Institut Straumann Research Articles

Comparison of two different restoration materials and two different implant designs of implant-supported fixed cantilevered prostheses: A 3D finite element analysis

Abstract Purpose: A key factor for the success or failure of a dental implant is the manner of stresses transferred to the surrounding bone. Parallel to this situation, cantilever extensions where it is not possible to place another implant, would cause greater stress and it should be avoided if possible. Manufacturers and clinicians try to develop new implant designs and superstructure materials to reduce the stresses around the implant and supporting bone tissue. This study analyzed the influence of superstructure materials and implant designs on stress distribution around dental implants supporting cantilever restoration under loading conditions. Materials and Methods: Three-dimensional finite element models of a 3-unit cantilever bridge were subjected to 150 N occlusal load to evaluate two different superstructure materials (conventional metal ceramic, fiber reinforced composite) and two different implant designs, cylinder type (Institut Straumann AG, Waldenburg, Switzerland) and cylinder type with micro threads around implant neck (Astra Tech AB, Mölndal, Sweden). To evaluate the distribution of stresses within the bone surrounding the implants, 3-dimensional finite element analysis was conducted using four mathematical models of unilateral 3-unit cantilever fixed partial dentures supported by two implants. Results: The stress distribution patterns and stress values were similar and stress concentrations were similar in both restoration materials. The highest stress concentrations were around the adjacent ITI implant, which supports the conventional metal porcelain restoration. Conclusions: Although, there was no significant difference in stress distribution between fiber reinforced composite (FRC) and conventional metal porcelain, stress values were lower in FRC restorations. The Astra-Tech micro-thread design reduced the stress that was distributed throughout the implant body, but it should be noted that the peak stress was still present on the implant neck.

Retrospective Analysis of Prosthetic Complications of Implant-Supported Fixed Partial Dentures After an Observation Period of 5 to 10 Years

The purpose of this study was to evaluate the incidence of the most common technical problems with implant-supported fixed partial dentures (FPDs) and to assess the survival and success rates (event-free survival) after 5 to 10 years of function. All of the implants evaluated in this study were from a single manufacturer (Institut Straumann). Follow-up examinations were scheduled 1 week after suprastructure placement, 6 months later, and annually thereafter. Prosthesis-based data on survival/failure rates and technical complications were analyzed. In 95 partially edentulous patients, 231 Straumann implants were placed and restored with 177 implant-supported prostheses (125 single crowns, 18 splinted crowns on two adjacent implants, and 34 three-unit FPDs). One hundred thirty one solid abutments and 100 synOcta abutments were inserted. The survival rate of prostheses supported by implants was 97.7%. The prosthetic success rate (event-free survival) was 96.05%. After an observation period of 5 years, the cumulative incidence of screw loosening was 0%. Fracture of the veneering porcelain occurred in 3.95% of all restorations. Fractures of the superstructure framework were not observed. The overall incidence of complications after 5 years was highest for splinted crowns, which showed the lowest success rate (94.4%), followed by three-unit FPDs (96%) and single crowns (98.4%). Single-unit restorations or short-span FPDs supported by both synOcta and solid abutments on Straumann implants showed low rates of technical complications, the most common being fracture of the veneering porcelain.

A new restorative technique for the perishing implant due to abutment screw fracture.

Dental implantology has revolutionized the treatment for edentulous and partially edentulous patients. With proper treatment planning, appropriate placement, adequate prosthetic design, and proper maintenance, implants can achieve a success rate of 97% to 99%.1 However, despite high survival rates, biological and technical failures or complications may occur.2 Technical problems can be divided into 2 groups: those related to the implant components, and those related to the prosthesis. Technical problems related to implant components include abutment screw loosening and fractures, and both have high incidence rates.3 Once an abutment screw fracture has occurred, the fractured screw segment inside the implant has to be removed. However, during this procedure, damage to the internal threads of the implant may happen. As a result, the implant may remain osseointegrated but will lose its ability to retain the prosthesis. To overcome this problem, a technique to remove the fractured screw and restore the tooth without sacrificing the implant is suggested. This article presents a technique of converting the screw chamber into post space and replacing the prosthetic component over this custom-made post and core system.A significant reason for screw fracture is screw loosening, and undetected micromovements of the abutment under functional loading, which may occur as a result of bruxism, an unfavorable superstructure, overloading, or malfunction.4 Several methods of addressing a fractured abutment screw have been described. Two common approaches for removing a fractured or damaged abutment screw are: (1) the use of a self-made screwdriver or (2) the use of a service set available for the specific implant system (ITI Dental Implant System, Institut Straumann AG, Waldenburg, Switzerland, Nobel Biocare USA, Yorba Linda, Calif).5 However, there is always the possibility of damage to the threads with the use of these techniques. Though the manufacturer purports that the new abutment will fit after tapping the threads, the new abutment may be slightly rotated and may not fit.6 However, the method is complex and difficult for routine application because the procedure can be time-consuming and involves the risk of damaging the threads inside the implant.Prevention is better than a cure, and the correct measures should be taken to ensure that screw loosening and fracture does not happen. However, when these problems occur, the first approach should be a conservative retrieval of the fractured screw without damaging the threads. If conservative retrieval fails, then the technique explained in this article should be employed without sacrificing the osseointegrated implant. Even the proposed technique has a few disadvantages such as weakening of the implant body and excessive heat production during cutting of the fractured screw. Further long-term clinical trials are required to confirm its success in the long run.

Evaluation of a New Titanium‐Zirconium Dental Implant: A Biomechanical and Histological Comparative Study in the Mini Pig

Titanium zirconium alloy with 13-17% zirconium (TiZr1317) shows significantly better mechanical attributes than pure Ti with respect to elongation and fatigue strength. This material may be suitable for thin implants and implant components exposed to high mechanical constraints. The aim of this study was to test the hypothesis that TiZr1317 and Ti implants show comparable osseointegration and stability. The mandibular premolars (P1, P2, P3) and the first molar (M1) in 12 adult miniature pigs were extracted 3 months prior to the study. Six specially designed implants made from Ti (commercially pure, Grade 4) or TiZr1317 (Roxolid®, Institut Straumann AG, Basel, Switzerland) with a hydrophilic sandblasted and acid-etched (SLActive, Institut Straumann AG, Basel, Switzerland) surface were placed in each mandible; three standard implants modified for evaluation of removal torque (RT) in one side and three bone-chamber implants for histologic observations in the contralateral side. RT tests were performed after 4 weeks when also the bone chamber implants and surrounding tissue were biopsied for histologic analyses in ground sections. The RT results indicated significantly higher stability (p=0.013) for TiZr1317 (230.9±22.4Ncm) than for Ti implants (204.7±24.0Ncm). The histology showed similar osteoconductive properties for both implant types. Histomorphometric measurements showed a statistically significant higher (p=0.023) bone area within the chamber for the TiZr1317 implants (45.5±13.2%) than did the Ti implants (40.2±15.2%). No difference was observed concerning the bone to implant contact between the groups with 72.3±20.5% for Ti and 70.2±17.3% for TiZr1317 implants. It is concluded that the TiZr1317 implant with a hydrophilic sandblasted and acid-etched surface showed similar or even stronger bone tissue responses than the Ti control implant.

Quantitative analysis on orientation of human bone integrated with midpalatal implant by micro X-ray diffractometer

A midpalatal implant system has been used as the unmoved anchorage for teeth movement. An 18-year-old male patient presented with reversed occlusion and was diagnosed as malocclusion. A pure titanium fixture (lengths: 4mm, diameter: 3.3mm, Orthosystem®, Institute Straumann, Switzerland) was implanted into the palatal bone of the patient as the orthodontic anchorage. The implant anchorage was connected with the upper left and right first molars, and had been used for 3 years. After dynamic treatments, the titanium fixture connected with bone was removed surgically, fixed in formalin solution, and embedded in resin. Specimens were cut along the frontal section of face and the direction of longitudinal axis of the implant, stained, and observed histologically. The titanium fixture was integrated directly with compact bone showing cortical bone-like structure such as lamella and osteon. In addition, to qualitatively characterize the implant-supported human bone, the crystallinity and orientation of hydroxyapatite (HAp) phase were evaluated by the microbeam X-ray diffraction analysis. Preferential alignment of c-axis of HAp crystals was represented by the relative intensity ratio of (002)-face diffraction peak to (310)-face one. The values decreased monotonously along the direction of the lateral stress from the site near the implant thread to the distant site in all horizontal lines of the map. These results indicated that the X-ray images for the intensity of c-face in HAp revealed functionally graded distribution of cortical bone quality. The micro-scale measurements of HAp structure could be a useful method for evaluating the mechanical stress distribution in human hard tissues.

In Vitro Assessment of Primary Stability of Straumann® Implant Designs

Primary implant stability (PS) is one of the main factors influencing implant survival rate. Several methods to determine the PS have been used, such as Periotest values (PVs) and resonance frequency analysis (RFA) with implant stability quotient (ISQ) values. The aim of this study was to compare different implant designs in regard to PS assessed by Periotest and RFA in vitro. A total of 90 implants were placed in freshly slaughtered cow ribs. The implants (Straumann®, Institute Straumann AG, Basel, Switzerland; length 10 mm, ø3.3 mm) had the following three designs: Bone Level (BL, 30 implants), Standard Plus (SP, 30 implants), and Tapered Effect (TE, 30 implants). Before implant placement, the investigator was calibrated for every design according to the manufacturer's instructions. An independent observer, blinded to the study, assessed the accuracy of placement. RFA based on the Osstell device and PVs were performed after abutment connection. One-way analysis of variance and Tukey's post hoc test were used for statistical evaluation. All implants were mechanically stable. The mean PV for BL was -4.67(± 1.18), for SP, -6.07(± 0.94), and for TE, -6.57(± 0.57). The mean ISQ values were 75.02(± 3.65), 75.98(± 3.00), and 79.83(± 1.85), respectively. The one-way ANOVA showed significant difference among three implant designs in PV (p < .0001) and for the ISQ between BL/TE or SP/TE implants (p < .0001). In addition, the Tukey's (pair-wise comparison) test showed significant differences in PV and RFA between the BL/T (p < .0001). Within the limitations of this study, higher implant stability was found for tapered designed implants.

Differential Effect of Amelogenin Peptides on Osteogenic DifferentiationIn Vitro: Identification of Possible New Drugs for Bone Repair and Regeneration

Enamel matrix proteins (EMP) have been shown to promote regeneration of periodontal ligament and root cementum, and sometimes to enhance the differentiation of bone-forming cells in vitro and new bone growth in vivo. However, the inconsistent and unpredictable effects of EMP that have been reported for bone regeneration may be due to the highly variable composition of this heterogeneous material, which is comprised mainly of amelogenin and amelogenin-derived peptides. The present study has therefore examined the effects of naturally occurring low-molecular-weight (LMW) and high-molecular-weight (HMW) fractions of Emdogain(®) (EMD; Institut Straumann, Basel, Switzerland), a commercially available form of EMP, on osteogenic differentiation of bone precursor cells in vitro. In addition, the effects of chemically synthesized specific components of LMW and HMW-namely, the tyrosine-rich amelogenin peptide (TRAP), a specific amelogenin isoform derived by proteolytic clipping, and a leucine-rich amelogenin peptide (LRAP), an isoform derived by alternative splicing-on bone-forming cell activity were also investigated. Our findings demonstrate that while TRAP suppressed the formation of bone-like mineralized nodules, LRAP upregulated osteogenic differentiation. Furthermore, synthetically produced TRAP and its unique C-terminal 12 amino acid sequence (TCT) also suppressed bone-forming cells, whereas LRAP and its unique C-terminal 23 amino acid sequence (LCT) markedly enhanced terminal differentiation of bone-forming cells. These findings suggest that the differential effects of amelogenin-derived peptide sequences present in EMP could be of potential clinical value, with the novel bioactive TCT peptide as a useful tool for limiting pathological bone cell growth and the unique LCT sequence having therapeutic benefits in the treatment of periodontal and orthopedic diseases.

ORIGINAL ARTICLE - Analysis of RFA related to stabilities by types and areas of dental implants

Objective : This research compared stabilities between two types of dental implant (SLATM, Institut Straumann AG, Waldenburg, Switzerland and SSIITM, Osstem co, Busan, Korea) using Osstell Mentor (Integration Diagnostics AB, Goteborg, Sweden) considering surgery methods, surgery area, diameter of implant, systemic disease, and smoking for obtaining prognosis information when installing fixture of dental implant. Materials &amp; Methods : 206 implants of 131 patients taken by resonance frequency analysis (RFA) were determined as a final sample. Dental implants were installed as protocol of supplier by a excellent dentist who had 10 years experience about dental implants. Before connecting abutments (3 months after installation of fixture), RFA were measured twice for buccal and lingual direction to obtain average value. Results : Dental implants at mandible showed significantly higher stabilities significantly than at maxilla (p&lt;0.001). Diameter 4.8 implants had also higher stabilities than diameter 4.1 in case of SLATM implants (p&lt;0.001). SLATM implants showed more excellent stabilities than SSIITM implants, especially at posterior area of mandible (p=0.045) and premolar area of maxilla (p=0.032). Conclusions : This research revealed higher stabilities of SLATM implants than SSIITM implant, especially at posterior area of mandible (p=0.045) and premolar area of maxilla (p=0.032).

Randomized Controlled Trial to Compare Two Bone Substitutes in the Treatment of Bony Dehiscences

This in vivo split-mouth randomized controlled trial compared a synthetic bone substitute with a bovine bone mineral to cover bone dehiscences after implant insertion. Fourteen patients received four to six implants to support an overdenture. Two comparable dehiscences within the same patient were first covered with a layer of autogenous bone, followed by a layer of either Bio-Oss® (group 1; Geistlich Pharma AG, Wolhusen, Switzerland) or Straumann BoneCeramic® (group 2; Institut Straumann AG, Basel, Switzerland) and sealed by a resorbable membrane. The change in vertical dimension of the defect was measured at implant placement and at abutment connection (6.5 months). Clinical and radiological parameters were evaluated up to 1 year of loading. The vertical size of the defect at surgery was 6.4 ± 1.6 mm for group 1 and 6.4 ± 2.2 mm for group 2 sites, measured from the implant shoulder. After 6.5 months, the depth of the defect was reduced to 1.5 ± 1.2 mm and 1.9 ± 1.2 mm for group 1 and group 2 sites, respectively (p > 0.05). No implants failed during follow-up. Mean marginal bone loss over the SLActive surface was 0.94 mm (group 1), 0.81 mm (group 2), and 0.93 mm (group 3, no dehiscence) after 1 year of loading. Both bone substitutes behaved equally effectively.

Evaluation of Primary Stability of Self‐Tapping and Non‐Self‐Tapping Dental Implants. A 12‐Week Clinical Study

The aim of this study was to investigate the relationship between surgical techniques and implant macro-design (self-tapping/non-self-tapping) for the optimization of implant stability in the low-density bone present in the posterior maxilla using resonance frequency analysis (RFA). A total of 102 implants were studied. Fifty-six self-tapping BlueSkyBredent® (Bredent GmbH&Co.Kg®, Senden, Germany) and 56 non-self-tapping Standard Plus Straumann® (Institut Straumann AG®, Waldenburg, Switzerland) were placed in the posterior segment of the maxilla. Implants of both types were placed in sites prepared with either lateral bone-condensing or with bone-drilling techniques. Implant stability measurements were performed using RFA immediately after implant placement and weekly during a 12-week follow-up period. Both types of implants placed after bone condensing achieved significantly higher stability immediately after surgery, as well as during the entire 12-week observation period compared with those placed following bone drilling. After bone condensation, there were no significant differences in primary stability or in implant stability after the first week between both implant types. From 2 to 12 postoperative weeks, significantly higher stability was shown by self-tapping implants. After bone drilling, self-tapping implants achieved significantly higher stability than non-self-tapping implants during the entire follow-up period. The outcomes of the present study indicate that bone drilling is not an effective technique for improving implant stability and, following this technique, the use of self-tapping implants is highly recommended. Implant stability optimization in the soft bone can be achieved by lateral bone-condensing technique, regardless of implant macro-design.

Immediate and Early Loading of Chemically Modified Implants in Posterior Jaws: 3‐Year Results from a Prospective Randomized Multicenter Study

There is a lack of well-designed prospective, randomized clinical trials evaluating the efficacy of immediate and early loading of implants placed in the partially edentulous posterior maxilla or mandible. The aim of this study was to evaluate crestal bone level changes over 3 years following immediate or early loading of Straumann implants with a chemically modified surface (SLActive®, Institut Straumann AG, Basel, Switzerland) placed in the posterior maxilla and mandible. Subjects received temporary restorations immediately or 28 to 34 days after surgery, with permanent restorations placed at 20 to 23 weeks. Bone level changes were measured by comparison of standardized radiographs taken on the day of implant placement and 5, 12, 24, and 36 months thereafter. Two hundred thirty-nine of two hundred sixty-six patients (89.9%) completed the trial. Implant survival rates were 97.4% and 96.7% in the immediate and early loading groups, respectively (p = not significant). Over 36 months, the mean bone level change for immediately loaded implants was 0.88 ± 0.81 mm versus 0.57 ± 0.83 mm for the early-loaded group (p < .001). After adjusting for a slight difference in initial placement depth, the time of loading had no significant influence on bone level change. Changes in crestal bone level occurred mostly during the first 5 months postloading. After this bone remodeling period, crestal bone level was stable up to 36 months. Implants with a chemically modified surface are safe and predictable for immediate and early loading in the posterior maxilla and mandible.

An Open System Approach for Surgical Guide Production

Surgical guides for oral implantology were made with a new open system independent of implant planning software based on a universal computed tomography/cone beam computed tomography (CBCT) scan plate for fiducial markers. For this in vitro study, CBCT scans were taken of 18 models based on a universal computed tomography/CBCT scan plate (Bego Medical, Bremen, Germany) for fiducial markers. The models were made from radiopaque composite with several integrated radiopaque gutta-percha points used as a reference. The coDiagnostiX (Institut Straumann, Basel, Switzerland) and implant 3D (med3D, Heidelberg, Germany) software programs were used for virtual implant planning. Coupling devices on the scan plate allowed for the precise connection to a special transfer plate (Bego Medical), which transfers the implant position to the drill guide. The horizontal distance of the final implant position to the gutta-percha markers was compared with the implant planning values. Planning of 18 implants was performed with the Institut Straumann system and 18 with the med3D system. The horizontal deviation of the final implant placement compared with the implant planning made with the med3D system showed a mean error of 0.33 mm for implants 1 and 2. The difference between the CBCT measurements of the Institut Straumann models was larger than that of the med3D measurements. The mean error for implant 1 was 0.65 mm and 1.13 mm for implant 2. The reduction in the dental laboratory costs, the freedom to use different implant planning software programs, and the easy handling might facilitate the distribution of guided surgery and provide significant benefits for the clinician and the dental laboratory.

Implant stability in posterior maxilla: bone-condensing versus bone-drilling: a clinical study

The aim of this clinical trial was to compare primary and secondary stability of implants placed by bone condensing versus the standard drilling technique in the posterior edentulous maxilla. Forty-eight SLA Straumann implants 4.1 × 10 mm (Institut Straumann AG, Waldenburg, Switzerland) were placed into edentulous maxillary posterior region in the same positions bilaterally, using the bone condensation technique for one and the standard technique for the other side. Implant stability measurements were performed immediately after implant placement, as well as every week for the next 6 weeks by use of resonance frequency analysis (RFA). Data were analyzed using Mann-Whitney U and Wilcoxon tests. After bone condensing, significantly higher implant stability was recorded immediately after surgery as well as during the whole observation period of 6 weeks compared with bone-drilling technique (Mann-Whitney U test, P = .000). The bone-condensing technique can be recommended as an alternate surgical approach for implant site preparation in reduced bone density to achieve greater implant stability in the posterior maxilla.

Marginal Bone Level Changes at Dental Implants after 5 Years in Function: A Meta-Analysis

It is important that peri-implant bone breakdown caused by, for example, undue load and/or peri-implantitis, is prevented or minimized. Some continuous loss of marginal bone is generally accepted, but the question remains as to what extent it must occur. The purpose of this study was to compile and compare data on peri-implant marginal bone level changes from prospective studies that have registered the peri-implant marginal bone level radiographically at the time of prosthetic loading, and after 5 years of follow-up for implant systems currently available on the market. A literature search was carried out to identify prospective studies on peri-implant marginal bone level changes around dental implants. To be included in a meta-analysis, the implant systems should have been subjected to at least two independent studies. Copycats without documentation were not accepted. Forty prospective studies that presented with a 5-year data were identified. Three implant systems met the inclusion criteria of having at least two independent studies; Astra Tech Dental Implant System® (Astra Tech AB, Mölndal, Sweden), Brånemark System (Nobel Biocare AB, Göteborg, Sweden), and Straumann Dental Implant System (Institute Straumann AG, Basel, Switzerland). The pooled mean marginal bone level change amounted to -0.24 mm (95% CI -0.345, -0.135) for the Astra Tech Dental Implant System, 0.75 mm (95% CI -0.802, -0.693) for the Brånemark System, and 0.48 mm (95% CI -0.598, -0.360) for the Straumann Dental Implant System over 5 years, with a statistically significant difference (p < .01) between the systems. The identified implant systems showed an annual bone loss below or much below what hitherto has been set up as a limit for success. A careful documentation of marginal bone level changes should be mandatory for all implant systems before being marketed. It is also time for revision of existing success criteria to refine the basis for clinical quality judgment of implant treatment.

Long‐term response of osteogenic cells on micron and submicron‐scale‐structured hydrophilic titanium surfaces: sequence of cell proliferation and cell differentiation

Modifications of surface topography and surface chemistry are key factors for guiding target cells during dental implant healing. Recent in vitro studies confirmed promotion of early osteogenic cell differentiation on submicron scaled surfaces in particular when hydrophilized. However, no long-term observations on both osteogenic cell proliferation as well as on cell maturation have been reported for respectively modified surfaces. Aim of this study was to monitor osteogenic cell proliferation and expression of specific osteogenic cell differentiation markers on a protein level over an extended period of 3 weeks with respect to surface modifications. Modified titanium (Ti) disks were obtained from Institute Straumann, representing the following surfaces: smooth pretreatment (PT), sandblasted/acid etched (SLA), and hydrophilized (modSLA). Surface topography was analyzed by scanning electron microscopy, surface elemental composition was assessed by X-Ray Photoelectronic Spectroscopy (XPS). Tissue culture polystyrene (TCPS) served as a control substrate. Human osteogenic cells (HOB-c) were cultivated on the respective substrates. After 24 hrs, 48 hrs, 72 hrs, 7 d, 14 d and 21 d, cell count was assessed as well as osteogenic cell differentiation utilizing cellular Quantitative Immuno-Cytochemistry (QIC) assay for collagen type I (COL), alkaline phosphatase (AP), osteopontin (OPN) and osteocalcin (OC). Data were normalized with respect to internal controls. In contrast to the other modified Ti disks, modSLA stands out due to low surface carbon contamination. TCPS and PT surfaces preserved a rather immature, mitotic active osteogenic phenotype (high proliferation rates, no increase of OC production), SLA and especially modSLA surfaces promoted the maturation of osteogenic precursors into post-mitotic osteoblasts. In detail, modSLA resulted in lowest cell proliferation rates, but exhibited highest expression rates of OC. Our results, which confirm previous studies, reveal long-term promotion of osteogenic cell maturation by topography (micron and submicron scale roughness) and surface hydrophilicity.

Marginal Bone Level Changes and Prosthetic Maintenance of Mandibular Overdentures Supported by 2 Implants: A 5‐Year Randomized Clinical Trial

Documentation of early loading of mandibular overdentures supported by different implant systems is scarce. This study aimed to compare the biologic and prosthetic outcome of mandibular overdentures supported by unsplinted early-loaded one- and two-stage oral implants after 5 years of function. Twenty-eight consecutive patients were screened following an inclusion and exclusion criteria, and randomly allocated to treatment groups. Ball-retained mandibular overdentures were fabricated on two unsplinted Straumann (Institut Straumann AG, Basel, Switzerland) and Brånemark (Nobel Biocare AB, Göteborg, Sweden) dental implants and subjected to an early-loading protocol. During the 5-year period, prosthetic complications were recorded. At 5-years of function, plaque, peri-implant inflammation, bleeding, and calculus index scores were recorded, and standard periapical radiographs were obtained from each implant for measurement of marginal bone loss. All implants survived during the observation period. The peri-implant inflammation, bleeding, and calculus index scores around Straumann and Brånemark implants were similar (p > .05). The marginal bone loss around Brånemark implants (1.21 +/- 0.1) was higher than Straumann implants (0.73 +/- 0.06) at 5 years of function (p = .002). Kaplan-Meier tests revealed that 1- and 5-year survival of overdentures on Straumann and Brånemark implants were similar (p = .85). Wear of the ball abutment in the Brånemark group was higher than in the Straumann group (p < .05). Complications regarding the retainer and the need for occlusal adjustments were higher in the Straumann group (p < .05). Chi-square test revealed that the frequency of retightening of the retainer was higher in the Straumann group than in the Brånemark group (p < .05). Mandibular overdentures supported by unsplinted early-loaded Straumann and Brånemark implants lead to similar peri-implant soft tissue and prosthetic outcomes, although higher marginal bone loss could be observed around Brånemark implants after 5 years.

Maxillary Sinus Floor Augmentation and Simultaneous Implant Placement Using Locally Harvested Autogenous Bone Chips and Bone Debris: A Prospective Clinical Study

The aim of this study was to prospectively evaluate the status of implants, marginal bone loss, and outcome of maxillary sinus floor augmentation in patients undergoing maxillary sinus lift and simultaneous implant placement with the use of bone grafts harvested adjacent to the actual surgical site. Patients in need of maxillary sinus floor augmentation to enable implant placement were enrolled in 2 different groups. In group A, a "bone trap" was used to harvest bone debris during implant preparation with additional bone collected by further drilling adjacent to the implant sites. In group B, a "bone scraper" was used to harvest cortical bone chips from the zygomatic buttress and from the lateral sinus wall before opening of a bony window. All patients were provided a fixed partial denture after a healing period of 3 to 6 months. A total of 61 patients with 81 Straumann implants (Institut Straumann AG, Basel, Switzerland) were assessed, with 17 patients (20 implants) in group A and 44 patients (61 implants) in group B. One implant was lost (in group B) before loading. The survival rate after a follow-up of 12 to 60 months was 98.8%. There was no significant difference in marginal bone loss on the mesial and distal sides of the implant when baseline to 1-year registration was compared with baseline to final registration. During the same time, graft height decreased significantly on the distal apical side of the implants. Bone grafts can be locally harvested at the site of the maxillary sinus augmentation procedure to enable placement, successful healing, and loading of 1 to 3 implants.

Early Loading after 21 Days of Healing of Nonsubmerged Titanium Implants with a Chemically Modified Sandblasted and Acid‐Etched Surface: Two‐Year Results of a Prospective Two‐Center Study

The aim of this two-center study was to evaluate screw-type titanium implants with a chemically modified, sandblasted and acid-etched surface when placed in the posterior maxilla or mandible, and loaded 21 days after placement. All 56 patients met strict inclusion criteria and provided informed consent. Each patient displayed either a single-tooth gap, an extended edentulous space, or a distal extension situation in the posterior mandible or maxilla. Eighty-nine dental implants (SLActive, Institut Straumann AG, Basel, Switzerland) were inserted according to an established nonsubmerged protocol and underwent undisturbed healing for a period of 21 days. Where appropriate, the implants were loaded after 21 days of healing with provisional restorations in full occlusion. Definitive metal ceramic restorations were fabricated and positioned on each implant after 6 months of healing. Clinical measurements regarding soft tissue parameters and radiographs were obtained at different time points up to 24 months after implant placement. Of the 89 inserted implants, two (2.2%) implants failed to integrate and were removed during healing, and two (2.2%) additional implants required a prolonged healing time. A total of 85 (95.6%) implants were therefore loaded without incident after 21 days of healing. No additional implant was lost throughout the study period, whereas one implant was lost to follow-up and therefore left unaccounted for further analysis. The remaining 86 implants all exhibited favorable radiographic and clinical findings. Based on strict success criteria, these implants were considered successfully integrated 2 years after insertion, resulting in a 2-year success rate of 97.7%. The results of this prospective two-center study demonstrate that titanium implants with a modified SLA surface can predictably achieve successful tissue integration when loaded in full occlusion 21 days after placement. Integration could be maintained without incident for at least 2 years of follow-up.

Numerical simulation of the effect of time-to-loading on peri-implant bone

Purpose To evaluate the effect of time-to-loading on trabecular bone around single-tooth dental implants using numerical solutions based on computer models. Materials and methods A global model with a coarse mesh carrying a Straumann dental implant (043.033S; Institut Straumann, Basel, Switzerland) was created. A region of interest in trabecular bone was defined to study a localized part of the global model with a refined mesh. Time-to-loading submodels to simulate 2 h, 4 days, 1, 4, 6 and 12 wks of trabecular bone-healing status were designed and created. Bone types were considered in the simulation by different elastic bone properties. A 100-N oblique static load was applied. Maximum and minimum principal stresses were calculated and visualized. Results Bone types with higher elastic moduli experienced higher stress levels. Changes in the quality and quantity of bone at the bone-implant interface did not affect the overall stress distribution. Peri-implant bone with a higher elastic modulus preserved the stress increase at the implant–bone interface. Discussion Reduced bone contact may not have a prevailing effect over bone quality and quantity on stress generation at the peri-implant bone. Conclusion Time-to-loading of single-tooth implants may not differ in terms of load distributions in neighboring peri-implant bone.

Characterization of cast-to implant components from five manufacturers

Cast-to components are commonly used in screw-retained implant-supported restorations to produce precise fit. There is little information in the literature about the compositions and microstructures of commercially available products. The purpose of this study was to characterize as-received cast-to components from 5 manufacturers (Dentsply Friadent CeraMed, Lifecore Biomedical, Inc, Nobel Biocare AB, Institut Straumann AG, and Zimmer Dental). Two components from each manufacturer were mounted in metallographic resin, sectioned into quarters, remounted, wet polished with alumina abrasives, cleaned by ultrasonic agitation in distilled water, etched with aqua regia solutions, and carbon coated for scanning electron microscope (SEM) observation. Secondary (SE) and backscattered electron (BSE) images were collected to investigate the variations in surface topography and composition, respectively. Elemental analyses (EDS) were performed using an energy-dispersive x-ray spectrometer coupled to the SEM. Overall Vickers hardness (500-g load) and Vickers hardness of the 2 primary microstructural constituents (10-g load) were measured. Mean values and standard deviations were determined for the composition and Vickers hardness data. All implant components were composed of 2 distinctive parallel-band constituents containing gold, palladium, and platinum. Trace concentrations of iridium were also found. Elemental compositions of the darker bands observed by BSE differed by up to 20% for Au and Pt in the 5 products, whereas there was a minimal difference in Pd content. The lighter bands observed by BSE had nearly the same compositions in all 5 products, and contained much more Au and much less Pt than the darker bands. The gold-rich bands in each product were found to have much lower Vickers hardness. At high magnifications, each of the 2 bands appeared to contain 2 phases. The elemental compositions, microstructures, and Vickers hardness of the 5 as-received cast-to implant components were similar. Because both microstructural bands principally contain gold, palladium, and platinum, these noble cast-to implant components should be metallurgically compatible with noble metal casting alloys.