Prosthodontic considerations for the transmandibular implant

Anterior Hyperfunction by Mandibular Anterior Teeth: A Narrative Review

"Combination syndrome", defined by Kelly in 1972, is a challenging condition observed in a patient with an edentulous maxilla and a partially edentulous mandible with only mandibular anterior teeth. "Anterior hyperfunction syndrome" is regarded as a synonym of combination syndrome and was first described in 1994. Although these terms have been well known, the definition of "anterior hyperfunction" has not been described yet. This narrative review focused on anterior hyperfunction and discussed the etiology and the clinical managements. An electronic bibliographic search for this literature review was conducted in addition to the review of our clinical cases. The previous reports indicated that combination syndrome with all five features was rarely observed. The patients with anterior hyperfunction generally showed the loss of posterior occlusal supports and the loss of vertical dimension of occlusion. To manage anterior hyperfunction, these conditions should be improved using conventional removable prostheses and implant-supported prostheses. Anterior hyperfunction is attributed to mandibular anterior teeth and some interventions for mandibular anterior teeth are required in many cases. Additionally, it must be noted that implant-supported prostheses may lead to anterior hyperfunction. In conclusion, comprehensive approaches for the remaining teeth and the prostheses will be required to manage this complex condition.

"Combination Syndrome" in an Upper/Lower Implant Overdenture Patient: A Clinical Report

An upper/lower overdenture case, which presented with clinical entities commonly associated with the combination syndrome, is described. To the author's knowledge, this is the first documented case to illustrate such a particular association. The patient presented with an upper overdenture on 4 individual implants with attachments, without palatal coverage, opposing a lower bar overdenture on 4 implants, delivered more than 10 years before presentation. The patient complained about esthetics (poor display of upper teeth, excessive showing of lower teeth, and occlusal plane cant) and chewing. The anterior maxilla had severe bone loss, whereas the anterior mandible had a large amount of bone. Our retreatment included an upper overdenture with palatal coverage and a lower overdenture, both prostheses supported by individually attached implants. The article describes in detail the reasoning behind chosen retreatment, along with limitations and compromises.

Mandibular Implant-Retained Overdentures: Potential Accelerator of Bone Loss in the Anterior Maxilla?

PURPOSE

To compare the residual ridge resorption (RRR) of the anterior maxillary bone beneath complete dentures when opposed by mandibular complete dentures (CD) and implant-retained overdentures (IRO).

MATERIALS AND METHODS

18 patients were rehabilitated with maxillary CD opposing mandibular IRO, and 4 patients were prescribed with conventional CD. Cone beam computed tomography (CBCT) scans of the maxilla were acquired before and 1 year post-treatment and converted into 3D models using Mimics research software. RRR was quantified by measuring the changes in bone volume following superimpositioning and sectioning of these models at the anterior maxillary region. Subsequently, the sectioned 3D models of the anterior maxilla were exported to 3-Matic software to reveal the predominant region and depth of RRR.

RESULTS

The mean reduction in bone volume of the anterior maxilla in the CD group was 2.60% (SD = 1.71%, range = -4.89 % to -0.92%, median = -2.30%), while the mean reduction in the IRO group was almost three times higher at 7.25% (SD = 3.16%, range = -13.25 to -1.50, median = -7.15%). The predominant areas of RRR were on the buccal and occlusal ridge of the anterior maxilla.

CONCLUSION

Within the limits of this study, it may be concluded that an IRO caused significantly higher RRR of the anterior maxilla than a CD.

Prosthetic management of an existing transmandibular implant: A clinical report

This report describes the prosthetic management of a fractured Dolder bar on a transmandibular implant system. The patient declined surgical removal of the implants. Therefore, to repair the superstructure, a cast Dolder bar was fabricated and luted onto the existing transmandibular implants. An implant-retained bar overdenture was then fabricated to rehabilitate the mandibular arch.

The influence of resilient liner and clip attachments for bar-implant-retained mandibular overdentures on opposing maxillary ridge. A 5-year randomised clinical trial

This study aimed to compare the influence of resilient liner and clip attachments for bar-implant-retained mandibular overdentures on opposing maxillary ridge after 5 years of denture wearing. Thirty edentulous male patients (mean age 62·5 years) received two implants in the anterior mandible after being allocated into two equal groups using balanced randomisation. After 3 months, implants were connected with resilient bars. New maxillary complete dentures were then constructed, and mandibular overdentures were retained to the bars with either clips (group I, GI) or silicone resilient liners (group II, GII). The prosthetic and soft tissue complications of the maxillary dentures were recorded 6 months (T6 m ), 1 year (T1), 3 years (T3) and 5 years (T5) after overdenture insertion. Traced rotational tomograms were used for measurements of maxillary alveolar bone loss. The proportional value between bone areas and areas of reference not subject to resorption was expressed as a ratio (R). Change in R immediately before (T0) and after 5 years (T5) of overdenture insertion was calculated. Maxillary denture relining times and frequency of flabby anterior maxillary ridge occurred significantly more often in GI compared with GII. The change of R in anterior part of maxilla was significantly higher than change of R in posterior part in both groups. GI showed significant resorption of anterior residual ridge compared with GII. Relining times and frequencies of flabby ridge were significantly correlated with change in R. Within the limitations of this study, resilient liner attachments for bar-implant-retained mandibular overdentures are associated with decreased resorption and flabbiness of maxillary anterior residual ridge and fewer maxillary denture relining times when compared with clip attachments.

Assessment of the prevalence index on signs of combination syndrome in patients treated at Bauru School of Dentistry, University of Sao Paulo

A group of destructive changes occurring in jaws in patients with maxillary complete dentures and mandibular removable partial dentures (bilaterally) has been described in the literature as the combination syndrome. However, this condition is not clinically observed in all patients. The aim of this study was to establish the prevalence index on signs of combination syndrome and to verify whether these changes also occurred in patients rehabilitated with a mandibular removable partial denture (unilaterally). Sample was composed of 44 patients, completely edentulous in the maxilla. Thirty-two patients had a Kennedy Class I removable partial denture and 12 a Kennedy Class II. Three major alterations were observed in 20.5% of the studied population. Nevertheless, these changes were present only in 25% of patients with Kennedy Class I removable partial denture. Based on the findings of this study, it can be concluded that patients with Kennedy Class II removable partial denture do not have similar signs that lead to the combination syndrome's condition.

Incorporation of growth factors into medical devices via biomimetic coatings

Orthopaedic and dental surgeons are fully aware of the need for implants to bond well with the surrounding living bone if long-lasting clinical success is to be achieved. For example, well-bonded hip implants have a 10 year failure rate, which is lowered fivefold if bonding is poor or absent. The techniques that are currently available to impart implant surfaces with the desired osteoconductive properties are essentially limited. To overcome the inherent difficulties, we have developed a 'biomimetic' coating process. By this means, implants with complex surface geometries, such as porous spinal implants, can be furnished with a bone-bonding surface. Furthermore, these coatings can be rendered osteoinductive as well as osteoconductive (by incorporating osteogenic agents). Using this facility, we have induced bone formation at an ectopic site in rats, and have accelerated osseointegration (bone bonding) at an orthotopic dental site in adult miniature pigs. Our preliminary results indicated that these osteoinductive dental implants bond with surrounding bone within one week instead of the usual three weeks. We believe that surfaces coated with biomimetic coatings into which osteogenic growth factors are incorporated hold great potential for use in clinical orthopaedics and dentistry.

The combination syndrome: a literature review

Although combination syndrome is recognized by many clinicians, documented observations seem to be rare. The aim of this article was to critically review the literature regarding combination syndrome to evaluate the evidence for this concept. A search of the dental literature with Medline/PubMed through July 2002, focusing on the combination syndrome and related features, was undertaken and combined with a hand search of older references and textbooks on removable prosthodontics.

Mandibular implant-retained overdentures: a literature review

The implant-retained overdenture for the mandible has been shown to be a highly successful prosthetic treatment similar to the fixed implant denture. However, controversy persists as to its design and indications. Few literature reviews have been published on the topic. This article critically analyzes the existing mandibular implant overdenture literature relative to bone preservation, effect on antagonist jaw, number of implants required, anchorage systems, maintenance, and patient satisfaction. A MEDLINE search was completed (from 1987 to 2001), along with a manual search, to locate relevant English-language articles on mandibular implant overdentures. Twelve treatment concepts are elucidated from a distillation of the literature review.

Modalities of treatment for the combination syndrome

A series of destructive changes occurring in the jaws of patients wearing a complete maxillary denture opposed by a mandibular distal extension removable partial denture have been described as the combination syndrome. However, the syndrome does not occur in all patients. Those patients who have not developed signs of the combination syndrome and whose mandibular anterior teeth are well preserved and not overerupted may be treated conservatively with a mandibular removable partial denture. A properly designed removable partial denture that distributes occlusal stresses over hard and soft tissues minimizes the risk of developing the combination syndrome. Nevertheless, the overdenture seems to provide a more predictable prognosis, especially for patients who already have the combination syndrome or whose mandibular anterior teeth are structurally or periodontally compromised or overerupted. The treatment modality is determined by the apparent potential of the patient to develop the combination syndrome and by the condition of the remaining mandibular anterior teeth.

Evaluation of anterior maxillary alveolar ridge resorption when opposed by the transmandibular implant

Fifteen edentulous patients with complaints regarding denture comfort and/or function were treated with the transmandibular implant. All patients were restored with conventional maxillary dentures opposed by implant-supported removable prostheses. Two to 4 years after surgery, these patients were evaluated for vertical and horizontal maxillary bone loss with a radiographic analysis developed by the authors. With this technique, attention was focused on vertical alveolar ridge resorption in the anterior maxilla. Although the sample size was small, the findings from this study indicate that vertical bone loss in the anterior maxilla does occur when a maxillary denture is opposed by an implant-supported overdenture. Comparison of these results with a previous study that evaluated anterior maxillary resorption when a complete maxillary denture opposed natural mandibular anterior teeth and a distal extension removable partial denture demonstrated no statistically significant difference.