Effectiveness of medical coating materials in decreasing friction between orthodontic brackets and archwires.

OBJECTIVE: The aim of this in vitro study was to evaluate the changes in friction between orthodontic brackets and archwires coated with aluminum oxide (Al2O3), titanium nitride (TiN), or chromium nitride (CrN). In addition, the resistance of the coatings to intraoral conditions was evaluated. METHODS: Stainless steel canine brackets, 0.016-inch round nickel-titanium archwires, and 0.019 × 0.025-inch stainless steel archwires were coated with Al2O3, TiN, and CrN using radio frequency magnetron sputtering. The coated materials were examined using scanning electron microscopy, an X-ray diffractometer, atomic force microscopy, and surface profilometry. In addition, the samples were subjected to thermal cycling and in vitro brushing tests, and the effects of the simulated intraoral conditions on the coating structure were evaluated. RESULTS: Coating of the metal bracket as well as nickel-titanium archwire with Al2O3 reduced the coefficients of friction (CoFs) for the bracket-archwire combination (p < 0.01). When the bracket and stainless steel archwire were coated with Al2O3 and TiN, the CoFs were significantly lower (0.207 and 0.372, respectively) than that recorded when this bracket-archwire combination was left uncoated (0.552; p < 0.01). The friction, thermal, and brushing tests did not deteriorate the overall quality of the Al2O3 coatings; however, some small areas of peeling were evident for the TiN coatings, whereas comparatively larger areas of peeling were observed for the CrN coatings. CONCLUSIONS: Our findings suggest that the CoFs for metal bracket-archwire combinations used in orthodontic treatment can be decreased by coating with Al2O3 and TiN thin films.

The effect of different micro-osteoperforation depths on the rate of orthodontic tooth movement: A single-center, single-blind, randomized clinical trial.

OBJECTIVE: This study aimed to identify the clinical effectiveness of two different penetration depths of micro-osteoperforations (MOPs) on the rate of orthodontic tooth movement. METHODS: Twenty-four patients requiring the removal of the upper first premolar teeth were selected and randomly divided into two groups. The control group participants did not undergo MOPs. Participants in the experimental group underwent three MOPs each at 4-mm (MOP-4) and 7-mm (MOP-7) depths, which were randomly and equally performed to either the left or right side distal to the canine. The retraction amount was measured on three-dimensional digital models on the 28th day of retraction. MOP-related pain was measured using a visual analog scale (VAS). Between-group statistical differences in the VAS scores were determined using an independent t-test and those in canine retraction were determined using analysis of variance and posthoc Tukey test. RESULTS: No significant difference was found between the MOP- 4 (1.22 ± 0.29 mm/month) and MOP-7 (1.29 ± 0.31 mm/month) groups in terms of the canine retraction rate. Moreover, both the groups demonstrated a significantly higher canine movement than the control group (0.88 ± 0.19 mm/ month). MOPs did not significantly affect the mesialization of the posterior teeth (p > 0.05). Moreover, the pain scores in the MOP-4 and MOP-7 groups were similar and showed no statistically significant difference. CONCLUSIONS: Three MOPs with a depth of 4 mm can be performed as an effective method to increase the rate of tooth movement. However, three MOPs with depths of 4-7 mm does not additionally enhance tooth movement.

Buccolingual Inclination Effects of Self-Ligating and Conventional Premolar Brackets: A Cone Beam Computed Tomography Study.

OBJECTIVE: This study aimed to compare the effects of passive self-ligating (PSL) and conventional ligating (CL) of brackets on the buccolingual inclination (BLINC) of the maxillary premolars. METHODS: This in vitro study included a PSL bracket group and a CL bracket group. Acrylic teeth on typodonts were aligned using 0.014-inch heat-activated nickel titanium (HANT) (T1) and 0.019×0.025-inch HANT (T2) and 0.021×0.025-inch stainless steel (SS) (T3) archwires in a sequence. Standardized cone beam computed tomography (CBCT) images were taken immediately after each archwire stage. The differences of premolar teeth BLINC values in the 0.019×0.025-inch and 0.014-inch HANT archwires (T2-T1) and 0.021×0.025-inch SS and 0.019×0.025-inch HANT archwires (T3-T2) were compared between PSL and CL groups. The value of p < 0.05 was considered statistically significant. RESULTS: The BLINC change of the second premolar (SPM) showed a statistically significant difference (p=0.008), but the BLINC change of the first premolar (FPM) (p=0.056) between the groups showed no statistically significant difference during the T2-T1 stage. However, there were statistically significant differences between two groups in the BLINC of the FPM (p=0.032) and SPM (p=0.032) in the T3-T2 stage. The angular changes in the buccal direction in the PSL group were higher than those in the CL group. CONCLUSION: The PSL upper premolar brackets used with the 0.021×0.025-inch SS archwire produced more buccal crown movement of the upper PM teeth compared with that of the CL brackets.

In-vivo effects of flapless osteopuncture-facilitated tooth movement in the maxilla and the mandible.

BACKGROUND: This study aimed to investigate the effects of a minimally invasive, flapless procedure to enhance tooth movement in both jaws and to determine whether this triggers the acceleration when repeated monthly. MATERIAL AND METHODS: The sample consisted of thirty-two individuals whose orthodontic treatment required canine retraction. They were divided into an experimental group and control group. Osteopunctures were performed using orthodontic mini-screws at the distal aspects of the canine teeth at the beginning and on the fourth week of distalization in the experimental group. The control group was treated with conventional mechanics. All canines were retracted. The rates of canine distalization, rotation, and tipping were measured on the first, fourth, and eighth weeks of distalization. First molar anchorage loss was also measured. Intergroup and intragroup analyses were performed. RESULTS: Flapless osteopuncture-facilitated tooth movement resulted in greater canine distalization and reduced molar movement in the maxilla in the experimental than in the control group during the first month of distalization. In addition, the extent of upper canine movement was significantly higher in the experimental group in the first month than in the second. No differences in canine and molar movement in the mandible were observed between the two groups. CONCLUSIONS: OP, as applied in this study, is an effective method for increasing the rate of tooth movement in the maxilla. Repeating the procedure monthly does not appear to show a major advance of tooth movement. Key words:Accelerated tooth movement, flapless osteopuncture.

The Effect of Different Doses of Extracorporeal Shock Waves on Experimental Model Mandibular Distraction.

OBJECTIVE: Distraction osteogenesis (DO) is widely used treatment for the bone deformities. In addition extracorporeal shock wave therapy (ESWT) is a new perspective on noninvasive modalities of management of the bone regeneration. We examined the effects of 2 different single doses of ESWT on the consolidation period of DO of the rabbit mandible using stereological, radiological and immunohistochemical methods in the present study. METHODS: DO was performed unilaterally in the mandible of 18 New Zealand rabbits (6 months' old, weighing between 2.5 and 3 kg). The distraction zone of the mandible has received no treatment as controls. Group 2 (ESWT 500) received ESWT (single dose of 500 impulses 0.19 mJ/mm energy flux intensity and 2155 mJ totally) were applied on the first day of the consolidation. Group 3 (ESWT 1000) treated with ESWT (single dose of 1000 impulses0.19 mJ/mm energy flux intensity and 4310 mJ totally) were applied on the first day of the consolidation period. After the sacrification, radiologically bone mineral density, new bone formation, new fibrous tissue, and new vessel formation were analyzed using unbiased stereological methods. RESULTS: It was found a statistically significant difference between the study groups and control group in the bone mineral density measurements and the highest values were in the ESWT1000 group. In terms of stereological analysis, there was a significant difference between the study groups and control group (P = 0.00). The new capillary volume was highest in the E1000 group. Additionally, significant differences were found in point of the capillary volumes between the groups control and ESWT500 (P = 0.001), control and ESWT1000 (P = 0.000), ESWT500 and ESWT1000 (P = 0.040), respectively. CONCLUSIONS: A total of 1000 impulses ESWT may induce the growth factors to enhance the newly formed bone regeneration.

In-vitro bond strengths and clinical failure rates of metal brackets bonded with different light-emitting diode units and curing times.

INTRODUCTION: The purpose of this study was to compare the clinical failure rates and the in-vitro bond strengths of metal brackets bonded with different light-emitting diode (LED) devices and curing times. METHODS: Forty patients were included in the clinical part of this study. A split-mouth design was used, with the adhesive in group 1 cured for 10 seconds with an LED unit (Elipar S10; 3M Unitek, Monrovia, Calif), and the adhesive in group 2 cured for 3 seconds with another LED unit (VALO Ortho; Ultradent Products, South Jordan, Utah). Bond failures during 12 months of orthodontic treatment were recorded. In-vitro performance of the brackets was also compared by bonding brackets to extracted premolars and using the same light units and curing times (n = 20 for each group). The adhesive remnant index was used to determine the bond failure interface. RESULTS: Clinical bond failure rates were 2.90% for the Elipar and 3.16% for the VALO curing units. The difference in bracket failure rates between the 2 LED devices was not statistically significant. No statistically significant difference was found between the in-vitro bond strengths of the groups. CONCLUSIONS: Our findings regarding long-term clinical survival rates and in-vitro bond strengths indicate that bracket bonding can be safely accomplished in 10 seconds of light-curing with an Elipar LED and 3 seconds of light-curing with a VALO LED.

Investigation of the effect of titanium alloy surface coating with different techniques on titanium-porcelain bonding.

STATEMENT OF PROBLEM: The bond strength of dental porcelain to titanium is inadequate as a clinical alternative to conventional alloys for metal ceramic restorations. PURPOSE: The purpose of this in vitro study was to evaluate the effects of coating titanium surface with a micro-arc oxidation (MAO) technique and hydroxyapatite (HA) on the bond strength of porcelain to titanium surfaces. MATERIAL AND METHODS: One hundred twenty machined titanium specimens with a dimension of 25×3×0.5 mm were prepared from grade 5 titanium as the metal substrate. Specimens were divided into 6 groups (n=20) according to the surface treatment used: airborne-particle abraded (control), coated with MAO for 5 minutes, coated with MAO for 15 minutes, coated with MAO for 30 minutes, coated with HA, and combination of MAO and HA. Each group was further divided into 2 subgroups (n=10) according to the type of porcelain used: Noritake Ti-22 porcelain or Vita-Titankeramik porcelain. The bond strength was tested with a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically with 2-way ANOVA and Tukey honest significant differences multiple comparison tests (α=.05). RESULTS: For both porcelain groups, the 30-minute MAO groups showed higher bond strength values than those of the control groups (P<.05). In the Vita Titankeramik porcelain subgroup, the specimens coated with HA did not show any statistical differences compared with those of the control group (P>.05). Surface roughness was affected significantly (P<.001) by the coating procedure compared to that of the the control group. CONCLUSIONS: Coating with either MAO or HA improved titanium-porcelain adhesion.

Comparison of the frictional characteristics of aesthetic orthodontic brackets measured using a modified in vitro technique.

OBJECTIVE: The coefficients of friction (COFs) of aesthetic ceramic and stainless steel brackets used in conjunction with stainless steel archwires were investigated using a modified linear tribometer and special computer software, and the effects of the bracket slot size (0.018 inches [in] or 0.022 in) and materials (ceramic or metal) on the COF were determined. METHODS: Four types of ceramic (one with a stainless steel slot) and one conventional stainless steel bracket were tested with two types of archwire sizes: a 0.017 × 0.025-in wire in the 0.018-in slots and a 0.019 × 0.025-in wire in the 0.022-in slot brackets. For pairwise comparisons between the 0.018-in and 0.022-in slot sizes in the same bracket, an independent sample t-test was used. One-way and two-way analysis of variance (ANOVA) and Tukey's post-hoc test at the 95% confidence level (α = 0.05) were also used for statistical analyses. RESULTS: There were significant differences between the 0.022-in and 0.018-in slot sizes for the same brand of bracket. ANOVA also showed that both slot size and bracket slot material had significant effects on COF values (p < 0.001). The ceramic bracket with a 0.022-in stainless steel slot showed the lowest mean COF (µ = 0.18), followed by the conventional stainless steel bracket with a 0.022-in slot (µ = 0.21). The monocrystalline alumina ceramic bracket with a 0.018-in slot had the highest COF (µ = 0.85). CONCLUSIONS: Brackets with stainless steel slots exhibit lower COFs than ceramic slot brackets. All brackets show lower COFs as the slot size increases.

Postfabrication thickness of single- and double-layered pressure-formed mouthguards.

AIM: The thickness of a mouthguard (MG) plays an important role in its primary function of preventing injuries. Multi-layered MGs have recently come into prominent use due to the disadvantages associated with single-layered MGs. Whereas researchers have evaluated the postfabrication thickness of single-layered MGs, the effects of fabrication procedures on multi-layered MGs are unknown. This study aimed to evaluate postfabrication thickness of various single-layered and double-layered pressure-formed MGs. MATERIALS AND METHODS: Mouthguards were fabricated using stone models produced from impressions of a phantom model maxillary arch. A total of 50 MGs were fabricated from ethylene vinyl acetate (EVA) sheets and divided into 10 groups of five according to the sheet(s) used in fabrication. The initial thickness of each sheet was recorded prior to fabrication. Following fabrication, MG thickness was measured at seven sites per MG. Data were analyzed using independent t-tests and one-way anova followed by Tukey's test. RESULTS: Mean reduction in MG thickness was 36-38% for single-layered MGs and 32-34% for double-layered MGs. Significant differences in thickness were seen between measured sites for all MG groups (P < 0.05). Maximum thinning occurred at the incisal edge of the central incisor, whereas minimum thinning was observed in the molar crown fissure sites for all groups. CONCLUSION: Clinicians should take into account the effects of fabrication on MG thickness. A loss of thickness of approximately 50% should be expected in critical areas of both single-layered and double-layered MGs made from EVA.

In vitro biomechanical evaluation of modified plating techniques for bilateral sagittal split ramus osteotomy in mandibular advancement.

The aim of this study was to compare the biomechanical properties of modified plate techniques using a newly designed three-dimensional test model after sagittal split ramus osteotomy. Fifteen synthetic polyurethane mandibular replicas were used and divided into 3 groups. Self-tapping 6-mm titanium screws with an outer diameter of 2.0 mm and private designed plates produced by 316-L stainless steel were used in the study. After the osteotomy, the distal part was advanced by 5 mm. The jaw models were placed to the three-dimensional test model designed by the authors, and the Instron Lloyd LRX device was used to apply a double-sided tensile force from the mandible angulus region of each group. Resistance forces that caused a displacement of 1.5 and 3 mm were recorded with the Instron program. The mean (SD) of the 3 groups were calculated using analysis of variance and the Tukey test. The results were compared statistically, with values of P < 0.05 determined as statistically significant. On the basis of the results of the Tukey comparison within the groups, there was a statistically significant difference between groups 1 and 2 and between groups 1 and 3 at both 1.5- and 3-mm displacement (P < 0.05). No significant difference was observed between groups 2 and 3 (P > 0.05). This test model was able to identify the most appropriate plate type of 3 different modified plate techniques after sagittal split ramus osteotomy.

The clinical and laboratory effects of bracket type during canine distalization with sliding mechanics.

OBJECTIVE: To compare the extent of canine movement with sliding mechanics between a self-ligating (SC) bracket and a modified twin design (MT) bracket. To test the in vitro coefficient of friction (COFs) of these two metal brackets on 0.019- × 0.025-inch, stainless-steel arch wires. MATERIALS AND METHODS: For the clinical portion of this study, a split-mouth design was used to bond the brackets of 19 patients. Canine distalization was achieved on a 0.019- × 0.025-inch, stainless-steel arch wire with a nickel-titanium, closed-coil spring strained between a mini-screw and a canine bracket. The linear and angular measurements were performed using lateral cephalometric radiographs taken before and after canine distalization. A tribometer was also used to measure the COFs of the bracket types in vitro. For comparisons, Student's t-tests for paired and unpaired samples were used at the 95% confidence level. RESULTS: The extent of canine movement and the changes in the canine and molar teeth angles were not significantly different between the SC and MT brackets. After 8 weeks, the mean canine movements were 1.83 and 1.89 mm in the maxilla and 1.79 mm and 1.70 mm in the mandible with the SC and MT brackets, respectively. The mean COF of the MT brackets (0.21) was significantly lower than that of the SC brackets (0.37) during in vitro testing. CONCLUSION: It is suggested that the rate of canine distalization was not different between the two groups, although in vitro COFs of the SC bracket was higher.

Effects of first molar extraction on third molar angulation and eruption space.

OBJECTIVES: The aim was to investigate the effects of orthodontic treatment with 4 first molar extractions on the angulations and eruption spaces of all third molars and to compare these changes with outcomes of nonextraction samples used as a control group. STUDY DESIGN: This study was carried out on standardized panoramic radiographs of 41 subjects (8 male, 33 female) with a mean age of 16.6 years (range 13 to 20 years). Twenty-one of the subjects were orthodontically treated with extraction of the 4 first permanent molars, and 20 had nonextraction treatment. The angulational changes and eruption spaces of third molars were evaluated on the panoramic radiographs taken before treatment and at the end of the observation period. RESULTS: Analysis of the linear variables demonstrated a statistically significant difference between the 2 groups for all third molar eruption spaces (P < .001). The mean differences in the third molar eruption spaces between the pretreatment and posttreatment values for the first molar extraction group were higher than those of the nonextraction cases. CONCLUSION: Orthodontic treatment accomplished with extractions of the permanent first molars increases the eruption spaces of third molars and decreases their impaction. In addition, it has greater favorable effect on the angulation of the upper third molars than of the lower third molars.

Effects of fixed functional appliance treatment on the temporomandibular joint.

INTRODUCTION: In this study, we tested the hypothesis that fixed functional appliance treatment in a group of Class II Division 1 patients with mandibular retrusion changes the condyle position in the glenoid fossa. METHODS: Transverse computed tomography images were taken of the temporomandibular joint region in 60 children with Class II Division 1 malocclusion. Thirty randomly selected patients were treated with a fixed functional orthodontic appliance (Forsus nitinol flat-spring, 3M Unitek Corp, Monrovia, Calif) for 7 months; another 30 patients without treatment were used as controls. Computed tomography images taken at the beginning and end of fixed functional appliance treatment were used for estimating the condyle-glenoid fossa relationship, including the volumes of condyle, glenoid fossa, and anterior and posterior joint spaces. RESULTS: Although the volumes of the condyle and glenoid fossa increased more in the study group than in the control group, the differences were not statistically significant. However, statistically significant differences were found between the groups in the volumes of the anterior and posterior joint spaces (P < 0.05). CONCLUSIONS: When the volumes of the anterior and posterior joint spaces changed, the condyle was more posteriorly positioned in the glenoid fossa in the study group than in the control group.

Evaluation of Treatments in Patients with Nocturnal Bruxism on Bite Force and Occlusal Contact Area: A preliminary report.

OBJECTIVES: The purpose of this study was to investigate the short-term effects of occlusal splint therapy and tricyclic antidepressants on the bite force and occlusal contact area of patients presenting with nocturnal bruxism. METHODS: A maxillary full-coverage hard acrylic splint was applied to the five patients (Group S). Five patients took a tricyclic antidepressant (Amitriptiline HCl, 10 mg/day) for 3 months (Group A) and a control group (Group C) comprising of 10 dental school students with normal occlusion was also formed. Using a Dental Prescale (Fuji Photo Film Corporation, Tokyo, Japan) and an Occluzer computer (FPD703, Fuji Photo Film Corporation, Tokyo, Japan) the bite force and occlusal contact area were measured. The evaluations were made just before the treatment and at 1 month and 3 months of treatment. RESULTS: The bite force and occlusal contact area before treatment in study Groups A and S were found to be higher than those in the Group C. Furthermore, the bite force and occlusal contact area increased during treatment in Group A whilst they decreased in Group S. Bite force and occlusal contact area in Group S were lower at both 1 month and 3 months of treatment than in Group C. CONCLUSIONS: It could be tentatively suggested that occlusal splint therapy may be more effective than tricyclic antidepressant in the treatment of bruxism. Further investigations of this measurement method involving larger study populations and a longer follow-up period are needed.

Comparison of different toothbrushing protocols in poor-toothbrushing orthodontic patients.

The aim of this study was to determine, using a computerized image analysing system, whether the use of a curved-bristle toothbrush (CBT) alone is more effective than two other toothbrushing protocols on dental plaque elimination in poor-toothbrushing orthodontic patients. The labial surfaces of the maxillary canine-to-canine anterior teeth of 30 patients (12 males and 18 females) were individually photographed following dental plaque staining before and 4 weeks after each toothbrushing protocol, with a 1-month washout interval. The toothbrushes used were (1) a CBT, (2) an orthodontic toothbrush (OT), and (3) an OT in combination with interproximal toothbrush (IT) (OT + IT). Total labial surfaces of the anterior teeth and stained plaque areas were measured and gingival indices (GIs) were also recorded. Repeated measures analysis of variance and Tukey's Honestly Significant Difference multiple range tests showed that the OT + IT produced a statistically significant decrease in the mean plaque percentage both for the total labial (7.2%) and interproximal (17.7%) tooth surfaces, when compared with the other toothbrushing protocols (P < 0.05). No statistically significant differences were found between the CBT and OT for the amount of bacterial plaque and GI scores (P > 0.05). Neither the CBT nor the OT alone was able to remove plaque under the archwires in poor-toothbrushing patients. Therefore, the use of ITs should be mandatory for effective plaque removal in these patients.

Mandibular asymmetry in different occlusion patterns.

OBJECTIVE: To investigate the effects of different occlusion types on the mandibular asymmetry in young individuals. MATERIALS AND METHODS: Mandibular asymmetry measurements were performed on the panoramic radiographs of 189 subjects (104 females and 85 males; age range, 11-15 years), with different occlusion patterns. The subjects were divided into five groups according to the occlusion types, namely, Angle Class I (Cl I), Class II division 1 (Cl II/1), Class II division 2 (Cl II/2), Class III (Cl III), and normal occlusions. The Kruskal-Wallis test was used to determine the possible statistically significant differences between the groups for condyle, ramus, and condyle-plus-ramus asymmetry index measurements. Identified differences between groups were further analyzed using the Mann-Whitney U-test at the 95% confidence interval (P<.05). RESULTS: There were no statistically significant differences between male and female subjects. The Kruskal-Wallis test showed that the occlusion type had a significant effect on the condylar asymmetry. In Cl II/1 cases, condylar asymmetry values were significantly different from the values of Cl II/2 and Cl III malocclusion and normal occlusion types. The normal occlusion control group was significantly different from those of Cl II/1 and the Cl I malocclusion groups. CONCLUSION: Cl II/1 malocclusion has a significant effect on the condylar asymmetry index when compared to Cl II/2 and Cl III malocclusion and normal occlusion types. However, the mean condylar asymmetry index value in Cl II/1 malocclusion was not different from Cl I malocclusion.

Nonextraction treatment with rapid maxillary expansion and mandibular symphyseal distraction osteogenesis and vertical skeletal dimensions.

OBJECTIVE: To investigate the effects of rapid maxillary expansion (RME) and mandibular symphyseal distraction osteogenesis (MSDO) on vertical dimensions of the face. MATERIALS AND METHODS: Fourteen patients, nine girls and five boys, underwent RME and MSDO procedures. Distraction was carried out at a rate of 1 mm per 24 hours with a tooth-borne appliance. The amount of distraction was 7 mm for each patient. Standardized lateral cephalograms were taken at the following time periods: before treatment (T0), after RME (T1), at the completion of MSDO (T2), and at the end of fixed orthodontic treatment (T3). The data were evaluated by using a general linear model of repeated-measures analysis of variance and paired t-tests at the 95% confidence level. RESULTS: RME significantly increased the vertical dimensions of the face and decreased the overbite (P < .001). Although the vertical parameters of the face on the lateral cephalogram decreased after MSDO, these decreasing effects were statistically insignificant just for the distances measured from the horizontal reference line to the chin points. In other words, MSDO decreased the vertical skeletal dimensions that were increased by RME, but this neutralizing effect of MSDO was not as much as the increase caused by RME. CONCLUSION: Treatment modalities (RME, MSDO, and fixed orthodontic treatment) described in this study, in total, had little effect on the vertical skeletal measurements of the face.

The effect of periodontitis on biting abilities.

BACKGROUND: The aim of this study was to compare the biting abilities (bite force [BF] and occlusal contact area [OCA]) of chronic periodontitis patients with those of control patients with healthy periodontia by using pressure-sensitive sheets. METHODS: The study population consisted of 20 patients with chronic periodontitis whose initial periodontal therapy was completed and 20 control subjects with healthy periodontia. Periodontitis was diagnosed by radiographs and measurements of probing depth and clinical attachment level. Pressure-sensitive sheets were used for the quantitative analysis of BF and OCA. RESULTS: Both mean BF and OCA values were greater in the healthy control group compared to those of the study group. The differences between the groups were statistically significant at the 95% confidence level. CONCLUSION: Reduced periodontal support in the absence of inflammation negatively affected biting abilities.

The effect of periodontal surgery on bite force, occlusal contact area and bite pressure.

BACKGROUND: Tooth mobility resulting from the loss of periodontal support or trauma induced by periodontal surgery may change the amount of bite force (BF) and bite pressure (BP) and number of occlusal contact areas (OCAs). The aim of the authors' study was to compare BF, BP and OCA of teeth with periodontal disease before and after periodontal surgery with similar values of healthy teeth. METHODS: The authors performed quantitative analysis of BF, BP and OCA using a pressure measurement film. Ten patients with periodontitis who needed periodontal surgery served as the test group. The authors took measurements of BF, BP, OCA and mobility (using Miller's Mobility Index) just before surgery and at one, four and 12 weeks after surgery. They also measured clinical attachment levels (CAL) before surgery and 12 weeks after surgery. Ten subjects without periodontitis served as the control group. RESULTS: Although BF and OCA increased the first week after periodontal surgery, analysis of variance (ANOVA) showed no statistically significant differences at a 95 percent confidence interval. There were statistically significant differences between first-week mobility and that at four and 12 weeks (P = .001). A factorial ANOVA showed significant interaction between BF and mobility (P < .05). CONCLUSIONS: The authors' findings suggest that changes in BF, BP and OCA were not affected by periodontal surgery. However, mean mobility values and BF are correlated. Further investigations of this measurement method involving larger study populations and a longer follow-up period are needed. CLINICAL IMPLICATIONS: It seems to be helpful to follow occlusal changes after periodontal surgery using a pressure measurement film. It also may be suggested that this measurement method could be used to evaluate the treatment prognosis.

Bite force and occlusal contact area changes following mandibular widening using distraction osteogenesis.

OBJECTIVE: To examine changes in bite force and occlusal contact area after mandibular widening by distraction osteogenesis using pressure-sensitive sheet (Dental-Prescale; Fuji Photo Film, Tokyo, Japan). STUDY DESIGN: Fifteen patients with transverse mandibular deficiency (6 to 9 mm, mean distraction interval: 8 mm) were examined. They were measured just before the operation and at 1 week, 1 month, 3 months, 6 months, and 1 year after the operation. Ten control subjects with normal occlusion were also measured. RESULTS: Both bite force and occlusal contact area were lowest at 1 month postoperatively. The values of bite force and occlusal contact area steadily increased thereafter. The bite force and occlusal contact area reached to the preoperative levels at 6 months after operation and slightly above the preoperative level at 12 months after operation. There were no statistically significant differences between 12 months and the control values for bite force measurements (P > .05). CONCLUSION: Although statistically not significant, this study suggests that mandibular symphyseal distraction osteogenesis increases the bite force and occlusal contact area in patients with transverse mandibular deficiency.