A newly published clinical study has drawn attention to one of the most overlooked aspects of restorative dentistry: proximal contact quality. While clinicians often focus heavily on material selection, bonding systems, and aesthetics, the study suggests that many restorative failures may originate from something far more basic—the quality of the contact area itself.
The investigation proposed a standardized floss-based classification system for evaluating proximal contact tightness chairside and assessed the quality of proximal contacts and marginal integrity across various direct and indirect restorations.
Why proximal contact matters
In natural dentition, proximal contacts are not static points but dynamic areas that help distribute occlusal forces, stabilize teeth and minimize food impaction. Improper contacts—whether excessively open or excessively tight—can contribute to:
food lodgement,
gingival inflammation,
periodontal breakdown,
flossing difficulty,
tooth migration, and
recurrent caries.
Although clinicians routinely verify contacts using dental floss, the study highlights that this assessment remains highly subjective in daily practice.
Only one-third of restorations demonstrated “appropriate” contact
The study evaluated 344 proximal surfaces across multiple restoration types and reported notable variability in contact quality:
34.6% demonstrated appropriate contact, 28.5% were excessively tight, 24.1% showed open contact, and 12.8% demonstrated poor contact quality.
These findings suggest that suboptimal proximal contacts may be far more common in routine practice than many clinicians realize.
The authors also emphasized that tactile floss assessment inherently carries perceptual variability, since floss tension, insertion angle, wetness, and operator interpretation can influence the perceived “snap” sensation.
Indirect restorations performed better
One of the most clinically relevant findings was the superior performance of indirect restorations compared with direct restorations.
Single crowns demonstrated better proximal contact quality and marginal integrity overall, likely because laboratory fabrication allows improved contouring and contact refinement before cementation.
Among direct restorations, glass ionomer cement restorations showed relatively favorable outcomes, whereas posterior composite restorations remained highly technique-sensitive. The study reinforced previous evidence showing that sectional matrix systems combined with separation rings continue to provide superior proximal contact predictability compared with wedges or hand instrumentation alone.
Mesial surfaces showed better outcomes than distal surfaces
The authors additionally observed a statistically significant association between contact quality and restoration surface location.
Mesial restorations demonstrated a higher frequency of acceptable contacts compared with distal surfaces.
The study attributed this difference primarily to accessibility factors, including:
easier matrix adaptation, improved wedge placement, better visibility, and simpler manipulation during restoration placement.
These findings are particularly relevant in posterior Class II and MOD restorations, where distal box management remains one of the most technique-sensitive aspects of direct restorative dentistry.
Marginal integrity remains closely linked to contact quality
Beyond contact tightness, the study also evaluated marginal integrity using USPHS criteria.
Indirect restorations demonstrated superior marginal adaptation overall, whereas direct restorations showed greater susceptibility to adhesive failure and marginal gap formation over time.
Importantly, the authors stressed that proximal contact quality and marginal integrity cannot be viewed independently. Poor contour or improper contact pressure may negatively influence both periodontal health and restoration longevity.
A simple chairside tool with significant clinical relevance
Unlike many contemporary restorative studies focused on advanced materials or digital systems, this investigation centered on refining a simple clinical procedure already used universally in practice: floss evaluation.
The authors proposed that a standardized floss-based classification system could provide clinicians with a reproducible and clinically feasible method for assessing contact quality chairside, particularly in general practice and dental education settings.
Clinical implications
The study reinforces several practical restorative principles:
proximal contacts require more than simply “closing the space”; matrix system selection significantly influences outcomes; overly tight contacts can be as problematic as open contacts; posterior direct composites remain highly technique-sensitive; and restoration longevity often depends on small details that may be overlooked during finishing and verification.
As adhesive dentistry continues to evolve, the findings serve as a reminder that successful restorative treatment is often determined not only by the material used, but by the precision with which fundamental clinical principles are executed.