Author: Dr. Suma, Dr. Jayashreedexith, Dr.Hemanthkumar.
Near Meenakshi Temple, Kammanhalli, Bangalore, Karnataka.



Abstract :
The purpose of this article is to identify the types of complications that have been reported in conjunction with endosseous root form implants and associated implant prostheses. The search focuses on publications that contained data regarding implant complications. The complications were divided into the following 5 categories: surgical bleeding, implant failure, implant loss, implant infections. The most common implant complications were hemorrhage-related complications.
It was not possible to calculate an overall complications incidence for implant prostheses because there were not multiple clinical studies that simultaneously evaluated all or most of the categories of complications¹

Although the implant data had to be obtained from different studies, they do indicate a trend toward a greater incidence of complications with implant prostheses, hence the article discuss some major aspects of complications associated with endosseous implants.

Introduction:
The placement of osseointegrated implants is generally accepted as a safe and minimally invasive procedure with a low rate of surgical morbidity. Many surgical complications have been identified in the implant literature, including hemorrhage-related complications, neurosensory disturbance, adjacent tooth devitalization/damage, mandibular fractures life-threatening hemorrhage ,air emboli, implant displacement into the mandibular canal, screwdriver aspiration, descending necrotizing mediastinitis, intraocular hemorrhage, and singultus (hiccups) and few other complications ²

Bleeding:
A major life-threatening event such as a catastrophic hemorrhage from placement of an implant has been reported³. In a reported case, the bleeding appeared to originate from many different locations, and pressure from the internal hemorrhage caused a dissecting hematoma, which, together with edema from aggressive tissue retraction and manipulation, gave rise to elevation of the floor of the mouth and, consequently, the airway obstruction. It was clear in the report that the incision was excessively lingualized and the lingual flap reflected in an erroneous surgical plane (supraperiosteally or through the periosteum). A perforation of the lingual aspect of the mandible by a drill might have also contributed to vessel damage ⁴.

Lingual hematoma:
It is necessary for dental implant practitioners to investigate the anatomy and vascular supply of the mandible at the stage of pre-treatment plan. Most studies indicate that the submental and sublingual arteries may course intimately to the lingual cortical plate from the floor of the mouth .The submental artery is most often the arterial major source to supply blood to the floor of the mouth . .In a report , the injured vessels in the floor of the mouth are most likely branches of the sublingual artery and not the submental artery as suggested by Bavitz et al. (1994).⁵. The use of X-ray imaging is not a useful substitute as it may not visualize these canals (McDonnel et al., 1994), but dental CT has the advantage for pre-implantation assessment of jaw anatomy to visualize the position, diameter and course of the lingual vascular canals of the mandible. However, in the most reported cases, arterial damage was also induced by perforation of the lingual cortical plate and plexus. It is a critical that the periosteum should be elevated carefully and not perforated. In patients with atrophic edentulous mandible, the alveolar ridge resorption could be considered a risk factor for cortical perforation (Woo et al., 2006). Clinicians should inform the patients of the potential complication well in advance, and surgeons should be well educated and trained to apply the primary emergency procedures, as well as determine the correct implant length well in advance which results in a favorable prognosis .The primary procedures to control the bleeding in the dental office are limited.

Bavitz et al. (1994) indicated that previous attempts to ligate the lingual artery for floor of mouth hemorrhage may be ineffective and that the sublingual or its parent facial artery should be ligated first. If this does not control the bleeding, then the lingual artery should be ligated. Arterial ligation procedures are complex operations and require the expertise of a surgeon skilled in head and neck surgery. External arterial ligation is only used in severe or uncontrollable cases. One simple preventive method is to palpate the lingual surface to determine the possibility of perforation potential. In addition, gently advancing the bur during preparation would be helpful. A lingual subperiosteal flap will ensure direct observation and protection of the lingual structures⁶.

Implant loss:
More implants were lost with overdenture prostheses than with fixed complete dentures, fixed partial dentures or single crowns. More implants were lost in the maxilla than mandible with fixed complete dentures and over dentures but not with fixed partial dentures. More failures occurred preprosthetically with overdentures and fixed partial dentures, whereas more post-prosthetic failures were found in conjunction with single crowns. Higher failure rates occurred with shorter implants. Significantly higher failure rates were found with implants placed in type 4 bone compared with those in types 1 to 3 bones.

Gingival inflammation was the most frequent complications. Screw loosening was the frequent reported mechanical complication. Prosthesis gold screws fractured more often than the abutment screws. Other mechanical complications included fractures of the metal framework, resin base, facial/occlusal veneer material, overdenture prosthesis, and opposing prosthesis. Clip/attachment loosening and fracture were reported with overdentures as well as the need for post placement relines. Phonetic problems were reported with all prostheses, except single crowns and esthetic problems, involved all prostheses, except overdentures⁷

Implant failure:
The criteria that define the success of dental implants have been changing continuously, and currently include, the absence of mobility at the start of the prosthetic phase, the absence of continuing radiolucency around the implant ,the absence of peri-implantitis with suppuration, and subjective complaints from the patient. Failure of endosseous implant is either early or late, depending on whether it occurs before or after occlusal loading with a prosthetic superstructure.

Early failure of dental implants is thought to be caused by failure of bony healing around the implant and subsequent failure of osseointegration,this could be attributed to local or systemic factors⁸ .Despite using well-documented dental implant systems, the possession of adequate clinical experience, the use of measures to avoid cross infection, and the adequacy of soft and hard tissues ,implants could fail early after insertion. A narrow keratinized gingiva was significantly associated with early loss of implants, However, other studies have shown that a thin or absent masticatory gingiva was associated with bleeding on probing and a significantly greater mean loss of alveolar bone. Polyglactin was associated with a higher incidence of early loss of implants(p = 0.048)than silk sutures. A recent study described the largest early loss of implants occurred with short and narrow implants and also found that the loss of implants was more common with narrow implants .One possible explanation is that narrow and short implants are usually placed in areas in which there is limited space or insufficient volume of bone. There is evidence to suggest that smoking may have a dose-related effect on osseointegration. The periodontal and endodontic state of neighboring teeth has to be taken into consideration when inserting implants. Higher failure rates were reported when implants inserted next to neighboring teeth than implants in an edentulous ridge⁹.It has been suggested that type4 and 1bones are more likely to fail. It has been speculated that the inability to establish intimate bone-implant contact compromises bone healing, which in turn leads to fibrous union and failure¹⁰. This applies where there is lack of primary stability and when the integrity of the bony socket is violated ¹¹ .For platform-switched implants, the crestal bone was often located higher than the implant shoulder due to their subcrestal placement. Due to the absence of microgap between the abutment and the implant and its platform-switched design, no crestal bone loss was reported.Minimizing cantilever lengths, elimination of non- working contacts, centralization of forces and proper framework design are key factors in success of implant- supported overdentures. The current development of implants surface treatment such as the sand blasted acid etched surfaces, the incidence of implant failure due to loss of osseointegration is rare and occurs secondary to systemic factors. In implant supported Removable prosthesis among different attachment types (ball, bar, and magnets ) The magnet and ball group presented the highest incidence of prosthetic complication as compared to bar group. Implants placed too far lingually in mandibular overdenture prosthesis will result in encroachment of tongue space and will cause problems in patient comfort and speech. Masticatory problems anteriorly are unsual and are usually related to tooth positions and can lead to problems with tipping of the prosthesis or lip biting .Loosening or fracture of the of the attachment screws is common problem associated with the prosthetic restoration of implants . Use of mechanical or electromagnetic torque wrenches will help in optimizing torque force ¹².

Implant infection:
Oral implants are anchored in jaw bone and yet penetrate the mucosa, reaching the highly contaminated environment of the oral cavity. The microflora of the dental peri-implantitis resembles that found in chronic periodontitis. Despite of variety of therapeutic options infected implants are difficult to treat, usually require removal¹³.

Cavernous sinus complication:
In an ,the carotid cavernous fistula was found associated by the onset of ipsilateral Tolosa-Hunt syndrome that appeared 5 months after the placement of dental implant and 4 months after local infection at the site of implant. The carotid cavernous fistula was of nontraumatic origin and predominantly supplied by the branches of the right internal maxillary artery that distributes extensively over the maxillary sinus and dura mater of the cranial base. The patient did not have a history of sinusitis, and clear paranasal sinuses were confirmed at presentation. In addition, lesions likely to present with Tolosa-Hunt syndrome were not identified other than the carotid cavernous fistula. Therefore,it was assumed that implant infection spreading hematogenously to the maxillary and sphenoid sinuses reached to the cavernous sinus and might attribute to the formation of carotid cavernous fistula with Tolosa-Hunt syndrome. Following the notion that the carotid cavernous fistula might arise in the setting of infection with inflammatory reactions, carotid cavernous fistula presenting with Tolosa-Hunt syndrome is explainable. Dental implant–associated infection may cause carotid cavernous fistula or Tolosa-Hunt syndrome and has to be managed promptly with adequate manner before it spreads¹⁴.

Fungal infection:
Fungal sinusitis of the maxillary sinus is most frequently caused by aspergillusspecies, a fungus of the ascomycetes class most commonly encountered in the human environment. which is the most well known example of chronic noninvasive fungal sinusitis, An unusual case of aspergillusinfection associated with dental implants and sinus bone grafting are reported which suggests the importance of considering fungal infection as a part of the differential diagnosis in sinusitis ¹⁵.

Sinus complication:
The presence of the maxillary sinus leads to unique complications, including maxillary sinusitis, oroantral fistula, and displacement of implants16. Invasion of maxillary sinus is a relatively frequent complication in dental implant in patients with inadequate posterior maxillary height ¹⁷. There are few reports of the displacement of dental implants into the maxillary sinus. UEDA & KANEDA¹⁸. reported a case of maxillary sinusitis caused by a displaced connection screw, patients had infections of the maxillary alveolar bone, and the displacement may have been caused by the destruction of the maxillary sinus floor following an alveolar infection. Although a surrounding foreign body reaction may have been predisposed to migration. If an implant placed in maxilla , penetrates the floor of the maxillary sinus clearly showing a lack of osseointegration, it can easily migrate into the sinus without apparent force. In cases such as this, failed implants must be removed immediately¹⁹. Some complications like Rhinorea have been induced by loading of dental implants²⁰ . It is known that slight sinus membrane perforation due to implant placement usually heals spontaneously.However, the previous study showed that when implants penetrated the mucosa of the sinus floor more than 4 mm, the portions of the implants extending into the sinus cavity were not fully covered with a newly formed sinus membrane with an increase in the mucosal thickening. The most likely explanation for this complication, as reported by Raghoebar et al., is that altered nasal airflow could have induced irritation of the nasal mucosa. In addition, nasal clearance could be disturbed by implant blockage, mucociliary pathway, giving rise to inflammation ²¹. In addition, debris may accumulate on the exposed implant surfaces extending into the sinus cavity that are not covered with the antral membrane. To decrease the risk for developing side effects, it is recommend that lifting of the sinus mucous membranes be performed before inserting implants in a resorbed upper jaw where sinus penetration is unavoidable ²². Avoiding complication begins with careful treatment planning based on accurate understanding of preoperative anatomy and potential problems²³.

Neurosensory disturbances:
Neurosensory disturbances were also most commonly reported surgical complications. Failure to precisely locate the inferior alveolar nerve and mental foramen invites surgical insult by the drills and the implant itself. Such insult may cause irreparable damage to the nerve, often felt as a paresthesia (numbness) or dysesthesia (painful numbness) of the gum, lip and chin. This condition may persist for life and may be accompanied by unconscious drooling. The 4 most frequent causes of nerve injury related to dental implant surgery are errors in evaluation and planning, the injection of local anesthetic, the bone preparation (drilling), and placement of the implant.²⁴

Events that can lead clinicians to suspect nerve injury include pain or altered sensation during drilling or implant placement, slippage of the drill or implant deeper than planned, and the presence of excessive bleeding, especially if nerve proximity is suspected.Patients may complain of altered sensation even though clinical procedures were uneventful. Management of the problem will depend on the cause of the IAN injury. As mentioned earlier, nerve injury can occur for many reasons. Radiographs must be taken to confirm whether it has been caused by the implant. If the implant is impinging on the nerve, it should be removed or at least unscrewed a few threads to relieve the pressure on the nerve. To control inflammatory reactions in the injured nerve, a course of steroids can be prescribed ²⁵.Inferior alveolar nerve transposition is a useful adjunct for managing the atrophic posterior mandible with dental implants. The risk of permanent dysfunction of the mental nerve appears small²⁶.

The use of new bone imaging technique for prevention of implant complications:
When computed tomography or, more specifically, cone beam computed tomography or CBCT (3D X-ray imaging) is used preoperatively to accurately pinpoint vital structures including the inferior alveolar canal, the mental foramen, and the maxillary sinus, the chances of complications might be reduced as is chair time and number of visits²⁷. CBCT allows the surgeon to create a surgical guide, which allows the surgeon to accurately angle the implant into the ideal space²⁸.

Conclusion:
Appropriate case selection , diagnosis and treatment planning along with making use of more definitive diagnostic tools such as CBCT or denta scan for further detailing of underlying anatomy and taking aid of surgical radiographic stents will minimize the risk of potential complications.

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