From Volume 49, Issue 1, January 2022 | Pages 14-24
With dental implants becoming a more common treatment option for the replacement of missing teeth, and with survival rates upwards of 90% after 10 years, it is likely that primary care dentists and dental care professionals will encounter patients presenting with problems. The second article in this two-article series outlines common biological and mechanical complications arising with dental implants and their component parts, and how to manage them.
A complication in terms of implant dentistry may be considered as a non-ideal event or outcome. They can be broadly defined into three categories:1
Biological complications are multifactorial in origin, but primarily arise from plaque biofilm accumulation around the components of implants causing inflammation, bone loss and possibly leading to implant loss. Plaque biofilm accumulation is a result of suboptimal patient-performed oral hygiene, and it can be exacerbated by a poorly designed prosthesis preventing adequate plaque removal.2 Biological complications can also encompass soft-tissue complications, such as fistulae and peri-implant tissue overgrowth (Figure 1).
Peri-implant health is defined as an absence of visual inflammation, swelling and suppuration, a lack of bleeding on probing, probing-pocket depths (PPD) of <5 mm and the absence of bone loss beyond initial crestal remodelling occurring within the first year in function (which should be no greater than 2 mm) (Figure 2).3
Peri-implant mucositis is defined as inflammation of the soft tissues surrounding a dental implant without associated bone loss. It is characterized by profuse bleeding on probing, with visual signs of inflammation, swelling or suppuration.3 There may be increased probing-pocket depths given the inflammation and oedema of the tissues (Figure 3a,b). Radiographically, there should be an absence of bone loss beyond crestal bone changes after initial remodelling, no greater than 2 mm. The prevalence of peri-implant mucositis has been reported as between 19% and 65% with a mean prevalence of 43%.4
Plaque accumulation around dental implants, smoking, residual cement and radiotherapy have been shown to be risk indicators for the development of peri-implant mucositis. On the other hand, there is only weak evidence to implicate implant abutment surface characteristics, keratinized tissue width, diabetes or genetics in the development of peri-implant mucositis.5
Much like gingivitis, peri-implant mucositis is a reversible condition.6 The recommended treatment includes thorough oral health education to improve patient-performed plaque control, and professional mechanical debridement around the implant,7,8,9 aiming to disrupt peri-implant biofilm, and remove calculus.10 Adjunctive local antiseptics or antibiotics have not been found to improve the efficacy of professionally administered plaque removal and are, therefore, not recommended in the treatment of peri-implant mucositis.7,8,9 It is of paramount importance to stabilize peri-implant mucositis as a prerequisite to prevent progression to peri-implantitis, and those patients who are seen for annual supportive therapy are less likely to progress from peri-implant mucositis to peri-implantitis.7,9,11
Peri-implantitis is defined as visual inflammation with combined bleeding on probing and associated progressive alveolar bone loss occurring after initial remodelling,3 with or without suppuration. There may be increased probing-pocket depths in comparison to baseline measurements. If there are no baseline measurements or radiographs available to the clinician, a diagnosis can be made where there is ≥3 mm radiographic bone loss and/or probing depths ≥6 mm in conjunction with profuse bleeding (Figure 4).3 Clinically, peri-implantitis frequently progresses in a circumferential manner around the implant fixture.12 The prevalence of peri-implantitis has been quoted as between 1% and 47% with a mean prevalence of 22%.4
There are a number of factors that have been associated with the development of peri-implantitis:
It is also worth noting that there is some emerging evidence to suggest a relationship between peri-implantitis and titanium dissolution as a result of titanium corrosion and inflammation around the implant fixture.22 Further research is again required in this field.
The aims of treatment for peri-implantitis include the disruption of the plaque biofilm, implant surface decontamination and anti-infective measures to arrest crestal bone loss.23 Peri-implant treatment success has been defined as stable peri-implant bone levels, absence of probing depths >5 mm and no bleeding or suppuration on probing.9,24
A pre-treatment phase to control or modify the individual's risk factors for peri-implantitis is an important first step in any management plan.9 This should include smoking cessation advice, oral health education and restoration adjustment or replacement to facilitate adequate patient-performed cleaning.9,25
There has been much debate about the optimal treatment for peri-implantitis, and it is currently unclear which treatment modality is the most effective.3,10,26,27 The most important factors to consider in the treatment of peri-implantitis is the ability for biofilm disruption and decontamination of the surface of the implant.28
Mechanical debridement of the implant surface, whether as part of a non-surgical or surgical protocol is required for biofilm disruption and hard deposit removal. There is inconclusive evidence regarding the most effective approach for mechanical debridement, with techniques being divided into two groups: hand instruments (titanium, plastic, carbon or stainless-steel curettes and titanium brushes); and powered devices (metal or plastic tip ultrasonic scalers, laser therapy and air-abrasive devices with glycine powder).10,29
Concerns remain about mechanical debridement around dental implants given the potential to cause damage, either by overheating of the implant due to insufficient irrigation, or introduction of further surface roughness, potentiating biofilm adherence. There is an increased risk of creating further roughness with scaler materials, such as steel,10 which are harder than the titanium implant surfaces. Instruments should be effective without causing damage10,30 and it is generally accepted that instruments that are softer than titanium can be used without risk of damage to the implant. Plastic curettes have been shown to be ineffective at removing hard deposits, and residual cement and can also break, leaving behind fragments.30 Ultrasonic scalers with non-metal or copper alloy tips may be beneficial to prevent implant surface damage;30 however, there are concerns about how effectively they can clean implant surfaces,31 highlighting the balance that needs to be sought between implant-surface damage and thorough debridement.
A systematic review examining the effectiveness of different methods of mechanical debridement of implant surfaces found that air–powder abrasive, with either sodium bicarbonate or the amino acid, glycine, was found to clean machined, SLA (sandblasted, large-grit, acid-etched), TPS (titanium plasma sprayed) and grit-blasted titanium surfaces effectively.31 Such findings should be viewed with caution, because there was a moderate to high risk of bias for all included studies, and there was insufficient homogeneity to perform a quantitative analysis. It has also been suggested by other reviews that sodium bicarbonate-based systems are too abrasive and cause damage to both hard and soft tissue when used for implant instrumentation.10 Care should therefore be taken when using this technique around implants with limited attached gingiva. Air abrasion systems have increased in popularity over recent years, and are more effectively placed to assist with peri-implant maintenance and the management of peri-implant mucositis rather than advanced peri-implantitis.
The literature has yet to find significant improvement in treatment outcomes with the use of lasers over conventional debridement techniques.10
Non-surgical debridement of peri-implantitis sites does not appear to significantly decrease the microbial load8 given the difficulties of decontaminating the individual threads of the implant, and has limited efficacy at deeper sites.8 However, it is recommended as a first-line treatment in an effort for initial biofilm disruption.9,25
If resolution of peri-implantitis has not been achieved at review, a surgical approach should be considered as the next phase of treatment.9,10 This improves visualization and access to the implant surface and bone defect,29 but should only be considered after initial infection control has been undertaken as per the Cumulative Interceptive Supportive Therapy (CIST) protocols.25 As a first line, this protocol includes mechanical, antiseptic and antibiotic treatment to treat ongoing infection, and should always precede any surgical treatment. Following this, surgical treatments to correct bone defects can be considered.
There are a number of aspects of the surgical implant debridement technique that should be considered, which are outlined below:
Whether a resective or regenerative surgical approach is used may depend upon the pattern of bone loss that is present.10
A resective approach aims to reshape the peri-implant architecture25 and is often combined with an apically repositioned flap where there is a substantial suprabony defect.9,10 It may help with patient-performed hygiene to leave previously affected portions of the implant exposed. Implantoplasty is sometimes then undertaken to modify the implant surface and smooth the exposed threads, aiming to reduce bacterial recontamination.8,32 A resective approach is often avoided in areas of high aesthetic demand.
Regenerative approaches aim to restore the support to the implant, prevent recession and enhance chances of re-osseo-integration and are indicated where there are circumferential bony defects with intact bony walls or localized intrabony defects.10 This approach should only be considered where there is an absence of suppuration25 to ensure maximal chances of success. A bone graft material is placed in the intrabony defect after implant-surface decontamination, and covered by a barrier membrane.10
There is a lack of evidence to show whether adjunctive systemic antibiotics offer any benefit because there are few studies that directly compare their use against a control.10
It is recognized that, as peri-implantitis is a chronic disease, much like periodontitis, recurrence can occur, and re-treatment may be necessary.27 Therefore, review and maintenance of patients with a diagnosis of peri-implantitis is of paramount importance. It has been found that regular supportive care following therapy for peri-implantitis results in a high level of implant survival in the medium to long term of between 82% and 100% at 3 years post peri-implantitis treatment.33 With the protocols outlined previously, around three-quarters of dental implants treated for peri-implantitis could be expected be present after 5 years.24 However, late stage peri-implantitis may result in the ultimate loss of the implant, and further planning for a new prosthesis (Figures 5 and 6).
As outlined, the treatment for peri-implantitis is a complex topic with many documented treatment modalities, and a summary of diagnostic parameters of peri-implant health and disease can be seen in Table 1. The British Society of Periodontology and Implant Dentistry (BSP)34 and NHS England35 recognize the challenges involved in the treatment of peri-implantitis and have, therefore, categorized it as Level 3 complexity – meaning treatment should be undertaken by specialists or consultants, and an onward referral should be made where possible. However, the Restorative Commissioning Standards35 do state clearly that this is only appropriate where ‘it is the responsibility of the NHS to manage the disease when implants have been placed under an NHS contract’. It does not make any reference to patients who have had implants placed privately or abroad.
| Parameters | Treatment | ||
|---|---|---|---|
| Clinical | Radiographic | ||
| Peri-implant health* |
|
|
None required |
| Peri-implant mucositis* |
|
|
Oral health education and professionally delivered mechanical debridement |
| Peri-implantitis |
|
|
Control patient risk factors |
Mechanical complications occur when the forces applied to a prosthesis exceed the capacity of the weakest component in the system.36 They often arise as a result of inadequately designed prostheses and inadequate control of occlusal forces. The lack of proprioception experienced with implants is also thought to make these restorations more at risk of mechanical complications.37 The 5-year mechanical complication rate for implant prostheses has been found to range from 16.3% to 53.4%.38 Mechanical complications with implant prostheses may manifest in a number of different ways depending upon whether the complication is fixture, abutment or supra-structure related. Some of the commonly reported mechanical complications include the following.
If unfamiliar with implants, this can appear a strange sight, but is relatively straightforward to manage (Figure 7). The screw access hole should be irrigated to dislodge impacted food debris, after which a pledjet of cotton wool or PTFE tape should be placed at the base of the screw access to protect the screw head and ensure its retrievability. Composite material should then be placed over this and polished. In recurrent cases of restoration loss, creation of undercut within the screw access can help retain the restoration.
As with tooth-supported indirect restorations, the veneering material of implant-supported crowns and bridges may chip and fracture (Figure 8). The veneering material can be porcelain, acrylic or composite resin. To decrease the risk of fracture, a prosthesis should be designed with a sufficiently thick framework to support the veneering materials without flexure, while allowing adequate thickness of veneering material to be provided. This should be combined with a carefully designed occlusal scheme. The 5-year complication rate for fracture of veneering material has been quoted as between 3.2% and 25.5% (combined rate including single crowns, implant-supported partial fixed dental prostheses and implant-supported fixed complete dentures), with implant-supported fixed complete dentures having the highest rate.38 No differences have been found in 5-year fracture rates for metal–ceramic and zirconia–ceramic single crowns, but there are increased material fractures for multiple-unit zirconia–ceramic restorations.39 The management of these fractures depends upon the framework of the implant restoration and the extent of the fracture. If minor and not in an aesthetic zone, they can be smoothed, repaired directly chair-side, or indirectly in the laboratory after restoration removal. In severe cases, replacement of the entire restoration may be required.
This is a rare complication9 where the superstructure of a multiple unit restoration fractures, with a 5-year complication rate of 0.2%.38 To decrease the risk of this complication, the framework material, design, dimensions and method of fabrication need to be considered prior to construction, as well as the available prosthetic space.
Again, this is a rare complication with a 5-year complication rate of 0.08%.38 It is more commonly seen with narrow-diameter or hollow implants.36 If suspected, a referral back to the dentist who placed the implant is recommended.
As described in Part 1 of this series,40 implant restorations and abutments require prosthetic screws for attachment to the implant fixture. These screws can become loose if subjected to excessive occlusal forces in either poorly designed or fitting restorations, or if they were not tightened appropriately in the first instance. It tends to be more common in narrow-diameter platform implants. The 5-year complication rate for this is between 3.1% and 10.8%, and is found more commonly with screw-retained restorations.38 It presents as mobility of the restoration, which the patient may or may not be aware of. After diagnosing screw loosening, it can simply be retorqued to the manufacturer's guidelines using the correct screwdriver, and the screw access re-sealed in the case of a screw-retained restoration. If a screw re-angulation system has been used, this can further complicate management. This requires knowing what implant has been placed (brand and platform size), as well as which type of prosthetic/abutment screw has been used (as described in Part 140). Although this information should have been given by the dentist providing the implant and restoration,41 a referral back may be warranted if the correct equipment to facilitate re-torquing of the components is not available.
This process becomes more complex for cement-retained restorations under which the abutment screw has become loose. Information required prior to treatment includes the type of cement used for retention, and the type and angulation of the abutment. Treatment would first require removal of the cement-retained crown, ideally by tapping off or, in a non-ideal situation, drilling. Once removed, the screw that retains the abutment can be re-torqued, the screw covered with cotton wool or PTFE for protection and then re-cementation of the crown.
This is an uncommon complication, but one to be aware of, with a 5-year complication rate of between 0% and 5.8%.38 Fractures can occur in either the prosthetic or the abutment screw, and present as mobility of the prosthesis, or as entire loss of the crown or abutment. It may result from excessive occlusal loading, overtightening or in suboptimally designed prostheses (Figure 9). If this is suspected, a referral back to the restoring or placing dentist should be made. It is sometimes possible to remove the fractured portion of the screw from the implant, but if not, it could render the implant unrestorable. Options for fractured screw removal include the use of an ultra-sonic scaler in an anti-clockwise motion, cutting a slot in the top of the screw to allow instrument insertion or the use of a specific screw retrieval system.
This is seen in cement-retained restorations where there has been a loss of retention, usually due to poor abutment design or inadequate control of occlusal forces, leaving only the abutment present in the mouth.42
The 5-year complication rate for loss of a cement-retained restoration retention is 3.1%.38 Cement-retained restorations can be re-cemented after sufficient cleaning of the crown and abutment, and a pledjet of cotton wool or PTFE tape has been placed in the screw access hole in the abutment. If there is sufficient retention and resistance form of the abutment, the authors preference for choice of cement is Temp-Bond (Kerr, Orange, CA, USA) to ease the retrievability of the crown. Glass-ionomer cements should be avoided if recementing all-ceramic crowns. Whichever cement is used, one must consider how easily the crown could be removed if subsequent treatment is required, and care should be taken to remove all excess cement to decrease the risk of biological complications. A delay in treatment may result in gingival overgrowth onto the abutment, making subsequent recementation more challenging.
As mentioned in Part 1,40 implant overdentures can be retained with ball abutments, locator abutments, magnets or bars. Implant overdentures can be prone to complications, including wear of components resulting in a loss of retention, abutment loosening or prosthesis fracture.43 To manage these complications, the dentist first needs to diagnose what the problem is and why is it occurring. This will involve assessing the attachment system used, and its component parts. The dental laboratory can often be a source of knowledge and aid the dentist in resolving these complications.
Most simply, for locator-retained overdentures, if the plastic inserts in the denture base are worn, they can be easily replaced. The old inserts in the denture base can be flicked out with a sharp probe, and new inserts can be placed into the housings within the denture using a locator insertion tool, a plugger or a burnisher.
Other complications, such as loose denture housings, may require more input to resolve, and may need the dental laboratory to replace them. If the general dental practitioner is unsure what the problem is, they can refer back to the restoring dentist for guidance and assistance.41
Aesthetic complications can negatively impact on the perceived appearance of the implant restoration, or the patient's satisfaction with it. Suboptimal aesthetics may result from the implant prosthesis (white aesthetic), the soft tissues (pink aesthetic) or a combination of both. A number of attempts has been made to create objective scales of measurement to quantify these components, the most notable being the PES/WES index for use with single-tooth implants.44 The PES (Pink Esthetic Score) considers and scores soft tissue criteria that influence the overall aesthetics, including papilla presence or absence, gingival contour, gingival level and tissue colour and texture. The WES (White Esthetic Score) considers and scores prosthetic aspects that influence the aesthetics, including tooth form, outline, colour, surface texture and translucency/character.
Overall, the aesthetics of implant-supported fixed dental prostheses and the tissues surrounding them are highly rated by patients,45 despite 5-year aesthetic complication rates for single implant crowns being reported at 7.1%.46 It should also be noted that aesthetic agreement between patients and clinicians is poor,47 and clinicians should be careful not to influence patients with their own views.36
Aesthetic complications associated with the prosthesis itself most commonly include suboptimal shade matching (Figure 10), poor contouring of the crown or visible crown margins.
Soft tissue aesthetic complications can include gingival asymmetry, mucosal recession (Figure 11) or thin tissues allowing fixture shine-through, or even absent interdental papillae (Figure 12), which can be difficult to correct due to the underlying implant fixture position.
It is often the case that aesthetic complications are identified and rectified where possible by the restoring clinician prior to discharge, but it is possible for aesthetic complications and patient dissatisfaction to develop over time, often requiring re-referral for investigation. There is evidence to suggest that patients recalibrate their internal standards downwards, and that the initial improvement a restoration has on their oral health-related quality of life gradually reduces over time.48
Aesthetic complications can also result from the treatment and stabilization of biological complications, and discussion of these risks versus the benefits of treatment should be had with the patient as part of the consent process prior to commencing any treatment. Figure 13 demonstrates a patient with early peri-implantitis affecting an over-contoured cement-retained implant crown in the UR1 site and a poorly contoured composite restoration on UL1. It Illustrates the change in gingival architecture, particularly further loss of the papilla mesial to the UL1 following replacement with a less bulbous temporary screw-retained implant crown, and non-surgical periodontal therapy to stabilize the peri-implant tissues. There has also been replacement of the composite restoration in the UL1 and composite addition to several anterior teeth to improve the anterior symmetry and aesthetics.
Accurate pre-operative planning and excellent communication between the clinician, the patient and the laboratory are required to optimize aesthetic outcomes.
The discussion of potential biological, mechanical and aesthetic complications prior to implant placement is an extremely important aspect of the informed consent process.
As mentioned previously, plaque accumulation is a strong risk indicator for peri-implant disease,13 and patients need to be made aware of the importance of self-performed plaque control. The dentist who has provided the implant and restoration should have discussed a tailored oral hygiene routine with the patient prior to discharge;41 however, it is likely that continued reinforcement of oral hygiene instruction will be necessary as part of continued supportive care.
It is recognized that patient-administered plaque control is an effective preventive measure for peri-implant disease.2 However, there has been no difference found between the effectiveness of electric versus manual toothbrush for maintaining peri-implant soft tissue health.49 The use of oral rinses for chemical plaque control has limited adjunctive effect.2
For single-implant crowns, patients can be encouraged to clean as they would do their natural teeth. This would include the use of a powered or manual toothbrush, along with interdental brushes for interproximal biofilm removal.50 Interdental brushes have been found to be more effective for interproximal plaque removal around dental implants in comparison to floss.51 A single-tufted brush may also be of benefit, depending on the design of the prosthesis (Figure 14).
For short- and long-span bridges, the use of SuperFloss (Oral-B, Procter and Gamble, Cincinnati, OH, USA) can help to clean under pontic sites. This can be quite dexterously challenging, so regular monitoring of hygiene levels and motivation of the patient may be required. Water flossing has been suggested as an adjunct for patient-performed oral hygiene and shows greater bleeding reduction of peri-implant tissues when used in comparison to traditional floss.52
For implants used to retain overdentures, patients often need to be reminded that these should still be cleaned like natural teeth. A powered brush can be used to rotate around the abutment and gum for mechanical plaque removal, as well as on top of the abutment to ensure food packing does not occur. If food packs into the abutment (Figure 15), it may prevent the denture from seating and result in a loss of retention.
An appropriate oral hygiene regimen should have been established with the patient prior to their discharge to primary care. It is the authors' preference to suggest the use of a combination of manual or electric toothbrushing, interdental brushes for interproximal regions, single-tufted brushes around the margins of the prosthesis and areas that are difficult to access, and SuperFloss or a water flosser in pontic sites of multiple-unit fixed prostheses.
Success criteria for dental implants have been described as no mobility, no peri-implant radiolucency, vertical bone loss <0.2 mm annually after the first year in function, and the absence of persistent signs and symptoms.53 Once a patient has been discharged from the care of the implant dentist, it will be the responsibility of the general dental practitioner to monitor for peri-implant health and disease.34,41 As more patients have implants placed, it is increasingly likely that the general dental practitioner will come into contact with patients with dental implants. Being able to recognize complications when they occur will be a key attribute of general dentists and dental care practitioners in the future.
The BSP recognizes that as more implants are being placed and that peri-implantitis is becoming more common, there is an expectation that general dental practitioners will screen for biological and mechanical complications even if they have not placed the implants.34 They recommend that if the dentist is uncomfortable maintaining implants, they must refer to a colleague with more experience in the field, or ask for guidance from their local implant dentist, periodontist or clinician who placed the implant. Preventive and supportive care for dental implants is defined as Level 1 complexity treatment and, therefore, should be completed in primary care.34,35
The authors are aware that many general dental practitioners may have received no implant training and therefore, see it as a daunting area of dentistry. Standardization of undergraduate implant teaching may improve the confidence of the next generation of general dental practitioners, but this is something that needs to be addressed at a national level. The aim of this article has been to demystify some areas of dental implantology, and give an overview of component parts and complications that may arise with implants and their restorations. By increasing the reader's knowledge, we aim to increase the confidence in preventive and supportive care for patients with dental implants.
Therefore, the authors recommend that the role of the general dental practitioner in patients with dental implants should be:
