Passively fitting implant-supported complete-arch interim restoration

This article presents a technique for fabricating a passively fitting implant-supported screw-retained complete-arch interim restoration with resistance to early fracture. Two gypsum casts were obtained from an implant impression using the splinting technique. The complete-arch interim restoration with abutment access holes, which was reinforced with a glass fiber splint, was fabricated on one cast and connected to restorative abutments on the other cast extraorally to eliminate stresses from the polymerization shrinkage of resin.     

A completely digital workflow for an interim implant-supported crown: A clinical report

This article describes a completely digital workflow for the diagnostic phase, surgical and prosthetic planning, extraction, immediate single implant placement by guided surgery, and interim implant-supported crown. From a virtual impression, zirconia abutments and a polymethylmethacrylate (PMMA) interim crown was planned in a computer-aided design (CAD) software program. This workflow shortened the time required for chairside placement of an interim restoration with enhanced function and esthetics while restoring an anterior mandibular tooth lost after trauma.     

Transforming an existing fixed provisional prosthesis into an implant-supported fixed provisional prosthesis with the use of healing abutments

Maintaining a fixed provisional prosthesis through all phases of complex implant prosthodontic therapy for a soon-to-be completely edentulous arch is a difficult task. This article focuses on the treatment phase in which teeth and/or transitional implants supporting a provisional fixed partial denture are removed. The described technique makes use of healing abutments to support a modified provisional fixed partial denture. This protocol ensures patient comfort and allows proper soft tissue healing before definitive implant abutment selection. It also eliminates the placement of interim implant abutments.     

In vitro resistance of reinforced interim fixed partial dentures

STATEMENT OF PROBLEM: Comprehensive restorative dental treatment often necessitates the use of interim fixed partial dentures (FPDs) with high stiffness, especially in long-span restorations or areas of heavy occlusal stress. PURPOSE: This in vitro study evaluated the fracture load of interim FPDs made with various materials and span lengths. MATERIAL AND METHODS: Groups (n = 3) of interim FPDs were fabricated with prosthodontic resin materials on 2 abutments with 3 different pontic widths of 3 units (12 mm), 4 units (19 mm), and 5 units (30 mm). The following materials were tested: (1) a thermoplastic polymer (Promysan Star), (2) Promysan Star with a veneering composite (Vita Zeta), (3) a nonimpregnated polyethylene fiber reinforced resin (Ribbond) with a veneering composite (Sinfony), (4) an impregnated fiber reinforced composite system (Targis/Vectris), and (5) a conventional polymethyl methacrylate, Biodent K+B, (control group). After 5000 thermocycles in 2 water baths at 5 degrees and 55 degrees C, the FPDs were temporarily fixed with a provisional cement on the corresponding abutments and subjected to 3-point bending until fracture by a universal testing machine. Statistical analysis consisted of an analysis of variance (ANOVA, 1-way, 2-way) and Bonferroni-Dunn's multiple comparisons post hoc analysis for test groups (alpha = .05). RESULTS: Fracture resistance (N) differed significantly for 3 (mean: 640 +/- 146 N), 4 (626 +/- 229 N), and 5 unit (658 +/- 98 N) Targis/Vectris FPDs compared with the corresponding Promysan (284 +/- 21 N to 125 +/- 73 N), Biodent K+B (247 +/- 91 N to 218 +/- 85 N), and Promysan/Vita Zeta (95 +/- 15 N to 82 +/- 6 N) groups (P < .05). Significant differences were obtained for the 4 and 5 unit Targis/Vectris FPDs compared with the Sinfony/Ribbond FPDs (281 +/- 25 N - 252 +/- 74 N) for the corresponding pontic spans. CONCLUSION: Within the limitations of this in vitro study the impregnated fiber reinforcement may considerably enhanced the fracture resistance of interim FPDs of different span lengths.     

Effect of pontic height on the fracture strength of reinforced interim fixed partial dentures

OBJECTIVES: This in vitro study evaluated the fracture load of interim FPDs made with various materials and pontic heights. The hypothesis was that different materials and pontic heights result in different fracture resistance. METHODS: Groups of interim FPDs were fabricated with prosthodontic resin materials on two abutments with two different pontic heights (4.3 and 5.8 mm) and a pontic width of 4 units (19 mm) (n = 3). The following materials were tested: (1) a thermoplastic polymer (Promysan Star), (2) Promysan Star with a veneering composite (Vita Zeta), (3) a non-impregnated polyethylene fiber reinforced resin (Ribbond) with a veneering composite (Sinfony), (4) an impregnated fiber reinforced composite system (Targis/Vectris), and (5) a conventional poly methyl methacrylate (PMMA) (Biodent K+B, control group). After 5000 thermocycles, the FPDs were temporarily fixed with a provisional cement on the corresponding abutments and tested for fracture strength. One-way and two-way ANOVA and Bonferroni-Dunn's multiple comparison tests were performed for the statistical analysis (alpha = 0.05). RESULTS: The mean fracture strength ranged from 83.0 to 625.9 N for a pontic height of 4.3 mm and from 97.2 to 893.7 N for a pontic height of 5.8 mm. Vectris/Targis FPDs of both pontic heights exhibited significantly superior fracture resistance compared to the corresponding Promysan, Promysan/Vita Zeta, Ribbond/Sinfony and Biodent groups. Except Biodent FPDs, fracture resistance of FPDs with a pontic height of 4.3 mm showed no significant differences compared to a pontic height of 5.8 mm for each material. SIGNIFICANCE: Material type of the FPDs has a significant influence on the fracture strength, whereas pontic height has no significant effect (except control group).     

Ensuring passivity and retrievability for immediate complete-arch implant-supported prostheses

This technique describes the fabrication of frameworks for immediate complete-arch implant-supported prostheses to ensure that the dimensional alterations that occur during the casting procedure do not interfere with passivity. As sectioning and soldering are not necessary, there is no delay in the fabrication process, and the framework is not weakened. Titanium abutments for interim screw-retained prostheses are prepared on the definitive cast, and framework waxing preserves the access holes to the screws. After casting, the framework is cemented on the prepared abutments. The proposed technique has been created to combine the advantages of cement-retained frameworks and the retrievability of screw-retained ones.     

A digital technique for fabricating implant-supported interim restorations in the esthetic zone

A digital technique for fabricating an implant-supported interim restoration is presented. The labial cervical architecture of the natural tooth is captured before extraction and registered to form the emergence profile of the interim restoration. A well-contoured interim restoration is fabricated before surgery and connected to the immediately placed implant with a customized interim abutment.     

CAD/CAM to fabricate ceramic implant abutments and crowns: a preliminary in vitro study

Background:  This study evaluated the feasibility of fabricating implant abutments and crowns from pre-sintered feldspathic porcelain blocks using the chair-side CAD/CAM, CEREC3D^® system.
Methods:  Thirty-two implant analogues were divided into two groups. In the control group, prefabricated machined anatomical titanium (Ti) abutments were screw-retained to the analogues. In the test group, machined feldspathic porcelain abutments were cemented on prefabricated machined Ti links and screw-retained to the implant analogues. These feldspathic porcelain abutments were fabricated out of pre-sintered feldspathic porcelain blocks as duplicates of the abutments in the control group using the CAD/CAM, CEREC3D^® system. Thirty-two feldspathic porcelain crowns, also fabricated out of pre-sintered ceramic blocks, were then cemented with resin cement on all the abutments in both groups. All samples were subsequently subjected to fracture strength testing under static load. An unpaired t-test was used to compare fracture load values between the two groups.
Results:  The test group using feldspathic porcelain abutments and crowns showed statistically significant higher mean fracture strength than the control group with the Ti abutments and feldspathic porcelain crowns.
Conclusions:  This preliminary study showed that the chair-side CAD/CAM technology can be utilized to fabricate customized ceramic abutments with their associated ceramic crowns using pre-sintered feldspathic porcelain blocks.     

Bar attachments for overdentures with nonparallel abutments.

Bar attachments are easily fabricated and provide increased retention and support for overdentures. Nonparallel root abutments can preclude the routine use of bar attachments unless modifications are made in the design. This article reviews several existing techniques to successfully fabricate bar attachments in overdenture patients with nonparallel abutments. In addition, three alternative methods are presented for placing bar attachments on abutments with divergent roots.     

The use of healing abutments for the fabrication of cement-retained, implant-supported provisional prostheses

This article describes the intraoral preparation of healing abutments for use as prefabricated abutments for a cement-retained, implant-supported prosthesis. After the healing abutments are prepared, an impression is made with irreversible hydrocolloid, and the provisional restoration is fabricated indirectly. This technique is an easy and economical alternative for the fabrication of provisional fixed partial dentures or crowns but may be contraindicated for severely misaligned implants.     

Comparison of the effects of cement removal from zirconia and titanium abutments: An in vitro study

Statement of problem

Excess cement around dental implants is a significant cause of peri-implant inflammation. Research has focused on approaches to cement removal, the type of cement used, and the different instruments used for cement removal with titanium abutments. However, data comparing zirconia with titanium abutments are lacking.

The use of biomechanical orthodontic treatment concepts for removable appliances in maxillofacial prosthodontics. Part I: Review of prosthesis design principles

Maxillary cuspids are commonly included in ablative block resections in maxillectomy patients. Although the remaining incisors are poor abutments for interim or definitive obturators, they must be used if adequate retention and support is to be achieved. Orthodontic biomechanical concepts for removable appliances offer solutions for the treatment of these patients. The proper application of these concepts can improve retention, support, and force distribution to the anterior teeth and is particularly useful in younger patients when long-term maintenance of teeth is critical. The purpose of this article is to describe the rationale for this approach and its application to interim and definitive Aramany Class I and II obturators.     

A technique for fabricating a definitive immediate implant-supported prosthesis for the edentulous mandible

A technique for fabricating a definitive immediate fixed implant-supported prosthesis to rehabilitate the edentulous mandible is described. Temporary abutments were used first as impression copings, later modified to achieve parallelism, and finally incorporated in the definitive framework. The metal framework was fabricated with holes for the abutments and connected to the abutments with composite resin cement intraorally to obtain passive fit. This technique reduced the number of steps, thereby decreasing insertion time of the definitive prosthesis to 2 days.     

Comparison of CAD-CAM and traditional chairside processing of 4-unit interim prostheses with and without cantilevers: Mechanics,fracture behavior,and finite element analysis

Statement of problemHow processing by computer-aided design and computer-aided manufacturing (CAD-CAM) or traditional chairside fabrication techniques affects the presence of defects and the mechanical properties of interim dental prostheses is unclear.PurposeThe purpose of this in vitro study was to compare the effects of CAD-CAM versus traditional chairside material processing on the fracture and biomechanical behavior of 4-unit interim prostheses with and without a cantilever.Material and methodsTwo types of 4-unit interim prostheses were fabricated with abutments on the first premolar and first mandibular molar, one from a prefabricated CAD-CAM block and one with a traditional chairside polymer-monomer autopolymerizing acrylic resin (n=10). Both groups were assessed by compressive strength testing and additionally with or without a cantilevered second molar by using a universal testing machine with a 5-kN load cell. A finite element model (FEM) was built by scanning both prosthesis designs. Finite element analysis (FEA) replicated the experimental conditions to evaluate the stress distribution through the prostheses.ResultsInterim fixed prostheses manufactured by CAD-CAM showed significantly higher mean fracture loading values (3126 N to 3136 N) than for conventionally made interim fixed prostheses (1287 N to 1390 N) (P=.001). The presence of a cantilever decreased the fracture loading mean values for CAD-CAM (1954 N to 2649 N), although the cantilever did not influence the traditional prostheses (1268 N to 1634 N). The highest von Mises stresses were recorded by FEA on the occlusal surface, with the cantilever design, and at the transition region (connector) between the prosthetic teeth.ConclusionsInterim partial prostheses produced by CAD-CAM had a higher strength than those manufactured traditionally. The presence of a cantilever negatively affected the strength of the prostheses, although the structures manufactured by CAD-CAM still revealed high strength and homogenous stress distribution on occlusal loading.     

Comparison of strength of milled and conventionally processed PMMA complete-arch implant-supported immediate interim fixed dental prostheses

Statement of problemA typical conversion process of a complete-arch immediate loading protocol entails preparing holes in a complete denture for connection to interim copings, which reduces the strength of the prosthesis. The excellent mechanical properties of milled polymethyl methacrylate (PMMA) disks may provide interim prostheses with improved strength.PurposeThe purpose of this in vitro study was to measure the flexural strength and failure load of simulated acrylic resin immediate implant-supported interim prostheses fabricated by conventional processing and computer-aided manufacturing.Material and methodsA master patient model was created with an acrylic resin base and 2 BioHorizons Internal 4.5-mm-diameter implants placed with a 21.5-mm span and multiunit abutments (MUA) tightened to place. Two groups with different prosthodontic designs were used: one represented the standard fixed prosthesis with support at each end (noncantilever, NC), and the other group represented the cantilever portion of the prosthesis (cantilever, C). Two connection designs of prosthesis blocks to MUA abutments were evaluated: one with typical holes in the prosthesis for capturing interim copings and one with a low-profile coping. For the heat-processed PMMA groups (HP/NC and HP/C), wax patterns were milled, and heat-polymerized denture base PMMA prostheses were processed. The milled PMMA groups (M/NC and M/C) were milled from a tooth-shaded PMMA disk for the prosthesis blocks. The milled low-profile groups (Mlp/NC and Mlp/C) had identical dimensions except that connection to the low-profile coping was designed with a cement space and a narrow diameter screw access hole and was milled from a PMMA disk. The failure load (N) of the cantilever prostheses was recorded, and for NC groups, the 3-point flexural strength formula (MPa) was calculated. The Weibull modulus, characteristic strength, and summary statistics were computed, and the groups were statistically analyzed with ANOVA and the post hoc Tukey test (α=.05).ResultsThe mean flexural strengths (MPa) were HP/NC=91.35 ±18.92; M/NC=143.94 ±36.79; Mlp/NC=117.06 ±13.86. Significant differences were found among groups (P<.001). Mean failure loads (N) and Weibull modulus (WM) of cantilever prosthesis strengths were for HP/C=512.66, WM=5.597; M/C=695.06, WM=4.875; Mlp/C=254.97, WM=1.797 (P<.001).ConclusionsImplant fixed interim structures milled from high-density PMMA blanks had a 35% higher flexural strength for both the standard prostheses and the cantilever prostheses than heat-processed denture base PMMA. The low-profile coping design was stronger than the heat-processed material, and the failure point was relocated from the lateral walls to the cervical margin area.     

Use of Stereolithographic Templates for Surgical and Prosthodontic Implant Planning and Placement. Part II. A Clinical Report

Eight implants were placed in the posterior part of the mandible using computer-generated stereolithographic templates. Preoperative implant simulation was done on a 3D computer model created by reformatted computerized tomography data. The surgeon and the prosthodontist positioned the simulated implants in the most favorable position addressing all concerns with regard to anatomy, biomechanics, and esthetics. The length and diameter of each implant along with the angulation/collar of abutments required for a screw-retained prosthesis were determined. Stereolithographic templates were then fabricated by incorporating the precise spatial position of the implants within the bone as previously planned during the computer simulation. The templates were fabricated to seat directly on the bone and were stable. The first template was used to complete osteotomies with a 2-mm twist drill followed by the second template for the 3-mm drill. Implants were placed and allowed to integrate for 4 months. After second-stage surgery, the definitive abutments were torqued into place followed by insertion of the definitive screw-retained prostheses. Dimensions of all implants and abutments were the same as planned during the computer simulation.     

Strength and mode of failure of single implant all-ceramic abutment restorations under static load.

The strength and mode of failure of three different designs of custom-made all-ceramic implant abutments fabricated by milling of In-Ceram sintered ceramic blocks were compared with the conventional CeraOne system under static load. Four test groups were formed with different locations of abutment screws. In three test groups, In-Ceram crowns were fabricated for placement on the all-ceramic abutments, and in one test group, a veneer porcelain was fired directly on the abutment; crowns in the control group were fabricated using the CeraOne system. Ten-mm-long Br?nemark implants were placed into a brass block that allowed loading at a 30-degree angle to the long axis. The test group in which the veneer porcelain was fired directly on the all-ceramic abutments was the weakest, and it showed fractures at a mean value of 236 N. The fracture strength of the three other test groups was dependent on the extension of the crown margin relative to the location of the screw head. The test group that had the screw on the top compressing the entire ceramic abutment showed a mean value of 422 N that was similar to the results that were achieved with the CeraOne system (427 N). The weakest link in the all-ceramic single implant restorations was the abutment screw in which the bending began at approximately 190 N.     

Comparison of the accuracy of working casts made by the direct and transfer coping procedures

STATEMENT OF PROBLEM: A working cast with dies that accurately record the prepared abutments, surrounding soft tissues, and adjacent and opposing teeth is necessary. PURPOSE: This study compared the accuracy of the direct and transfer coping methods in recording the vertical and horizontal dimensional relationship of a pair of removable dies in a working cast before and after separation from the stone base. Among the procedures used for making impressions of abutments for fixed partial dentures, the transfer coping procedure has specific advantages. In particular, where there are multiple abutments, this procedure, in which individual impressions are made of the abutments, transfer copings are made, and a transfer impression of the copings is used for seating the dies and fabrication of a dental stone base, is useful. METHODS: Two groups of working casts were fabricated from a stone master cast containing 2 ivorine teeth to simulate abutments. The first group of working casts was fabricated directly from the elastomeric impression of the abutments using a 2-pour procedure. The second group of working casts was made using the transfer coping procedure. RESULTS: When the interdie dimensions in each group were compared with that of the master cast, after separation and replacement of the dies in the stone base, the differences were less than 100 microm and similar for both the direct and transfer coping techniques. CONCLUSIONS: These findings show that either procedure is equally effective in positioning the dies in the working casts.     

An alternative method for the fabrication of customised abutments for single tooth replacements. A clinical follow-up after 18 months

The present paper describes an alternative method (The Cresco ST-method) for the fabrication of customised abutments designated for implant supported single-tooth (ST) replacements. The method is based on the conventional lost wax technology. 29 ST-replacements/crowns fabricated according to the method were tested/evaluated clinically during an 18 months period. The test was focused on mechanical complications. All crowns were supported by Cresco solid screw implants. Only one mechanical complication (retention screw loosening) was reported during the observation period. Based on the results it was concluded that the Cresco ST-method for fabrication of customised abutments is accurate and reliable. The influence of the interlocking features between implant and abutment and the advantages with customised abutments were discussed.     

Accuracy of the acrylic resin pattern for the implant-retained prosthesis.

An in vitro study was conducted to determine the accuracy of fit of the acrylic resin pattern for the implant-supported prosthesis to the implant abutments. A master model containing five Nobelpharma titanium implants was fabricated using Ivocap acrylic resin. Using this model, five standardized acrylic resin patterns were fabricated from the three test dental acrylic resins. The fabricated patterns remained on the master model for 24 hours before removal and subsequent measurement. To compute the accuracy of each pattern, three special measuring points were firmly attached to each gold cylinder prior to pattern fabrication and the x, y, and z coordinates of these measuring points were determined. Measurements were made prior to pattern fabrication, with the cylinders on their respective abutments and after pattern fabrication, when the pattern had been removed from the master model. The results of this study showed that there was a significant difference in accuracy between the test acrylic resins and that none of these materials was completely accurate.