Prospective cohort study to evaluate narrow diameter implants for restoration of a missing lateral incisor in patients with a cleft palate: One-year results.

STATEMENT OF PROBLEM: Patients diagnosed with a cleft palate often have a congenitally missing maxillary lateral incisor. The congenital cleft presents the practitioner with challenges including the quantity and quality of bone, a surgically managed cleft correction, and limited clinical space. PURPOSE: The purpose of the present prospective investigation was to report preliminary results at the 1-year follow-up for this planned 5-year investigation of narrow diameter implants used to restore a missing lateral incisor in patients with a cleft palate. MATERIAL AND METHODS: Fourteen study participants with a cleft palate and a missing maxillary lateral incisor were enrolled based on established criteria. Narrow diameter implants (AstraTech OsseoSpeed TX 3.0S and 3.5 mm) were placed by using a 2-stage protocol and restored. All study participants received an Atlantis abutment and a cement-retained crown. Four probing depth measurements and bleeding on probing were measured at baseline and at 1 year. Probing depth measurements were evaluated using a 2-way repeated measures ANOVA with Tukey-Kramer multiple comparisons tests. Radiographic marginal bone loss was measured at 1-year by using a digital subtraction technique and evaluated by using a repeated measures ANOVA. Pretreatment cone beam computed tomography (CBCT) images were used to measure a mean gray level that was proportional to bone mineral density (BMD) in the implant site. One-way mixed ANOVA was used to compare the mean gray level and average implant stability quotient (ISQ) loading. A Pearson correlation was also tested between those parameters (α=.05) for each statistical analysis. RESULTS: The mean marginal bone loss at 1 year was 0.601 ±0.48 mm. Regarding probing depth measurements, a 2-way repeated measures ANOVA found both the location (P=.012) and time (P=.009) were significant. The Tukey-Kramer multiple comparisons test showed a significant difference between the buccal and distal site (P=.006) from baseline to 1-year follow-up. CONCLUSIONS: Narrow diameter implants are a reliable treatment for replacing a missing lateral incisor in patients with a cleft palate at 1 year, with an implant survival rate of 100% and implant success rate of 94% using the established criteria. A negative association was found between the bone mineral density and the implant stability in the alveolar cleft site of a patient with a cleft palate. The peri-implant soft tissue probe depths exhibited significant change during the first year.

Rescue of an implant-supported fixed complete prosthesis after the failure of an implant: A dental technique.

This technique article describes the rescue of an existing implant-supported fixed complete prosthesis after the failure of a supporting implant. To achieve this, a system able to rescue the fixed prosthesis after placement of a new implant was used, and the protocol for performing this procedure is described.

Dislodgement force analysis of an overdenture attachment system.

STATEMENT OF PROBLEM: The performance of a recently introduced overdenture attachment system after cyclic dislodgement is not known. PURPOSE: The purpose of this in vitro study was to compare a conventional attachment system and a recently introduced attachment system for their dislodgement forces before and after cyclic dislodgement. MATERIAL AND METHODS: Three acrylic resin models were fabricated with 2 implant analogs (4.1 mm; Zimmer Dental) in different angulations; parallel in the first, divergent by 30 degrees in the second, and divergent by 60 degrees in the third model. Six acrylic resin blocks containing 2 metal housings of 2 different LOCATOR attachments (LOCATOR Legacy [LL], R-Tx, n=3; Zest Dental Solutions) were also fabricated. LOCATOR abutment pairs (LL and R-Tx) were placed onto the analogs. Seven specimens for LL and R-Tx with pink attachments were tested for dislodgement forces, and the values were recorded before and after 1440 times (simulated 1-year use) of cyclic dislodgement using an occlusal loading simulator machine. A 3-way ANOVA was used for dislodgement force comparison before and after cyclic dislodgement for different angulations and for 2 different LOCATOR attachments. Any significant differences were identified with the Tukey HSD test (α=.05). The percentage decrease in the dislodgement force was also calculated. RESULTS: A significant 3-way interaction was found for the LOCATOR type, implant angle, and time (P<.001). LOCATOR type made a difference for only parallel and 60 degree-divergent implants before cyclic dislodgement (P≤.022). After cyclic dislodgement, a significant effect of the LOCATOR type on dislodgement force was found for only parallel implants (P=.034). In both LOCATOR systems, the dislodgement force was different (P<.001) among different implant angulations, except for parallel to 30-degree comparison, before and after cyclic dislodgement. For both LL and R-Tx, significant differences (P≤.022) were found between before and after cyclic dislodgement for all angulations except LL in parallel (P=.214). CONCLUSIONS: When implants were parallel, initially, the dislodgement force of R-Tx was higher than that of LL; however, the forces were similar after cyclic dislodgement. When implants were divergent by 30 degrees, there were no differences between the dislodgement forces of the LOCATOR systems before and after cyclic dislodgement. When implants were divergent by 60 degrees, initially, the dislodgement force of LL was higher than that of R-Tx; however, the forces were similar after cyclic dislodgement. Before and after cyclic dislodgement, in each system, dislodgement forces were greater when implants were divergent by 60 degrees than when parallel and 30 degrees. After cyclic dislodgement, dislodgement forces decreased for both systems, except for LL when the implants were parallel.

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.

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.

Distortion of CAD-CAM-fabricated implant-fixed titanium and zirconia complete dental prosthesis frameworks.

STATEMENT OF PROBLEM: Computer-aided design and computer-aided manufacturing (CAD-CAM)-fabricated titanium and zirconia implant-supported fixed dental prostheses have become increasingly popular for restoring patients with complete edentulism. However, the distortion level of these frameworks is not well known. PURPOSE: The purpose of this in vitro study was to compare the 3-dimensional (3D) distortion of CAD-CAM zirconia and titanium implant-fixed screw-retained complete dental prostheses. MATERIAL AND METHODS: A master edentulous model with 4 implants at the positions of the maxillary first molars and canines was used. Multiunit abutments (Nobel Biocare) secured to the model were digitally scanned using scan bodies and a laboratory scanner (S600 ARTI; Zirkonzahn). Titanium (n=5) and zirconia (n=5) frameworks were milled using a CAD-CAM system (Zirkonzahn M1; Zirkonzahn). All frameworks were scanned using an industrial computed tomography (CT) scanner (Nikon/X-Tek XT H 225kV MCT Micro-Focus). The direct CT scans were reconstructed to generate standard tessellation language (STL) files. To calculate the 3D distortion of the frameworks, STL files of the CT scans were aligned to the CAD model using a sum of the least squares best-fit algorithm. Surface comparison points were placed on the CAD model on the midfacial aspect of all teeth. The 3D distortion of each direct scan to the CAD model was calculated. In addition, color maps of the scan-to-CAD comparison were constructed using a ±0.500 mm color scale range. RESULTS: Both materials exhibited distortion; however, no significant difference was found in the amount of distortion from the CAD model between the materials (P=.747). Absolute values of deviations from the CAD model were evident in the x and y plane and less so in the z direction. CONCLUSIONS: Zirconia and titanium frameworks showed similar 3D distortion compared with the CAD model for the tested CAD-CAM and implant systems. The distortion was more pronounced in the horizontal and sagittal plane than in the vertical plane.

Comparison of 3D displacements of screw-retained zirconia implant crowns into implants with different internal connections with respect to screw tightening.

STATEMENT OF PROBLEM: Internal conical implant-abutment connections without horizontal platforms may lead to crown displacement during screw tightening and torque application. This displacement may affect the proximal contacts and occlusion of the definitive prosthesis. PURPOSE: The purpose of this in vitro study was to evaluate the displacement of custom screw-retained zirconia single crowns into a recently introduced internal conical seal implant-abutment connection in 3D during hand and torque driver screw tightening. MATERIAL AND METHODS: Stereolithic acrylic resin models were printed using computed tomography data from a patient missing the maxillary right central incisor. Two different internal connection implant systems (both ∼11.5 mm) were placed in the edentulous site in each model using a surgical guide. Five screw-retained single zirconia computer-aided design and computer-aided manufacturing (CAD-CAM) crowns were fabricated for each system. A pair of high-resolution digital cameras was used to record the relationship of the crown to the model. The crowns were tightened according to the manufacturers' specifications using a torque driver, and the cameras recorded their relative position again. Three-dimensional image correlation was used to measure and compare crown positions, first hand tightened and then torque driven. The displacement test was repeated 3 times for each crown. Commercial image correlation software was used to extract the data and compare the amount of displacement vertically, mesiodistally, and buccolingually. Repeated-measures ANOVA calculated the relative displacements for all 5 specimens for each implant for both crown screw hand tightening and after applied torque. A Student t test with Bonferroni correction was used for pairwise comparison of interest to determine statistical differences between the 2 implants (α=.05). RESULTS: The mean vertical displacements were statistically higher than the mean displacements in the mesiodistal and buccolingual directions for both implants (P<.001). Mean displacements in all directions were statistically significant between iterations for both implants (P<.001). No statistically significant differences were found for displacements between implants at different directions and at different iterations (P>.05). CONCLUSIONS: Within the limitations of this in vitro study, screw-retained zirconia crowns tended to displace in all 3 directions, with the highest mean displacement in the vertical direction at iteration 1. However, the amount of displacement of crowns between the 2 different implants was statistically insignificant for all directions and iterations.

In vitro fit of CAD-CAM complete arch screw-retained titanium and zirconia implant prostheses fabricated on 4 implants.

STATEMENT OF PROBLEM: Computer-aided designed and computer-aided manufactured (CAD-CAM) titanium and zirconia implant-supported fixed implant prostheses on 4 implants have become popular. The precision and accuracy of their interface fit has not been widely researched. PURPOSE: The purpose of this in vitro study was to compare the marginal fit of zirconia and titanium implant-supported screw-retained CAD-CAM complete fixed dental prostheses (CFDP) fit with a standardized cast simulating the all-on-4 implant distribution. MATERIAL AND METHODS: Representation of an edentulous maxilla with 4 multiunit replicas embedded in sites corresponding to the positions of the maxillary first molars and canines was chosen. Multiunit abutments were digitally scanned using scan bodies and a laboratory scanner. CAD software was used to design screw-retained implant-fixed complete prostheses framework, and the file was sent to a milling machine for CAM. Titanium (n=5) and zirconia (n=5) frameworks were milled on 4 implants, and the frameworks were scanned with an industrial computed tomography (CT) scanner while applying the 1-screw test. The direct CT scans were reconstructed to generate a standard tessellation language (STL) file from the voxel data set and transported to volume graphics analysis software from which measurements were extracted. The circular mating surfaces of the corresponding framework interfaces to their representative multiunit abutment replicas on the standard were measured for implant position left maxillary canine (LMC), implant position right maxillary canine (RMC) and implant position right maxillary first molar (RMFM). In addition, color maps were generated to show the marginal discrepancy between the mating surfaces using ±0.500 mm color scale ranges. RESULTS: The material type (zirconia or titanium) was not significant for 3D discrepancy measurements (P=.904). However, 3D discrepancy measurement values were significantly different between RMC and RMFM within each group (P<.001). The mean 3D ±SD discrepancy measurement for LMC for titanium was 48.2 ±2.6 µm. The mean ±3D discrepancy measurement for RMC for titanium was 74 ±15 µm and 84.4 ±12.1 µm for zirconia. The mean 3D discrepancy measurement for RMFM for titanium was 102 ±26.7 µm and 93.8 ±30 µm for zirconia. All 3D discrepancy measurements showed values <135 µm. CONCLUSIONS: Within the limitations of the present in vitro study, implant-supported CAD-CAM fabricated titanium and zirconia complete fixed dental prosthesis frameworks showed comparable marginal fit. Three-dimensional microgap measurements of frameworks showed clinically acceptable misfit values. Absolute passive fit was not achieved.

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.

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.

Load to failure of different zirconia implant abutments with titanium components.

STATEMENT OF PROBLEM: Abutments with a zirconia superstructure and a titanium insert have recently become popular. Although they have been tested under static load, their performance under simulated mastication is not well known. PURPOSE: The purpose of this in vitro study was to compare the cyclic load to failure of 3 types of zirconia abutments with different mechanisms of retention of the zirconia to the titanium interface. MATERIAL AND METHODS: Fifteen implants (n=5 per system) and abutments (3 groups: 5 friction fit [Frft]; 5 bonded; and 5 titanium ring friction fit [Ringfrft]) were used. Abutments were thermocycled in water between 5°C and 55°C for 15000 cycles and then cyclically loaded for 20000 cycles or until failure at a frequency of 2 Hz by using a sequentially increased loading protocol up to a maximum of 720 N. The load to failure for each group was recorded, and 1-way analysis of variance was performed. RESULTS: The mean load-to-failure values for the Frft group was 526 N, for the Bond group 605 N, and for the Ringfrft group 288 N. A statistically significant difference was found among all abutments tested (P<.05). CONCLUSIONS: Abutments with the bonded connection showed the highest load-to-failure value, and the abutment with the titanium ring friction fit connection showed the lowest load-to-failure value.

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.

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.

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.

An alternative conversion technique for fabricating an interim fixed implant-supported complete arch prosthesis.

The conversion technique enables the immediate loading of implants using an existing or a new complete denture. Acrylic resin is generally used directly intraorally when the conventional conversion technique is used. The technique described suggests picking-up the interim copings and capturing the soft tissue contour with the conversion prosthesis with a polyether impression material when 4 implants are placed with an angled implant protocol. A polyether impression was made to complete an autopolymerized reline jig reline. Acrylic resin was applied on the cast generated from this impression outside the oral cavity. This technique may minimize chair time and maximize the ability of the technician/clinician to adapt the prosthesis to the soft tissue contour.

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.

Effect of long-term steam autoclaving on changes in torque delivery of spring- and friction-type torque wrenches.

STATEMENT OF PROBLEM: Two types of mechanical torque-limiting devices (MTLD) are available: friction-style and spring-style. Limited information is available regarding the accuracy of different types of MTLDs after sterilization. PURPOSE: The purpose of this in vitro study was to determine the accuracy of MTLDs after sterilization. MATERIAL AND METHODS: Three new friction-style and 3 new spring-style MTLDs (Astra Tech/Dentsply, Zimmer Dental, Biohorizons, Biomet 3i, Straumann [ITI] and Nobel Biocare; n=5 per manufacturer; 30 total) were selected to evaluate their accuracy in delivering the target torque values preset by their manufacturers before and after sterilization. Target torque measurements were made with a digital torque gauge (model DFS2-R-ND; Chatillon) 10 times for each device. All MTLDs were sterilized following the manufacturers' recommendations. The sterilization procedure was repeated 100 times, and the accuracy of all MTLDs was retested. Absolute torque differences were analyzed using a repeated measures analysis of variance with instrument as the repeated factor. MTLD type (friction or spring) and MTLD status (new or autoclaved) were the independent variables. Post hoc testing was done using the Tukey method for balanced data. RESULTS: No significant difference was found between the spring-style and friction-style MTLDs or within the spring-style and friction-style MTLDs before and after sterilization (P>.05). CONCLUSIONS: After 100 cycles of steam autoclaving, the accuracy of spring-style and friction-style MTLDs was similar. All MTLDs fell within ±10% of the target torque value before and after sterilization.

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.

Using the "final-on-four" concept to deliver an immediate metal-resin implant-fixed complete dental prosthesis.

In traditional dental implant therapy, the time between implant placement and delivery of the definitive prosthesis can be long and uncomfortable for a patient wearing a conventional removable denture on an atrophied ridge. New clinical protocols, often with tilted implants, are being used to immediately restore mandibular implants with interim restorations, thus shortening the patient's return to function. However, these conversion type interim restorations do not decrease the time to definitive prosthetic rehabilitation. The Ohio State University (OSU) developed an immediate load surgical and prosthetic protocol to compensate for the disadvantages of previous techniques. With this protocol, a custom, definitive, screw-retained metal-resin fixed prosthesis can be delivered 2 to 4 days postoperatively and has been described using 5 implants. This clinical report presents the OSU immediate loading protocol, combined with a tilted implant technique, for the fabrication of a mandibular metal-resin implant fixed complete dental prosthesis (MRIFCDP) in 3 days postoperatively and with only 4 implants. Replacing the mandibular dentition with an immediate load-fixed metal-resin prosthesis by means of the "final-on-four" technique resulted in a custom, definitive, and functional restorative solution immediately after surgery.