Screw-retained Restorations Research Articles

Screw loading and gap formation in implant supported fixed restorations: Procera implant bridge vs. conventionally cast screw-retained restorations

It was the purpose of this finite element analysis to compare the implant-restoration connection created by Procera Implant Bridge (PIB) and conventional screw-retained prostheses with respect to screw loading and gap formation. Finite element models representing a conventional screw-retained restoration and a PIB were set up. A horizontal load of 200N was applied on the restorations while resulting gap formation and screw loading was recorded. Increasing the preload of the retaining screws led to a decrease in gap formation. Smaller gaps were observed in the conventional restorations. Loading of the screws was of comparable magnitudes in both cases. The use of screw-retained implant-supported restorations representing butt-joint connections at the restorative interface may result in increased gap formation.

Peri‐implant bone loss in cement‐ and screw‐retained prostheses: Systematic review and meta‐analysis

The aim of this systematic review and meta-analysis was to assess and compare peri-implant marginal bone loss in cement- and screw-retained prostheses. Electronic database and manual searches were undertaken to identify trials, prospective or retrospective studies reporting on radiographic marginal bone loss around dental implants restored with cement- and/or screw-retained prostheses. Two reviewers independently conducted the article selection and data extraction. Random-effects models were used to obtain estimates of peri-implant marginal bone loss [mean, 95% confidence intervals (CI)]. Of the 1217 identified studies, nine finally met the inclusion criteria. Only two studies included both cement- and screw-retained prostheses, three assessed only screw-retained prostheses, and four evaluated only cement-retained prostheses. Pooled mean marginal bone loss was 0.53mm (CI 95%, 0.31-0.76mm) for cement-retained prostheses and 0.89mm (CI 95%, 0.45-1.33mm) for screw-retained prostheses. There is no evidence to support differences in the marginal bone loss through indirect comparison between cement and screw-retained restorations.

A three-dimensional image-superimposition CAD/CAM technique to record the position and angulation of the implant abutment screw access channel

Cement-retained, implant-supported restorations have advantages over screw-retained restorations, but retrievability can be a problem. By using computer-aided design and computer-aided manufacturing (CAD/CAM) technology, a working cast or mouth can be scanned, and a definitive record of the screw hole can be made in 3 dimensions and saved as a file. This information includes not only the position of the opening of the screw hole but also its angulation and orientation, which can be retrieved if required.

Factors influencing success of cement versus screw-retained implant restorations: a clinical review

Aim As more and more dental practitioners are focusing on implant-supported fixed restorations, some clinicians favor the use of cement retained restorations while others consider screw retained prosthesis to be the best choice. Discussion In screw-retained restorations, the fastening screw provides a solid joint between the restoration and the implant abutment, while in cement-retained prostheses the restorative screw is eliminated to enhance esthetics, occlusal stability, and passive fit of the restorations. The factors that influence the type of fixation of the prostheses to the implants like passivity of the framework, ease of fabrication, occlusion, esthetics, accessibility, retention and retrievability are discussed in this article with scientific studies demonstrating superior outcomes of one technique over another. Screwretained implant restorations have an advantage of predictable retention, retrievability and lack of potentially retained subgingival cement. However, a few disadvantages exist such as precise placement of the implant for optimal and esthetic location of the screw access hole and obtaining passive fit. On the other hand, cement retained restorations eliminate unesthetic screw access holes, have passive fit of castings, reduced complexity of clinical and lab procedures, enhanced esthetics, reduced cost factors and non disrupted morphology of the occlusal table. Conclusion This article compares the advantages, potential disadvantages and limitations of screw and cement retained restorations and their specific implications in the most common clinical situation.

Peri‐implant tissue reactions to immediate nonocclusal loaded implants with different collar design: an experimental study in dogs

The aim of this study was to evaluate bone remodelling and soft tissue reactions around immediate nonocclusal loaded implants with different collar configuration in beagle dogs. The mandibular bilateral second, third and fourth premolars of six beagle dogs were extracted. After 3 months of healing, four implants were placed in the mandibles of each dog. Randomly, two implants with a 1.5 mm polished surface collar (TSA, control group) and two implants with a 0.7 mm polished surface collar and 2.5 mm microthreaded area (TSAA, test group) were inserted. Both groups were treated with a minimal mucoperiosteal flap elevation approach. Impressions were taken and two single screw-retained restorations were inserted in each hemi-mandible 2 days after the implant placement. The animals were sacrificed at 1, 2 and 3 months (two specimens each), and biopsies were obtained. Samples were processed for ground sectioning. Histomorphometric analysis was carried out to compare buccal and lingual bone height loss and soft tissue behaviour between the two groups. Crestal bone resorption was significantly higher in the control group (P > 0.05). The establishment of the biological width showed similar outcomes for both groups. Only the distance from the top of the peri-implant mucosa to the apical portion of the barrier epithelium at lingual aspect was significantly more pronounced in the control group (P > 0.05). The alterations that occurred in the peri-implant tissues were related to the adaptation that occurred after the loading conditions in both groups. The microthread design might have an effect in maintaining the marginal bone loss against loading.

Does residual cement around implant‐supported restorations cause peri‐implant disease? A retrospective case analysis

The purpose of this study was to determine the relationship between patients with a history of periodontitis and development of cement-related peri-implant disease. Seventy-seven patients with 129 implants for this retrospective analysis were selected from completed implant cases that were scheduled for regular maintenance or had experienced mechanical or biological complications between years 2006 and 2011 in private practice. Implants with extracoronal residual cement and implants without cement remnants were analyzed. The selected cases were further divided into two groups--implants in patients with history of periodontitis (1) and implants in periodontitis-free individuals (2). The selection of these groups was made on the basis of treatment history and orthopantomograph. As a control group, a set of 238 screw-retained implant restorations, delivered to 66 patients during the same period of time was examined. The incidence of peri-implant disease among implants in all groups was calculated. Peri-implant disease was evident in 62 of 73 implants with cement remnants (85%). All implants in group 1 developed peri-implantitis--4 early and 35 delayed disease cases. In the periodontally healthy group, 20 of 31 implants were diagnosed with peri-implant mucositis, 3 implants had early peri-implantitis, and 11 implants with cement remnants did not develop biological complications. In the group of implants without cement remnants, peri-implant disease was diagnosed in 17 of 56 cases (30%). In contrast, only two occurrences of peri-implant disease were registered in the control group of screw-retained restorations (1.08%). Implants with cement remnants in patients with history of periodontitis may be more likely to develop peri-implantitis, compared with patients without history of periodontal infection.

A modified technique to locate the abutment screw access opening of a cemented implant-supported restoration

Cemented implant-supported restorations have advantages relative to those which are screw retained, including greater passivity of fit and better esthetics.1 However, the easier retrievability of a screw-retained restoration is clinically useful should an abutment screw become loose. Abutment loosening of a cemented implant crown usually necessitates estimating the location of the abutment screw access opening, and accessing the screw by drilling through the crown. Several articles have been written describing methods for indicating the location of the abutment screw, either prior to or after the restoration has been cemented.

Performance of the Straumann Bone Level Implant system for anterior single‐tooth replacements in augmented and nonaugmented sites: A prospective cohort study with 60 consecutive patients

The purpose of this prospective study was to evaluate radiographic, clinical and aesthetic outcomes and patient satisfaction of cases treated with platform-switched single implant restorations in the aesthetic region of the maxilla. Furthermore, the influence of an augmentation procedure 3months before implant placement and the type of restoration (screw-retained vs. cement-retained) was evaluated. Sixty patients with a missing anterior tooth in the maxilla were treated with a Straumann Bone Level Implant. Bone augmentation was performed in 29 patients at 3months before implant placement. Implants were loaded after 3months of submerged healing. Follow-up was conducted at 7 and 18months after implant placement. Peri-implant mucosa and implant crown aesthetic outcomes were determined using the Implant Crown Aesthetic Index (ICAI) and the Pink Esthetic Score-White Esthetic Score (PES-WES). No implants were lost. At 18months after implant placement, mean bone level change was -0.10±0.27mm and mean probing pocket depth was 2.57mm. No differences were found between augmented and nonaugmented sites (P=0.28). The ICAI indicated satisfactory mucosa and crown aesthetics in 67% and 75% of the cases, respectively, while the PES score was 14.4. ICAI mucosa (P=0.004) and PES (P=0.02) scores were significantly less favourable for augmented sites compared with nonaugmented sites. Patient satisfaction was high (8.9±1.1 on VAS-score). From the present prospective, clinical study, it can be concluded that the Straumann Bone Level Implant shows an excellent survival rate, marginal bone stability and good clinical and aesthetic results. Bone augmentation before implant placement does not lead to more marginal bone loss. However, less favourable pink aesthetic outcomes were found in augmented sites compared with nonaugmented sites, while no differences were found between cement-retained and screw-retained restorations.

Effect of implant connection and restoration design (screwed vs. cemented) in reliability and failure modes of anterior crowns

The mechanical performance of cemented or screw-retained implant-supported crowns with an internal or external configuration is yet to be understood. This in vitro study evaluated the effect of screw-retained and cement-retained prostheses on internal and external implant-abutment connections. Thereby, the reliability and failure modes of crowns were investigated. Eighty-four implants (Emfils; Colosso Evolution system) were divided into four groups (n=21 each): screw-retained and internal connection (Si), screw-retained and external connection (Se), cement-retained and internal connection (Ci), and cement-retained and external connection (Ce). Ti-6Al-4V abutments were torqued (30 Ncm) to the implants, and maxillary central incisor metal crowns were torqued (30 Ncm) or cemented (Rely X Unicem; 3M-ESPE) and subjected to accelerated life-testing in water. Use-level probability Weibull curves and reliability for 50,000 cycles at 150 N were calculated. The β values for Si (1.72), Se (1.50), Ci (1.34), and Ce (1.77) groups indicated that fatigue/damage accumulation accelerated their failure. The Ci group presented the highest reliability, the Se group presented the lowest reliability, and Si and Ce groups presented intermediate reliability. Screw-retained restorations presented mainly abutment fracture. Cement-retained restorations resulted in failures of the screw in the Ce group, but implant/screw fracture in the Ci group.

COMMENTARY. An Esthetic Solution to the Screw-Retained Implant Restoration: Introduction to the Implant Crown Adhesive Plug: Clinical Report

COMMENTARY. An Esthetic Solution to the Screw-Retained Implant Restoration: Introduction to the Implant Crown Adhesive Plug: Clinical Report

A Method for Obtaining Peri-Implant Soft-Tissue Contours by Using Screw-Retained Provisional Restorations as Impression Copings: A Clinical Report

In the esthetic zone, remodeling of the peri-implant soft-tissue contours through the use of provisional restorations is one of the imperative key factors for optimizing outcomes. Several methods have been described to produce the desired peri-implant soft-tissue contours using customized impression copings or cement-retained provisional crowns. The aim of this article is to present an alternative method for obtaining the desired peri-implant soft-tissue contours by using screw-retained provisional restorations as impression copings, which facilitates the definitive prosthesis fabrication.

Porcelain Fracture Resistance of Screw‐Retained, Cement‐Retained, and Screw‐Cement‐Retained Implant‐Supported Metal Ceramic Posterior Crowns

The purpose of this in vitro study was to compare the porcelain fracture resistance between screw-retained, cement-retained, and combined screw- and cement-retained metal-ceramic (MC) implant-supported posterior single crowns; and to investigate the effect of offsetting the occlusal screw-access opening on porcelain fracture resistance of screw-retained and cement-retained MC implant-supported posterior single crowns. Forty standardized MC molar-shaped restorations were fabricated. The 40 restorations were divided into four groups (SRC, SRO, CRP, and CSC) of 10 specimens each. Group SRC: screw-retained, screw-access hole placed in the center of the occlusal surface; Group SRO: screw-retained, screw access hole placed 1 mm offset from the center of the occlusal surface toward the buccal cusp; Group CRP: cement-retained, zinc phosphate cement was used; Group CSC: cement-retained with a screw-access hole in the center of the occlusal surface. The screw-retained restorations and abutments were directly attached to 3i implant fixtures embedded in acrylic resin blocks. Subsequently, all test specimens were thermocycled and vertically loaded in a universal testing machine at a crosshead speed of 2 mm/min until fracture. Mean values of load at fracture (in N) were calculated in each group and compared with a one-way ANOVA and Tukey's Studentized test (alpha= 0.05). Mean values of loads required to fracture the restorations were as follows (N): Group SRC: 1721 +/- 593; Group SRO: 1885 +/- 491; Group CRP: 3707 +/- 1086; Group CSC: 1700 +/- 526. Groups SRC, SRO, and CSC required a significantly lower force to fracture the porcelain than did the CRP group (p < 0.05). The cement-retained restorations showed significantly higher mean fracture loads than the restorations having screw-access openings in their occlusal surface. The position of the screw-access hole within the occlusal surface did not significantly affect the porcelain fracture resistance.

Full-Arch Metal-Resin Cement- and Screw-Retained Provisional Restoration for Immediately Loaded Implants

Abstract This article describes the clinical and laboratory procedures involved in the fabrication of laboratory-processed, provisional, screw-retained, implant-supported maxillary and mandibular fixed complete dentures incorporating a cast metal reinforcement for immediate loading of implants. Precise fit is achieved by intraoral luting of the cast frame to milled abutments. Effective splinting of all implants is attained by the metal substructure and retrievability is provided by the screw-retention of the prosthesis.

Effect of Implant Design on Preservation of Marginal Bone in the Mandible

Implant design and surface may have an influence on the marginal bone response during immediate functional loading. The purpose of this study was to radiographically study the effect of implant design on marginal bone preservation at immediately loaded implants used for prosthetic rehabilitation of the completely edentulous mandible. A total of 39 patients, previously treated with five implants for support of a full-arch fixed bridge in the mandible, were included in the study. Either machined Brånemark implants (Ma) (Nobel Biocare AB, Gothenburg, Sweden) or surface modified Astra Tech implants with (Mi) or without a microthreaded neck (Ti) (TiOblast, AstraTech AB, Mölndal, Sweden) were used. All fixtures were loaded with a provisional glass fiber or metal-reinforced screw-retained restoration within 24 hours. The provisional restorations were replaced by a 12-unit screw-retained metal-ceramic or metal-resin cantilever bridge after 3 months. Bone loss from baseline to 1 year of loading was measured by means of intraoral radiographs. Only patients with baseline and 1-year radiographs of all implants were selected for comparison. Statistical analysis was carried out on both patient and implant levels. The survival rates after 1 year in function were 98.6, 100, and 100% for the Ma, Ti, and Mi implants, respectively. The overall mean bone loss after 1 year was 1.03 mm (SD 0.87; range -0.77 to 2.5). The mean bone loss was calculated to 1.52 (SD 0.66) for the Ma group, 0.79 (SD 0.79) for the Ti group, and 0.70 (SD 1.01) for the Mi group. There was a significant difference between Ma and Ti (p = .023) and between Ma and Mi (p = .046) groups but not within Ti and Mi implants (p = .70). These conclusions were also valid when the statistical analysis was performed on implant level. There is no impact of design and surface on implant survival in the completely edentulous mandible. Bone preservation in immediately loaded implants in the mandible is influenced by implant design and significantly better on surface-modified AstraTech implants compared with machined Brånemark implants. In the mandible, a microthread design of the implant collar does not seem to improve bone preservation.

Retrofitting a tooth-supported crown with an implant and abutment: A clinical report

This article presents a treatment option for a fractured maxillary central incisor root as part of an existing complete maxillary rehabilitation. After the root extraction and immediate implant placement into the extraction socket, an acrylic resin removable partial denture (RPD) was placed. Six months later, a screw-retained provisional restoration was placed to guide the development of soft tissue contours. An impression was made, and a custom abutment was fabricated to conform to the new gingival profile and the intaglio surface of the existing metal ceramic crown. The custom abutment was placed and the preexisting metal ceramic crown was then cemented.

Immediate Loading of Immediate Mandibular Implants With a Full-Arch Fixed Prosthesis: A Preliminary Study

To determine the survival of immediate dental implants with immediate loading in the partially edentulous mandible, by use of a full-arch screw-retained provisional restoration. Patients who were partially edentulous in the mandible with indications for extraction of the remaining teeth and with a minimum follow-up of 12 months after implant placement were included in the study. They were treated in chronologic order by the insertion of 6 Defcon dental implants (Impladent, Sentmenat, Spain) subjected to immediate loading (4 interforaminal and 2 posterior placements). Implants with a minimum primary stability of 60 implant stability quotient were loaded. All resin screw-retained prostheses were inserted and loaded with fully functional occlusion within 24 hours of implant placement. Eleven patients were treated with immediate implants, although 2 patients were excluded from the study for having an implant stability quotient value below 60 in at least one of the implants after surgery and did not undergo restoration with immediate loading. Fifty-four implants were placed in 9 partially edentulous patients with immediate loading with a full-arch screw-fixed prosthesis. The patients wore this provisional prosthesis during the healing period (2 months) without complication and with a high level of comfort. The survival rate of the implants was 100% at 12 months of follow-up. Immediate mandibular loading with immediate full-arch implant-supported and screw-retained restorations is a viable treatment alternative, yielding a 100% success rate in this small series of patients.

Immediate functional loading of TiOblast dental implants in full‐arch edentulous maxillae: a 3‐year prospective study

Immediate functional loading of dental implants for full-arch restoration is a patient-friendly approach, shown to be feasible with a good long-term prognosis in a completely edentulous mandible. For the complete restoration of the maxilla, acceptable long-term clinical follow-up is lacking or based on case reports rather than on prospective studies. This prospective mono-centre study reports the 3-year outcome of immediately functionally loaded Astra Tech Dental implants in completely edentulous maxillae based on clinical survival and success based on radiographical assessment of bone level. One hundred and ninety-five Astra Tech TiOblast surface fixtures were installed in 25 consecutively treated patients (age range: 42-76 years), of whom eight were smokers, 12 had a confirmed history of periodontitis and six had poor bone quality normally deemed for delayed loading. Fixtures and abutments were inserted in a one-stage procedure and functionally loaded within 24 h with a 10-unit provisional glass-fibre or metal-reinforced screw-retained restoration. After 6 months, each implant was checked for stability using a manual torque of 20 N cm and the provisional restoration was replaced by a 10-12-unit screw-retained metal-ceramic or metal-resin cantilever bridge. Bone level was assessed radiographically from the day of surgery up to 3 years and used to calculate mean bone loss at the patient level and individual implant success. No failures occurred in implants or prostheses, the total survival rate being 100%. Mean marginal bone loss was 0.58 mm (SD 0.58); 0.6 mm (SD 0.53); 0.63 (SD 0.61); and 0.72 (SD 0.63) after 6 and 12 months, and 2 and 3 years, respectively, yielding a 100% success at the patient level. Wilcoxon's signed ranks test showed only statistically significant bone loss between baseline and 6 months and a steady-state condition during all other intervals. At the individual fixture level, 82% lost <1 mm marginal bone between baseline and 1 year. After 3 years, 86% have <1.5 mm total bone loss and can be considered a success. The fixtures expressing more bone loss were all inserted in smokers. Immediate loading of a full-arch maxillary bridgework on 7-9 Astra Tech TiOblast implants is a predictable treatment option with 100% fixture survival and stable bone-to-implant contact up to 3 years. The steady state in bone remodelling is indicative of a good long-term prognosis in non-smokers but smokers seem to be more prone to bone loss.

Telescoping implant prostheses with intraoral luted galvano mesostructures to improve passive fit

A passive fit of implant-supported prostheses seems to be a prerequisite for the prevention of mechanical complications. As a certain level of distortion of multiimplant screw-retained restorations seems inevitable, cementation of implant frameworks has been advocated to compensate for discrepancies. However, cement-retained prostheses have disadvantages, including lack of retrievability. This article describes a technique for the fabrication of telescopic, metal-acrylic resin, implant-supported complete dentures. Precise fit is achieved by intraoral luting of telescopic galvano mesostructures to the framework.

Fabrication of a Cement- and Screw-retained Multiunit Implant Restoration

Retrieval of cemented implant restorations can be difficult for both the patient and the dentist. The method described in this article combines the advantages of cement- and screw-retained restorations. Abutment screws can be easily reached by the screw access channel prepared in the waxing phase; the restoration can be retrieved without destroying the implants and prosthesis. This article describes a simple and reliable method to fabricate a retrievable cemented prosthesis.

A technique for the manipulation of prosthetic screws intraorally

The insertion of an implant-supported prosthesis is easier when the prosthesis is cement-retained. 1 Misch C.E. Contemporary implant dentistry. 2nd ed. Mosby, St Louis1998 Google Scholar , 2 Hebel K.S. Gajjar R.C. Cement-retained versus screw-retained implant restorations: achieving optimal occlusion and esthetics in implant dentistry. J Prosthet Dent. 1997; 77: 28-35 Abstract Full Text Full Text PDF PubMed Scopus (374) Google Scholar This is due to the larger size and, consequently, easier manipulation of the prosthetic implant components needed to complete a cement-retained restoration (abutment and abutment screw), compared to the size of the prosthetic screws used in screw-retained restorations. Hand manipulation of the prosthetic screws in screw-retained restorations can be difficult intraorally, especially in posterior areas, because of their small head size. Screws are not easily held by the screwdriver tip. A simple technique to manage prosthetic screws intraorally during the insertion of screw-retained prostheses is described. The sticky consistency of the gel/petroleum jelly allows easier clinical manipulation of the prosthetic screw with the screwdriver.