Injectable simvastatin in periodontal defects and alveolar ridges: pilot studies

BACKGROUND: Topical injection of simvastatin in methylcellulose gel was shown to stimulate bone growth and inflammation over mouse calvaria and in rat mandible models. The purpose of these pilot studies was to evaluate the potential of locally injected simvastatin in human-sized periodontal defects. METHODS: Chronic periodontal defects were created bilaterally in seven 1-year-old beagle dogs: 3-walled intrabony defects distal of the mandibular second premolar and mesial of the fourth premolar and Class II furcation defects at the buccal furcation of the mandibular first molars. The edentulous space distal to the mandibular canine was left undisturbed. After 16 weeks of healing, defect sites were treated with scaling and root planing, and mandible sides were randomly selected to receive three weekly injections of 0.5 mg simvastatin in 30 microl methylcellulose gel and contralateral gel alone (n=3) or 2.0 mg simvastatin/methylcellulose gel and contralateral gel alone (n=4). Two months following drug application, block sections, including teeth and surrounding tissues, and submandibular lymph nodes were obtained for histomorphometric analysis. RESULTS: Two trends were noted in this pilot study: buccal edentulous ridge thickness was 29% greater with simvastatin, 0.5 mg, compared to gel alone (P=0.0845), and the simvastatin groups had bone-height loss in interproximal intrabony and furcation defects, but the length of new cementum in the interproximal intrabony defects was greater with simvastatin, 0.5 mg (0.35+/-0.14 mm), compared to gel alone (0.06+/-0.15 mm; P=0.069). No new cementum was found in furcations. CONCLUSIONS: Multiple injections of simvastatin are not appropriate for the treatment of intrabony or furcation defects. However, this approach shows potential to augment bone thickness in closed alveolar environments.     

Guided tissue regeneration. An experimental procedure in beagle dogs

This preliminary study examined the healing following an experimental procedure designed to facilitate coronal migration of progenitor cells from the periodontal ligament circumferentially on roots of premolar teeth in beagle dogs. Mucoperiosteal flaps were reflected on the buccal and lingual aspects of premolars in six beagle dogs with periodontal disease. Following root preparation, pieces of orthodontic wire were placed interproximally on the crowns to bridge the spaces between teeth. Biobrane, a synthetic membrane bonded to a knitted nylon fabric and coated with collagen, was placed as a physical barrier between the roots and the flaps to be replaced. The membrane extended as a single piece from the cementoenamel junction (CEJ) to overlap the crest of alveolar bone by 3 to 4 mm on both the buccal and lingual surfaces of the three premolars in each quadrant. The membrane was attached to the crowns at the CEJ with resin. The flaps were replaced and sutured. Postoperative care included plaque control and the membranes were removed after 5 weeks. The dogs were sacrificed to provide observation periods of 8 and 16 weeks after placement of membranes. Histologic examination revealed new connective tissue attachment in the apical part of the 8- and 16-week experimental specimens. Some experimental specimens showed new attachment up to 2.94 mm while others showed a long junctional epithelium (JE). Root resorption was also seen in some specimens. These preliminary findings suggest that placement of physical barriers between root surface and flaps may be beneficial in facilitating coronal migration of progenitor cells from the periodontal ligament.     

Cortical bone thickness in dentate and edentulous human cadavers

BACKGROUND: A critical component of treatment planning in dental implant therapy is the amount of available bone. Thick cortical plates have been the primary way to achieve primary implant stability. However, information about cortical bone thickness in various regions of the maxilla and mandible is largely missing. Hence, it was the purpose of this cadaver study to determine an average cortical bone thickness in different tooth locations. METHODS: To determine the average thickness of buccal and lingual plates, 28 cadaver heads (68% male and 32% female) with an average age of 73.1 years were measured at various locations correlating to molar (M), premolar (PM), and anterior (A) regions. Edentulous and dentate regions also were recorded. RESULTS: Average buccal cortical thicknesses were 1.69 mm (M), 1.43 mm (PM), and 1.04 mm (A) in the edentulous maxilla; 2.06 mm (M), 1.78 mm (PM), and 1.36 mm (A) in the edentulous mandible; 2.23 mm (M), 1.62 mm (PM), and 1.59 mm (A) in the dentate maxilla; and 1.98 mm (M), 1.20 mm (PM), and 0.99 mm (A) in the dentate mandible. Average lingual cortical thicknesses were 2.06 mm (M), 1.60 mm (PM), and 1.36 mm (A) in the edentulous maxilla; 2.39 mm (M), 1.88 mm (PM), and 1.66 mm (A) in the edentulous mandible; 2.35 mm (M), 2.0 mm (PM), and 1.95 mm (A) in the dentate maxilla; and 2.51 mm (M), 1.92 mm (PM), and 1.24 mm (A) in the dentate mandible. CONCLUSIONS: The average cortical thickness of the buccal plates ranged from 1.0 to 2.1 mm in the edentulous maxilla and mandible, with the thinnest area in the anterior maxilla and the thickest area in the posterior mandible. The buccal plate of the dentate maxilla and mandible ranged from 1.6 to 2.2 mm in thickness, with the thinnest area in the lower anterior region and the thickest area in the upper posterior region.     

Can posterior teeth of patients be translated buccally,and does bone form on the buccal surface in response?

Objective:To produce buccal translation and determine whether buccal bone forms on the cortical surfaces.Materials and Methods:Eleven patients requiring maxillary first premolar extractions participated in this prospective, randomized, split-mouth study. Pre- and posttreatment records included models, photographs, and small field of view CBCT images. One randomly chosen maxillary first premolar was moved buccally with 50 g of force applied approximately at the tooth’s center of resistance. The other premolar served as the control. Forces were re-activated every 3 weeks for approximately 9 weeks, after which the teeth were held in place for 3 weeks. Pre- and posttreatment records were analyzed and superimposed to evaluate changes in the dental-alveolar complex.Results:There was significant (P < .05) movement of the experimental premolar with minimal buccal tipping (2.2°). Changes in maximum bone height were bimodal, with 6 patients showing 0.42 mm and 5 patients showing 8.3 mm of vertical bone loss. Buccal bone thickness 3 mm apical to the CEJ decreased 0.63 mm. Direct measurements and CBCT superimpositions showed that buccal bone over the roots grew 0.46 mm and 0.51 mm, respectively.Conclusions:It is possible to produce buccal bodily tooth movement with only limited amounts of tipping. Such movements are capable of producing buccal bone apposition, but there are potential limitations.     

Efficacy of Using PDGF and Xenograft With or Without Collagen Membrane for Bone Regeneration Around Immediate Implants With Induced Dehiscence‐Type Defects: A Microcomputed Tomographic Study in Dogs

Background: Use of collagen membrane (CM) with xenograft and recombinant human platelet‐derived growth factor (rhPDGF) in guided bone regeneration (GBR) is debatable. The aim of this microcomputed tomographic experiment was to assess the efficacy of using PDGF and xenograft (with or without CM) for GBR around immediate implants with dehiscence defects. Methods: Ten beagle dogs underwent atraumatic bilateral second and fourth premolar extractions from both arches. A standardized dehiscence defect (6 × 3 mm) was created on the buccal bone and immediate implants were placed in distal sockets in each site. Animals were randomly divided into three groups: 1) group 1, xenograft with rhPDGF was placed and covered with CM; 2) group 2, xenograft with rhPDGF was placed over the defects; and 3) group 3, four immediate implants were associated with dehiscence (controls). After 16 weeks, animals were sacrificed and jaw segments were assessed for buccal bone thickness (BBT), buccal bone volume (BBV), vertical bone height (VBH), and bone‐to‐implant contact (BIC) using microcomputed tomography. Results: BBT was higher in group 2 (1.533 ± 0.89 mm) than group 1 (0.745 ± 0.322 mm) (P <0.001) and group 3 (0.257 ± 0.232 mm) (P <0.05). BBV was higher in group 2 (67.87 ± 19.83 mm³) than group 1 (42.47 ± 6.78 mm³) (P <0.05) and group 3 (19.12 ± 4.06 mm³) (P <0.001). VBH was higher in group 2 (6.36 ± 1.37 mm) than group 3 (0.00 ± 0.00 mm) (P <0.001). VBH was higher in group 1 (3.91 ± 2.68 mm) than group 3 (0.00 ± 0.00 mm) (P <0.05). BIC was higher in group 2 (67.25% ± 13.42%) than group 1 (36.25% ± 12.78%) (P <0.05) and group 3 (30.25% ± 7.27%) (P <0.01). Conclusion: GBR around immediate implants with dehiscence defects using PDGF and xenograft alone resulted in higher BBT, BBV, VBH, and BIC than when performed in combination with CM.     

尖牙远中微植体支抗植入区域口腔颌面部锥形束CT测量分析

目的:通过测量上、下颌骨尖牙与第一前磨牙之间不同水平处颊侧骨皮质的厚度以及根间距离,为微植体支抗植入的最佳位点提供依据。方法:随机选择武汉大学口腔医院就诊患者的口腔颌面部锥形束CT影像资料29例,测量双侧上、下颌骨尖牙与第一前磨牙间距离牙槽嵴顶3 mm、4 mm、5 mm、6 mm、7 mm不同水平处颊侧骨皮质的厚度及根间距离,并对测量数据进行统计分析。结果:上下颌尖牙与第一前磨牙间3~7 mm水平骨皮质厚度均大于1 mm,上颌自3 mm向根尖骨皮质厚度逐渐增加,下颌4 mm处骨皮质最薄,自5 mm向根尖方向骨皮质厚度逐渐增加。上下颌尖牙与第一前磨牙间3~7 mm水平牙根间距均大于2 mm,上、下颌骨距牙槽嵴顶3 mm处牙根间距最短,向根尖方向根间距离逐渐增大;双侧上下颌骨3~7 mm各水平骨皮质厚度及根间距离的差异没有统计学意义。结论:上下颌尖牙远中区在距离牙槽嵴顶≥3 mm处骨质可作为微植体的安全植入区域;通过口腔颌面部锥形束CT对微植体植入区域骨皮质厚度及根间距离的测量分析,可以向临床提供精确的数据支持。     

Correction of Buccal Dehiscence During Immediate Implant Placement Using the Flapless Technique: A Tomographic Evaluation

Background: The aim of this study was to evaluate a new technique for treating dehiscence buccal bone sites (Class II) with immediate implant and collagen‐enriched bovine‐derived xenograft blocks without a surgical flap or membrane. Methods: Individuals with at least 5 mm of buccal bone dehiscence were selected for a flapless surgical approach to insert xenograft blocks into buccal dehiscence defects as well as the gap between implant and residual bone wall. No membrane was used. Buccal bone wall height was measured by computed tomography in the preoperative period (T0) and 6 to 12 months after procedure (T1). Likewise, buccal‐lingual width of alveolar ridge as well as thickness of buccal wall was compared with the contralateral tooth. Results: Fourteen patients were selected. Buccal wall height at T1 was not significantly different after 6 to 12 months between the treated and contralateral teeth, although both were greater than T0 (P <0.01). The heights ranged from 6.4 to 16.30 mm at T0, 12.8 to 25.6 mm at T1, and 14.8 to 25.29 mm in the contralateral teeth. Significant differences were observed between treated teeth (T1) and their contralateral, both buccal‐lingually in the alveolar ridge (P = 0.007) and in buccal wall thickness (P = 0.003). Wall thickness ranged from 0.9 mm to 3.81 mm at T1 and 0.25 mm to 1.60 mm in the contralateral teeth. Conclusion: Immediate implant placement at dehiscence buccal bone sites using flapless surgery combined with xenograft blocks provided complete formation of the buccal bone wall up to the implant shoulder.     

Guided tissue regeneration following treatment of recession-type defects in the monkey

Recent studies have demonstrated extensive amounts of new attachment formation following reconstructive surgery based on the biological principle of guided tissue regeneration (GTR). The aim of the present investigation was to evaluate the effect of using a polytetrafluorethylene (PTFE) membrane in GTR-treatment of recession-type defects and to examine the interrelationship between the PTFE membrane and surrounding periodontal tissues. Full-thickness flaps were raised around 24 maxillary premolar and molar teeth in 6 monkeys. The buccal alveolar bone was surgically removed to a level corresponding to the apical third of the roots. The exposed root surfaces were scaled and planed. In 12 teeth, PTFE membranes were adjusted to cover the exposed root surfaces from a level 1 to 2 mm apical to the CEJ, to a level 3 to 4 mm apical to the alveolar crest. The coronal border of the membranes was tightly adapted to the root surfaces by sling sutures. Twelve teeth served as control teeth without placement of membranes. The flaps were placed with the margin coronal to the CEJ and sutured. The animals were sacrificed after 3 months of healing and all experimental teeth were subjected to histological analysis. The membranes were found to be incorporated with the surrounding connective tissue, and the apical extension of the junctional epithelium terminated at the coronal border of the membranes. The amount of new attachment formation was on the average 74.3% of the defect height in the test teeth, which corresponded to 100% of the membrane covered root portion. Newly formed connective tissue attachment in the controls amounted to an average of 36.9% of the defect height.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ridge alterations following implant placement in fresh extraction sockets: an experimental study in the dog

OBJECTIVE: To study dimensional alterations of the alveolar ridge that occurred following implant placement in fresh extraction sockets. MATERIAL AND METHODS: Five beagle dogs were included in the study. In both quadrants of the mandible, incisions were made in the crevice region of the third and fourth pre-molars. Buccal and minute lingual full-thickness flaps were elevated. The mesial root of the four pre-molars root was filled and the teeth were hemi-sected. Following flap elevation in (3)P(3) and (4)P(4) regions, the distal roots were removed. In the right jaw quadrants, implants with a sand blasted and acid etched (SLA) surface were placed in the fresh extraction sockets, while in the left jaws the corresponding sockets were left for spontaneous healing. The mesial roots were retained as surgical control teeth. After 3 months, the animals were examined clinically, sacrificed and tissue blocks containing the implant sites, the adjacent tooth sites (mesial root) and the edentulous socket sites were dissected, prepared for ground sectioning and examined in the microscope. RESULTS: At implant sites, the level of bone-to-implant contact (BC) was located 2.6+/-0.4 mm (buccal aspect) and 0.2+/-0.5 mm (lingual aspect) apical of the SLA level. At the edentulous sites, the mean vertical distance (V) between the marginal termination of the buccal and lingual bone walls was 2.2+/-0.9 mm. At the surgically treated tooth sites, the mean amount of attachment loss was 0.5+/-0.5 mm (buccal) and 0.2+/-0.3 mm (lingual). CONCLUSIONS: Marked dimensional alterations had occurred in the edentulous ridge after 3 months of healing following the extraction of the distal root of mandibular pre-molars. The placement of an implant in the fresh extraction site obviously failed to prevent the re-modelling that occurred in the walls of the socket. The resulting height of the buccal and lingual walls at 3 months was similar at implants and edentulous sites and vertical bone loss was more pronounced at the buccal than at the lingual aspect of the ridge. It is suggested that the resorption of the socket walls that occurs following tooth removal must be considered in conjunction with implant placement in fresh extraction sockets.     

Dimension of the facial bone wall in the anterior maxilla: a cone-beam computed tomography study

Objective: To determine the thickness of the facial bone wall in the anterior dentition of the maxilla and at different locations apical to the cemento‐enamel junction (CEJ). Material and methods: Two‐hundred and fifty subjects, aged between 17 and 66 years, with all maxillary front teeth present were included. Written informed consents were obtained. Cone‐beam computed tomography scans were performed with the iCAT unit. This examination included all tooth and edentulous sites in the dentition. The images were acquired by means of the iCAT software and processed by a computer. Measurements of the (i) distance between the CEJ and the facial bone crest and (ii) the thickness of the facial bone wall were performed. The bone wall dimensions were assessed at three different positions in relation to the facial bone crest, i.e., at distances of 1, 3, and 5 mm apical to the crest. Results: The measurements demonstrated that (i) the distance between the CEJ and the facial bone crest varied between 1.6 and 3 mm and (ii) the facial bone wall in most locations in all tooth sites examined was ≤1 mm thick and that close to 50% of sites had a bone wall thickness that was ≤0.5 mm. Conclusion: Most tooth sites in the anterior maxilla have a thin facial bone wall. Such a thin bone wall may undergo marked dimensional diminution following tooth extraction. This fact must be considered before tooth removal and the planning of rehabilitation in the anterior segment of the dentition in the maxilla. To cite this article:
Januário AL, Duarte WR, Barriviera M, Mesti JC, Araújo MG, Lindhe J. Dimension of the facial bone wall in the anterior maxilla: a cone‐beam computed tomography study.
Clin. Oral Impl. Res. 22 , 2011; 1168–1171
doi: 10.1111/j.1600‐0501.2010.02086.x.
10.1111/j.1600‐0501.2010.02086.x     

Periodontal response to long-term abuse of the gingival attachment by supracrestal amalgam restorations

The combined length of the supracrestal connective tissue attachment and the junctional epithelium is referred to as the "biologic width". The long-term (1-year) effect of complete violation of the supracrestal connective tissue attachment was examined in beagle dogs. Full thickness periodontal flaps were elevated, exposing the buccal bony crests of the maxillary and mandibular canines of 3 beagle dogs. The roots of the experimental teeth were planed and class V cavities were prepared. The apical border of each cavity was located at the alveolar bone crest. The cavities were restored with amalgam and the flaps were repositioned and sutured. In the control sites, a notch was prepared at the CEJ and the distance between the notch and the bony crest was measured. The dogs were sacrificed 57 weeks after the operation and the experimental and control sites prepared for histologic analysis. Every 5th section was examined and measurements were taken of the amount of gingival and bone recession, the length of the connective tissue and the epithelial attachment. Control sites healed uneventfully. Gingival recession averaged only 0.5 mm; bone loss was minimal and averaged 0.15 mm. The combined length of the supracrestal connective tissue and epithelial attachment measured 4.47 mm. In experimental sites, the gingiva receded 3.16 mm on average. Moderate bone loss (mean = 1.17 mm) was noted, but no signs of bone resorption were seen at the time of sacrifice. After bone loss, root surfaces which were previously attached to alveolar bone by periodontal ligament were mainly (0.90 mm) attached to connective tissue.(ABSTRACT TRUNCATED AT 250 WORDS)     

Alveolar ridge dimensions in maxillary posterior sextants: a retrospective comparative study of dentate and edentulous sites using computerized tomography data

Aim: To compare the alveolar ridge dimensions between edentulous sites and contralateral dentate sites of maxillary posterior sextants in the same individuals. Materials and methods: Computerized tomography scans of 32 patients with one fully edentulous and one fully dentate maxillary posterior sextants were analyzed. Results: When compared with dentate sextants, edentulous sextants showed (i) a lower bone height (BH) at second premolar, first molar and second molar sites, which was associated with a more coronal position of the maxillary sinus floor at second premolar site; (ii) a more apical position of the ridge at second premolar and second molar sites; (iii) a lower bone width (BW)_{1 mm} at first and second premolar sites, and a lower BW_{3 mm} at all sites, (iv) a lower, although not significant, prevalence of premolar and molar sites with BH≥8 mm and BW_{1 mm}≥6 mm. Conclusions: The edentulous sextants in the posterior maxilla showed a reduced height and width of the ridge when compared with contralateral dentate sextants. The reduced vertical dimensions observed in edentulous sextants were variably associated with ridge resorption as well as sinus pneumatization. To cite this article:
Farina R, Pramstraller M, Franceschetti G, Pramstraller C, Trombelli L. Alveolar ridge dimensions in maxillary posterior sextants: a retrospective comparative study of dentate and edentulous sites using computerized tomography data.
Clin. Oral Impl. Res. 22 , 2011; 1138–1144.
doi: 10.1111/j.1600‐0501.2010.02087.x     

Impact of Local and Systemic Alendronate on Simvastatin‐Induced New Bone Around Periodontal Defects

Background: Simvastatin has been shown to stimulate new bone growth on rat mandibles, but much of the bone is lost over time. The purpose of this study is to evaluate the impact of a locally or systemically applied antiresorptive agent (alendronate) on simvastatin‐induced bone formation in and adjacent to a rat periodontal defect. Methods: Fenestration defects were created over mandibular molar roots in 65 mature female Sprague‐Dawley rats. Two weeks later, animals were divided into eight groups of eight to nine rats, and three weekly injections around the defect were applied: 1) 0.5 mg simvastatin in ethanol (SIM‐EtOH); 2) 0.5 mg simvastatin in alendronate–cyclodextrin conjugate (SIM‐ALN‐CD); 3) EtOH alone; 4) ALN‐CD alone; or 5) no injections. Twenty‐four animals were evaluated for new bone width around the defect 21 days after the last injections (short‐term) and 41 rats were followed for 48 days (long‐term). Three SIM‐EtOH groups of long‐term rats also were subjected to 2 weeks of daily systemic ALN or saline either during or 3 to 4 weeks after SIM‐EtOH injections. Decalcified, hematoxylin‐and‐eosin‐stained cross‐sections of the defect area were analyzed for new bone width and groups were compared using mixed‐model analyses of variance. Results: All groups showed nearly 100% bone fill, with no differences among the short‐term groups. However, in the long‐term animals, two‐fold to three‐fold more new bone width (≤0.004) was seen around the periphery of the defect with the use of systemic ALN after SIM‐EtOH injections (0.93 ± 0.12 and 0.78 ± 0.11 mm with early and late systemic ALN, respectively) compared to local SIM/ALN‐CD preparations (0.32 ± 0.10 mm) or short‐term SIM‐EtOH injections (0.35 ± 0.10 mm). No significant new cementum formation or ankylosis was noted. Conclusion: The use of a short course of systemic ALN during the healing period after bone anabolic SIM injections has the potential to enhance local bone augmentation.     

The thickness of facial alveolar bone overlying healthy maxillary anterior teeth

Background: A facial bone (<2 mm) overlying maxillary anterior teeth may be prone to resorptive processes after extraction and immediate implant placement. A thin bone contributes to risk of bone fenestration, dehiscence, and soft‐tissue recession. This study measures the distance between the cemento‐enamel junction (CEJ) and alveolar bone crest and the thickness of facial alveolar bone at points 1 to 5 mm from the bone crest for the six maxillary anterior teeth. Methods : Sixty‐six tomographic scans (31 males and 35 females; aged 17 to 69 years; mean age: 39.9 years) of intact anterior maxilla were randomly selected and evaluated by two calibrated and independent examiners (MG and TP). Results: A high variation of CEJ–bone crest (0.8 to 7.2 mm) was detected. A significantly larger CEJ–bone crest was measured in smokers (P <0.05) and patients who were ≥50 years old (P <0.05). The average bone thickness at 3 mm from the CEJ for the maxillary right central incisor was 1.41 mm and for the maxillary left central incisor was 1.45 mm. For the maxillary right and left lateral incisors, the crestal bone thickness averaged 1.73 and 1.59 mm, respectively. For the maxillary right and left canines, the crestal bone thickness averaged 1.47 and 1.60 mm, respectively. Conclusions : The present study supports the finding of a predominantly thin facial bone overlying the six maxillary anterior teeth. Therefore, it is essential to make informed treatment decisions based on thorough site evaluation before immediate implant placement.     

A study of the internal structure of the Japanese edentulous mandible

With the aim of improving understanding of the transition the mandible internal structure undergoes between the dentulous and edentulous states, the thickness of the substantia compacta, the ratio of trabecular bone to the total substantia spongiosa, and the thickness of the trabecular bone were measured in 9 edentulous mandibles aged 45 to 65 years. The measurements were made with an image-treatment device outfitted with a personal computer. Results 1. Thickness of the substantia compacta The thickest zones (3.00-3.81 mm) were located on the lingual side of the anterior teeth; the second thickest zones (2.20-2.48 mm) were located on the superior lingual and buccal side of the molars. The thinnest zones (1.66-1.67 mm) were located on the labial side of the anterior teeth; the second thinnest zones (1.71-1.75 mm) were located on the buccal side of the premolars. Little difference (1.90-2.18 mm) was observed in the bases of the mandibular areas. In the region of the lingual side, the thickest zones occurred in the premolars. Little difference in thickness was observed between the premolar and molar zones. On the labial-buccal side, thicknesses increased from the premolar to the molar zones (which were the thickest) and decreased gradually from the mental to the premolar zones. Comparisons showed that the anterior teeth zoon in the edentulous mandible the substantia compacta is thinner on the labial side and thicker on the lingual side than it is in the dentulous mandible. Little difference between the dentulous and edentulous mandibles was observed in the lingual side of the molar zone, although the buccal side was thinner in the edentulous than in the dentulous mandible. 2. Ratio of trabecular bone to the total substantia spongiosa The highest ratios (74.03-89.62%) occurred in the mental zone; the second highest (69.07-82.92%) occurred in the incisor zone. The lowest ratios (30.61-39.61%) occurred in the superior and middle regions of the premolar zone. The inferior area of the premolar zone, however, was relatively wider (42.83-55.66%) than the superior and middle areas. The following ratios of trabecular bone to total substantia spongiosa were observed: The highest ratio occurred in the zone of the anterior teeth, the next highest ratio in the molar zone, and the lowest ratio in the premolar zone. Although, differences in ratios between dentulous and edentulous mandibles were only slight, a lower ratio occurred in the inferior area of the premolar zone. 3. Thickness of trabecular bone within the substantia spongiosa.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ridge dimensions of the edentulous posterior maxilla: a retrospective analysis of a cohort of 127 patients using computerized tomography data

Objectives: To evaluate the edentulous ridge dimensions of maxillary posterior sextants with a tridimensional radiographic technique. The influence of the presence/absence of teeth adjacent to the edentulous site on the dimensions of the edentulous ridge was also evaluated. Material and methods: Computerized tomography (CT) scans of 127 patients (65 males and 62 females; mean age: 55.2±10.1 years) with at least one missing tooth in the maxillary posterior sextants were analyzed. On CT cross sections, bone height (BH), bone width (BW) at 1, 3, and 7 mm from the most coronal point of the alveolar crest (BW_{1 mm}, BW_{3 mm}, and BW_{7 mm}, respectively) and the relative vertical ridge position (rVRP) were assessed at the first premolar, second premolar, first molar and second molar edentulous sites. Results: The results of the study indicate that (i) the maxillary sinus was radiographically evident in about 50% of first premolar sites and 90–100% of second premolar and molar sites; (ii) BH showed a significant decrease from first premolar to molar sites; (iii) BW_{1 mm} was higher at second molar site compared with the first and second premolar sites, BW_{3 mm} and BW_{7 mm} were higher at each molar site compared with each premolar site; (iv) the proportion of sites with BH≥8 mm and BW_{1 mm}≥6 mm was 86.7%, 59.2%, 19.8% and 34.8% at first premolar, second premolar, first molar and second molar sites, respectively. The absence of teeth adjacent to the edentulous site negatively affected rVRP, but not BH and BW. Conclusions: The results of the study indicate that at second premolar as well as molar sites, the dimensions of the alveolar crest may call for bone augmentation procedures for proper implant placement in a substantial amount of edentulous patients. When both mesial and distal tooth adjacent to the edentulous site are absent, the placement of implants of adequate dimensions may be more challenging due to a more apical position of the alveolar ridge compared with sites where both adjacent teeth are present. To cite this article:
Pramstraller M, Farina R, Franceschetti G, Pramstraller C, Trombelli L. Ridge dimensions of the edentulous posterior maxilla: a retrospective analysis of a cohort of 127 patients using computerized tomography data.
Clin. Oral Impl. Res. 22 , 2011; 54–61.
doi: 10.1111/j.1600‐0501.2010.01984.x     

Buccal Bone Formation After Flapless Extraction: A Randomized,Controlled Clinical Trial Comparing Recombinant Human Bone Morphogenetic Protein 2/Absorbable Collagen Carrier and Collagen Sponge Alone

Background: Flapless extraction of teeth allows for undisturbed preservation of the nearby periosteum and a source of osteoprogenitor cells. Recombinant human bone morphogenetic protein 2 (rhBMP‐2) has been used for different bone augmentation purposes with great osteoinductive capacity. The aim of this study is to compare the bone regenerative ability of rhBMP‐2 on an absorbable collagen sponge (ACS) carrier to a collagen sponge (CS) alone in extraction sites with ≥50% buccal dehiscence. Methods: Thirty‐nine patients requiring extraction of a hopeless tooth with ≥50% buccal dehiscence were enrolled. After flapless extraction and randomization, either rhBMP‐2/ACS carrier or CS alone was placed in the extraction site. After extraction, a baseline cone beam computed tomography (CBCT) scan was obtained of the site, and a similar scan was obtained 5 months postoperatively. Medical imaging and viewing software were used to compare the baseline and 5‐month postoperative images of the study site and assess ridge width measurements, vertical height changes, and buccal plate regeneration. Results: Radiographically, CBCT analysis showed that with ≥50% of buccal bone destruction, rhBMP‐2/ACS was able to regenerate a portion of the lost buccal plate, maintain theoretical ridge dimensions, and allow for implant placement 5 months after extraction. The test group performed significantly (P <0.05) better in regard to clinical buccal plate regeneration (4.75 versus 1.85 mm), clinical ridge width at 5 months (6.0 versus 4.62 mm), and radiographic ridge width at 3 mm from the alveolar crest (6.17 versus 4.48 mm) after molar exclusion. There was also significantly (P <0.05) less remaining buccal dehiscence, both clinically (6.81 versus 10.0 mm) and radiographically (3.42 versus 5.16 mm), at 5 months in the test group. Significantly (P <0.05) more implants were placed in the test group without the need for additional augmentation. The mean loss in vertical ridge height (lingual/palatal) was less in the test sites but was not significantly (P = 0.514) different between the test and control groups (0.39 versus 0.64 mm). Conclusions: rhBMP‐2/ACS compared to CS alone used in flapless extraction sites with a buccal dehiscence is able to regenerate lost buccal plate, maintain theoretical ridge dimensions, and allow for implant placement 5 months later.     

Root surface measurements of the mandibular first molar

The root surface area (RSA) per millimeter of root length was determined for 20 extracted mandibular first molars. The molars were cross-sectioned at 1-mm increments, and each section photographed, projected and measured with a calibrated opisometer. The RSA and per cent RSA were calculated for each 1 mm of root length (1-mm section), the root trunk and the individual roots. Also measured was the location of the root separations from the root trunk, the location of the first detectable root concavity, and the prevalence of "intermediate bifurcation ridges" (IBRs). Mean measurements indicated that the greatest RSA per millimeter of root length was 4 to 7 mm apical to the cementoenamel junction (CEJ) in the area of the furcation. Of the total RSA, 48.7% was located in the coronal 6 mm of a root (mean length, 14.4 mm). Root separation occurred 4.0 mm apical to the CEJ with no tooth having a root trunk longer than 6 mm. Buccal and lingual root concavities were first present 0.7 mm and 0.3 mm apical to the CEJ, respectively. Fourteen (70%) of the 20 teeth had IBRs. According to the mean measurements, the mesial root was larger than the distal root by a ratio of 1.0:0.88. Horizontal attachment loss of 6 mm affecting both the buccal and lingual surfaces of the mandibular first molar would have resulted in a through and through (grade 3) furcation involvement of all the teeth studied.     

HISTOMETRIC ANALYSIS OF LIGATURE-INDUCED PERIODONTITIS IN RATS: A COMPARISON OF HISTOLOGICAL SECTION PLANES

The purpose of this study was to analyze the histometry of ligature-induced periodontitis in rats at different histological section depths. Sixteen male adult Wistar rats were randomly assigned to two groups: ligature and control. In the ligature group, rats received a sterile 4/0 silk ligature around the maxillary right 2nd molar. Thirty serial sections containing the 1st and 2nd molars, in which the coronal and root pulp, cementoenamel junction (CEJ) in the mesial side of the 2nd molar, interproximal alveolar bone and connective fiber attachment were clearly visible, were selected for histometric analysis. The histological sections were clustered in groups of 10 sections corresponding the buccal (B), central (C) and lingual (L) regions of the of periodontal tissue samples. The distance between the CEJ in the mesial side of the 2nd molar and the attached periodontal ligament fibers (CEJ-PL) as well as the distance between the CEJ and the alveolar bone crest (CEJ-BC) were determined. From CEJ-PL and CEJ-BC distances measured for each specimen, the measurements obtained in the B, L and C regions were recorded individually and together. Data were submitted to statistical analysis. Significant differences (p<0.001) were observed between the control and ligature groups regarding CEJ-PL (0.05 mm and 0.26 mm, respectively) and CEJ-BC (0.47 mm and 0.77 mm, respectively) measurements. Regarding the depth of the buccal, central and lingual planes, the means of CEJ-PL and CEJ-BC of both groups showed no statistically significant differences (p>0.05). In conclusion, the selection of 10 serial sections of the central region of periodontal tissue samples at any depth can be considered as representative for the evaluation of periodontal ligament fiber attachment and bone loss in ligature-induced periodontitis in rats.     

Effect of Simvastatin Prodrug on Experimental Periodontitis

Background: Local application of statins has shown potential in preventing and regenerating bone loss associated with experimental periodontitis. This study evaluates the effect of a novel simvastatin (SIM) prodrug (capable of delivering high doses to periodontitis inflammatory lesion and cells) on experimental periodontitis bone loss and inflammation. Methods: Forty mature female Sprague Dawley rats were subjected to ligature‐induced experimental periodontitis between maxillary first and second molars (M1‐M2). Equal groups were treated with three weekly doses of: 1) prodrug carrier alone (mPEG); 2) 0.5 mg SIM dose equivalent in carrier (SIM/SIM‐mPEG); 3) 1.0 mg SIM/SIM‐mPEG; 4) 1.5 mg SIM/SIM‐mPEG; or 5) ligature alone. Contralateral molars served as unmanipulated controls. Four weeks after initiation of periodontitis, animals were euthanized, the M1‐M2 interproximal was evaluated with microcomputed tomography and histology, and data were analyzed with one‐way analysis of variance. Results: Ligature alone caused a mean bone loss of 1.01 ± 0.06 mm from the cemento‐enamel junction, whereas all doses of SIM/SIM‐mPEG reduced bone loss, especially 1.5 mg SIM/SIM‐mPEG (0.68 ± 0.05 mm, P <0.001), which was not statistically different from contralateral control (0.47 ± 0.06 mm). A dose of 1.5 mg SIM/SIM‐mPEG also reduced percentage of neutrophils compared with carrier alone (2.0% ± 1.0% versus 5.7% ± 1.1%; P <0.05), and increased amount of uninflamed connective tissue in the M1‐M2 interproximal area (65.2% ± 3.3% versus 46.3% ± 3.3%; P <0.001). The mPEG carrier alone did not have bone‐sparing or anti‐inflammatory properties. Conclusion: Multiple local 1.5‐mg doses of a macromolecular SIM prodrug decreases amount of experimental periodontitis bone loss and inflammation in rats.