|Year : 2020 | Volume
| Issue : 1 | Page : 43-46
Assessment of marginal bone level around immediately loaded single implant used to retain mandibular overdenture with bollard coping vs locator attachments
Mohamad H. Ismael Ph.D 1, Diab F. El-Haddad2, Osama A. Helaly2, Mohamad A. Quassem2
1 Department of Removable Prosthodontics, Faculty of Dentistry, October 6 University, October 6 City, Egypt
2 Department of Removable Prosthodontics, Faculty of Dentistry, Al-Azhar University, Cairo, Egypt
|Date of Submission||26-Oct-2019|
|Date of Acceptance||30-Jan-2020|
|Date of Web Publication||20-Jun-2020|
Mohamad H. Ismael
Removable Prosthodontics, Faculty of Dentistry, October 6 University, Cairo; Qalyubia, KafrShokr City,
Source of Support: None, Conflict of Interest: None
The aim of this study was to assess changes in marginal bone level around immediately loaded single implant used to retain mandibular overdenture with two different types of attachment (bollard coping and locator).
Patients and methods
Twenty completely edentulous patients were randomly selected from the Outpatient Clinic, Department of Removable Prosthodontics, Faculty of Dental Medicine, Al-Azhar University (Boys, Cairo). Patients were divided into two groups: Group I received single implant retained overdenture with a new design (bollard coping) attachment while group II received single implant retained overdenture with a locator attachment. Marginal bone loss around implant of both groups were evaluated by digital radiography with Digora software. Measurements were taken at baseline, 3, 6 and 12 months after implant insertion. Independent t-test was used for comparison between groups while the comparison of within each group by time was carried out by one-way analysis of variance followed by post-hoc Tukey test.
An acceptable range of bone loss in both groups with a statistically non-significant differences between both groups during the same follow up period was recorded. Bone loss values in both groups over time showed a statistically significant difference between 3 and 12 months and between 6 and 12 months values, however, there was no significance difference resulted from the comparison of 3 and 6 months values.
Bollard coping attachment is recommended to retain mandibular overdenture when using immediately loaded single implant. It was evidenced by less marginal bone loss around the implant when compared to those with conventional locator attachment during the same follow-up period.
Keywords: attachments, bollard, bone loss, implant overdenture, locators
|How to cite this article:|
Ismael MH, El-Haddad DF, Helaly OA, Quassem MA. Assessment of marginal bone level around immediately loaded single implant used to retain mandibular overdenture with bollard coping vs locator attachments. Tanta Dent J 2020;17:43-6
|How to cite this URL:|
Ismael MH, El-Haddad DF, Helaly OA, Quassem MA. Assessment of marginal bone level around immediately loaded single implant used to retain mandibular overdenture with bollard coping vs locator attachments. Tanta Dent J [serial online] 2020 [cited 2020 Oct 20];17:43-6. Available from: http://www.tmj.eg.net/text.asp?2020/17/1/43/287101
| Introduction|| |
Implant retained overdenture concept for treating completely edentulous patients seeking stable and well retained prosthesis was well documented and showed excellent results .
However, many patients cannot afford an implant therapy with two or more implants or do not want to undergo an extensive surgery. In order to reduce treatment time and treatment costs, the concept of immediate loading single mandibular implant in the edentulous mandible was introduced in the 1990 ,.
Many authors reported some problems associated with single implant overdenture treatment options, including a risk of potential vascular damage; also increased risk of midline denture fracture due to the limited amount of acrylic resin and increased space occupied by the attachment housing ,.
A wide variety of commercially available attachment systems is used to connect implants to overdenture; selection of attachment system depend on many factors among of them are anatomic situation of the ridge, desired level of retention, hygiene maintenance capability, and cost considerations .
Locator attachment offers several advantages including; dual retention, self-aligning, compensation for a misaligned implant, and availability of different levels of retentive forces obtained from the nylon male inserts .
Bollard coping attachment is a new resilient telescopic attachment employed in implant supported overdenture. Bollard coping consist of a metal coping with 6° convergence and a retention cap, to form an undercut. The Bollard coping is screwed to the implant abutment. Silicon is placed in the denture with retention achieved by engagement of the silicon to the undercut in the Bollard coping .
Still, there is a little available data in the literature about the effect of new attachment bollard coping and locator attachment as regard the amount of bone loss around single implant retained mandibular overdenture. So that this in-vivo study aimed at assessment of marginal bone level around immediately loaded single implant used to retain mandibular overdenture with bollard coping vs locator attachment.
| Aim|| |
This study was carried out to assess marginal bone level around immediately loaded single implant used to retain mandibular overdenture with bollard coping vs locator attachment.
| Patients and Methods|| |
Twenty completely edentulous patients with average age of 45–55 years free from any systemic diseases that might affect implant placement were randomly selected from the Outpatient Clinic, Department of Removable Prosthodontics, Faculty of Dental Medicine, Al-Azhar University (Boys, Cairo). Informed consent was obtained from all patients after an explanation of the methodology prior to enrolment in the study.
All patients were informed about the aim of this research and accepted to participate in it and written consent forms were signed from them according to the ethical committee of faculty of Dental Medicine, Al-Azhar University.
Prosthetic phase of the treatment
An acrylic complete denture was constructed for each patient following the conventional steps for complete denture construction with bilateral balanced occlusion concept. Any necessary adjustment of the denture and occlusion was carried out. Postinsertion instructions were given, and patients were instructed to wear the dentures till adaptation was acquired. Cone beam computerized tomography was taken for assessment the bone quality and dimensions at implant site, surgical guide stent was fabricated to assist implant insertion at its planned site.
Following single stage surgical protocol and by the aid of cone beam computerized tomography. Single dental implant fixture (Sky System, Bredent, Germany) with length 12 and 3.5 mm diameter were placed at midline of mandibular alveolar ridge. Patients were randomly allocated into two groups according to attachment used. Group I: patients received bollard coping attachment [Figure 1]. Group II: patients received locator attachment. The conventional acrylic complete dentures were converted into overdentures immediately retained by the single implant in both groups. Housings were created in the fitting surface of the dentures to receive silicon (1 mm) for bollard coping (group I); and the female part of the locator attachment (group II) using auto polymerizing acrylic resin.
Radiographic assessment of bone height around the implants was carried out by using standardized digital intraoral periapical radiographic images. It was carried out at the time of implant insertion, 3, 6 and 12 months after denture insertion. Rhinn technique was employed using the XCP instruments for extension cone paralleling techniques. These instruments consist of a bite block, directing rod and a guide ring. For infection control, a disposable plastic sleeve was fitted over the sensor and part of the cable, as the sensor cannot be autoclaved or disinfected then positioned with its long axis vertically. Thesensor was inserted into a slot in the bite block, and to ensure accurate re-positioning of the film every time the radiograph was taken, a putty rubber base bite was constructed for each patient when he/she closed his mouth on the bite block for localizing the film holder. So, the block could be removed and repositioned exactly in the same position in the patient's mouth every time. The radiographic tube was positioned flushing with the ring and the exposure was taken [Figure 2]. Time and dose of exposure were standardized in all patients. After the exposure, the image was displayed on the computer screen and stored on the patient card. The image was exported from the sensor software (OrisWin DG Suite v4.3; Fona, Assago, Italy) as greyscale image to be interpreted via DigoraOptime computerized system (Dfw 2.7, Digora, North Ossetia-Alania, Russia). The distance between the implant shoulder and first crestal bone-to-implant contact mesially and distally, represent the vertical level of bone around the implant.
Data were collected, tabulated, and statistically analyzed by SPSS 20 for windows (SPSS, Chicago, USA). The data distribution of normality was carried out by using Kolmogorov–Smirnov test. The test showed normal distribution of data and independent t-test was used for comparison between groups while the comparison of within each group by time was carried out by one-way analysis of variance followed by post-hoc Tukey test.
| Results|| |
Changes in marginal bone height around implants of both groups
The mean bone loss values (mm) recorded for both groups I (Bollard) and group II (locator) are showed in [Figure 3]. Independent t-test showed statistically nonsignificance difference at insertion and at 3, 6, and 12 months [Table 1].
|Figure 3: Line chart showing mean bone loss values (mm) along the follow-up intervals.|
Click here to view
Effect of time on bone loss in both groups
Regarding bone loss in both groups, there was a significant difference between the baseline reading and 3, 6, and 12 months readings. There was a significant difference between 3 months reading and 12 months reading, also there was a significant difference between 6 months reading and 12 months reading but there was no significance resulted from the comparison of 3 months reading and 6 months reading [Table 1].
| Discussion|| |
A meta-analysis showed that single implant supported overdenture is an alternative treatment option for edentulous mandible which ensure better retention with less cost and time of the treatment .
Implants were immediately loaded in this study in agreement with Attard and Zarb  who stated that immediate loading concept of implants in the anterior mandible reduce the treatment time with clinical results comparable with the delay loading concept.
Marginal bone changes around implants were measured by using standardized digital periapical radiographs as it has higher resolution with lower radiation dose rather than extra oral radiograph .
Long cone paralleling technique with customized film holder fabricated for each patient was carried out to ensure a standardized radiographic analysis . The film holder was used in the intraoral radiographic technique to ensure standardization of the measurements and to ensure a projection angle of 90° to the fixture axis, which resulted in maximum accuracy in controlling the marginal bone height .
The increase in bone loss with advance of time may be due to immediate bone response to healing and reorganization combined with functional stresses . The mean marginal bone loss values observed for both groups at the end of the follow up period (12 months) remain in the normal range of values reported in literature (not exceed 1 mm in the first year) .
Conversely, Alsabeeha et al.  found a lower rate of bone resorption (0.23 ± 0.44) when single midline implant immediately loaded with locator retained overdenture. The authors attributed the minimal bone loss to the dominance of basal bone known to be resistant to resorptive process.
When the two groups compared together during the same period of time, numerically marginal bone loss was higher in locator group than bollard group, but this difference was statistically nonsignificant. This may be due to the dual retention property of locator attachment which comes from friction between the inner and outer surface together with limited lateral and hinge movement. It may be responsible for transferring more loads to the implant, thus contributing to increased bone loss .
This results come in agreement with Celik and Uludag  who noted greater peri-implant stresses with locator when compared to ball and bar attachment.
| Conclusion|| |
Bollard coping attachment is recommended to retain mandibular overdenture with immediately loaded single implant. It has simpler fabrication technique and associated with less marginal bone loss around the implant than locator attachment during the same follow-up period.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]