The effect of inter-implant distance on the height of inter-implant bone crest

BACKGROUND

The biologic width around implants has been well documented in the literature. Once an implant is uncovered, vertical bone loss of 1.5 to 2 mm is evidenced apical to the newly established implant-abutment interface. The purpose of this study was to evaluate the lateral dimension of the bone loss at the implant-abutment interface and to determine if this lateral dimension has an effect on the height of the crest of bone between adjacent implants separated by different distances.

METHODS

Radiographic measurements were taken in 36 patients who had 2 adjacent implants present. Lateral bone loss was measured from the crest of bone to the implant surface. In addition, the crestal bone loss was also measured from a line drawn between the tops of the adjacent implants. The data were divided into 2 groups, based on the inter-implant distance at the implant shoulder.

RESULTS

The results demonstrated that the lateral bone loss was 1.34 mm from the mesial implant shoulder and 1.40 mm from the distal implant shoulder between the adjacent implants. In addition, the crestal bone loss for implants with a greater than 3 mm distance between them was 0.45 mm, while the implants that had a distance of 3 mm or less between them had a crestal bone loss of 1.04 mm.

CONCLUSIONS

This study demonstrates that there is a lateral component to the bone loss around implants in addition to the more commonly discussed vertical component. The clinical significance of this phenomenon is that the increased crestal bone loss would result in an increase in the distance between the base of the contact point of the adjacent crowns and the crest of bone. This could determine whether the papilla was present or absent between 2 implants as has previously been reported between 2 teeth. Selective utilization of implants with a smaller diameter at the implant-abutment interface may be beneficial when multiple implants are to be placed in the esthetic zone so that a minimum of 3 mm of bone can be retained between them at the implant-abutment level.

The radiological prediction of inferior alveolar nerve injury during third molar surgery

The surgical removal of an impacted mandibular third molar may result in damage to the inferior alveolar nerve and may cause disabling anaesthesia of the lip; anaesthesia of the lower gingivae and anterior teeth may also result. Assessing the likelihood of injury depends to a great extent on preoperative radiographic examination. Seven radiological diagnostic signs have been mentioned in the literature; the reliability of these signs as predictors of likely nerve injury have been evaluated through retrospective and prospective surveys. Three signs were found to be significantly related to nerve injury and a further two were probably important clinically.

Ridge alterations post-extraction in the esthetic zone: a 3D analysis with CBCT

Dimensional alterations of the facial bone wall following tooth extractions in the esthetic zone have a profound effect on treatment outcomes. This prospective study in 39 patients is the first to investigate three-dimensional (3D) alterations of facial bone in the esthetic zone during the initial 8 wks following flapless tooth extraction. A novel 3D analysis was carried out, based on 2 consecutive cone beam computed tomographies (CBCTs). A risk zone for significant bone resorption was identified in central areas, whereas proximal areas yielded only minor changes. Correlation analysis identified a facial bone wall thickness of ≤ 1 mm as a critical factor associated with the extent of bone resorption. Thin-wall phenotypes displayed pronounced vertical bone resorption, with a median bone loss of 7.5 mm, as compared with thick-wall phenotypes, which decreased by only 1.1 mm. For the first time, 3D analysis has allowed for documentation of dimensional alterations of the facial bone wall in the esthetic zone of humans following extraction. It also characterized a risk zone prone to pronounced bone resorption in thin-wall phenotypes. Vertical bone loss was 3.5 times more severe than findings reported in the existing literature.

Bone classification: an objective scale of bone density using the computerized tomography scan

Dental implants are subject to masticatory loads of varying magnitude. Implant performance is closely related to load transmission at the bone-to-implant interface where bone quality will be highly variable. The type and architecture of bone is known to influence its load bearing capacity and it has been demonstrated that poorer quality bone is associated with higher failure rates. To date, bone classifications have only provided rough subjective methods for pre-operative assessment, which can prove unreliable. The results of an extensive analysis of computerized tomography scans using Simplant software (Columbia Scientific Inc., Columbia, MD, USA) demonstrate that an objective scale of bone density based on the Houndsfield scale, can be established and that there is a strong correlation between bone density value and subjective quality score (P = 0.002) as well as between the bone density score and the region of the mouth (P < 0.001).

Clinical and radiographic evaluation of the papilla level adjacent to single-tooth dental implants. A retrospective study in the maxillary anterior region

BACKGROUND

The regeneration of gingival papillae after single-implant treatment is an area of current investigation. This study was designed to determine: 1) whether the distance from the base of the contact point to the crest of the bone would correlate with the presence or absence of interproximal papillae adjacent to single-tooth implants, and 2) whether the surgical technique at uncovering influences the outcome.

METHODS

A clinical and radiographic retrospective evaluation of the papilla level around single dental implants and their adjacent teeth was performed in the anterior maxilla in 26 patients restored with 27 implants. Six months after insertion, 17 implants were uncovered with a standard technique, while 10 implants were uncovered with a technique designed to generate papilla-like formation around dental implants. Fifty-two papillae were available for clinical and radiographic evaluation. The presence or absence of papillae was determined, and the effects of the following variables were analyzed: the influence of the 2 surgical techniques; the vertical relation between the papilla height and the crest of bone between the implant and adjacent teeth; the vertical relation between the papilla level and the contact point between the crowns of the teeth and the implant; and the distance from the contact point to the crest of bone.

RESULTS

When the measurement from the contact point to the crest of bone was 5 mm or less, the papilla was present almost 100% of the time. When the distance was > or = 6 mm, the papilla was present 50% of the time or less. The mean distance between the crest of bone and the most coronal papilla level (interproximal soft tissue height) was 3.85 mm (SD = 1.04). When comparing the conventional and modified surgical technique, the relation shifted from 3.77 mm (SD = 1.01) to 4.01 mm (SD = 1.10), respectively.

CONCLUSIONS

These results clearly show the influence of the bone crest on the presence or absence of papillae between implants and adjacent teeth. The data also show a positive influence for the modified surgical technique, aimed at reconstructing papillae at the implant uncovering.

Radiographic examination of ectopically erupting maxillary canines

This study analyzes the need for and possibility of obtaining further information from different radiographic procedures in 125 children with potential ectopic eruption of the maxillary canines. After clinical examination of 3,000 10 to 15-year-old children, it was found that 7% needed radiographic examinations for determination of the canine position. Eighty-four children (2.8%), with a total of 125 potential ectopically erupting maxillary canines diagnosed clinically and by means of periapical radiographs, were selected and a stepwise extended radiographic diagnostic procedure was used. Most canines in ectopic eruption were positioned palatally; the positions could be assessed with sufficient accuracy from conventional periapical films in 92% of the cases. Only in 37% of the cases, however, could the lateral incisor be projected free from the ectopic canine by the intraoral technique. The lamina dura of the lateral incisor facing the canine was often found to be interrupted. For 29% of the ectopic canines, the lateral incisors could neither be projected free nor judged free from resorptions and a supplementary polytomographic investigation was believed to be necessary. The number of resorbed teeth was doubled by polytomography and altogether 12.5% of the ectopic canines caused resorptions. A stepwise radiographic procedure including polytomography is described and recommended in cases of ectopic eruption of maxillary canines for determining the correct position and ruling out or confirming resorptions on incisors, thereby optimizing the orthodontic treatment planning.

Crestal bone changes around titanium implants. A radiographic evaluation of unloaded nonsubmerged and submerged implants in the canine mandible

Current implant placement utilizes both nonsubmerged and submerged techniques. However, the implications of the location of a rough/smooth implant interface as well as the location of a microgap between implant and abutment on crestal bone changes are not well understood. The purpose of this study was to radiographically evaluate crestal bone changes around unloaded nonsubmerged and submerged titanium implants in a side-by-side comparison. Fifty-nine (59) implants were placed at different levels to the alveolar crest in 5 foxhounds. Standardized radiographs were taken at baseline and at monthly intervals until sacrifice at 6 months. Radiographic assessment was carried out by measuring the distance between the top of the implant/abutment and the most coronal bone-to-implant contact (DIB), and by evaluation of bone density changes using computer-assisted densitometric image analysis (CADIA). DIB measurements revealed that in 1-part, nonsubmerged implants, the most coronal bone-to-implant contact followed at all time points the rough/smooth implant interface. In all 2-part implants, nonsubmerged and submerged, the most coronal bone-to-implant contact was consistently located approximately 2 mm below the microgap. In addition, CADIA values for all 2-part implants were decreased in the most coronal area-of-interest (AOI). All bone changes were statistically significant and detectable 1 month after implant placement in nonsubmerged implants or 1 month after abutment connection in submerged implants. Neither implant position nor individual dog effects were statistically significant. These results demonstrate that the rough/smooth implant interface as well as the location of the microgap have a significant effect on marginal bone formation as evaluated by standardized longitudinal radiography. Bone remodeling occurs rapidly during the early healing phase after implant placement for non-submerged implants and after abutment connection for submerged implants.

Reconstruction of alveolar jaw bone. An experimental and clinical study of immediate and preformed autologous bone grafts in combination with osseointegrated implants

In edentulousness, which cannot be adequately compensated for by a denture but causes considerable oral dysfunction, the treatment of choice is a bridge construction on osseointegrated titanium fixtures. In those cases, where the quantity or quality of the alveolar ridge--as a consequence of progressing resorption--does not provide enough bone tissue for lasting implant anchorage, restoration of jaw bone anatomy is required. In attempts to evaluate the best material and method for bone reconstruction in these cases, experimental and clinical studies on various grafting procedures were performed. The immediate, autologous cancellous bone and marrow graft was not found to provide volume restitution to the required extent because of rapid graft resorption. The biomechanical capacities of the jaw bone were, however, restored to such a degree that fixtures could be integrated and permanent bridge stability achieved in 13 out of 18 cases. In order to avoid resorptive derangement of the anatomy of the reconstructed alveolar region a modified transplantation technique was developed. In an experimental study in dogs a procedure of preformation of autologous composite bone grafts containing integrated titanium implants was designed. The results indicated that this procedure could provide graft persistance together with implant stability. Clinical applications of this reconstructive procedure showed that preformed grafts containing incorporated implants from the proximal tibial metaphysis could be used to restore jaw bone anatomy and that the implants remained integrated within the transplanted, remodelled bone, providing permanent support for bridge constructions.

De novo bone induction by recombinant human bone morphogenetic protein-2 (rhBMP-2) in maxillary sinus floor augmentation

PURPOSE

This phase II study was designed to evaluate 2 concentrations of recombinant human bone morphogenetic protein-2 (rhBMP-2) for safety and efficacy in inducing adequate bone for endosseous dental implant in patients requiring staged maxillary sinus floor augmentation.

MATERIALS AND METHODS

Patients were treated with rhBMP-2 (via an absorbable collagen sponge [ACS]), at concentrations of 0.75 mg/mL (n = 18), 1.50 mg/mL (n = 17), or with bone graft (n = 13). Bone induction was assessed by alveolar ridge height, width, and density measurements from computed tomography scans obtained before and 4 months after treatment and 6 months post-functional loading of dental implants (density only).

RESULTS

Mean increases in alveolar ridge height at 4 months after treatment were similar among the groups; 11.3 mm, 9.5 mm, and 10.2 mm, respectively, in the bone graft, 0.75 mg/mL, and 1.50 mg/mL rhBMP-2/ACS treatment groups. Mean increases in alveolar ridge width (buccal to lingual) at the crest of the ridge were statistically different among the treatment groups; 4.7 mm, 2.0 mm, and 2.0 mm, respectively, in the bone graft, 0.75 mg/mL, and 1.50 mg/mL treatment groups (P <or= .01 vs 0.75 mg/mL; P < .01 vs 1.50 mg/mL). At 4 months postoperative new bone density was statistically different among the treatment groups; 350 mg/cc, 84 mg/cc, and 134 mg/cc for the bone graft, 0.75 mg/mL, and 1.50 mg/mL rhBMP-2/ACS treatment groups, respectively (P = .003 vs 0.75 mg/mL, P = .0137 vs 1.50 mg/mL, P = .0188; 1.50 mg/mL vs 0.75 mg/mL). Core bone biopsies obtained at the time of dental implant placement confirmed normal bone formation. The proportion of patients who received dental implants that were functionally loaded and remained functional at 36 months post-functional loading was 62%, 67%, and 76% in the bone graft, 0.75 mg/mL, and 1.50 mg/mL rhBMP-2/ACS treatment groups, respectively.

CONCLUSION

This study is the first randomized controlled trial demonstrating de novo organ tissue growth in humans from a recombinant human protein. rhBMP-2/ACS safely induced adequate bone for the placement and functional loading of endosseous dental implants in patients requiring staged maxillary sinus floor augmentation.

Horizontal ridge augmentation using autogenous block grafts and the guided bone regeneration technique with collagen membranes: a clinical study with 42 patients

OBJECTIVE

To analyze the clinical outcome of horizontal ridge augmentation using autogenous block grafts covered with an organic bovine bone mineral (ABBM) and a bioabsorbable collagen membrane.

MATERIAL AND METHODS

In 42 patients with severe horizontal bone atrophy, a staged approach was chosen for implant placement following horizontal ridge augmentation. A block graft was harvested from the symphysis or retromolar area, and secured to the recipient site with fixation screws. The width of the ridge was measured before and after horizontal ridge augmentation. The block graft was subsequently covered with ABBM and a collagen membrane. Following a tension-free primary wound closure and a mean healing period of 5.8 months, the sites were re-entered, and the crest width was re-assessed prior to implant placement.

RESULTS

Fifty-eight sites were augmented, including 41 sites located in the anterior maxilla. The mean initial crest width measured 3.06 mm. At re-entry, the mean width of the ridge was 7.66 mm, with a calculated mean gain of horizontal bone thickness of 4.6 mm (range 2-7 mm). Only minor surface resorption of 0.36 mm was observed from augmentation to re-entry.

CONCLUSIONS

The presented technique of ridge augmentation using autogenous block grafts with ABBM filler and collagen membrane coverage demonstrated successful horizontal ridge augmentation with high predictability. The surgical method has been further simplified by using a resorbable membrane. The hydrophilic membrane was easy to apply, and did not cause wound infection in the rare instance of membrane exposure.

Root proximity is a major factor for screw failure in orthodontic anchorage

INTRODUCTION

The purpose of this study was to evaluate root proximity as a risk factor for the failure of miniscrews used as orthodontic anchorage.

METHODS

We used dental radiographs and 3-dimensional computed tomography images to examine 216 titanium screws in 110 patients. Each screw was classified according to its proximity to the adjacent root. Category I, the screw was absolutely separate from the root; category II, the apex of the screw appeared to touch the lamina dura; and category III, the body of the screw was overlaid on the lamina dura. If the orthodontic force could be applied to the screw for 1 year (or until completion of orthodontic treatment), we recorded the screw anchorage as a success.

RESULTS

The screws had a high success rate--above 80%. Screws placed in the maxilla had a significantly higher success rate than those in the mandible. There was a significant correlation between success rate and root proximity. There were significant differences in the success rates between categories I and II, I and III, and II and III. Although screws in all 3 categories in the maxilla and categories I and II in the mandible showed high success rates above 75%, screws in category III in the mandible had a low success rate of 35%.

CONCLUSIONS

The proximity of a miniscrew to the root is a major risk factor for the failure of screw anchorage. This tendency is more obvious in the mandible.

Current Products and Practice

There has been an escalating interest in three-dimensional imaging devices over the last decade. Orthodontists are beginning to appreciate the advantages that the third dimension gives to clinical diagnosis, treatment planning and patient education. This article focuses on the cutting edge technology of cone beam CT, which utilizes conventional X-ray technology and computerized volumetric reconstruction to reproduce a three-dimensional image. A variety of applications and range of issues associated with this technology will be discussed.

Diagnosis and possible causes of vertical root fractures

Thirty-two cases of vertical fractures were studied in an attempt to identify the causes and diagnostic signs normally present. In all of the patients except two, osseous defects were present and could be probed. The majortiy (65.63 percent) had only mild pain or a dull discomfort. Seventy-five percent showed diffuse widening of the periodontal ligament space. This study suggests that excessive force during lateral condensation of the gutta-percha caused 84.38 percent of the fractures. A secondary cause was the forcing or tapping of inlays or dowels into place. The majority (78.13 percent) of the patients were over the age of 40. In all but nine of the cases, treatment consisted of the extraction of the involved teeth.

Long-term evaluation of osseointegrated implants inserted at the time or after vertical ridge augmentation. A retrospective study on 123 implants with 1-5 year follow-up

The purpose of the present study was to evaluate retrospectively, after 1 to 5 years of prosthetic loading, 123 implants consecutively inserted at the time of vertical ridge augmentation in 4 clinics. At the time of the implant surgery, 3 different techniques were used: the implants were allowed to protrude 2 to 7 mm from the bone level and a titanium reinforced expanded-polytetrafluoroethylene (e-PTFE) membrane was positioned to protect either the blood clot (Group A, 6 patients), or an allograft (Group B, 11 patients), or an autograft (Group C, 32 patients). The annual implant evaluation was carried out according to a standard protocol utilized for long term studies with endosseous implants inserted in non-regenerated bone. Only 1 implant failed immediately after the second stage surgery and after 1 month it was substituted with a new implant. All the remaining implants appeared clinically stable, no signs of radiolucency were present at the bone-implant interface, therefore, they could be defined successfully osseointegrated. The radiographic analysis showed stable bone crest levels with a mean bone loss of 1.35 mm for the Group A, of 1.87 mm for the Group B and of 1.71 for the Group C during the period of observation. Only 2 implants demonstrated an increased crestal bone loss of 3.5 mm and 4 mm respectively at the first year examination. On the base of these results, we can confirm previous long term studies on regenerated bone and we can conclude that vertically augmented bone with GBR techniques responds to implant placement like native, non-regenerated bone.

A retrospective study of 236 patients with teeth restored by carbon fiber-reinforced epoxy resin posts

STATEMENT OF PROBLEM

The Composipost dowel is made of stretched, aligned carbon fibres embedded in an epoxy-resin matrix. It is widely used in Europe and Canada for the restoration of endodontically treated teeth and was introduced in the United States 2 years ago as the C-Post dowel.

PURPOSE

This retrospective study evaluated treatment outcome of the Composipost system after 2 to 3 years.

MATERIAL AND METHODS

A total of 236 patients treated during a 1-year period by seven Swedish dental practitioners were included. Of those, 146 patients consented and data were collected from the dental records of the remaining patients. Thus, the material comprised 236 teeth restored with carbon fiber-reinforced epoxy resin post, 130 maxillary and 106 mandibular teeth, with a mean restoration time of 32 months (range 27 to 41). Periodontal conditions, radiographic signs, and prosthodontic results were recorded.

RESULTS

Five teeth (2%) had been extracted for reasons unrelated to the Composipost system. Periodontal conditions such as plaque accumulation, gingival health, bleeding on probing, and pocket depth around the teeth with Composipost dowels were similar to the control teeth. No dislodgment or root or post fractures were observed clinically or on radiographs. Radiographic examination of bone height measured from the apex to the bone margin mesially and distally showed differences on the mesial side but not on the distal surface (p < 0.05) between the Composipost-treated teeth and the controls.

CONCLUSIONS

Promising results after 2 to 3 years of clinical service indicate that this system can be a viable alternative to conventional post-and-core systems.

A 10-year retrospective study of periodontal disease progression

The purpose of this study was to record the rate of periodontal disease progression over a 10-year period with respect to individual subject, age and tooth type. 283 subjects, who had undergone a full-mouth radiographic examination in 1974-76 and at that time were 25-70 years old, were randomly selected from a larger patient sample for a new radiographic examination in 1985-86. 201 subjects (71%) agreed to participate. For each respondent, tooth loss over the 10-year period was calculated. The radiographic bone height at the mesial and distal aspect of all teeth was assessed by measuring the distance between the cemento-enamel junction and the bone crest. Difference in periodontal bone height between the 2 examinations was calculated for each tooth site. The results revealed that the mean number of teeth lost over the 10-year period was 3.8 (SD 4.6). Tooth mortality, expressed as a % of the no. of teeth present at the initial examination, increased with age and varied between 2.9%-28.5%. In all age groups, molars had the highest and canines the lowest rate of tooth mortality. The frequency of subjects with loss of greater than 10 teeth was highest for the initially 45-year old individuals (20%). 7 individuals (3%) had become edentulous. The mean annual reduction of alveolar bone height varied between 0.07-0.14 mm in the age groups 25-65 years. The initially 70-year old subjects showed a statistically significant higher annual rate of bone loss (0.28 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

Cigarette smoking and periodontal bone loss

The association between smoking and loss of periodontal bone height was investigated in Swedish dental hygienists. The study group included 210 subjects: 24 to 60 years of age, 30% smokers, 32% former smokers, and 38% non-smokers. The study was based on bite-wing radiographs, where loss of the interproximal bone height was measured as the distance from the cemento-enamel junction (CEJ) to the interdental septum (IS). The magnitude of the CEJ-IS distance was read at 12 sites, representing 3 maxillary and 3 mandibular bone septa in each subject. The CEJ-IS distance was significantly greater for smokers when compared to non-smokers, mean +/- SEM 1.71 +/- 0.08 mm and 1.45 +/- 0.04 mm, respectively. The mean +/- SEM for former smokers was 1.55 +/- 0.05 mm. In smokers, the CEJ-IS distance increased with increased smoking exposure. The results, based on adults with good oral hygiene, suggest that loss of periodontal bone is related to smoking. The smoking related bone loss is not correlated with plaque infection.

Untreated periodontal disease: a longitudinal study

Thirty diagnosed but untreated patients with moderate to advanced periodontal disease were examined a minimum of two times. The examination time intervals ranged between 18 and 115 months. 2. A total of 83 teeth were lost between examinations. 3. Excluding a patient who lost 25 teeth, a total of 58 teeth were lost. The adjusted tooth loss was 0.61 tooth per patient per year (or 0.36 with the elimination of 22 "hopeless" teeth). 4. The mandibular and maxillary molars had the greatest percentage of tooth loss between examinations. 5. All 29 patients completing the study had progessive increases in pocket depth during their time in the study. Increases in the mean annual pocket depths per tooth per patient varied from 0.24 millimeter per year to 2.46 millimeters per year. 6. The disto-lingual and mesio-lingual interproximal surfaces had the greatest increases in surface pocket depths. The lingual and buccal surfaces had the smallest increases in pocket depth. 7. The rate of increase in pocket depths was less in patients over 44 years of age. 8. The teeth which were lost had greater initial pocket depths and mobility scores than those which were present at both examinations. 9. There was no correlation between increases in pocket depth and changes in mobility. 10. All 29 patients showed radiographic evidence of progressive bone resorption between examinations. The posterior segments of the mouth had the largest amounts of bone loss between the first and last examinations.

Hydroxylapatite as an alloplastic graft in the treatment of human periodontal osseous defects

Twelve patients, 32 to 60 years of age, received a polycrystalline ceramic form of pure dense hydroxylapatite as an alloplastic bone implant material in intrabony defects following reflection of full mucoperiosteal flaps, root planing and defect-curettement. The defects were measured from an acrylic stent, using an endodontic silver point which was placed to the base of the defect. Similarly, debrided and curetted defects in the same patients were not implanted and served as controls. Recalls for documentation and plaque control were at 1, 2, and 4 weeks, and at 3, 6 and 9 months. Measurements relating to changes in defect-depth were made upon reentry at 9 months. The twelve defects, serving as controls, showed very little difference between the pretherapy and 9-month measurements. The initial mean measurement from the base of the defect to the highest alveolar crest was 4.27 mm and the 9-month mean measurement after curettage only was 3.36 mm. In terms of resolution of the original defect this amounted to 19.49% reduction, but a 0.46-mm mean loss in height of the alveolar crest provided an actual percentage fill of the original defect of 9.91%. Of sixteen experimental defects, the same initial mean measurement from the base of the defect to the highest alveolar crest was 5.18 mm and the 9-month mean measurement after grafting was 2.43 mm. In terms of resolution of the original defect, this amounted to a 53.57% reduction, but in contradistinction to the curettage sites, a mean increase in height of the highest alveolar crest of 0.61 mm gave a true percentage fill of the original defect of 66.89%. At the 9-month reentry, the implanted mass seemed to be partially "calcified" and was resistant to penetration with a probe or removal with a curette. The data and clinical impression strongly suggest that hydroxylapatite has a potential as an alloplastic implant with clinically apparent acceptance by the soft and hard tissues.

Tooth-borne vs bone-borne rapid maxillary expanders in late adolescence

OBJECTIVE

To evaluate the immediate effects of rapid maxillary expansion (RME) on the transverse skeletal and dentoalveolar changes with bone-borne (C-expander) and tooth-borne type expanders using cone-beam computed tomography (CBCT) in late adolescents.

MATERIALS AND METHODS

A sample of 28 female late-adolescent patients was divided into two groups according to the type of expander: bone-borne (C-expander, n  =  15, age  =  18.1 ± 4.4 years) and tooth-borne (hyrax, bands on premolars and molars, n  =  13, age  =  17.4 ± 3.4 years). CBCT scans were taken at 0.2-mm voxel size before treatment (T1) and 3 months after RME (T2). Transverse skeletal and dental expansion, alveolar inclination, tooth axis, vertical height of tooth, and buccal dehiscence were evaluated on maxillary premolars and molars. Paired t-test, independent t-test, one-way analysis of variance, and Scheffé post hoc analysis were performed.

RESULTS

The C-expander group produced greater skeletal expansion, except in the region of the first premolar (P < .05 or < .01), which showed slight buccal tipping of the alveolar bone. The Hyrax group had more buccal tipping of the alveolar bone and the tooth axes, except in the region of the second molar (P < .05 or < .01 or < .001). Dental expansion at the apex level was similar in the banded teeth (the first premolar and the first molar). Vertical height changes were apparent on the second premolar in the hyrax group (P < .05 or < .01). Significant buccal dehiscence occurred at the first premolar in the hyrax group (P < .01 or < .001). There were no significant differences between tooth types for any variables in the C-expander group.

CONCLUSIONS

For patients in late adolescence, bone-borne expanders produced greater orthopedic effects and fewer dentoalveolar side effects compared to the hyrax expanders.

The relationship between attachment level loss and alveolar bone loss

Standardized radiographs and repeated periodontal probe measurements were made on 22 untreated subjects with destructive periodontal disease monitored for 1 year. Radiographs of selected sites were taken at 0, 6 and 12 months. Measurements of attachment level were made monthly. Radiographic measurements were made on 7X magnified projected images. Alveolar bone height from the CEJ was computed by multiplying the average length of the root times the measured ratio of CEJ to alveolar bone over CEJ to root tip. Each radiograph was measured twice by 2 investigators. Sites were excluded as having indistinct anatomical landmarks in which the standard deviation of the 4 measurements exceeded 0.16 mm, the measurement error for repeat determination of bone height on high quality radiographic images. A 3 sigma critical value for significant bone loss was selected as 0.48 mm. Changes in attachment level were computed for the intervals preceding and during the 6-12 month radiographic measurement period. Based on these critical values, 6.1% of the 231 radiographed sites showed significant bone loss. Similarly, 5.7% of the 1155 probed sites showed significant attachment loss. However, none of the sites with significant bone loss exhibited significant attachment loss over the same time period. In general, significant attachment loss preceded bone loss by 6 to 8 months. At 4 mm, attachment loss was found to predict subsequent bone loss with a true positive ratio of 60% and a false positive ratio of 5%, indicating a high degree of predictive discrimination. These observations indicate that attachment loss precedes radiographic evidence of crestal alveolar bone loss during periods of periodontal disease activity.

3D-CT evaluation of facial asymmetry

OBJECTIVE

Recently, 3-dimensional-computed tomography (3D-CT) imaging has been used in the diagnosis and surgical treatment planning of patients with craniofacial deformities. The present authors have developed a 3D-CT imaging procedure for a 3-dimensional coordinate point evaluation system to assess and diagnose patients with facial asymmetry.

STUDY DESIGN

The CT data of 16 subjects was selected retrospectively as the control group from patients who had undergone CT examinations to diagnose conditions other than maxillofacial deformities. Anatomical landmarks modified from orthodontic craniometric (cephalometric) points were defined on the 3D-CT images and the asymmetry index of each point was calculated in millimeters. A diagrammatic chart with a baseline indicating the mean asymmetry indices plus the standard deviation in the control group was designed. The resulting diagrammatic chart was used to evaluate the degree of deformity in facial asymmetry patients.

RESULTS AND CONCLUSIONS

The topography of facial asymmetry was assessed. The 3D-CT imaging technique as described herein is a practical method of evaluating the morphology of facial asymmetry.

Three-dimensional micro-computed tomographic imaging of alveolar bone in experimental bone loss or repair

BACKGROUND

Micro-computed tomography (micro-CT) offers significant potential for identifying mineralized structures. However, three-dimensional (3-D) micro-CT of alveolar bone has not been adapted readily for quantification. Moreover, conventional methods are not highly sensitive for analyzing bone loss or bone gain following periodontal disease or reconstructive therapy. The objective of this investigation was to develop a micro-CT methodology for quantifying tooth-supporting alveolar bone in 3-D following experimental preclinical situations of periodontitis or reconstructive therapy.

METHODS

Experimental in vivo bone loss or regeneration situations were developed to validate the micro-CT imaging techniques. Twenty mature Sprague-Dawley rats were divided into two groups: bone loss (Porphyromonas gingivalis lipopolysaccharide-mediated bone resorption) and regenerative therapy. Micro-CT and software digitized specimens were reconstructed three-dimensionally for linear and volumetric parameter assessment of alveolar bone (linear bone height, bone volume, bone volume fraction, bone mineral content, and bone mineral density). Intra- and interexaminer reproducibility and reliability were compared for methodology validation.

RESULTS

The results demonstrated high examiner reproducibility for linear and volumetric parameters with high intraclass correlation coefficient (ICC) and coefficient of variation (CV). The ICC showed that the methodology was highly reliable and reproducible (ICC >0.99; 95% confidence interval, 0.937 to 1.000; CV <1.5%), suggesting that 3-D measurements may provide better alveolar bone analysis than conventional 2-D methods.

CONCLUSIONS

The developed methods allow for highly accurate and reproducible static measurements of tooth-supporting alveolar bone following preclinical situations of bone destruction or regeneration. Future investigations should focus on using in vivo micro-CT imaging for real-time assessments of alveolar bone changes.

A 3-year follow-up study on single implant treatment

The purpose of this study was to investigate restorative and postinsertion problems in patients provided with single implant supported restorations. Fifty consecutive single implant patients were reviewed over a period of 3 years following placement of artificial crowns. One (1.4%) of the 70 inserted implants was lost during the follow-up period, which gives a cumulative success rate of 98.5%. The most frequent complication was loosening of the single tooth abutment screw. This problem was associated with fistulas during the first year of clinical service. A more severe complication was that three adjacent teeth had to be endodontically treated due to accidental devitalization from surgical trauma during implant insertion. The mean marginal bone level adjacent to the implants was reduced 0.5 mm from crown insertion to the third annual review.