The effect of age on condylar asymmetry in patients with craniomandibular disorders of arthrogenous origin

The temporomandibular joint of California sea lions (Zalophus californianus): part 2-osteoarthritic changes

OBJECTIVES

Following comprehensive characterization of the temporomandibular joint (TMJ) of the California sea lion, as well demonstrating that TMJ-osteoarthritis (OA) occurs in this species, the objective of this part of the investigation was to describe the macroscopic osteologic findings associated with TMJ-OA in a large museum collection of skull specimens.

DESIGN

Museum skull specimens (n=497) of California sea lions were examined macroscopically according to defined criteria for the presence, severity, location and characteristics of TMJ-OA. The specimens, acquired from strandings, varied in age from young adults to mature adults.

RESULTS

Overall 63.5% of the specimens had findings consistent with TMJ-OA. Of these, 56.2% were from females 43.8% were from males. Moreover, 71.2% specimens were from mature adults and 28.8% from young adults. However, there was no significant association between age and sex with the presence or severity of TMJ-OA. The most prominent TMJ-OA changes were the presence of subchondral bone defects and abnormal porosity. The majority of the OA present at the mandibular head affected the entire articular surface. In contrast, the OA present on the mandibular fossa of the temporal bone was located primarily on the medial aspect (P<0.001).

CONCLUSION

The incidence of TMJ-OA in California sea lions is high and varies in severity. Although the significance of the high incidence of this disease in the California sea lion remains elusive, the occurrence and severity of TMJ-OA detected in this study may play an important role in the species' morbidity and mortality.

Three-dimensional condylar positions and forms associated with different anteroposterior skeletal patterns and facial asymmetry in Chinese adolescents

OBJECTIVE

To evaluate the association of condylar asymmetry and chin position with different anteroposterior skeletal patterns using three-dimensional models reconstructed from cone-beam computed tomography (CBCT) images.

MATERIALS AND METHODS

CBCT scans of 123 Chinese adolescents (aged 11-15 years, 68 girls and 55 boys) with 64 skeletal Class I, 46 Class II and 13 Class III were selected from scans of patients attending the orthodontic clinic. The condyles of the subjects were reconstructed bilaterally and 25 linear, angular and volumetric measurements were performed to evaluate the asymmetry of the condyles and position of the chin. The proportions of condylar asymmetry in the different skeletal groups were calculated by the absolute difference value between the left and right sides to the smaller side value. One-way analysis of variance and Pearson's correlations were used to analyse the data.

RESULTS

The values for RV, RCL, LCH, RCH, LCGM, RCGM, LCo-Me and RCo-Me were significantly different among the three skeletal groups (p < 0.05). There were significant positive correlations between Pog-Ss and Co-Sh, Co-Me in the Class I and II groups (p < 0.05). Asymmetries for Co-Ss, Co-Sh, CP and SP between the left and right condyles exceeded a ratio of 20% for more than 30% of the subjects.

CONCLUSION

Condylar asymmetry varied significantly among the three skeletal groups, with the vertical position of the condyle (Co-Sh) and height of the mandibular ramus (Co-Me) being significantly and positively related to the chin position.

Osteoarthritis of the temporomandibular joint in southern sea otters (Enhydra lutris nereis)

Museum skull specimens (n = 1,008) of southern sea otters (Enhydra lutris nereis) were examined macroscopically according to defined criteria for the presence, severity and characteristics of temporomandibular joint osteoarthritis (TMJ-OA). The specimens were from stranded young adult to adult animals. Overall, 4.1% of the specimens had findings consistent with TMJ-OA. Of these, 61.0% were from females and 39.0% were from males. In addition, 85.4% of the affected specimens were from adults and 14.6% were from young adults. However, there was no significant association between age and sex with the presence or severity of TMJ-OA. Lesion severity was mild in 41.5%, moderate in 19.5% and severe in 39.0% of affected specimens. The most prominent changes were the presence of osteophytes and subchondral bone defects and porosity. The mandibular condylar process and fossa were affected equally. The lengths of the right and left mandibular heads were significantly associated with age (P = 0.002 and P = 0.003, respectively) and sex (P = 0.0009 and P = 0.001, respectively), but not with the presence of TMJ-OA. The significance of this disease in sea otters remains elusive, but this condition may play an important role in survival of these animals.

Association between condylar asymmetry and temporomandibular disorders using 3D-CT

Objectives: Using reconstructed three-dimensional computed tomography (3D-CT) models, the purpose of this study was to analyze and compare mandibular condyle morphology in patients with and without temporomandibular disorder (TMD). Study Design: Thirty-two patients were divided into two groups: the first comprised those with TMD (n=18), and the second those who did not have TMD (n=14). A CT of each patient was obtained and reconstructed as a 3D model. The 64 resulting 3D condylar models were evaluated for possible TMD-associated length, width and height asymmetries of the condylar process. Descriptive statistics were used to assess the results and student’s t tests applied to compare the two groups. Results: Statistically significant (p<0.05) vertical, mediolateral and sagittal asymmetries of the condylar process were observed between TMD and non-TMD groups. TMD patients showed less condylar height (p<0.05) in comparison with their asymptomatic counterparts. Conclusions: Using 3D-CT, it was shown that condylar width, height and length asymmetries were a common feature of TMD.

Key words:Condilar asymmetry, 3D-computed tomography, X-ray diagnosis , maxillofacial surgery, orthodontics.

A preliminary anatomical study on the association of condylar and occlusal asymmetry

The aim of this study was to test the hypothesis that condylar and occlusion asymmetry are not associated. For each of 22 skulls, the asymmetry of condyles was graded by one examiner and the asymmetry of occlusion by another examiner, both blinded to each other's evaluation, as 0 = symmetrical, 1 = mild asymmetrical and 2 = severe asymmetrical. There were 18 condyles graded the same as to their occlusion, but in four, the grades differed by one degree. Nine were graded symmetrical, seven were mild, and six were graded severely asymmetrical condyles. The corresponding figures for occlusion were: 10 were graded symmetrical, seven were graded mildly asymmetrical, and five were graded severely asymmetrical occlusion. The relation between occlusion and condylar asymmetry was tested using Goodman-Kruskal's gamma and was found to be 0.970 (p < 0.001). The null hypothesis was not supported. The results indicate that asymmetry of occlusion and condyles are associated, which indicates the need for further studies on larger samples, and in vivo studies.

Molar bite force and its correlation with signs of temporomandibular dysfunction in mixed and permanent dentition

The aim of the study was to evaluate molar bite force (BF) magnitude and its correlation to the signs of temporomandibular dysfunction (TMD), gender, weight, height and age in 101 students ranging in age from 6 to 18 years (32 boys/21 girls with mixed dentition and 23 boys/25 girls with permanent dentition). TMD clinical signs were evaluated using the Craniomandibular Index (CMI), and two subscales, the Dysfunction Index (DI) and the Palpation Index (PI). BF was determined with a pressurized tube connected to a sensor (MPX5700-Motorola SPS). anova, Tukey's test, and Pearson's and Spearman's coefficients were evaluated. BF was higher in the permanent dentition (P < 0.05). There was no difference in BF between genders within the groups, but boys with permanent dentition had higher values than children with mixed dentition (P < 0.05). The girls with permanent dentition presented negative correlation in BF with PI and CMI (P < 0.05). BF was positively correlated with weight, height and age in the permanent dentition group (P < 0.05). It was concluded that BF increased from mixed to permanent dentition, with an assumed enhancing influence of body variables and ageing. The TMD signs in older girls were correlated to decreasing BF, suggesting an influence of muscle tenderness preventing subjects from exerting maximum BF.

Asymmetry of the articular eminence in dentate and partially edentulous populations

The purpose of this study was to assess the degree of right-left asymmetry of the glenoid fossa. The specific aims were (1) to determine whether there were relationships between age, number of teeth, slope of the articular eminence, fossa depth, and the degree of right-left asymmetry, and (2) to compare the right-left asymmetry of two populations, one characterized by an acceptable occlusion (A-Occ), the other by an unacceptable occlusion (partially edentulous; Un-Occ). A-Occ was defined as possessing a minimum of 28 teeth that would allow for hand articulation of the mandibular teeth to the maxillary teeth. Un-Occ had fewer than 17 teeth, which would make it impossible to articulate the mandible with the maxilla. The sample included 20th century dry skulls: 70 African-American (44 male, 26 female) and 64 European-American (49 male, 15 female), ranging in age from 21-105 (mean 47.1 +/- 19.9). The medial (M), central (C), and lateral (Lat) aspects of the right (R) and left (L) slopes of the articular eminence were measured in a sagittal plane. The R and L fossa depth also were measured. The raw absolute differences IR-LI and relative differences [IR-LI/IR+Llx100] of the articular slope angles (M, C, and Lat) and fossa depths were computed. Statistical analysis included paired t-tests, independent t-tests, and Pearson's correlation coefficients, significance at p < or = 0.05. Ninety percent (90%) of the population exhibited right-left asymmetry of the glenoid fossa. The right articular slopes (M, C, and Lat) were significantly steeper than the left articular slopes; the right fossa depths were significantly deeper than the left. There generally were no differences in the articular slope steepness or fossa depths between the partially dentate and the dentate, nor were there statistical differences between the two groups in the raw absolute differences or relative differences of the M, C, and Lat slopes or fossa depths. No significant relationships were found between right-left asymmetry, age, or number of teeth. With only 10% of the subjects exhibiting symmetry of the glenoid fossa depths or articular slope angles, clinicians should consider bilateral asymmetry the norm and not an anomaly.

Tomographic evaluation of TMJ in adolescents with temporomandibular disorders

This study evaluated the TMJ images of normal subjects and of those who presented TMD (temporomandibular disorders) using linear tomography at rest position. Craniomandibular Index (CMI) and a questionnaire on subjective symptoms were used to assess 217 subjects aged 12 to 18 years. Those with the highest and the lowest scores were divided into Control (n = 20) and TMD groups (n = 20), respectively. Corrected tomography was used to measure the narrowest anterior, superior and posterior joint spaces, to determine the condyle position in all 40 subjects. The distance means did not correlate with CMI scores (p > 0.05). The number of posteriorly positioned condyles was significantly higher in TMD patients (p = 0.05), especially in females. It was concluded that condyle position in linear tomography at rest position cannot yield TMD diagnosis.

Efficacy of Root Canal Preparation by Er,Cr:YSGG Laser Irradiation with Crown-Down Techniquein Vitro

OBJECTIVE

The purpose of this study was to compare the efficacy of Er,Cr:YSGG laser in root canal preparation and its effectiveness in removing debris and smear layer with the efficacy of the conventional hand instrument, in vitro.

BACKGROUND DATA

Recently, the use of the Er,Cr:YSGG laser device in root canal preparation has been excepted in the dental clinic. However, there have been no published reports on root canal preparation by using the Er,Cr:YSGG laser irradiation.

MATERIALS AND METHODS

A total of 40 straight root canals were prepared by an Er,Cr:YSGG laser at a output power of 2 W, and 40 canals were shaped by using the K file under irrigation with NaOCl and H2O2 by using the crown-down technique (control). The achievement degree of root canal preparation and debris score was morphologically investigated.

RESULTS

The results showed that great improvement in the cleanliness of the walls was found using the laser technique as compared with the control technique; a significant decrease in smear layer or debris was also recognized in laser-prepared canals (p < 0.01). But canal preparations with the laser device sometime result in ledge, zipped, perforation, or over-instrumentation.

CONCLUSION

The results demonstrated that root canal preparations with the laser device were significantly worse than in the control group. Further development in laser device and technique are required to ensure its success in root canal preparation.

The condylar asymmetry measurements in different skeletal patterns

In the present study, condylar asymmetry measurements were investigated on the lateral cephalometric head radiographs and the panoramic radiographs of 72 subjects (36 males and 36 females), aged 12-16-years and having different skeletal patterns. The lateral cephalometric head radiographs were divided into three groups according to the ANB angle: ANB angles smaller than 1 degrees, between 1 degrees and 5 degrees, and larger than 5 degrees. In addition, each group was also divided into two subgroups according to sex. The effects on the ANB angle and sex on the condylar asymmetry measurement were investigated on the panoramic radiographs by means of variance analysis. It was observed that while condylar + ramus ratio measurement was affected by the change of ANB angle, the other measurements were not affected by it.

A comparative study on compositional changes and Knoop hardness measurement of the cavity floor prepared by Er:YAG laser irradiation and mechanical bur cavity

OBJECTIVE

This present study was performed to compare the compositional changes of human dentin and, Knoop hardness of the cavity floor prepared by Er:YAG laser irradiation with that of the conventional bur cavity.

BACKGROUND DATA

There are still no reports on the compositional changes of dental hard tissues and microhardness of the cavity floor prepared by Er:YAG laser irradiation.

MATERIALS AND METHODS

Fifteen laser and 15 bur cavities were cross-sectioned, and subjected to atomic analysis by SEM-EDX and Knoop hardness testing. Statistical analyses were performed using the Mann-Whitney U test; a value of p < 0.01 was considered significant. Cross sections of the remaining five laser and five bur cavities were examined by light microscopy and then by SEM.

RESULTS

The results showed that the quantities of Ca (Ca weight %) and P (P weight %) were increased significantly in the laser cavities, but no significant differences were found between the Ca/P ratio and Knoop hardness number of laser and bur cavities. The results of SEM observation revealed that the lased cavity surface was irregular, and there was also the absence of a smear layer; the orifice of dentinal tubules was exposed.

CONCLUSION

Er:YAG laser device produces minimal thermal induced changes of dental hard tissue compositions; Ca/P ratio and Knoop hardness of the lased cavity floor was almost similar to the bur cavities.

Morphological and microleakage studies of the cavities prepared by Er:YAG laser irradiation in primary teeth

OBJECTIVE

The purposes of this study were to investigate cavity surfaces morphologically, and compare microleakage at cavities prepared by Er:YAG laser after composite resin restoration versus conventional mechanical treatment in human primary teeth in vitro.

BACKGROUND DATA

There have been few reports on microleakage at cavities prepared by Er:YAG laser irradiation.

MATERIALS AND METHODS

A total of 30 cavities (class V) in human primary teeth were used. Half of the cavities were prepared by an Er:YAG laser system at 300 mJ pulse energy and 4 Hz, and the other half were prepared with a high-speed diamond bur. Five cavities from each group were investigated by scanning electron microscopy (SEM) and histopathological examination. Remaining cavities were filled with a composite resin without an acid-etching technique and then subjected to microleakage test in 0.6% rhodamine B solution under thermocycling.

RESULTS

Microleakage (score: 2.45 +/- 1.07) at cavities prepared by laser was significantly less than that by bur (score: 1.30 +/- 0.95; p < 0.05). SEM observation showed that, compared with the relatively flat appearance of cavities prepared by bur, cavity margins prepared by laser were irregular but there was almost no smear layer at the cavity walls.

CONCLUSION

It can be concluded that cavity surfaces prepared by Er:YAG laser are irregular, but microleakage at cavities prepared by the laser after filling with composite resin is better than that by mechanical bur using the dye penetration method.

Er:YAG laser effects on enamel occlusal fissures: an in vitro study

This study evaluated by scanning electron microscopy (SEM) the morphological changes in occlusal fissure enamel, of permanent models, irradiated by Er:YAG laser using contact and noncontact fiberoptics in vitro. Previous studies have demonstrated the efficacy of Er:YAG laser for dental hard tissue removal and cavity preparation. The treatment of occlusal fissures in noncarious permanent human molars (n = 9) was carried out with Er:YAG laser (KEY Laser II) using handpiece no. 2051, noncontact, focused (12 mm), water spray-cooled, pulse energy 200 mJ, and frequency 2 Hz (group 1), and handpiece no. 2055 with a quartz fiberoptic 50/10, in contact, air cooled, pulse energy setting of 350 mJ and frequency 2 Hz (group 2) and 400 mJ/2 Hz (group 3). The specimens were sectioned, dehydrated in a graded series of aqueous ethanol, dried, and sputtering with gold. Morphological change analysis on occlusal fissures was performed by SEM. Group 1 showed removal of fissure debris and predominantly enamel etching-like patterns, and groups 2 and 3 showed irregular edges, melting, and recrystallization of fissure enamel, with a lava-like structure and bubble-like voids. The results of this in vitro study suggest that the irradiation of fissures by Er:YAG laser using a fiberoptics (contact and air cooled) produced melting and recrystallization of fissures enamel. Further studies are required with different energy parameters and water cooling to evaluate the thermal effects on teeth.

Clinical assessment of Er,Cr:YSGG laser application for cavity preparation

In this study, an erbium,chromium:YSGG (Er,Cr:YSGG) laser emitting at a wavelength of 2.78 microm was clinically applied to remove caries and prepare cavities, and the clinical outcome was evaluated. Effective clinical application of Er,Cr:YSGG laser had been expected from previous studies. This study included 44 patients (26 females, 18 males; aged 23-58) with a total of 50 cavity preparations by the Er,Cr:YSGG laser irradiation at 3-6 W with water spray. Patient acceptance and prognosis were evaluated. Most cases (94%) were prepared without anesthesia, and no pain was felt in 34 cases (68%). No adverse reaction was observed in any of the cases, and patient acceptance for this system was favorable. All cases had a good prognosis. In 45 cases (90%), overall clinical evaluation was satisfactory. From the present study, it can be concluded that the Er,Cr:YSGG laser system is an efficient, effective, and safe device for caries removal and cavity preparation.

Comparison between the removal effect of mechanical, Nd:YAG, and Er:YAG laser systems in carious dentin

OBJECTIVE

The purpose of this study was to compare the effectiveness of carious dentin removal by using an Er:YAG laser irradiation and Nd:YAG laser under a continuous water spray with that of the conventional mechanical treatment in vitro.

BACKGROUND DATA

Lasers are being considered as a potential replacement of conventional mechanical systems to remove diseased and healthy dental hard tissues.

METHODS

First, one half of the 10 carious lesions were treated with the round steel bur and then removed. The other half were treated with the Er:YAG laser at 200-mJ pulse energy at 2 Hz. After that, one half of another set of 10 teeth was subjected to the round steel bur in which the other half was removed using the Nd:YAG laser at 6-W output power, 20 pps, and under a continuous water spray (120 mL/min). Thermal change during each treatment and the time required for carious dentin removal was determined, and the surface characteristic was observed using the scanning electron microscopic (SEM).

RESULTS

The Er:YAG or Nd:YAG laser irradiation time was almost two or three times longer than the bur treatment, respectively. From the SEM study, it was found that the lased cavity surface revealed various patterns of microirregularity, and there was also no smear layer.

CONCLUSIONS

It can be suggested that under adequate water spray and with a careful irradiation technique, cavities without sign of thermal damage to the surrounding tissues as well as dental pulp could be produced with the Er:YAG and Nd:YAG laser.

Removal of carious dentin by Er:YAG laser irradiation with and without carisolv

OBJECTIVE

The purpose of this study was to investigate the effectiveness of caries removal by using an Er:YAG laser irradiation with and without Carisolv, in vitro.

BACKGROUND DATA

Effective ablation of dental hard tissues using Er:YAG laser has been reported and its application to caries removal has been expected.

METHODS

Five extracted human teeth were selected for Carisolv and burr treatment. One-half of the lesion was treated with the Carisolv and then removed. The other half was removed using burr treatment. Fifty teeth were subjected to Er:YAG laser treatment with and without Carisolv. First, Carisolv was applied on one-half of each carious lesions for 1 min and followed by the Er:YAG laser irradiation at 60-140 mJ, 2 Hz for another 1 min; the other half was treated with Er:YAG laser only. The cavity was carefully assessed by DIAGNOdent. Each lesion was photographed before and after treatment, and the treated cavity was observed by microscopy and with scanning electron microscope (SEM).

RESULTS

Our results revealed that application of Carisolv followed by Er:YAG laser irradiation at 100-140 mJ pulse energy effectively removed dentin caries. From the SEM study, it was found that the cavity surface treated with the laser revealed various patterns of microirregularity, often accompanied by microfissure propagation. There was also no smear layer.

CONCLUSIONS

It was revealed that Er:YAG laser and Carisolv could provide an alternative technique for caries removal for conventional mechanical drilling and cutting.

Effects of Er,Cr:YSGG laser irradiation in human enamel and dentin: ablation and morphological studies

OBJECTIVE

This investigation was performed to determine quantitatively the ranges of ablation and to evaluate the morphological changes in human enamel and dentin irradiated by Er,Cr:YSGG laser with or without water spray.

SUMMARY BACKGROUND DATA

Recently, Er,Cr:YSGG laser has been introduced in dental clinics to remove carious dental hard tissues in anticipation of replacing the high-speed dental drill.

METHODS

A total of 40 extracted human teeth were used in this study. An Er,Cr:YSGG laser was used to ablate human dental hard tissues with the output powers of 3 to 6 W. Ablation extent with or without water spray at different output powers was measured, and the morphological changes on enamel and dentin were also investigated by stereoscopy and scanning electron microscopy (SEM).

RESULTS

The irradiation with water spray significantly (p < 0.001) increased the ablation depths compared to those irradiated without water mist. Morphological findings by SEM indicated that when irradiated without water spray, carbonization with brown or dark color was recognized in enamel or dentin, respectively. In addition, cavities with a molten lava-like appearance were produced and an irregular structure with many microholes was observed in dentin.

CONCLUSIONS

These results suggest that during the Er,Cr:YSGG laser irradiation, water spray directed at the ablation sites increases the ablation depths and water plays an important role as an initiator of the ablation of dental hard tissues.

Caries-preventive effect of Er:YAG laser irradiation with or without water mist

OBJECTIVE

This investigation was performed to evaluate the effect of Er:YAG laser irradiation on the acquired acid resistance of sound dental hard tissues to artificial caries formation by spectrophotometry, and the ultrastructure of lased areas was investigated by scanning electron microscopy (SEM) in vitro.

BACKGROUND DATA

Although an Er:YAG laser has shown the most promise for hard tissue ablation, there have not been any dissolution studies to determine if this laser is suitable for caries preventive treatments.

METHODS

An Er:YAG laser was used to irradiate the enamel and dentin samples from 20 extracted human molars at 400 mJ pulse energy with or without water mist. Samples were subjected to 2 microL of 0.1 M lactic acid solution (pH 4.8) for 24 hours at 36 degrees C. The parts per million (ppm) of calcium ion (Ca2+) dissolved in each solution was determined by atomic absorption spectrophotometry and the morphological changes were investigated by SEM.

RESULTS

The lowest mean Ca2+ ppm was recorded in the samples irradiated without water mist, in those by irradiated with water mist, and in the unlased samples. SEM observation showed that the lased areas had melted and seemed to be thermally degenerated when irradiated without water mist. After acid demineralization, the thermally degenerated enamel or dentin surfaces were almost unchanged.

CONCLUSIONS

The results of this study suggest that Er:YAG laser irradition with and without water mist appears to be more effective for caries prevention.

Effects of copper vapor laser irradiation in human enamel and dentin: ablation and morphological studies

OBJECTIVE

This investigation was performed to determine the ranges of ablation quantitatively and to evaluate the morphological changes in human enamel and dentine irradiated by a green copper vapor laser.

SUMMARY BACKGROUND DATA

Recently, green copper vapor laser (CVL), which is said to have characteristics similar to the argon laser has been introduced in dentistry.

METHODS

Extracted noncarious human teeth were used in this study. A CVL was used to ablate human dental hard tissues with the output powers of 2.0 W. Ablation extent without water spray using red or black ink was measured, and the morphological changes on enamel and dentin were also investigated by stereoscopy and scanning electron microscopy (SEM).

RESULTS

In the samples, irradiated by a CVL after painting red ink on the surface, the ablation depth was increased more than that of irradiation after painting with black ink. Morphological findings by SEM indicated that when irradiated with red ink, brown carbonization was recognized on enamel and dentin surfaces. In addition, cavities with a molten lava-like appearance were produced and an irregular structure with many microholes was observed in the enamel and dentin. Alternatively, a shallow cavity with little carbonization was produced with black ink.

CONCLUSIONS

Removal of dental hard tissues appears to be possible using the CVL. However, further studies should be performed on the selection of radiation conditions that achieve the desired ablation with minimal side effects.

A study on the morphological changes of the rat mandibular bone with TEA CO2 laser

OBJECTIVE

The purpose of this study was to investigate the morphological changes of the bone structure induced by transversely excited, atmospheric TEA pressure CO2 laser irradiation. Moreover, the healing process at 3 weeks was also observed.

SUMMARY BACKGROUND DATA

It has been demonstrated that dental hard tissue can be removed by a long pulse of TEA CO2 laser irradiation with minimal thermal damage. However, there are few studies on the morphological changes of the TEA CO2 laser on bone tissue.

METHODS

The TEA CO2 laser was irradiated on the surface of the rat mandibular bone under the following irradiation conditions: wavelength, 10.6 microns; output, 95 mJ/pulse; pulse repetition rate, 1 Hz; irradiation time, 7.5 microseconds/shot; spot size, 0.8 x 1.5 mm; energy density, 7.9 J/cm2. Histological and scanning electron microscopic examinations were performed.

RESULTS

In the stereoscopic examination, a defect with clean-cut margins was produced. In the light microscopic examination, a basophilic line at the bottom of the defect was noted. Examining the defect with SEM, a smear-like appearance and cone structures were found. In the histological examination, a healing process by formation of new bones at the junction site was recognized.

CONCLUSIONS

These findings suggest that it is possible to remove bone tissues by TEA CO2 laser irradiation. However, a particle-like structure associated with a basophilic line and melted surface indicated that some thermal damage was produced during the laser irradiation.

Ablation depths and morphological changes in human enamel and dentin after Er:YAG laser irradiation with or without water mist

OBJECTIVE

This investigation was performed quantitatively to determine the ranges of ablation and to evaluate the morphological changes in human enamel and dentin irradiated by Er:YAG laser with or without water mist.

SUMMARY BACKGROUND DATA

Recently, several infrared lasers have been introduced in the dental clinic to remove carious dental hard tissues in anticipation of replacing the high-speed dental drill. Among them, the Er:YAG laser has shown the most promise for hard tissue ablation.

METHODS

An Er:YAG laser was used to ablate human dental hard tissues using a pulse energy that ranged from 100 to 400 mJ at a frequency of 2 Hz for 5 seconds. Ablation rates with or without water mist at different pulse energies were measured, and the morphological changes on enamel and dentin were also investigated by stereomicroscopy and scanning electron microscopy (SEM).

RESULTS

The relationship between ablation depths and energies was almost linear at both enamel and dentin samples. The irradiation with water mist reduced the ablation depths, but only minimally, when compared to those irradiated without water mist. Morphological findings by SEM indicated that Er:YAG laser irradiation with water mist could produce the cavities without signs of thermal damage to the surrounding enamel and dentin.

CONCLUSIONS

The results of this study suggest that addition of a fine water mist directed at the ablation sites does not greatly decrease the ablation, and does not cause any carbonization and melting in the surrounding dental hard tissues.

Study of microleakage at Class I cavities prepared by Er:YAG laser using three types of restorative materials

OBJECTIVE

The purpose of this in vitro study were to investigate microleakage at class I cavities filled with amalgam, composite resin, or glass-ionomer after preparation by Er:YAG laser and to compare the results with those by a conventional method using an air turbine.

SUMMARY BACKGROUND DATA

There has been no report of a study of microleakage on class I cavities prepared by Er:YAG laser.

METHODS

Ninety-six extracted human premolar and molar teeth were used in this study. Forty-eight class I cavities were prepared by Er:YAG laser and 48 class I cavities by air turbine. After preparation, each of the 2 groups was further subdivided into 3 groups, respectively, and cavities in each of these subgroups were filled by 1 of 3 types of restorative materials. Microleakage at the restored cavities was assessed by the dye penetration method and scanning electron microscopy (SEM).

RESULTS

Minimal or moderate leakage was evident at most of the composite resin or glass-ionomer restorations, whereas moderate or severe leakage was observed at most of the amalgam restorations as shown by the dye penetration method. There was significant difference among the 3 restorative materials (p < 0.05), but there was no significant difference in microleakage between the cavities prepared by Er:YAG laser and those by air turbine (p > 0.05). SEM evaluation demonstrated good adaptation with most of the composite resin or glass-ionomer restorations, but amalgam restorations showed slightly poorer adaptation.

CONCLUSION

These results suggest that Er:YAG laser is useful for class I cavity preparation from the viewpoint of microleakage.

The effect of parafunction on condylar asymmetry in patients with temporomandibular disorders

This study was undertaken to examine the relationship between condylar asymmetry and parafunction in patients with temporomandibular disorders (TMD). Twenty-eight patients with TMD and parafunction and 30 patients with TMD but no parafunction were examined. A panoramic radiograph was obtained for each patient and from this the condylar asymmetry determined. The group with parafunction showed a significantly (P < 0.005) higher asymmetry index than did the group with no noticeable parafunction. Patients were grouped into the following age ranges: 10-19 years, 20-29 years, 30-39 years, and 40 + years. The mean asymmetry index was determined for each age range for both groups of patients. The group of patients with TMD and parafunction had a higher mean asymmetry index in all the age ranges studied. This suggests that muscle hyperactivity may be a factor in the increased asymmetry found in patients with TMD.

A study on microleakage after resin filling of Class V cavities prepared by Er:YAG laser

OBJECTIVE

The aims of this study were to investigate microleakage after composite resin filling to class V cavities prepared by Er:YAG laser and to compare the results with those obtained by a conventional method using an air turbine in vitro.

SUMMARY BACKGROUND DATA

There has been no report of the microleakage study on class V cavities prepared by Er:YAG laser.

METHODS

Forty-eight human extracted single root teeth were used in this study. Teeth were divided into three groups of sixteen each and class V cavities of the same size were prepared by Er:YAG laser for two groups and by air turbine for one group (control). For one group prepared by Er:YAG laser and the control group, the teeth were treated with 30% phosphoric acid. After the cavities were filled with the composite resin, the teeth except the areas of cavities and margins were covered by nail varnish and dye penetration was performed under the 0.6% Rhodamine B at 36 degrees C for 48 hrs. The teeth were sectioned at a thickness of 2 mm transversally and the slices were evaluated by stereoscopy and scanning electron microscopy (SEM).

RESULTS

Microleakage at the cavity margins was observed in all three groups using the dye penetration method, but there was no significant difference among the three groups. SEM results showed similar results with the dye penetration method.

CONCLUSION

These results suggest that microleakage at the cavities prepared by Er:YAG laser is at the same level as for prepared by air turbine using dye penetration and SEM methods.

Mandibular condyles and rami are asymmetric structures

The purpose of this study was to determine the degree of bony asymmetry between the right (R) and left (L) mandibular condyles and rami. On 25 dry skulls, condylar height, breadth and length, as well as ramus height and breadth were assessed. On each skull the average of the three measurements on the right and left sides, respectively, were calculated with the corresponding reference points being redetermined for each measurement. The raw absolute differences magnitude of R - L as well as the relative absolute differences magnitude of R - L/R + L were computed. The relative absolute differences showed that asymmetries were of similar magnitude (between 1.20% and 2.58%) for all variables except for condylar height (11.06%). After taking three additional measurements with reference points chosen only once, the intra-individual measurement error, consisting of reproducibility of the reference points and accuracy in measuring the distance between the chosen points, was assessed with the help of a statistical variance component technique. Estimates of the 95% range of the absolute differences were computed. Between 60% and 88% of the measured differences were outside the predicted 95% range, thus much too large to be explained by random measurement error; hence, they were due to real individual asymmetries. We concluded that asymmetries of mandibular condyles and rami are part of the biologic variation of humans. It still remains unclear, however, when such asymmetries should be considered "unphysiological."

Temporomandibular joint dysfunction in children

Sixteen pediatric patients with temporomandibular joint (TMJ) dysfunction were successfully diagnosed following appropriately selected imaging methods. The role of radiography in diagnosis of TMJ dysfunction is essential in distinguishing between the osteogenic and non-osteogenic etiologies. Computed tomography (CT) was found to be a valuable imaging method, with advantages over plain film radiography. The treatment modalities considered were: non-invasive therapy, occlusal therapy and surgical treatment. The treatment of choice was dependent on the osteogenic or non-osteogenic etiology. Surgery was considered only when the non-invasive or occlusal therapies were ineffective.

Determining mandibular condyle and ramus height with the help of an Orthopantomogram--a valid method?

The asymmetry of condylar and rami heights was determined from orthopantomograms of 25 macerated skulls and compared with the results of the 'true' values obtained by direct measurements of the skulls. The correlation between the two measuring methods was low.

The condylar asymmetry-age relationship in determining myogenous or arthrogenous origin of pain in patients with temporomandibular disorders

The relation of age to asymmetry index of the condyles of the temporomandibular joint differs for groups of patients with a myogenous and arthrogenous origin of pain. It was decided to investigate if this has clinical diagnostic significance. Twenty-eight patients complaining of temporomandibular disorders (TMD) were included in this study. All were dentate with a maximum of five missing teeth including third molars allowed. Condylar asymmetry was measured according to the method of Habets, and this was used to compute the expected patient age for both curves. The patient was assigned to the group with computed age closest to true age. The association between category derived from graphs and that from clinical diagnosis was studied. There was agreement clinically and graphically in 25 of 28 patients. The Kappa statistic to explore the agreement between the two methods gave a value of 0.78, which allows rejection of the hypothesis that agreement was based on chance alone.

Vertical asymmetry of the mandibular ramus and condylar heights measured with a new method from dental panoramic radiographs in patients with psoriatic arthritis

Vertical asymmetry of the mandibular ramus and condylar heights was measured with a new method from dental panoramic radiographs. The study groups consisted of 45 psoriatic arthritis (PA) and 45 control (CO) matched pairs. Vertical asymmetry was calculated with the formula (R - L)/(R + L) x 100. Females showed no statistical significant difference in vertical asymmetry between the PA and CO pairs. In males however, vertical asymmetry showed a statistically significant difference between the PA and CO groups among those aged 35-55 years (P = 0.008). This group included four men with arthritis mutilans, a severe form of psoriatic arthritis.

The relation of age and handedness to condylar asymmetry in a group of edentulous patients with a temporomandibular disorder of arthrogenous origin

A group of edentulous patients with a temporomandibular disorder of arthrogenous origin was found to have a mean asymmetry index of 7.38%. This was lower than a group with a disorder of myogenous origin, but higher than a control group of non-patients. A graph of age vs. asymmetry index showed no correlation, in keeping with similar results found in a group of patients with a disorder of myogenous origin.

Condylar asymmetry and its relation to age in a group of patients with a craniomandibular disorder of myogenous origin

A group of patients with a myogenous origin of craniomandibular disorders was found to show a variation of condylar asymmetry with age. The curve obtained by plotting patient age against their asymmetry index was parabolic in nature. This differed from a group of patients with an arthrogenous origin of pain, where a linear correlation with age, with a negative slope, had previously been found. The mean asymmetry index for this group of patients was found to be 23.77%. This is higher than that reported for a group of patients with a craniomandibular disorder of arthrogenous origin, namely 18.76%. It appears that these two groups differ in the variation of condylar asymmetry with age..

Variation of condylar asymmetry with age in edentulous patients with a craniomandibular disorder of myogenous origin

The effect of age on condylar asymmetry in dentate patients has already been investigated and a clear relationship between these two variables was established both for a group with an arthrogenous origin and with myogenous origin of pain. In this study, the mean asymmetry index for an edentulous group of patients with a craniomandibular disorder of myogenous origin was found to be 12.55%, less than that for both dentate groups. There appeared to be no correlation between age and the asymmetry index in this group, suggesting that different mechanisms may be at work in the development of these disorders.

Annual review of selected dental literature: report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The annual review of selected dental literature this year cites 384 published papers and reports. This year's review contains more editorial comment than reviews of years passed. New data on the biological responses to materials is emphasized in several sections. Observations on new compounds able to prevent plaque formation are presented. Clinically relevant advances in knowledge concerning the etching of different tooth structures are reported along with the effect of etching procedures on the dental pulp. Evaluation of periodontal diseases in all age groups is a topic. Limitations of current diagnostic techniques in periodontal disease, temporomandibular disorders, and implant therapy are included. There are new views on the use of dental amalgam. The future use of dental mercury is predicted. Interest in new ceramic systems is indicated as the demand for esthetics continues. Clinical information is emphasized over scientific information throughout this year's review.