23 June 2021

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Proximal contact loss between implant restoration and adjacent tooth

Giulia Palandrani

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Dental implant therapy has been widely used as a treatment for missing teeth.  Although dental implants have demonstrated a high survival rate (over 95%) and 5-year success rate (over 90%), complications associated with dental implants can occur and become problematic 

One of the complications that is frequently observed, but easily overlooked, is proximal contact loss ( PCL ). A PCL can occur and result in a gap formed between two natural teeth, two implants or the implant and its adjacent natural tooth.  Recent studies have shown that the prevalence of PCL between implant- supported fixed dental prostheses (FDP) and adjacent teeth ranged from 34% to 65%. 

Many studies have shown that teeth have a tendency to migrate mesially. It is driven by a forward occlusal force, known as the anterior component of force (ACF). In contrast, an implant prosthesis showed much less vertical movement than a natural tooth does during mastication (5 μm vs 28 μm), and has no mesial migration which is more like an ankylotic tooth. When a mesial drifting of the adjacent tooth occurs while the implant is immobile, a gap may be formed between the natural tooth and the implant prosthesis. This is one of the most widely accepted assumptions for mesial PCL .

Although the mesial drifting theory can explain some of the PCL  cases, PCL occurs not only at the mesial side, but also at the distal side. In addition, not all patients developed PCL. Many possible factors for PCL have been implicated, such as age, gender, functional time, adjacent teeth conditions, opposing dentition, implant position, periodontal condition, oral hygiene, and parafunctional habits.  In this study the prevalence and associated factors of  PCL between implant restorations and adjacent teeth were investigated.

Material and methods 
317 patients, 120 were male and 197 female who had received implant- supported FDP in the posterior region  with a mean age of 54 years old were examinated. The restoration types of prostheses were either cement type or screw-retained implant-supported FDP . Of the 549 implants, 349 were single crowns and 200 were splinted implant-to-implant FDPs.  When the prostheses were delivered, the proximal contact surface was adjusted by a dental floss. If the dental floss passed through the proximal contact area with sufficient resistance, the proximal contacts were considered as closed.

 During clinical assessment proximal contact tightness (PCT), oral hygiene conditions, and periodontal health of each patient and additional factors were examined. The degree of PCT was evaluated with a dental floss passing through the contact areas and classified as: (a) tight: sufficient resistance to the passage of the floss; (b) loose: insufficient resistance to the passage of the floss; and (b) open contact: no resistance to the passage of the floss. Patients also received a comprehensive evaluation for their periodontal conditions (such as gingival index, pocket depth, alveolar bone position, and periodontal abscess) through clinical and radiographic examinations, along with food impaction conditions. 

Results and discussion
A total of 317 patients participated in this study. The total numbers of mesial contacts and distal contacts analyzed were 549 and 301. Then, 148 of 549 mesial contacts (27%), and 14 of 301 distal contacts (5%) were classified as “ PCL ” (open contacts). The earliest  PCL  was observed in 4 months after prosthesis delivery and five occurred within 1 year. Less than 20% of the   PCL at the distal side occurred by 12 years, while 50% of the mesial contact loss occurred by 9 years 

Six factors showed significant associations with the mesial contact loss (P <.05), including patient age (P = .0212), frequency of using interdental brush (P = .0006), functional years of prostheses (P = .0002), single or splinting implant (P < .0001), food impaction (P < .0001), and plunger cusp in the opposite jaw (P = .0046). 

Conclusion
PCL at the mesial side was frequent and increased over functional years after prosthesis delivery. It should be considered as a complication associated with dental implants. Using an occlusal retainer to prevent  PCL was also suggested. Although oral hygiene conditions contributed little to  PCL , the effect of food impaction and the use of interdental brushes were significant 

 

For additional information: The prevalence and associated factors of proximal contact loss between implant restoration and adjacent tooth after function: A retrospective study