Browsing by Subject "Prosthodontics"

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    A Comparison Of Morse Taper And Sloped Shoulder Abutment Geometries Using Torque Angle Analysis
    (2024) Clark , Zane
    Abstract Background: Full arch fixed implant prostheses continue to become a popular treatment option for dentists when rehabilitating the completely edentulous patient as they can help to significantly restore function, esthetics and comfort paired with the well-documented predictability, success and longevity of dental implants. The connection of the prosthesis to the implant platform has also received much attention in the literature, however, many of these papers only report torque and de-torque values. Generally, torque values recommended by the manufacture are between 65-75% of that abutment screws yield potential, or in other words, the point at which the abutment screw will fracture. But a key concept to understand is that the implant-abutment connection maintains its stability through a mechanical force known as preload, which is a clamping force created from the elastic recovery of the abutment screw. But herein lies a well-documented issue that up to 90% of the torquing force applied to the abutment screw is lost to friction and other factors leaving only 10% available for conversion to preload. Although it has been reported that abutment geometry can aid in the stability of the connection, preload is the predominant force holding the implant, abutment and prosthesis together. If the preload can be maximized within the limits of the abutment screws yield potential, then a stronger implant abutment connection will be created. In a pilot study by Chow et al., they investigated whether abutment geometry contributes to preload of the abutment screw. Among their conclusions was a statistically significant difference between classical morse tapered engaging abutments and non-engaging abutments with the non-engaging abutments having higher preload values. This was because for the non-engaging abutments, much of the torque was lost to settling of the abutment into the morse taper. With the numerous dental implant companies a restorative dentist can choose from, it begs the question: are all implant-abutment connections created equal? More specifically, are some implant brands better suited for optimizing the implant-abutment connection and preload achieved in the abutment screw. Therefore, the purpose of this study is to investigate the effect of abutment geometry on preload with two widely used implant bodies and multiunit abutments. The hope of this pilot study is to report the data and utilize it for a larger future study that compares preload data between multiple implant brands. Purpose: This study aimed to evaluate preload on sloped shoulder and morse taper abutment geometries using torque angle signature analysis Materials and Methods: Three sloped shoulder (Straumann, BLX) implants were embedded into custom dies using Type V dental gypsum (Die-Keen Green). Two abutment designs were selected for this study, one having a morse taper geometry and the other with a morse taper and sloped shoulder component. Three morse tapered internal connection abutments and three sloped shoulder abutments were used in this study. An a priori power analysis was completed to determine sample size. Therefore, two experimental groups (n=3) were created. A custom fabricated device was milled out of aluminum to rigidly fixate both the imbedded implant and torque meter. A horizontal arm was also attached to the torque meter to allow for a consistent and controlled torque force to be applied. A torque driver was attached to the torque angle meter (HGTA-AMK Digital Torque Gauge with Angle Encoder, IMADA, PCB, Load &Torque, Inc.). Each abutment was torque to into the imbedded implants to 35 Ncm and a torque angle signature obtained. Upon reaching 35 Ncm, the torque meter was zeroed and samples were de-torqued producing a releasing curve. Analysis of the torque angle signatures allowed for extraction of insertion slope as well as insertion and releasing degree of rotation (torque angle). From these values, preload values were calculated using the preload formula outlined by Hagiwara and Ohashi (1994). Statistical analysis was conducted using non-paired student t-test. A p-value of 0.05 was used. Results: Morse Taper Abutments (blue) show an elongated rundown, alignment and elastic zone when compared to the sloped shoulder abutments. A mean insertion slope of 0.71 was calculated for sloped shoulder abutments (n=3, st. dev.= 0.102) with a 95% C.I. of ±0.115. A mean slope of 0.3 was calculated for morse taper abutments (n=3, st. dev.= 0.048) with a 95% C.I. of ±0.246. Non-paired student t-test produced a value of p=0.0039961. Analysis of the data shows a maximum mean insertion angle of 41.40° for sloped shoulder abutments (n=3, st. dev.= 3.176) and a 95% C.I. of ±3.59. Mean insertion angle for morse tapered abutments were 108.67° (n=3, st. dev. = 16.88) with a 95% C.I. of ±19.1. Non-paired student t-test produced a value of p=0.0105222. Similarly, upon releasing, releasing angles showed a maximum mean release angle of 31.6° for sloped shoulder abutments (n=3, st. dev. = 4.757) with a 95% C.I. of ±5.38°. Mean release angle for morse tapered abutments was 21.8° (n=3, st. dev. = 1.892) with a 95% C.I. of ± 2.14°. Non-paired student t-test produced a value of p=0.0222863. The mean preload for sloped shoulder abutments was 805.06N (n=3, st. dev. = 120.812) with a 95% C.I. of ±136.7. Mean preload for morse tapered abutments was 554.48N (n=3, st. dev. = 48.074) with a 95% C.I. of ±54.39. Non-paired student t-test produced a value of p=0.0.0222289. Conclusions: Higher preload levels were found in the sloped shoulder abutment than in the morse taper abutment. Longer rundown and alignment zones were found in the morse taper abutment than in the sloped shoulder abutment. The insertion slopes were less for the morse tapered abutment than for the non-engaging abutment. Additionally, insertion angles were greater and release angles shorter in morse tapered abutments. The lack of a positive stop and greater friction between components seen in the morse tapered abutment caused the torque limit to be reached before greater clamping force could be achieved. Although more studies are needed to take friction into account, this study demonstrates that the geometry of the implant-abutment connection does influence preload. With respect to multiple implant splinted prostheses, these factors can greatly impact the clinical outcome, longevity of the prosthesis, its various components, and underlying implants.
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    Proximal bone levels of plateau-designed, press fit implants adjacent to a natural teeth and implants.
    (2009-12) Imeri, Alfredo Montes
    STATEMENT OF PROBLEM. Successful implant treatment requires a favorable biological response of living tissues to a foreign material. Even with a favorable pre-surgical evaluation, negative changes such as crestal bone loss can occur after the implant is placed, which can result in an esthetic failure. Controlling crestal bone loss around an implant placed adjacent to a natural tooth or to another implant represents an important challenge for present day prosthodontics. Guidelines on the distance between an implant and a natural tooth or another implant have been published as being an important factor in proximal bone preservation. PURPOSE. The purpose of this study was to retrospectively evaluate pre-treatment and post-treatment proximal bone levels of a single tooth, plateau-designed, press fit implants (Bicon®) utilizing a locking tapered, implant to abutment connection adjacent to a natural teeth and to a plateau design Bicon® implants. The bone levels were evaluated separately for those implants that were closer to a natural tooth or to another implant than the recommended guidelines. Bone levels were also measured on mesial and distal surfaces of all implants as well as the crestal bone levels between 2 implants. The relationship between implant spacing and crestal bone levels was to be determined. MATERIAL AND METHODS. A retrospective cohort study was designed to evaluate pre-treatment and post-treatment proximal bone levels of a single tooth, plateau-designed, press fit implants (Bicon®) utilizing a locking tapered, implant to abutment connection adjacent to a natural teeth and to a plateau design Bicon® implants. The cohort was derived from patients who received 1 or more single tooth, plateau-designed, press fit implants between 1995 and 2005. One hundred and sixty-nine implants with 338 proximal surfaces were included in this study. Of the 338 proximal surfaces, 120 were adjacent to a natural tooth, 192 were adjacent to an implant, and the remaining 26 surfaces were adjacent to an edentulous area. The mean follow-up time was 4 ± 2.3 years. Bone levels and changes in bone levels over time were determined by direct measurement of non-standardized digital periapical radiographs. All measurements were made by using a software measuring tool (DIGORA; Soredex, Tuusula, Finland) at ×3.0 magnification. Student T-tests were used to evaluate the statistical significance between pre-treatment and post-treatment proximal bone levels of natural teeth adjacent to implants. Level of significance was set to alpha 0.05. Descriptive statistics were used to report bone levels on implants adjacent to a natural tooth, another implant, or an edentulous area, as well as the crestal bone levels between 2 implants. RESULTS. There was no significant difference (P=0.25) between pre-treatment proximal bone levels and post-treatment proximal bone levels on a single tooth, plateau-designed, press fit implants (Bicon®) utilizing a locking tapered, implant to abutment connection adjacent to a natural teeth and plateau design Bicon® implants. CONCLUSIONS. Bone levels on implant surfaces adjacent to another implant and bone levels on natural teeth adjacent to implants can be expected to remain unchanged post-treatment when a single tooth, plateau-designed, press fit implant is placed closer than the recommended distance away from the natural tooth or to another implant.