PROXIMAL CONTACT LOSS BETWEEN IMPLANT CROWNS AND NATURAL TEETH
Randolph R. Resnik DMD, MDS
A common complication being reported recently in the literature is the development of an open contact area (where there was a prior contact) between a dental implant crown and a natural tooth. This loss of contact can result in possible complications consisting of food impaction, caries, peri-implant disease, and prosthesis remediation. Gasser et. al. has shown that open contacts (no interproximal resistance) occur 50 % of the time in a 10-year retrospective study. 1 Manicone et. al., also in a 10-year retrospective study, reported interproximal gaps approximately 51% of the time. 2 Wei et al related an even higher incidence of 58% with the average time period being 2.2 years. 3 Therefore, as can be seen from the current literature, proximal contact loss is a significant and common problem. The etiology of acquired open contacts is unclear, and most likely caused by many factors. Open contacts usually do not occur between natural teeth because of physiologic drift (i.e. mesial drift). Mesial drift is the natural tendency for teeth to move in a mesial direction within the dental arch, which results in maintaining the interproximal contacts between adjacent teeth. When an implant is adjacent to a natural tooth, the osseous interface will not allow for the implant to move in association with the natural tooth, thereby allowing for a contact to open.
Another possibility of the etiology of open contacts may originate from occlusal forces, mainly from the mandibular closure muscles (i.e., lateral and medial pterygoid, masseter, temporalis). The forces directed to the teeth are dictated by inclined cusp planes. Forces exist that may push teeth mesial and distal; however, the anterior (forward) vector is five times stronger than the posterior force. Studies have shown the anterior component of force is transmitted via the interproximal contacts and that its strength will decrease with increased distance from the posterior teeth. Another possible reason for the loss of contact area is craniofacial growth. Facial growth has been reported in some patients well into adulthood. Even minor facial growth may allow for mesial, buccal, or vertical growth leading to the opening of occlusal contacts.
Enameloplasty Prior To Impressions:
To minimize this complication, before the final impression for a crown, an enameloplasty should be completed to allow for parallel interproximal contact areas. The longer and wider contact areas will allow for better force distribution, especially if there is a significant mesial or distal cantilever over the marginal ridge area. This concept has been advocated in natural dentition via large interproximal contacts to increase tooth position stability.
To maintain strong contact and prevent tooth movement, an occlusal guard may be warranted to minimize excessive occlusal forces and to maintain tooth position.
Occlusion may be modified to obtain even contacts on all incline planes, which results in decreasing the distal vector forces on the natural tooth
Treatment of an open contact usually will include remaking the prosthesis or adding a contact to the adjacent tooth via a new crown or composite bonding.
- Gasser, Thomas JW, et al. “Interproximal contact loss at implant sites: a retrospective clinical study with a 10‐year follow‐up.” Clinical Oral Implants Research 33.5 (2022): 482-491.
- Byun, Soo‐Jung, et al. “Analysis of proximal contact loss between implant‐supported fixed dental prostheses and adjacent teeth in relation to influential factors and effects. A cross‐sectional study.” Clinical oral implants research 26.6 (2015): 709-714.
- Wei H, et al: Implant prostheses and adjacent tooth migration: a preliminary retrospective survey using 3-dimensional occlusal analysis. Int J Prosthodont 21:302–304, 2008.