Non‐Radiological Method for Fabrication of a Screw‐Channel Drilling Guide in Cement‐Retained Implant Restorations Using Intraoral Digital Scanning and Imaging Superimposition: A Clinical Report

The difficulty of retrieving the abutment screw is a major disadvantage of cement‐retained implant restorations. Conventional methods for locating the screw‐access hole are based largely on radiography or manual labor, which limits accuracy and clinical feasibility. This clinical report describes a non‐radiological method for fabricating an accurate drilling guide for location of the screw channel using intraoral optical scanning, 3D superimposition, and computer‐aided design and computer‐aided manufacturing (CAD/CAM) technologies. The present technique not only improves the guide fabrication process and the accuracy of screw‐channel drilling, but also has wide indications for implant restorations.     

An Alternative Design to Overcome the Problem of Unfavorable Implant Angulations for a Screw‐Retained,Implant‐Supported Fixed Prosthesis: Two Clinical Reports

Two clinical reports present an alternative design to address the problem of unfavorable implant angulations if a screw‐retained prosthesis is desired. The restorations were designed as screw‐retained prostheses, except in the area with the unfavorable implant screw emergence. The frameworks in these areas were customized to receive individual cement‐retained crowns. This design offers retrievability and helps to minimize complications associated with excess cement without compromising the functional or esthetic outcome.     

Cement Selection for Cement‐Retained Implant‐Supported Prostheses: A Literature Review

Cement‐retained implant‐supported prostheses are widely used for restoring missing teeth; however, they show some complications in comparison to screw‐retained restorations, such as difficulty in retrieving the restoration and biocompatibility of cement. Therefore, the practitioner should consider several important aspects when using this type of restoration. In this regard, one major concern is appropriate cement selection, with considerations including cement biologic compatibility, methods for limiting the excess cement, ease of removing the excess cement, radiographic view of the cement, and also the possibility of future retrieval of the prosthesis. The aim of this review article was to address most aspects related to this type of prosthesis in terms of cementation.     

Management of a Fractured Multiunit Maxillary Implant‐Supported Fixed Prosthesis with Stripped Abutment Screws Using a Hybrid Cement‐Retained and Screw‐Retained Design: A 5‐Year Follow‐Up Clinical Report

Fracture and loosening of implant‐supported prostheses (ISPs) are complications encountered in routine dental practice. In the present report, management of a fractured maxillary full‐arch cement‐retained (CR) fixed dental prosthesis supported by six implants is presented. Due to stripped screws, complications were encountered that prevented the retrieval of two of the six abutment screws, which was managed by using a hybrid retention approach, whereby a single full‐arch CR and screw‐retained (SR) ISP was used. The techniques used to successfully retrieve four of the abutment screws are described. The final retention design involved a combination of three CR and three SR restorations, which offers the advantages of both retention designs.     

Using a Porcelain Furnace to Debond Cement‐Retained Implant Crown from the Abutment after Screw Fracture: A Clinical Report

When a screw fracture occurs on a cement‐retained, implant‐supported restoration, the abutment and restoration are completely separated from the implant's internal connection. Traditionally, an access hole is drilled through the crown to retrieve the broken screw, and the restoration can be placed again as a screw‐retained restoration. This clinical report documents a patient whose broken abutment screw was retrieved from the restoration by burning off the cement and separating from the abutment without drilling an access hole.     

Three‐Dimensional Image Correlation Analyses for Strains Generated by Cement and Screw‐Retained Implant Prostheses

Purpose: This study aimed to measure and compare strains generated by splinted implant crowns retained by cement or screws for two implants with applied load. Materials and Methods: A stereolithic resin model was printed using computed tomography data from a patient missing all mandibular molar teeth. Two 4 × 6 mm implants were consecutively placed in the left side. One set of splinted cement and screw‐retained crowns were made to fit the two implants. Image correlation technique was used for full‐field measurement of strains using an image correlation software and two synchronized high‐resolution digital cameras. A random dot pattern was applied to the model surface. Cameras recorded changes in random dot patterns as prostheses were loaded up to 400 N in vertical and oblique directions using a universal testing machine. Testing was repeated three times for cement and screw‐retained prostheses. An image correlation algorithm used the dot pattern to define correlation areas or virtual strain gauge boxes. Three‐dimensional coordinates of gauge box centers were determined for each recorded photograph and used to calculate strains. Strain distribution data were compared for major, minor, and von Mises strains for each loading condition, as well as peak and average strains for the field of view using an analysis of variance (α = 0.05). Results: Patterns and magnitudes of strain for cement‐ and screw‐retained splinted crowns were similar under vertical loading. Neither peak nor mean strains were significantly different for the two retention methods. For oblique loading, peak strains were lower for the screw‐retained crowns; however, there were no statistically significant differences between the two groups when strains were averaged throughout the entire field of view. Conclusions: Cement retention did not improve the magnitude of transferred strains for splinted implant crowns using either loading condition.     

Replacement of Missing Anterior Tooth Using Screw Retained Implant Prosthesis in the Esthetic Zone: A Case Report with 3 Years of Follow Up

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. As both types of prostheses have certain advantages and disadvantages, clinicians should be aware of the limitations of each type. Screw-retained implant restorations have an advantage of predictable retention, retrievability and lack of potentially retained sub-gingival 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 eliminates unaesthetic screw access holes; have passive fit of castings; reduce stress to splinted implants because of minor misfit of the framework; reduced complexity of lab procedures; enhanced esthetics; reduced cost factors and non disrupted morphology of the occlusal table. This case report presents the replacement of missing left central incisor using screw-retained implant prosthesis due to palatal trajectory of the implant placement and inadequate abutment height for retention of cement retained prosthesis.     

Effect of Engaging Abutment Position in Implant‐Borne,Screw‐Retained Three‐Unit Fixed Cantilevered Prostheses

Purpose: To investigate the effects of internally connected engaging component position in screw‐retained fixed cantilevered prostheses. Materials and Methods: Twenty‐one three‐unit fixed dental prostheses (FDPs) were cast in high‐palladium alloy in three groups. In group A, engaging components were incorporated into the units away from the cantilevered segment; proximal units received nonengaging components. In group B, these positions were reversed. Control specimens were fabricated using all nonengaging components. Specimens were attached to internally connected 3.5 (diameter) × 13 mm (length) implants, torqued to 32 Ncm, and embedded into epoxy resin. Specimens were tested in cyclic fatigue with a 2 Hz sine wave and 0.1 min/max load ratio. Load amplitude started at 1.8 N and increased by 1.8 N every 60 cycles until fracture. Log‐rank statistic, ANOVA, Spearman's correlation, and LIFETEST procedures were used to evaluate level of statistical significance within the results. Results: In the control group, the mean number of cycles to fracture was 31,205 ± 2639. Mean axial force at fracture was 932 ± 78 N. In group A, these numbers were 38,160 ± 4292 and 1138 ± 128 N, and in group B, 31,810 ± 3408 and 949 ± 101 N. Statistical significance levels for number of cycles to fracture were: Control versus group A, p= 0.0117, and groups A versus B, p= 0.0156 (statistically significant). Control versus group B, p= 0.357 (not statistically significant). Log‐rank statistic for the survival curves is greater than would be expected by chance; there was a statistically significant difference between survival curves (p= 0.012). The location and mode of failure were noteworthy (always in the abutment screw). Conclusions: The position of the engaging component had significant effects on the results. Within the limitations of this investigation, it can be concluded that using an engaging abutment in a screw‐retained fixed cantilevered FDP provides a mechanical advantage, and engaging the implant furthest from the cantilever when designing a screw‐retained cantilever FDP increased resistance to fracture of the distal abutment screw.     

Three‐Dimensional Location of the Retaining Screw Axis for a Cemented Single Tooth Implant Restoration

Retrievability is a major concern with cemented versus screw‐retained implant restorations. This article describes the use of cone beam radiography to help target and create a precise screw access opening for a loosened implant‐supported single crown retained by cement to its abutment.     

Microbial Colonization of the Peri‐Implant Sulcus and Implant Connection of Implants Restored With Cemented Versus Screw‐Retained Superstructures: A Cross‐Sectional Study

Background: The aim of this study is to investigate peri‐implant and intraconnection microflora of healthy implants restored with cemented and screwed superstructures. Methods: Patients with two to three implants restored with cemented or screwed restorations and 5 years of follow‐up were recruited. Samples were taken from peri‐implant sulci, adjacent teeth, and the inner portion of connections. Prevalence of positive sites and bacterial loads for 10 microorganisms were obtained with quantitative real‐time polymerase chain reaction. Implant connection permeability to the studied microorganisms was estimated using a standardized bacterial contamination index. Statistical analysis was performed using a generalized estimating equations model, Wald χ² test, and the least significant difference test. Results: The final sample consisted of 18 patients (55 implants) in the cemented group and 22 patients (46 implants) in the screw‐retained group. Regarding prevalence of positive sites, significant differences between groups were only found for Tannerella forsythia, which was 8.7 times more frequent at peri‐implant sulci of cemented than screw‐retained prostheses. Bacterial loads of Porphyromonas gingivalis, T. forsythia, Parvimonas micra, and total bacterial load were significantly higher at peri‐implant sulci for the cemented group; at the inner portion of connections, values were significantly higher for P. micra and Fusobacterium nucleatum for the screw‐retained group. Contamination index values demonstrated higher permeability to most microbes in the cemented group. Conclusions: Internal implant surfaces were microbiologically contaminated for both cemented and screw‐retained superstructures. Differences were found between the two methods of prosthetic retention: the cemented group presented significantly higher bacterial loads in the peri‐implant sulcus but significantly lower bacterial loads at the inner portion of the implant connection.     

A comparison of the porcelain fracture resistance of screw-retained and cement-retained implant-supported metal-ceramic crowns

STATEMENT OF PROBLEM: The presence of a screw opening on the occlusal surface of implant-supported metal-ceramic crowns may decrease the porcelain fracture resistance and shorten the longevity of the crown. PURPOSE: The purpose of this study was to compare the porcelain fracture resistance between screw-retained and cement-retained implant-supported metal-ceramic crowns and to assess whether narrowing the occlusal table or offsetting the screw-access opening affects fracture resistance. MATERIAL AND METHODS: Forty standardized maxillary premolar metal copings were fabricated with a Pd-Ga alloy (Protocol) on an implant abutment. Copings were divided into 4 groups (n=10): Group 1 (Screw-retained; occlusal surface buccolingual width=5 mm), screw access opening placed in the center of the occlusal surface; Group 2 (Screw-retained; occlusal surface buccolingual width=5 mm), screw access opening positioned 1 mm offset from the center of the occlusal surface toward the buccal cusp; Group 3 (Cement-retained; occlusal surface buccolingual width=5 mm), copings were not altered; and Group 4 (Cement-retained; occlusal surface buccolingual width=4 mm), copings designed to have a reduced occlusal surface width. All castings were finished with aluminum oxide stones and airborne-particle abraded. Two layers of opaque and dentin porcelain were applied, respectively, on all specimens, which were then glazed. The crown specimens were positioned in a custom testing apparatus and vertically loaded on the middle of the occlusal surface with a universal testing machine at a crosshead speed of 0.5 mm/min until fracture. Mean values of load at fracture (Kgf) were calculated in each group and compared with a 1-way analysis of variance and Tukey's Studentized test (alpha=.05). RESULTS: Mean values of loads required to fracture the crowns were as follow: Group 1: 95.01+/-46.6 Kgf; Group 2: 108.61+/-57.9 Kgf; Group 3: 390.94+/-151.3 Kgf; Group 4: 380.04+/-211.8 Kgf. Groups 1 and 2 required a significantly lower force to fracture the crowns compared with Groups 3 and 4 (P=.0001). Comparing Group 1 with 2 (P=.9) and Groups 3 with 4 (P=.6), no significant differences were noted. CONCLUSIONS: Screw-retained implant-supported metal-ceramic crowns demonstrated a significantly lower porcelain fracture resistance than cement-retained crowns. Placing the screw access opening 1 mm offset from the center of the occlusal surface did not result in lower fracture resistance. Cement-retained crowns with 4- or 5-mm buccolingual width of the occlusal surface showed similar porcelain fracture resistance.     

Investigation of the Association Between Cement Retention and Prevalent Peri‐Implant Diseases: A Cross‐Sectional Study

Background: The aim of this study is to examine the association between retention type (cement‐retained versus screw‐retained restorations) and prevalence of peri‐implant diseases in a German university‐treated population. Methods: Data were analyzed from individuals that underwent clinical and radiographic peri‐implant examinations as part of a university‐based cross‐sectional study from September 2011 to October 2012. Results: Data from 139 individuals (mean age: 57.59 years) having 394 implants were analyzed: 192 implants supporting single crowns and 202 fixed partial dentures. Overall, 11.9% of the participants had peri‐implantitis, whereas 68.9% had peri‐implant mucositis. Crude odds ratios (95% confidence intervals) for peri‐implantitis and peri‐implant mucositis for cement‐ versus screw‐retained restorations were 1.43 (0.45, 4.60) and 0.89 (0.53, 1.48), respectively. Results remained non‐significant in multivariable models adjusting for type of restoration and smoking (all P values >0.50). There was also no effect of splinting restorations on disease prevalence in adjusted analyses (P values >0.32). Conclusions: In this university‐treated sample, there is no association between the type of prosthesis retention and peri‐implant diseases. Current findings show that, when appropriate selection and removal of cement is performed, cement retention is not a risk indicator for peri‐implant diseases.     

A Novel Approach for Converting a Mandibular Complete Denture to a Fixed Interim,Screw‐Retained Implant Prostheses: A Case Report

For most of the last century, conventional complete dentures have been the standard of care and the most common treatment for edentulous patients. Technological advancements in fabrication techniques may significantly reduce the number of office visits required to fabricate complete dentures. Immediate occlusal loading with mandibular full arch prostheses has been extensively researched and is now one of the standards of care for edentulous patients. A clinical technique for converting a mandibular immediate complete denture to an interim full arch, screw‐retained fixed prosthesis with novel implant restorative components for immediate loading on four implants is described.     

Z350复合树脂不同厚度组充填螺丝固位式种植修复体入路孔的实验研究

目的:采用Z350 复合树脂材料推测充填厚度对螺丝固位型种植义齿的入路孔周围瓷层的影响。方法:实验样品随机均分为3组;对颌用BEGO 合金制作的金属联冠。将3组样品的入路孔用棉球填塞后分别留2.0 mm、3.5 mm 和5 mm的深度,按照预留深度充填Z350复合树脂后调牙合、抛光,10 个样品分别在0~100 N,1 Hz,20000次受到沿种植体长轴方向的力,加载完毕后在场发射电子显微镜下观察,计数在钉道口周围0.5 mm内的裂纹数量,将3组数据进行统计学分析。结果:对测得的实验数据进行统计学分析:Z350复合树脂3.5 mm充填组和5.0 mm充填组之间不存在统计学差异,2.0 mm充填组与其他两组有统计学差异。结论:3.5 mm厚度对表面瓷和树脂的受力后性能的改善明显,继续增加厚度对表面瓷和树脂的受力后性能的改善没有统计学意义。     

An esthetic solution to the screw-retained implant restoration: introduction to the implant crown adhesive plug: clinical report

Screw-retained implant crowns may be clinically demanding, especially managing the esthetic and occlusal challenges of screw access channel closure. Many clinicians have moved away from using screw retention as a means of fixing a crown to an implant in favor of cementation to an underlying abutment. A link has been established between peri-implant disease and excess cement extrusion in cement-retained implant restorations. This article describes a novel technique of bonding a pressed porcelain plug into the screw access channel of an implant restoration that allows for control of occlusion, matches the esthetics of a cement-retained crown, and eliminates the issues of excess cement. CLINICAL SIGNIFICANCE: Overcoming the restorative challenges (esthetic, occlusal) of the screw access channel in a screw-retained implant restoration is difficult. By fabricating a pressed ceramic over metal crown and esthetic plug these challenges can be dealt with in a predictable manner.     

The cross‐pin retained implant supported restoration: a study of gasket placement and leakage

Background: Advantages of cross‐pin retained implant supported restorations (ISRs) include predictable retrieval and predictable retention. Unlike direct to fixture (DTF) or cement retained restorations, the prosthetic design of a cross‐pinned restoration retains gaps at the interfaces between the crown, abutment and cross‐pin screw. These spaces permit leakage into the suprastructure and gasket placement has been recommended to prevent this leakage. Methods: Five different gaskets were assessed for their ability to prevent leakage into a cross‐pinned ISR. The gaskets tested were: cement admixture on the cross‐pin screw; cement admixture on the inner surface of the coping and the cross‐pin screw; cement admixture on the inner surface of the coping only; cement admixture placed 1 mm from the margin of the coping and a filler placed in the abutment chimney. Results: Only gaskets which sealed both the cross‐pin screw interface and the abutment‐crown interface prevented leakage. A filler placed in the abutment chimney prevented leakage into this space but did not prevent fluid accumulating between the coping and abutment. Conservative placement of cement at the margin of the coping failed to prevent leakage. Conclusions: Cement gaskets may effectively prevent leakage into a cross‐pinned ISR. However, the use of a cement as a gasket has to be weighed against the issue of predictable retrieval, cement extrusion and incomplete seating.     

Clinical performance of provisional screw‐retained metal‐free acrylic restorations in an immediate loading implant protocol: a 242 consecutive patients' report

Objective: To evaluate the clinical performance of provisional screw‐retained metal‐free acrylic restorations in an immediate loading implant protocol. Material and methods: Two hundred and forty‐two consecutive patients were selected retrospectively, who received 1011 implants and 311 immediate provisional screw‐retained implant restorations (2–4 h after implant surgery). The patients were monitored for a period of 2–3 months, until they were referred for a final restoration. The primary variables recorded include the survival time and the appearance of fractures in the provisional restoration, and the independent variables included age, sex, dental arch, type of restoration, type of attachment and components used, as well as cantilevers and opposing dentition. A survival analysis (Kaplan–Meier) and a Cox regression analysis were performed. Results: Twenty‐three restorations in 20 patients (8.26%, 95% CI 4.8–11.7) showed at least one fracture (7.39%). More than half of the new fractures (52%, 12 cases) occurred in the first 4 weeks. The cumulative survival probability observed was greater in mandible (P=0.05) and non‐cantilever restorations (P=0.001), and in those opposed by full restorations or natural teeth (P=0.001). With an opposing implant‐supported prosthesis, the risk of fracture was multiplied by 4.7, and the use of cantilevers as well as the location of the restoration in the maxilla multiply the risk by 3.4–3.5. Conclusions: Immediate provisional screw‐retained metal‐free implant‐supported restorations can be considered a reliable restoration (92.6% remain intact) for the healing period of 3 months. To cite this article:
Suarez‐Feito JM, Sicilia A, Angulo J, Banerji S, Cuesta I, Millar B. Clinical performance of provisional screw‐retained metal‐free acrylic restorations in an immediate loading implant protocol: a 242 consecutive patients' report.
Clin. Oral Impl. Res. 21 , 2010; 1360–1369.
doi: 10.1111/j.1600‐0501.2010.01956.x     

A Prosthesis Retention System for Full‐Arch,Fixed, Implant‐Supported Prosthesis

Full‐arch, fixed, implant‐supported prostheses can be designed to be cement‐ or screw‐retained. Both retention mechanisms have a few inherent disadvantages. A fixed attachment system has been introduced to circumvent the disadvantages of both screw and cement retention. This system eliminates the screw access holes and the use of cement. The number of intraoral procedures required is also reduced. The purpose of this article is to report a case using the Locator F‐Tx Attachment System to facilitate fabrication of an esthetic, clinician‐retrievable, full‐arch implant‐supported fixed dental prosthesis.     

Strategies for restoration of single implants and use of cross‐pin retained restorations by Australian prosthodontists

Background: Implant supported restorations (ISRs) for the single implant may be cement retained or screw retained. Limited scientific evidence exists to support the superiority of a retention type for either implant or prosthetic success. The aim of this study was to assess preferences of Australian prosthodontists when restoring single implants. In particular, clinical practices for cross‐pin retained implant supported restorations for a single implant were investigated. Methods: A written questionnaire comprised of seven questions, some of which had multiple parts and of both open‐ and closed‐format, was sent to 124 Australian prosthodontists. The questionnaire asked recipients to identify: (1) their preference for retention choice when restoring a single implant; (2) the frequency of use; and (3) clinical practice when restoring a cross‐pin retained restoration. Results: Seventy‐seven per cent of respondents indicated that direct to fixture (DTF) retention was their first preference. DTF retention was also the most frequently employed restoration for single implants. Respondents indicated that cross‐pinned ISRs are employed to maintain retrievability or when DTF is not possible. The majority of respondents indicated they always or sometimes use a gasket with cross‐pin retained restorations, though gasket type varied. Thirty‐eight respondents (31%) indicated that they would never use a cross‐pinned retained restoration for a single ISR. Conclusions: Australian prosthodontists prefer, and more frequently restore single implants, using DTF retention. Queensland prosthodontists prefer cement retained ISRs. In comparison, cross‐pinned restorations tend to be the least favoured and least used retention type. In addition, variation in opinion exists regarding the need for a gasket and type of gasket to be placed.     

Posterior resin composite restorations with or without resin‐modified,glass‐ionomer cement lining: a 1‐year randomized,clinical trial

Aim: To investigate the effect of resin‐modified, glass‐ionomer cement lining on the quality of posterior resin composite restorations, bonded with a two‐step, total‐etch or self‐etching adhesive, at 1 year. Methods: Patients with 1–4 moderate‐to‐deep, primary occlusal caries in molars were informed and recruited. A total of 110 composite restorations were placed in 75 participants, with one of four restorative procedures: (a) bonded with a total‐etch adhesive (Single Bond 2); (b) lined with glass‐ionomer cement (Fuji Lining LC), and then bonded with total‐etch adhesive; (c) bonded with a self‐etching adhesive (Clearfil SE Bond); and (d) lined with glass‐ionomer cement, and then bonded with self‐etching adhesive. Results: At 1 year, 57 patients (86 restorations) attended the recall. Each of the restorations was evaluated and scored from 1 (clinically excellent) to 5 (clinically poor) using the following criteria: (a) patient satisfaction; (b) fracture and retention; (c) marginal adaptation; (d) recurrent caries; and (e) post‐operative sensitivity. At 1 year, the qualities of the restorations were not significantly affected by the placement of glass‐ionomer cement lining, regardless of the adhesive used (P > 0.05). Most of the restorations were scored 1 for all criteria. Conclusions: The benefit of placing a glass‐ionomer cement liner in resin composite restoration is questionable.