Between 3 and 5% of all malignant tumors are located in the head and neck region. Approximately half of these are located in the oral cavity, and oral squamous cell carcinoma (OSCC) accounts for roughly 90% of the total. It is defined as a malignant neoplasm which originates in the stratified epithelium, and is typically found in men over the age of 60, who have a habit of tobacco and alcohol use. However, this trend has been changing and is being observed more and more so in patients who are under the age of 40, even in children, adolescents, and in women who do not have any risk factors. It has also been associated with other less typical risk factors such as: the existence of nutritional deficiencies, exposure to ionizing radiation, immunosuppressant and irritant factors of dental and/or implant origin.
Oral rehabilitation using osseointegrated dental implants has become one of the best options for the treatment of edentulous patients and is considered by some to be the only form of treatment. Due to the universality of the use of dental implants, the literature has also reported an increase in the number of complications associated with their use. Among such complications, the most frequent are the inflammatory processes that affect the bone and soft tissues, which are known as periimplantitis. Clinically, these conditions often occur with edema, erythema, hypertrophy and even ulcers of the soft tissues, sometimes presenting an appearance which may require a differential diagnosis with malignant lesions.
To date, very few cases have been published on oral squamous cell carcinomas in proximity with osseointegrated dental implants, and even less on primary carcinomas in patients without a previous history of malignancy at the local or regional level. However, with the increase in the number of implants, we are likely to see an increase in the cases of oral squamous cell carcinoma. In this study, we present a review of the cases published in the literature on oral carcinomas associated with implants and we examine whether there is a direct relationship between the implants and the development of OSCC, evaluating the mechanism by which the implants may be considered risk factors. There is no data in the current literature that assess other possible causes, such as the galvanic effects that might arise from the transmembrane potential differences between the areas adjacent to the implants and the remaining mucosa; neither is there any data on the variables of decreased or increased bacterial colonization, or on the carcinogenic factors associated with the nitrosamines produced by Candida.
The mechanism by which osseointegrated dental implants could contribute to the development of oral squamous cell carcinoma is very debatable. Some authors argue that the placement of implants may contribute to the development of oral squamous cell carcinoma from the epithelium to the cancellous bone due to the loss of periodontal ligament.
The gingival attachment in implants is an area that experiences constant inflammation, which may affect the stability of the mucosa, and this inflammation may play an important role in the development of cancer due to the action of cytokine mediators such as: prostaglandins, interleukin-1, interleukin-6 and tumor necrosis factor. Additional risk factors may also be added, such as: alcohol and tobacco consumption, irritating factors such as an improperly fitted prosthesis or poor oral hygiene. In the literature reviewed, the vast majority of cases referred were of patients with oral squamous carcinoma or with a history of cancer in other parts of the body prior to implant placement.
Nutritional deficiencies may explain the rapid evolution of a lesion, such as we present in case study 1, given that gastroplasty reduces the area of absorption for some nutrients and vitamins at the stomach level, increases the gastrointestinal transit rate and also reduces the absorption of certain necessary elements - all of which are associated with the local irritation factor of implants, which could explain the process in a patient who does not have any toxic habits.
Of the 12 cases described, only 6 of the patients did not present a prior history of carcinomas or cancer. In 2004, Shaw et al. presented 2 cases of squamous cell carcinoma: one in a 67-year-old male and another in a 64-year-old female patient, without a prior history of malignant lesions or risk factors. In both cases, the lesions appeared to be compatible with those associated with peri-implantitis. In 2008 Schache et al. reported a case in a 77-year-old male with an exophytic lesion located in the left mandibular region, associated with implants that support a fixed denture which was placed 5 years ago. The patient has no history of cancer, peri-implantitis or inflammation of the mucosa, nor any known risk factors. In 2008, Chimenos-Küstner et al. present a case of a 62-year-old female whose risk factors include moderate alcohol consumption and being an ex-smoker, without a prior history of cancer, presenting an exophytic lesion around implants placed in the lower incisor region. The histopathological examination revealed an invasive moderately differentiated squamous cell carcinoma, requiring resective surgery with safety margins, as well as a functional radical homolateral lymphadenectomy. In 2008, Eguia del Valle et al. present a case of a 76-year-old male with a history of hypertension and hyperuricemia, who received 2 implants placed in the right hemimandible (4.5 and 4.6) approximately 5 years ago, subsequently developing an exophytic lesion adjacent to 4.6. The patient did not present risk factors and was seen regularly for check-ups. As a first treatment, a peri-implant curettage was performed and a biopsy was performed 15 days later. The histopathological examination revealed a well-differentiated squamous cell carcinoma. Excision of the tumor was then performed with safety margins, without lymph node involvement.
Of the other articles published, 2 present patients with and without a prior history of cancer and the following 6 had a history of oral cancer or cancer in other parts of the body, pre-malignant lesions or metastases. In 2008, Kwok et al. presented 3 cases. The first case concerns a 62-year-old male with poorly adapted dentures, who had been treated with 8 implants and has a history of high consumption of tobacco and alcohol. Three months after treatment, an ulcer was found in the lower right premolar region, whose histopathological study revealed a well-differentiated carcinoma. The second patient is a 71-year old male whose risk factors include heavy alcohol consumption and being an ex-smoker. He was treated with 2 implants in the lower incisor region and 6 years later an ulcer appeared which ended up being a well-differentiated squamous cell carcinoma, which was subsequently treated with surgery. The third patient is a 67-year-old female with a history of 2 small carcinomas in the lateral edges of the tongue, which were removed in 2001 and 2004. She was an ex-smoker and consumes alcohol in moderation. A breast tumor had also been removed in 1992. In 2006, she developed a hyperplastic lesion in the lower lip and during surgery, a small area of granulation tissue was found around the lower left implant. A biopsy was performed, revealing an early stage of squamous cell carcinoma adjacent to the implant. The patient was thus treated with local excision of the carcinoma. In 1996, Clapp et al.reported three cases, one of which did not have a history of risk factors. The second case presented moderate dysplasia of the oral mucosa and the third case presented a prior history of OSCC. In 1997, Moxley et al. reported a case, without risk factors, although with a history of verrucous carcinoma in the molar area. In 2001, Block and Scheufler reported a case of a patient who was an ex-smoker and had a history of verrucous carcinomas in different areas and at different times. In 2007, Abu El-Naaj et al.presented a case of a patient who is a smoker and has a history of oral lichen planus, presenting an exophytic lesion around implants in the symphyseal region. In 2006, Czerninski et al. presented 2 cases: a patient with a high consumption of tobacco and a history of oral lichen planus, and the other patient with a prior history of oral and colon cancer. In 2007, Dib et al. presented a case of a woman with metastasis around osseointegrated implants produced by a breast adenocarcinoma, which were diagnosed at the same time. In 2008, Gallego et al. presented a case of a patient without any risk factors, with a history of oral lichen planus, who subsequently presents a carcinoma in situ in another location. The patient is treated with a resection of the area and rehabilitated with implants; however, due to the recurrence of carcinoma, a mandibular resection next to the implants is performed.
There is a case of osteosarcoma in the upper maxilla associated with implant placement with the use of fill material at the level of the maxillary sinus, which opens another debate about the use of platelet-rich factors or plasma rich in growth factors (PRF, PRGF).
The article by Gulati et al. describes a 62-year-old patient who was diagnosed with a verrucous leukoplakia located in the mandibular gingiva, which upon biopsy proved to be an invasive carcinoma, requiring surgical treatment with microvascular fibula graft. The patient had undergone posterior implant treatment for the prosthetic rehabilitation of the back part of his mouth, repeatedly suffering a peri-implantitis. Finally, a biopsy was performed in the inflamed area, which led to a diagnosis of oral squamous cell carcinoma.
The role of osseointegrated implants in the formation of squamous cell carcinoma is not well-established, although the inflammation that occurs in the adjacent tissues may be an important factor which contributes to the development of this pathology.
Before an implant treatment, the patient’s risk factors must be established and an appropriate cost-benefit evaluation must be conducted for each patient.
In patients with risk factors, regular check-up should be performed in which a thorough examination of the oral cavity is performed, and in the case of a lesion that raises any questions, a biopsy and the subsequent histopathological examination should be performed in order to make a correct diagnosis as soon as possible.
The most frequent carcinoma associated with dental implants occurs in the form of peri-implantitis; that is why any of these symptoms requires thorough monitoring in order to carry out the final screening of carcinoma.
Therefore, we believe that from a medical standpoint, any implant worn over a denture should be able to be removed relatively comfortably in order to examine the peri-implant tissues and to monitor possible changes in this area.