The influence of nicotine on the bone loss rate in ligature-induced periodontitis. A histometric study in rats

BACKGROUND: The present study investigated the possible influence of nicotine on the bone loss rate in the furcation region due to ligature-induced periodontitis in rats. METHODS: Twenty adult male Wistar rats were included. After anesthesia, the tooth was randomly assigned to receive the cotton ligature in the sulcular area, while the contralateral tooth was left unligated. The animals were randomly assigned to one of the following treatments, including daily intraperitoneal injections: group A, 2 microl/g body weight of saline solution; group B, 2 microl/g body weight of a nicotine solution with 0.13 microl of nicotine/ml of saline solution; group C, 2 microl/g body weight of a nicotine solution with 0.19 microl of nicotine/ml of saline solution; and group D, 2 microl/g body weight of a nicotine solution with 0.26 microl of nicotine/ml of saline solution. Thirty days later, the animals were sacrificed and the specimens routinely processed for serial decalcified sections. RESULTS: Intergroup analysis revealed greater bone loss in the ligated teeth of group B (1.01 +/- 0.61 mm2), group C (1.14 +/- 0.72 mm2), and group D (1.36 +/- 0.60 mm2) when compared with group A (0.64 +/- 0.62 mm2) (P <0.01). However, no statistically significant differences in bone loss were found among groups B, C, and D. In addition, no bone loss was observed for unligated teeth (P>0.01). CONCLUSIONS: Within the limits of the present study, nicotine enhanced the effects of the local components of periodontal disease in a non-dose-dependent way; nevertheless, the administration of nicotine did not produce periodontal bone loss by itself.     

尼古丁对实验性牙周炎大鼠牙槽骨影响的显微CT观察

目的 建立牙周炎大鼠的牙槽骨三维模型,采用显微CT观察尼古丁对大鼠牙槽骨的影响.方法 36只SD大鼠,丝线结扎上颌右侧(实验侧)第二磨牙颈部,左侧不予结扎,作为自身对照(对照侧),使用完全随机分组方法分为对照组(A)及尼古丁注射低剂量(B)和高剂量(C)组,每组12只.分别给予生理盐水和尼古丁0.83、1.67 mg·kg-1·d-1腹腔注射.每组分别于给药后第14、28天各处死6只,取双侧上颌磨牙区牙体牙周复合组织,行显微CT扫描、重建、测最和分析.结果 随尼古丁给药剂量增加,双侧牙槽骨骨密度、骨体积分数、骨小梁厚度逐渐降低,牙槽骨高度丧失与骨小梁间隙逐渐升高.28 d时C组牙槽骨高度丧失[对照侧和实验侧分别为(0.61±0.14)、(1.39±0.09)mm]显著高于B组[对照侧和实验侧分别为(0.39±0.10)、(1.31±0.06)mm]和A组[对照侧和实验侧分别为(0.30±0.06)、(0.94±0.07)mm];C组牙槽骨骨密度[对照侧和实验侧分别为(617.86±34.27)、(572.46±31.62)mg/cm3]显著低于B组[对照侧和实验侧分别为(660.04±36.73)、(604.97±32.59)mg/cm3]和A组[对照侧和实验侧分别为(709.15±34.95)、(657.04±30.06)mg/cm3].结论 尼古丁可加重丝线结扎造成的大鼠牙槽骨骨量丧失和骨质微观结构的变化,导致牙槽骨骨质疏松.     

兔咬合创伤时咬肌损伤与线粒体Ca2+载的研究

目的研究咬合创伤导致咬肌损伤的作用和线粒体Ca2+超载在损伤机制中的作用.方法在兔一侧前磨牙粘固(牙合)板造成咬合创伤,皮下注射乙二胺四乙酸(ethylenediarninetetraacetic Acid,EDTA),同时建立对照组,10天后检测兔咬肌线粒体Ca2+含量,观察咬肌的组织学改变,并进行比较分析.结果戴(牙合)板而不注射EDTA兔的(牙合)板侧咬肌线粒体Ca2+含量明显升高,并有明显的超微结构改变;(牙合)板对侧及戴(牙合)板并注射EDTA兔的双侧咬肌线粒体Ca2+含量均与对照组无显著性差异,组织学改变亦不明显.结论咬合创伤是咬肌损伤的致病因素之一,而线粒体Ca2+超载则是咬肌损伤发生机制中的一个重要环节.     

Histometric evaluation of the effect of nicotine administration on periodontal breakdown: an in vivo study

The present study investigated the effect of nicotine administration on periodontal breakdown resulting from ligature-induced periodontitis in rats. Twenty adult male Wistar rats were used. After anesthesia, a mandibular first molar was randomly assigned to receive a cotton ligature in the sulcular area while the contralateral tooth was left unligated. The animals were randomly assigned to one of the following treatments. of daily intraperitoneal injections: A - saline solution, B -0.37 mg of nicotine kg, C -0.57 mg of nicotine kg and D -0.73 mg of nicotine/kg. Thirty days later, the animals were sacrificed and the specimens routinely processed for serial decalcified sections. Statistical analysis (ANOVA) revealed greater bone loss (p<0.05) in the ligated teeth of animals which received nicotine (groups B/C D) than in the ligated teeth of animals which received saline solution (group A). In addition, a dose-dependent response was observed among the nicotine groups. A negative effect of nicotine was observed in the unligated teeth of the experimental groups (p<0.05). Therefore, daily administration of nicotine enhanced, in a dose-dependent manner, the effects of local factors in producing periodontal breakdown. Furthermore, the nicotine seemed to have a direct deleterious effect on the periodontal tissues.     

Micro‐computerized tomography analysis of alveolar bone loss in ligature‐ and nicotine‐induced experimental periodontitis in rats

Liu Y‐F, Wu L‐A, Wang J, Wen L‐Y, Wang X‐J. Micro‐computerized tomography analysis of alveolar bone loss in ligature‐ and nicotine‐induced experimental periodontitis in rats. J Periodont Res 2010; 45: 714–719. © 2010 John Wiley & Sons A/S Background and Objective: Nicotine reportedly is a risk factor for periodontitis, but accurate data regarding nicotine‐induced alveolar bone loss is lacking. The aim of this study was to quantitatively assess alveolar bone loss in ligature‐ and nicotine‐induced periodontitis in rats using micro‐computerized tomography (micro‐CT). Material and Methods: Thirty‐six adult male rats were treated by placing silk ligatures around the cervixes of the right second maxillary molar; the contralateral tooth was untreated. After ligation, the animals were randomly divided into three groups: group A received intraperitoneal injections of saline solution, group B received 0.83 mg of nicotine/kg/d, and group C received 1.67 mg of nicotine/kg/d. Six animals in each group were killed on days 14 and 28 after ligature placement, and then micro‐CT examinations were conducted. Results: In all groups, bone mineral density (BMD), bone volume fraction (BVF), trabecular number (Tb.N) and trabecular thickness (Tb.Th) values of the ligated sides were significantly lower than those of the unligated sides (p < 0.001), whereas alveolar bone height loss (ABHL) and trabecular separation (Tb.Sp) of the ligated sides were significantly higher than those of the unligated sides (p < 0.001). Compared with the control group, nicotine administration increased the ABHL value and decreased the BMD, BVF and Tb.Th values of both sides in a dose‐dependent manner (p < 0.05). Conclusion: Our results confirmed that ligature could cause significant loss in the trabecula of alveolar bone, and daily administration of nicotine resulted in further bone loss and microstructure deterioration.     

A histologic and histometric assessment of the influence of nicotine on alveolar bone loss in rats

BACKGROUND: Cigarette smoking has long been recognized as a risk factor for periodontal disease. The aim of this study was to perform quantitative and qualitative analyses of bone loss in the furcation region of periodontally healthy rats after daily systemic administration of nicotine or saline solution. METHODS: Thirty adult male Wistar rats were assigned randomly to twice daily subcutaneous injections of saline solution (control, group C) or nicotine (group N). The animals were sacrificed at 37, 44, or 51 days after the first subcutaneous injection. The specimens were processed for serial histologic sections, and the area of bone loss in the furcation region of the second molar was analyzed histometrically. RESULTS: Greater bone loss was detected in group N compared to group C on day 37 (16.36 +/- 5.84 mm(2) and 7.24 +/- 2.66 mm(2)), day 44 (15.12 +/- 4.57 mm(2) and 7.76 +/- 1.35 mm(2)), and day 51 (18.80 +/- 3.71 mm(2) and 8.74 +/- 2.61 mm(2)), respectively (P <0.05). Extension of bone loss appeared greater in the furcation region of group N where a thinner trabeculae bone was found. After day 37, bone loss did not increase significantly. CONCLUSIONS: Daily systemic administration of nicotine resulted in significantly greater bone loss in the furcation region compared to saline solution. This indicated a close association between nicotine and periodontal morbidity in rats.     

Buccal alveolar exostoses: prevalence, characteristics, and evidence for buttressing bone formation

BACKGROUND: Buttressing bone formation has been described as the development of thickened or exostotic buccal alveolar bone in response to heavy occlusal forces. Little supporting evidence for this model has been found in previous literature, however, and there is little seen on the prevalence or characteristics of buccal alveolar exostoses. METHODS: A sample of 416 selected teeth and investing bone in 52 modern skeletal specimens at the National Museum of Natural History were examined. Two measures of heavy occlusal function--periodontal ligament (PDL) width and occlusal attrition--were analyzed for their relationship to three parameters of buccal alveolar bone (exostoses, lipping, and overall thickness). RESULTS: Buccal alveolar bone enlargements were found in 25% of all teeth examined: 18% were expressed as marginal bony lippings and 7% as buccal exostoses. Exostoses were mainly seen around maxillary molars and bicuspids, especially in males, while lippings were seen in molars, bicuspids, and mandibular incisors, with even gender distribution. When findings were controlled for arch and tooth type, no significant correlations were found between wider PDL spaces or occlusal attrition and exostotic, lipped, or thicker alveolar bone. CONCLUSIONS: These results indicate a lack of anatomic evidence for the theory of buttressing bone formation and suggest that other factors may be of greater importance in the etiology of buccal bone enlargements. Incidentally, no correlation was found between widened PDL spaces or severe occlusal attrition and the presence of cervical loss of tooth structure, which casts doubt on the currently popular concept of abfraction.     

The effect of dexamethasone in the pathogenesis of ligature-induced periodontal disease in Wistar rats

The aim of this study was to evaluate, in rats, the role of the systemic use of dexamethasone in the pathogenesis of induced alveolar bone loss. In 26 female Wistar rats, ligatures were placed around the second upper molars, and the contralateral ones served as intra-group controls. Two groups were formed. The test group received 0.5 mg/kg of dexamethasone subcutaneously every third day during thirty days. The control group received the same amount of saline solution. After thirty days, the animals were sacrificed and their maxillae were removed. Sodium hypochlorite was used to prepare the specimens, and the cementum-enamel junction was stained with 1% methylene blue. Morphometric analysis of the alveolar bone loss was performed with standardized digital photographs, and the distance between the cementum-enamel junction and the alveolar bone crest was measured with the software ImageTool 3.0. Intra-examiner calibration revealed a Pearson correlation coefficient of 0.99. Statistical analysis was performed by paired or independent samplet tests, as appropriate (alpha = 0.05). Dexamethasone increased the mean alveolar bone loss in ligature-induced periodontitis in relation to the control group (0.77 and 0.61 buccally, and 0.65 and 0.56 palatally, respectively). No significant differences were observed intergroups in the teeth without ligatures. In the animal model used here, the use of dexamethasone increased the progression of ligature-induced alveolar bone loss.     

Assessment of the resistance to fracture of endodontically treated molars restored with amalgam

STATEMENT OF PROBLEM: Controversy exists concerning the preferred type of final restoration of endodontically treated molars regarding their resistance to fracture under occlusal load. PURPOSE: The aim of this study was to assess the resistance to fracture of endodontically treated molars with various degrees of tooth structure loss restored with amalgam under simulated occlusal load. MATERIAL AND METHODS: .The study teeth consisted of 90 noncarious, nonrestored molars stored in physiological saline solution. The teeth were endodontically treated and randomly divided into 9 experimental groups of 10 specimens each with various degrees of tooth loss, ranging from a conservative endodontic access to removal of all cusps. All teeth were restored with a standardized technique to their original contour with amalgam. Each specimen was mounted onto a specialized jig for loading at the central fossa at a 30-degree angle to the long tooth axis. The resistance to fracture, under continuous compressive force at a cross-head speed of 2 mm/minute, was applied by a universal testing machine and was recorded. One-way analysis of variance with Scheffé contrast was used to statistically compare the differences between the groups at significance level P<.05. RESULTS: One-way analysis of variance showed that the group with a conservative endodontic access (1137.6 +/- 311.6 N) and the group with removal of all cusps (1261.4 +/- 195.1 N) presented a significantly higher resistance to fracture when compared with the other groups (P<.05). There was no significant difference in resistance to fracture under the simulated load between the other 7 groups, which ranged from 655.8 +/- 229.4 to 906.3 +/- 168.1 N (P>.05). CONCLUSION: Within the limitations of this study, the endodontically treated molars with a conservative endodontic access or after removal of all cusps that were restored to their original contour with amalgam presented the highest resistance to fracture under a simulated occlusal load.     

Effect of body weight in the pathogenesis of ligature-induced periodontal disease in Wistar rats

Objective. The aim of this study was to compare ligature-induced alveolar bone loss between obese and non-obese rats. Material and methods. Thirty female Wistar rats were randomly divided into two groups: a test group comprising 14 rats fed with a “cafeteria diet” for 120 days in order to gain weight and a control group comprising 16 regularly fed rats. Ligatures were placed around the 2nd upper molars, and the contralateral teeth served as intra-group controls. After 30 days, the animals were killed and the maxillae were removed. Sodium hypochlorite was used to prepare the specimens, and the cementum-enamel junction was stained with methylene blue 1%. Morphometric analysis of alveolar bone loss was by standardized digital photographs and the distance between the cementum-enamel junction and the alveolar bone crest was measured using the software Image Tool 3.0. Results. Body weight differed statistically between test and controls (268.6 and 242.4 g, respectively). Test animals demonstrated a mean (SD) alveolar bone loss of 0.51 (0.11) mm and in the controls 0.52 (0.14) mm in teeth with ligatures. No statistically significant differences were observed (ANOVA+Tukey), except for teeth with and without ligatures in both groups. Conclusions. The establishment and progression of alveolar bone loss in rats was not influenced by body weight in the present study.     

神经生长因子及酪氨酸蛋白激酶受体AmRNA在创伤咬合犬牙周组织中的表达

目的研究咬合创伤时犬牙周组织中神经生长因子(nerve growthfactor,NGF)及其酪氨酸蛋白激酶受体A(tyrosine ki-nase A,trkA)mRNA表达水平的变化,探讨咬合创伤致口面痛的可能机制。方法高出咬合面1.5mm的镍铬合金嵌体黏固于18只杂种犬右侧上颌第一、二磨牙咬合面的I类洞形内,造成对牙合牙的创伤。黏固嵌体后3、7、14、30、60d时拔除双侧上下颌磨牙并立即刮取牙周膜组织。用逆转录(RT)-PCR检测牙周膜组织中NGF及trkAmRNAs表达水平并与无咬合创伤的对照组作比较。结果①咬合创伤3d起,创伤侧牙周组织内NGF mRNA急剧升高,14~30d时表达水平最高,30d时NGF mRNA是对照侧及对照组的3.0倍,60d时表达量下降。3~7d对照侧牙周组织NGF mRNA也上调(P<0.05)。②trkAmRNA表达水平的变化规律同NGF mRNA,trkA mRNA在30d时表达水平最高。③观测时间内,创伤侧NGF和trkA mRNAs的表达水平高于对侧(P<0.01),分别从咬合创伤3d和7d起高于对照组(P<0.05)。结论咬合创伤能导致牙周膜内NGF及trkAmRNA表达水平上调。单侧咬合创伤能导致双侧牙周组织NGF、trkA mRNA表达水平的改变。     

Overeruption of periodontally affected unopposed molars in adult rats

Fujita T, Montet X, Tanne K, Kiliaridis S. Overeruption of periodontally affected unopposed molars in adult rats. J Periodont Res 2009; doi: 10.1111/j.1600‐0765.2009.01230.x © 2009 John Wiley & Sons A/S Background and Objective: In clinical practice, anterior teeth with periodontal disease exhibiting signs of overeruption are occasionally encountered. However, the influence of periodontitis on unopposed teeth needs to be further elucidated. This study investigated, in rats, the overeruption pattern of unopposed mandibular molars with experimentally induced periodontitis. Material and Methods: Sixty adult male rats were divided equally into four groups. In two groups, periodontitis was induced by a silk thread placed around the cervix of the right mandibular molar. In two groups with and without experimentally induced periodontitis, the crowns of the right maxillary molars were reduced occlusally by grinding to simulate unopposed teeth. After 4 wk, the animals were killed and scanned using micro‐computed tomography to measure the vertical position of molars and the buccal and lingual alveolar bone levels. Results: There were no significant differences in the overeruption of opposed molars with and without periodontitis. However, the alveolar bone level of opposed molars with periodontitis was lower than that of healthy molars. Healthy unopposed molars were extruded when compared to molars with an antagonist. The alveolar bone level of healthy unopposed molars was not influenced by molar overeruption. Unopposed molars with periodontitis exhibited significantly larger extrusion than healthy unopposed molars. The lingual alveolar bone level of unopposed molars with periodontitis was lower than that of other healthy and periodontally affected teeth. Conclusion: The loss of antagonist causes overeruption of the unopposed tooth, which becomes more prominent in the presence of periodontitis.     

Morphological study of periodontal tissues in the initial stage of periodontal disease. Part 1. Application of a morphological measurement and a system for evaluating the periodontal status

The functional aberration of occlusion, based on the morphology of the alveolar process, causes chronic irritation of the periodontium in addition to the concomitant effect of other local environment factors. This investigation was designed to study the role of morphological characteristics in the periodontal disease process. The periodontal health of 22 subjects was recorded by clinical and roentgenological measurements of the loss of periodontal tissue. The criteria for this selection were no loss of or a crowding of adjoining teeth and no disharmony in occlusal contact. Morphological data were measured around the premolars and molars of lower jaws on the study models individuals, in bucco-lingual width of the alveolar bone in relationship to the width of the crown and the sagittal figure of the Spee curve etc. by using a three-dimensional analyzer. The subjects were categorized as Type II when the records indicated a ratio of the crown width/bone width of 1/1.2. Types I and III, depended on a greater and smaller ratio, respectively. Type W symbolized the alveolar process, of which the interproximal bone showed a considerable curvature mediodistally. Type F showed a flat pattern. The sagittal figure of the Spee curve was divided into four patterns: Pattern A or B, when the cusp of the canine and first premolar leveled over or on the occlusal plane; Pattern C, when the cusp of the canine leveled over and the first premolar under the occlusal plane, and Pattern D, when all cusps, canine, premolar and molar, were under the occlusal plane. The distance from the occlusal plane to the deepest point of the Spee curve was divided into four groups: Pattern a, when the distance was 0-1.0 mm, Pattern b, 1.1-2.0 mm, Pattern c, 2.1-3.0 mm and Pattern d, 3.1-4.0 mm. These results suggest that the morphological evaluation is a useful diagnostic indicators on a rational basis. The morphological characteristics might be related to the presence of periodontal disease and allowed to speculate the pathological changes in established stage, and also to the response to periodontal treatment in the initial stage of periodontal disease.     

Ankylosis of primary molars--a future periodontal threat to the first permanent molars?

Most infra-occluded and ankylosed primary molars with a permanent successor will exfoliate normally. Continuous supervision of occlusal development and radiographic control of normal root resorption have been recommended. The decreased height of the alveolar bone level at the site of the infra-occluded primary molar has been reported to normalize after the eruption of the permanent successor. However, opinions that infra-occlusion of primary molars entails a risk of future periodontal damage to the first permanent molars have been presented. The aim of this study was to perform a long-term follow-up of the alveolar bone level mesial to the first permanent molars after spontaneous exfoliation or necessary extraction of the infra-occluded second primary molars. The material consisted of 143 permanent molars adjacent to 119 infra-occluded primary molars and 24 normal contralateral primary molars in 68 individuals. The subjects were re-examined about 8 years after the exfoliation or extraction of the infra-occluded second primary molars. The subjects were examined both clinically and radiographically. Alveolar bone level mesial to the first permanent molars was measured in bite-wing radiographs. All but two permanent first molars showed a normal alveolar bone level mesially. In two first permanent molars where the primary molar was extracted, mesial approximal bone loss amounted to 4 and 3 mm, respectively, but no pocket formation was found. Infra-occlusion and ankylosis of primary molars does not constitute a general risk of future alveolar bone loss mesial to the first permanent molars. The general treatment recommendation to await normal exfoliation and eruption of successors remains valid.     

Changes in the microstructure of the rat alveolar bone induced by unilateral molar extraction and estrogen deficiency

The present study was designed to assess compensatory changes in the microstructure of alveolar bone induced by occlusal force and estrogen deficiency using micro-computed tomography, which enables us to analyse bone mass and architecture in detail, in combination with a histomorphometric analysis.Fifteen 10-week-old female Wistar rats were used. We created hypofunctional teeth in the right molar region of the mandible after abolishing occlusal force by extracting the right maxillary molars and bilateral ovariectomy was undergone. Analyses of the microstructure and bone resorption of the alveolar bone were carried out by the micro-computed tomography (micro-CT) and histomorphometric analyses.The results of micro-CT and histomorphometric analyses showed that a decrease in occlusal force stimulated bone resorption and accelerated the fragility of the bone structure in the alveolar bone around the teeth, and also shortened the mean intercept length of the trabecular bone in the direction of the tooth axis. However, estrogen deficiency appeared to have few effects, based on the results of micro-CT and histological morphometric analyses.These results suggest that occlusal force is essential for female rats with sexual maturation during short time period to maintain the structure and regulation of alveolar bone in rats.     

Can nonstandardized bitewing radiographs be used to assess the presence of alveolar bone loss in epidemiologic studies?

OBJECTIVE: To compare periodontitis-associated alveolar bone loss assessment by standardized and nonstandardized radiographs in clinical and epidemiologic studies. METHODS: Participants included 37 patients aged 21-66 years with prior nonstandardized bitewing radiographs scheduled to receive bitewing radiographs as part of their next routine dental care visit. Standardized bitewing radiographs were taken with a Rinn film holder to position the film in the mouth and align the X-rays so that they were at 90 degrees to the film. Before taking the radiograph the bite was registered in centric relation using a polyether impression material. One registered dental hygienist took and processed all the standardized radiographs. One dentist read all radiographs using a viewing box, magnifying lens, and periodontal probe with William's markings. Radiographic bone loss was measured to the closest millimeter at mesial and distal sites of the posterior teeth excluding third molars. The examining dentist was blinded to the participant's name, age, gender, or if the radiograph was standardized or nonstandardized. RESULTS: Mean bone loss (+/- SD) was similar in the standardized and nonstandardized groups (1.60 +/- 0.72 mm versus 1.64 +/- 0.85 mm), and the correlation was high (r = 0.95). Periodontitis was defined as present if the participant had at least one site with 3, 4 and 5 mm bone loss. The Kappa statistics for concordance using these three cutoffs were good and ranged from 0.60 to 0.65. The sensitivity ranged from 72.7 to 80.8% and specificity from 88.5 to 90.9%. CONCLUSIONS: Periodontitis assessed as mean alveolar bone loss or the prevalence of disease based on alveolar bone loss can be accurately and reliably evaluated from nonstandardized radiographs.     

Stress may enhance nicotine effects on periodontal tissues. An in vivo study in rats

OBJECTIVES AND BACKGROUND: Diabetes mellitus and smoking have been described as important risk factors that may affect the initiation and progression of periodontitis. Recent studies have pointed to potentially periodontal risk indicators, which include stress. The present study investigated the effects of stress associated with nicotine administration on periodontal breakdown resulting from ligature-induced periodontitis in rats. METHODS: Twenty adult male Wistar rats were used. After anesthesia, both mandibular first molars received a cotton ligature in the dento-gingival area. The animals were randomly assigned to one of the following experimental groups: A - saline solution, B - 0.73 mg of nicotine/kg/d (intraperitoneal), C - stress (immobilization - 2 h/d/40 d) associated with an intraperitoneal administration of saline solution, and D - stress (immobilization - 2 h/d/40 d) associated with an intraperitoneal injection of 0.73 mg of nicotine/kg/d. Forty days later, the animals were sacrificed and the specimens routinely processed for serial decalcified sections. RESULTS: Intergroup analysis (ANOVA) revealed a greater bone loss (P < 0.05) in the animals of group D compared with the animals from groups A, B and C. In addition, the data revealed a significant effect of nicotine (group B) compared with groups A and C (P < 0.05), and no difference between groups A and C (P > 0.05). CONCLUSION: Within the limits of the present study, although stress did not affect periodontitis by itself, it significantly enhanced the effects of nicotine on the periodontal tissues.     

Maxillary sinus pneumatization following extractions: a radiographic study

PURPOSE: The aim of this study was to identify and measure postextraction maxillary sinus pneumatization using fixed reference lines on panoramic radiographs. MATERIALS AND METHODS: One hundred fifty-two panoramic radiographs, each of a different subject, were used to measure superoinferior differences of the sinus floor position in dentate sites in comparison with contralateral edentulous sites. Fifty-eight pairs of panoramic radiographs, each pair of the same subject, were used to measure superoinferior differences of the sinus floor position in the same site before and 6 to 67 months after extraction. All measurements were performed using an interorbital line and 2 zygomatic process lines as reference lines. Statistical correlations between the amount of expansion of the sinus and the root classification, projection length, duration after extraction, type, and number of the extracted teeth were examined. RESULTS: Postextraction expansion of the sinus in an inferior direction occurred in both comparisons (2.18 +/- 2.89 mm for dentate versus contralateral sites and 1.83 +/- 2.46 mm for the same site pre- and postextraction). A considerable amount of expansion occurred after the extraction of teeth surrounded by a superiorly curving sinus floor (5.27 +/- 1.59 mm). A larger expansion was also measured after second molar extractions in comparison to first molars and in cases of extractions of 2 or more adjacent posterior teeth. DISCUSSION: Posterior maxillary tooth extraction caused an inferior expansion of the maxillary sinus in relation to fixed anatomic landmarks, thus proving the pneumatization phenomenon after tooth loss. CONCLUSIONS: Sinus pneumatization was identified after extraction of maxillary posterior teeth. The expansion of the sinus was larger following extraction of teeth enveloped by a superiorly curving sinus floor, extraction of several adjacent posterior teeth, and extraction of second molars (in comparison with first molars). If dental implant placement is planned in these cases, immediate implantation and/or immediate bone grafting should be considered to assist in preserving the 3-dimensional bony architecture of the sinus floor at the extraction site.     

Treatment of removable partial dentures. 2. Causes and consequences of a reduced occlusal system

The occlusal system is part of the orofacial system and consists of the maxillary and mandibular alveolar ridge and teeth which are occluding or not or the removable denture teeth. The most prevalent causes of loss of teeth are insufficient oral self care or inadequate professional oral healthcare service. A reduced dentition can be described in terms of diastemas in the anterior region and number of occluding pairs of (pre)molars, differentiated as interrupted or shortened dental arches. Characteristic of a healthy functional occlusal system are the absence of pathology and the possibility to practice all oral functions without inconvenience. The consequences of a reduced occlusal system may be overload and/or migration of teeth, mandibular instability, and impaired esthetics and chewing function. Morphological and functional alterations can be considered to be adaptations to changed situations or to be pathological. The distinction between adaptation and pathology cannot be sharply defined. If prosthetic replacement of teeth is needed, the trend is to avoid removable partial dentures.