In vitro comparison of master cast accuracy for single-tooth implant replacement

STATEMENT OF PROBLEM: The inaccuracy in transferring the position of the hexagonal head of a single implant to the working cast can result in a final single tooth crown, which clinically may present occlusal and/or interproximal contacts that are different from those contacts on the master cast obtained by the technician. PURPOSE: This in vitro study evaluated the accuracy of the master casts obtained using square pick-up impression copings for single-tooth replacement. Copings used were (1) copings as sold by the manufacturer, and (2) copings modified by sandblasting and coating with impression adhesive their roughened surfaces before final impression procedures. MATERIAL AND METHODS: A polymeric resin model with a standard single implant was used to simulate a clinical situation. A group of 20 impressions were made using nonmodified impression copings; a second group of 20 impressions were fabricated with modified copings. Master casts fabricated for both groups were analyzed to detect rotational position change of the hexagon on the implant replicas in the master casts in reference to the resin model. RESULTS: The rotational position changes of the hexagon on implant replicas were significantly less variable in the master casts obtained with the modified impression copings than in the master casts achieved with the nonprepared copings. CONCLUSION: Improved precision of the impression was achieved when the adhesive-coated copings were used.     

The single-tooth implant: a viable alternative for single-tooth replacement

BACKGROUND: The use of dental implants for single-tooth replacement cases introduces a challenge to the performance of these restorations. Clinical data suggest that single-tooth implant restorations do not benefit from lateral support from the surrounding dentition as do bridged implants, and that these restorations are subjected to greater masticatory forces. Therefore, single-tooth implants are exposed to an increased risk of failure. This prospective clinical trial was designed to evaluate the cumulative success rate of dual acid-etched single-tooth replacement implants in two clinical centers. METHODS: The study protocol included 59 patients between 19 and 73 years. Implants were evaluated for mobility, infection, and crestal bone loss from 30.9 to 60 months. RESULTS: Seventy-one (71) implants were placed in 59 patients, 20 male and 39 female. Forty-seven (47) were placed in the maxilla and 24 in the mandible. The percentages of anterior and posterior implants were 45.1% and 54.9%, respectively. A total of 13 (18.4%) implants were placed in soft, poor quality (Type IV) bone. Beginning 1 month post-implant placement, cases were followed for 30.9 to 60 months with a mean follow-up of 45.9 months. One implant failed (peri-implant infection) yielding an overall success rate of 98.6%. CONCLUSIONS: This success rate for single-tooth replacement dual acid-etched implants compares favorably with bridged implants and with success rates of other single-tooth implant studies. Dual acid-etched implants performed well even under conditions of poor quality bone, where concomitant bone augmentation was performed, and when used for immediate replacement of extracted teeth.     

Immediate implant therapy in clinical practice: single-tooth replacement

Once viewed as an esoteric treatment option, implant therapy has demonstrated long-term predictability at least equal to that of more "conventional" treatment modalities. The continued evolution of implant surface technology and restorative options has made implant therapy the treatment modality of choice in many if not most, clinical situations. It is, therefore, only natural that the role of immediate implant therapy continues to expand. Proponents of immediate implant therapy advocate its use at the time of tooth removal or, in a partially or fully edentulous arch, to meet a variety of clinical challenges.     

Computer-aided flapless implant surgery and immediate loading. A technical note

Purpose

The aim of the present technical note was to describe a prosthetic technique developed to increase the predictability of immediately loaded implants supporting a fixed prosthesis after computer-aided template-guided flapless implant placement.

Methods

During a 2-year period, eight patients presenting partial edentulism underwent computer-aided template-guided implant placement. The presented technique was used during the prosthetic procedures to directly transfer the data obtained with the facebow to the surgical environment, allowing for accurate repositioning of the temporary prosthesis on the implants as previously planned with the digital software.

Results

A total of 78 dental implants were immediately loaded with an implant-supported fixed prosthesis after flapless template-guided implant placement. A survival and success rate of 100 % was reported after a mean follow-up of 1 year from the prosthetic loading. Neither major complications nor dropouts were observed during the healing time. From both clinical and radiological evaluations, implants appeared stable with no signs of soft tissue inflammation or infection and no evidence of pathological peri-implant bone resorption.

Conclusions

The proposed technique associated with computer-aided implant placement and immediate loading protocol provided a high implant and prosthetic survival and success rate. No complications were reported during the recalls, suggesting predictability and reliability of the present technique over a short-term period.

     

A screw lock for single-tooth implant superstructures.

BACKGROUND: The most common complication in a single-tooth implant restoration is abutment screw loosening. Instability of the prosthetic superstructure is expressed by difficulty in chewing and functioning, as well as soft-tissue soreness and/or swelling that could lead to screw fracture. Manufacturers of oral implants have attempted to refine the connecting parts of the prosthesis to achieve a more predictable tightening method for the screws. METHODS: To maintain the abutment screw tightly in its correct position, the authors developed a technique in which an elongated hexagonal titanium bar is inserted into the hexed fixed screw head. The screw is locked, and the bar is then fixed with a light-cured composite resin material that serves to seal the retaining screw access hole. The occlusal hexagonal bar thus serves as a secure screw lock that can be easily removed if needed. RESULTS: The authors have used the hexagonal bar for almost three years on 120 single-tooth screw-retained prostheses in 100 patients (65 in the first and second premolar region, 40 in the incisor region and 15 in the posterior molar region). All of these prostheses functioned successfully, including those with wider occlusal planes and increasing occlusal forces. No screw loosening or fractures were noted in any of the fixtures. CLINICAL IMPLICATIONS: This technique secures and stabilizes the single-tooth prosthesis, reduces chair time on follow-up procedures and reduces unnecessary frustration in patients and dental team members.     

The Graz implant supported pendulum, a technical note.

A new, immediately loadable palatal implant with rotational stability and an implant-supported pendulum for patients with dental class II dysgnathia and dental crowding is presented. In seven cases, the treatment goal of distalization of all upper molars without extraction of a single tooth was achieved within 8 months.     

Template fabrication for a midpalatal orthodontic implant: technical note

An implant has been developed as an adjunct to conventional orthodontic anchorage. Planning is advisable to determine the available bone and soft tissue thickness and the optimum position for orthodontic utilization. A simple method is described for fabrication of a radiographic and surgical template to aid in optimal placement of the implant.     

Effect of impression coping and implant angulation on the accuracy of implant impressions: an in vitro study

PURPOSE

The purpose of this study was to compare the accuracy of the implant master cast according to the type (pick-up, transfer) and the length (long, short) of the impression copings.

MATERIALS AND METHODS

The metal master cast was fabricated with three internal connection type implant analogs (Osstem GS III analog), embedded parallel and with 10° of mesial angulation to the center analog. Four types of impression coping were prepared with different combinations of types (transfer, pick-up) and lengths (long, short) of the coping. The impressions were made using vinyl polysiloxane (one step, heavy + light body) with an individual tray, and 10 impressions were made for each group. Eventually, 40 experimental casts were produced. Then, the difference in the distance between the master cast and the experimental cast were measured, and the error rate was determined. The analysis of variance was performed using the SPSS (v 12.0) program (α = .05), and the statistical significance was set at P < .05.

RESULTS

The ANOVA showed that the pick-up type impression coping exhibited a significantly lower error rate than the transfer type. However, no significant difference was observed with respect to the length of the impression coping. Additionally, no significant difference was observed between the parallel and mesial angulated groups.

CONCLUSION

Within the limitations of this study, the pick-up type impression coping exhibited a more accurate implant master cast than the transfer type in parallel group. The accuracy of the implant master cast did not differ for different lengths of impression coping of at least 11 mm. Additionally, the accuracy of the implant cast was not different for the parallel and 10° mesial angulated groups.     

Ideal implant positioning in an anterior maxillary extraction socket by creating an apico-palatal guiding slot: a technical note

In anterior maxillary extraction sockets, immediate implants are usually positioned along the palatal slope of the extraction socket. However, this positioning frequently causes unintentional slipping of dental implant toward thin labial plate, leading to its fracture or perforation. To prevent this, the present authors have created a simple apico-palatal guiding slot in the extraction socket following atraumatic extraction. Guided by this slot, sequential drilling up to implant placement can be easily accomplished while maintaining ideal axial orientation of the dental implant.     

Fit of implant frameworks: an in vitro comparison between two fabrication techniques

STATEMENT OF PROBLEM: It has been suggested that a precise fit between the implant and the framework cylinder is necessary to ensure a satisfactory long-term clinical outcome. PURPOSE: The purpose of this study was to compare the precision of fit between implant abutments and framework cylinders in frameworks fabricated by the Procera system and those fabricated from cast gold-alloy. MATERIAL AND METHODS: A total of 19 frameworks, 14 made with the Procera system (type 1) and 5 made of a cast gold-alloy (type 2), were fabricated. A total of 95 implants, 70 type 1 and 25 type 2 frameworks, were evaluated. Three replicas of the space between the implant abutments and the framework cylinders of the master cast were made for each test specimen. The replicas were cut with a scalpel in 2 axial directions: buccal-lingual and right-left. For the purpose of measurement, a microscope with a precision of +/- 0.5 microm was used at original magnification x30. The Student t test was used to determine whether there were significant differences between the framework designs. RESULTS: The buccal-lingual measurements for the type 1 and type 2 frameworks showed mean values of 28.1 microm (SD 9.8) and 42.0 microm (SD 1.8) on the buccal side, respectively, and 25.6 microm (SD 11.2) and 51.6 microm (SD 10.9) on the lingual side, respectively. For the right-left view, the mean measurements were 26.6 microm (SD 8.4) and 49.2 microm (SD 11.4) on the right side, respectively, and 27.4 microm (SD 8.5) and 44.4 microm (SD 6.5) on the left side, respectively. The total mean value for type 1 frameworks was 26.9 microm (SD 9.3); that for type 2 frameworks was 46.8 microm (SD 8.8). CONCLUSION: Within the limitations of this experiment, it was demonstrated that the fit of frameworks made with the Procera system was significantly better than that of the frameworks made with cast gold-alloy (P<.01).     

Bone reduction surgical guide for the Novum implant procedure: technical note

The Novum System offers a unique opportunity to create a definitive, immediately loaded fixed prosthesis on the edentulous mandible for patients who meet specific presurgical criteria. Since this system is based on precisely placed implants and prefabricated bar structures, the surgical techniques are critical in obtaining a satisfactory result. It is especially important that the bone reduction required to create space for the implants and bar assembly be in the proper plane and deep enough to leave room for eventually setting and processing teeth. The surgical guide described here can be an important adjunct during bone reduction to assure proper spatial positioning of the preformed titanium bars. Mounted casts of the correct or corrected maxillary dentition and mandibular arch are required at the appropriate vertical dimension of occlusion. The mandibular cast is reduced in prescribed dimensions to allow the subsequent creation of a processed resin surgical guide for use during the initial stages of surgery. This guide, when used for bone reduction during surgery, eliminates the arbitrary removal of osseous structure and helps assure the plane of implant placement is appropriate for each patient. When used routinely, a significant complication of the Novum procedure can be minimized or eliminated completely. Setting of teeth and processing are subsequently simplified, especially in the posterior dimensions, with this guide technique.     

Effect of subgingival depth of implant placement on the dimensional accuracy of the implant impression: an in vitro study

STATEMENT OF PROBLEM: In some instances, an implant needs to be placed deep subgingivally, which may result in a less accurate impression of the implant. PURPOSE.: The purpose of this study was to evaluate the effect of subgingival depth of implant placement on the accuracy of implant impressions. MATERIAL AND METHODS: A stone master model was fabricated with 5 implant analogs (RN synOcta analog), embedded parallel to each other, at the center (E) and the 4 corners (A, B, C, and D). The vertical position of the shoulders of the implants was intentionally different among the implants: A and E were flush with the top surface of the model; B was 2 mm below, and C and D were 4 mm below the surface. The horizontal distances of implants A, B, C, and D from E were measured with a measuring microscope. A cross-shaped metal measuring bar was then fabricated and connected to E, with the arms of the casting designed to be 2 mm above the top surface of the model and incorporating a reference mark. With the measuring bar connected to E, the vertical distances from the apical surface of A, B, C, and D to the measuring reference marks were measured with a digital micrometer. The body of the impression coping for implant D was modified by adding 4 mm of additional impression coping, while standard impression copings were used for all other implants. Open tray impressions were made using medium-body polyether material (Impregum Penta) or a combination of putty and light-body vinyl polysiloxane (VPS) material (Elite HD+) (n=15). Then casts were poured with type IV dental stone. The vertical and horizontal distances of the casts were measured with the methods outlined above for the master model. The distortion values that were determined as differences between the measurements of the master model and those of the casts were collected for statistical analysis. Two-way and 1-way repeated measures ANOVA followed by Tukey's HSD test were performed to compare the distortion values (alpha=.05). RESULTS: For vertical measurements, 2-way repeated measures ANOVA showed no significant depth (P=.36), material (P=.24), or interaction effects (P=.06). However, it showed significant depth effect for horizontal measurements (P=.01). Within the polyether group, 1-way repeated measures ANOVA showed significant differences in horizontal measurements among the implants with different depths (P=.03). The post hoc Tukey's test showed that the impression of 4-mm-deep implants with normal impression copings (C) was significantly less accurate than impressions of 0-mm-deep implants (A) (P=.02). Within the VPS group, there was no significant difference among the implants with different depths (P=.09). CONCLUSIONS: There was no effect of implant depth on the accuracy of the VPS group. However, for the polyether group, the impression of an implant placed 4 mm subgingivally showed a greater horizontal distortion compared to an implant placed more coronally. Adding a 4-mm extension to the retentive part of the impression coping eliminated this difference.     

Fracture resistance of single-tooth implant-supported all-ceramic restorations: an in vitro study

STATEMENT OF PROBLEM: High-strength ceramic materials can be used to fabricate esthetic and stable implant-supported single-tooth restorations. No study was identified that compared the fracture resistance of individual components of single-tooth implant-supported all-ceramic restorative systems after artificial aging. PURPOSE: The purpose of this in vitro study was to evaluate the fracture resistance of single-tooth implant-supported all-ceramic restorations consisting of alumina all-ceramic restorations on different implant abutments and to identify the weakest component of the restorative system. MATERIAL AND METHODS: Forty-eight standardized maxillary central incisor alumina crowns (Procera) were fabricated for each of the 3 test groups (n = 16) (Control group Ti, titanium abutments; Group Al, alumina abutments; Group Zr, zirconia abutments) for the Replace implant system. The crowns were adhesively luted using a resin luting agent (Panavia 21) and artificially aged through dynamic loading and thermal cycling. Afterwards, all specimens were tested for fracture resistance using compressive load on the palatal surfaces of the crowns. Kruskal-Wallis analysis of variance and post hoc Wilcoxon rank sum tests were performed to test for differences in fracture resistance values (alpha = .05). RESULTS: All test specimens survived the artificial aging process using simulated oral conditions. No screw loosening was recorded. The median fracture resistance was 1454 N, 422.5 N, and 443.6 N for groups Ti, Al, and Zr, respectively. Significant differences were found for the fracture resistance comparisons of group Ti with groups Al and Zr (Kruskal-Wallis test, P < .001). The test results for the comparison of groups Al and Zr were not significant. CONCLUSION: All 3 implant-supported restorations have the potential to withstand physiologic occlusal forces applied in the anterior region.     

A laboratory investigation of the accuracy of the repositioning impression coping technique at the implant level for single-tooth implants

This study investigated the accuracy of the repositioning impression technique at the implant level using vinyl polysiloxane impression material. Three groups each of ten senior dentists, postgraduate students and technicians were asked to use this technique to record the position of an implant in a master model. The Reflex Microscope was used to measure variations between the resulting casts and the master model. Significant difference between the casts and the master model in the X and Y-axes (p < 0.01) was recorded. Alarming inclinational and rotational errors for the implant analogue position were measured with all groups of operators. Similar distortion in the Z-axis was recorded.