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Year : 2015  |  Volume : 5  |  Issue : 1  |  Page : 82-86

Prosthetic recovery utilizing residual dental implants: A case report involving a unilateral milled-bar-magnet attachment combination

Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Ken Dentalx, Tokyo, Japan

Date of Web Publication2-Apr-2015

Correspondence Address:
Shinji Kuroda
Department of Oral Health Sciences, Tokyo Medical and Dental University, 1-5-45, Bunkyo-ku, Yushima, Tokyo 113-8549
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0974-6781.154456

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Few options for functional recovery using residual dental implants are available after removal of disintegrated implants. This report describes the application of a maxillary implant-supported removable partial denture (RPD) retained by a unilateral milled-bar-magnetic attachment combination fixed to the remaining two implants as an alternative for functional recovery without surgery. A custom milled-bar with keepers was fixed to the two remaining unparallel unilateral implants in a 78-year-old woman who visited our department after dental implant treatment. Although 2 of the 4 initial implants were lost, additional surgery was unfeasible; thus, a magnetic RPD with a clasp on the ipsilateral second molar was placed. Peri-implant infection and bone resorption did not occur in the 4 years after implant-supported RPD placement. In the present case, a custom milled-bar-magnetic attachment and a clasp combination have been effective for retaining an implant-supported RPD even with an inadequate unilateral design.

Keywords: Attachments and clasp combination, implant-supported removable partial denture, unilateral attachment design

How to cite this article:
Nakata H, Kuroda S, Takushima H, Kasugai S. Prosthetic recovery utilizing residual dental implants: A case report involving a unilateral milled-bar-magnet attachment combination. J Dent Implant 2015;5:82-6

How to cite this URL:
Nakata H, Kuroda S, Takushima H, Kasugai S. Prosthetic recovery utilizing residual dental implants: A case report involving a unilateral milled-bar-magnet attachment combination. J Dent Implant [serial online] 2015 [cited 2019 Sep 22];5:82-6. Available from:

   Introduction Top

The frequent application of dental implants to meet the increasing demand of patients has increased the number of treatable cases but also raised the number of complications. [1],[2],[3],[4] Reports on the therapeutic options after implant loss mostly discuss the mechanisms of failure and propose surgical corrective methods. [5],[6] However, implant replacement is contraindicated in elderly patients who cannot perform adequate self-care, those with systemic diseases, and patients refusing additional surgery. Further, loss of even a single implant can make oral rehabilitation difficult if the number of implants used was the minimum required. Various studies and clinical reports have focused on the benefits derived from implant-supported fixed prosthesis and removable overdenture, and discussed on individual characteristics; [7],[8],[9],[10] however, only a few reports on the use of multiple attachments with implant-supported overdenture (IOD) as an alternatives of functional recovery utilizing residual implants have been published. Here, we describe a case of the application of a maxillary implant-supported removable partial denture (RPD) retained by a unilateral milled-bar-magnetic attachment combination and a clasp after two contralateral implants disintegrated.

   Case report Top

In March 2008, a 78-year-old Japanese woman visited our hospital with a chief complaint of skin rash and redness on the face and neck after dental implant treatment [Figure 1]. She had a history of cerebral infarction (around 2003), osteoarthritis (both legs), but no notable family history and smoking history.

At another clinic, in June 2007, she had undergone placement of four implants (Brånemark MK III RP, ö4 mm × 15 mm; Nobel Biocare, Göteborg, Sweden) in the maxilla based on the All-on-4 treatment concept. [11] However, when the final prosthesis was attached, one implant had disintegrated and was removed. Ultimately, the final prosthesis was fixed to three residual implants positioned at 3, 8, and 12. A metal crown covered 14 [Figure 2].
Figure 1: Skin rash and redness extending from the face to the neck were observed

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Figure 2: Initial panoramic radiograph showing the final prosthesis attached to three implants (March 2008)

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To determine the cause of the cutaneous symptoms, drug lymphocyte stimulation test, and patch test were conducted at the Dental Allergology Clinic in our hospital. Allergies to the ingredients of the fixture and the prosthesis such as titanium, palladium, gold, and cobalt were excluded.

In June 2009, the patient developed pain and swelling in the maxillary right molar region. When the prosthesis was removed, the implant at 3 was lost spontaneously. Interestingly, the cutaneous symptoms disappeared afterward. Of the remaining implants on the left side, the one at 12 had a distal angulation of 30° and the other was perpendicular to the anterior maxilla, and the patient refused additional surgery. In November 2009, to correct the angulations and connect the implants, a combination attachment consisting of a custom milled-bar with three magnetic keepers welded to its upper part was fixed to the implants by using 35-Ncm torque [Figure 3]. Then, an implant-supported RPD with three magnets (Magfit® IP-B Flat Type, Aichi Steel Corporation, Aichi, Japan) and a clasp for 14 was placed.
Figure 3: Panoramic radiograph obtained after the milled-bar was attached (December 2009)

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During the 4 years follow-up, the clinical course was uneventful [Figure 4]a-c. Occlusal conditions were assessed with the Dental Prescale (Fujifilm Corporation, Tokyo, Japan) 3 times, and no major problem was found [Figure 5]. In addition, the cutaneous symptoms did not relapse [Figure 6]. The patient is very satisfied with the therapeutic outcomes.
Figure 4: Appearance of the unilateral milled-bar-magnetic attachment combination (a) and implant-supported overdenture 4 years after loading (b and c)

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Figure 5: Evaluation of occlusion at 4 years after loading by using the Dental Prescale

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Figure 6: The cutaneous symptoms did not relapse and the rough skin around the eyes and lips healed completely (February 2014)

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   Discussion Top

 Bar-and-clip systems, magnetic attachments, locators, and ball attachments are commonly used for retaining IODs. [12],[13],[14] Various studies on their design, [15],[16] position and number of magnetic attachments contributing to retention, [17] stress distributions at the bone-implant interface, [18] and literature reviews [19] have been reported. Locators and magnetic attachments allow angular correction of unparallel implants; [20],[21] however, they cannot correct angular differences of approximately 30° between implants placed according to the All-on-4 treatment concept. As ball attachments provide virtually no angular correction, strict parallelism of implants is required. Further, in bar-and-clip systems, mesiodistal parallelism of implants is not a major issue, however, the clip can rotate, and adequate maxillary denture retention is difficult in unilateral design. To avoid these problems, we joined the two unparallel implants on the left side by using a custom milled-bar and retained the implant-supported RPD with three magnetic attachments instead of a clip; the clasp at 14 was also retentive.

Among the aforementioned attachment designs, magnetic attachments have the weakest retentive force. [22] Because only vertical suction is applied and grip is absent, retention by a magnetic attachment is mainly attributable to the properties of the magnetic assembly, whose retentive force disappears when the denture moves laterally. [23] In the present case, the magnetic keepers were embedded in the custom milled-bar, ensuring adequate grip, and lateral denture movement was restricted by the clasp on 14. Therefore, the vertical force generated by the magnetic attachments was considered sufficient for retaining the implant-supported RPD. We estimated the occlusal support and force distribution by using Dental Prescale. [24] The results showed no abnormality in occlusal force [Table 1].
Table 1: Evaluation of occlusions and comparison of right and left occlusal areas, pressure, and force by using the dental prescale at 4 years after loading. The test was performed three times in the same condition, and the mean value is shown in the table

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The cutaneous rash, which was the chief complaint, improved when the second implant was lost, and the patient's skin healed completely [Figure 6]. Chronic inflammation around the implant might have caused the cutaneous rash and redness. According to Minegishi and Saito, [25],[26] mild inflammation caused by streptococci in the oral cavity might induce allergy-like dermatitis. This view is supported by case reports and reviews that described dermatitis caused by mild inflammation. [27],[28] Importantly, the finding suggests that good oral hygiene and prevention of chronic inflammation are necessary not only for implant survival but also for general well-being.

Pramod Kumar et al. [29] presented a case in which a ball attachment and milled-bar were used in a partially edentulous mandible. Similarly, Kim et al. [30] used a combination attachment consisting of a locator and milled-bar to retain a mandibular IOD. Reviews and clinical studies have evaluated this technique. [31],[32],[33] Our case shows that a prosthetic design, including such combination attachments is acceptable for minimally invasive recovery procedure and may provide high satisfaction even though implant replacement is not possible because of various reasons.

   References Top

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]

  [Table 1]


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