Periodontal response to experimental tooth movement by interrupted orthodontic force in rats

The upper first molars of Wistar rat were moved experimentally using an expansion screw in order to clarify whether an interrupted orthodontic force that maintains the blood circulation in compressed periodontal ligament (PDL) can cause efficient tooth movement without pathological damage.In the 30-μm group with moving distance of one-third of PDL width, degenerating tissue with toluidine blue staining and appreciable root resorption were not seen during the experimental period. On the other hand, in the 60-μm group with moving distance of two-third of PDL width degenerating tissue and severe root resorption appeared. On observation of bone formation using Villanueva fluorescent staining, a thick labeling line was observed on the tension side in both experimental groups.In statistical analysis about the ratio between mesial and distal PDL areas, expressing expansion rate of mesial PDL, there was no significant difference between 30-μm and control groups, except an experimental period of day 11. In contrast, significant differences were seen between 60-μm and control groups in 23–31 days after tooth movement.From these results, it is evident that the interrupted force that induces tooth movement within a distance of approximately one-third of PDL width enables tooth movement without toluidine blue-stained degenerating tissue, regarded as pathological damage, and promotes bone formation on the tension side.     

Long-term tooth survival following regenerative treatment of intrabony defects

BACKGROUND: The longevity of the clinical benefits of guided tissue regeneration (GTR) has not been fully explored. The aim of this investigation was to assess the long-term survival of GTR treated sites in terms of clinical attachment level (CAL) stability and tooth loss. METHODS: A total of 175 patients with one deep intrabony defect were selected for a retrospective investigation of tooth retention and CAL stability. All sites had been treated with GTR more than 2 years previously and had received full periodontal examinations every 2 years for up to 16 years. Definitions of events for survival analyses were tooth loss, loss of > or = 2 mm compared with the CAL observed before GTR treatment, and loss of > or = 2 mm compared with the CAL observed 1 year after completion of GTR. RESULTS: Teeth were severely compromised by the presence of CAL loss of 10.7 +/- 2.4 mm, probing depths of 8.7 +/- 2.3 mm and deep intrabony defects (average depth 6.6 +/- 2.1 mm). After GTR, CAL gains were 4.6 +/- 2 mm. Average follow up was 8 +/- 3.4 years; 66.9% of subjects strictly complied with a periodontal maintenance program. Tooth survival was greater than 96% more than 10 years after GTR. CAL was equal or coronal with respect to pretreatment in 92% of cases followed for 15 years after treatment, while loss of CAL compared to the 1-year post-GTR result was observed in 37.8% of cases. Cox proportional hazard models indicated that incidence-free survival was negatively affected by smoking and positively affected by full compliance with a periodontal maintenance program in a specialist practice. CONCLUSIONS: Within the limits of this study, data suggest that tooth retention and clinical improvements following GTR treatment of intrabony defects can be maintained long term in the great majority of cases and thus that regenerative periodontal treatment represents an important alternative for the management of severely compromised teeth.     

Periodontal healing after impacted lower third molar surgery. Precision and accuracy of radiographic assessment of intrabony defects

The effect of periodontal tissues of impacted lower 3rd molar surgery has been investigated in a retrospective study comprising 215 cases, 2 years postoperatively. In order to evaluate the precision and accuracy of the radiographic assessment of intrabony defects on the distal surface of the lower 2nd molar using conventional free hand technique, a methodological study was performed on 25 patients. The error variance due to variability in the radiographic reproduction and examiner inconsistency was between 3 and 4% of the total variance. In order to evaluate the radiographic assessment of intrabony defects, intraoral radiographs were taken in the deepest part of the intrabony defect with and without a probe as an indicator. Comparing the 2 sets of radiographs, the deviation was 1 mm or less in 87.9% of the cases. The radiopaque marker enhanced the accuracy of assessment of intrabony defects to 96.7%. The study shows the intraoral freehand technique to be sufficiently reliable as regards radiographic reproduction of the mandibular molar area. It also demonstrates that the radiographic method describes the depth of postoperative intrabony defects on the distal surface of the lower 2nd molar more accurately than probing depth measurements alone.     

Periodontal tissue engineering after tooth replantation

Background: Blood‐derived products, platelet‐poor plasma (PPP) and platelet‐rich plasma (PRP), constitute an approach in the enhancement of tissue healing. PRP has also been used as a scaffold for bone marrow stem cells in tissue engineering. This study evaluates the effect of PPP, calcium chloride–activated PRP (PRP/Ca), calcium chloride– and thrombin‐activated PRP (PRP/Thr/Ca), and bone marrow mononuclear cells and PRP/Ca (BMMCs/PRP/Ca) on the healing of replanted dog teeth. Methods: After 30 minutes of extraction, teeth were replanted with 1) no material (control); 2) PPP; 3) PRP/Ca; 4) PRP/Thr/Ca; or 5) BMMCs/PRP/Ca. Histologic, histomorphometric, and immunohistochemical analysis was assessed 120 days after replantation. Data from histomorphometric analysis were analyzed statistically (analysis of variance, Tukey; P <0.05). Quantitative immunohistochemical analysis was analyzed by Kruskal‐Wallis and Dunn post hoc test (P <0.05). Results: Flow cytometry analysis showed 55.98% of CD34⁺ and 32.67% of CD90/Thy‐1 for BMMCs sample. BMMCs/PRP/Ca presented the largest areas of replacement resorption characterized by osseous ingrowth into cementum (P <0.05), with intense immunomarcation for tartrate‐resistant acid phosphatase. The PRP/Ca group also showed areas of replacement resorption with significant immunomarcation for osteopontin. PRP/Thr/Ca presented no replacement resorption. PPP showed areas of inflammatory resorption, with immunomarcation for tartrate‐resistant acid phosphatase. Conclusions: The results suggest that platelets activated with thrombin play an important role in the healing of tissues after tooth replantation. Additional studies are necessary to test other materials, because PRP/Ca did not present an appropriate scaffold for undifferentiated cells in the treatment of avulsed teeth.     

Periodontal regeneration of intrabony defects using resorbable membranes: determinants of the healing response. An observational clinical study

The safety and bone-regenerative capacity of a resorbable membrane (Resolut) was evaluated by a nonrandomized prospective clinical study of patients with periodontal defects. Prior to surgical management all patients underwent scaling and root planing and were instructed on oral hygiene. The study included 18 patients (31 periodontal defects) who received surgical treatment by guided tissue regeneration (GTR) using resorbable membranes. The results were evaluated 12 months after surgery in terms of Plaque Index, bleeding index, probing depth, gingival recession, clinical attachment level, and dental mobility. The results obtained show that the use of resorbable membranes in GTR causes few complications. The mean gain in clinical attachment level (4.06 +/- 1.91 mm), with an attachment level gain of more than 3 mm in 81.2% of the defects, suggests the presence of "new attachment." This difference was clinically and statistically significant (t = 11.03, P = 0). The multivariate regression study showed that 60% of the observed variability (F = 11.48, P < 0.001) in clinical attachment level gain was accounted for by the variable's initial probing depth, the Plaque Index of the tooth subjected to GTR, and the infrabony component of the defect.     

Periodontal regeneration of intrabony defects with resorbable and non-resorbable membranes: 30-month results

Abstract The aim of this prospective split-mouth-study was to compare the healing results in intrabony defects 12 and 30 months after placement of resorbable (polyglactin-910) and non-resorbable (e-PTFE) GTR-membranes. 11 healthy patients with 30 defects participated. 10 patients with 10 pairs of contralateral lesions, which were treated with both membrane types, were included in the split-mouth-design. Furthermore, in an additional group-design all 30 (16 polyglactin-910 and 14 e-PTFE) treated sites were evaluated. Clinical examinations (PBI, REC, PPD, PAL) and radiographic examinations were carried out under standardized conditions immediately before as well as 12 and 30 months after surgery. Additionally, for the assessment of the effectiveness of the 2 membranes by comparing the regeneration results of different defects, the vertical relative attachment gain (V-rAG) was calculated as a% of the PAL gain related to the maximum possible attachment gain (expressed by the baseline depth of the osseous defect intraoperatively measured). Digital subtraction radiography (DSR) was carried out for the quantitative assessment of bone density changes due to GTR. In the split-mouth-design, both types of membranes provided significant V-rAGs (median) after 12 months (polyglactin: 81.7%: e-PTFE: 100.0%) and after 30 months (polyglactin: 69.1%: e-PTFE: 83.8%) compared to baseline. In 90.0% of the polyglactin and e-PTFE sites, a probing attachment gain of at least 2 mm was maintained over the 30-month period. However, in 2 polyglactin treated sites, and 5 e-PTFE treated sites, a new attachment loss was found between 12 and 30 months. DSR showed bone density gain 12 and 30 months postsurgically. No statistically significant differences could be observed between the 2 membrane materials with regard to clinical and radiographic findings. This was confirmed when considering the total number of defects (group-design). In conclusion, based on this 30-month-study resorbable polyglactin membranes may be regarded as a useful alternative to the well established e-PTFE membranes for the treatment of intrabony defects.     

Periodontal parameters and cervical root resorption during orthodontic tooth movement

Objectives: To assess the relationship between periodontal parameters and cervical root resorption in orthodontically moved teeth. Material and Methods: In a standardized experimental tooth movement in 16 periodontally healthy subjects, 29 pre‐molars were tipped buccally for 8 weeks. Eighteen contralateral pre‐molars not subjected to orthodontic movement served as controls. Plaque Index (PI), Gingival Index (GI), probing depth and bleeding on probing were assessed three times before and six times during the experimental phase. Teeth were extracted and scanned in a micro‐computed tomography scanner. The presence or absence, and the severity of cervical root resorption were evaluated on the three‐dimensional reconstruction of the scans by two calibrated examiners. Results: Overall, periodontal parameters were not different between the test and the control teeth. Clear signs of buccal cervical resorption were detected on 27 of 29 orthodontically moved teeth and on one control tooth. Ten subjects had perfect oral hygiene and no gingivitis, whereas six subjects showed a moderate level of plaque and gingivitis (>20% occurrences of PI or GI with >0). No relationship could be demonstrated between resorption and periodontal parameters. Conclusions: Nearly all orthodontically moved teeth showed signs of cervical resorption. Periodontal parameters were unrelated to this important side effect of orthodontic treatment.     

Periodontal repair in surgically created intrabony defects in dogs: influence of the number of bone walls on healing response

BACKGROUND: The objective of this study was to histologically evaluate periodontal healing following flap surgery in intrabony periodontal defects to determine the influence of the number of bone walls on periodontal regeneration. METHODS: One-, 2-, and 3-wall intrabony periodontal defects were surgically produced at the proximal aspect of mandibular premolars in either right or left jaw quadrants in six beagle dogs. Mucoperiosteal flaps were positioned and sutured to their presurgery position following defect preparation. The animals were euthanized at 8 weeks post-surgery, and block sections of the defect sites were collected for histologic and histometric analysis. RESULTS: Bone and cementum regeneration was positively correlated to the number of bone walls limiting the intrabony periodontal defects. The junctional epithelium averaged (+/- SD) 1.5 +/- 0.2, 1.2 +/- 0.3, and 0.9 +/- 0.2 mm for the 1-, 2-, and 3-wall defects, respectively, with the 3-wall defects being significantly different from the 1-wall defects (P <0.05). Cementum regeneration averaged 1.2 +/- 0.6, 2.0 +/- 0.6, and 2.8 +/- 0.5 mm for the 1-, 2-, and 3-wall defects, respectively; all groups were significantly different from each other (P <0.05). Bone regeneration averaged 1.5 +/- 0.5, 1.7 +/- 0.6, and 2.3 +/- 0.5 mm for the 1-, 2-, and 3-wall defects, respectively, with the 3-wall defects being significantly different from the 1-wall defects (P <0.05). CONCLUSIONS: The results suggest that the number of bone walls is a critical factor determining treatment outcomes in intrabony periodontal defects. One- and 3-wall intrabony defects appear to be reproducible models to evaluate candidate technologies for periodontal regeneration.     

Periodontal response to orthodontic tooth movement in diabetes‐induced rats with or without periodontal disease

1 Background

Systemic conditions can influence orthodontic tooth movement. This study evaluates histologic periodontal responses to orthodontic tooth movement in diabetes‐induced rats with or without periodontal disease.

2 Methods

Forty Wistar rats were divided according their systemic condition (SC) into diabetic (D) and non‐diabetic (ND) groups. Each group was subdivided into control (C), orthodontic tooth movement (OM), ligature‐induced periodontitis (P) and ligature‐induced periodontitis with orthodontic movement (P+OM) groups. Diabetes mellitus (DM) was induced with alloxan monohydrate, and after 30 days, the P group received a cotton ligature around their first lower molar crown. An orthodontic device was placed in OM and P+OM groups for 7 days, and the animals were then euthanized.

3 Results

Differences in OM between D and ND groups were not significant (6.87± 3.55 mm and 6.81 ± 3.28 mm, respectively), but intragroup analysis revealed statistically significant differences between the P+OM groups for both SCs. Bone loss was greater in the D group (0.16 ± 0.07 mm²) than in the ND group (0.10 ± 0.03 mm²). In intragroup analysis of the D condition, the P+OM group differed statistically from the other groups, while in the ND condition, the P+OM group was different from the C and OM groups. There was a statistically significant difference in bone density between D and ND conditions (18.03 ± 8.09% and 22.53 ± 7.72%) in the C, P, and P+OM groups.

4 Conclusion

DM has deleterious effects on bone density and bone loss in the furcation region. These effects are maximized when associated with ligature‐induced periodontitis with orthodontic movement.     

Orthodontic tooth movement after different coxib therapies

Anti-inflammatory substances used for treatment of pain and discomfort related to orthodontic treatment (OT) could slow down tooth movement. Selective cyclooxygenase-2 inhibitors are an alternative to conventional non-steroidal anti-inflammatory drugs. The aim of this study was to compare different coxibs on dental movement in the rat. Twenty-eight Wistar male rats (3 months old) divided into four experimental groups were studied: (1) Five rats underwent a 50 g coil spring implantation and received three injections of 0.5 mg/kg body weight (bw) of Rofecoxib in the maxillary gingiva, close to the first molar, on the day of implantation and after 3 and 5 days. Similar procedures were carried out (2) on six animals receiving 8 mg/kg bw of Celecoxib and (3) on five animals receiving 25 mg/kg bw of Parecoxib. (4) For the controls, 12 rats received the same OT but only equivolumetric 0.9 per cent saline solution injections. Tooth movement was measured on lateral cranial teleradiographs after 10 days of treatment. Non-parametric standard techniques (Wilcoxon, H, and Mann-Whitney, U) were used for statistical analysis. Mesial tooth displacement in the control animals was 0.33 +/- 0.07 mm. While no movement was found in rats treated with Rofecoxib, the Celecoxib- and Parecoxib-treated rats showed tooth movement of 0.42 +/- 0.09 mm and 0.22 +/- 0.04 mm, respectively. The differences were statistically significant (H = 13.07; P < 0.004). Celecoxib and Parecoxib, but not Rofecoxib, seem appropriate for discomfort and pain relief while avoiding interference during tooth movement.     

Changes in response properties of periodontal mechanoreceptors after experimental orthodontic tooth movement in rats

Using an in vitro preparation, we investigated chronological changes in response properties of periodontal mechanoreceptors (PMRs) in the rat right mandibular first molar (M1) after experimental orthodontic tooth movement. Orthodontic force was applied to M1 for 14 days by activating 24.5 mN superelastic titanium-nickel alloy closed coil springs anchored to the mandibular incisors. Experiments were performed on days 3, 7, 10, and 14 during application of orthodontic force and on days 7, 14, 21, and 28 after removal of orthodontic force. The rats without application of orthodontic force were used as control group. In each group, direct mechanical stimulation using von Frey hairs and electrical stimulation was applied to the distal root of M1. Results showed that compared with controls (1) the mechanical thresholds were significantly lower during application of orthodontic force; however, no significant difference was found after removal of force application and (2) conduction velocities were significantly lower from day 7 during application of orthodontic force to day 14 after removal of orthodontic force; however, no significant difference was found on days 21 and 28 after removal of orthodontic force. These results suggest that the PMRs, although having some of their response properties altered during orthodontic force application, were able to recover and adapt to the newly acquired intraoral condition after removal of the orthodontic force.     

下颌骨牵引成骨区即刻牙移动的实验研究

目的：研究下颌骨牵引成骨后在新骨区即刻牙移动时牙周组织的改建行为及牙移动规律。方法：选择4只牙列完整的Beagle犬,其中2只犬建立双侧下颌骨牵引成骨动物模型,牵引完成后,即刻以30g力远中移动下颌第三前磨牙进入牵引成骨区;另外2只犬拔除双侧下颌第四前磨牙后3个月,以30g力远中移动下颌第三前磨牙。实验中,每周加力1次拍摄X线片,并记录牙移动速率。牙移动8周后,观察实验牙及其牙周组织特点。测量数据采用SPSS12.0软件包进行t检验。结果：实验牙借助自制的持续加力装置移动进入牵引成骨区,实验牙未产生倾斜,牙无明显松动,牙根未见明显吸收。实验组牙移动速度显著快于对照组,P〈0.01。组组织学观察发现,牙槽骨和牙周膜未出现不可逆性损伤。结论：牵引成骨区的新生骨质中,牙可以快速而平稳地移动。