|Year : 2014 | Volume
| Issue : 1 | Page : 3-7
Implant dentistry: Periodontal and restorative factors in a multidisciplinary approach
Latha S Davda1, Sanjay V Davda2
1 University of Portsmouth Dental Academy, Portsmouth, PO1 QG, London, United Kingdom
2 Department of Oral Surgery, King's College London Dental Institute, Denmark Hill, London, United Kingdom
|Date of Web Publication||21-Jun-2014|
Latha S Davda
University of Portsmouth Dental Academy, Portsmouth, PO1 QG, London
Source of Support: None, Conflict of Interest: None
| Abstract|| |
The long-term success of any dental implant treatment is influenced by several factors including patient factors, preventative measures used by the patient, esthetics, surgical factors, periodontal factors, restorative factors, and the mechanical factors of the implant system. The patient factors, esthetic factors, prevention, surgical, and mechanical factors influencing the treatment planning of a dental implant patient were discussed in the previous papers. This article will discuss the periodontal and restorative factors involved in dental implant treatment with relevant case studies.
Clinical Relevance to Interdisciplinary Dentistry
Long term implant success is dependent on several factors. The periodontal and restorative factors involved in implant treatment are discussed.
Keywords: Dental implant, long-term success, multidisciplinary, periodontal factors, prosthetic factors, restorative factors
|How to cite this article:|
Davda LS, Davda SV. Implant dentistry: Periodontal and restorative factors in a multidisciplinary approach. J Interdiscip Dentistry 2014;4:3-7
|How to cite this URL:|
Davda LS, Davda SV. Implant dentistry: Periodontal and restorative factors in a multidisciplinary approach. J Interdiscip Dentistry [serial online] 2014 [cited 2019 Jun 19];4:3-7. Available from: http://www.jidonline.com/text.asp?2014/4/1/3/134996
| Introduction|| |
The long-term success of any dental implant treatment is influenced by several factors listed in [Table 1]. ,, Patient factors, implementation of prevention, esthetics, surgical factors, radiological factors, and mechanical factors were discussed in the previous papers by the author.  The restorative and periodontal factors influencing long-term implant success are discussed with the relevant examples.
Periodontal factors to consider before implant placement are the patient's periodontal status and associated periodontal risk factors. The risk factors are the patient's oral hygiene, secondary systemic diseases, smoking, and traumatic occlusion. The most common cause of tooth loss is periodontal disease.  When implants are placed in patients with existing periodontal disease, there is a high-risk of periimplantitis. Infection around an implant is a major cause of implant failure. The micro flora associated with failing implants has been found to be identical to those in chronic adult periodontitis. ,,] Sub-gingival dental plaque is an important source of bacteria colonizing newly inserted implants in partially edentulous subjects. , Some implant surfaces such as the titanium plasma-sprayed surfaces, are more susceptible to implant failure due to periimplantitis than machine surfaced implants. In a meta-analysis study, Esposito et al. [ 1] found that implants with roughened surfaces were more affected with periimplantitis compared with implants with smooth surfaces. Periradicular pathosis of teeth adjacent to implant may jeopardize the implant.  Such adjacent teeth may need to be root canal treated or extracted prior to implant placement to prevent microbial contamination of implant during healing. However, some animal studies  showed that teeth with periradicular lesions do not adversely affect adjacent titanium implants. Some of the causes of implant periradicular lesions are attributed to overheating of bone during placement, overloading, preexisting infection, implant contamination during production or insertion or placement of implant in infected maxillary sinus. 
An implant is considered to be failing or failed, if there is horizontal mobility of >0.5 mm, vertical mobility, rapid progressive bone loss, pain, and exudation of pus despite treatment. , Early signs of perimucositis are bleeding on probing and inflamed gingiva around implants. This should be treated aggressively before bone loss sets in. Intense oral hygiene instructions to improve plaque control, educating the patient to use interdental aids like the single tufted tooth brush or super-floss effectively, help in controlling the mild disease. Periodic radiographs and the bone levels along with the appearance of the bone around implants is a good indicator of periimplantitis. Smoking in addition to existing periodontal disease increases the bone loss. Radiograph [Figure 1] taken 2 years after placement of an implant in a smoker shows extensive bone loss.
|Figure 1: Radiograph showing bone loss around an implant placed in a smoker 2 years after placement|
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The treatment options for ailing and failing implants can be divided into nonsurgical and surgical therapy. Nonsurgical therapy involves pharmacological treatment, mechanical treatment, and elimination of occlusal interferences. The pharmacological therapy includes chlorhexidine mouthwash 0.5%, though no scientific data has validated its effectiveness. Tetracycline fibers inserted locally and systemic antibiotics have been used. , Mombelli and Lang  showed that with local removal of plaque , surgical irrigation of periimplant pockets with chlorhexidine 0.5%, polishing of the accessible surface of implant with rubber cup and pumice and a 10-day course of systemic antimicrobial therapy, a 2.5 mm pocket depth reduction in ailing implants. Scaling should be done with plastic tipped scalers or an air-powder abrasive system or a rubber cup and pumice to prevent damage to titanium surface of the implants. These methods will not damage the implant surface. The standard periodontal curettes will damage the implant surface. ,,, Maintaining smooth surface of the exposed implant ensures cleaner implant environment.
Surgical therapy becomes necessary when nonsurgical therapy is not successful or not indicated. The aim is to completely remove periodontal pathogens and endotoxins from the implant surface. , The hydroxyapatite (HA)-coated surface of the implants is more prone to be affected by these microorganisms. With inflammation, the pH falls locally and the HA coated surface may decalcify and resorb, with subsequent loss of connective tissue attachment. This will lead to osseous defects similar to the effects of periodontal disease.  Detoxification of implant surface has been more successful with citric acid and tetracycline application locally and with scaling with plastic instruments.  After detoxification, the osseous defect should be grafted with or without membranes. Membranes retain the graft in the desired position.
| Restorative factors|| |
Restorative factors that affect the long-term success of implant restorations are the management of the occlusal stresses, parafunctional habits, the design of the crown or the bridge both in terms of materials, size and shape and the crown implant ratio.
Implants cannot adapt like natural teeth because of lack of the periodontal ligament. Implants, when used next to natural teeth, are easily overloaded and this causes failure.  Occlusal stresses are caused by inadequate number of implants to support the prosthesis, heavy occlusal contacts in centric occlusion, interferences and excessive buccal or lingual cantilever that is, occlusal table is too wide for the implant diameter.
Thus, at the treatment planning stage, it is very important to identify these factors and to avoid them. Once the source of additional forces is identified, the treatment plan must be revised to lower their negative impact on bone, implant and restoration. Ideally, an increase in bone-implant surface area by placing additional implants or decreasing the pontic numbers will help in dissipation of stress.  An increase in implant width rather than increase in length will decrease the stress transmission to surrounding crestal bone and decrease the likelihood of fracture.  An increase in 0.5 mm of abutment post diameter will increase the fatigue strength by over 30%. 
Bruxism forces are difficult to treat in the long-term. Bruxism can cause crestal bone loss, loosening of abutments and fatigue stress fracture of implant and prosthesis. If the opposing arch has a soft tissue supported removable prosthesis, the effects of bruxism are minimized, but the bone loss under the prosthesis is increased. In bruxism, the two main modifications suggested in the treatment plan are additional implants and elimination of posterior lateral occlusal contacts in excursive movements. Excessive occlusal loading can cause loosening of abutment screws and possible implant fracture. , Using a night guard can reduce the damage to the implant superstructure in bruxists.
Shackleton et al.  have reported that cantilevers >1.5 mm induced overloading resulting in periimplant bone loss and prosthetic failure. This has also been reported in other studies. ,,, [Figure 2] shows the radiograph of a cantilever bridge supported by single implant, resulting in repeated screw loosening. This was resolved by changing the bridge to a single implant supported crown. A loose abutment will trap plaque underneath it and can also give rise to bone loss [Figure 3] and [Figure 4]. If detected early this bone loss could be prevented by tightening the abutment and recementing the crown. Rangert et al.  evaluated implant fractures and reported that 90% of the fractures occurred in posterior area and most of these were supported by one or two implants with cantilever in association with bruxism. Misch  proposed that for implants placed in poor quality bone, extended healing time and carefully monitored and gradual loading improved the implant stability.
|Figure 2: Radiograph of a cantilever bridge supported by single implant resulting in repeated screw loosening|
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|Figure 3: A loose abutment causing periimplantitis and bone loss – radiograph|
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|Figure 4: Bone loss caused by a loose abutment evident on surgical exposure|
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Currently, there is no evidence-based implant-specific concept of occlusion.  However, the occlusal principles in tooth restorations (balanced, group function, and mutually protected occlusion) have been successfully adopted with modifications for implant supported prosthesis.  Misch et al.  have proposed an implant protected occlusion, which is designed to reduce occlusal forces on implant prosthesis. These modifications include load sharing occlusal contacts, narrow occlusal table, and increased implant surface area, elimination of unfavorable biomechanics, occlusal morphology, and reduction of cusp inclination. The tooth morphology should be flat around centric contacts so that the occlusal force is directed apically.  The reduction of cusp inclination will decrease the bending movement and direct force axially too. , Reduction of occlusal table by 30-40% has been suggested for implants prosthesis.  [Figure 5] illustrates the narrow occlusal table of an implant supported crown in the upper first premolar region. Dimensions larger than implant diameter can create cantilever effects unless the occlusal force is along the vertical axis of the implant. The force distribution between implants and natural teeth differ due to positional changes in vertical and mesial direction in natural teeth. This may intensify the occlusal stress on implants.  Hence, re-evaluation and periodic occlusal adjustments are necessary in partially dentate implant patients.
|Figure 5: Narrow occlusal table of an implant supported crown in the upper first premolar region|
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In the anterior region, restoration of the implants can produce esthetic challenges if the implants are not placed during surgery in the ideal position [Figure 6]. The implant neck will need to be camouflaged with porcelain [Figure 7]. In this case, the patient had a smile line that did not show the gingival margin. The crown implant ratio is an important risk factor, especially when short implants are used as they are associated with higher prosthetic complications such as screw loosening and porcelain fracture. 
|Figure 6: Upper right implant placement is not in the ideal position for restoration|
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|Figure 7: Upper right implant in lateral incisor position camouflaged with porcelain|
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Mechanical complications that occur are screw loosening, veneer fracture, crown or bridge debonding, framework fracture, screw fracture or implant fracture.  There are more incidents of screw loosening in single implant crowns (12.7%) compared to implant retained fixed bridges (5.8%) and implant retained fixed bridges with cantilever (8.2%). The incidence of crown and bridge debonding is reported as an average of 5.6%.  The others are rare complications, but can be time consuming and expensive to correct.
| Conclusion|| |
The long-term success of implant treatment is heavily dependent on the periodontal and the restorative factors. The periodontal factors such as the patient's periodontal condition, oral hygiene regime and the ability to maintain adequate plaque control, patient's smoking status and systemic disease influencing periodontal condition must be evaluated and taken into account before embarking on implant treatment. The restorative factors such as the patient's occlusion, para-functional habits, design and material of the prosthetic restorations are important to avoid biological and mechanical complications.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]