Tooth mobility after periodontal surgery.

Changes in tooth mobility after surgical crown lengthening procedures were examined with a modern electro-mechanical instrument (Periotest) in a total of 37 teeth in 14 patients between the ages of 18 and 55 years. Seven teeth were incisors, three canines, thirteen pre-molars and fourteen were molars. Periotest values, probing depths, bleeding indices and plaque indices were recorded after the initial preparation stage of the periodontal treatment, and further Periotest values and plaque and bleeding indices were recorded at intervals up to 3 months after surgery. In each category of teeth there was a progressive increase in tooth mobility starting immediately after surgery and peaking about the seventh day. The mobility then declined steadily to approach the base line again at about 3 months. There were statistically significant differences in mobility after surgery between tooth types (p < 0.01). Gender and age did not significantly affect the values. The pattern of post-surgical tooth mobility can be closely correlated with the known biological events of post-surgical healing.     

Splints made of wire and composite: an investigation of lateral tooth mobility in vivo

Abstract In 103 posttraumatic splints, lateral tooth mobility was measured with Periotest immediately before and after the routine splint removal. The splints were made of composite resin and an 0.017×0.025″ orthodontic steel wire. 481 teeth were measured. A statistic evaluation revealed that the immobilisation effect did not exceed normal tooth firmness. Fixation to one neighbouring tooth had less effect than fixation to two. Adjacent tooth gaps reduced the effect. Splint extensions had no influence. With the use of the Periotest device, more than 50% of all teeth with a true mobility of 20 Periotest-units or more were detectable as mobile in spite of the fixed splint.     

Long-term follow-up of maxillary incisors with severe apical root resorption

The purpose of the study was to analyse the mobility of teeth with severe orthodontically induced root resorption, at follow-up several years after active treatment, and to evaluate mobility in relation to root length and alveolar bone support. Seventy-three maxillary incisors were examined in 20 patients, 10-15 years after active treatment in 13 patients (age 24-32 years) and 5-10 years after active treatment in seven patients (age 20-25 years). All had worn fixed or removable retainers; seven still had bonded twistflex retainers. Total root length and intra-alveolar root length were measured on intra-oral radiographs. Tooth mobility was assessed clinically according to Miller's Index (0-4) and the Periotest method. Crestal alveolar bone level, periodontal pocket depth, gingival, and plaque indices, occlusal contacts during occlusion and function, and dental wear were recorded. There was a significant correlation (P < 0.05) between tooth mobility, and total root length and intra-alveolar root length. No correlation was found between tooth mobility and retention with twistflex retainers. None of the variables for assessment of periodontal status, occlusion and function were related to total root length or tooth mobility. It is concluded that there is a risk of tooth mobility in a maxillary incisor that undergoes severe root resorption during orthodontic treatment, if the remaining total root length is < or = 9 mm. The risk is less if the remaining root length is > 9 mm. Follow-up of teeth with severe orthodontically induced root resorption is indicated.     

A split-mouth study on periodontal and microbial parameters in children with complete unilateral cleft lip and palate

BACKGROUND: Complete unilateral cleft lip and palate (UCLP) is a hereditary or multifactorial malformation that can be corrected successfully with a combined orthodontic, surgical and restorative treatment. Such multidisciplinary treatment takes many years and demands a lot of attention to both patients' teeth and periodontium. OBJECTIVES: This split-mouth study aimed to compare the periodontal health as well as the microbial parameters between cleft and non-cleft region. MATERIAL AND METHODS: 75 patients (52 males, 23 females) between 8 and 20 years with a complete unilateral cleft lip and palate (before (n = 30), during (n = 34) and after (n = 11) the active orthodontic treatment) volunteered for this study. Four regions were defined for the split-mouth comparison: teeth neighbouring cleft (site 1), tooth in cleft (site 2), and the corresponding contra-lateral teeth, respectively, in the unaffected quadrants (sites 3 and 4). At all sites the following periodontal parameters were recorded: plaque and gingivitis indices, pocket depth, attachment loss, bleeding on probing, tooth mobility (visual and Periotest), radiographic bone loss and gingival width. In addition, three pooled subgingival plaque samples were taken (around tooth in cleft, teeth facing the cleft, and contra-lateral teeth of the latter). RESULTS: The differences between the teeth neighbouring the cleft and the corresponding contra-lateral opponents were of borderline significance (P 相似文献   

Clinical evaluation of abutment teeth of removable partial denture by means of the Periotest method

Prosthodontics should be one of the means of establishing conditions for the maintenance of periodontal health. The forces applied to the abutment teeth and their effects are very important considerations in the design and construction of the removable partial dentures. This 6-month follow-up clinical study evaluated the degree of mobility of abutment teeth of distal extension and tooth supported removable partial dentures by using Periotest. Two types of clasp design were selected for evaluation. In cases with unilateral and bilateral distal-extension, a clasp design including a T clasp of Roach retentive arm, a rigid reciprocal arm and a mesial rest were used. For the abutments of tooth-supported removable partial dentures, a second clasp design with a cast circumferential buccal retentive arm, a rigid reciprocal clasp arm and a rest adjacent to the edentulous ridges was selected. A total of 68 abutment teeth was analysed. Periotest values were made at the time of denture placement (control) and at 1, 3 and 6 months after the denture placement. The statistical analysis was performed using Friedman test. All analysis was performed at a 0.05 level of significance. The results revelled that no significant changes in tooth mobility were observed during the 6-months follow-up (P > 0.05). In conclusion, our findings suggest that adequate oral hygiene instructions, careful prosthetic treatment planning and regular recall appointments play an important role in preventing changes in abutment tooth mobility caused by removable partial denture placement.     

61例正畸牙根牵引前后牙周状况变化的研究

目的观察61例正畸牙根牵引治疗前后牙周状况的变化。方法选择前牙32例、前磨牙29例的残根,共366个位点,使用正畸方法牵引牙根,记录正畸牵引治疗前、正畸加力2周、正畸结束前、修复完成后即刻、修复3个月后的各个阶段残根的牙齿松动度、牙周探诊深度(periodontal depth,PD)和牙龈出血指数(bleeding index,BI),并统计学比较各个时期临床指标的差异。结果①牙齿松动度在正畸牵引加力2周后及正畸牵引结束前分别增至1.50及1.14,与正畸牵引治疗前差异有统计学意义(P<0.05);修复完成后即刻,牙齿松动度与正畸牵引治疗前差异没有统计学意义。②PD在正畸牵引治疗结束前减至2.34 mm、修复完成后即刻降至2.57 mm,均优于治疗前,与正畸牵引治疗前有统计学意义(P<0.05);修复3个月后,PD值与正畸牵引治疗前差异没有统计学意义。③BI在正畸牵引加力2周后增至2.18,修复3个月后又降至1.05,与治疗前差异有统计学意义(P<0.05)。结论正畸牙根牵引治疗过程中牙周状况会发生一时性的改变,但是没有对牵引后的牙周组织造成永久的损伤。     

Stability of implants and natural teeth as determined by the Periotest over 60 months of function

Various methods for evaluating tooth mobility have been developed throughout the years, but their acceptance has been limited because of the subjectivity associated with their use. In recent years, the Periotest has been studied and used to evaluate the mobility of natural teeth and is claimed to b e potentially reliable in assessing the stability of the implant-bone interface. Few clinical implant studies have used natural teeth as controls to monitor changes in mobility associated with dental implants. The Dental Implant Clinical Research Group initiated a long-term clinical study in 1991 to assess the influence of design, application, and site of placement on clinical success and crestal bone height. As part of the study, Periotest values (PTVs) were recorded for 2,623 of the 2,998 implants placed and uncovered. For the statistical analysis, 2,623 implants were tested at second-stage surgery, with the number of implants tested varying at each follow-up visit. Data were collected from investigators at 32 study centers for periods ranging up to 60 months. A total of 975 natural teeth from 409 partially edentulous study subjects served as controls. FPVs on natural teeth and implants were combined, and the overall average Periotest values (OA-PTVs) were compared with values for individual subjects. The effect of implant and natural tooth locations on mobility were evaluated and compared with each other. The combined OA-PTV for all natural teeth was +1.8 and the OA-PTV for all implants was -3.4 PTVs. Compared with those in the maxillae, mandibular teeth and implants were found to be more stable Implants were found to be significantly more stable as compared with natural teeth. The recorded variations in PTVs for natural teeth and implants over the entire evaluation period were not found to be significantly different. This study developed the following conclusions: (1) implants were found to be significantly less mobile as compared with natural teeth for individual subjects; (2) the PTVs for natural teeth and implants did not exhibit significant variation over the evaluation period; (3) the Periotest can provide reproducible assessment of stability in a long-term clinical study; and (4) changes in PTVs may be helpful in evaluating improvement or degradation of the implant-bone complex.     

Forced orthodontic extrusion to restore extensively damaged anterior and premolar teeth as abutments for single-crown restorations: Up to 5-year results from a pilot clinical study

Statement of problemClinical data on orthodontic extrusion to restore teeth deemed unrestorable because of their defect size are scarce. It remains unclear for which defects forced orthodontic extrusion and tooth retention is preferred to extraction.PurposeThe purpose of this pilot clinical study was to investigate the survival, frequency, and type of complications of extensively damaged teeth requiring single-crown restorations after forced orthodontic extrusion.Material and methodsParticipants were recruited from consecutive patients in need of restorative treatment of extensively damaged teeth at a university clinic. The teeth were orthodontically extruded to reestablish the biologic width and to ensure a 2-mm ferrule preparation before restoration. The primary endpoint was restoration success and survival. At recall, survival was defined as the tooth being in situ and success as a symptom-free tooth with an intact, caries-free restoration and with physiological pocket probing depths, no signs of intrusion, ankylosis, root resorption, or periapical radiolucency. Recalls were performed every 6 months; the outcome was assessed by radiographic and clinical evaluation after up to 5 years of clinical service. Quantitative parameters were described with mean values and standard deviations.ResultsThirty-four participants were assessed for eligibility and enrolled (mean ±standard deviation age: 53.4 ±18.9 years). Four participants were premature dropouts. Data were analyzed for 35 teeth in 30 participants. The amount of extrusion varied between 2 and 6 mm (mean ±standard deviation 3.4 ±0.9 mm). The mean duration of extrusion was 18.9 ±12.6 days and the mean duration of retention was 126.94 ±88.1 days. The mean ±standard deviation crown-to-root ratio after treatment was 0.8 ±0.1 (range: 0.5 to 1.0). Three participants exhibited orthodontic relapse before restoration. Teeth were successfully restored after repeated extrusion. After a mean observation period of 3.3 years (range: 1 to 5.2 years), 29 of 31 teeth were still in situ. Two teeth were fractured, and 4 participants were not available for recall. Thus, the survival rate was 94%. No resorption or periapical translucencies were observed radiographically. Clinical examinations revealed physiological probing depths and absence of ankyloses. One tooth presented with marginal bone loss. The most frequent type of complication was orthodontic relapse at recall (n=3). A total of 84% of teeth were considered a success.ConclusionsForced orthodontic extrusion allowed for the restoration of anterior and premolar teeth deemed as nonrestorable because of their defect size. Tooth retention of extensively damaged teeth and their use as abutments for single-crown restorations can be recommended.     

Apical root resorption of upper incisors during the torquing stage of the tip-edge technique

The purpose of this study was to investigate whether treatment with the Tip-Edge appliance resulted in more apical root resorption (ARR) of the central and lateral incisors during the torquing (third stage) than the non-torquing phases (first two stages) of orthodontic treatment. The three stages of this orthodontic technique make it possible to examine the amount of root shortening during torque separately from other types of tooth movement. The ARR ratio was calculated in 31 Caucasian patients (20 females, 11 males), after the non-torquing stage of treatment and after the torquing phase, by analysing periapical radiographs taken at the beginning of treatment (T1), before the start of the torquing stage (T2), and at the end of treatment (T3). At T1, the mean age was 13 years 6 months (+/- 3 years 3 months). The mean, standard deviation and range of the ARR ratios were calculated and compared (P < 0.001). T-tests were performed to determine levels of significance, at different stages of treatment, between teeth with and without ARR (ARR ratio = 1). Root shortening at T3 was observed for 70 per cent of the central and 76 per cent of the lateral incisors. At T2, ARR was 48 and 53 per cent, respectively. Compared with T2, 38 per cent of the central incisors and 55 per cent of the lateral incisors showed ARR during the application of torque. At T3, the finding for both was 22 per cent. The mean ARR ratio for the central and lateral incisors was the same after the non-torquing stage of treatment but was significantly different from a tooth with no root resorption. After the torquing stage, the ARR ratio for the central incisors was 0.96 and for lateral incisors 0.92. At the end of treatment, the ratio was 0.89 and 0.85, respectively. This study revealed that both the central and the lateral incisors showed comparable amounts of ARR during the torquing and non-torquing stage of Tip-Edge treatment.     

In vitro splint rigidity evaluation – comparison of a dynamic and a static measuring method

Abstract – Objectives: The aim of this in vitro study was to investigate a dynamic and static tooth mobility assessment method in terms of reproducibility and correlation. Materials and Methods: A custom‐made artificial model was used. The central incisors simulated ‘injured’ teeth with increased mobility, and the lateral incisors served as ‘uninjured’ teeth with physiological mobility. To assess tooth mobility, three consecutively repeated measurements were taken, in the vertical and horizontal dimensions before and after splinting, using the Periotest method as well as the Zwick universal testing machine. Reproducibility of the measurements was tested using anova and the Bonferroni post hoc test (α = 0.05). Correlation was analysed using Spearman’s rank correlation (α = 0.05). Results: No significant differences were found when comparing the three consecutively taken Periotest values and the vertical Zwick values (P > 0.05). In the horizontal dimension, the first Zwick values differed from the second and third values (P < 0.05). Only a few random correlations (P < 0.05) were found when comparing the two assessment methods. Horizontal and vertical measurements within one method did not correlate (P > 0.05). Conclusions: The Periotest and vertical Zwick values are highly reproducible. The measurements of the two methods do not correlate; therefore, a conversion of Periotest values into metric displacement data is not feasible. The two methods provide different valuable information about tooth mobility. The Periotest method describes the damping characteristics of the periodontal ligament while the Zwick method reveals quantitative metric values.     

Comparison of Incisor Mobility after Insertion of Canine-to-Canine Lingual Retainers Bonded to Two or to Six Teeth A Clinical Study

BACKGROUND: Fixed appliance therapy often extends over several years. Debonding is warmly welcomed and is often seen by the patient as the end of treatment. Yet both patients and parents often underestimate the importance of the subsequent retention period and the speed at which negligence in this treatment phase results in relapse. Bonded retainers guarantee excellent long-term stability at least while they are in situ. The reliable attachment of lingual retainers with modern bonding techniques has led to widespread application of this retention method. The present study investigated its influence on tooth mobility and on the damping properties of the periodontal tissue, by means of a dynamic measuring method (Periotest). PATIENTS AND METHOD: For this purpose two groups with mandibular bonded retainers and one control group were formed. The control group wore removable retention appliances. In all groups, active treatment with fixed appliances had been completed at least half a year before baseline. RESULTS: The results showed that bonded retainers had a negative impact on the damping properties of the periodontal tissue and thus in the broader sense on tooth mobility. Tooth mobility decreased with the number of teeth to which the retainer was bonded but remained, as in the control group, within the physiologic range.     

Composition changes in gingival crevicular fluid during orthodontic tooth movement: comparisons between tension and compression sides

The aim of this study was to evaluate whether the application of tension or compression forces exerted on the periodontium during the early phase of orthodontic tooth movement is reflected by differences in the composition of the gingival crevicular fluid (GCF), at the level of interleukin-1beta (IL-1beta), substance P (SP), and prostaglandin E(2) (PGE(2)). Eighteen children (mean age 10.8 yr) starting orthodontic treatment were included in the study. Molar elastic separators were inserted mesially to two first upper or lower molars. One of the antagonist molars served as the control. GCF was collected from the mesial and distal sites of each molar, before (-7 d, 0 d) and immediately after (1 min, 1 h, 1 d, and 7 d) the placement of separators. The levels of IL-1beta, SP, and PGE(2) were determined by enzme-linked immunosorbent assay. At the orthodontically moved teeth, the GCF levels of IL-1beta, SP, and PGE(2) were significantly higher than at the control teeth in both tension and compression sides, and at almost all occasions after insertion of separators. The increase, relative to baseline values, was generally higher in tension sides. For the control teeth, the three mediators remained at baseline levels throughout the experiment. The results suggest that IL-1beta, SP, and PGE(2) levels in the GCF reflect the biologic activity in the periodontium during orthodontic tooth movement.     

微创牵引复位外伤挫入年轻恒牙的临床疗效观察

目的研究微创正畸牵引复位无自发萌出能力的外伤挫入年轻恒牙的临床疗效。 方法选择年轻恒牙外伤挫入的患者8例,年龄7~ 11岁,共11颗上颌切牙,其中9颗重度挫入、2颗中度挫入。观察1个月以上,确定无自发萌出能力后,采用如下微创正畸牵引方式复位：（1）"2 × 4"镍钛弓丝技术：单颗牙中度挫入,邻牙萌出3/4以上;（2）活动基托牵引：重度根向挫入、邻牙萌出不足1/2或伴脱位性损伤;（3）活动基托牵引联合"2 × 4"镍钛弓丝技术：重度唇向或腭向挫入,邻牙萌出不足1/2或伴脱位性损伤。观察治疗后患牙萌出状况、牙根吸收、边缘骨缺损和（或）牙髓变化情况。 结果（1）患牙萌出状况：所有挫入牙均复位;（2）牙根吸收情况：4颗牙出现轻微根吸收,2颗牙牵引前出现根尖部和根中段侧方低密度影,治疗完成时低密度影消退,余牙均无牙根吸收;（3）边缘骨缺损情况：除2颗牙外均无边缘骨缺损;（4）牙髓活力状况：3颗牙齿发育Nolla 10期的挫入牙,牵引前即行牙髓摘除术,4颗牵引中行牙髓摘除术,4颗牙髓活力正常,其中1颗根管钙化。 结论无萌出潜力的挫入年轻恒牙可根据其挫入方向及邻牙萌出程度和受伤情况,分别选择"2 × 4"镍钛弓丝技术、活动基托牵引技术或活动基托联合"2 × 4"镍钛弓丝牵引技术,及时进行微创牵引,可有效复位挫入牙,避免牙根吸收,减少边缘骨缺损,并可能保存活髓,值得进一步推广。     

伴错[牙合]畸形的侵袭性牙周炎患者牙周-正畸联合治疗长期疗效的影响因素分析

目的分析侵袭性牙周炎(aggressive periodontitis,AgP)患者牙周-正畸联合治疗长期疗效的相关影响因素。方法纳入2002年1月至2010年9月于北京大学口腔医学院·口腔医院牙周科就诊,并完成牙周-正畸治疗的AgP患者25例,收集初诊(T0)、正畸治疗完成后(T1)、正畸结束3年以上末次复查(T2)时的全口根尖X线片,通过根尖X线片评价患者根形态异常情况、正畸前后剩余牙槽骨高度(residual alveolar bone height,RBH)的变化。评价根形态异常对牙周-正畸治疗的影响,并进行多因素分析,评价与正畸后长期牙槽骨高度变化相关的牙和个体水平因素。结果T0、T1时统计25例患者的693颗牙,T2期随访14例患者,共观测368颗牙。牙周-正畸治疗前后,牙槽骨高度变化的主要影响因素为根形态异常(估计值为-2.392)、牙位(上颌牙vs.下颌牙估计值为3.139;前牙vs.后牙估计值为?3.469)和T0期的牙槽骨高度变化(估计值为-0.391)(P<0.05)。根形态异常、下颌牙、前牙以及T0时牙槽骨高度高,都是牙槽骨增加的不利因素。正畸后长期观察,牙槽骨高度变化的主要影响因素为牙位(上颌牙vs.下颌牙估计值为3.735;前牙vs.后牙估计值为-5.318)、T0时探诊深度(估计值为-1.594)和T0时牙槽骨高度(估计值为-0.498)(P<0.05)。下颌牙、前牙、T0时牙槽骨高度增加和T0探诊深度增加,都是正畸后长期牙槽骨增加的不利因素。结论多因素分析显示,正畸治疗结束时,牙槽骨高度变化的主要影响因素为根形态异常、牙位和T0时牙槽骨高度;正畸后3年以上复查,牙槽骨高度变化的主要影响因素为牙位、T0时的探诊深度和T0时牙槽骨高度。     

Occlusal interference during mastication can cause pathological tooth mobility

BACKGROUND AND OBJECTIVE: Despite little evidence regarding the relationship between tooth mobility and nonworking contact, the evaluation of occlusion is performed mainly by the detection of premature and/or nonworking contacts during tapping movements and lateral excursion. The hypothesis of this study is that occlusal contact during mastication is potentially traumatic to periodontal tissue. It clarifies the relationship between chewing patterns and the status of periodontal tissue. MATERIAL AND METHODS: Subjects included 73 adults, 20-29 years of age (39 men and 34 women), with complete sets of teeth and no history of orthodontic treatment or periodontal disease. The closing chewing patterns of each subject were classified into three groups by the Masticatory Deviation Index, which depicts the deviation from the normal chewing patterns within 5 mm from the intercuspal position. Periotest was used to diagnose teeth mobility and the values were compared among the three groups. RESULTS: The present study indicates that the chewing movements which deviated from the normal chewing movements increased the mobility of specific types of teeth. CONCLUSION: The results of this study imply a relationship between chewing movements and tooth mobility and indicate that functional evaluation of occlusion is necessary for the examination of periodontal tissue. Occlusal evaluation with border and tapping movements might be insufficient, and functional occlusal evaluation during chewing movements can be clinically useful for using to evaluate periodontal tissue.     

Periotest for measuring periodontal characteristics–Correlation with periodontal bone loss

The Periotest measures the reaction of the periodontium to a defined percussive force. The percussion is applied to the tooth by an electronically controlled tapping head. Information on structural change is obtained by measurement of both the elastic and viscous characteristics of the periodontium. The latter prevent oscillations of the tooth in the alveolar bone. A value is calculated and is displayed as a "Periotest value". The following research report shows the relation of Periotest values to bone loss. Bone loss was quantitatively determined for 2312 teeth from orthopantomographic radiographs and for 900 teeth exposed to intra-oral films using the standard paralleling technique. A differentiation was made between vertical and horizontal bone loss. Clinical mobility index, pocket depth, gingival recession and papillary hemorrhagic index were also measured. There was a strong association between the Periotest value and bone loss. These results suggest that Periotest evaluation provides an objective indication of the extent of periodontal bone loss.     

Alkaline phosphatase activity in dental pulp of orthodontically treated teeth.

INTRODUCTION: The aim of this study was to examine alkaline phosphatase (ALP) activity in the dental pulp of orthodontically treated teeth. METHODS: Sixteen healthy subjects (mean age 17.0 +/-1.6 years) who required extraction of 4 first premolars for orthodontic reasons participated. One maxillary first premolar subjected to orthodontic force was the test tooth. The contralateral first premolar, bracketed but not subjected to mechanical stress, was the control tooth. After a week of treatment, the first premolars were extracted and the dental pulp removed from the teeth. ALP activity was determined spectrophotometrically and the results expressed as units/liter per milligram of pulp tissue [U/(L x mg)]. RESULTS: ALP activity was 89 +/- 26 U/(L x mg) in the test teeth and 142 +/- 33 U/(L x mg) in the control teeth. The difference between the groups was statistically significant (P < .01). CONCLUSIONS: Orthodontic treatment can lead to significant early-phase reduction in ALP activity in human dental pulp tissue.     

正畸治疗前后牙根吸收的临床研究

目的 调查正畸治疗前后牙根吸收的临床特征。方法 随机选择至少经过十二个月固定正畸治疗,有清晰可辨的矫治前后全口曲面断层片的病例９６例,用根吸收分级评估法记录每人矫治前后全口牙齿根吸收情况,并统计分析。结果 （１）正畸治疗前８．６％的牙齿存在根吸收,治疗后４１．６％的牙齿有程度不等的根吸收;（２）治疗前的根吸收绝大部分为轻度,治疗后仍以轻度吸收为主,但也有部分中重度吸收;（３）治疗前的根吸收主要在上颌前牙区;治疗后根吸收上下颌没有显著性差异,但前牙明显高于后牙。结论（１）正畸后的根吸收较为常见;（２）大部分正畸过程中的牙根吸收是可接受的;（３）正畸治疗后有一部分牙齿（１．３％）出现重度根吸收,主要分布于上前牙,成为危害患者颜面美观及功能的隐患,应引起足够的重视。     

High-speed filming of the Periotest measurement

Periodontal disease may be diagnosed with the Periotest technique, which involves electronically controlled and reproducible percussion of tooth. The movement on percussion was investigated with high-speed film and then compared with the return of teeth after static deflection for several seconds as has been reported previously by Lukas and Scholz. The elastic and viscous properties of the periodontium and the surrounding bony tooth socket are to a large extent non-linear. The 10-20 microns deflection of the healthy tooth represents only a fraction of static tooth mobility published by Parfitt or Schulte et al. The visco-elastic properties of a healthy tooth enabling the percussion of the Periotest tapping head to be decelerated in less than 1 ms are largely lost in periodontitis. It is this essential difference which the Periotest method utilizes.