2.1.1Proceedings of the 4th ITI Consensus Conference 2008
International Journal of Oral and Maxillofacial Implants 2009, Vol. 24 (Supplement): Consensus statements and recommended clinical procedures regarding risk factors in implant therapy (Cochran and coworkers 2009)
Introductory remarks
The group was asked to address the available evidence for potential risk factors in implant therapy. The authors were requested to prepare narrative reviews using a systematic approach, and were provided with general topics rather than specific research questions. The four reviews presented for discussion within the group addressed: (1) systemic conditions and treatments as risks for implant therapy, (2) history of treated periodontitis and smoking as risks for implant therapy, (3) mechanical and technical risks in implant therapy, and (4) local risk factors for implant therapy. The group’s participants critically reviewed each of the review papers produced by its members, and amendments were made following thorough discussion.
Systemic conditions and treatments
Clinical recommendations
With respect to systemic conditions and treatments as risk factors for implant therapy, the following recommendations can be made:
•A thorough medical history is essential to identify potential systemic risks.
•Risks for implant failure and risks for medical complications should be differentiated and evaluated. In some instances, conditions and their treatments may pose increased risks for implant failure, whereas the risk for the patient may be minimal. As an example, there are no data to support withholding implant treatment for patients with diabetes or osteoporosis. However, these patients need to be informed of the possibility of implant complications.
•Where there is a potential risk of a medical complication—for example, osteonecrosis of the jaw in patients taking oral bisphosphonates and patients undergoing radiotherapy—the option of implant therapy should be chosen restrictively, and the patient should be informed specifically, taking into account the current level of uncertainty with regard to the consequences. For patients with a life-threatening systemic disease, implant placement should be postponed until the patient’s medical condition is stabilized and has improved.
History of treated periodontitis and smoking
Clinical recommendations
With respect to a history of treated periodontitis and smoking, the following recommendations can be made:
•History of treated periodontitis. A history of treated periodontitis is not a contraindication for implant placement. However, patients with a history of treated periodontitis should be informed of an increased risk of implant failure and peri-implantitis. Patients with a history of periodontitis should receive individualized periodontal maintenance and regular monitoring of peri-implant tissue conditions.
•Smoking. Smoking is not a contraindication for implant placement. However, patients should be informed that the survival and success rates are lower in smokers. Heavy smokers should be informed that they are at greater risk of implant failure and loss of marginal bone. Patients who smoke should be informed that there is an increased risk of implant failure when sinus augmentation procedures are used.
•History of treated periodontitis and smoking combined. Patients who smoke and have a history of treated periodontitis should be informed that they have an increased risk of implant failure and peri-implant bone loss.
Mechanical and technical risks
Clinical recommendations
With respect to mechanical/technical risks, the following recommendations can be made:
•In general, implant reconstructions should be planned to minimize mechanical/technical risks.
•Patients receiving implant therapy should receive regular maintenance care in order to detect mechanical/technical complications early, particularly in patients with overdentures.
•Both cemented and screw-retained implant-supported reconstructions can be recommended.
•Patients should be evaluated for bruxism.
Local risk factors
Clinical recommendations
With respect to local risk factors, the following recommendation can be made:
•Special care should be taken in selection of implant diameter and design in areas with limited interdental space.
2.1.2Proceedings of the 5th ITI Consensus Conference 2013
International Journal of Oral and Maxillofacial Implants 2014, Vol. 29 (Supplement): Consensus statements and clinical recommendations for prevention and management of biologic and technical implant complications (Heitz-Mayfield and coworkers 2014)
Introductory remarks
Implant treatment is highly successful, as documented in a wealth of scientific literature. However, patients and clinicians should expect to see complications within their daily practice. The aim of the papers presented by this group was to address the prevention and management of technical and biologic complications in order to make recommendations both for clinical practice and future research. Three topics were chosen within the field of complications of implant treatment, and these addressed prevention and therapy of peri-implant disease and prevention of technical complications.
Three systematic reviews were conducted and formed the basis for discussion of working group 5. The discussions led to the development of statements and recommendations determined by group consensus based on the findings of the systematic reviews. These were then presented and accepted following modifications as necessary at plenary sessions.
Effects of anti-infective preventive measures on biologic implant complications and implant loss
Consensus statements
The aim of the review by Salvi and Zitzmann (2014) was to systematically appraise whether anti-infective protocols are effective in preventing biologic implant complications and implant loss after a mean observation period of at least ten years following delivery of the prosthesis. Out of fifteen included studies, only one comparative study assessed the effects of adherence to supportive periodontal therapy (SPT) on the occurrence of biological complications and implant loss. In view of the lack of randomized trails, observational studies including adherence and lack of adherence to SPT were considered valuable in order to estimate the effects of SPT on implant longevity and the occurrence of biological complications.
•Overall, the outcomes of this systematic review indicated that high long-term survival and success rates of dental implants can be achieved in partially and fully edentulous patients adhering to supportive periodontal therapy (SPT).
•Long-term implant survival and success rates are lower in patients with a history of periodontal disease adhering to SPT compared with those without a history of periodontal disease.
•The findings of this systematic review indicate that pre-existing peri-implant mucositis in conjunction with lack of adherence to SPT was associated with a higher incidence of peri-implantitis.
Treatment guidelines
Preventive measures before implant placement
•Residual periodontal pockets are a risk for peri-implant disease and implant loss. Therefore, completion of active periodontal therapy aiming for elimination of residual pockets with bleeding on probing should precede implant placement in periodontally compromised patients.
•In cases of residual probing depths (PD) ≥ 5 mm with concomitant bleeding on probing, full-mouth plaque scores > 20%, and associated risk factors, re-treatment and periodontal reevaluation are recommended before implant placement.
•In subjects diagnosed with aggressive periodontitis, an SPT program with shorter intervals is a prerequisite.
•During implant treatment planning, factors to be considered that may result in biological complications include: insufficient keratinized mucosa and bone volume at the implant recipient site, implant proximity, three-dimensional implant position, and design and cleansability of the prosthesis. Alternative restorative solutions should be considered according to a patient’s individual circumstances.
Preventive measures after implant placement
•All oral healthcare providers, including undergraduate students, should be trained to recognize clinical signs of peri-implant pathology and maintain or reestablish peri-implant health.
•After delivery of the definitive implant-supported prosthesis, clinical and radiographic baseline measurements should be established.
•During SPT, an update of medical and dental history and a clinical inspection of the implant-supported prosthesis including the evaluation of iatrogenic factors (e.g. cement remnants, misfit of prosthesis, implant proximity with insufficient access for interproximal oral hygiene) should constitute the basis of a proper diagnostic process.
•Regular diagnostic monitoring of the peri-implant tissues includes assessment of presence of plaque, probing depth (PD), bleeding on gentle probing (approx. 0.25 N), and/or suppuration.
•Changes in PD from a fixed landmark should be assessed regularly and compared to previous examinations.
•In the presence of clinical signs of disease, an appropriate radiograph is indicated in order to detect radiographic bone-level changes compared to previous examinations.
•A diagnosis of peri-implant health is given in the absence of clinical signs of inflammation. A recall frequency of at least once per year is recommended unless systemic and/or local conditions require more frequent intervals. In cases of peri-implant health, professional cleaning including reinforcement of self-performed oral hygiene is recommended as a preventive measure.
•A diagnosis of peri-implant mucositis is given in the presence of individual clinical signs of soft tissue inflammation (e.g. redness, edema, suppuration) and bleeding on gentle probing. If mucositis is diagnosed, in addition to reinforcement of self-performed oral hygiene, mechanical debridement with or without antiseptics (e.g. chlorhexidine) is delivered. The use of systemic antibiotics for the treatment of peri-implant mucositis is not justified. Therapy of peri-implant mucositis should be considered as a preventive measure for the onset of peri-implantitis.
•A diagnosis of peri-implantitis is given in the presence of mucositis in conjunction with progressive crestal bone loss. When peri-implantitis is diagnosed, early implementation of appropriate therapy is recommended to prevent further progression of the disease.
Therapy of peri-implantitis
Consensus statements
The focused question for the review by Heitz-Mayfield and Mombelli (2014) was: In patients with osseointegrated implants diagnosed with peri-implantitis, how successful is treatment aimed at resolution of the disease?
Currently, there is no standard of care for treating peri-implantitis. Various clinical protocols for treating peri-implantitis have been proposed, including mechanical debridement, the use of antiseptics and local and systemic antibiotics, as well as surgical and regenerative procedures. In view of the lack of comparable randomized controlled trials (RCTs), this review has taken a broader approach to capture as many relevant studies as possible, including randomized and observational studies, but with consideration to the strengths and limitations of the included research.
The ideal goal of the treatment of peri-implantitis would be the resolution of disease, i.e. no suppuration or bleeding on probing, no further bone loss, and the re-establishment and maintenance of healthy peri-implant tissues. A composite outcome to reflect this would include absence of peri-implant PD ≥ 5 mm with concomitant bleeding on probing and no suppuration, in addition to no further bone loss. If these criteria are met, it can be assumed that no further intervention other than nonsurgical maintenance care would be required, and the treatment outcome would therefore be regarded as successful. Unfortunately these data were rarely reported in the literature and therefore a compromise composite criterion for successful treatment outcome was employed, i.e. implant survival with mean PD < 5 mm and no further bone loss. Although there is no consensus in the literature on whether a 5-mm peri-implant PD alone represents health or disease, this threshold was adopted for the purposes of the review. This review was based on 33 studies reported in 43 papers including case-series of at least 5 patients treated with the same protocol and comparative studies. No studies were found comparing surgical and nonsurgical protocols. Based on this literature, the following conclusions were drawn:
1.The case definition of peri-implantitis remains unclear and varies substantially between studies.
2.There is a great variety of treatment protocols for both nonsurgical and surgical treatment.
a.Nonsurgical therapy included: debridement with hand and powered instruments, air-powder abrasive devices, laser treatment, and local and systemic antimicrobial agents.
b.Surgical therapy included: elevation of a mucoperiosteal flap and removal of granulation tissue to gain access to the implant and defect surfaces, decontamination of the implant surface (various techniques) with or without implant surface modification. Some studies also evaluated resective therapy or a variety of regenerative procedures. The majority of the studies employed systemic antimicrobial administration.
3.The following elements are common to most protocols for peri-implantitis therapy:
a.Pretreatment phase including establishment of good oral hygiene.
b.Anti-infective treatment including implant surface cleaning achieved by nonsurgical/surgical access.
c.Supportive maintenance care.
4.The available evidence does not allow recommendation of specific treatment options for peri-implantitis. However, improvement of clinical parameters was reported for the majority of patients, although complete resolution according to a composite success criterion was not usually achieved for all patients. Favorable short-term outcomes were reported in many studies; however, lack of disease resolution as well as progression or recurrence of disease and implant loss, despite treatment, were also reported.
5.Interpretation of the results of studies is complicated by unclear or high risk of bias, heterogeneity of study design, and difficulty of generalizing outcomes to practice settings due to frequent exclusion of patients who smoke, those with poorly controlled diabetes, and other conditions that may affect clinical outcomes.
6.There are no data investigating patient-reported outcomes and economic analysis of therapy.
7.Peri-implantitis therapy was associated with soft-tissue recession, which was most evident following surgical treatment. Postsurgery complications including membrane exposure and infection were also reported.
Treatment guidelines
1.As peri-implantitis is an infection associated with the presence of a submucosal bacterial biofilm around implants, the primary goal of therapy must be the resolution of the infection, which is achieved by the disruption of the biofilm, the removal of calculus and/or overhanging restoration margins, and the prevention of recurrence of the disease.
2.It is important to try to establish if iatrogenic or other factors have contributed to the infection, for example ill-fitting or noncleansable overcontoured prostheses, malpositioned implants, or foreign bodies such as impression material or excess luting cement. Noniatrogenic factors may include impacted dental floss.
3.The following sequence of treatment of peri-implantitis is normally recommended.
a.Pretreatment phase including:
i.Thorough assessment and diagnosis.
ii.Reduction of risk factors for peri-implantitis; in particular poor oral hygiene, prostheses that prevent adequate access for plaque control, tobacco use, presence of periodontal diseases, and systemic diseases that may predispose to peri-implant disease.
iii.If required, prosthesis removal and adjustment/replacement.
b.Nonsurgical debridement focused on maximal removal of biofilm, with or without antimicrobials.
c.Early reassessment of peri-implant heath; normally within one to two months
d.Surgical access if resolution of peri-implantitis has not been achieved. This should include:
i.Full-thickness mucoperiosteal flaps and removal of granulation tissue to allow thorough cleaning of the implant surface.
ii.Thorough surface decontamination of the implant and restorative components. The following techniques have been proposed: locally applied chemicals, gauze soaked with saline or antiseptics, hand-powered instruments, air-powder abrasives, Er-YAG lasers, photodynamic therapy, and implant surface modification. There is no evidence for the superiority of any one approach.
iii.Surgical therapy might also include regenerative or resective approaches:
1.Regenerative approaches include filling of the intraosseous peri-implant defect with a bone substitute/graft/bioactive substance with or without a resorbable barrier membrane. Defect morphology for regeneration would normally require a contained defect. Submerged healing might reduce the risk of membrane exposure. Re-establishment of osseointegration following treatment has not been demonstrated in humans.
2.Resective approaches include osseous recontouring with apical positioning of the flap.
iv.Immediate postoperative anti-infective protocol should include daily chlorhexidine rinsing during the healing period until mechanical oral hygiene can be resumed. In the absence of evidence comparing surgical treatment with or without antibiotics, peri- or postoperative systemic antibiotics are recommended in view of the aggressive nature of disease. Professional support of healing and plaque control will be needed during this phase.
e.Clinical monitoring should be performed on a regular basis and supplemented by appropriate radiographic evaluation as required. Supportive maintenance therapy including reinforcement of effective oral hygiene and professional biofilm removal should be provided on a frequency determined by oral health and the risk profile, likely to be between every three to six months.
4.Surgical access is likely to be needed for the majority of deep lesions due to the difficulty of accessing the threads and surfaces of the implant.
5.The patient should be advised that:
a.Recession of the peri-implant mucosa should be expected following peri-implantitis treatment, in particular after surgical therapy.
b.Progression or recurrence of disease might require additional therapy or implant removal.
6.The clinician should consider implant removal as a treatment option. Factors influencing this decision may include the severity of the peri-implantitis lesion, the position of the implant, the surrounding tissues, or when the treatment outcomes are likely to be unsatisfactory.
7.Referral to specialist care for non-responding peri-implantitis should be considered.
8.Regular assessment of peri-implant health is recommended during SPT to identify disease at an early stage.
9.Training of dental team professionals should include diagnosis and management of peri-implant disease.
Survival rates of implant-supported fixed prostheses over the last decades
Consensus statements
The systematic review by Pjetursson and coworkers (2014) was conducted to compare the survival and complication rates of implant-supported prostheses published up to the year 2000 with those reported in studies published after the year 2000. An association between period of publication and fixed implant-supported prosthesis outcomes was found with higher survival rates and overall lower rates of mechanical and technical complication reported in more recent clinical studies. However, the incidence of reported technical complications is still high. The difference in survival rates are most evident for screw-retained prostheses, where the reported survival rate of 77.6% in the older publications was increased to 96.8% in the more recent ones.
Treatment Guidelines
Risk of fracture—implants
1.Implant fracture is a rare complication. To avoid implant fracture it is recommended that clinicians consider the use of appropriately designed and manufactured implants with properly investigated and documented low fracture rates. Similarly, the clinician should use implants manufactured from materials that have been thoroughly investigated.
2.The risk of implant fracture can be considered extremely low when:
a.The appropriate distribution, number, and diameter of implants are used.
b.Implants are placed using a restoratively driven protocol.
c.Implants are combined with an adequately fitting prosthesis
Risk of fracture and/or loosening—prosthetic screws
Fracture of manufacturer screws made to specified tolerances can be influenced by three factors: mishandling, misfit, and occlusal forces.
1.Mishandling: To reduce the risk of fracture of prosthetic screws, it is recommended that a clinician follow the manufacturer’s instructions for use.
2.Misfit: An inadequately fitting framework may be a predisposing factor to prosthetic screw fracture or loosening. It is recommended to prioritize evaluation of the accuracy of the interface between the machined head of the screw and its seating surface over the entire area of contact to reduce the risk of loosening and fracture.
3.Occlusal forces, usually in the presence of other predisposing factors, misfit, and mishandling, may lead to prosthetic screw fracture or loosening.
Risk of fracture and/or loosening—abutments
1.It is recommended that the clinician carefully evaluate the differential etiology of screw loosening, as the literature does not differentiate sufficiently between abutment or prosthetic screw loosening to conclude which type of screw is more likely to loosen.
2.Metal abutment fracture is a rare complication. Greater caution is advised with ceramic abutments. It is recommended that the specific material-based requirements of ceramics should be respected when choosing, designing, and handling these abutments.
Risk of fracture of framework and/or veneering materials
1.Currently framework fracture is a rare complication. The choice of material, appropriate design, and method of fabrication are all factors in reducing the risk of framework fracture.
2.To reduce the risk of fracturing the veneering materials, the framework must provide adequate support for the veneering ceramic or resin in order to avoid excessive thickness of the veneering material.
3.When choosing the material and determining framework design, it is recommended that the final contour of the definitive prosthesis be visualized prior to framework fabrication.
4.Scheduled regular maintenance appointments should include a careful occlusal review. It is recommended that clinicians undertake any required adjustments to the prosthesis, inclusive of meticulous polishing of worn ceramic surfaces, to reduce the risk of fracturing of the veneer material.
Quality assurance
It is recommended that clinicians, technicians, and manufacturers employ a tracking system for implants and restorative components. Clinicians should be aware that not all implant systems have the same level of documentation. The clinician should be aware of the origin of the components used.
2.2Literature Review:
Biological Complications
L. J. A. Heitz-Mayfield
In earlier longitudinal studies reporting on outcomes of implant-supported prostheses, the focus was predominately on implant survival. In many publications, information regarding the occurrence and nature of both technical and biological complications associated with the implant or the prosthesis was not reported (Berglundh and coworkers 2002).
In 2002, Berglundh and coworkers published the first systematic review addressing the incidence of biological and technical complications in implant dentistry, reporting on prospective longitudinal studies of at least a five-year duration. They included 51 studies in a meta-analysis, and reported a higher incidence of soft tissue complications for patients treated with implants supporting overdentures than for fixed prostheses. They found that most studies reported only on implant loss, while biological complications were considered in only 40% to 60% of the studies and technical (hardware) complications in only 60% to 80% of the studies. The authors concluded that the incidence of biological and technical complications was likely underestimated.
Furthermore, where reported, biological complications associated with osseointegrated dental implants were described using a wide range of terms including; implant loss, peri-implantitis, bone loss, soft-tissue hyperplasia, mucosal overgrowth, and soft-tissue complications. The inconsistencies in the terminology used have made it difficult to interpret data from these studies relating to the incidence or prevalence of these complications.
Pjetursson and coworkers as well as other authors have published a series of systematic reviews focusing on the survival and complication rates of implant-supported prostheses after an observation period of at least five years (Pjetursson and coworkers 2004; Jung and coworkers 2008; Aglietta and coworkers 2009; Pjetursson and coworkers 2012; Pjetursson and coworkers 2014). These systematic reviews indicate that hardware complications occur approximately three to four times more frequently than biological complications. When evaluating implant-supported fixed partial dentures, 8.6% (95% CI: 5.1%–14.1%) of them had had a biological complication after five years (Pjetursson and coworkers 2004). Jung and coworkers (2008) evaluated the biological complication rate of implant-supported single crowns in longitudinal studies with a mean follow-up of five years and found a five-year cumulative soft-tissue complication rate of 7.1% (95% CI: 4.4%–11.3%), and a five-year cumulative complication rate for implants with bone loss > 2 mm of 5.2% (95% CI: 3.1%–8.6%). A systematic review analyzing the survival and complication rates of implant-supported fixed dental prostheses with cantilever extensions found the five year estimates for peri-implantitis were 5.4% (95% CI: 2%–14.2%) (Aglietta and coworkers 2009).
At the First European Workshop on Periodontology in 1993, the terms peri-implant mucositis and peri-implantitis were clearly defined. Peri-implant mucositis was defined as inflammation of the peri-implant mucosa, and peri-implantitis as inflammation of the peri-implant mucosa in addition to loss of supporting bone (Albrektsson and Isidor 1994). Recent publications have used these definitions, resulting in a clearer insight into the prevalence and incidence of these biological complications.
Cross-sectional studies are valuable for determining the prevalence of biological complications in individuals with implant-supported prostheses. In recent years, a number of these studies have been published with the aim of determining the proportion of subjects within a population with peri-implant mucositis and peri-implantitis.
Mombelli and coworkers (2012) published a review focused on the epidemiology of peri-implantitis. Based on the data from 23 studies reporting information on the presence of signs of peri-implantitis in populations of at least 20 implant cases, they suggested that the prevalence of peri-implantitis is in the order of 10% of implants and 20% of patients during a five- to ten-year period after implant placement.
A subsequent systematic review and meta-analysis including 9 studies with 1,497 participants and 6,283 implants reported summary estimates of 63.4% of participants for the frequency of peri-implant mucositis and 18.8% of participants for the frequency of peri-implantitis (Atieh and coworkers 2013).
There has, however, been great variation in reported prevalence data for peri-implantitis with some authors reporting a lower prevalence in the order of 1.8% - 10% of subjects over a ten-year period (Buser and coworkers 2012; Cecchinato and coworkers 2013).
One of the difficulties in determining the prevalence of peri-implantitis is that authors use different bone-loss thresholds to define a case of peri-implantitis. One example illustrating this is described in a study from The University of Oslo, Norway, where a group of 109 subjects who had received dental implants between 1990 and 2005 were clinically and radiographically examined a mean of eight years after restoration of the implants. The prevalence of peri-implantitis depended on the bone loss thresholds and probing-depth thresholds used. The prevalence of peri-implantitis was: 47.1% of subjects when defined as inflammation and detectable bone loss; 20.1% of subjects when defined as bleeding on probing at peri-implant pockets ≥ 4 mm with bone loss ≥ 2 mm; and 11.7% of subjects when defined as bleeding on probing at peri-implant pockets ≥ 4 mm with bone loss ≥ 3 mm (Koldsland and coworkers 2010). Obviously, the prevalence of peri-implantitis will depend on the thresholds and definition used. In addition the prevalence of peri-implantitis is also likely related to the subjects within the convenience sample examined. Factors including the skill of the treating clinician, the proportion of smokers or periodontal patients within the population, and the frequency and nature of the supportive care program will have an impact on the prevalence of peri-implant mucositis and peri-implantitis.
As the use of dental implants increases worldwide, it is likely that the prevalence of biological complications will also increase. Clinicians need to be aware of the procedures for management and prevention of these complications outlined in this Treatment Guide volume.
2.3Literature Review:
Hardware Complications and Failures
U. Brägger
2.3.1Mechanical and Technical Risks
A literature review was prepared for the ITI Consensus Conference in Stuttgart to identify mechanical and technical risks for implant-supported reconstructions (Salvi and Brägger 2009). Ten conditions with a potential impact on the integrity of implant-supported reconstructions and their prosthetic components were identified after searching the literature:
•Type of retentive elements supporting overdentures
•Presence of cantilever extension(s)
•Cemented versus screw-retained reconstruction
•Angled/angulated abutments
•Bruxism
•Crown/implant ratio
•Length of the superstructure
•Prosthetic materials
•Number of implants supporting a fixed dental prosthesis (FDP)
•History of mechanical/technical complications
A total of 35 clinical reports compared the events observed over at least four years with or without these potential risk conditions.
Regarding overdentures, it was found that, independent of the retention elements, patients required multiple prosthetic maintenance. Technical/mechanical complications occurred more frequently with ball retainers than with bars. Retention was perceived to be better with bars compared to ball retainers; the lowest retention was found for magnets. Metal frameworks were recommended to reduce the observed rate of resin body fractures where no framework was present.
When short FDP with or without cantilevers were followed within the same study population, no difference in the rate of technical/mechanical complications was documented. In one study, cantilevers exceeding 15 mm in length were associated with a high risk of framework fracture and, therefore, remakes of full-arch reconstructions.
The few studies that compared cemented and screw-retained crowns and short FDP did not indicate an increased risk. Similarly, the available data did not indicate an increased risk for reconstructions on angulated versus straight abutments.
An unfavorable crown-to-root ratio has traditionally been perceived as a risk factor for implant loss. There was, however, no evidence to be found in the literature that the ratio of crown height versus osseointegrated implant length would determine the incidence of complications or failures. However, smaller reconstructions were more prone to complications than extended ones. Reconstructions with previous complications or multiple complications did demonstrate a higher risk for the definitive mechanical/technical failure, especially—and significantly more frequently—in bruxers (patients with attrition). One study also reported more chipping on veneered titanium versus gold frameworks.
One of the main findings of this review was that the 10 factors examined did not affect the integration of the implant or the crestal bone height.
The small number of papers included and the quality of the data presentation available at the time did not allow a pooled statistical analysis in terms of a meta-analysis.
2.3.2Effect of Improved Components on Complications and Failure Rates
In 2013, at the most recent ITI Consensus Conference held in Bern, Switzerland, a major focus was on consensus statements and recommendations for clinical procedures regarding prosthetic materials and production processes.
It was assumed that the continuous improvement of prosthetic components would result in better survival and success rates for implant-supported reconstructions. One way to assess any such improvement would be to compare event rates reported in older and newer publications (Pjetursson and coworkers 2014)
The year 2000 was chosen as a cut-off, and results from 31 older studies were compared to data from 108 more recent studies. Estimated five-year survival rates for cemented reconstructions increased from 95.2% to 97.9%, for screw-retained reconstructions from 77.6% to 96.8%.
The survival rates for implant-supported single crowns increased from 92.6% to 97.2%, for FDP from 93.5% to 96.4%.
In the older studies, annual rates for screw loosening ranged from 0.79% to 6.08%. This means that after five years, 3.9% to 26.2% of the reconstructions were affected. The more recent studies reported event rates between 0.62% and 2.29%, affecting between 3.6% and 10.8% of the reconstructions at five years.
Annual rates for abutment screw fractures ranged from 0.16% to 0.44% (0.8%–2.2% at five years) in the older publications. This was reduced to 0% to 1.2% (0% –5.8% at five years) in the more recent studies.
Fractures of the veneering material ranged from 0.25% to 4.28% per year in the older studies but remained high at 0.64% to 5.82% per year in the more recent studies.
The rates for implant and framework fractures and for loss of retention did not change significantly.
The total incidence of technical complications reported ranged from 2.32% to 10.46% per year in the older studies and even higher, with 3.55% to 15.19%, in the more recent studies.
While the survival rates of the reconstructions were increased and the abutment-related failures/complications were reduced considerably, veneer chipping and total events seemed to have increased, according to newer publications.
This could be explained by an increased awareness on the part of clinical researchers for the need to report in detail all events related to the quality of the superstructure and the components rather than concentrating on implant survival and changes in bone level.
2.3.3Complication and Failure Rates with Cemented versus Screw-retained Reconstructions
One of the systematic reviews prepared for the 2013 ITI Consensus Conference focused on the clinical performance of screw-retained versus cemented fixed implant-supported reconstructions (Wittneben and Millen 2014). A thorough search identified 4,324 titles of publications. Ultimately, 73 publications were included for analysis. The number of publications and the quality of the data presentation allowed a pooled analysis and a random-effect Poisson regression analysis when several studies were summarized.
Estimated failure rates and the weights of all included studies related to cemented and screw-retained reconstructions were presented based on 5,858 reconstructions observed over a mean observation period of 5.4 years.
Of these, 59% were screw-retained, while 41% were cemented. Grouping into single crowns, shorter FDP, and full-arch FDP did not reveal any significant difference in failure rates between cemented and screw-retained reconstructions.
When the material was considered, the cemented all-ceramic crowns revealed higher failure rates than metal-ceramic crowns. A similar difference was not found for the screw-retained implant crowns.
Technical complications as a whole occurred more frequently with cemented reconstructions than with screw-retained reconstructions. “Loss of retention” and “screw loosening” as separate events were also significantly more frequent with cemented reconstructions, while “ceramic chipping” was more frequent in the screw-retained ones.
As far as biological complications are concerned, the presence of fistulas/suppuration* was more frequently observed with cemented restorations. Overall, biological events were significantly more frequent with cemented prostheses.
2.3.4Complication and Failure Rates with Metal versus Ceramic Abutments
A third systematic review focused specifically on the survival and success rates of abutments (Zembic and coworkers 2014). The search returned 24 publications (1996–2012) for data extraction.
Three randomized clinical trials presented data comparing zirconia versus titanium, alumina versus titanium, and titanium versus gold abutments.
Components from eight commercially available implant systems were involved, with external and internal connections.
However, of the total 2,186 abutments analyzed, only 134 were ceramic abutments. The mean observation period was 5.5 years.
The quality of the data presentation and the number of publications allowed the pooled calculation of event rates per 100 objects per year. Ceramic abutments survived at 97.5% at five years; metal abutments, at 97.6%. The estimated rate of mechanical complications was 8.9% for ceramic abutments and 12.0% for metal abutments.
The percentage of technical complications was 1.3 times higher for implants with external connections.
Eight studies also reported on incorrect fit affecting 1 ceramic and 19 metal abutments (20 out of 2,186 implant-abutment connections).
2.3.5State of the Art of CAD/CAM-assisted Production of Implant-supported Reconstructions
The fourth systematic review covered the available evidence to support the use of computer-aided design/computer-aided manufacturing (CAD/CAM) technology for the production of custom prosthetic components and frameworks (bars) (Kapos and Evans 2014). Of the seventeen publications included, two reported on CAD/CAM crowns, six on implant CAD/CAM abutments, and nine on implant-supported CAD/CAM frameworks.
The short-term survival rates were high for CAD/CAM single crowns, with no failure reported in one study with 24 crowns and only 1 out of 75 crowns that had to be remade in another study.
The short-term survival of CAD/CAM individualized abutments was also high, with no failed abutments in four studies and 1 out of 58 and 3 out of 40 abutment failures in two other studies.
The data on CAD/CAM frameworks included observation times between 24 and 120 months. One study reported 5 out of 26 framework failures; another study reported 2 out of 67 framework failures. A third study reported 5 out of 66 framework failures. No failures were reported in four studies; one study did not comment on prosthetic survival.
In addition to the failures, a rather high incidence of chipping was reported for at least four studies considering complications, whereas four studies reported no technical complications and one study focused on bars only.
In summary, this implies that the availability of CAD/CAM technology has not eliminated the risks for hardware-related complications.
Several systematic reviews have explored the prosthetic maintenance needs for implant-supported overdentures.
The most frequent hardware-related problems reported are associated with the activation or replacement of patrix-matrix components, as well as maintenance required for the overdenture or restorations in the opposing jaw.
A time-dependent analysis of reported maintenance with implant-supported overdentures resulted in continuous rates for the maxilla and the mandible during year 1, between years 1 and 5, and after year 5 (Cehreli and coworkers 2010).
It was also found that the type of the attachment system did not have an effect on the prosthetic outcome with the overdenture (Cehreli and coworkers 2010).
This review was based on 49 clinical studies and listed hardware-related events including: patrix loosening; patrix activation; patrix replacement; patrix fracture; dislodged, worn or loose matrix or housing; matrix activation; matrix replacement; matrix fracture; fracture of the implant-supported overdenture; fracture of the acrylic above a patrix; fractured denture teeth; relining of implant overdentures; fabrication of a new overdenture.
The evaluation of pooled data from several clinical studies yields weak conclusions. When analyzing the data, it becomes obvious that there is always a range of observed complication rates. Therefore, fewer complications did occur in some patient groups, and the procedures and components yielding the best outcomes should be identified and applied.
A significant piece of information is that the inclination of the implants had an adverse influence on prosthodontic maintenance. Not least for the prevention of overdenture-related complications, prosthetically driven implant placement is needed (Walton and coworkers 2001).
Whereas the reported survival rates of implant-supported overdentures are very high, a substantial number of maintenance visits are required and time needs to be invested during the years following the insertion of overdentures.
A regular maintenance schedule is recommended for early detection of component wear, so that the affected components can be replaced before extensive repairs are needed.
2.3.7Survival Rates of Reconstructions Obtained from Systematic Reviews
Numerous systematic reviews have focused on the estimated survival and success rates expected with different types of reconstructions.
The event rates per 100 reconstructions per year were retrieved from observed events and extrapolated to five or ten years’ exposure.
These estimated event rates were the basis for statistical comparisons of the outcomes with various types of reconstructions.
In Figure 1, the expected prostheses survival rates of various tooth or implant-supported reconstructions were marked graphically, based on the systematic reviews by Aglietta and coworkers 2009, Harder and coworkers 2009, Heydecke and coworkers 2012, Jung and coworkers 2008, Jung and coworkers 2012, Koller and coworkers 2011, Lulic and coworkers 2007, Sunnegardh and coworkers 2012, Pjetursson and coworkers 2004, Pjetursson and coworkers 2007, Pjetursson and coworkers 2008, Pjetursson and coworkers 2012, Rohlin and coworkers 2012, Romanos and coworkers 2012, Romeo and coworkers 2012, Sailer and coworkers 2007, Sailer and coworkers 2012, Salinas and coworkers 2010, Schley and coworkers 2010, Stavropolou and coworkers 2007, Tan and coworkers 2004, van Heuman and coworkers 2009, Wasseman and coworkers 2006, Wittneben and coworkers 2009, and Zurdo and coworkers 2009.
The overview demonstrates that failure rates increase with time. Differences between the reconstructions can be observed after only a brief exposure; and the range of the estimated failure rates increases drastically after longer exposure periods.
One would like most patients to be found in the upper right corner of the graph; reality, however, tells a different story.
Patients, treatment providers, and insurance companies will have to accept the fact that the incidence of prosthetic failures and complications is increasing. The steepness of the progress depends on the type of reconstruction and is associated with patient-related and other risk factors.
It is therefore important to avoid and control as many risk factors as possible during the treatment planning phase as well as during the production and insertion of implant-supported reconstructions and their regular prophylactic maintenance.
Evidence-based analyses of the literature as presented in this volume of the ITI Treatment Guide therefore have a direct impact on clinical practice and feed knowledge into the clinical process.