Journal of Dental Implants

ORIGINAL ARTICLE
Year
: 2020  |  Volume : 10  |  Issue : 2  |  Page : 72--77

Lateral incisors versus canine areas for two implant placements used to retain mandibular overdenture: Periodic monitoring of ridge base contact relation


Khloud Ezzat Mourad1, Radwa Mohsen Kamal Emera1, Wael Ahmed2, Ahmed Habib1,  
1 Department of Removable Prosthodontics, Faculty of Dentistry, Mansoura University, Mansoura, Egypt
2 Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Mansoura University, Mansoura, Egypt

Correspondence Address:
Dr. Khloud Ezzat Mourad
Department of Removable Prosthodontics, Faculty of Dentistry, Mansoura University, Mansoura
Egypt

Abstract

Purpose: This study aimed to compare the effect of two different implants' position (lateral incisors and canine areas) to retain mandibular complete overdenture on the ridge base contact relation after 6 months of overdenture use. Materials and Methods: Ten completely edentulous patients were selected from the Outpatient Clinic of Removable Prosthodontics Department, Faculty of Dentistry, Mansoura University. According to the position of implant placement, patients were randomly classified into two equal groups; Group I where two implants were placed in the lateral incisors' area and Group II where two implants were placed in the canines' area. Positioner attachment was connected to the implant fixture to retain the mandibular implant overdenture. Periodic monitoring of ridge base contact relation was carried out at the time of insertion (T0) and 6 months (T6) later using cone-beam computed tomography (the dual scan technique procedures). Results: There was a statistically insignificant difference between the two groups (lateral incisors' position group and canines' position group) regarding the ridge base contact relationship. Conclusion: Within the limitations of this study (patient number and study period), the ridge base relationship of two implants retained mandibular overdenture is maintained regardless of the implants' position.



How to cite this article:
Mourad KE, Kamal Emera RM, Ahmed W, Habib A. Lateral incisors versus canine areas for two implant placements used to retain mandibular overdenture: Periodic monitoring of ridge base contact relation.J Dent Implant 2020;10:72-77


How to cite this URL:
Mourad KE, Kamal Emera RM, Ahmed W, Habib A. Lateral incisors versus canine areas for two implant placements used to retain mandibular overdenture: Periodic monitoring of ridge base contact relation. J Dent Implant [serial online] 2020 [cited 2021 Jan 24 ];10:72-77
Available from: https://www.jdionline.org/text.asp?2020/10/2/72/303918


Full Text

 Introduction



The conventional complete denture has been the only treatment option for completely edentulous patients for many years. Although many patients were satisfied with their dentures, some problems appeared, especially with the lower denture, such as insufficient retention and stability, decreased chewing efficiency, and caused discomfort during mastication due to mobility of the denture.[1],[2] Using a dental implant to assist mandibular overdenture can improve the quality of life for the patient as it can improve the prosthesis retention and stability with subsequent improvement of patient satisfaction.[3]

According to Misch, to develop a treatment plan for implant overdenture, the final prosthesis should be determined according to the necessary retention, support, and stability required for the prostheses. For implant overdenture, the amount of retention is related to the number and type of overdenture attachment. The stability is more related to the implant position and the support is primarily related to the implant number and distribution.[4]

It was found that there is an interaction between the implant location and the achieved retention and stability of the two-implant retained overdenture. Furthermore, the correlation between the direction of the force and the implant location was confirmed.[5]

When an overdenture is retained by two anteriorly placed implants, this overdenture derives its major support from the residual ridge tissue. Good adaptation and fitting of the implant overdenture to the tissue is necessary to avoid unfavorable denture movement with subsequent undesirable stresses to the tissue and the implants. Posterior tissue changes under the tissue-supported implant overdenture may lead to loss of fit and adaptation between the overdenture and the ridge tissue.[6],[7]

Using a resilient connection between the implants and the overdenture allows for movement between the denture and the implant. The movement is achieved at the expense of mucosal resiliency so that most of the load is absorbed by the alveolar ridge.[8],[9]

In case of two implant-retained overdenture, the implants act as a fulcrum, with anterior and posterior lever arm, subsequent rotational movement may occur around it when force is applied. However, the primary and secondary bearing areas of the overdenture will resist occlusal forces placed on the posterior lever arm, but forces on the anterior lever arm such as incisive movements may cause more noticeable rotation. Hence, it was supposed that by moving the implants from the canine to the lateral incisor position, the effective anterior lever arm is reduced, thus minimizing the tipping forces on the overdenture.[10]

Changes that occur after denture insertion affect the residual ridge both hard and soft tissue. When the soft-tissue mucosa below the denture base is compressed, the blood supply that provides nutrients and removes metabolites from the bone can be affected, possibly leading to resorption.[11] Subsequently, the aim of this study was to compare the effect of the two implant positions (lateral incisors and canine areas) on the ridge base contact relation after insertion of the implant overdenture insertion.

 Materials and Methods



Ten healthy completely edentulous patients were selected from the Outpatient Clinic of Removable Prosthodontics Department, Faculty of Dentistry, Mansoura University, according to the following inclusion criteria: all patients had maxillary and mandibular residual alveolar ridges that covered with healthy mucosa, without any remaining roots or local inflammation and sufficient residual alveolar bone quantity (height and width) and quality (normal trabecular pattern) in the interforaminal area to receive implants verified by cone-beam computed tomography (CBCT) for each patient. Patients had Angel's Class I maxillomandibular relation and sufficient restorative space that was detected by tentative jaw relation. The patients were healthy and free from any systemic diseases that may affect the bone health such as uncontrolled diabetes mellitus and osteoporosis. Exclusion criteria that were considered were the presence of a history of parafunctional habits (bruxism and clenching), smoking and alcoholism, local or general contraindications for surgical procedures, TMJ or neuromuscular disorders, and history of radiation therapy in the head and neck region.

This research protocol was approved by the Faculty Ethical Committee. After the patients were informed about the treatment plan and the need for frequent recalls, they signed written consents.

Presurgical procedures

All patients received conventional maxillary and mandibular complete dentures. Mandibular complete denture for each patient was duplicated into clear acrylic resin to construct the surgical stent. Using the milling machine, two parallel holes corresponding to the final drill diameter were drilled at the intended implant positions (at the canines or lateral incisors' area). Metal tubes were attached at the drilled holes to guide drilling during surgery. The surgical stent was then sterilized to be ready for use.

Patients grouping

Selected patients were divided into two groups according to the implants' position: Group A: received two implants at the mandibular canines' area. Group B: received two implants at the mandibular lateral incisors' area. Each patient received two implant fixtures (Dentium SuperLine, Dentium, Co. Ltd., Korea) of (12 mm length and 3.4 mm diameter) using the two stages of the surgical protocol.

Prosthetic procedures

After 3 months of the osseointegration period, two circular incisions were made at the cover screw area using the tissue punch. Cover screws were unthreaded using the screwdriver and the healing abutments (Dentium, Co. Ltd., Korea) (diameter 4 mm and height 3 mm) were screwed over each fixture for 2 weeks to allow healing of peri-implant tissue. After healing of peri-implant tissues, healing abutments were unscrewed and the positioner abutments (Dentium, Co. Ltd., Korea) (3.5 mm diameter and 3 mm height) were screwed in position using the screwdriver [Figure 1]a and [Figure 1]b. The positioner socket set was incorporated in the denture by the direct pickup procedures.{Figure 1}

Cone-beam computed tomography assessment procedures

For each patient, periodic monitoring of the ridge base relation was performed using the dual scan procedures twice at T0 and T6 where the first scan (T0) was done 1 week after pick up to permit denture settling, and the second one (T6) was done after 6 months. The dual-scan procedures include four stages.

Preparation of the mandibular denture to scan

A caliper was used to determine the position of three fixed dimples to be opposite to the central fossa of the lower 2nd molar (R1), lower 1st molar (R2), and mesial fossa of the lower 2nd premolar (R3) on the right side and the same points (L1), (L2), and (L3) on the left side. These small rounded shallow dimples, with a diameter of 2 mm, were prepared on the crest area of the fitting surface of the mandibular overdenture using rose head bur number 5. Then, gutta-percha was incorporated on each one to act as radio-opaque maskers [Figure 2].{Figure 2}

The first scan procedures (patient and denture scan)

The first scan (i CAT next generation, Imaging Science International, Hatfield/PA/USA) was done to obtain an image of the patient's mandible and the denture so it was done while the patient was wearing the prosthesis with gutta-percha markers that were positioned away from positioner metal socket. This scan is done while the patient biting on a silicone bite index.

Preparation of the patient

The patient was positioned in a seated position with the head upright. He/she was asked not to move during procedures to avoid artifacts that compromise the reformatted images.

Alignment of the patient

To achieve correct alignment, the transaxial CT slice plane should be parallel to the occlusal plane. Stabilizing the relationship of the jaws during the scan was done using a bite registration index made of a radiolucent silicone.

The scanning instruction

The entire prosthesis should be included in the scan so that the prosthesis up to the level of occlusal plane will be visible in the image. This was achieved by positioning the first slice just below the inferior border of the mandible, while positioning the last slice just above the artificial teeth of the overdenture. The scan radiation was adjusted at 120 KV, 5 mA, and 0.25 voxel for 14.7 s.

The second scan procedures (prosthesis scan)

For accurate positioning, the prosthesis was placed in the same way as it was positioned in the patient mouth during the first scan. Hence, the prosthesis was positioned in the CBCT scanner with a right–left orientation that matches the right–left orientation of the prosthesis in the first scan. The scan radiation was adjusted at 120 KV, 5 mA, and 0.125 voxel for 14.7 s [Figure 3].{Figure 3}

Reconstruction of the images

Using software*, images of the 1st and 2nd scan were superimposed over each other. Superimposition was done by placing the gutta-percha markers on the denture on the gutta-percha markers appeared on the 1st scan [Figure 4].{Figure 4}

Measurements

On the reconstructed images, the ridge base relation was measured by measuring the distance between the alveolar bone and the denture base. This was done using the “ruler” tool, from the measure tools on the software, to measure the distance from each radio-opaque point, that represent the denture base, to the crest of alveolar bone [Figure 5]. These distances were measured 1 week after pick up to have the data of (T0) and after 6 months to record data of (T6). All data were tabulated and statistically analyzed.{Figure 5}

Statistical analysis

Shapiro–Wilk test was used to verify the normal distribution of data owing to the small sample size of the patients. The data were nonparametric and violated the normal distribution. To compare the difference in ridge base distance between groups, and sides, the Mann–Whitney test was used. The nonparametric Kruskal–Wallis test was used to compare the difference in ridge base distance between the second premolar, first molar, and second molar positions. This comparisons were done to find If significant differences were detected. P value is significant if it was < 0.05. The data were analyzed using SPSS (SPSS Inc., Chicago, Illinois, USA) (statistical package for the social sciences).

 Results



Comparison of the difference in ridge base distance between groups:

Descriptive statistics of difference in ridge base distance for groups are presented in [Table 1]Positive sign and negative sign indicate changes in the ridge base distanceExcept the second premolar area, the canine group showed decreased distance at different sites for the right and left sides. However, the lateral incisor area showed increased distance at different sites for the right and left sidesComparison of the difference in ridge base distance between groups is presented in [Table 1]The mean distance from the denture base to the crest of the ridge was increased or decreased insignificantlyThere was no significant difference between groups at each position and each side (Mann–Whitney test, P > 0.05).{Table 1}

Comparison of the difference in ridge base distance between positions:

Descriptive statistics of difference in ridge base distance for positions are presented in [Table 2]Positive sign and negative sign indicate changes in the ridge base distanceThe first and second molar areas at the right side of the canine group showed decreased distance. However, the second premolar area at the right side of the canine group and all areas at the right and left sides of the lateral incisor group showed increased distanceComparison of the difference in ridge base distance between positions is presented in [Table 2]There was no significant difference between positions at each group and each side (Kruskal–Wallis test, P > 0.05).{Table 2}

Comparison of the difference in ridge base distance between sides:

Descriptive statistics of difference in ridge base distance for sides are presented in [Table 3]Positive sign and negative sign indicate changes in the ridge base distanceThe right and left sides of the canine group showed decreased distance except the second premolar position at the right side. However, the right and left sides of the lateral incisor group showed increased distance at all positionsComparison of the difference in ridge base distance between sides is presented in [Table 3]There was no significant difference between sides at each group and each position (Mann–Whitney test, P > 0.05).{Table 3}

 Discussion



The two implants' location at the lateral incisors' area and canines' area was applied in this study, for two–implants retained overdenture, to evaluate the effect of these two locations on the ridge base contact relation.

It was concluded that the bone remodeling activity beneath the denture base of the mandibular 2-implant overdenture was predominantly shown posteriorly in the molar region.[12] This was agreed with Topkaya and Solmaz, where they found that the molar region is the most affected region with the chewing forces so posterior changes beneath the implant overdenture are more predominant.[13]

According to Scherer et al.,[14] soft-tissue changes, attachment wear, and alveolar ridge resorption occur in the patient mouth overtime. As these changes occur, the prosthesis may no longer be well adapted to the tissues and rotational movement around the implants may occur. This change could change the biomechanical status from Class 2 to Class 1 lever and the implant consequently may become the fulcrum point as opposed to the anterior residual ridge.

This study showed a statistically insignificant difference in the ridge base relation, measured from the base of the denture to crest of the alveolar bone, regardless to the implant location. This means that within the follow-up period of this study, the effect of lever arm length was not effective in the observed ridge base relation. Moreover, from a biomechanical point of view, this study followed definite pressure impression technique, positioner attachment, and functional pick up of the attachment components.

It was concluded that the definite pressure impression technique evenly distributes the functional load along the residual alveolar ridge.[15] Positioner attachment used in this study provides a resilient connection between the prosthesis and the implants. It was found that the resilient attachments allowed the decrease of stress transmission throughout the implants. They also decreased the loads in the bone around the implant during the mastication loading process. Thus, it was concluded that the resilient attachments allow for a more even load distribution between the denture bearing surfaces and the dental implants.[16],[17] Daher.[18] found that the functional pick up of the attachment can be made in a passive-loaded environment to ensure complete seating of the denture on the supporting tissues.

 Conclusion



Within the limitations of this study (patient number and study period), the ridge base relationship of two implant-retained mandibular overdenture is maintained regardless to the implant position.

Recommendation

According to the results of this study, extended follow-up period and larger sample size are recommended to evaluate the effect of two implant positions; in the lateral incisors versus the canine areas; on the ridge base contact relation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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