|Year : 2022 | Volume
| Issue : 1 | Page : 31-37
Rehabilitation of edentulous posterior maxilla using lateral disc implants avoiding ridge augmentation in cases with inadequate bone height: A clinical evaluation
Sanjay Kumar Roy Chowdhury, R Arunkumar Shadamarshan, Rajkumar Krishnaprabhu
Department of Dental Surgery and Oral Health Sciences, Division of Oral and Maxillofacial Surgery, Armed Forces Medical College, Pune, Maharashtra, India
|Date of Submission||07-Sep-2021|
|Date of Decision||27-Feb-2021|
|Date of Acceptance||27-Feb-2022|
|Date of Web Publication||16-Jun-2022|
Dr. R Arunkumar Shadamarshan
Wangchuck Lo Dzong Military Hospital, Haa Dzong, Haa, Bhuan 15001
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Context: Implant-retained prosthodontic rehabilitation of the posterior maxilla is challenging owing to the compromised characteristics of the residual alveolar bone which might require several adjunctive surgical procedures to augment the available alveolar bone.
Aims: This study aims to evaluate the outcome of rehabilitated maxillary posterior edentulous space with lateral disc implants in subjects with inadequate bone height.
Subject and Methods: Forty patients with edentulous span in posterior maxilla with inadequate volume of bone were rehabilitated with lateral disc implant-retained prosthesis. Follow-up was undertaken at the end of 06, 12, 24, and 36 months by allocating the implants into the groups assessed according to the Misch Implant quality scale. A total of 6 Single disc, 22 Double disc, and 12 triple disc implants were placed.
Statistical Analysis Used: Descriptive statistics.
Results: At the end of 06 months, 96.6% were in Group 1, 3.3% were assessed to be in Group 2. At 12 months, 95% were in Group 1, 1.6% in Group 2, and 3.3% in Group 3. At 24 months, 95% were in Group 1, 3.3% were in Group 2, and 1.6% were in Group 3. At 36 months, 96.6% were assessed in Group 1 while 1.6% each was in Group 2 and 4.
Conclusions: A clinical success of 98.4% has been established and is concluded that Lateral disc implants provide a viable alternative to the contemporary management protocol involving a sinus lift.
Keywords: Lateral disc implants, Misch implant quality scale, sinus lift, trans-sinus implant placement
|How to cite this article:|
Roy Chowdhury SK, Shadamarshan R A, Krishnaprabhu R. Rehabilitation of edentulous posterior maxilla using lateral disc implants avoiding ridge augmentation in cases with inadequate bone height: A clinical evaluation. J Dent Implant 2022;12:31-7
|How to cite this URL:|
Roy Chowdhury SK, Shadamarshan R A, Krishnaprabhu R. Rehabilitation of edentulous posterior maxilla using lateral disc implants avoiding ridge augmentation in cases with inadequate bone height: A clinical evaluation. J Dent Implant [serial online] 2022 [cited 2023 Jan 29];12:31-7. Available from: https://www.jdionline.org/text.asp?2022/12/1/31/347662
| Introduction|| |
The replacement of missing teeth in the posterior maxilla is challenging in several aspects. Advanced jaw bone resorption may be seen in many cases. Not only does the width and height of the residual alveolar ridge reduce in width, but also the density of bone decreases dramatically making the placement of a conventional endosseous implant sometimes impossible. The maxillary sinus undergoes expansion after the loss of posterior teeth both inferiorly and laterally. Compounding this situation further is the preexisting periodontal disease and traumatic extraction procedures. Various options of bone augmentation exist for conventional implant placement. These include various onlay grafting, sinus floor elevation techniques using both lateral window and transalveolar methods, ridge split techniques, ridge expansion, guided bone regeneration techniques, distraction osteogenesis, etc. A common disadvantage to all these techniques is the increased treatment time, unreliable and uncertain increase in the dimensions of the alveolar process, and the increased cost. Several modifications in implant techniques have also been devised. The use of subperiosteal implants, short implants are some of them that circumvent additional surgical procedures for bone augmentation yet aids in implant-supported rehabilitation of the posterior maxilla. Basal osseointegrated implants are one of the recently developed and popularized alternatives for the rehabilitation of compromised edentulous posterior maxilla that derives its anchorage from the basal bones of the maxilla and mandible.
This technique enables the operators to place the implants of the desired dimension in a single sitting in the best-suited location without elaborate surgical procedures, thus reducing the total time of rehabilitation, with less morbidity and avoiding multiple surgical interventions at a reduced cost.
The aim of this study was to clinically evaluate the outcome of rehabilitated maxillary posterior edentulous space with lateral disc implants as oral prosthetic foundation in subjects with inadequate bone height for rehabilitation.
| Subject and Methods|| |
Forty willing subjects of the age group of 20–60 years of both sexes with edentulous span in posterior maxilla, who were medically fit with no systemic disease/condition, with good oral hygiene with periodontitis extending not beyond type I periodontitis, with minimum 10 months history of extraction/loss of tooth in the desired location, with maximum 4–6 mm of residual bone height in the edentulous span in posterior maxilla below the maxillary sinus, willing to follow-up for a minimum of 18 months' post rehabilitation with no habit of smoking or alcohol consumption were included in the study.
Cone-beam computed tomography (CBCT) was obtained (Newtom Cone Beam 3D Imaging Scanner) to assess the subantral level of the bone and the status of the buccal and palatal cortical plates, status of the maxillary sinus and its membrane, evaluation of septae, and the evaluation of the quality of bone in the subantral region [Figure 1]. The general dimensions and the respective coding of the implant (Victory Diskimplants® Monobloc cylindrical, Nice-France) were referred before the selection of the implant. The implant width is selected in such a way that the basal disc is in close contact with both the buccal and palatal cortex after placement. If the buccal cortex appears to be absent, the implant diameter is selected based on the involvement of the palatal cortex.
|Figure 1: Assessment of the subantral bone and the width of the alveolus in cone beam computed tomography sections|
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Since the subantral bone in the selected cases is always <6 mm, the transantral placement of the disc implants was undertaken. Informed consent was obtained from the patient. A prefabricated acrylic splint was kept ready to serve as a guide. Under local anesthesia, a crestal incision was placed and a buccal full-thickness mucoperiosteal flap was elevated to expose the buccal surface of the alveolar process till the required vertical height. The prefabricated acrylic stent was tried in the patients' mouth. The thickness of the gingiva was measured approximately and the cranial position of the respective high-speed lateral cutter was adjusted accordingly so that the implant abutment does not get submerged into the gingiva. The appropriate lateral cutter was used under continuous irrigation at 300,000 rpm (using an airotor) for the preparation of the lateral osteotomy [Figure 2]. The osteotomy site was inspected for any granulation tissue or sinus pathologies which may be removed in this step. The implant was tapped into the osteotomy site using the reverse side of a surgical osteotome and gentle malletting [Figure 3]. Complete submergence of the implant into the bone was ensured. The flap is reapproximated and a water-tight closure is obtained using nonresorbable sutures. The abutment is screwed onto the connector using the wrench and screws provided by the manufacturer [Figure 4]. Postoperative radiographs are taken to verify the position of the implant [Figure 5]. The implants were immediately loaded using contemporary prosthodontic protocols. A temporary crown was fabricated initially and replaced with a cemented definitive prosthesis [Figure 6]. Postoperative instructions regarding maintenance of oral hygiene, medications including antibiotics and analgesics were prescribed routinely. Patients were advised to avoid any activities that may increase the intra sinus pressure, including straining, blowing of the nose, and sneezing. Routine nasal decongestants, steam inhalation were given to maintain the patency of the ostium. Patients were advised to refrain from smoking and alcohol intake.
|Figure 4: Immediate postoperative photograph with the implant and abutment fixed|
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|Figure 5: Postoperative radiographs (inset shows the intraoral periapical radiograph)|
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|Figure 6: Rehabilitation with temporary crowns for immediate loading (Inset shows the lateral view of the rehabilitation)|
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Meticulous postoperative follow-up including radiographic examination was undertaken to assess the status of the implants at the end of 06 months, 12 months, 24 months, and 36 months [Figure 7]. Individual implants were allocated into the groups assessed according to the Misch Implant quality scale [Table 1]. Statistical analysis was carried out using SPSS Software 184.108.40.206 (IBM SPSS Statistics for Windows, Version 27.0 [IBM Corp, Armonk, NY]).
| Results|| |
A total of 40 patients (Males - 20; Females - 20) with an average age of 46.75 years were included in the study and a total of 60 implants (Males – 32; Females – 28) equally distributed between both sides were placed in these patients. The average age of males was 46.05 years and that of females was 43.65 years. The average subantral bone height on CBCT scans at the shortest portion was recorded to be 3.6 mm (standard deviation = 1.58). A total of 6 single disc implants, 22 Double disc implants, 12 triple disc implants were placed. Among the disc implants placed, 2 implants were of 5 mm diameter, 22 implants were of 7 mm diameter, 3 implants were of 8 mm diameter and 13 implants were of 9 mm diameter. The distribution of the specifications (Diameter and Number of discs) is shown in [Table 2]. On the assessment of the outcome based on the Implant quality scale [Table 1], at the end of 06 months, 58 implants (96.6%) were in Group 1, 2 implants (3.3%) were assessed to be in Group 2. At the end of 12 months, 57 implants (95%) were in Group 1, 1 implant (1.6%) in Group 2, and 2 implants (3.3%) in Group 3. At the follow-up of 24 months, 57 implants (95%) were in Group 1, 2 implants (3.3%) were in Group 2 and 1 implant (1.6%) was in Group 3. At the end of 36 months, 58 implants (96.6%) were assessed in Group 1 while one each (1.6%) were in Group 1 and 4. A clinical success rate of 98.4% has been established in the study [Table 3]. No patient was lost to follow-up.
| Discussion|| |
Partial edentulousness in the posterior maxilla has accounted for at least 36% of the cases reporting for the rehabilitation of partial edentulousness. This region undergoes the maximum resorption in terms of the width of the alveolar ridge and reduction in the bone density than any other region in the oral cavity. The absence of well-differentiated labial cortical along with the maximum magnitude of occlusal forces and the expansion of maxillary sinus after the loss of posterior teeth compounds the situation. The expansion of maxillary sinus occurs in inferior and lateral direction leading to a significant reduction in the sub-antral bone level. Preexisting periodontal diseases, systemic conditions, and surgical trauma during extraction can cause further reduction in the bone dimensions. The vertical subantral bone height is found to be <8 mm in 88.2% cases and <5 mm in 55% cases.
Several options exist for the rehabilitation of such compromised ridges including sinus augmentation followed by placement of conventional implants, subperiosteal implants, short implants, Zygoma implants, and Basal implants.
Sinus floor elevation using one of the two established procedures with or without immediate loading has long been the standard of treatment for the implant-mediated rehabilitation of compromised posterior maxilla. Standard protocol for sinus floor elevation and augmentation includes sinus floor augmentation through crestal osteotomy and immediate implant placement for a residual bone height of 7–9 mm, sinus augmentation through a lateral window approach, and immediate implant placement for a residual bone height of 4–6 mm and sinus augmentation through a lateral window approach and delayed implant placement for a residual bone height of 1–3 mm. Several studies have estimated a long-term success of implants ranging from 93% to 98% in sinus floor elevated and augmented maxillary sinus. However, this requires an additional surgical procedure with its attendant morbidities and complications including perforation of the sinus membrane, rhinosinusitis, and infection, hemorrhage. Not in all cases, simultaneous implant placement may be carried out. Therefore, increase in the rehabilitation time is a potential disadvantage of this technique which may take anywhere between 5 months (with autogenous bone graft) and 11 months (for other grafts) for healing and maturation of bone.
Subperiosteal implants are placed between the periosteum and the alveolar bone with screws. The success rate of such implants has been established at the range of 66% ± 8%.
Short Implants are those with the length of the endosseous component less than or equal to 8 mm. Finite element analysis of short implants have proven to concentrate the occlusal forces over the crestal bone than to the entire implant surface and consequently have been associated with poor long term results. It was demonstrated that short implants failed earlier than conventional osseointegrated implants with a survival rate of 88.1% at 168 months with the peak failure observed at 4–6 years. Although several studies have failed to demonstrate the increased failure rate of short implants compared with conventional implants with or without sinus floor elevation, no consensus has been attained on the use and success of those implants. However, immediate loading is not recommended in a short implant, especially in the posterior maxilla which demonstrates poor bone quantity, quality, and higher occlusal load. Some studies have reported a higher complication rate following the placement of short implants in the posterior maxilla than in other sites in the oral cavity.
Basal implants derive anchorage from the basal region of the jaws. Basal bone is an osseous framework found below the alveolar process, relatively stable, always present despite ongoing resorption, forms the load-bearing framework, more resistant to infection and resorption than the crestal bone. There are basically two types of basal implants: Basal cortical screw implants and lateral basal implants, the latter ones have been put into use in our study. For the purposes of elaboration and discussion, these two types have to be dealt together, in spite of a different design, the concept remains the same with subtle differences.
The basal implants are indicated where immediate loading is anticipated, compromised vertical and horizontal dimension of the alveolar process, and also as a second option in failed conventional endosseous implants and/or bone augmentation procedures. No absolute contraindication exists specifically for basal implant mediated rehabilitation. A failure to achieve balanced masticatory forces in a completely edentulous patient may be considered a relative contraindication due to the chances of failure of these implants in the immediate loading protocol. Osseointegration in basal implants has been demonstrated during its removal in a patient before undergoing radiotherapy. Tetracycline labeling, microradiography, and light microscopic studies have demonstrated bone formation at the surface of these titanium implants.
The insertion of the lateral disc implants is made through an osteotomy that is prepared using an airotor at 300,000 rpm. Although it is well-established that a temperature of more than 44°C causes irreversible bone tissue injury, the use of a pure Titanium cutting disk at 300,000 rpm with continuous cooling produces a local temperature of only 32 C, causing no bony changes.
Disc implants impart physiological elasticity between the cortical bone structures, similar to the presence of natural teeth. Any basal implant with a basal load transmitting disc of <9 mm diameter and more than 0.6 mm thickness is considered to be rigid. Increasing the diameter and reducing the thickness of the disc increases the elasticity while increasing the number of discs per implant, thickness of the bar, shaft, and ring reduces the elasticity. The elasticity imparted to the bone should not disrupt the primary stability and hinder the osseointegration.
The contact of the implant between the buccal and the palatal cortex offers excellent stability aiding in immediate loading, thereby reducing the need for a transient removable partial denture, leading to increased vascular supply, healing of bone and periosteum, and better chances at osseointegration. By virtue of the well-polished vertical portion, the basal cortical screw implants show lesser crestal bone loss than conventional implants and reduce the chances of peri-implant infection. These implants are less technique sensitive to place but due to the inherent protocol of immediate loading and rehabilitation that this implant offers, the surgical procedure along with the immediate prosthodontic rehabilitation takes longer appointments but less number of appointments. An estimated 50% reduction is envisioned since no adjunctive bone augmentation procedures are required for the placement of these implants in compromised ridges. The incidence of periimplantitis has also been reported to be reduced by 98% in basal implants when compared with conventional endosseous implants.
The main disadvantages of the lateral basal disc implant are that it requires flap elevation with its attendant complications.
The trans-sinus placement of the disc implant stems from the thought process of assessing the outcomes of postfracture osteosynthesis screws that are routinely found inside the sinus, Zygoma implants which transverse a large portion of the sinus membrane, complete disintegration of the anatomy of maxillary sinus post-Le fort I osteotomy. Concepts do exist against the implementation of sinus augmentation techniques due to the increased frequency of sinus pathologies that are seen in ENT literature, postoperative sinusitis, and other complications that may hinder the outflow of the sinus. It has also been stressed that according to Frank's law of flexural deformation of bone, even if the internal maxillary sinus wall is augmented to a concave surface, the expansion will occur in due course to make it convex, thus resorbing the augmented bone.
Meticulous postoperative care of a trans-sinus placement is important. It is important to maintain a patent ostium at the hiatus which theoretically suffices the drainage of infection.
The success rate of these implants has not been established accurately due to the lack of long-term studies and systematic reviews. Scortecci conducted a clinical trial to evaluate the safety and efficacy of immediately loading a fixed implant-supported prosthesis without bone augmentation in moderately to severely resorbed, completely edentulous maxillae. Over a 41-month period, 783 titanium implants (627 laterally inserted disk implants, with or without 156 axially inserted Structure implants) were placed in 72 consecutive patients with completely edentulous maxillae using an immediate loading protocol. Six months postoperatively, 98% of the implants were radiologically and clinically osseointegrated. All of the fixed prostheses remained functional, and no additional implants were lost. This closely resembles our result of the clinical success rate of 98.2% at the end of 12 months. Further studies are required to accurately establish the success of these versatile implants specifically comparing it with the present standards of treatment that exist in these scenarios.
| Conclusion|| |
It can be concluded that the trans sinus osseointegrated lateral disc implants provide a viable alternative to the contemporary management protocol followed for the rehabilitation of compromised edentulous posterior maxilla without the necessity of elaborate adjunctive surgical procedures for the augmentation of subantral bone leading to reduced morbidity, cost, and overall treatment time. However, the long-term randomized studies are required to establish this as a standard of treatment.
We would like to thank Mr. DR Basannar M.Sc., MPS, Scientist “F,” Department of Community Medicine, Armed Forces Medical College for the statistical help provided for the design, execution, and interpretation of the study.
Financial support and sponsorship
This paper is based on Armed Forces Medical Research Committee Project No 4823/2016 granted by the office of the Directorate General Armed Forces Medical Services and Defence Research Development Organization, Government of India.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2], [Table 3]