Custom-made 3D printed subperiosteal implant for restoration of

severe atrophic jaw: a case report

In the last decades, considerable progress has been made in the field of oral implantology, regarding endosseous implants, especially through the changes brought by the digital revolution. Although their versatility and predictability has been proven over time through clinical studies and follow-ups, endosseous implants have certain limitations, mainly given by the patients’ perspectives: the general state of health, bone supply, long osseointegration time, etc. Well-designed subperiosteal implants have been reported to function successfully for many years and came as an alternative to endoseous implants. The analog method of inserting subperiosteal implants has been widely discussed and used over time, and represents a well-defined protocol. However, the first surgical time, that of taking impression of the residual bone field, caused problems for the clinicians as follows: the trauma inflicted to the patient was greater as he was subjected to two surgical interventions instead of one(first for the impression of the bone and second for the insertion of the implant), the grip contraction of the impression material creates the possibility that the implant doesn’t fit to the bone. Digital technology comes into our hands in order to solve this unpleasant situations, offering the possibility to design the future implant on the CBCT scan of the patient long before the surgery itself.

This case report reviews the design characteristics of 3D printed superiosteal implants, step by step procedure and its particularities compared with the analog method, the anatomy of the areas upon which the implants rest in the maxillae, based on recent research perfomed in Romania, in collaboration with AB Dental International (1).

Introduction

The use of endosseous dental implants to replace missing teeth has been a very predictable solution for many years and is now one of the most common techniques in dental rehabilitation. However, sufficient bone quantity and quality is required for implantation. In cases of severe bone resorption, bone regeneration techniques, zygomathic implants, nerve lateralization and sinus lift surgeries were proposed, but unfortunatelly these methods require more advanced surgical procedures, which may result in higher complication rates, morbidity, and longer treatment times.

Subperiosteal implants were first developed in Sweden at the beginning of 1940’s and have been used ever since, with a decrease in popularity with the invention of the first endoseous implants by Branemark. Subperiosteal implants were custom-made based on an impression obtained in the stage I surgery and inserted below the periosteum and stabilised to the bone with mini-screws, then covered by the mucosa in the stage II surgery. Thus, the pacient was subject to two surgeries at an interval of 21 days. The subperiosteal implants were made of cobalt-chrome or titanium alloys and were connected to the prosthesis using transmucosal abutments that emerged into the oral cavity. Their replacement or decrease in use was due to the complexity of the production process, the imperfect fit of the implant caused by relative instability of the impression material, the wide range of complications (2).

Different protocols have been proposed lately for subperiosteal implants, especially the ones 3D printed, but infortunately romanian clinicians need to collaborate with abroad factories or laboratories in order to treat these cases. Here, the authors present their experience with an innovative design of a customized subperiosteal implant manufactured by AB Dental International based on the CBCT scan of the patient.

Case history/examination

A 58 years old male patient with severe maxillary athrophy was referred to the clinic due to complaints of inappropriate masticatory and aesthetic function. He reported a mixed tooth-implant supported maxillary rehabilitation with five implants and two teeth which failed 3 years ago after more that 15 years of use due to peri-implantitis and mobility. Ever since, our patient has been wearing a removable acrylic denture. The pacient denied smoking habits or relevant systemic diseases. In order to decide whether he is a valid candidate for a subperiosteal implant or not, the patient was passed through the entire selection process which included: general examination, clinical local examination of the oral mouth, laboratory analysis and radiographs. The pre-operative laboratory analysis were slightly modified with a high value of the PDW (Platelet Distribution Width) which can indicate anemia or an infection in the body. Clinical examination [Fig. 1(a)](12) and orthopatomography [Fig. 1(b)](12) indicated a combined horizontal and vertical severe osseous atrophy, confirmed through cone-beam computed tomography (CBCT) [Fig. 2](12).

Note : In some areas, due to the severe bone atrophy, oro-sinusal communications covered only by the mucosa were evident on the CBCT scan, in which case the patient’s removable denture functioned as a protective „shield”.

The cone-beam computed tomography has confirmed an inflamtion of the sinus mucosa due to odontal causes (infections associated with the previous teeth) and the severe lack of alveolar bone in all the maxillary regions that could be seen in the preliminary radiographs. The highest points of the residual bone were found, firstly, as it can be observed on the CBCT, in the third molars region both sides [Fig. 2(a) and 2(b)](12) with dimensions ranging between 2.4 and 7.2 mm in height and 6.6 and 10.2 mm in width in the first quadran and between 4.8 and 10.2 mm in height and 5.4 and 9.6 mm in width in the second quadran.

Implant placement in the posterior region of the maxilla, the distal area of the maxillary alveolar process, which corresponds most frequently to the position of the third molar, has been suggested by many authors as an alternative to bone grafting. The posterior maxillary region typically has type III or IV bone quality, consisting of thin cortical bone and low-density trabecular bone. Primary stability is adversely affected by this. Due to inadequate primary locking, as well as short implants having unfavourable biomechanics, this region tends to have low success rates. Therefore, clinicians face a challenge in rehabilitating this area (3).

The second area where we could measure some significant alveolar bone is the second molars region both sides [Fig. 3(a) and 3(b)](12) with dimensions ranging between 2.1 and 2.7 mm in height and 10.8 mm width in the first quadran and between 3.0 and 3.9 mm in height and 9.3 and 9.9 mm in width in the second quadran.

As it can be observed in the CBCT scan, in the first molars region both sides, the residual alveolar bone height is either less that 3.0 mm or unsignificant [Fig. 3(a), Fig. 4(a)](12), making implant placement without lateral window sinus lift impossible. In the first quadran, it is important to notice the abcence of the cortical vestibular bone and the oral comunication with the maxillary sinus, closed only by the mucosa (an where we previously mentioned that patient’s removable denture functioned as a protective “shield”).

As it can be observed in the figures above [Fig 4, Fig. 5 and Fig. 6](12), the other areas of alveolar bone have no significant dimensions that could be useful for a complete implant-prosthetic rehabilitation. Thus, the possible initial treatment plan proposed was bilateral window sinus lifting with delayed implant placement after 8 – 10 months from the initial surgery and guided bone regeneration for vertical and horizontal deficiency in the frontal area. During these 8 – 10 months of healing, the patient was to be only aesthetically rehabilitated with a removable prosthesis and the prognosis was reserved. Because he has high functional and aesthetic requests, and due to the fact that he has already been edentulous for 3 years by now, we had to find a more appropriate treatment solution.