A 5-Year Retrospective Analysis of Biologic and Prosthetic Complications Associated With Single-Tooth Endosseous Dental Implants: Practical Applications

Abstract

Focused Clinical Question:

What are the key considerations of the incidence and timing for single-tooth implant complications, including early failure, biological complications, and prosthetic complications?

Summary:

Single-tooth dental implants have been shown to have a high overall survival rate, but implant complications affect patient satisfaction and may lead to costly and/or time-consuming repair and revision. Assessing the incidence and types of biologic and prosthetic complications and the timing of such complications is helpful so that the underlying causes can be addressed during the treatment planning process. Furthermore, identification of patient demographics, patient-, implant-, and site-specific factors associated with such complications may allow for more comprehensive risk assessment during treatment planning.

Conclusions:

Overall, dental implants have a high survival rate. Identification of the incidence of both biologic and prosthetic complications and minimizing their impact in patients with dental implants is critical to overall implant success. Utilization of careful treatment planning and dental implant fixtures, surgical protocols, and prosthetic designs that reduce complication rates can improve patient acceptance and outcomes. Further research is necessary to fully assess complication rates and risk factors.

Graphical Abstract

Background

The need for tooth replacement with dental implants in partially edentulous patients is a common problem in individuals with missing teeth due to many causes including agenesis, trauma, caries, fracture, and periodontal disease. Implant therapy to support single implant-supported crowns (ISCs) is based upon the tenets of osseointegration and has been common practice for nearly four decades.¹ It is estimated that up to 5 million dental implants are placed each year.² Additionally, longitudinal survival rates of osseointegrated dental implants range between 90% and 95%,^3–5 which would indicate implant failure rates that reach up to half a million fixtures annually. While survival data are most often reported, this may not give a full picture of the rate of complications, including peri-implant bone loss. Complication rates reported in a systematic review indicate that, in implants assessed over a 5-year period, cumulative prosthetic and biologic complication rates were 8.8% and 12.3%, respectively.⁶ Given the high prevalence of implant complications, it is imperative for dental professionals to identify dental implant-related factors that may lead to increased biologic and prosthetic/occlusal complications.^7–9 Much reported longitudinal implant data focuses on survival rates, which may belie other implant complications that impact the health and longevity of dental implants and patients.¹⁰ An improved understanding of the incidence and types of biologic and prosthetic complications and the timing of such complications is helpful during the treatment planning process and was the aim of this retrospective analysis.

Implant Complications

Implant complications may be early or late and biological and/or prosthethic.^6,11,12 Common biological complications include peri-implant mucositis and peri-implantitis. Prosthetic complications include implant screw loosening, implant screw fracture, prosthesis fracture, and/or implant fixture fracture. While the underlying etiologies for prosthetic and biologic complications differ, the impact on patients and practitioners in terms of time, cost, peri-implant maintenance considerations, and esthetics can be considerable and the incidence and underlying etiologies of both types of complications should be considered.

Biologic complications

Peri-implant mucositis.

Peri-implant mucositis has been defined as an inflammatory lesion of the mucosa surrounding an implant without loss of supporting peri-implant bone.^13,14 Peri-implant mucositis has been shown to develop when biofilm deposits accumulate within the mucosal sulci at osseointegrated dental implants.^13–15 While these lesions have been characterized as analogous to gingivitis lesions around teeth, it has been noted that the histologic inflammatory lesions associated with peri-implant mucositis are larger and require a longer time of pristine oral hygiene to reverse than gingivitis lesions.^16,17 The overall incidence of peri-implant mucositis has been reported to be observed in up to 65% of subjects with dental implants.¹⁸ Clinical signs associated with peri-implant mucositis include bleeding upon gentle probing, erythema, edema, and suppuration.¹⁴ Additionally, while peri-implant mucositis is reversible and may be present for long periods of time without progression to peri-implantitis, it is considered a precursor to peri-implantitis and may progress if left untreated.^15,16,19

Peri-implantitis.

Peri-implantitis is a pathological condition occurring in tissues around dental implants that are osseointegrated and in function, which is characterized by inflammation of the peri-implant mucosa and loss of supporting peri-implant bone.^14,20 Clinically, these lesions are characterized by swelling, erythema, pain, bleeding upon probing, suppuration, increasing probing depths, and radiographic bone loss.¹⁴ Peri-implantitis lesions have been demonstrated to commence early (within three years of function) in the postrestorative period and to progress more rapidly than is seen with periodontitis lesions.^21,22 Peri-implantitis progression occurs in a nonlinear, accelerating pattern.²¹ Risk factors that have been associated with peri-implantitis include a history of periodontitis, smoking, hyperglycemia, retained cement, restorative design, implant-abutment interface, and previous implant failure at the implant site.^20,23–27 Overall incidence of peri-implantitis varies in different reports and have been reported to range from 10% to 47%.^18,28,29 Given the highly prevalent nature of peri-implantitis and the relative difficulty in treating peri-implant lesions, identification of high-risk patients is critical in clinical practice.

Prosthetic complications

While prosthetic implant complications do not have an underlying microbiological etiology and do not, in most cases jeopardize the osseointegration of the dental implant, they are nevertheless a clinical problem during the practice of treating implant patients. A recent review has identified six categories of technical or mechanical failures: loosening of screws, screw fracture, fracture of framework, fracture of abutment, chipping/fracture of veneering material, and decementation.³⁰ As reported in this retrospective analysis, the overall incidence of technical or mechanical complications for all implants in partially edentulous patients was 10.8% for single implant restorations and 16.1% for partial fixed implant-supported prostheses over approximately a 5-year period.³⁰ The most common form of mechanical complication for single implant restorations was screw loosening and was veneering material fracture in partial fixed implant-supported prostheses.³⁰ Furthermore, prosthetic complications have been subdivided into those associated with industrial components (eg, implant and/or abutment fracture) and those associated with customized components (eg, restorative porcelain veneer fracture, restoration debonding, etc).³¹

Clinical Scenarios

Clinical scenario 1: Early implant failure

A 48-year-old male received an implant at site #9 that was placed immediately upon extraction of tooth #9 that was fractured subgingivally and deemed restoratively hopeless (Figures 1a–1f). His medical history is significant for traumatic brain injury (25 years prior to implant placement), coronary bypass surgery (5 years prior to implant placement), and cerebrovascular stroke (1.5 years prior to implant placement). The patient currently reports taking no medication and monitoring blood pressure daily. Implant #9 was placed immediately following tooth extraction. Graft material was placed around the implant within the extraction socket and a custom healing abutment to shape gingival tissues was placed at the time of implant placement. Placement torque value was >35 N/cm. At a 2-week postoperative visit, patient noted pain and mobility at the implant site and an increase in radioopacity was noted on a peri-apical radiograph. The implant was explanted 2 weeks after surgical placement. It should be noted, that this presentation cannot be considered peri-implantitis as the implant was not osseointegrated and in function and rather represents an early implant failure.

FIGURE 1.

A-F, Early implant failure at site #9 with immediate implant failure. 1a,1b, Postoperative clinical photograph and radiograph after immediate implant placement and custom abutment placement at site #9. 1c,1d, Clinical photograph and radiograph 2 weeks after placement when patient presented with pain and mobility at the implant site. 1e,1f, Clinical photographs of the explantation site and explanted implant after early implant failure and implant removal

Clinical scenario 2: Late biologic complication(s)

A 68-year-old female received implants #18–20 at lower left quadrant after a long-span fixed partial denture teeth #17–20 failed due to caries (Figure 2a–2g). Patient stated that teeth #19, 18 had been lost >30 years prior due to caries. Due to vertical bone loss, implant short (7.5 mm length) implants were placed at sites #18, 19. The patient’s medical history was significant for hypothyroidism, Type 2 diabetes mellitus, anxiety/depression, and hypertension. She is currently taking celecoxib (200 mg), acarbose (25 mg), levothyroxine (100 mg), tramadol (50 mg), losartan (100 mg), duloxetine (60 mg), pregabalin (75 mg), aripiprazole (10 mg), furosemide (20 mg), and metoprolol (50 mg). Her HbA1c at the time of implant placement was 6.8%. This patient sought sporadic periodontal maintenance care and her recorded HbA1c ranged from 6.8% to 7.9% during the 2 years postrestoration, which was considered poorly controlled. While plaque accumulation and inflammation was noted throughout the natural dentition, periodontal attachment loss was not noted during this 2 year period. Two years after restorative loading, #19 demonstrated radiographic bone loss >75% and mobility and was explanted. At the time of explantation, it was noted that the width of keratinized mucosal at the implant site was <2 mm, which may have also predisposed the implant to plaque accumulation and subsequent peri-implant inflammation.

FIGURE 2.

A-F, Late biologic implant failure at site #19. 2a, Postoperative radiograph after implant placement at sites #18–20. 2b, Post-temporization radiograph at implants #18–20, 4 months after implant placement. 2c,2d, Clinical photograph and radiograph 2 years after implant placement when patient presented with mobility at implant #19. 2e,2f, Radiograph and clinical photograph of explantation site and explanted implant after loss due to peri-implantitis

Clinical scenario 3: Late prosthetic complication(s)

An 81-year-old female received an implant at edentulous site #19 (Figures 3a–3f). His medical history is significant for hypertension and benign prostatic hyperplasia (BPH). He currently reports taking daily lisinopril (10 mg), ASA 81 mg, and a multivitamin. He also reports a penicillin allergy. His periodontal diagnosis upon initial presentation is clinical health on a reduced periodontium. After surgical implant placement, the implant was submerged and restored after 3 months of healing. The patient received a custom titanium abutment and a screw-retained zirconia crown. After restoration, he was referred for ongoing peri-implant maintenance and was seen on a 6-month interval rotating between his restoring dentist and his periodontal surgeon. One year after crown delivery, 10–15% radiographic bone loss was noted and at 2 years after crown delivery, the patient presented with a mobile restoration and fractured abutment screw. The emergence profile of the crown was noted to create a subgingival environment that was plaque-retentive. Intrasurgical evaluation demonstrated a circumferential peri-implant defect that was approximately 3mm deep and 1–2 mm wide. This patient received surgical debridement of the peri-implant defect and grafting of the intrabony defect with freeze-dried bone allograft and a collagen membrane. Post-operative radiographs taken 8 months after surgical therapy demonstrate partial radiographic bone fill. At this time, a new implant supported abutment and screw-retained crown were fabricated and the patient was referred for peri-implant maintenance on a 4-month interval.

FIGURE 3.

A-H, Late prosthetic implant failure at site #19. 3a,3b, Radiographs prior to and at the time of dental implant placement at #19. 3c, Implant restoration placed 3 months after surgical implant placement. 3d, Implant at 1 year post-restoration demonstrating 1–2mm of radiographic crestal bone loss. 3e, Implant at 2 years post-restoration after loss of implant supported abutment and crown due to abutment screw fracture. 3f, Restoration with fractured abutment screw. 3g, Intrasurgical intrabony peri-implant defect dimensions. 3h, 8 months postsurgical grafting procedure with placement of new implant-supported abutment and screw-retained crown

Clinical scenario 4: Long-term implant health

A 63-year-old male received a surgical implant placement at edentulous site #30 with a restoration placed 5 years prior (Figures 4a–4d). His medical history is significant for hypertension and hypercholesterolemia and he currently takes daily lisinopril (20 mg), simvastatin (20 mg), and 81mg ASA. The patient has a dental history significant for Stage II, Grade B Periodontitis, and a previous history of implant failure at #30 due to peri-implantitis. The patient states that he sought sporadic periodontal maintenance care after the initial implant placement at site #30, but has received periodontal and peri-implant maintenance every 3 months after current implant placement and restoration.

FIGURE 4.

A-D, Implant health at implant #30 at 5 years after placement. 4a, Post-operative radiograph at time of implant placement site #30. 4b, Radiograph at implant #30 after final restoration placement. 4c,4d, Clinical photograph and radiograph 5 years after implant placement at site #30 demonstrating maintenance of bone levels and a lack of clinical signs and symptoms of inflammation

Discussion

Implant complications, including prosthetic and biologic complications, are common^{6,18,28,30,31} and careful assessment and treatment planning to identify and address such considerations is critical to improving the implant success rates and patient satisfaction.³² Given the myriad considerations that contribute to biologic and prosthetic failures, it may be critical to assess incidence biologic and prosthetic complications, not merely implant survival, for various implant designs and manufacturers.

To investigate the potential for such an assessment, a retrospective chart review was conducted on records of patients treated with FDA-approved endosseous dental implants from one manufacturer^‡ placed in a graduate periodontics residency program^§ during calendar years 2007–2010, with up to 5-year follow up. All individuals provided written informed consent prior to surgical implant placement and a consent waiver for this retrospective research was approved by the Institutional Review Board at the University of Alabama at Birmingham (IRB-140922002). Recorded patient characteristics were: age, gender, race, smoking, and comorbidities including diabetes, osteoporosis, and history of periodontal disease (PD). Cumulative incidence of (a) early complications (defined as complications prior to restoration), (b) late biological complications (biologic complications after restoration), and (c) late prosthetic complications (prosthetic complications after restoration) were calculated with two-sample t-test and Chi-square test. Data were analyzed to determine the relationship of demographics, systemic conditions, history of periodontal disease, implant size, and implant type (one-piece, internal hex connection, and external hex connection) with complication rates using chi-square and analysis of variance test for categorical and continuous variables, respectively. Odds ratios (OR) and associated 95% confidence intervals were calculated for the association between biological and technical complications and confounders were evaluated using multivariable logistic regression. A P-value < .05 was considered significant in two-tailed statistical tests. All analyses were conducted using SAS 9.4 (SAS Institute, Cary, NC).

A total of 189 patients and 408 dental implants were identified in this retrospective analysis. The patients included in this study averaged 58 years in age (±14) and included 60% women. Demographic data are summarized in Table 1. Mean follow up was 6.2 years (±1.7 years) and over that period, 8.5% of participants experienced early complications, 16.1% experienced late biological, and 11.5% late prosthetic complications. The most frequent biological and prosthetic complications were bone loss (15.12%) and screw loosening (7.32%), respectively. After adjusting for other potential risk factors, multivariable logistic regression models suggested that early complications were more likely in females than males (OR 2.97; 95% CI 1.1–8.0). Risk factors associated with increased risk of developing late biological complications included female gender and PD. No statistically significant difference was observed regarding implant size/design in regards to sex, race, tobacco use, PD, osteoporosis, or diabetes. There was no observed statistically significant difference among implant size/design regarding the rates of late biologic or late prosthetic complications (Table 2).

TABLE 1.

Demographic characteristics and rate of biological and prosthetic complications of 139 individuals with 281 implants with a laser-grooved collar design

DEMOGRAPHICS	N (SD)	P-value†
Mean age at implant placement (years)	58.4±12.8	<.0001
Sex (%)
Male	48 (35.0)	.0004
Female	91 (65.0)
Race (%)
Black	17 (12.1)	<.0001
White	117 (84.3)
Other	5 (3.6)
Reported tobacco use (%)	20 (14.3)	<.0001
MEAN FOLLOW-UP TIME (years)	2.4±1.7	<.0001
BIOLOGICAL COMPLICATIONS
Events	48
Rate per year (95% confidence limits)	0.07 (0.05–0.09)	<.0001
PROSTHETIC COMPLICATIONS
Events	39
Rate per year (95% confidence limits)	0.05 (0.04–0.07)	<.0001

^†P-values estimated from chi-square for equal proportions and one-sample t-test for difference from 0.

TABLE 2.

Summary of types of biological and prosthetic complications noted in this sample

Biological Complications (n = 48)
Peri-implant mucositis	18 (6.4%)
Peri-implantitis	30 (10.6%)
Prosthetic Complications (n = 39)
De-bonding of prosthesis	10 (3.5%)
Screw loosening	21 (7.4%)
Prosthesis fracture	8 (2.8%)

The overall incidence of prosthetic complications in this retrospective analysis was similar to that seen in previous studies, but late biologic complications were generally lower than other reports, which have been reported in scientific literature at up to 47% in all implant systems.^18,28,29 This decrease in biologic complications may be due to the selection of implants from one manufacturer, the common laser-grooved collar design, that the implants were placed by clinicians in a supervised environment with standardized implant placement protocols, the rigorous presurgical treatment planning undertaken in these cases, and/or that the implants received regular peri-implant maintenance during the follow-up period. It should be noted that this retrospective analysis did not allow for biologic sampling or comparisons with other manufacturers in a controlled environment and further prospective randomized controlled trials are necessary to determine the relative rates of complications among implant types.

Supportive implant maintenance and clinician surgical and restorative skill level have both been associated with improved implant outcomes long term.^7,11,33–36 Furthermore, it is conceivable that the use of implants with a laser-grooved collar design may have yielded an altered attachment apparatus that may be more resistant to breakdown in the presence of plaque biofilm than that at other peri-implant soft tissue junctions. The laser-grooved collar has been shown to demonstrate a histologic attachment of soft-tissue fibers that are oriented perpendicular to the implant surface³⁷ and laser-grooved surfaces were found to reform these histological attachments even after disruption in a human model.³⁸ It is therefore possible that this more robust attachment apparatus may provide a physiologic barrier to peri-implant soft tissue migration and reduce biologic complications.

Given these findings, overall assessment of manufacturer-specific complication rates and the effect of ongoing peri-implant maintenance should be further studied to quantify the effects that these may have on long-term implant success and to establish benchmark thresholds for acceptable implant outcomes. Furthermore, the relative frequency of both biologic and prosthetic implant complications indicates that a focus on individualized risk factors associated with these complications should be thoroughly assessed prior to implant placement to allow for ideal treatment planning and personalized peri-implant maintenance.^7–9,32

Lastly, it is well-established that treatment of peri-implant complications can be particularly challenging. In clinical practice, successful treatment of peri-implant diseases to achieve optimal oral health and esthetic outcomes relies upon many patient, site, and treatment-related factors.^13,20,32 Multiple systematic reviews and randomized controlled trials have evaluated the efficacy of various treatment strategies for peri-implant diseases.^39–41 Identification of a single ideal treatment strategy applicable to all clinical scenarios has proven elusive.^39,40 It is imperative, therefore, that a priori treatment planning to reduce both biologic and prosthetic implant complications be an integral part of implant therapy. Given the challenges faced by clinicians in treating implant complications, particularly peri-implantitis, utilization of implant fixtures and surgical protocols that reduce the rates of such complications is critical to improving long-term implant success rates and patient outcomes.

Conclusion

Overall, dental implants are a successful and impactful treatment option for tooth replacement and improvement of esthetics, phonetics, and masticatory function in partially and completely edentulous patients.^3–5,42 However, despite high survival rates, late biologic and prosthetic complications may vary based upon implant system and implant design, surgical placement protocols, ongoing implant maintenance, patient compliance with home care, and prosthetic design. It is critical that care be taken to identify and address risk factors for complications during the implant treatment planning process and that clinicians seek to minimize risk by adherence to protocols that have been shown to reduce late complication rates. Further research is necessary to fully assess complication rates and risk factors. Furthermore, once those complications have developed, more ideal treatment options for peri-implant diseases and conditions should be identified.