Beyond Osseointegration: Dealing With Late Dental Implant Complications

The advent of dental implants has been a boon in the field of restorative dentistry. With dental implants, the treatment modalities to replace missing teeth have widened considerably. While the advantages of implants are undeniable, they are not without complications. There are insufficient reports on the problems of dental implants, which paints a skewed view that dental implants are somewhat “immortal” and the ultimate gold standard for restoring missing teeth. With the often quoted 95% survival rate of dental implants,¹  such treatment modalities have been regarded as the ideal option to replace missing teeth. While we duly acknowledge the immense contributions of dental implants, the difficulties of maintaining these implants for life should also be acknowledged.

Dental implant complications can be classified according to the timing of the complication (perioperative versus postintegration) or according to their supposed cause (biological versus technical).²  Biological complications refer to disturbances in the function of the implant due to biological processes that affect the supporting tissues around the implant, such as peri-implantitis. Technical complications in dental implants refer to mechanical damage of the implant/implant components and suprastructures.³  A systematic review by Pjetursson et al⁴  concluded that approximately 38% of implant-supported fixed prostheses sustained biological or technical complications after 5 years in function. Bear in mind that most studies on implant success have been conducted in academic institutions under stringent protocols. It would be assumed that in less than ideal situations often found in general dental practice, the percentage of complications would be higher.⁵  In this series of case presentations, we will highlight late complications associated with osseointegrated implants after functional loading and how such problems were managed.

A 67-year-old patient presented with the complaint that his “implant crown had shifted” after 3 years in function (Figure 1). Upon examination, the implant crown on #30 had rotated buccally. As this was a cement-retained prosthesis, a hole was drilled through the crown to access the implant screwhead. The abutment had fractured at the internal hex, but due to the clamping force from the screw, the prosthesis remained connected, albeit loose, to the fixture. The fractured hex ring was retrieved with a fine ultrasonic scaler tip. A new implant crown with certain amendments was designed to reduce the load on the posteriormost implant. The occlusal table was made narrower, and the occlusal contacts were made lighter with slight shim-pull contact during maximum intercuspation and no contact during lateral excursions to offset the heavier masticatory forces associated with the posteriormost teeth.

Although it involved a purely technical complication, case 1 emphasizes the importance of patients knowing the implant system used in their oral cavity. This patient meticulously kept all dental treatment records and was able to trace the original dentist and implant system used. Thus, acquiring the correct tools to remove the abutment and fabricate a new prosthesis was straightforward.

This 50-year-old patient complained of discomfort and foul smell from the lower left quadrant for about a year (Figure 2). Upon examination, 5-mm probing depths were observed around the implant (#18) with bleeding. Excess cement beneath the implant crown was evident on a radiograph, so the patient was advised to return to the dentist who did the original implant restorative work for management. The dentist dismissed the complaint, but the patient later developed abscess buccal to the implant area. The implant crown was subsequently removed via an occlusal access cavity to engage the abutment screwhead, and abundant remnant cement was evident at the margins between the abutment and crown. The decision was made to bury the implant due to its ill-placed position: too deep and with a too narrow restorative space. The space was narrow as the site was previously occupied by an impacted second molar that was surgically removed and immediately replaced with an implant.

In case 3 (Figure 3), the anterior implant (#8) had been placed about 10 years earlier and generally had no problems. The 52-year-old patient later developed swelling around #8 and returned to the dentist for management. Upon examination, the dentist declared that the implant was fine as it was firm and surrounded by bone radiographically. The dentist prescribed systemic antibiotics without further treatment. When the condition did not improve after the antibiotics, the patient sought a second opinion from a periodontist, who noted a 9-mm probing depth on the buccal surface. Nonsurgical debridement was done. At the 2-week review, the rough surface of the implant was exposed and uncovered more calculus, which was cleaned up. The mucosa healed with further recession.

Failure to recognize and appropriately treat peri-implant diseases at an early stage, especially in the anterior region, can lead to esthetic disasters. Although the implant in case 3 had been placed many years earlier, the patient was not followed up with maintenance care,⁶  which possibly led to the development of peri-implantitis.

Case 4 is an example of dental tourism gone wrong (Figure 4). The patient presented with a complaint of a mobile upper prosthesis and swollen and bleeding gums, causing much pain and discomfort. Full-mouth rehabilitation work had been done in the country where the patient was stationed 5 years earlier. The patient was a smoker, had diabetes, and was prone to periodontitis. Examination of the maxillary prosthesis revealed a long-span, roundhouse, fixed prosthesis, which was no longer fixed. The patient also had a 4-unit acrylic bridge spanning #20 to #18, with 2-mini implants in between.

The management for this patient was to remove all the failed prostheses that were aggravating the patient's periodontal health. Removal of the failed maxillary bridge and implants revealed ridge lap intaglio zirconia surfaces packed with food debris that was could not have been cleaned by even the most dexterous patient. Removal of the 4-unit acrylic bridge revealed 2 unidentified mini implants and inflamed soft mucosa. As the mini implants were still firm, composite resin was used to cover the projections before fabricating partial dentures for the patient. The upper arch was rehabilitated with a full acrylic denture.

A 34-year-old patient (current smoker) presented with exposed threads on the labial surface of the implant on #8 (Figure 5). A radiograph of the implant revealed crestal bone loss with radiolucency between the crown and the abutment platform. The patient had received the dental implant as part of a live surgery demonstration for a new implant brand about 10 years earlier. However, 2–3 years after the implant was loaded, the patient noticed the greyish hue of the implant showing through the gums and a foul taste coming from the implant area. The patient sought treatment from multiple dentists, but no one could identify the implant or offer any conclusive treatment. As a final resort, the implant was removed, leaving a large bony defect covered by nonkeratinized tissue. Soft and hard tissue augmentation has been planned to reconstruct the affected area for a new implant.

This exotic implant was no longer on the market, which illustrates the difficulties of dealing with unknown implants. The 1-piece implant with aggressive threads was unsalvageable; thus, explantation was the best option.

A 58-year-old patient presented with pus exudate from a fractured implant on #19 and a mobile #20 (Figure 6). Deep periodontal pockets and bone loss were also evident around other teeth. Both #19 and #20 had a poor prognosis and were extracted/explanted. Guided bone regeneration was performed, which enabled 2 implants to be placed 6 months later. The patient was also treated for periodontitis and put under maintenance.

This patient was a known bruxer with Class III malocclusion, which might have contributed to occlusal overload leading to the fractured implant. However, the implant on #18 remained intact with some degree of porcelain chipping on the implant crowns.

Mechanical complications are usually easily detected by clinician and patient. Screw loosening or abutment fractures usually manifest as mobile implant crown or, in some cases, total dislodgement of the prostheses. Screw loosening occurs when the joint-separating forces acting on the screw joint are greater than the clamping forces holding the screw unit together.⁷  The external joint-separating forces include off-axis occlusal contacts, lateral excursive contacts, interproximal contacts between natural teeth and implant restorations, protrusive contacts, parafunctional forces, and nonpassive frameworks attached to implants.⁸  If the external joint-separating forces] exceeds the clamping force, it will eventually result in loss of preload. Other examples of mechanical complications related to overdentures are also easily recognized, such as fracture of the overdenture acrylic, fracture of porcelain on the implant prosthesis, and fracture of framework. Mechanical complications are often a sequela of biomechanical overloading, which may result from poorly planned or executed restorative treatment. Factors that contribute to biomechanical overloading in implant occlusion include overextended cantilever on implant frameworks, parafunctional habits and heavy bite force, excessive premature contact, large occlusal table, steep cusp inclination, poor bone density/quality, and inadequate number of implants supporting the prosthesis.⁹ 

Implant-protected occlusion concept is meant to reduce occlusal force on implant prostheses, thus protecting implants. Some modifications to the conventional occlusal concepts are suggested, such as providing load-sharing occlusal contacts, modifying the occlusal table and anatomy, correcting load direction, increasing implant surface areas, and reducing occlusal contacts in implants with unfavorable biomechanics.^10,11  A word of caution is warranted though: in cases of occlusion with a reduced number of natural teeth accompanied by multiple implants, overdoing this implant-protected occlusion concept may result in deleterious effects by overloading the few remaining natural teeth. Thus, judicious use of this concept is imperative to ensure overall occlusal stability in the oral cavity.

While dealing with mechanical and biological complications of dental implants is part and parcel of practicing dental implantology, the work is more difficult if the implant system is unknown and unattainable in one's practice. In cases 4 and 5, the implants were unknown and the restorative protocols unfamiliar. Barrowman et al¹²  demonstrated a problem with dental implant tourism in cases in which dental implants installed overseas could not be restored because the implant system could not be identified. Dental implant tourism is a headache for clinicians when implants are placed in a foreign country and the patient subsequently encounters problems simply because there are so many implant systems on the market. Jokstad et al¹³  identified at least 220 brands of dental implants produced by about 80 manufacturers. The impact of constant changes in the dental implant landscape is significant; when implant systems disappear from the market necessary remedial implant work becomes more complicated.

If an implant system is unknown to the clinician or patient, it will take guesswork using radiographs to identify the implant system.¹⁴  Websites such as “What Implant Is That?” use radiographic images to identify the implant system.¹⁵  A few countries recently attempted to create a national registry of dental implants,¹⁶  but perhaps a more practical approach would be to educate patients and make them aware of the need to know their dental implant systems.

Inflammation from bacterial biofilm appears to be the initiating factor for periodontitis and peri-implant diseases.^17,18  Bleeding on probing, deepened probing depths, suppuration, and radiographic bone loss, in combination, paint a clinical picture of diseased periodontal/peri-implant tissues.¹⁹  As with evaluation of periodontal diseases, examination of dental implants requires peri-implant probing,²⁰  with emphasis on the presence of bleeding on probing.²¹  Cautious probing around dental implants has no detrimental effects on peri-implant health.²²  In case 2, deep probing depths, bleeding on probing, and suppuration hinted at peri-implant disease.¹⁹  The combination of clinical and radiographic evaluation led us to suspect that remnant cement had been left within the peri-implant sulcus. Case 2 was not merely a case of undiagnosed peri-implant disease. As the implant was done immediately after surgical removal of an impacted tooth, the implant was likely sunk deeper to achieve primary stability. This made it almost impossible to remove excess cement as the crown-abutment interface was too far subgingivally.²³  When local postextraction anatomy does not permit prosthetically driven and maintainable implant positioning, a delayed approach is preferred.²⁴ 

Removal of biofilm is of utmost importance when treating peri-implant diseases.¹⁸  Systemic antibiotics without removal/disruption of tenacious biofilm renders such treatment less effective.²⁵  The multicellular structure of biofilm shields the microorganisms within from antibiotics and host immune cells.^25,26  If we can mechanically disrupt the complex structure of a biofilm, penetration of antibiotics and host defenses can be greatly improved.²⁶  In case 3, failure to detect clinical signs of peri-implantitis and injudicious prescription of systemic antibiotics led to delayed treatment and substantial loss of soft and hard tissues. To date, the patient has refused surgical management of #8 and is under 6-month peri-implant maintenance. Indeed, once an implant has been restored, individualized peri-implant supportive care should be prescribed and patient compliance upheld.⁶  This permits monitoring of peri-implant tissue health and early intervention should problems arise. This is particularly important in periodontitis-susceptible patients who are at higher risk of peri-implant diseases.²⁷ 

Placement of implants immediately after extraction does not preserve the buccal cortical bone.²⁸  In most cases, the buccal cortical bone in the anterior maxilla is very thin (≤1 mm)²⁹  and the use of aggressive threads to achieve primary stability during immediate implant placement may end up traumatizing it. Certain criteria for immediate implant placement must be strictly adhered to. A thick (≥2 mm) buccal bone, controlled periodontal disease, and adequate bony dimensions to allow proper angulation of the implant are prerequisites.³⁰  A smoker (case 5) is surely a poor candidate for such therapy.³¹  Smokers have an increased annual bone loss rate of 0.16 mm/year compared with nonsmokers³²  and are at higher risk for peri-implant diseases³³  and failure.³⁴  However, the clinician may not recognize such pitfalls unless they follow up their patients over the long run.

Biological and mechanical implant complications often come hand in hand. In case 6, we postulate that uncontrolled periodontal disease may have caused bone destruction around #20 and #19. Due to significant bone loss around the implant neck coupled with occlusal overload, the implant may have fractured as the cervical region of the implant was subjected to the most occlusal stress.³⁵  However, one may argue that the extensive bone loss around #20 and #19 may have been a consequence of the fractured implant neck serving as a plaque retentive factor in a periodontitis-susceptible patient. Natural teeth adjacent to implants with peri-implantitis are prone to attachment loss.³⁶  Unfortunately, periodic radiographs to aid in a conclusive diagnosis were not available.

With the growing popularity of dental implant treatment, the occurrence of more implant complications appears inevitable. It is crucial that clinicians who place dental implants are able to identify the signs and symptoms of implant complications and possess adequate knowledge on factors that can contribute to the occurrence of such complications in order to manage them satisfactorily. Mitigating complications early may prevent the total loss of the implant itself.

This work has been supported in part by the Young Researchers' Incentive Grant (GGPM 2017-109), The National University of Malaysia.

The authors declare no conflict of interests