# Evaluation of Proximal Contact Tightness and Contact Area of Posterior Composite Resin Restorations
## 4 Discussion
Although this stage was kept standard for each group, how much material this sanding process removed from the composite surfaces was not measured. Studies have shown that sectional matrices have different effects on the separation of the retaining ring in the opening amount and the area where it is positioned [16; 33; 34]. However, some studies have claimed that separation rings in sectional matrices create similar contacts when used in accordance with the manufacturer's instructions and that dentists tend to use them in this way [35; 36]. However, in some recent studies, it has been shown that Palodent BiTine or similar Composite-Tight Gold separation rings, which are designed to be more anatomical to the contact area of the posterior teeth and produced with a higher percentage of titanium in the metal alloy, provide greater separation [26; 37]. This extra titanium ring or ally add-in makes the separation ring more flexible as well as able to apply more force in separation. In addition, if the gripper arms are only flat cylindrical metal in form, are not designed for the interproximal area where the embrasures are located and do not allow the positioning of the wedge, they would cause a tight contact but a weak contour [38]. Since the OM is a sectional matrix system with similar features, it explains the weaker contours in histogram measurement compared to the PM matrix system. Additionally, there are studies in the literature that support our results, the common opinion in all of them is that buccal and lingual embrasures are very effective in creating contact and contour [30]. The measurement and evaluation process of the contact tightness is a challenging procedure where the contact and contour must be compatible together such as in Class II cavities. In cases where there is sufficient contact, if there is an inappropriate contour or vice versa, erroneous measurements will be inevitable. In addition, under clinical conditions, the position of the patient, the stability of the physician, the measurement speed and adequacy of the device, the wetness of the area, which affects the frictional stress caused by teeth and gums, and similar anatomical factors will directly affect the measurement process [34; 39]. In a study conducted by [PERSON] et al., it was reported that there were differences in contact tightness measurements depending on the position of the patients as well as the teeth; therefore, it was quite difficult to make objective measurements in the in vivo conditions [34]. Therefore, it is essential that the measuring system has to be fixed to achieve similar results in all conditions to exclude possible effects [40]. Additionally, the polishing stage has a direct effect on the quality and integrity of the contour and strength of the contact point by altering the previous steps and influencing the final results. To maintain the contact point of the restoration solid and tight as the natural morphology of the tooth, it is required to establish a standardized polishing process to minimize the loss of resin composite and to avoid open contacts. Although this PDPM system is designed and manufactured for clinical use, in vitro test conditions are applied to make standard measurements with this prototype and to reveal the pros and cons of the system, which may cause conflict between the results and incompatibility with the literature. Although reliable and reproducible results are obtained if the system is stabilized in the mouth, the usability of the device in cases of missing anterior abbutment/anchor teeth will be challenging under clinical conditions. Additionally,the fact that the manikin model measured in this study remained completely motionless to reflect simulating in vitro conditions is also a misleading advantage. Considering that in clinical conditions, people's natural movements and even breathing can affect the results, the measurement process must be fast enough to be completed in a very short time.