Movement of teeth adjacent to posterior bounded edentulous spaces

Crown adjustment and chairside efficiency of single-unit restorations fabricated from immediate and staged impressions using a digital workflow for posterior implants

PURPOSE

This is a clinical study to compare immediate and staged impression methods in a complete digital workflow for single-unit implants in the posterior area.

MATERIALS AND METHODS

Sixty patients requiring single-unit implant crowns were enrolled. Forty patients were assigned to the test group, immediate digital impression after implant surgery with crown delivery 4 months later. The remaining 20 patients were assigned to the control group, staged digital impressions 4 months after implant surgery, and crown delivery 1 month later. Both workflows involved free-model CAD-CAM crown fabrications. The crowns were scanned before and after clinical adjustment using an intraoral scanner (TRIOS Color; 3Shape). Two 3D digital models were trimmed and superimposed to evaluate the dimensional changes using Geomagic Control software. Chairside times for the entire workflow were recorded. Kruskal-Wallis was performed to compare crown adjustments between two groups, while One-way ANOVA was used to compare chairside time durations between the test and control groups.

RESULTS

All crowns were delivered without refabrication. The average maximum occlusion adjustment of crowns was -353.2 ± 207.1 μm in the test group and -212.7 ± 150.5 μm in the control group (p = 0.02). The average area of occlusal adjustment, measured as an area of deviation larger than 100 μm, was 14.8 ± 15.3 and 8.4 ± 8.1 mm2 in the test and control groups, respectively (p = 0.056). There were no significant differences in the mesial and distal contact adjustment amounts, or the maximum deviations of the proximal area, between the two groups. The mean chair-side time was 50.25 ± 13.48 and 51.20 ± 5.34 min in the test and control groups, respectively (p = 0.763).

CONCLUSIONS

The immediate impression method in the digital workflow for single-unit implants required more occlusal adjustments of crowns but showed similar chairside times compared to the staged impression method.

Adjacent tooth migration after maxillary first molar loss in patients with sinus augmentation: A retrospective research

PURPOSE

The objectives of this study are to: (1) investigate the extent of antagonistic and distal neighboring tooth migration in the maxillary posterior single tooth-missing site during the healing period of bone augmentation and implant surgery; (2) identify factors associated with tooth migration.

MATERIALS AND METHODS

One hundred and forty-three cases that lost the maxillary first molar were included, and their CBCT data during the edentulous period were obtained. Dentition models were reconstructed from CBCT, and superimpositions were performed, followed by measuring migration distances and calculating migration rates of antagonistic and distal neighboring teeth. Factors were analyzed using multivariate generalized estimating equations (GEE).

RESULTS

The mean migration distances were 208 ± 137 μm and 403 ± 605 μm for antagonistic teeth and distal teeth, and the mean migration rates were 26.8 ± 21.2 μm/month and 48.5 ± 76.7 μm/month, respectively. One hundred and nineteen out of 143 distal neighboring teeth migrated toward the edentulous site, and all antagonistic teeth migrated occlusally. Occlusal contact loss and chronic apical periodontitis both significantly accelerated antagonistic tooth migration (p < 0.05), the latter also accelerated distal tooth migration (p < 0.05). Besides, the displacement of the distal teeth was somewhat accelerated by the impacted adjacent third molar and root protrusion into the sinus.

CONCLUSIONS

The neighboring teeth tend to migrate toward the edentulous gap in the maxillary posterior region. Occlusal contact loss and chronic apical periodontitis are two significant risk factors for accelerating antagonistic tooth migration, and for distal teeth, chronic apical periodontitis is the risk factor. The impacted adjacent third molar and root protrusion into the sinus are also potential risk factors for accelerating the migration of the maxillary distal tooth. Thus, to prevent maxillary edentulous gap reduction, the factors mentioned above should be taken into consideration when planning treatment flow.

Uprighting a mesially tilted molar using customized titanium healing abutment of an adjacent osseointegrated implant

This case report evaluates the use of a customized healing abutment of a dental implant to upright a mesially tilted molar using elastic separating rings. The external surface of the healing abutment was roughened by air particle abrasion, and a flowable composite was applied as a collar around it. The size of the resin collar was increased several times during the molar uprighting treatment by replacing the elastic ring. The uprighting procedure was evaluated after 2 months using radiographic and clinical evaluations. After treatment, the mesiodistal space above the implant was increased from 6 mm to 9 mm as follows: 2 mm by uprighting the second molar and 1 mm by mesial shifting the second premolar, and then a screw-retained zirconia crown was placed to restore the implant. The healing abutment of the implant can be modified by adding a resin collar and used as orthodontic anchorage for uprighting the adjacent tilted molar to facilitate the prosthetic procedure. Neither special instruments nor an orthodontic background are required for this minor tooth movement.

Three-dimensional position changes of unopposed molars before implant rehabilitation: a short-term retrospective cohort analysis

OBJECTIVE

To investigate the spatial changes of unopposed molars within the period between the antagonist extraction and the final implant restoration using data from cone beam computed tomography.

METHODS

A total of 59 patients with 68 unopposed molars were included in this study. Three-dimensional models reconstructed from cone beam computed tomography data before and after loss of the antagonist were superimposed to measure the spatial changes. The overeruption and tipping of target teeth were calculated by coordinate values.

RESULTS

The result of overeruption over the study period (9.2 ± 4.3 months) was expressed by two values: the mean overeruption of molar cups (0.432 mm) and the maximum overeruption of cusps (0.753 mm), which were statistically significant compared to the baseline level (p < 0.001). The average tipping was 1.717 degrees in the buccal direction.

CONCLUSIONS

Unopposed molars displayed overeruption throughout the study period (9.2 ± 4.3 months), which indicates that the clinicians should pay attention to the possibilities of overeruption and make appropriate interventions in their clinical practice. The establishment of three-dimensional measuring methods using cone beam computed tomography data helps analyze spatial changes.

[Three-dimensional movement of posterior teeth after losing the interproximal and occlusal contacts in adults]

OBJECTIVE

To observe the movement of posterior teeth after losing the interproximal and occlusal contacts in adults from the amount and speed of mesial-distal, buccal-lingual, occlusal-gingival and three-dimensional movements.

METHODS

Twenty cases of metal post-core restoration from the Department of Prosthodontics, Peking University School and Hospital of Stomatology were recruited into this study, which was an observational study. The restored teeth had complete mesial, distal, and occlusal contacts before treatment. All the interproximal and occlusal contacts were removed during the preparation for the post-core. The three-dimensional positions of the post-core preparation were obtained by the intraoral scanner at the day of tooth preparation and that of post-core placement. The amounts of mesial-distal, buccal-lingual and occlusal-gingival tooth movement were measured in the software. On this basis, the amount of three-dimensional tooth movement was calculated. The speed of tooth movement was calculated based on the elapsed time between the two scans.

RESULTS

Ten females and ten males with an average age of (29.5±4.9) years were recruited. The average elapsed time was (10.9±2.7) days. The amount of the mesial-distal tooth movement was (134.8±61.2) μm, of the buccal-lingual tooth movement was (110.3±39.5) μm, of the occlusal-gingival tooth movement was (104.8±57.5) μm, and of the three-dimensional tooth movement was (211.4±71.0) μm, respectively. The amounts of mesial-distal, buccal-lingual and three-dimensional tooth movements were larger in female than in male (P < 0.05). The speed of the mesial-distal tooth movement was (13.1±7.8) μm/d, of the buccal-lingual tooth movement was (10.6±4.5) μm/d, of the occlusal-gingival tooth movement was (10.1±6.8) μm/d, and of the three-dimensional tooth movement was (20.5±9.7) μm/d, respectively. The speed of mesial-distal and buccal-lingual tooth movements were larger in female than in male (P < 0.05). The speed of three-dimensional tooth movement was slightly larger in female than in male, while there was no significant difference between different genders (P>0.05).

CONCLUSION

The three-dimensional position of posterior teeth changed after losing the interproximal and occlusal contacts in adults. The female had more significant and faster tooth movement than the male.

The accuracy of implant placement with computer-guided surgery in partially edentulous patients and possible influencing factors: A systematic review and meta-analysis

PURPOSE

To review the current clinical studies regarding the accuracy of implant computer-guided surgery in partially edentulous patients and investigate potential influencing factors.

STUDY SELECTION

Electronic searches on the PubMed and Cochrane Central Register of Controlled Trials databases, and subsequent manual searches were performed. Two reviewers selected the studies following our inclusion and exclusion criteria. Qualitative review and meta-analysis of the implant placement accuracy were performed to analyze potential influencing factors. Angular deviation, coronal deviation, apical deviation, and depth deviation were evaluated as the accuracy outcomes.

RESULTS

Eighteen studies were included in this systematic review, including six randomized controlled trials, nine prospective studies, and three retrospective clinical studies. A total of 1317 implants placed in 642 partially edentulous patients were reviewed. Eight studies were evaluated using meta-analysis. Fully guided surgery showed statistically higher accuracy in angular (P <0.001), coronal (P <0.001), and apical deviation (P <0.05) compared with pilot-drill guided surgery. A statistically significant difference (P <0.001) was also observed in coronal deviation between the bounded edentulous (BES) and distal extension spaces (DES). A significantly lower angular deviation (P <0.001) was found in implants placed using computer-aided design/computer-aided manufacturing (CAD/CAM) compared to the conventional surgical guides.

CONCLUSIONS

The edentulous space type, surgical guide manufacturing procedure, and guided surgery protocol can influence the accuracy of computer-guided surgery in partially edentulous patients. Higher accuracy was found when the implants were placed in BES, with CAD/CAM manufactured surgical guides, using a fully guided surgery protocol.

The migration of neighboring and antagonist teeth three months after implant placement in healed single tooth-missing sites

OBJECTIVES

To quantify the neighboring and antagonist teeth migration of a single posterior tooth-missing site within 3 months using digital scanning and measuring techniques.

MATERIALS AND METHODS

Intraoral scans (IOS) were made in 40 patients presenting a single posterior tooth-missing gap and receiving implant therapy. IOS were obtained at the day of and three months after implant surgery rendering a digital baseline model (BM) and a digital follow-up model (FM). Digital models were superimposed using the implant scan body as reference. Antagonist models were processed by the best fit alignment. Dimensional change between anatomical landmarks on neighboring teeth and that of featuring points on antagonistic teeth were measured using a three-dimensional analysis software. The Mann-Whitney U test was applied to compare the tooth-moving distance between the mesial and distal neighboring teeth. The Kruskal-Wallis one-way ANOVA was used to test the difference in dimensional change in tooth-missing site among age subgroups.

RESULTS

The mean dimensional change in the tooth-missing site was -37.62 ± 106.36 μm (median: -28.33 μm, Q₂₅ -72.65/Q₇₅ 38.97) mesial-distally and -67.91 ± 42.37 μm (median: -61.50 μm, Q₂₅ -88.25/Q₇₅ -36.75) occlusal-gingivally. Eighteen out of 40 mesial neighboring teeth and 24 out of 40 distal neighboring teeth showed migration towards the implants. When patients were grouped according to age, the mesial-distal reduction in the tooth-missing site was significantly larger in patients younger than 30 years compared with those older than 50 years (p < .05).

CONCLUSIONS

The dimensions of posterior tooth-missing sites decreased over an observation period of 3 months.

The influence of undercut depths on the accuracy of casts poured from irreversible hydrocolloid impression materials

Objectives

To evaluate the elastic recovery of a typical irreversible hydrocolloid impression material in terms of the amount of undercut identified and additional thickness of spacer provided before custom tray fabrication.

Methods

This study surveyed the undercut depths of the teeth surfaces and lingual sulci of one hundred partially dentate mandibular dental casts which were subsequently scanned and the data exported as STL files. A typical cast from each undercut category (0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 4mm, 5mm) was 3D printed. Three custom trays were constructed with spacer thicknesses representing 20%, 30% and 50% compression against the wall of the custom trays on removal, impressions recorded, and casts fabricated in dental stone. Measurements for elastic recovery of irreversible hydrocolloid were done using an internal caliper and a digital caliper. All measurements were done by the principal investigator. Non-parametric analyses were used for comparisons of the undercut values between the 3D printed and poured casts to determine the amount of elastic recovery of the irreversible hydrocolloid impression material.

Results

There was no statistically significant difference in measurements between the original 3D printed casts and the poured casts, irrespective of percentage compression (p > 0.05).

Conclusions

In removable partial denture construction, casts should be blocked out parallel to the path of insertion and then an additional 3mm of spacer applied as a standard technique before custom tray fabrication to ensure elastic recovery of the irreversible hydrocolloid impression.

Clinical implications

In severe undercut situations, accurate impressions can be taken using irreversible hydrocolloid by blocking out all undercut surfaces on the teeth and lingual sulci before adapting additional three-millimetre wax spacer on casts when constructing custom trays thereby ensuring accurate and reliable impressions for removable prosthesis construction.

Three-dimensional analysis of the physiologic drift of adjacent teeth following maxillary first premolar extractions

We assessed the three-dimensional (3D) pattern of the physiologic drift of the remaining adjacent teeth after premolar extraction due to orthodontic reasons and the associated factors. Data were collected from 45 patients aged 17.04 ± 5.14 years who were scheduled to receive a fixed appliance after maxillary premolar extraction. Seventy-five drift models were obtained and digitalized via 3D scanning. The average physiologic drift duration was 81.66 ± 70.03 days. Angular and linear changes in the first molars, second premolars, and canines were measured using the 3D method. All the examined teeth had tipped and moved towards the extraction space, leading to space decreases. Posterior teeth primarily exhibited significant mesial tipping and displacement, without rotation or vertical changes. All canine variables changed, including distal inward rotation and extrusion. The physiologic drift tended to slow over time. Age had a limited negative effect on the mesial drift of posterior teeth, whereas crowding had a limited positive effect on canine drift. Thus, the mesial drift of molars after premolar extraction may lead to molar anchorage loss, particularly among younger patients. The pattern of the physiologic drift of maxillary canines can help relieve crowding and facilitate labially ectopic canine alignment, whereas canine drift is accelerated by more severe crowding.

Professional Variability in Decision Making in Modern Dentistry: A Pilot Study

Dental treatment planning is usually expected to take account of the individual patient's clinical risks and benefits. Ideally, the therapeutic choice for each and every patient should be based on adequate clinical diagnostics and risk assessment that facilitates stabilization of the patient's clinical condition as well as prevents further oral impairment. However, identification of the most suitable approach tends to become more and more challenging as the number of therapeutic alternatives continues to increase due to medical innovation. In this study, the challenge of decision making in modern dentistry is illustrated using the example of bounded edentulous spaces. Many therapeutic alternatives exist for such clinical scenarios, including a noninvasive monitoring approach, minimally invasive tooth recontouring, orthodontic and prosthodontic treatment, and implant placement. The findings of this pilot study highlight the utmost relevance of incorporating individual patients' needs and risks into clinical treatment planning and providing appropriate guidelines.

Oral diagnosis and treatment planning: part 7. Treatment planning for missing teeth

Although more people are retaining increasing numbers of their natural teeth into older ages, approximately 30-40% of persons over the age of 75 years in Western countries are edentulous. The causes and significance of tooth loss vary widely among individuals and cultures, and missing teeth may be replaced by a variety of means for functional, social and psychological reasons, rather than for significant physical health benefits. Therefore, it is essential to determine what the loss of teeth means to patients and what their expectations are for the outcomes following tooth replacement by various methods.

A sociodental approach in prosthodontic treatment decision making

A critical problem in the decision making process for dental prosthodontic treatment is the lack of reliable clinical parameters. This review discusses the limits of traditional normative treatment and presents guidelines for clinical decision making. There is a need to incorporate a sociodental approach to help determine patient's needs. Adoption of the evidence-based clinical practice model is also needed to assure safe and effective clinical practice in prosthetic dentistry.

Occlusal Changes Following Posterior Tooth Loss in Adults. Part 2. Clinical Parameters Associated with Movement of Teeth Adjacent to the Site of Posterior Tooth Loss

PURPOSE

Much anecdotal evidence is available on tooth positional changes following loss of an adjacent tooth, but only a few studies are available. In Part 1 of this series, supraeruption was assessed and Generalized Linear Models were made to determine the clinical parameters associated with the supraeruptive process. The models demonstrated that clinical parameters were not only associated with the extent of supraeruption, but also with the type of eruption present. This investigation of tooth positional changes adjacent to sites of posterior tooth loss attempts to provide increased understanding of the magnitude, direction, and associated features that may be helpful in decision making and treatment planning in the clinical setting.

MATERIALS AND METHODS

One hundred patients with an unopposed posterior tooth, with 100 age, sex, and bone level matched controls, were drawn from patients undergoing routine restorative care at Leeds Dental Institute. Study models were scanned, and the extent of eruption, type of eruption of the unopposed tooth, the overbite, overjet, buccal occlusion, and degree of crowding in the dentition, tipping, rotation, and buccal movement of the teeth associated with the edentulous site were recorded. Generalized Linear Models were developed to examine associations between each tooth movement and patient or dental factors.

RESULTS

A statistical significance in the degree of tipping of teeth both mesial and distal to the extraction site was detected between the subject and control groups. There was also a significant difference in rotation of the tooth mesial to the site. Four Generalized Linear Models were produced of the types of non-vertical movements found in teeth associated with sites of tooth loss.

CONCLUSIONS

Teeth adjacent to the site of tooth loss may undergo non-vertical movements. Teeth mesial to the extraction site had a tendency to tip distally. The degree of tipping was increased in upper teeth and in subjects with a cusp-to-cusp buccal occlusion. Rotation of teeth mesial to the extraction site was more prevalent in the lower arch. Tipping of the tooth distal to the extraction site could be extreme and was found to be more prevalent in subjects with a reduced (Code 1) overbite and in the lower arch. Rotation of teeth distal to the extraction site was greater in the upper arch and was also associated with a reduced (Code 1) overbite. It also had an association with rotation of the tooth mesial to the extraction site. Models of non-vertical movement are likely to be of limited value due to overdispersion, indicating a high degree of variability within the model.

Occlusal changes following posterior tooth loss in adults. Part 3. A study of clinical parameters associated with the presence of occlusal interferences following posterior tooth loss

PURPOSE

Tooth positional changes following posterior tooth loss may alter arch forms and occlusal planes. This may result in the development of occlusal interferences. The purpose of this study was to determine clinical parameters associated with the presence of retruded contact position (RCP) contacts and occlusal interferences associated with posterior tooth loss.

MATERIALS AND METHODS

Diagnostic casts of 100 patients with at least one unopposed posterior tooth and 100 control patients were scanned and analyzed to record clinical parameters described in the earlier publications in this series. Clinical examinations identified the presence of RCP contacts and occlusal interferences. Five generalized linear models were developed to investigate the parameters associated with presence of RCP contacts, protrusive interferences, working side interferences, and nonworking side interferences.

RESULTS

RCP contacts were associated with the degree of supraeruption of the unopposed tooth and the presence of other types of interferences. Protrusive interferences were associated with the presence and position of a tooth distal to the extraction site and the presence of other types of interference. Working side interferences were associated with tipping of the tooth mesial to the extraction site and the presence of other interferences. Nonworking side interferences were associated with the presence of other types of interference only.

CONCLUSION

Unopposed posterior teeth are more likely to be involved in RCP contacts or interferences than their matched controls. Many teeth were involved in multiple interferences, and there appears to be a number of interrelationships between these. Initial RCP contacts have associations with the extent of supraeruption of the unopposed teeth. The presence and position of the teeth distal to extraction sites was significant when modeling protrusive interferences. Protrusive interferences are more prevalent where the site of tooth loss was bounded. Mesial tipping of the teeth distal to extraction sites reduced this effect. Working side interferences were associated with tipping of teeth mesial to the site of tooth loss. No associations between patient or tooth factors were found for nonworking side interferences, and the only association found for these interferences were with protrusive interferences at the sites.

Deviation from the Broadrick occlusal curve following posterior tooth loss

Production of an appropriate occlusal curve for dentitions which have become deranged because of tooth loss, overeruption, tipping and drifting can present challenges for the dental technician. An earlier paper (J Oral Rehabil, 2005 32: 895-900.) demonstrates that the use of the Broadrick flag method for producing the occlusal curve is relatively accurate for most intact arches. This study demonstrates that when a posterior tooth has remained unopposed for 5 years or more positional changes, which cause deviation from the Broadrick curve, occur. The extent of the deviation may be extreme, potentially leading to difficulties in restoring a harmonious occlusal scheme. This study also demonstrates that the Broadrick curve may provide an accurate reproduction of the occlusal curve, even when the tooth forming the posterior determinant of the curve is tipped. A moderate degree of tipping of this tooth has little effect on the radius of the Broadrick curve.