A Case of an Ultra-Short Sintered Porous-Surfaced Implant in a Patient With Periodontitis: 11-Year Follow-Up

Alveolar ridge resorption due to the loss of 1 or more teeth is influenced by many factors, such as age, gender, diabetes, osteoporosis, genetic predisposition, and periodontal disease. In addition, the longer the time elapsing after dental extractions, the less bone volume will be available for standard-length implant placement.^1–3  Several surgical techniques for the purpose of vertical bone augmentation have been described, including guided bone regeneration (GBR), distraction osteogenesis, intra- and extra-oral bone grafting, interpositional grafts, and combinations thereof.^3,4  These procedures are case-sensitive, technically demanding, and time-consuming. They may also contribute to increase postoperative morbidity and the total duration of the therapy.⁵  Short implant placement has become a good alternative to overcome the limitations posed by deficient residual ridges.³  This solution reduces the time, cost, morbidity, and patient's discomfort by comparison with bone augmentation procedures.^3,6 

In this case report, we describe the rehabilitation of a single edentulous site in the right posterior area of the upper jaw with an ultra-short, sintered porous-surfaced (SPS) implant. The most coronal 1 mm segment of the implant's length is prepared as a machined collar, while the remaining 4 mm of intrabony length is coated with a 300 μm SPS layer.^7,8  This surface has the advantage of promoting a faster osteointegration and greater bone-implant contact (BIC).^6,7  On the other hand, like all the other rough surfaces, the SPS has the disadvantage of favoring biofilm formation and raising the risk of the onset and progression of peri-implantitis,^9,10  a risk that is already higher in patients with a history of periodontitis.¹¹ 

This case report shows that, when appropriate surgical, prosthetic, and hygienic protocols are followed, ultra-short SPS implants can nonetheless prove an excellent solution for the rehabilitation of severely resorbed posterior alveolar ridges even in patients with a history of periodontal disease.

In October 2006, a 57-year-old man was referred to the authors with deep furcation exposure and wide mobility of tooth #3 as a result of generalized chronic periodontitis. He had previously been treated with a complete cycle of nonsurgical periodontal therapy to eliminate all residual periodontal pockets, and to reach a mean full-mouth bleeding on probing (BOP) score of <25%. The patient's past medical and social history was noncontributory. Orthopantomography (OPT) and periapical X rays were obtained to plan the extraction of tooth #3 (Figure 1). Three months later, periapical X ray and cone-beam computerized tomography in dental scan mode were used to assess bone width and height and to plan implant positioning (Figures 2, 3). An ultra-short SPS implant was chosen because of the severe atrophy of the alveolar ridge and the patient's refusal of a bone graft. The authors opted to insert the implant after a manual osteotomic preparation and a series of surgical drills to achieve ridge expansion, good primary implant stability, and sinus floor elevation without any bone grafting. The whole porous-surfaced region of the implant and the 0.5 mm smooth coronal region were fully submerged in bone (Figure 4). Four months later, the implant was uncovered and the healing abutment was inserted (Figures 5, 6). An impression was obtained 2 weeks afterward to make a provisional prosthesis (Figure 7). After an additional 3 months, another impression was taken to fashion the definitive prosthesis, which was placed on the implant 2 days later (Figure 8). Both the provisional and the definitive prostheses were checked in occlusion to eliminate precontacts and interferences during centric and eccentric movements, with reduced areas during lateral and protrusive excursions and several contacts in maximum intercuspation.

The patient was included in a well-established oral hygiene protocol, generally applied to all periodontal patients undergoing implant rehabilitation, with the aim of achieving and maintaining optimal hard and soft tissue health. This protocol scheduled oral hygiene instructions, professional dental hygiene, probing pocket depth (PPD) measurements, and checks on occlusal contacts every 4 months. Radiographic assessments with periapical X rays were scheduled every 8 months. The anatomical crown-implant ratio was 2.5. The clinical crown-implant ratio was 3.1 at the baseline, and 3.3 after 11 years of follow-up. No pathological PPD, calculus or signs of peri-implantitis were observed during the follow-up (Figures 9–12).

The biomechanical rationale behind the use of short implants is that the crestal portion of the osteointegrated bone-implant interface absorbs most of the prosthetic loads.⁶  Short implants can consequently be used in regions with severe alveolar atrophy with high implant success and survival rates, comparable with those of longer implants inserted after bone grafting.^4,12 

In the present case, an ultra-short SPS implant was used to rehabilitate a severely resorbed site in the right posterior maxilla. The use of a sintered porous surface increases the BIC, consequently providing a wider area over which the masticatory forces come to bear and thereby reducing the stresses at the bone-implant interface.⁶  The main disadvantage lies in the fact that this surface favors plaque adhesion and the rapid onset of peri-implantitis when it is exposed to the oral environment. The risk increases considerably in patients with a history of periodontitis.^9,10 

This report shows that proper surgical, prosthetic, and hygienic management enables the long-term survival of ultra-short SPS implants even in patients with a history of periodontal disease. The success of such procedures relies on several factors.

First, the entire porous-surfaced region of the implant and at least 0.5 mm of the smooth coronal region must be fully submerged in bone;⁸  and the width of the buccal and palatal crestal bone around the implant must be at least 1.5 mm to prevent biofilm contamination of the porous surface.¹³  When the residual alveolar bone ridge is insufficient to guarantee compliance with the aforementioned criteria for adequate implant placement, using the Alternating Osteotome Technique described by Malchiodi^14,15  enables the bone volume to be increased by at least 25%–30%, by means of a combined ridge expansion and sinus floor elevation.¹ 

Second, the biomechanics of implant prosthetic structures play a key part in long-term implant success. Considering the crown height as a vertical cantilever,⁶  the crown-implant ratio must be less than 3.1 to prevent peri-implant bone loss⁸  and screw loosening or fracture as result of overloading.¹⁶  It is also essential to carefully check occlusion in centric and eccentric movements at every follow-up visit, particularly in patients with periodontal issues because a greater mobility of their teeth combined with an altered periodontal proprioception can lead, with time, to changes in the occlusal contacts, with consequent implant precontact and overloading. That is why the implant occlusion must only be adjusted when the occlusal contacts are relieved with the residual teeth at their maximum level of intrusion. This is achieved by asking the patient to bite for a few seconds as forcefully as possible before attaching the prosthetic crown and using articulating paper. It is important to reach and maintain several centric contacts, and to ensure incisal guidance using canine guide, or mutually protected occlusion to distribute the stresses toward the long axis of the implant, avoiding lateral forces in all mandibular movements.^6,16 

Lastly, we need to remember that SPS has the important disadvantage of promoting the adhesion of plaque, and consequently raises the risk of the onset and progression of peri-implantitis, especially in patients with a history of periodontal disease.^11,17  This means that, after a complete cycle of periodontal therapy, there should be no residual pockets with a PPD >5 mm, any open furcations should be healthy and easy to clean, and a full-mouth mean BOP <25% should be achieved. Patients must be carefully selected (nonsmokers with good oral hygiene and excellent compliance), and a well-established periodontal maintenance protocol must be rigorously imposed to guarantee the long-term success of this type of rehabilitation, avoiding the risk of rapid implant failure due to peri-implantitis developing in association with the short implant length.

Abbreviations

BIC

bone-implant contact

BOP

bleeding on probing

CBCT

cone-beam computerized tomography

GBR

guided bone regeneration

OPT

orthopantomography

PPD

probing pocket depth

SPS

sintered porous surface

The authors have no potential conflicts of interest to disclose in relation to the authorship and submission of this article.