not well understood. PURPOSE: The purpose of this in vitro study was to evaluate the effects of 4 scanning techniques and 5 intraoral scan bodies (ISBs) on the trueness, precision, and scan time in a completely edentulous arch with 4 implants. MATERIAL AND METHODS: Five different ISB systems: AF, NT, DE, C3D, and ZI, and 4 different scanning techniques: unmodified master model (NO), glass fiduciary markers placed on the edentulous ridge (GB), pressure-indicating paste brushed over the ridge and palate (PP), and floss tied between the scan bodies (FL), were evaluated. Scan bodies were attached to an edentulous maxillary model with 4 dental implant analogs and scanned by using a structured blue light industrial scanner, and 5 consecutive digital scans of the model were made by using an intraoral scanner and 1 of the 4 techniques (n=5). The scans were superimposed on the master reference model, and the distance deviation and angular deviation of the scan bodies was calculated. The scan time was also recorded. A 2-factor ANOVA was used to examine the effect of scan body and technique on the trueness and scan time, with subsequent Tukey honestly significant difference or Bonferroni-corrected Student t tests. Precision was evaluated by tests for homogeneity of the variances between groups. Reliability for the entire study was evaluated using the intraclass correlation coefficient (α=.05 for all tests). RESULTS: The overall reliability of the study according to intraclass correlations was 0.999. In terms of trueness, no statistically significant interaction was found between the effects of scan body and technique on the distance deviation (P=.246); however, the scan body (P=.031) and technique (P<.001) each had a significant effect independently. A statistically significant interaction was found between the effects of the scan body and technique on angular deviation (P<.001). Testing for the homogeneity of variances demonstrated significant differences in the precision among the groups in terms of distance deviation (P≤.013) and angular deviation (P≤.003). No statistically significant interaction was found between the effects of the scan body and technique (P=.076) on the scan time; however, the scan body alone was found to have a significant effect (P<.001). CONCLUSIONS: The accuracy (trueness and precision) of complete-arch digital implant scans using ISBs was affected by both the scan body and scan technique when using an intraoral scanning system. The ZI scan body had significantly less distance deviation, whereas splinting scan bodies with floss led to significantly more distance deviation. The scan techniques with different surface modifications were not found to improve the scan accuracy. The use of different ISBs led to significant differences in the scan time.

Treatment of edentulous mandible with metal-resin fixed complete dentures: A 15- to 20-year retrospective study.

OBJECTIVES: The purpose of this retrospective study was to report the implant and prosthetic complications of mandibular metal-resin fixed complete dentures (MRFCDs) opposing a maxillary complete removable dental prosthesis (CRDP) in a 15- to 20-year post-placement follow-up period. MATERIAL AND METHODS: Dental records of 24 edentulous patients treated by a mandibular MRFCD and a maxillary CRDP were reviewed. Complications for the implants, MRFCDs, and CRDPs were recorded in four different recall periods: 0-5 years, 5-10 years, 10-15 years, and more than 15 years. The survival and failure times based on Kaplan-Meier statistics were analyzed using Lifetest procedures. Product-limit survival estimates were used for cumulative survival rates (CSRs). RESULTS: The mean service time was 18.5 years. The CSR for the implants and MRFCDs was 91.8% at 16.9 years (confidence intervals: 85.2% and 95.5%) and 80% at 19.6 years (confidence intervals: 44.1% and 94.1%), respectively. The implant failures after 15 years occurred because of a tumor resection. Acrylic resin tooth fracture (45.8% of patients) and wear (75% of patients) were the most common complications with the MRFCD. Retaining screw complications [loosening (8.1% of retaining screws) and fracture (11.3% of retaining screws)] were also common. CONCLUSIONS: The outcomes seen with MRFCD over the long term were favorable. After placement of prostheses, 1 implant loss was observed potentially due to prosthetic/hygiene/periodontal factors. However, potential maintenance complications such as acrylic resin tooth fracture and/or wear and retaining screw loosening and fracture may occur in the long term when a similar design is used for the mandible.

Positional accuracy of a prosthetic treatment plan incorporated into a cone beam computed tomography scan using surface scan registration.

STATEMENT OF PROBLEM: The registration of surface scans onto cone beam computed tomography (CBCT) scans has been proposed as a method of visualizing different anatomic structures and the prosthetic treatment plan simultaneously. This method also overcomes some of the problems associated with conventional radiographic templates. However, it has not been thoroughly investigated or validated for use in implant dentistry. PURPOSE: The purpose of this in vitro study was to evaluate the accuracy of a prosthetic treatment plan surface scan incorporated into a CBCT scan and to compare it to conventional radiographic templates for single tooth replacement. MATERIAL AND METHODS: Direct surface scans of a completely dentate master model with removable radiopaque teeth were made using an intraoral scanner, and indirect surface scans of a stone duplicate of the master model were made using a laboratory scanner. To simulate a clinical scenario, the mandibular left first molar was removed. A CBCT scan of the clinical scenario was made. The surface scans were registered onto the CBCT scans. Radiographic templates for the clinical scenario were fabricated, and the master model was subsequently scanned using the same CBCT scanner with each radiographic template seated. Metrology software was used to assess the accuracy of each method by measuring the 3-dimensional deviation on standard tessellation language (STL) files generated from the CBCT scans against an STL file of the completely dentate master model generated from a CBCT scan. One-way ANOVA and the Tukey HSD test were used for statistical analysis (α=.05). RESULTS: The incorporation technique had a significant effect on deviation from the master model (P=.004). The overall mean 3-dimensional deviation was 0.04 mm for direct surface scan registrations, 0.03 mm for indirect surface scan registrations, and 0.33 mm for radiographic templates. Radiographic templates were significantly less accurate compared with both surface scan registration methods (P<.001), whereas no statistically significant difference in accuracy was found between the registration of a laboratory scan and that of an intraoral scan (P=.94). CONCLUSIONS: Intraoral and laboratory surface scan registration on CBCT scans were more accurate than radiographic templates for prosthetic treatment plan incorporation. The accuracy of the registration of an intraoral scan and a laboratory scan was comparable.

Fabrication of an implant-supported fixed complete denture using multiple digital technologies for a patient with a perioral burn: A clinical report.

This clinical report describes the prosthetic and surgical management of a patient with a restricted oral orifice due to a perioral burn. Complete oral rehabilitation was achieved with maxillary and mandibular implant-supported fixed prostheses using a combination of digital and conventional impressions, design, and processing techniques.

Effect of length and location of edentulous area on the accuracy of prosthetic treatment plan incorporation into cone-beam computed tomography scans.

BACKGROUND: Effects of length and location of the edentulous area on the accuracy of prosthetic treatment plan incorporation into cone-beam computed tomography (CBCT) scans has not been investigated. PURPOSE: To evaluate the effect of length and location of the edentulous area on the accuracy of prosthetic treatment plan incorporation into CBCT scans using different methods. MATERIAL AND METHODS: Direct digital scans of a completely dentate master model with removable radiopaque teeth were made using an intraoral scanner, and digital scans of stone duplicates of the master model were made using a laboratory scanner. Specific teeth were removed to simulate different clinical situations and their CBCT scans were made. Surface scans were registered onto the CBCT scans. Radiographic templates for each clinical situation were also fabricated and used during CBCT scans of the master models. Using metrology software, three-dimensional (3D) deviation was measured on standard tesselation language (STL) files created from the CBCT scans against an STL file of the master model created from a CBCT scan. Statistical analysis was done using the MIXED procedure in a statistical software and Tukey HSD test (α =.05). RESULTS: The interaction between location and method was significant (P = .009). Location had no significant effect on registration methods (P > .05), but on the radiographic templates (P = .011). Length of the edentulous area did not have any significant effect (P > .05). CONCLUSIONS: Accuracy of digital image registration methods was similar and higher than that of radiographic templates in all clinical situations. Tooth-bound radiographic templates were significantly more accurate than the free-end templates. The results of this study suggest using image registration instead of radiographic templates when planning dental implants, particularly in free-end situations.

Fracture analysis of CAD-CAM high-density polymers used for interim implant-supported fixed, cantilevered prostheses.

STATEMENT OF PROBLEM: The load-to-fracture performance of computer-assisted design and computer-assisted manufacturing (CAD-CAM) high-density polymer (HDP) materials in cantilevers is unknown. PURPOSE: The purposes of this in vitro study were to evaluate the load-to-fracture performance of CAD-CAM-fabricated HDPs and to compare that with performance of autopolymerized and injection-molded acrylic resins. MATERIAL AND METHODS: Specimens from 8 different brands of CAD-CAM HDPs, including Brylic Solid (BS); Brylic Gradient (BG); AnaxCAD Temp EZ (AE); AnaxCAD Temp Plus (AP); Zirkonzahn Temp Basic (Z); GDS Tempo-CAD (GD); Polident (Po); Merz M-PM-Disc (MAT); an autopolymerized acrylic resin, Imident (Conv) and an injection-molded acrylic resin, SR-IvoBase High Impact (Inj) were evaluated for load-to-fracture analysis (n=5). CAD-CAM specimens were milled from poly(methyl methacrylate) (PMMA) blocks measuring 7 mm in buccolingual width, 8 mm in occlusocervical thickness, and 30 mm in length. A wax pattern was prepared in the same dimensions used for CAD-CAM specimens, flasked, and boiled out. Autopolymerizing acrylic resin was packed and polymerized in a pressure container for 30 minutes. An identical wax pattern was flasked and boiled out, and premeasured capsules were injected (SR-IvoBase) and polymerized under hydraulic pressure for 35 minutes for the injection-molded PMMA. Specimens were thermocycled 5000 times (5°C to 55°C) and fixed to a universal testing machine to receive static loads on the 10-mm cantilever, vertically at a 1 mm/min crosshead speed until fracture occurred. Maximum load-to-fracture values were recorded. ANOVA was used to analyze the maximum force values. Significant differences among materials were analyzed by using the Ryan-Einot-Gabriel-Welsch multiple range test (α=.05). RESULTS: Statistically significant differences were found among load-to-fracture values of different HDPs (P<.001). GD and Po materials had significantly higher load-to-fracture values than other materials (P<.001), and no statistically significant differences were found between GD and Po. The lowest load-to-fracture values were observed for autopolymerized and BG materials, which were significantly lower than those of GD, Po, AE, AP, Z, MAT, Inj, and BS. The load-to-fracture value of autopolymerized acrylic resin was not significantly different from that of BG CAD-CAM polymer. CONCLUSIONS: GD and Po CAD-CAM materials had the highest load-to-fracture values. AE, AP, Z, MAT, and BS CAD-CAM polymers and injection-molded acrylic resin had similar load-to-fracture values, which were higher than those of BG and autopolymerized acrylic resin. Autopolymerized acrylic resin load-to-fracture value was similar to that of BG CAD-CAM polymer, which is colored in a gradient pattern.

A load-to-fracture and strain analysis of monolithic zirconia cantilevered frameworks.

STATEMENT OF PROBLEM: The dimensions of implant-supported fixed cantilevered prostheses are important to prevent mechanical and biological complications. Information on the optimum thickness and cantilever length for improving the strength of zirconia cantilevered frameworks is limited in the literature. PURPOSE: The purpose of this in vitro study was to investigate the effect of cantilever length and occlusocervical thickness on the load-to-fracture and strain distribution of zirconia frameworks. MATERIAL AND METHODS: Twenty-seven rectangular prism-shaped specimens (6 mm thick buccolingually) were fabricated using a computer-aided design and computer-aided manufacturing (CAD-CAM) milling technique. The specimens were prepared in 9 groups (n=3) according to their vertical dimensions (6×6 mm, 8×6 mm, and 10×6 mm) and cantilever loading distance (7 mm, 10 mm, and 17 mm). All specimens were heat treated in a porcelain furnace and thermocycled for 20000 cycles before the tests. Each framework was secured using a clamp attached to the first 20 mm of the framework. A 3-dimensional image correlation technique was used for a full-field measurement of strain during testing. A load-to-fracture test was used until the specimens fractured. Maximum force and principal strain data were analyzed by 2-way analysis of variance using the maximum likelihood estimation method (α=.05). RESULTS: No statistically significant effects (P>.05) were found for occlusocervical thickness and cantilever length or between them on the strain distribution. The results showed that the effect of occlusocervical thickness and cantilever length was significant on the load to fracture (P<.001). No statistically significant interaction was observed between the 2 factors (P>.05). CONCLUSIONS: Increased occlusocervical thickness and decreased cantilever length allowed the cantilever to withstand higher loads. The occlusocervical thicknesses and cantilever lengths of zirconia frameworks tested withstood the maximum reported occlusal force. The properties of components in the implant-abutment framework assembly should be considered in the interpretation of these results.

Radiographic Appearance of Interocclusal Record Materials for Cone Beam Computed Tomography-Guided Implant Surgeries.

PURPOSE: To select an ideal interocclusal record material for cone beam computed tomography (CBCT)-guided implant surgery based on the material's radiodensity on the scan. MATERIALS AND METHODS: Twelve commonly used interocclusal record materials were used for this investigation: two were waxes, one was polyether, and nine were polyvinyl-siloxane-type materials. A scan template was fabricated by duplicating existing dentures in Ortho-Jet acrylic resin mixed with 30% barium powder for the teeth and 10% barium powder for the denture base between the teeth and the tissue. An interocclusal record was fabricated with each material, and the same template was used to obtain a CBCT scan with an ICAT machine (Imaging Sciences International) at 0.3 voxel and 14-bit depth settings. Twelve CBCT scans were obtained and analyzed. The radiopacity of the barium teeth was used as a control and was compared with the opacity of the 12 materials using a paired t test. A post hoc analysis of variance (ANOVA) test was used to compare the densities of the various materials with each other. RESULTS: There was a statistically significant difference between the radiopacity of barium teeth (gray value: 1,959.475) and that of Modelling Wax (gray value: 750; P = .0026), Aluwax (gray value: 795.22; P = .0022), Blu-Bite CT (gray value: 1,105; P = .005), Ramitec (gray value: 1,105.3; P = .08), Memosil 2 (gray value: 1,202; P = .01) followed by Reprosil (gray value: 1,407.73; P = .01). Compared with the barium teeth, there was no statistically significant difference between the densities of Futar D (gray value: 1,866.5; P = .51), Jet Bite (gray value: 1,660.04; P = .08), Lab-Putty (gray value: 1,402.14; P = .19), and Memoreg 2 (gray value: 1,754.72; P = .1). The highest radiodensity was seen with Blu-Mousse (gray value: 2,949; P = .007) and Take 1 (gray value: 2,229.85; P = .025), which were also significantly different from the density of the barium teeth but in the opposite direction, making them more opaque. CONCLUSION: Within the limitations of this in vitro study, the most radiolucent appearance of Modelling Wax, Aluwax, Memosil 2, Blu-Bite CT, and Ramitec made them the suitable materials of choice of those tested, as the interocclusal registration record during CBCT scanning allowed clear visualization of barium teeth.

Strain analysis of 9 different abutments for cement-retained crowns on an internal hexagonal implant.

STATEMENT OF PROBLEM: Many aftermarket abutments for cement-retained crowns are available for the tapered screw-vent implant. Aftermarket abutments vary widely, from stock to custom abutments and in materials such as zirconia, titanium, or a combination of the two. How these aftermarket abutments perform under occlusal loads with regard to strain distribution is not clear. PURPOSE: The purpose of this in vitro study was to measure and compare the different strains placed upon the bone around implants by 9 different abutments for cement-retained crowns on an implant with an internal hexagonal platform. MATERIAL AND METHODS: Nine 4.1×11.5-mm tapered screw-vent implants were placed into a 305×51×8-mm resin block for strain measurements. Five abutment specimens of each of the 9 different abutments (N=45) were evaluated with 1 of the 9 implants. Monolithic zirconia crowns were then fabricated for each of the 9 different abutments, the crowns were cyclically loaded (maximum force 225 N) at 30 degrees, twice at a frequency of 2 Hz, and the strain was measured and recorded. The strain to the resin block was determined using a 3-dimensional digital image correlation (3D DIC) technique. Commercial image correlation software was used to analyze the strain around the implants. Data for maximal and minimal principal strains were compared using analysis of variance with a Tukey-Kramer post hoc test (α=.05). RESULTS: Strain measurements showed no significant differences among any of the abutments for minimal (compression) principal strains (P>.05). For maximal (tensile) principal strains, the zirconia abutment showed the highest, and the patient-specific abutment showed the second-highest strain around the implant, with the zirconia being significantly greater than all abutments, with the exception of the patient-specific abutment, and the patient-specific abutment being significantly greater than the straight contoured abutment in titanium and also zirconia (P<.05). CONCLUSIONS: The name brand patient specific titanium and Atlantis zirconia abutments conferred the most tensile strain to the implants. When selecting an abutment for a cement-retained crown on a tapered screw-vent implant, practitioners should consider the abutment material and the manufacturer of the abutment because not all abutments that fit in an individual implant transmit the strains in the same way.

Managing a fractured one-piece zirconia abutment with a modified plastic periodontal probe: A clinical report.

This clinical report describes the management of a fractured 1-piece zirconia stock abutment from an implant with an internal connection using a modified plastic periodontal probe. This minimally invasive approach allows for the retrieval of fractured prosthetic components without causing irreversible damage to the implant's platform or its internal threads and does not require special equipment or costly instruments.

Evaluation of patient experience and satisfaction with CAD-CAM-fabricated complete dentures: A retrospective survey study.

STATEMENT OF PROBLEM: Reports of sound, evidence-based treatment outcomes of computer-aided design and computer-aided manufacture (CAD-CAM) of complete dentures (CD) are lacking in publication databases. PURPOSE: The purpose of this retrospective survey study was to assess patient preferences and satisfaction when treated with digitally fabricated CDs, by using a questionnaire. MATERIAL AND METHODS: A total of 50 patients who received digital CDs were included in this study. A 10-item questionnaire was sent to the patients in order to assess their satisfaction with their digital CD experience. The items, or statements listed, were concerned with patient satisfaction and also the treatment technique and final outcome. Results of patient satisfaction questions were evaluated using descriptive statistics, means, and medians. All statistical tests were performed using commercially available software. Responses to the questionnaire provided by patients were analyzed using the Mantel-Haenszel chi-squared test (α=.05). RESULTS: The questionnaire was sent to 50 patients, and the total patient response rate after treatment intervention was 38% (n=19). Data obtained from questionnaire responses revealed that patients were generally pleased and satisfied with digital CDs. The chi-squared test results revealed no statistically significant differences (P=.180) in the ratings of experienced CD wearers. However, 70% of experienced CD patients agreed that their new digital CDs were "better" than their previous set of CDs. In all categories evaluated, patients gave positive responses regarding their digital CDs. CONCLUSIONS: Results of this questionnaire-driven study suggest that ratings from experienced CD wearers rehabilitated with CAD-CAM-fabricated CDs did not differ significantly from their previous ratings of conventional CDs, but overall, their satisfaction ratings of their digital CDs tended to be positive.

Clinical performance of CAD-CAM-fabricated complete dentures: A cross-sectional study.

STATEMENT OF PROBLEM: Computer-aided design and computer-aided manufacture (CAD-CAM)-fabricated complete dentures (CD) seek to address the disadvantages associated with conventional CD fabrication. However, few if any randomized clinical trials, cross-sectional, and/or retrospective analyses are available for the clinical performance of CAD-CAM-fabricated CDs. PURPOSE: The purpose of this retrospective study was to evaluate clinician experience with digital CD fabrication attempted in a 2-visit protocol. The actual number of appointments required for insertion and the number of postinsertion adjustment visits, and whether the incidence of treatment complications was related to operator experience were recorded and evaluated. MATERIAL AND METHODS: Patients who had received CAD-CAM-fabricated CDs were identified from a retrospective chart review. The number of appointments needed to insert digital CDs in attempting the 2-visit fabrication protocol marketed by the company, the number of postinsertion adjustments, and the reported complications were counted. There was no control group for comparative purposes used in this study. Whether the experience level of the operator influenced the frequency of a complication, the number of appointments needed to insert the definitive prostheses, and the number of postinsertion visits was determined by using an analysis of variance assessed at the 95% confidence level (α=.05). The frequency of a complication at each of the levels of operator experience was analyzed using the Exact Mantel-Haenszel chi-square test. RESULTS: Of the 48 rehabilitated participants, 24 participants were treated at the predoctoral level and 24 were treated at the graduate prosthodontics resident level. A total of 31 participants satisfied the true 2-visit fabrication protocol, and the remaining 17 participants required additional clinical visits because of complications on the day of insertion. The CD prostheses of 5 participants from the sample population required remaking using the conventional method. The mean number of postinsertion adjustment visits was 2.08. Of the 90 arches completed, 22 prostheses could not be inserted at the second appointment. CONCLUSIONS: The mean number of appointments needed to insert the prostheses in both groups was 2.39 visits--not 2 as claimed by the company. The most common types of complications observed were lack of denture retention, inaccurate occlusal vertical dimension, and incorrect centric relation.

Anteroposterior Spread and Cantilever Length in Mandibular Metal-Resin Implant-Fixed Complete Dental Prostheses: A 7- to 9-Year Analysis.

PURPOSE: The purpose of this retrospective study was to investigate the relationship of specific prosthetic complications in patients with a maxillary complete removable dental prosthesis (CRDP) opposing a mandibular metal-resin implant-fixed complete dental prosthesis (MRIFCDP) with respect to anteroposterior (AP) spread and cantilever length. MATERIALS AND METHODS: Of the 46 patients contacted for this study, 23 patients responded. All patients had been treated with a maxillary CRDP and a mandibular MRIFCDP. They were reviewed for prosthetic complications, and the AP spread and cantilever length were evaluated. A polyvinyl siloxane impression was made of each MRIFCDP so that cantilever length and AP spread could be measured. The average recall time was 8.5 years. The mechanical complications noted were screw-related complications, including both the prosthetic and the abutment screw, consisting of loosening and/or fracture, and fracture of the metal framework. Three different individuals repeated each measurement three times. Inter- and intrarater reliability was evaluated with the intraclass correlation coefficient, and a linear regression analysis of age and average cantilever length to AP spread ratio was calculated. In addition, calculations using this ratio were divided into two groups (> 2.1 and ≤ 2.1) and examined with each variable individually. A logistic regression analysis was performed for a comparison between the two AP spread ratio groups by age, right cantilever length, left cantilever length, average cantilever length, posterior spread, and failures. RESULTS: None of the predictor values was significant for the linear regression analysis of age, cantilever length, and AP ratio on number of failures. There was no significance in complications between the groups that had an AP spread ratio > 2.1 and groups that had an AP spread ratio ≤ 2.1. CONCLUSIONS: There was no statistical significance in predicting whether a screw-related complication would occur in relation to age, cantilever length, or AP spread ratio. There was no increase or decrease in complications whether the AP spread ratio was greater than or less than or equal to 2.1. In mandibular MRIFCDPs opposing maxillary complete denture situations, screw-related complications may be less likely regardless of the patient's age, cantilever length, or AP spread ratio of the prosthesis.

Displacement of Implant Abutments Following Initial and Repeated Torqueing.

PURPOSE: To measure and compare the three-dimensional (3D) position of nine different abutments manufactured by different manufacturers after repeated torqueing on an internal-hexagon implant. MATERIALS AND METHODS: Nine tapered implants were placed into an acrylic resin block. Five specimens each of nine different abutments (n = 45) were placed into one of nine implants. The abutments were handtightened and then torqued to the manufacturer-recommended torque of 30 Ncm. After 10 minutes, 30 Ncm of torque was reapplied. Another 10 minutes elapsed before testing was completed. Images were recorded in 12-second intervals. The spatial relationship of the abutments to the resin block was determined using 3D digital image correlation. Commercial image correlation software was used to analyze the displacements. Mean displacements for the abutments were calculated in three dimensions and overall for both torque applications. Statistical comparisons were done with a t test and a step-down Bonferroni correction. RESULTS: The overall 3D displacement of the Atlantis Titanium abutment after the second applied torque was significantly greater than that of two of the eight other abutments. Displacement in all three dimensions for the Atlantis Titanium abutment changed direction between the first and second torque applications. All abutments moved further in the same direction except for the Atlantis Titanium abutment, which moved back toward its original hand-tightened position horizontally after the second torque application. CONCLUSION: Re-torqueing of abutments after a 10-minute interval leads to minor displacement of varying degrees between the abutment and a tapered implant. A potential effect of embedment relaxation and/or manufacturing errors should be taken into consideration when selecting an abutment for a cement-retained crown on a tapered implant. Accordingly, clinicians may benefit from adjusting cement-retained implant crowns after re-torqueing the abutments to prevent potential occlusal and interproximal contact problems.

Three-Dimensional Displacement of Nine Different Abutments for an Implant with an Internal Hexagon Platform.

PURPOSE: Clinicians need to know whether there are any differences among the many abutment options available for restoring a particular implant. This study aims to compare nine abutments for one implant system for positional changes between hand tightening and torqueing. MATERIALS AND METHODS: Nine Tapered Screw-Vent (TSV) implants were placed into a resin block. Five specimens of nine different abutments (n = 45) were tried in one of the nine implants. Initially, the abutments were torqued to 20 Ncm to represent hand tightening. Abutments were tightened to 30 Ncm using a torque driver as recommended by the manufacturer for final seating. Images were recorded in 12-second intervals for approximately 10 minutes after the torque was applied. The spatial relationship of the abutments to the resin block was determined using three-dimensional digital image correlation. Commercial image correlation software was used to analyze the displacements. Mean displacements for the nine different abutments were calculated in all three dimensions and for overall displacement in space. A t test with a step-down Bonferroni correction was used for a pairwise comparison of each abutment's mean displacements to the other abutments to determine statistical differences (α = .05). RESULTS: The Atlantis titanium, Inclusive titanium, and Legacy zirconia abutments showed mean displacements that were statistically significantly higher than other abutments in the horizontal direction. The overall three-dimensional displacement of the Atlantis titanium abutment after an applied 30-Ncm torque was significantly higher than that of six of the other eight abutments (P < .0144). CONCLUSION: Within the limitations of this in vitro study, the Zimmer PSA demonstrated less displacement between hand tightening and torqueing than the Atlantis titanium or Inclusive titanium abutments when used to restore a TSV implant.

Load to failure of different titanium abutments for an internal hexagon implant.

STATEMENT OF PROBLEM: Several aftermarket abutments are available for a commonly used internal hexagonal connection implant. However, their load to failure performance is unknown when compared with the manufacturer's abutment. PURPOSE: The purpose of this in vitro study was to conduct a load to failure comparison of 5 different titanium abutments (manufacturer's and aftermarket) for cement-retained restorations used on an implant with an internal hexagon connection. MATERIAL AND METHODS: Five implants (Tapered Screw-Vent, 4.1×11.5 mm; Zimmer Dental) were individually secured in a loading apparatus, and 3 abutment specimens of each of the 5 different titanium abutments (Atlantis, AstraTech TiDesign, Legacy Straight Contoured, Inclusive Custom, and Zimmer PSA) (n=15 total) were loaded at a 30-degree angle until fracture of the implant abutment complex. Data for load to fracture were compared with analysis of variance and a Tukey-Kramer post hoc test (α=.05). RESULTS: Significant differences were noted between the fracture loads of some abutment pairs; Atlantis-AstraTech TiDesign, Atlantis-Legacy Straight Contoured, AstraTech TiDesign-Legacy Straight Contoured, Inclusive Custom-AstraTech TiDesign, and Inclusive Custom-Legacy Straight Contoured (P<.05). The highest overall resistance to fracture was achieved by the Legacy Straight Contoured Abutment, which was significantly greater than all other aftermarket abutments (P<.05). Tested abutments fractured at an average of 649.17 N. The Zimmer PSA abutment was the only abutment that showed no fracture of any of the components before implant failure. CONCLUSION: When comparing manufacturer's versus aftermarket brands, the manufacturer's abutment (Zimmer PSA) was the only abutment without fracture of any of the components. Aftermarket brands experienced screw fractures, which could result in further clinical prosthetic complications. The clinical implications of these findings need further investigation.

Load to failure of different zirconia abutments for an internal hexagon implant.

STATEMENT OF PROBLEM: Various zirconia abutment designs are available to restore implant systems. Fracture resistance is one of the criteria involved in selecting among these options. PURPOSE: The purpose of this in vitro study was to measure and compare load to failure for 5 zirconia abutments for an internally hexagon implant. MATERIAL AND METHODS: Five 4.1×11.5-mm Zimmer tapered screw-vent implants were individually secured in a loading apparatus, and 3 specimens of each of the 5 different abutments (Zimmer Contour with a Ti ring, anatomic-contour Atlantis-Zr, anatomic-contour Inclusive-Zr, anatomic-contour Astra Tech ZirDesign, Legacy Straight Contoured abutment with Ti core) (N=15) were loaded at a 30-degree angle until the implant abutment complex failed. Data for load to failure were compared with analysis of variance and a Tukey-Kramer post hoc test (α=.05). RESULTS: The custom anatomic-contour abutment (Inclusive) showed the lowest load to fracture, and the stock anatomic-contour (AstraTech ZirDesign) the second lowest load to fracture. These were significantly lower than all other abutments (P<.05). The highest overall fracture strength was of a zirconia abutment with a titanium core-hexagon (Legacy Straight Contoured), which was significantly greater than all other abutments (P<.05). Anatomic-contour zirconia abutments fractured at an average of 275 N compared with the average fracture load of 842 N for zirconia abutments with titanium component (P<.05). CONCLUSION: The stock zirconia abutment with a titanium ring and the zirconia abutment with a titanium core-hexagon (Legacy Straight Contoured) had significantly greater fracture resistance than that of any of the 1-piece anatomic-contour zirconia abutments tested.

Comparison of retention and stability of two implant-retained overdentures based on implant location.

STATEMENT OF PROBLEM: The location of dental implants and the choice of retentive attachments for implant-retained overdentures are selected based on clinician preference, expert opinion, or empirical information. Limited information is available regarding implant position and the effect on the retention and stability of 2-implant mandibular implant overdentures. PURPOSE: The purpose of this investigation was to evaluate the effect of implant location on the in vitro retention and stability of a simulated 2-implant-supported overdenture and to examine the differences among different attachment systems. MATERIAL AND METHODS: A model that simulates a mandibular edentulous ridge with dental implants in positions that approximate tooth positions, and a cobalt-chromium cast framework attached to a universal testing machine was used to measure the peak load (N) required to disconnect the attachments. Four different types of attachments (Ball/Cap, ERA, Locator, and O-Ring) were used in sequence in various positions on the model to evaluate the effect of implant location on the retention and stability of a simulated 2-implant-retained overdenture. Means were calculated, and differences among the systems, directions, and groups were identified by using a repeated measured ANOVA (α=.05). For differences observed between measurements, the Bonferroni post hoc method at the 5% level of significance was used to determine the location and magnitude of difference. RESULTS: The interactions between the attachment system, direction of force, and implant location were statistically significant (P=.01). The vertical retention and horizontal stability of a simulated overdenture prosthesis increased with the distal implant location up to the second premolar, and the anteroposterior stability increased with distal implant location. The attachment type affected retention and stability differently by location. Ball attachments produced the highest levels of retention and stability, followed by Locator (pink), O-Ring, and ERA (orange). CONCLUSIONS: The retention and stability of a 2-implant simulated overdenture prosthesis is significantly affected by implant location (P=.01) and abutment type (P=.01).

Implant-abutment interface: a comparison of the ultimate force to failure among narrow-diameter implant systems.

STATEMENT OF PROBLEM: Limited available alveolar ridge bone and space deficiencies are some of the challenging scenarios that have led many dental implant manufacturers to develop narrow-diameter implants of various designs. Clinicians may have concerns about the durability and function of the narrow-diameter implants. PURPOSE: The purpose of this study was to explore and compare the ultimate failure resistance of the smallest diameter of the 2-stage type implant provided by 5 commonly used dental implant systems. MATERIAL AND METHODS: Thirty implants, Astra OsseoSpeed 3.0 mm and 3.5 mm, Straumann Bone Level 3.3 mm, Zimmer Tapered Screw-Vent 3.7 mm, Full Osseotite Certain 3.25 mm, and NobelSpeedy Replace 3.5 mm, 5 of each type, were tested in this study. A rigid clamp was used to hold the implants at a 30-degree angle to a static load vector. The load continued until the specimen broke or obviously deformed. Peak loads were recorded at that point for all the studied implant systems. Student t test and 1-way ANOVA were used to compare the mean peak load values (α=.05). RESULTS: The mean fracture/deformation peak load values were 367.20 N ± 98.05 for Astra OsseoSpeed 3.0 mm; 568.80 N ± 85.24 for Astra OsseoSpeed 3.5 mm; 679.00 N ± 81.09 for Full Osseotite Certain 3.25 mm; 553.4 N ± 56.96 for NobelSpeedy Replace 3.5 mm; 802.80 N ± 134.50 for Zimmer Tapered Screw-Vent 3.7 mm; and 576.20 N ± 71.45 for Straumann Bone Level 3.3 mm. Generally, a higher load was required to cause failure in implants with larger diameters than in narrower-diameter implants, and more force was necessary to cause failure in Ti6Al4V alloy implants than in commercially pure titanium implants. CONCLUSIONS: With regard to implant diameter and ultimate failure strength, Osseotite Certain 3.25 mm was considered to be more advantageous in comparison with the other implants tested.

A technique for retrieving fractured implant screws.

The use of dental implants as a source of support and retention for fixed restorations is common. This report describes the use of a fragment removal instrument together with the use of ultrasonic instrumentation to retrieve a screw fragment.