Abutment Screw Fracture Research Articles

Prosthodontic Maintenance of Fixed Implant Restorations vs. Implant Overdentures: A Systematic Review

Objectives: To compare the prosthodontic maintenance requirements of fixed implant prosthesis versus that of implant overdentures after an observation period of at least 1year. Methods: An electronic search was performed using PubMed and Cochrane CENTRAL databases for articles published in English till the end of September 2015. Inclusion criteria were randomized controlled trials (RCTs) and prospective cohort studies (PS) which compared maintenance requirements of fixed versus removable implant supported full arch prostheses. Two reviewers independently screened titles and abstract, made data extraction and appraised the quality of included studies. Findings: From a total of 21 relevant studies identified, 2 RCTs and 6 PS fulfilled the inclusion criteria. The most common prosthetic complications affecting both types of prostheses were abutment screw loosening and fracture, prosthetic teeth fracture, frame work/bar fracture, acrylic resin denture base crack/fracture and denture remake. Most of the included studies were PS, and the RCTs were considered of high risk of bias accordingly there is no enough evidence to conclude that a group is superior over the other. Application/Improvements: To perform a true comparison, well designed RCTs should be held out. Besides, the evaluation of prosthodontic maintenance should be standardized between studies to come out with a definite conclusion..

Salvaging an Osseointergrated Implant after Abutment Screw Fracture- A Case Report

The rehabilitation of patients using implants supported prosthesis restores aesthetic and function and preserves the underlying periodontium .Common failure of the implant includes biological and mechanical failure. Biological failures include lack of osseointegration and peri-implantitis. Mechanical failure includes abutment screw loosening or fracture, crown loosening, crown fracture. The most common failure encountered in dental practice is the abutment screw loosening and fracture. Fracture of the implant abutment screw can be a serious problem as the fragment remaining inside the implant may prevent the implant from functioning efficiently. Retrieval of the screw is difficult if the screw fragment is below the neck of the implant and is very small. This case report outlines the management of abutment screw fracture with screw fragment being very small.

The applicability of PEEK-based abutment screws

The high-performance polymer PEEK (poly-ether-ether-ketone) is more and more being used in the field of dentistry, mainly for removable and fixed prostheses. In cases of screw-retained implant-supported reconstructions of PEEK, an abutment screw made of PEEK might be advantageous over a conventional metal screw due to its similar elasticity. Also in case of abutment screw fracture, a screw of PEEK could be removed more easily. M1.6-abutment screws of four different PEEK compounds were subjected to tensile tests to set their maximum tensile strengths in relation to an equivalent stress of 186MPa, which is aused by a tightening torque of 15Ncm.Two screw types were manufactured via injection molding and contained 15% short carbon fibers (sCF-15) and 40% (sCF-40), respectively. Two screw types were manufactured via milling and contained 20% TiO2 powder (TiO2-20) and >50% parallel orientated, continuous carbon fibers (cCF-50). A conventional abutments screw of Ti6Al4V (Ti; CAMLOG® abutment screw, CAMLOG, Wimsheim, Germany) served as control. The maximum tensile strength was 76.08±5.50MPa for TiO2-20, 152.67±15.83MPa for sCF-15, 157.29±20.11MPa for sCF-40 and 191.69±36.33MPa for cCF-50. The maximum tensile strength of the Ti-screws amounted 1196.29±21.4MPa. The results of the TiO2-20 and the Ti screws were significantly different from the results of the other samples, respectively. For the manufacturing of PEEK abutment screws, PEEK reinforced by >50% continuous carbon fibers would be the material of choice.

Prospective assessment of CAD/CAM zirconia abutment and lithium disilicate crown restorations: 2.4 year results

Statement of problemSingle-tooth implant restorations are commonly used to replace anterior maxillary teeth. The esthetic, functional, and biologic outcomes are, in part, a function of the abutment and crown. PurposeThe purpose of this clinical study was to describe the implant, abutment, and crown survival and complication rates for CAD/CAM zirconia abutment and lithium disilicate crown restorations for single-tooth implants. Material and methodsAs part of a broader prospective investigation that enrolled and treated 141 participants comparing tissue responses at the conical interface (CI; AstraTech OsseoSpeed), flat-to-flat interface (FI; NobelSpeedy), and platform-switch interface (PS; NanoTite Certain Prevail) of single-tooth implants, computer-aided design and computer-aided manufacturing (CAD/CAM) zirconia abutments (ATLANTIS Abutment) and cemented lithium disilicate (e.max) crowns were used in the restoration of all implants. After 2.4 years in function (3 years after implant placement), the implant, abutment, and crown of 110 participants were evaluated. Technical and biologic complications were recorded. Demographic results were tabulated as percentages with mean values and standard deviations. Abutment survival was calculated with the Kaplan-Meier method. ResultsAfter 2.4 years, no abutments or crowns had been lost. Abutment complications (screw loosening, screw fracture, fracture) were absent for all 3 implant groups. Crown complications were limited to 2 crowns debonding and 1 with excess cement (2.5%). Five biological complications (4.0%) were recorded. The overall complication rate was 6.5%. ConclusionsCAD/CAM zirconia abutments restored with cemented lithium disilicate crowns demonstrated high survival on 3 different implant-abutment interface designs. No abutment or abutment screw fracture occurred. The technical complications observed after 2.4 years were minor and reversible. The use of CAD/CAM zirconia abutments with cemented lithium disilicate crowns is associated with high technical and biologic success at 2.4 years.

Reliability and failure modes of narrow implant systems.

Narrow implants are indicated in areas of limited bone width or when grafting is nonviable. However, the reduction of implant diameter may compromise their performance. This study evaluated the reliability of several narrow implant systems under fatigue, after restored with single-unit crowns. Narrow implant systems were divided (n=18 each), as follows: Astra (ASC); BioHorizons (BSC); Straumann Roxolid (SNC), Intra-Lock (IMC), and Intra-Lock one-piece abutment (ILO). Maxillary central incisor crowns were cemented and subjected to step-stress accelerated life testing in water. Use level probability Weibull curves and reliability for a mission of 100,000 cycles at 130- and 180-N loads (90% two-sided confidence intervals) were calculated. Scanning electron microscopy was used for fractography. Reliability for 100,000 cycles at 130N was ∼99% in group ASC, ∼99% in BSC, ∼96% in SNC, ∼99% in IMC, and ∼100% in ILO. At 180N, reliability of ∼34% resulted for the ASC group, ∼91% for BSC, ∼53% for SNC, ∼70% for IMC, and ∼99% for ILO. Abutment screw fracture was the main failure mode for all groups. Reliability was not different between systems for 100,000 cycles at the 130-N load. A significant decrease was observed at the 180-N load for ASC, SNC, and IMC, whereas it was maintained for BSC and ILO. The investigated narrow implants presented mechanical performance under fatigue that suggests their safe use as single crowns in the anterior region.

A conservative approach to retrieve a fractured abutment screw – Case report

IntroductionRegarding implant-supported prostheses, the most reported types of complications are related to loosening or fracturing of abutment or prosthesis screws. This case report shows a series of procedures that allowed a conservative solution for a fractured screw. It avoided removing the implant and also allowed the same prosthesis to be used after guided-drilling the fractured screw and re-tapping the implant internal threads. The same prosthesis was replaced immediately after the procedure. PatientA 67-year-old male patient, who had a fractured abutment screw of the lower left first molar implant. The patient decided for the conservative treatment option and an attempt was made to remove the fractured screw. DiscussionParafunctional habits can generate excessive occlusal forces, which are risk factors associated with loosening and fracturing implant screws and even the fixtures themselves. This case report focus on the probable causes, difficulties and risks associated with this procedure and it also discusses the alternative approaches. ConclusionThe purposed treatment allowed a time and money saving resolution for fractured abutment screws.

Effect of morphology and diameter of implant fixture-abutment connection on mechanical failure of implants

Purpose: This study was conducted to evaluate the effect of the fixture abutment connection type and diameter on the screw joint stability in external butt joint for 2nd surgery and internal cone connected type implant system for 1st and 2nd surgery using ultimate fracture strength. Materials and Methods: USII system, SSII system and GSII system of Osstem Implant were used. Each system used the fixture with two different diameters and cement-retained abutments, and tungsten carbide / carbon coated abutment screws were used. Disc shaped stainless steel metal tube was attached using resin-based temporary cement. The experimental group was divided into seven subgroups, including the platform switching shaped specimen that uses a regular abutment in the fixture with a wide diameter in USII system. A static load was increased to the metal tube at 5mm deviated point from the implant central axis until it reached the compression bending strength at a rate of 1mm/min. Then the deformations and patterns of fracture in threaded connection were compared. Results and Conclusion: 1. In the comparison between the Regular diameter, compression bending strength of SSII system was higher than USII system and GSII system. There was no significant difference between USII system and GSII system. 2. In the comparison between wide diameter, compression bending strength was increased in the order of GSII system, USII system, and SSII system. 3. In comparison between the implant diameter, compression bending strength of the wide diameter was greater than the regular diameter in any system(P<0.05). 4. There was no significant difference between the platform switching (III group) and the regular diameter (I group) in USII system. 5. In USII system, fracture of abutment screw and deformation of both fixture and abutment were observed in I, II and III subgroups. 6. Failure pattern of SSII system, which was the fracture of abutment screw and deformation of the abutment and fixture, was observed in both IV and V subgroups. Fracture of some fixtures was observed in subgroup V. 7. Failure pattern of GSII system, which was the fracture of the abutment screw and deformation of the fixture and the abutment, was observed in both VI and VII subgroups. Apart from other subgroups, subgroup VII demonstrated no bending neither the fracture at the top of the fixture. The compressive deformation of internal slope in the fixture was the only thing observed in subgroup VII.

Mechanical Evaluation of Two Grades of Titanium Used in Implant Dentistry.

To investigate the effect of core dental implant materials supporting single crowns on the probability of survival and failure modes. Thirty-six standard external-hex titanium implants (4.0 mm in diameter) were selected to restore single crowns and divided into two groups according to core material: commercially pure grade 2 titanium (G2) and grade 5 titanium-aluminum-vanadium alloy (Ti-6Al-4V) (G5). Abutments were screwed to the implants, and standardized maxillary central incisor metal crowns were cemented and subjected to step-stress accelerated life testing in water. Use-level probability Weibull curves and reliability for missions of 100,000 cycles at 150 N and 200 N (with 90% two-sided confidence intervals [CIs]) were calculated. Polarized light and scanning electron microscopes were used to determine the failure modes. Use-level probability Weibull calculations showed beta values of 0.59 (CI, 0.31 to 1.11) and 1.22 (CI 0.81 to 1.84) for G2 and G5, respectively, and significantly higher characteristic strength and Weibull modulus for G5. The calculated reliability (90% CIs) for a mission of 100,000 cycles at 150 N showed that cumulative damage would lead to survival of 45% of implant-supported crowns of G2 and 98% of G5. At 200 N the probability of survival decreased to 0.03% for G2 and 21% for G5. Abutment screw fracture was the failure mode for all groups. Reliability, characteristic strength, and Weibull modulus were significantly higher for Ti-6Al-4V dental implants than for commercially pure (grade 2) titanium implants. Failure modes were similar for both groups.

Effect of Diamondlike Carbon Coating on Reliability of Implant-Supported Crowns.

To evaluate the effect of diamondlike carbon (DLC) coating on abutments and/or abutment screws on the reliability, characteristic strength, and Weibull modulus of implant-supported single crowns. Seventy-two external hexagon implants (Emfills Implant 4 mm diameter, 10 mm length, Emfills) were divided into four groups (n = 18 each), according to the presence or not of a DLC coating in the abutment and/or abutment screw, as follows: abutment without coating, screw without coating (AwcSwc); abutment without coating with coated screw (AwcSC); abutment coated with noncoated screw (ACSwc), and coated abutment with coated screw (ACSC). Abutments and screws were evaluated with scanning electron microscopy. The specimens were subjected to step-stress accelerated life testing in water. Use-level probability Weibull curves and reliability for a mission of 100,000 cycles at 150 N (90% two-sided confidence intervals) were calculated. Polarized light and scanning electron microscopes were used for fractographic analysis. For a mission of 100,000 cycles at 150 N, reliability was 0.45 (0.20 to 0.67), 0.12 (0.00 to 0.47), 0.56 (0.17 to 0.82), and 0.44 (0.07 to 0.77) for AwcSwc, AwcSC, ACSwc, and ACSC, respectively. The probability Weibull calculation showed a Weibull modulus (m) of m = 5.50, m = 11.64, m = 16.96, and m = 15.08 and the characteristic strengths (η, which indicates the load at which 63.2% of the specimens of each group fail) of η = 202.67 N, ŋ = 206.64 N, ŋ = 192.54 N, and ŋ = 203.59 N for AwcSwc, AwcSC, ACSwc, and ACSC, respectively. Abutment screw fracture was the chief failure outcome in all groups. Characteristic strength values were not different among groups; neither was reliability. However, an increase in Weibull modulus (indicating low variability of the results) was observed with DLC coating of abutment or screw or both.

Mechanical Complication Rates and Optimal Horizontal Distance of the Most Distally Positioned Implant-Supported Single Crowns in the Posterior Region: A Study with a Mean Follow-Up of 3 Years.

The purpose of this retrospective study was to determine the 3-year mechanical complication rates of the most distally positioned implant-supported single crowns (ISSCs) in the posterior region, and how these complication rates are affected by several clinical factors (i.e., gender, mean age, horizontal distance [HD], position in the jaw, placement location, duration of functional loading, clinical crown-to-implant length ratio [C/I ratio], and crown height space of the implant). The mechanical complications (i.e., abutment screw loosening [ASL], abutment screw fracture [ASF], and ceramic fracture [CF]) associated with the implants were identified by examining the patients' treatment records, clinical photographs, and intraoral periapical radiographs. Statistical analyses were performed using chi-square and Student's t-test to identify the relationship between various clinical factors and the mechanical complication rates. Receiver operating characteristics analysis was conducted to determine the optimal cut-off value for the HD between the most distally positioned ISSCs and the mesially adjacent natural tooth beyond which complications occur. The study inclusion criteria were met by 183 patients who had undergone implant surgery in the period 2004 to 2011, involving a total of 221 implant treatments. Mechanical complications were present in 40 (18.1%) of the 221 investigated ISSCs. ASL was the most common complication (n = 28, 12.7%), followed in order by CF (n = 9, 4.1%) and ASF (n = 3, 1.4%). Repeated ASL and CF occurred in four (1.8%) and two (0.9%) implants, respectively. The mechanical complication rates differed significantly between implants with different HDs (p = 0.009) and clinical C/I ratios (p = 0.019); however, there was no significant association between the other clinical factors and the mechanical complication rates. Within the limitations of this study, it appears that the incidence of mechanical complications is higher for the most distally positioned ISSCs in the posterior region than for those positioned at other sites. Furthermore, since the rate of mechanical complications increases with increasing HD, an HD of 3.7 mm or less is recommended.

インプラントのチタン製アバットメントスクリューの破折危険因子に関する検討

チタン合金製アバットメントスクリュー破折の原因および物理的因子や環境因子について検討した．破折したアバットメントスクリュー破断面の走査型電子顕微鏡（SEM）画像の観察，三次元有限要素法による応力解析，および口腔内類似環境下において腐食反応実験を行った．アバットメントスクリューの破断面には，腐食孔と疲労破壊の様相が認められ，表面にS などの付着物が検出された．三次元有限要素法では，インプラントの上部構造物辺縁隆線部に垂直方向へ応力を負荷させた場合に，破折部位と同一部位に応力集中が認められた．また，腐食試験では，チタン合金板（Ti-6Al-4V）に応力を負荷し，37℃の硫酸ナトリウム（Na2SO4）水溶液，生理食塩水，無負荷板を Na2SO4 水溶液に浸漬した．浸漬期間は1 週間，2 週間，3 週間，4 週間とした．その後，SEM 観察とエネルギー分 散型エックス線分析（EDS）による元素分析を行ったが，すべての試験片で孔食などの腐食所見は見られなかった．破折の原因は，腐食環境下にて，腐食孔を起点とした疲労破壊と考えられるが，孔食の原因は特定できなかった．

New 3D technologies applied to assess the long-term clinical effects of misfit of the full jaw fixed prosthesis on dental implants.

To assess implant:suprastructure misfit in patients with an edentulous jaw restored by an implant-retained fixed dental prosthesis (FDP) and its association with biologic and mechanical adverse events over an extensive period. Thirty patients with an edentulous mandible treated with implant-supported prosthetics before 2000 were examined clinically in 2012. Each patient had received 4 to 6 implants to retain a FDP made from acrylic and three different metal alloys, that is, Ag-Pd, Pd-Ag, and Au type IV. The implant intra-oral locations were recorded digitally by use of an intra-oral scanner, and the intaglio surface of the detached FDP was recorded using a desktop scanner. The fit was estimated by digital matching of the STL files using industrial metrological software. The average misfit was correlated with the average marginal bone loss and the prevalence of screw loosening or fractures, using the patient as the statistical unit. Over an average of 19years (range 12 to 32), 5 implants had been lost in 4 participants (96.7% implant survival) and 8 eight prostheses (26.7%) had been remade. Anaverage misfit was 150μm (SD 35, range 95-232, CI 138-163). An average marginal bone loss of 2.2mm (SD=0.7) had occurred (range 0.6 to 5.8mm) for individual implants. The correlation between framework misfit and marginal bone loss was weak (R²=0.04) (P=0.29). The prostheses with a history of screw-related adverse events showed average misfit of 169μm (SD=32) vs. those with no history of screw-related adverse events, that is, 134μm (SD=30) (P=0.005, Student's t-test). Fourteen of the 30 participants had experienced at least one incidence of screw loosening or fracture of prosthetic or abutment screw(s) over the period of follow-up. The occurrence among the frameworks fabricated with different metal alloys did not differ (P>0.05, Fisher's exact test). Combining STL files with best-fit algorithms to appraise misfit is feasible using metrological software. The effect of misfit between the superstructures on its supporting implants up to ~230μm on the long-term clinical outcomes appears to be minor, apart from a slightly higher risk of screw-related adverse events.

다수의 임플란트발거로 임플란트 고정성 보철이 실패한 환자에서의 잔존 임플란트를 이용한 부분 가철성 국소의치 수복증례

부분 무치악을 수복하는 데 있어서 선택할 수 있는 치료의 옵션으로는 전통적인 국소의치와 임플란트 지지-고정성 보철물 등이 있다. 하지만, 환자의 전신적 또는 구강의 상태(수술적인 술식이 제한되는 전신병력, 지지조직의 부족 그리고 골유착에 실패한 임플란트)와 치료비용에 대한 허용 정도에 따라 모든 옵션이 항상 가능한 것은 아니다. 가철성 국소의치는 임플란트 고정성 보철물에 비해 구강위생 관리 및 상,하악 악간관계의 부조화를 수정하기에 편리한 장점이 있다. 최근에는 전략적 위치에 임플란트를 식립하여 기존 악궁 형태에서는 제한되는 국소의치 디자인의 한계를 개선할 수 있는 임플란트지지형 RPD(Implant Supported Removable Partial Denture)가 새로운 방안으로 대두되고 있다. ISRPD는 전략적 위치에 임플란트를 식립하여 역학적인 한계를 극복할 수 있을 뿐 만 아니라 전악의 임플란트지지형 고정성 보철이 제한되는 환자에서 보다 경제적이고 현실적인 보철적 해결책이 될 수 있다. 따라서, RPD를 이용한 보철계획 수립시 전략적 위치에서의 임플란트의 사용은 고전적인 가철성 국소 의치에서보다 유지력과 안정성을 증진시키고 구강위생관리 또한 용이하여 환자의 적응도를 높이는 방안으로 고려될 수 있다. 본 증례는 상악 양측 구치부의 임플란트 고정성 보철,하악의 bar-type overdenture를 사용중이던 59세 남성환자에서 상악 #15i임플란트의 abutment screw fracture와 임플란트의 골유착 실패로 인한 다수 임플란트를 발거 후 남은 #15i,24i,25,26,i의 잔존 임플란트와 #23 자연치를 활용해 상악에 ISRPD를 적용한 경우이다. #23 surveyed crown, #24i=25i=26i surveyed bridge 및 #15i에 gold coping을 제작하여 국소의치의 지지와 유지,안정을 도모하였다.최종 보철물을 장착하고 2년간 주기적인 follow up 통해 예후를 관찰중이며 지대치로 사용한 임플란트에서 screw loosening이나 파절, 골흡수 등의 증상은 현재까지 관찰되지 않았다. There are several treatment options for rehabilitation of partial edentulism including the use of conventional or implant-retained fixed prostheses. However, such prosthetic options cannot always be possible because of compromised general and oral health (i.e. loss of supporting tissues, medical reasons, extensive surgical protocol and osseointegration failure of dental implant) as well as the affordability of patients. In some cases, removable partial denture provides easier access for oral hygiene procedures and the ability to correct discrepancies in dental arch relationships than implant fixed prosthesis. Recently, Implant Supported Removable Partial Denture (ISRPD) where to place dental implant in strategic position has been suggested to improve the limitation and shortcomings of conventional RPD. ISPRD can overcome mechanical limition of conventional RPD by placing implant in a favorable position and can be cost-effective, prosthetic solution for partially edentulous patients who are not immediate candidates for extensive, fixed implant supported restorations. Incorporation of dental implants to improve the RPD support and retention and to enhance patient acceptance should be considered when treatment planning for RPD. In this case, 59 years old male patient who received dental treatment of implant fixed prosthesis on both side of the upper jaw and implant overdenture on lower jaw showed implant abutment screw fracture on #15i and osseointegration failure on multiple number of implants. After removing failed implants, we planned ISRPD using #15i,24i,25i,26i and #23 natural tooth for RPD abutment. We fabricated #23 surveyed crown,#24i=25i=26i surveyed bridge and #15i gold coping for support,retention and stability for RPD. Periodic follow up check for 2years has been performed since the ISRPD delivery to the patient. No sign of screw loosening, fracture or bone resorption around abutment implants were detected.

Management of a Fractured Implant Abutment Screw: A Clinical Report

In an abutment screw fracture, it is generally a challenge for the clinician to remove fractured fragments. In some cases, the screw cannot be removed, and alternative solutions should be considered. This clinical report describes the replacement of a ball attachment with a fractured screw, which was impossible to retrieve, with a cast dowel with ball attachment. The patient who presented to the Department of Prosthodontics, Yeditepe University, Faculty of Dentistry was a 65-year-old woman, wearing a mandibular complete denture supported by two implants for 4 years. She complained about the loss of retention of the denture because of the fractured abutment screw, and it was found that another dentist had previously tried to retrieve the fractured screw with no success. It was decided to construct a cast dowel with ball attachment to improve retention without sacrificing the implant. The interior of the implant and the fractured screw were machined with a rotating instrument. An impression was taken with a metal strip and silicone-based materials. In the laboratory, a stone die was generated from the impression, and a custom-made cast dowel with ball attachment was constructed. It was then cemented with glass ionomer cement and connected to the denture with the direct method. The alternative procedure described in this clinical report was successful for the removal of the fractured abutment screw and use of the existing denture.

Mechanical Testing of Implant-Supported Anterior Crowns with Different Implant/Abutment Connections

This study evaluated the reliability and failure modes of anterior implants with internal-hexagon (IH), external-hexagon (EH), or Morse taper (MT) implant-abutment interface designs. The postulated hypothesis was that the different implant-abutment connections would result in different reliability and failure modes when subjected to step-stress accelerated life testing (SSALT) in water. Sixty-three dental implants (4 × 10 mm) were divided into three groups (n = 21 each) according to connection type: EH, IH, or MT. Commercially pure titanium abutments were screwed to the implants, and standardized maxillary central incisor metallic crowns were cemented and subjected to SSALT in water. The probability of failure versus number of cycles (95% two-sided confidence intervals) was calculated and plotted using a power-law relationship for damage accumulation. Reliability for a mission of 50,000 cycles at 150 N (90% two-sided confidence intervals) was calculated. Polarized-light and scanning electron microscopes were used for failure analyses. The beta values (confidence intervals) derived from use-level probability Weibull calculation were 3.34 (2.22 to 5.00), 1.72 (1.14 to 2.58), and 1.05 (0.60 to 1.83) for groups EH, IH, and MT, respectively, indicating that fatigue was an accelerating factor for all groups. Reliability was significantly different between groups: 99% for MT, 96% for IH, and 31% for EH. Failure modes differed; EH presented abutment screw fracture, IH showed abutment screw and implant fractures, and MT displayed abutment and abutment screw bending or fracture. The postulated hypothesis that different implant-abutment connections to support anterior single-unit replacements would result in different reliability and failure modes when subjected to SSALT was accepted.

A Technique Elucidating the Retrieval of an Adhered Cover Screw in a Dental Implant – A Case Report

Dental implants have become one of the most popular and rapidly growing techniques for replacing missing teeth. While their predictability, functionality, and durability make them an attractive option for patients and clinicians alike, complications can arise at any stage from patient assessment to maintenance of therapy. Failure of dental implants not only occurs due to biological factors, like unsuccessful osseointegration or peri-implantitis but may also occur due to technical complications like, failures of implant-supported restorations relating those from the implant components, and those relating to the prosthesis. Technical problems related to implant components include abutment screw fractures and cover screw fractures. In this case report we have elucidated an adhered cover screw in an implant.

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.

A NEW RESTORATIVE TECHNIQUE FOR THE PERISHING IMPLANT DUE TO ABUTMENT SCREW FRACTURE

Abstract Abutment screw fracture, although uncommon, occurs in clinical practice. In many cases, the fractured end can be retrieved and replaced by a new abutment screw. However, sometimes the screw cannot be removed conservatively. By using rotary instruments, internal threads of the screw hole may be damaged and the implant rendered useless. To overcome these problems, this article presents a technique of converting the screw chamber into post space and rehabilitating with the new crown over this post and core system.

Systematic review of the survival rate and the biological, technical, and aesthetic complications of fixed dental prostheses with cantilevers on implants reported in longitudinal studies with a mean of 5 years follow‐up

A systematic review was carried out to evaluate the success and survival rate of implants supporting cantilever prosthesis, as well as the incidence of technical and biological complications. A MEDLINE search was conducted up to December 2011 for studies with a mean follow-up of 5 years or more. Two independent reviewers screened the retrieved articles and extracted the data independently. Data on survival, failure, mechanical/technical and biological complications were analyzed. One-hundred and sixty articles were selected as abstract. Only 18 underwent a full-text analysis and only six were included in the study. The estimated cumulative survival rate of implants supporting cantilevered prosthesis was 98.9% (95% CI: 97.4-99.5%), whereas ICFDP survival was estimated to be about 97.1% (95% CI: 90.1-99.2%). Implant failures before prosthetic delivery were not considered. Biological complications were estimated to be 5.7% (95% CI: 4.2-7.6%) at implant level after 5 years. Technical complications were analyzed: the most common complications were veneer fractures (5-year estimate: 10.1%; 95% CI: 3.7-16.5%) and abutment screw fractures (5-year estimate: 1.6%; 95% CI: 0.8-3.5%). Decementation and screw loosening were estimated to be at 5 years 5.9% (95% CI: 1.7-16.8%) and 7.9% (95% CI: 3.2-18.2%), respectively. Implant fracture was rare (5-year estimate: 0.7%; 95% CI: 0.1-4.7%); no framework fracture was reported. Radiographic bone level changes did not yield statistically significant differences. No aesthetic outcome was reported. ICFDPS can be considered a reliable treatment: the systematic review assessed that there is no increase in complication rate due to the presence of the cantilever.

Effect of microthread presence and restoration design (screw versus cemented) in dental implant reliability and failure modes

This study evaluated the reliability and failure modes of implants with a microthreaded or smooth design at the crestal region, restored with screwed or cemented crowns. The postulated null hypothesis was that the presence of microthreads in the implant cervical region would not result in different reliability and strength to failure than smooth design, regardless of fixation method, when subjected to step-stress accelerated life-testing (SSALT) in water. Eighty four dental implants (3.3×10mm) were divided into four groups (n=21) according to implant macrogeometric design at the crestal region and crown fixation method: Microthreads Screwed (MS); Smooth Screwed (SS); Microthreads Cemented (MC), and Smooth Cemented (SC). The abutments were torqued to the implants and standardized maxillary central incisor metallic crowns were cemented (MC, SC) or screwed (MS, SS) and subjected to SSALT in water. The probability of failure versus cycles (90% two-sided confidence intervals) was calculated and plotted using a power law relationship for damage accumulation. Reliability for a mission of 50,000 cycles at 150N (90% 2-sided confidence intervals) was calculated. Differences between final failure loads during fatigue for each group were assessed by Kruskal-Wallis along with Benferroni's post hoc tests. Polarized-light and scanning electron microscopes were used for failure analyses. The Beta (β) value (confidence interval range) derived from use level probability Weibull calculation of 1.30 (0.76-2.22), 1.17 (0.70-1.96), 1.12 (0.71-1.76), and 0.52 (0.30-0.89) for groups MC, SC, MS, and SS respectively, indicated that fatigue was an accelerating factor for all groups, except for SS. The calculated reliability was higher for SC (99%) compared to MC (87%). No difference was observed between screwed restorations (MS - 29%, SS - 43%). Failure involved abutment screw fracture for all groups. The cemented groups (MC, SC) presented more abutment and implant fractures. Significantly higher load to fracture values were observed for SC and MC relative to MS and SS (P<0.001). Since reliability and strength to failure was higher for SC than for MC, our postulated null hypothesis was rejected.