Effects of polymethyl methacrylate-based bone cement graft for treating excessive gingival display and its dimensional facial changes: 12-Month clinical study

Objective

to present a 12-month follow-up with photographic and tomographic analyses of the effect of polymethyl methacrylate-based bone cement graft (PMMA) in gingival exposure (GE) in patients with excessive gingival display (EGD).

Methods

Twelve patients with EGD were included. The PMMA was surgically placed. A frontal and lateral photograph protocol was performed at baseline (T0), 3 (T3), 6 (T6), and 12 months (T12) post-operatively. Soft tissue cone-beam computed tomography (ST-CBCT) was performed at T0 and T12. Measures included GE, length of the lip vermilion (LLV), lip shape (LS), nose width (NW), filter width (FW), nasolabial angle (NAS) while smiling, and nasolabial angle at rest (NAR). The height, thickness, and volume of the cement graft were also measured in the ST-CBCT. The comparisons were performed by Kruskal-Wallis test at 5 % of significance (p < 0.05).

Results

The height, thickness, and volume of the PMMA were respectively 12.84 ± 1.59 mm, 3.83 ± 0.53, and 1532.02 ± 532.52 mm3. PMMA significantly decreased GE from 8.33 ± 1.25 mm (T0) to 6.60 ± 0.93 mm (T12) (p < 0.01). NAR was 98.34 ± 9.28° at T0 and increased to 105.13 ± 7.33° at T12; however, the angle value was not statistically different (p = 0.08). LLV, LS, NW, FW, and NAS did not exhibit statistical differences between the baseline and follow-up periods.

Conclusions

PMMA significantly decreased GE in a 12-month follow-up without influencing adjacent soft tissue anatomical structures.

Assessment of Deviations of Implants Installed with Prototyped Surgical Guide and Conventional Guide: In Vitro Study

OBJECTIVE

 The study aimed to assess the angular and linear deviations of implants installed in mannequins aided by surgical guides produced with the techniques of dual tomography (DT), model-based tomography (MT), and nonprototyped guide.

MATERIALS AND METHODS

 Implants were installed in mannequins of a partially edentulous maxilla and divided into three groups: Group C (n = 20), implants installed using the conventional technique with flap opening and conventional guide; Group DT (n = 20), implants installed using guided surgery with the dual tomography technique; and Group MT (n = 20), implants installed using the model-based tomography technique. After implant installation, the mannequin was subjected to a computed tomography (CT) to measure the linear and angular deviations of implant positioning relative to the initial planning on both sides.

RESULTS

 There was a higher mean angular deviation in group C (4.61 ± 1.21, p ≤ 0.001) than in groups DT (2.13 ± 0.62) and MT (1.87 ± 0.94), which were statistically similar between each other. Similarly, the linear deviations showed group C with the greatest discrepancy in relation to the other groups in the crown (2.17 ± 0.82, p = 0.007), central (2.2 ± 0.77, p = 0.004), and apical (2.34 ± 0.8, p = 0.001) regions.

CONCLUSION

 The techniques of DT and MT presented smaller angular and linear deviations than the conventional technique with the nonprototyped guide. There was no difference between the two-guided surgery techniques.

Evaluation of deviation in implants placed at different depths with a prototype surgical guide: an in vitro study

The aim of this study was to measure the angular and linear deviations between planned and placed dental implant positions at different depths in an in vitro model. Ten dental manikins of a maxilla without the central and lateral incisors were used. The implants were placed in the tooth positions using a prototype guide based on computed tomographic scans of dental casts. The groups consisted of implants placed at varying depths according to tooth position: 1 mm deep for the right lateral incisor, 2 mm deep for the right central incisor, 3 mm deep for the left central incisor, and 4 mm deep for the left lateral incisor (n = 10 per group). After implant placement, the manikin was scanned again to compare the positioning of the implants to the planned positions. Statistical analysis evaluated the linear deviations between planned and placed implant positions at 3 points (coronal, central, and apical) as well as the angular discrepancies. The analysis showed that the depth of the implant placement proportionally affected the linear deviation of the actual position from the planned position; thus, the deeper implants showed significantly greater linear deviations (P < 0.05; 1-way analysis of variance and Tukey test). There were no statistically significant differences in the mean angular deviations of the groups. Thus, the results suggest that implants placed at greater depths present greater linear deviations than implants placed at shallower depths, but the angular deviation is not affected by implant depth.