Bone-healing pattern at the surface of titanium implants: an experimental study in the dog

OBJECTIVE

To study the early sequential stages of osseointegration at implants installed in alveolar bony.

MATERIALS AND METHODS

In 12 Labrador dogs, all mandibular premolars and first molars were extracted bilaterally. After 3 months of healing, full-thickness flaps were elevated in the edentulous region of the right side of the mandible. Implants were installed, and the flaps were sutured to allow a fully submerged healing. The timing of the installations in the left side of the mandible and of sacrifices were performed with a schedule that various observation periods to sacrifice from 5, 10, 20, and 30 days were available so that n = 6 was obtained per each healing period. Ground sections were prepared and analyzed.

RESULTS

Newly formed bone in contact with the implant surface was found after 10 days of healing and the percentage increased up to 50% after 1 month of healing. A higher percentage was found in the trabecular compared with the cortical bony compartment. Old bone decreased by about 50% during healing, being still present after 1 month (16%). The proportions of bone debris and bone particles were at 27% after 5 days and decreased during healing to 6% after 1 month.

CONCLUSION

Osseointegration (new bone-to-implant contact) developed at various rates for cortical and trabecular compartments, respectively. In the trabecular region, mesenchymal cells were identified, subsequently developing into new bone in contact with the implant surface. In the cortical compartment, however, resorptive processes were observed throughout all periods of healing. The proportion of newly formed bone percentage was lower compared with that of the trabecular area. Old bone was still present after 1 month of healing in both compartments. Bone debris and small bone particles appeared to be involved in initial bone formation.

Osseointegration of implants with dendrimers surface characteristics installed conventionally or with Piezosurgery®. A comparative study in the dog

AIM

The first aim of the present experiment was to compare bone healing at implants installed in recipient sites prepared with conventional drills or a piezoelectric device. The second aim was to compare implant osseointegration onto surfaces with and without dendrimers coatings.

MATERIAL AND METHODS

Six Beagles dogs were used in this study. Five implants with two different surfaces, three with a ZirTi(®) surface (zirconia sand blasted, acid etched), and two with a ZirTi(®)-modified surface with dendrimers of phosphoserine and polylysine were installed in the right side of the mandible. In the most anterior region (P2, P3), two recipient sites were prepared with drills, and one implant ZirTi(®) surface and one coated with dendrimers implants were installed at random. In the posterior region (P4 and M1), three recipient sites were randomly prepared: two sites with a Piezosurgery(®) instrument and one site with drill and two ZirTi(®) surface and one coated with dendrimers implants installed. Three months after the surgery, the animals were sacrificed for histological analysis.

RESULTS

No complications occurred during the healing period. Three implants were found not integrated and were excluded from analysis. However, n = 6 was obtained. The distance IS-B at the buccal aspect was 2.2 ± 0.8 and 1.8 ± 0.5 mm, while IS-C was 1.5 ± 0.9 and 1.4 ± 0.6 mm at the Piezosurgery(®) and drill groups, respectively. Similar values were obtained between the dendrimers-coated and ZirTi(®) surface implants. The BIC% values were higher at the drill (72%) compared to the Piezosurgery(®) (67%) sites. The BIC% were also found to be higher at the ZirTi(®) (74%) compared to the dendrimers-coated (65%) implants, the difference being statistically significant.

CONCLUSION

This study has revealed that oral implants may osseointegrate equally well irrespective of whether their bed was prepared utilizing conventional drills with abundant cooling or Piezosurgery(®). Moreover, the surface coating of implants with dendrimers phosphoserine and polylysine did not improve osseointegration.

Clinical research in implant dentistry: evaluation of implant-supported restorations, aesthetic and patient-reported outcomes

The articles discussed in working group 3 dealt with specific aspects of clinical research. In this context, the literature reporting on survival and complication rates of implant-supported or implant-tooth supported restorations in longitudinal studies of at least 5 years were discussed. The second aspect dealt with the evaluation of aesthetic outcomes in clinical studies and the related index systems available. Finally, the third aspect discussed dealt with patient-reported outcome measures (PROMs). A detailed appraisal of the available methodology was presented.

Complication and failure rates of tooth-supported fixed dental prostheses after 7 to 19 years in function

PURPOSE

The aims of this study were to reexamine patients who had received fixed dental prostheses (FDPs) more than 10 years prior, list the frequencies of observed technical and biologic failures and complications, and calculate the estimated failure and complication rates at 10 and 15 years.

MATERIALS AND METHODS

Fifty-six of 195 patients who were treated by undergraduate students during their state board examinations in fixed prosthodontics between 1990 and 1999 at the School of Dental Medicine, University of Bern, Bern, Switzerland, were recalled successfully.

RESULTS

At reexamination, it was determined that 56 patients with a mean age of 62 years (range: 41 to 85 years) had received 95 metal-ceramic FDPs supported by 202 abutment teeth. Prostheses had been in function for 7 to 19 years (mean: 14 years). The FDPs demonstrated a high estimated survival rate of 90.4% after 10 years and 80.5% after 15 years, although 17 of the 202 abutment teeth had been lost. The probability to remain free from any complication/failure was 79.7% at 10 years and 34.6% at 15 years. The risk of FDPs being affected by a biologic complication or failure after 10 years was 14.9%; the risk was 5.34% for a technical complication or failure. After 15 years, the risks of a biologic or technical complication or failure were 45.7% and 19.7%, respectively.

CONCLUSIONS

The survival rates of FDPs decreased gradually with time. Freedom from complications and failures was drastically decreased for FDPs that had been in function for longer than 10 years.

A systematic review of post-extractional alveolar hard and soft tissue dimensional changes in humans

BACKGROUND

Removal of teeth results in both horizontal and vertical changes of hard and soft tissue dimensions. The magnitude of these changes is important for decision-making and comprehensive treatment planning, with provisions for possible solutions to expected complications during prosthetic rehabilitation.

OBJECTIVES

To review all English dental literature to assess the magnitude of dimensional changes of both the hard and soft tissues of the alveolar ridge up to 12 months following tooth extraction in humans.

METHODS

An electronic MEDLINE and CENTRAL search complemented by manual searching was conducted to identify randomized controlled clinical trials and prospective cohort studies on hard and soft tissue dimensional changes after tooth extraction. Only studies reporting on undisturbed post-extraction dimensional changes relative to a fixed reference point over a clearly stated time period were included. Assessment of the identified studies and data extraction was performed independently by two reviewers. Data collected were reported by descriptive methods. Weighted means and percentages of the dimensional changes over time were calculated where appropriate.

RESULTS

The search provided 3954 titles and 238 abstracts. Full text analysis was performed for 104 articles resulting in 20 studies that met the inclusion criteria. In human hard tissue, horizontal dimensional reduction (3.79 ± 0.23 mm) was more than vertical reduction (1.24 ± 0.11 mm on buccal, 0.84 ± 0.62 mm on mesial and 0.80 ± 0.71 mm on distal sites) at 6 months. Percentage vertical dimensional change was 11-22% at 6 months. Percentage horizontal dimensional change was 32% at 3 months, and 29-63% at 6-7 months. Soft tissue changes demonstrated 0.4-0.5 mm gain of thickness at 6 months on the buccal and lingual aspects. Horizontal dimensional changes of hard and soft tissue (loss of 0.1-6.1 mm) was more substantial than vertical change (loss 0.9 mm to gain 0.4 mm) during observation periods of up to 12 months, when study casts were utilized as a means of documenting the changes.

CONCLUSIONS

Human re-entry studies showed horizontal bone loss of 29-63% and vertical bone loss of 11-22% after 6 months following tooth extraction. These studies demonstrated rapid reductions in the first 3-6 months that was followed by gradual reductions in dimensions thereafter.

Clinical and radiographic changes at implants supporting single-unit crowns (SCs) and fixed dental prostheses (FDPs) with one cantilever extension. A retrospective study

OBJECTIVES

To evaluate the clinical and radiographic changes at implants in posterior maxillary and mandibular areas supporting single-unit crowns (SCs) and fixed dental prostheses (FDPs) with one mesial or distal cantilever extension after an observation period of at least 3 years.

MATERIAL AND METHODS

Seventeen subjects with 19 implant-supported SCs and 21 subjects with 21 implant-supported FDPs fulfilled the inclusion criteria. All FDPs were supported by two implants and had a span of 3-4 units. All reconstructions were incorporated in the posterior maxilla or mandible. The mesial and distal radiographic marginal bone loss from baseline (i.e. delivery of the reconstruction) to the follow-up examination was averaged and compared between SCs supporting one cantilever extension with that of implants supporting FDPs adjacent to or distant from the cantilever extension. Changes in mean pocket probing depth (PPD) were calculated and compared between the three groups.

RESULTS

The mean observation period was 78.2 ± 34.5 months for SCs supported by one implant and 67.8 ± 29.8 months for FDPs supported by two implants. No implant loss occurred, yielding a 100% survival rate. At baseline, the mean radiographic bone levels ± SD were 2.6 ± 0.3 mm for implants supporting SCs, 2.6 ± 0.3 mm for implants of FDPs adjacent to the cantilever extension, and 2.4 ± 0.5 mm for implants of FDPs distant from the cantilever extension. At follow-up, the corresponding mean bone levels ± SD were 2.7 ± 0.4, 2.7 ± 0.5, and 2.8 ± 0.5 mm, respectively. No statistically significant differences (P > 0.05) were observed comparing the mean marginal bone loss between the three groups. Moreover, mean changes in PPD between baseline and follow-up were not statistically significantly different (P > 0.05) between the three groups.

CONCLUSION

The presence of one mesial or distal cantilever extension in the posterior maxilla or mandible does not jeopardize the marginal bone levels of implants supporting SCs or short-span FDPs after a mean observation period of at least 5 years.

Effects of a single topical doxycycline administration adjunctive to mechanical debridement in patients with persistent/recurrent periodontitis but acceptable oral hygiene during supportive periodontal therapy

OBJECTIVES

To evaluate the efficacy of a slow release doxycycline gel (SRD) adjunctively administered to non-surgical therapy in subjects with recurrent or persistent periodontitis but acceptable oral hygiene during supportive periodontal care.

MATERIAL & METHODS

In this single blind, parallel group, multicentre study, 202 of 203 recruited periodontal maintenance subjects with recurrent or persistent periodontitis were randomly assigned to subgingival ultrasonic/sonic instrumentation (USI) with (test) or without (control) subsequent administration of SRD in all residual periodontal pockets ≥4 mm. Intergroup differences in probing depth, BOP reductions, treatment time, probing attachment levels were evaluated at 3, 6 and 12 months. The primary outcome was the inter-group difference in absolute change of probing pocket depth (PPD) 3, 6 and 12 months after intervention.

RESULTS

At baseline, the two groups were comparable. At 3 months, the test group showed a significantly higher decrease in mean probing depth than the control group at 3 months (mean difference = 0.11 mm, 95% CI 0.03-0.19 mm, p = 0.003). Administration of SRD resulted in significantly greater odds of transition of bleeding pockets ≥5 mm to a category of non bleeding sites with PPD ≤4 mm at 3 and 6 months (O.R. = 1.4, 95% CI 1.2-1.8 at 3 months). At 6 months, SRD benefit was observed only in the deeper pockets. 7.5% of subjects (no significant difference between test and control) showed disease progression (attachment loss ≥2 mm) and were exited from the study. No difference in the incidence of adverse events was observed between groups.

CONCLUSION

The trial results show that topically administered SRD may provide short-term benefit in controlling inflammation and deep pockets in treated periodontal patients participating in a secondary prevention programme and able to maintain a satisfactory level of oral hygiene.

Alveolar bony crest preservation at implants installed immediately after tooth extraction: an experimental study in the dog

AIM

To evaluate the influence of deproteinized bovine bone mineral in conjunction with a collagen membrane, at implants installed into sockets in a lingual position immediately after tooth extraction, and presenting initial horizontal residual buccal defects <2 mm.

MATERIAL AND METHODS

The pulp tissue of the mesial roots of (4)P(4) was removed in six Labrador dogs, and the root canals were filled with gutta-percha and cement. Flaps were elevated, and the buccal and lingual alveolar bony plates were exposed. The premolars were hemi-sectioned, and the distal roots were removed. Implants were installed in a lingual position and with the margin flush with the buccal bony crest. After installation, defects resulted at about 1.7 mm in width at the buccal aspects, both at the test and control sites. Only in the left site (test), deproteinized bovine bone mineral (DBBM) particles were placed into the defect concomitantly with the placement of a collagen membrane. A non-submerged healing was allowed.

RESULTS

After 3 months of healing, one implant was found not integrated and was excluded from the analysis together with the contralateral control implant. All remaining implants were integrated into mature bone. The bony crest was located at the same level of the implant shoulder, both at the test and control sites. At the buccal aspect, the most coronal bone-to-implant contact was located at a similar distance from the implant margin at the test (1.7 ± 1.0 mm) and control (1.6 ± 0.8 mm) sites, respectively. Only small residual DBBM particles were found at the test sites.

CONCLUSION

The placement of an implant in a lingual position into a socket immediately after tooth extraction may favor a low exposure of the buccal implant surface. The use of DBBM particles, concomitantly with a collagen membrane, did not additionally improve the outcome obtained at the control sites.

Effectiveness of different interdental brushes on cleaning the interproximal surfaces of teeth and implants: a randomized controlled, double-blind cross-over study

OBJECTIVES

To compare the interproximal cleansing efficacy of the novel, waist-shaped Circum brush (Topcaredent, Switzerland; CB) with that of a straight soft interdental brush (IB) (TePe, Sweden; SB) on posterior surfaces.

MATERIAL & METHODS

Eight patients after completion of initial periodontal therapy abolished oral hygiene for 3 days. Baseline plaque scores (PlI, Silness & Löe ) were assessed on eight surfaces of all premolars and molars. Subsequently, an instructed nurse applied at random one of the two IB, three times per interdental space . Following this, registration of the PlI was repeated by the same blinded examiner. After a 2-week recovery, patients abolished oral hygiene practices for another 3 days. Again, pre-and post-brushing PlI were recorded by the same examiner. The second IB was now applied.

RESULTS

Patient mean PlI and site PlI were evaluated before and after application of the SB or CB respectively. Paired t-tests were performed to yield statistically significant differences. The reduction of biofilm from before to after the use of the IB on a subject basis was highly significant (P < 0.0001). The mean PlI after the use of the CB was significantly lower than after the use of the SB (P < 0.0001). Comparing the PlI of the line angles (MB, ML, DB, DL), significantly more biofilm had been removed by applying CB compared with SB (P < 0.0001). Moreover, comparing the PlI of the buccal (MB, DB) or the lingual line angles (DL, ML) yielded a significantly higher reduction of biofilm in favour of the CB (P < 0.0001). The reduction of the PlI in the mid-interproximal portion, both mesially and distally did not differ significantly between CB and ST. No biofilm reduction was seen on the buccal sites with either IB.

CONCLUSION

The application of the waist-shaped Circum IB resulted in significantly lower PlI scores than the use of a straight IB. This was predominantly due to the higher cleansing effect of the waist-shaped CB on the buccal and lingual line angles.

Osseointegration--communication of cells

BACKGROUND

The article provides the scientific documentation for the 3D animated film - "Osseointegration - Communication of cells".

AIM

The aim of this article and of the film is to visualise the molecular and cellular events during the healing of an osseous wound after installation of a dental implant with special emphasis on the process of osseointegration.

MATERIAL AND RESULTS

In this review article for didactic reasons the concept of the four phases of a healing soft tissue wound was transferred to a bone wound after insertion of a dental implant: haemostasis, inflammatory phase, proliferative phase and remodelling phase. Wound healing throughout these phases is the result of a coordinated action of different cell types which communicate with each other by their interaction using signalling molecules like cytokines, extracellular matrix proteins and small molecules. A regular sequence of cell types controlled by adequate concentrations of signalling molecules results in undisturbed healing. Disturbed healing is associated with a continuation of the early inflammatory phase and the development of a toxic wound environment. The latter is characterized by high counts of polymorphnuclear cells, high concentrations of toxic radicals and proteolytic enzymes and low concentrations of growth factors and extracellular matrix molecules. Clinically the development of a toxic wound environment should be avoided, e.g. by antibacterial measures.

DISCUSSION AND CONCLUSION

Experiencing implant osseointegration as a biological process may provide the clinician new targets to improve the therapy with dental implants.

Does a clinician's sex influence treatment decisions?

PURPOSE

As more women are entering health professions, the health care system is becoming more feminized. This investigation evaluated gender differences in clinicians' treatment preferences and decision making in a complex treatment situation.

MATERIALS AND METHODS

A questionnaire was developed containing clinical cases and statements to assess practitioners' opinions on treatment of periodontally involved maxillary molars and implant therapy with sinus grafting. Data were analyzed with respect to the clinicians' sex, and an overall logistic regression was performed to further investigate possible influences of age, office location, and specialty.

RESULTS

Three hundred forty questionnaires were evaluated (response rate: 35.1%). The mean age of female respondents (37%) was 42 years, and the mean age of male respondents was 46 years. Significantly fewer women reported performing implant placement (35% vs 63%), sinus grafting (16% vs 43%), and periodontal surgery (57% vs 68%). Female practitioners tended to refer more patients to specialists. Participants favored sinus grafting more often for their spouses than for themselves. Apart from a preference for regenerative periodontal surgery among women, no gender differences were observed for treatment decisions or views on general statements related to implant preference, tooth maintenance, or conventional reconstructive therapies.

CONCLUSIONS

With similar expert knowledge, treatment decisions were made irrespective of sex. While the majority of male care providers performed complex therapies themselves, female clinicians referred more patients to specialists.

Alveolar process preservation at implants installed immediately into extraction sockets using deproteinized bovine bone mineral - an experimental study in dogs

AIM

To evaluate the soft tissue and the dimensional changes of the alveolar bony crest at sites where deproteinized bovine bone mineral (DBBM) particles, concomitantly with the placement of a collagen membrane, were used at implants installed into sockets immediately after tooth extraction.

MATERIAL AND METHODS

The pulp tissue of the mesial roots of (3) P(3) was removed in six Labrador dogs, and the root canals were filled. Flaps were elevated bilaterally, the premolars hemi-sectioned, and the distal roots removed. Recipient sites were prepared in the distal alveolus, and implants were placed. At the test sites, DBBM particles were placed in the residual marginal defects concomitantly with the placement of a collagen membrane. No treatment augmentation was performed at the control sites. A non-submerged healing was allowed. Impressions were obtained at baseline and at the time of sacrifice performed 4 months after surgery. The cast models obtained were analyzed using an optical system to evaluate dimensional variations. Block sections of the implant sites were obtained for histological processing and soft tissue assessments.

RESULTS

After 4 months of healing, no differences in soft tissue dimensions were found between the test and control sites based on the histological assessments. The location of the soft tissue at the buccal aspect was, however, more coronal at the test compared with the control sites (1.8 ± 0.8 and 0.9 ± 0.8 mm, respectively). At the three-dimensional evaluation, the margin of the soft tissues at the buccal aspect appeared to be located more apically and lingually. The vertical dislocation was 1 ± 0.6 and 2.7 ± 0.5 mm at the test and control sites, respectively. The area of the buccal shrinkage of the alveolar crest was significantly smaller at the test sites (5.9 ± 2.4 mm(2) ) compared with the control sites (11.5 ± 1.7 mm(2) ).

CONCLUSION

The use of DBBM particles concomitantly with the application of a collagen membrane used at implants placed into sockets immediately after tooth extraction contributed to the preservation of the alveolar process.

Influence of implants with different sizes and configurations installed immediately into extraction sockets on peri-implant hard and soft tissues: an experimental study in dogs

AIM

To study the influence on the healing of soft and hard peri-implant tissues when implants of different sizes and configurations were installed into sockets immediately after tooth extraction.

MATERIAL AND METHODS

Transmucosal cylindrical implants, 3.3 mm in diameter in the control sites, and conical 5 mm in diameter in the test sites, were installed into the distal socket of the fourth mandibular premolars in dogs immediately after tooth extraction. After 4 months, the hard and soft tissue healing was evaluated histologically.

RESULTS

All implants were integrated in mineralized mature bone. Both at the test and control sites, the alveolar crest underwent resorption. The buccal bony surface at the implant test sites (conical; 3.8 mm) was more resorbed compared with the control sites (cylindrical; 1.6 mm). The soft tissue dimensions were similar in both groups. However, in relation to the implant shoulder, the peri-implant mucosa was located more apically at the test compared with the control sites.

CONCLUSION

The present study confirmed that the distance between the implant surface and the outer contour of the buccal alveolar bony crest influenced the degree of resorption of the buccal bone plate. Consequently, in relation to the implant shoulder, the peri-implant mucosa will be established at a more apical level, if the distance between the implant surface and the outer contour of the alveolar crest is small.

Implant dentistry in undergraduate dental curricula in South-East Asia: forum workshop at the University of Hong Kong, Prince Philip Dental Hospital, 19-20 November 2010

This paper reports on the discussions arising from a 2-day forum on implant dentistry education in South-East Asia. The 10 institutions present represented undergraduate and postgraduate dental curricula from seven countries, including Hong Kong, Indonesia, Malaysia, Taiwan, Thailand, the Philippines, and Singapore. While not aiming to reach consensus as in other such conferences, the outcome was positive in establishing realistic goals in university education in implant dentistry for curriculum leaders and developers.

Flap vs. "flapless" surgical approach at immediate implants: a histomorphometric study in dogs

AIM

To compare the remodeling of the alveolar process at implants installed immediately into extraction sockets by applying a flap or a "flapless" surgical approach in a dog model.

MATERIAL AND METHODS

Implants were installed immediately into the distal alveoli of the second mandibular premolars of six Labrador dogs. In one side of the mandible, a full-thickness mucoperiosteal flap was elevated (control site), while contra-laterally, the mucosa was gently dislocated, but not elevated (test site) to disclose the alveolar crest. After 4 months of healing, the animals were sacrificed, ground sections were obtained and a histomorphometric analysis was performed.

RESULTS

After 4 months of healing, all implants were integrated (n=6). Both at the test and at the control sites, bone resorption occurred with similar outcomes. The buccal bony crest resorption was 1.7 and 1.5 mm at the control and the test sites, respectively.

CONCLUSIONS

"Flapless" implant placement into extraction sockets did not result in the prevention of alveolar bone resorption and did not affect the dimensional changes of the alveolar process following tooth extraction when compared with the usual placement of implants raising mucoperiosteal flaps.

Influence of lateral pressure to the implant bed on osseointegration: an experimental study in dogs

AIM

To study osseointegration and bone-level changes at implants installed using either a standard or a reduced diameter bur for implant bed preparation.

MATERIAL AND METHODS

In six Labrador dogs, the first and second premolars were extracted bilaterally. Subsequently, mesial roots of the first molars were endodontically treated and distal roots, including the corresponding part of the crown, were extracted. After 3 months of healing, flaps were elevated and recipient sites were prepared in all experimental sites. The control site was prepared using a standard procedure, while the test site was prepared using a drill with a 0.2 mm reduced diameter than the standard one used in the contra-lateral side. After 4 months of healing, the animals were euthanized and biopsies were obtained for histological processing and evaluation.

RESULTS

With the exception of one implant that was lost, all implants were integrated in mineralized bone. The alveolar crest underwent resorption at control as well as at test sites (buccal aspect ∼1 mm). The most coronal contact of bone-to-implant was located between 1.2 and 1.6 mm at the test and between 1.3 and 1.7 mm at the control sites. Bone-to-implant contact percentage was between 49% and 67%. No statistically significant differences were found for any of the outcome variables.

CONCLUSIONS

After 4 months of healing, lateral pressure to the implant bed as reflected by higher insertion torques (36 vs. 15 Ncm in the premolar and 19 vs. 7 Ncm in the molar regions) did not affect the bone-to-implant contact.