## 4 Discussion

Table 3: The prevalence of radiographic abnormalities found in class II composites restorations among genders, age groups, tooth, and restoration surfaces. mentioned in vitro study, nearly 63% of the examined samples had voids between the layers [23]. These results were substantially higher than the 7.8% examined radiographically in the present study. Pre-molars and disto-oclusal restorations had a high rate in this radiographic condition. The appearance of interlayer gaps is frequent in incremental techniques if the layers are not appropriately adapted [24]. These interlayer gaps affect the physical properties of the restoration [23]. All the restorations were assumed to be performed by an incremental technique using Optibond solo unidose (Kerr, Brea, CA, USA) and low-viscosity or high-viscosity universal hybrid composites TPH Spectra ST (Dentsply, Milford, DE, USA) available in the predoctoral clinics. The operator's ability may also have influenced this outcome. Providers performed all the restorations under training (juniors and senior dental students). Sixty-five percent of voids were found in restored premolars, and 69% accounted for two surfaces (disto-oclusal) restorations. Cavity preparations in premolars are often conservative. They are represented by slot preparations compromising the proximal lesions and occlusal access. The placement and adaptation of the first increment of composite on the bottom of the slot preparation may offer challenges due to the restricted access. Furthermore, in specific clinical scenarios, the distal box of the preparation can be more difficult for visualization and adaptation of the material. Three percent of the examined restorations had overhangs. [PERSON] et al. [25] found similar rates of 4% of prevalence overhang [26]. The positive ledge at the margins is an iatrogenic factor for gingivitis through mechanical irritation. [PERSON] et al. [27] showed higher radiographic attachment loss with marginal overhangs in periodontitis involved patients [27]. Corroborating with this find, [PERSON] et al. [28] also suggest the degradation of local periodontal health and the promotion of secondary caries formation [28]. The irregular rough surface of the overhang acts as the perfect area for bacterial plaque accumulation. The presence of overhang is mainly caused by incorrect proximal matrix placement. Prior studies have pointed out that applying low-viscosity composites may increase the presence of overhang [29]. Twenty-one percent of the radiographs examined had an abnormal adhesive interface, implying the presence of radiolucent areas between the restoration and tooth structure (Table 3). Furthermore, 11.1% of this radiographic condition is present as an external bonding interface and 9.6% as an internal interface gap. This result is consistent with previously published findings for a 14% (111/770) bond layer interface and 11.8% (91/770) lack of adaptation, which includes both external interface gap and overhang [30]. Gaps at the gingival margins are a dilemma for class II composites is the most common zone for secondary caries development. Our data indicated a higher prevalence of external gaps at the gingival margin. This result is less than other studies of 33 % underfilled restorations [23]. The gingival interfacial gap at the enamel level suggests weaker bonds and higher microleakage potential at the dentine level [28]. Several studies showed a correlation between the depth of the ditched margins and the demineralization process [29; 30]. Other technique-related factors can also create radiolucent halos [31]. For example, a thick adhesive layer can lead to misdiagnosis and retreatment [7]. On the other hand, a more apparent radiolucent zone promoted by adhesive pooling in the bottom of the cavity may be easily interpreted as secondary caries, marginal gaps, or voids beneath the restoration [31; 32; 33]. According to [PERSON] et al.